1) A bus disconnect link is used to isolate
the generator circuit breaker from the bus
2) A capacitor can be tested using a megohmmeter or an ohmmeter If the meter is connected to a shorted capacitor, the meter pointer should
immediately deflect to and remain at zero
3) A circuit with a blown fuse would be described as a/an
- open circuit
4) A common type of protective covering used on electrical conductors is
fibrous braid
5) A device which can be used to check the calibration of a circuit breaker is a
portable low voltage high current testing unit
6) A device which prints out a permanent record of the plant operating conditions is known as the
data logger
7) A dielectric is a/an
electrical insulator
8) A fuse will blow if
the electrical current exceeds the rated value of the fuse
9) A galvanometer is an instrument used to measure
very small amounts of current or voltage
10) ground can be defined as an electrical connection between the wiring of a motor and its
metal framework
11) A grounded switch or cable will be indicated by a megohmmeter reading of
zero
12) A megohmmeter can be used to test for
an open field coil
13) A megohmmeter is connected to each end of an individual motor winding A low ohm reading indicates
good continuity
14) A megohmmeter is used to measure
insulation resistance values
15) A multimeter may be damaged by taking a
voltage reading while in the ammeter mode
16) A replacement wire having twice the length and one-half the cross-sectional area of the original wire will have a resistance that is
four times that of the original wire
17) A resistance in a circuit of unknown value is to be tested using the voltmeter/ammeter method Therefore, the meters should be connected with
the ammeter in series and the voltmeter in parallel with the resistance
18) A resistor placed in parallel to the output of a power supply
aids in output voltage regulation
19) A switchboard ammeter indicates a reading slightly above zero when the leads are disconnected, this is caused by
mechanical misalignment of the meter pointer
20) A switchboard for an AC electrical system requires the use of which of the following devices?
Frequency meter.
21) A switchboard, for a AC electrical distribution system, will be provided with which of the following components?
All of the above
22) A wattmeter is used to determine
the power being consumed by electrical equipment
23) AC circuits develop resistance, inductance, and capacitance The inductive reactance of a circuit is expressed in
Ohms
24) AC voltmeters are generally calibrated to read the
RMS voltage
25) Accidental grounds in a shipboard electrical system must be repaired as soon as possible as they will
damage insulation and may cause outages
26) All electric cables passing through watertight bulkheads must be
installed with watertight stuffing tubes
27) An AC circuit has capacitance arranged in series If the line voltage remains constant, the capacitive reactance value can be varied by changing the
line frequency
28) An accidental path of low resistance, allowing passage of abnormal amount of current is known as a/an
short circuit
29) An across-the-line starter is typically used for which of the following applications?
Full-voltage starting of motors
30) An ammeter should be used to measure
current flow in a circuit
31) An electrical component is connected across a 120 volt 60 hertz AC supply What is the current drawn by the component if the impedance is 200 ohms?
0.60 amperes
32) An insulation resistance test is performed on a particular piece of electric equipment In addition to the resistance reading, what information listed below should be entered in the electrical log?
The temperature of the machine at the time the resistance reading was taken.
33) An ohmmeter can be used to measure
circuit continuity
34) Any electric motor can be constructed to be
explosion proof
35) As shown in the illustration EL-0026, the symbol is used in electrical drawings to designate a
sustaining type push button with a mechanical interlock
36) As shown in the illustration EL-0079, the direction of electron flow through the component is
from terminal A to terminal B
37) As shown in the illustration, which of the symbols represents a normally closed electrical contact?
A
38) Before measuring an unknown resistance with an ohmmeter, you should
short the test leads and calibrate the meter
39) Before testing insulation with a megohmmeter, the windings of large machines should be grounded for about 15 minutes just prior to the test, because the
static charge of the machine may give a false reading
40) Burning of controller contacts, when opening, is prevented by
magnetic blowout coils
41) Capacitance in an AC circuit will
- oppose any change in circuit voltage
42) Capacitors are used on the output of the power supply in todays consoles to
filter out ripple
43) Capacitors can be used in electric distribution systems to improve power factor This is accomplished by seesawing energy between the capacitor and the
inductive loads
44) Cleaning of electrical insulation should be
determined by need and not the calendar
45) Component F in the illustrated EL-0033 device is for
- overload protection
46) Copper is often used as an electrical conductor because it
is able to pass current with little opposition
47) Decreasing the frequency in a capacitive circuit while maintaining a constant circuit voltage, will result in a/an
decrease in circuit current
48) During maintenance of circuit breakers,
inspect for wear and misalignment of main contacts
49) Electric cables are formed of stranded wire to
increase their flexibility
50) Electrical insulation is classed by the
temperature stability of the manufacturing material(s)
51) Electrical power is expressed in
Watts
52) External shunts are sometimes used with ammeters to
prevent damage to the meter movement from heat generated by the shunt
53) Figure B shown in the illustration EL-0067 represents a/an
silicon controlled rectifier
54) Four lamps are connected in parallel in a single circuit If one of the lamp burns out, the others will
burn with their original intensities
55) Fuses are rated in
all the above
56) Fuses are usually rated in
amps and volts
57) Grease coatings on electrical contact surfaces increase contact resistance and should be removed with a/an
clean dry cloth
58) Grounds occurring in electrical machinery as a result of insulation failure may result from
all of the above
59) Handheld phase sequence indicators are useful when
connecting shore power lines to the ship
60) Hand-portable phase sequence indicators should be used when
preparing to make the shore power connection
61) How is a wattmeter electrically connected in a circuit?
In series-parallel
62) How much current will flow in the illustrated circuit EL0020 if the supply is 24 volts and the resistances of R1 is 3 ohms, R2 is 4 ohms, and R3 is 5 ohms?
2 amps
63) If a voltage tester is being used to check for defective fuses in the circuit, shown in the illustration EL-0062, which of the readings will indicate that fuse #2 is open?
A-D no voltage
64) If coil R1-R2 at the receiver of figure A shown in the illustration were in 180 degree error with respect to that of the transmitter, what corrective action should be taken?
Reverse the 60 Hz supply connections at R1 and R2.
65) If fuse #1 shown in the illustration EL-0062 is defective, a voltage tester connected across points C and B will
show a reading of zero volts
66) If fuse F-1 in the illustrated schematic diagram opens,
the motor will not start
67) If many turns of an alternating current coil for a contactor become short circuited, the coil
will probably burn out immediately
68) If the length of a wire is halved and the cross-sectional area is doubled, the resistance will be
Quartered
69) In a simple series circuit, the entire source voltage will drop across
an open circuit
70) In a three-phase circuit, the phase voltages are
120° apart
71) In order to increase its range of measurement, a resistance would be placed in series with which of the following instruments?
DC voltmeter
72) In the flow of one cycle of single phase AC current past any given point in a circuit, the maximum current peak occurs
two times
73) In the illustration EL-0033 the component C is the
fixed contact
74) Large cable sizes are formed as individual conductors that may be comprised of several smaller strands to
- obtain the flexibility required for easy handling
75) Magnet chatter or pumping occurring in a magnetic contactor can be caused by
chattering contacts on the control relay
76) Most conducting materials such as copper, aluminum, iron, nickel, and tungsten
increase in resistance with increased temperature
77) Periodic testing of circuit breakers is necessary to assure that a correctly rated and properly installed unit
will continue to provide the original degree of protection
78) Possible phase relationships between voltage and current in an alternating current circuit include which of the following conditions?
All of the above.
79) Reversing the current flow through a coil will
reverse its two-pole field
80) The 24 volt DC bus on the emergency switchboard is used to supply power to the
all of the above
81) The arrow drawn through the resistor shown in the illustration EL-0086 indicates that it is
- one whose resistance is variable
82) The combined effect of inductive reactance, capacitive reactance, and resistance in an AC series circuit is known as
Impedance
83) The diagram shown in the illustartion EL-0022 represents a/an
common emitter amplifier
84) The diagram shown in the illustration EL-0082 represents a/an
stepup transformer
85) The dielectric constant is a numerical value indicating the effectiveness of a dielectric material in comparison to that of a standard, which is
dry air or a vacuum
86) The electrical device shown in the illustration EL-0077 is a/an
potentiometer
87) The electrical diagram shown in the illustration EL-0021 shows
R1, R2, and R3 are connected in parallel
88) The electrical diagram shown in the illustration is used to depict a/an
capacitive circuit
89) The electrical schematic illustrated EL-0059 in figure A, depicts a/an
potential transformer
90) The existing resistance of a conductor is dependent upon its length, cross-sectional area,
material and temperature
91) The final step in testing a circuit for a ground involves the use of a megohmmeter A grounded switch or cable will be indicated by a megohmmeter reading of
zero
92) The illustrated device is a
full wave bridge rectifier
93) The illustrated EL-0024 circuit is a
wheatstone bridge
94) The insulation resistance of electric equipment and machinery should be tested for the lowest normal insulation values
immediately after shutting down the machine
95) The multiple prefix giga (G) means
billion (10 to the 9th power)
96) The multiple prefix kilo means
thousand (10 to the 3rd power)
97) The multiple prefix mega (M) means
million (10 to the 6th power)
98) The multiple prefix tera (T) means
trillion (10 to the 12th power)
99) The need for insulation cleaning may be determined by
visual inspection for dirt accumulation
100) The output voltage of a 440 volt, 60 hertz, AC generator is controlled by the
exciter output voltage
101) The part of the shipboard electrical system used to control the distribution of power to the branch circuits, is the
main switchboard
102) The purpose of a main switchboard circuit breakers reverse-power trip is to
prevent alternator motorization
103) The purpose of a short circuit forcing module (short time trip) installed in a branch line is to provide
all of the above
104) The purpose of the automatic bus transfer shown in the illustration is to
provide emergency power to the lighting distribution panel
105) The resistance of a conductor varies
directly as its length and inversely as its cross-sectional area
106) The resistance of electric wire will decrease as its
cross-sectional area increases
107) The resistance of most conducting materials will change as a result of temperature change The resistance of copper will
decrease as temperature decreases
108) The sub-multiple prefix micro (Greek letter mu) means
millionth (10 to the -6th power)
109) The sub-multiple prefix milli (m) means
- one thousandth (10 to the -3rd power)
110) The sub-multiple prefix nano (n) means
billionth (10 to the -9th power)
111) The sub-multiple prefix pico (p) means
trillionth (10 to the -12th power)
112) The symbol shown as figure A in EL-0059 represents a/an
transformer
113) The total power consumed in a parallel circuit is
the sum of the powers used in each individual load
114) The total power used up in a series circuit is
the sum of the powers used in each load
115) The total resistance of a parallel circuit is always
smaller than that of the branch with the lowest resistance
116) The total voltage of a series circuit is the
sum of the individual voltage drops
117) The unit hertz is equivalent to
cycles per second
118) The unit of electrical power is the
Watt
119) The unit of electrical resistance is the
Ohm
120) To carry out an insulation resistance test, one terminal of the megohmmeter should be connected to the winding, with the other terminal being connected to the
frame of the machine
121) To check the three line fuses of a three-phase system consisting of a three-phase motor, you must
place the starter in the stop position
122) To determine if a stator coil is grounded, you should use a/an
Megger
123) To minimize magnetic field interaction between electrical conductors in physical proximity, it is best to keep them
at right angles and as far as practicable from each other
124) To test fuses in an energized circuit, you should use a
Voltmeter
125) What is represented by the electric symbol figure D in the illustration?
Fuse
126) What is the direction of current through the load resistor in the circuit shown in the illustration?
Always from the grounded end to point Z.
127) What is the power consumed by R2 in the circuit illustrated EL-0020 if the supply is 24 volts and the resistance of R1 is 3 ohms, R2 is 4 ohms, and R3 is 5 ohms?
16 watts
128) What is the power consumed by R3 in the circuit illustrated EL-0020 if the supply is 24 volts and resistance of R1 is 3 ohms, R2 is 4 ohms, and R3 is 5 ohms?
20 watts
129) What is the voltage across R1 of the illustrated circuit EL0020 if the supply is 24 volts and resistance of R1 is 3 ohms, R2 is 4 ohms, and R3 is 5 ohms?
6 volts
130) When a megohmmeter is being used to test insulation resistance, current leakage along the surface of the insulation is indicated by the megohmmeters pointer
kicking slightly down scale as voltage is applied
131) When a megohmmeter is used to test insulation, the gradual rise of the pointer reading as a result of continued cranking, is caused by
the dielectric-absorption effect of the insulation
132) When a megohmmeter is used to test the dielectric strength of wire insulation, the initial dip of the pointer toward zero is caused by
the capacitance of the circuit
133) When a solid-state component of an electronic circuit is mounted to a metallic mass, the general purpose of that mass is to
act as a heat sink
134) When changing fuses, you should always
use a fuse puller
135) When electrical cables penetrate watertight bulkheads,
a watertight stuffing tube capable of accepting packing should be employed
136) When insulation failure produces a low resistance current path between two conductors, the resulting condition is known as
a short circuit
137) When maintenance personnel are working on electrical equipment, all supply switches should be secured in the open position and tagged specifically by the
person performing the repair
138) When measuring AC current flow, you must always connect the meter
in series with the power source and load
139) When placed in a magnetic field, which of the materials listed will maintain the highest permeability?
Soft iron
140) When replacing fuses, always make sure
the fuse clips are straight, tight, and in good contact
141) When shipboard electrical distribution circuits are connected in parallel, additional parallel circuits will cause the total circuit resistance to
decrease, causing an increase in the line current
142) When the current flow through a copper wire increases, its
temperature will increase
143) When using a megohmmeter to test insulation, good insulation will be indicated by
a downward dip followed by a gradual climb to the true resistance value
144) Where a thermal-acting breaker is required to be used in an area of unusually high, low, or constantly fluctuating temperatures, an ambient compensating element must be used This element consists of a
second bimetal element
145) Which component will stop the motor shown in the illustration in case of an overload in the control circuit?
G
146) Which of the following characteristics is most critical in determining the size of the cable to be used in a particular circuit?
current rating
147) Which of the following conditions can lead to the failure of a resistor?
All of the above
148) Which of the following electric motors would be the safest and most reliable to use on the main deck of a vessel in foul weather conditions?
Watertight motors
149) Which of the following materials is a good electrical insulator?
Wood
150) Which of the following precautions should be taken when a blown fuse, rated at 10 amperes, is replaced?
Replace blown fuse with one of equal voltage and ampere capacity.
151) Which of the following represents a characteristic of an ungrounded electrical distribution system?
Accidental contact between one line and ground does not cause an outage.
152) Which of the following statements concerning electrical cables is correct?
Where they pass through watertight bulkheads, they should be fitted with watertight stuffing boxes.
153) Which of the following statements is correct for the illustrated EL-0020 circuit?
R1, R2, and R3 are connected in series.
154) Which of the following statements is true concerning the cleaning of electrical contacts?
Delicate parts should be cleaned with a brush and an approved safety solvent.
155) Which of the following statements is true if a 100 watt lamp and a 75 watt lamp are connected in parallel across a 100 volt power supply?
The 75 watt lamp will have a higher resistance.
156) Which of the following statements regarding the use of a current measuring instrument is correct?
It must be connected in series with the circuit.
157) Which of the following statements represents the action of a megohmmeter when testing a small capacitor in good condition?
The meter pointer should first swing quickly to zero and then gradually move up the scale as the capacitor charges.
158) Which of the following statements represents the FIRST precaution to be taken prior to working on any installed electrical component?
Open the supply circuits and tag the switches.
159) Which of the instruments listed is used to check insulation resistance?
Megohmmeter
160) Which of the instruments listed should always be connected in series with a circuit?
Ammeter
161) Which of the listed figures shown in the illustration EL0084 represents devices connected in a three-phase delta-delta arrangement?
A
162) Which of the listed sections of an emergency switchboard is used to supply power for alarm signals under emergency conditions?
The 24 volt DC bus
163) Which of the meters listed should only be used after a circuit has been electrically disconnected?
Ohmmeter
164) Which of the spaces listed is defined as a location requiring an exceptional degree of protection when considering the installation of shipboard electrical equipment?
Machinery space
165) Which of the substances listed can be used to shield sensitive equipment from static magnetic fields?
Permeable iron
166) With both ends of a three conductor cable disconnected and arranged without the conductors touching each other, an ohmmeter reading of zero ohms between the ends of one conductor would indicate
Continuity
167) A battery is connected to a circuit containing three resistors in parallel The values of the three resistors are 2 ohms, 3 ohms, and 6 ohms What is the voltage of the battery if the total circuit current is 12 amps?
12 volts
168) A breakable, mercury-filled thermometer should not be used in a lead-acid battery to measure electrolyte temperature, as an accidental breakage can cause
severe sparking and explosions
169) A constant output voltage from an AC generator is maintained by the
voltage regulator
170) A DC ammeter is always connected
in series with a circuit
171) A diesel driven emergency generator is prevented from being paralleled with the ships service generators by
an electrical interlock system
172) A generator has been exposed to water and is being checked for its safe operation Therefore, it is necessary to
test insulation values with a megger
173) A generator is prevented from becoming motorized by the use of a/an
reverse power relay
174) A hydrometer indicates specific gravity by comparing the
buoyancy of an object in water with the buoyancy of the same object in the liquid being measured
175) A lead-acid battery cell sustaining a short circuit
will become excessively heated while being charged
176) A lead-acid battery is considered fully charged when the
specific gravity of all cells reaches the correct value and no longer increases over a period of 1 to 4 hours
177) lead-acid battery may become hotter than normal during a charge if the
battery has a shorted cell
178) A loss of field excitation to an AC generator while operating in parallel will cause it to
lose its load, begin to motorize, trip out on reverse power relay, and possibly overspeed
179) A nickel-cadmium battery is receiving a normal charge and gases freely The charging current should
remain the same
180) A positive charge can:
both of the above
181) A reverse-current relay will prevent AC generator motorization by
tripping the generator circuit breaker
182) A slow continual loss of electrolyte level from one cell of a storage battery could be due to
a cracked casing
183) A three-phase alternator is operating at 450 volts with the switchboard ammeter indicating 300 amps The kw meter currently indicates 1636 KW, with a power factor of 07 If the power factor increases to 08, the KW meter would then read
186.8 KW
184) A three-phase alternator operates at 450 volts with a 08 power factor If the ammeter indicates 250 amperes, what should be the KW meter reading?
155.70 KW
185) A transformer in an electric circuit serves to
increase or decrease circuit voltage as required
186) A twelve volt lead-acid battery is constructed of
six cells
187) A vessel is equipped with two ships service generators Generator #1 is rated at 900 kw and generator #2 is rated at 600 kw During parallel operation, with a hotel load of 1,000 kw, what should be the kw load on generator #2?
400 kw
188) After closing the circuit breaker to place two similar alternators in parallel, the NEXT step is to balance the
kilowatt load
189) Air gap readings for electrical generating equipment should be taken periodicly This is to I determine the condition of the bearings II prevent damage to the rotor and stator
both I and II
190) Air gap readings should be periodicly taken for electrical generation equipment The best tool to use to take these measurements is a
tapered, long blade, feeler gage
191) Air gap readings should be taken on electrical generation equipment periodicly to I check machine effeciency II determine the need for cleaning
neither I or II
192) Air gap readings should be taken on electrical generation machinery periodicly to I determine the need for cleaning II check the condition of the bearings
II only
193) Air gap readings should be taken periodicly on electrical generation equipment to
determine the condition of the bearings
194) An AC generator panel is fitted with both synchronizing lamps and a synchroscope When the synchroscope pointer reaches the noon position, one synchronizing light is bright and the other is dark This means
the phase sequence is incorrect
195) An AC generator produces 60 Hz at 1800 RPM If the generator speed is increased to 1830 RPM, the cycles will
increase to 61 Hz
196) An alternator switchboard has a synchroscope and synchronizing lamps If the synchroscope is broken, which of the steps listed is the most essential before an alternator can be paralleled with the bus?
The frequency meter should be used to determine that the incoming alternator frequency is slightly higher than the bus.
197) As a result of a mechanical malfunction in one of the ships service generators operating in parallel, you must secure that generator In order to prevent a possible overload to the remaining generator, which of the following sequential courses of action
Trip all nonvital distribution feeder circuit breakers, the malfunctioning generators circuit breaker, and the prime mover throttle trip.
198) As shown in the illustration EL-0071, the dry-cell batteries are connected in
series
199) As shown in the illustration, all MS contacts are opened and closed by means of
manual operation of the master switches
200) As shown in the illustration, which of the listed actions of the synchroscope pointer is occurring?
Revolving rapidly in the fast direction.
201) At high discharge rates, nickel-cadmium storage batteries are superior to lead-acid batteries because they
can be charged and discharged many times without much damage
202) Attempting to parallel an AC generator which is out of phase with the bus will result in which of the following problems?
The breaker should trip.
203) Automatic voltage regulators provided on switchboards function to
vary the field excitation to the generators
204) Batteries used for diesel engine starting should
be located as close as possible to the engine
205) Battery capacities are given in
ampere-hours
206) Battery charging rooms should be well ventilated because the charging process produces
explosive gases
207) Before any work on electrical or electronic equipment is performed, which of the following precautions should be carried out?
Secure and tag the supply circuit breaker in the open position.
208) Before reassembling any machinery, you should
clean any corroded surfaces and file all burrs smooth
209) Caution must be exercised during the charging of lead-acid storage batteries as
hydrogen gas is being continuously liberated
210) Common nickel-cadmium and nickel-iron storage batteries utilize
alkaline secondary cells
211) Diesel generators #1 and #2 are operating in parallel at near full load capacity Diesel generator #1 suddenly trips out mechanically due to low lube oil pressure The reverse power relay functions properly and trips generator #1 electrically off the bo
Strip the board of all nonvital circuits.
212) During discharge of a lead-acid storage battery, which of the following actions occurs?
The acid becomes weaker.
213) During the charging process of storage batteries, the charging rooms should be well ventilated because
highly explosive gases will otherwise accumulate
214) Electric circuits are protected against overloads and short circuits by means of a/an
circuit breaker
215) Electric current is the flow of electrons through a conductor; the rate of this flow is measured in
Amperes
216) Equal power factors on paralleled AC generators are maintained by an automatic
voltage regulator
217) Equalization of the power factors of two alternators operating in parallel is accomplishe
automatically, by automatic voltage regulators
218) From the standpoint of safety, you should never allow salt water to enter a lead-acid storage battery or come in contact with sulfuric acid because
the resulting gas is a respiratory irritant that can be fatal
219) If a 6 volt battery were connected in series with a 24 volt battery by putting their negative terminals together, what would be the result?
18 volts, positive on the 24 volt battery
220) If a fuse of correct size and type blows frequently,
look for trouble within the circuit
221) If a transformer is connected to a DC source, the transformer will overload at the
primary coil
222) If air gap readings for an electical generating machine have changed significantly from the last reading, you should check
the bearings
223) If an alternator is to be inactive for a considerable period of time, which of the following actions should be taken?
The brushes should be lifted off the slip rings to prevent pitting of the metal by electrolytic action.
224) If many turns of an alternating current coil for a contactor become short circuited, the coil
will probably burn out immediately
225) If the energy input is significantly reduced to the prime mover of one shipboard alternator operating in parallel with others, that alternator will
begin to motorize and then trip out
226) If the excitation is increased to one of two alternators operating in parallel, th
power factor will change in the lagging direction
227) If the excitation of an alternator operating in parallel is decreased below normal, its
power factor will change in the leading direction
228) If the illustrated EL-0059 device is fully discharged, what will be the result?
The electrolyte will be maximum water minimum sulfuric acid.
229) If the pointer of the synchroscope is rotating in the slow direction when you are preparing to parallel two alternators, the
loaded alternator is turning faster than the incoming machine
230) If three AC generators are operating in parallel, and one of them were to pull out of synchronism with the other two generators, the
AC generator pulling out of synchronism will vibrate severely
231) If two AC generators have just been placed in parallel, the true power load is initially distributed evenly by
adjusting the governor control settings
232) If violent gassing occurs when a lead-acid storage battery is first placed on charge, the
charging rate is too high
233) In a 60 Hz AC system, the current will pass through one complete cycle in
.016 of a second
234) In a three-phase, open-delta connected transformer, the line current is equal to
the phase current
235) In an AC generator, pitting of collector rings will cause I sparking II Chattering
neither I or II
236) In electric circuit schematics, a transformer is represented by which of the symbols shown in the illustration EL-0059?
A
237) In replacing a defective transformer with a new one, which of the following actions must be carried out to insure proper operation of the equipment it serves?
The transformer connections must be made as before with regard to the indicated polarity.
238) In the illustration EL-0033, the the device E is the
trip bar
239) In the illustration EL-0039 circuit, A, B, C, and D are each 12 volts What is the voltage of the lead connected to C and D with respect to the lead connected to A and B?
(+) 24 volts
240) In the illustration, D is the symbol for a/an
fuse
241) In which section of the 24 VDC power supply circuit illustrated, does the greatest change in voltage level take place when fed from ships power
I
242) Kilowatt load is divided between two AC generators operating in parallel by
adjusting the governor controls
243) Local action in a dry-cell, or lead-acid storage battery is the process whereby
the battery becomes discharged without being connected to a load
244) Local action in a nickel-cadmium battery is offset by
trickle charging
245) Loss of or weak residual magnetism in an alternator or generator can be corrected for by
using a storage battery or battery charger to flash the field
246) Maintenance of alkaline batteries should include
trickle charging
247) Mercury filled thermometers should never be used to determine the temperature of the battery electrolyte because accidental breakage of the thermometer can cause
severe sparking and explosions
248) Motorization of an alternator is undesirable because
it puts an additional load on the bus
249) Nickel-cadmium batteries are superior to lead-acid batteries at high discharge rates because they
deliver a large amount of power and can be recharged in a shorter time
250) Nickel-cadmium storage batteries are superior to lead-acid batteries because they
can remain idle and keep a full charge for a long time
251) On large generators, space heaters are used to
maintain rotor and stator winding temperatures above the dew point to prevent the formation of condensation
252) On some electrical generating equipment one outboard bearing pedestal is insulated from the bedplate To check this insulation with the machine assembled you should use a
millivolt meter and a jumper with the machine running
253) On some electrical generating equipment one outboard bearing pedestal is insulated from the bedplate To check this insulation with the machine assembled you should use a
millivolt meter and a jumper
254) On the meter scale illustrated, while using the R X 1 scale, the reading at E will be
2.0 ohms
255) One factor that determines the frequency of an alternator is the
speed of the rotor
256) One horsepower is equal to
746 watts
257) Power transformers are rated in
Kilovoltamperes
258) Prior to closing the breaker when paralleling two AC generators, the recommended practice is to have the frequency of the incoming machine
slightly greater than the line frequency
259) Prior to starting an AC generator prime mover, the voltage regulator cutout switch should be placed in the
manual position
260) Proper storage battery maintenance includes
keeping connections tight and casing surfaces clean
261) Proper storage battery maintenance includes
applying petroleum jelly to connections to minimize corrosion
262) Regarding an AC generator connected to the main electrical bus; as the electric load and power factor vary, a corresponding change is reflected in the generator armature reaction These changes in armature reaction are compensated for by the
voltage regulator
263) Regarding battery charging rooms, ventilation should be provided
at the highest point of the room
264) Routine maintenance of lead acid batteries should include
all of the above
265) The amount of voltage induced in the windings of an AC generator depends mainly on
the strength of the magnetic field
266) The amount of voltage induced in the windings of an AC generator depends on
all of the above
267) The apparent power in a purely inductive circuit is also known as
reactive power
268) The basic operating principle of a transformer is attributed to
electromagnetic induction
269) The capacity of a storage battery is measured in
ampere-hours
270) The charge of a lead-acid battery can be restored by
passing a direct electric current through the cell
271) The charge of a lead-acid battery is checked with a
Hydrometer
272) The charging of lead-acid storage batteries will always result in
a dangerously explosive gas being liberated
273) The cycles per second developed by the alternator aboard your vessel is determined by
the speed of the engine driving the alternator
274) The division of kilowatt load between two paralleled alternators is determined by the
load-speed characteristics of the governors
275) The division of the kilowatt load between two AC generators operating in parallel is controlled by the settings and characteristics of the
prime mover governors
276) The division of the reactive KVA load between paralleled AC generators is initiated by the
voltage regulators
277) The dry-cell batteries, shown in the illustration EL-0070 are connected in
parallel
278) The dry-cell batteries, when connected as shown in the illustration EL-0070, would produce
1.5 volts
279) The electrolyte in a lead-acid storage battery consists of distilled water and
sulfuric acid
280) The electrolyte used in a nickel-cadmium battery is distilled water and
potassium hydroxide
281) The freezing point of the electrolyte in a fully charged lead-acid battery will be
lower than in a discharged battery
282) The frequency of an AC generator is adjusted by means of the
prime mover governor control
283) The frequency of an AC generator is controlled by the
Governor
284) The frequency of an alternator at a given RPM is determined by the
number of magnetic poles
285) The frequency of an alternator is controlled from the main switchboard by adjusting the
governor control
286) The frequency output of an operating alternator is controlled by the
relative speed of the rotor poles
287) The governor control switch of an alternator is moved to the raise position This action will
raise the no-load speed setting of the governor
288) The illustrated EL-0031 lead acid battery is about to be placed in service The negitive plate, labeled E, is made of
sponge lead (Pb)
289) The illustrated EL-0031 lead acid battery is about to be placed in service The positive plate labeled D is made of
lead peroxide (PbO2)
290) The joule is the base unit of:
Energy si work
291) The kilowatt load can be adjusted on a paralleled generator by using the
governor control
292) The KW load is evenly distributed between two alternators just placed in parallel by adjusting
the governor settings
293) The load sharing characteristics of two diesel generators operating in parallel are mostly dependent on their governor
speed droop settings
294) The main purpose of an electric space heater installed in a large AC generator is to
prevent moisture from condensing in the windings during shutdown
295) The main purpose of an electric space heater installed in a large AC generator is to
prevent moisture from condensing in the windings when the machine is shutdown
296) The most common type of AC service generator found aboard ship is the stationary
armature, rotating electromagnetic field type
297) The most practical way to control the voltage output of an AC generator is to vary the
strength of the rotating magnetic field
298) The number of cells in a 12 volt lead-acid battery is
six cells
299) The open-circuit voltage of a fully charged lead-acid battery cell is
2.0 volts
300) The opposition to the establishment of magnetic lines of force in a magnetic circuit is called the circuits
Reluctance
301) The output voltage of a 440 volt, 60 Hz AC generator is controlled by the
exciter output voltage
302) The output voltage of a three-phase alternator is regulated by the
DC voltage to the field
303) The plates of a NiCad storage battery are made of
combinations of nickel powder and nickel & cadmium salts
304) The power factor at which a paralleled AC generator operates is usually adjusted by the
field excitation
305) The power factor of an AC generator operating singularly is determined by the
connected load
306) The proper way to mix the electrolyte for a battery is to add
acid to distilled water
307) The purpose of DC generator brushes is to
conduct electric current to an outside circuit
308) The purpose of the commutator and brushes on a DC generator is to
convert the alternating voltage generated within the armature to a direct voltage
309) The purpose of the reverse power relay, provided on a ships service alternator panel, is to trip the circuit in the event of
alternator motorization
310) The reactive power drawn by a motor from an AC generator is the power which is
used to establish the magnetic field of the motor
311) The removal of paint from electrical equipment, such as generators, should be cautiously undertaken because
the paint dust is composed of abrasive and semi-conducting materials which impair insulation
312) The reset contacts of the master switch shown in the illustration are
closed only when the master switch is off
313) The RPM of an AC generator can be measured with a/an
vibrating reed meter
314) The specific gravity of the electrolyte in a lead-acid battery is measured by a
Hydrometer
315) The specific gravity of the electrolyte solution in a lead acid battery
gives an indication of the state of charge of the battery
316) The standard method of controlling the output voltage of a 440 volt, 60 Hz, AC generator is accomplished by adjusting the
alternator field excitation
317) The standard procedure for maintaining the charge in an emergency diesel starting battery is to trickle charge the battery
Continuously
318) The state of charge of a lead acid storage battery is best indicated by the
specific gravity of the electrolyte
319) The state of charge of a lead-acid battery is best indicated by the
electrolyte specific gravity
320) The true power indicated by a wattmeter depends on the current flow through the load, the magnitude of the potential across the load, and the
power factor of the load
321) The voltage developed by an AC generator is controlled by varying the
DC excitation to the field
322) The voltage output of an AC generator is accurately controlled by
varying the DC exciter voltage
323) Three 12 volt, lead-acid, batteries connected in series will develop
36 volts
324) Three factors responsible for the change in voltage as load is applied to an AC generator are: 1) the drop in resistance in the armature circuit, 2) the change in flux, and 3) the
armature reactance voltage drop
325) To determine the state of charge of a nickel-cadmium battery, you would use a/an
Voltmeter
326) To equalize the power factor of two alternators operating in parallel, the
field excitation of both units is adjusted
327) To increase the frequency of an operating AC generator, you should
increase the speed of the prime mover
328) To properly seat the brushes on slip rings, you should use
sand paper
329) To remove an alternator operating in parallel with another unit from the main electrical bus, you must FIRST
remove the load from the outgoing alternator
330) To test the state of charge of a nickel-cadmium battery, you should use a/an
Voltmeter
331) Transformer cores are laminated to reduce
eddy currents
332) Transformers are used onboard ships with AC generators to
permit higher voltage for electric motor operation and low voltage for lighting circuits
333) Two AC generators are operating in parallel and both are equipped with automatic voltage regulators While standing watch, one generator is noted as having a greater lagging kvar In order to equalize the kvars between the generators you should
decrease the voltage of the generator with the largest kvar while increasing the other generator voltage
334) Two AC generators of the same capacity are operating in parallel One with a zero speed droop setting and the other with a 5% speed droop If its capacity is not exceeded, the unit whose governor has the zero speed droop setting will
maintain the frequency of the system
335) Under normal conditions, storage batteries used for starting the emergency diesel generator are maintained in a charged state by which of the following methods?
Trickle charging
336) Upon failure of the normal power supply, the emergency generator is placed on the line by the
automatic bus transfer device
337) Upon failure of the normal power supply, the emergency generator is placed on the line by the
automatic bus transfer device
338) Violent gassing developed by a lead-acid battery during charging indicates that the
charging rate is excessive
339) Violent gassing from a lead-acid battery while it is being charged, indicates that the
charging rate is too high
340) Voltage failure of an AC generator may be caused by
failure of the exciter generator
341) Voltage generated by most AC generators is fed from the machine to the bus by means of
direct connections from the stator
342) What is the approximate voltage per cell produced by the nickel-iron (Edison) battery?
1.35 volts
343) What is the approximate voltage produced by a nickel-cadmium battery cell?
1.25 volts
344) What is the maximum allowable primary current of a 2 KVA step-down transformer with a four to one turns ratio if connected across a 440 volt line?
4.5 amps
345) What is the total current in the illustrated circuit EL-0021 with a 6 volt battery if the resistance of R1 is 2 ohms, R2 is 4 ohms, and R3 is 4 ohms?
6 amps
346) What type of rotor is used in split-phase motors?
Squirrel-cage
347) What will be the frequency of a three-phase, six pole, AC generator operating at 1800 revolutions per minute?
90 hertz
348) When a battery is continuously exposed to low temperatures, the best procedure to keep it from freezing is to
keep the battery fully charged
349) When a lead-acid battery begins gassing freely while receiving a normal charge, the charging current should
be decreased
350) When a lead-acid battery begins gassing freely while receiving a normal charge, the charging current should be
Decreased
351) When a nickel-cadium battery begins gassing while connected to the battery charging circuit, you should
do nothing as this is a normal condition when charging
352) When a transformer is used to step down voltage, the low voltage winding is
the secondary coil
353) When an alternator is to remain idle for even a few days
energize the heater circuit
354) When changing fuses and the spring clips are found to have lost their grip, they should be replaced or
clip clamps should be used
355) When charging a 100 amp-hour lead-acid battery,
the source of power for charging should be 2.5 volts per cell
356) When charging a nickel-cadmium battery,
the specific gravity of the electrolyte will be unaffected by the state of charge
357) When charging lead-acid batteries, the charging rate should be reduced as the battery nears its full charge to
prevent damaging battery plates
358) When charging lead-acid batteries, you should reduce the charging rate as the battery nears its full charge capacity to
prevent excessive gassing and overheating
359) When checking the specific gravity of the battery electrolyte with a hydrometer, you should be aware that
warm temperatures will lower the specific gravity of the electrolyte
360) When choosing a battery for a particular application, major consideration should be given to the batterys
amp-hour capacity
361) When correcting specific gravity readings of a lead-acid battery for existing temperature conditions, you should
add 4 points for each 10° above 80°F
362) When lead-acid batteries are charging, they always give off hydrogen gas that is
highly explosive
363) When mixing electrolyte for a lead-acid storage battery,
always pour the acid into the water
364) When mixing electrolyte for a lead-acid storage battery, you should pour the
acid into distilled water in a glass container
365) When mixing electrolyte, which of the following precautions should always be observed?
Add the acid to the water.
366) When paralleled, AC generators must have the same
all of the above
367) When paralleling two AC generators, the frequency (cycles) of the incoming generator, just prior to closing the circuit breaker, should be
slightly more than the frequency of the generator on the line
368) When paralleling two AC generators, the frequency of the incoming machine immediately prior to closing its breaker should be
slightly greater than the bus frequency
369) When paralleling two AC generators, the frequency of the machine coming on-line, immediately prior to closing its breaker, should be
slightly greater than the bus frequency
370) When paralleling two AC generators, the synchroscope selector switch and frequency meter switch should be set up to sense the frequency of the
- oncoming generator
371) When paralleling two alternators the synchronizing lamps grow dim and are totally darkened as the synchroscope pointer approaches the 0° position This indicates the
incoming alternator is in phase with the bus voltage
372) When paralleling two alternators using three synchronizing lamps, the flickering of all three lamps becomes progressively slower and slower This means the
frequency of the incoming generator is approaching that of the bus
373) When paralleling two alternators, the synchronizing lamps remain lit as the synchroscope pointer approaches the 0° This indicates the
synchroscope is defective or broken
374) When securing an AC generator, you should FIRST
reduce the load on the unit
375) When shore power is being connected to a ship in dry dock,
proper phase sequence must be established
376) When the current flow in a power transmission line is halved, the power loss
is divided by four
377) When the electrolyte level of a lead-acid storage battery has decreased due to normal evaporation, the level should be reestablished by adding
distilled water only
378) When troubleshooting a lead-acid storage battery, a weak or dead cell is best detected by
measuring and comparing all cells specific gravity
379) When troubleshooting an alkaline storage battery a weak or dead cell is best located by
testing each cell with a voltmeter
380) When two AC generators are being paralleled, the breaker should be closed with the synchroscope pointer rotating in the
fast direction, just before the 12 oclock position
381) When you check the specific gravity of the battery electrolyte with a hydrometer, it should be kept in mind that
a hydrometer reading is inaccurate if taken immediately after water is added to the cell
382) Which of the devices listed is indicated by the symbols lettered A to F, shown in the illustration?
Diodes
383) Which of the devices shown in the illustration automatically prevents the simultaneous operation of the windlass from both master switches?
Contact CR1D
384) Which of the following actions must be carried out prior to closing the alternator circuit breaker according to the graph shown in the illustration?
Increase the alternator voltage.
385) Which of the following activities occurs during the charging process of a lead-acid storage battery?
The specific gravity of the acid increases.
386) Which of the following components are used to convert alternating current produced in the generator windings to direct current?
Commutator and brushes
387) Which of the following conditions indicates that a lead-acid battery is being charged too rapidly?
Excessively high temperatures and gassing rates.
388) Which of the following devices should be used to measure the temperature of a battery electrolyte?
Alcohol thermometer
389) Which of the following losses is/are present in every direct current generator armature?
All of the above.
390) Which of the following problems is indicated if a lead-acid battery begins to gas violently when it is first placed on charge?
An excessive charging rate is being applied to the battery.
391) Which of the following statements about a three-phase wye connection is correct?
The line voltage is 1.73 times the phase voltage.
392) Which of the following statements concerning nickel-cadmium batteries is true?
Nickel-cadmium batteries can be stored for a long time and still keep a full charge without additional charging.
393) Which of the following statements concerning the specific gravity of a battery electrolyte is true?
The specific gravity reading is lowered when the electrolyte is heated.
394) Which of the following statements is true concerning a stepdown transformer in an operating AC power circuit?
Voltage decreases as current increases.
395) Which of the following statements is true concerning all three-phase alternators?
Each has three separate but identical armature windings acted on by one system of rotating magnets.
396) Which of the following statements is true concerning the operation of two alternators in parallel?
The cycles per second of each alternator are the same.
397) Which of the following temperatures represents the maximum allowable temperature for the electrolyte of a lead-acid battery?
125°F
398) Which of the listed battery charging circuits is used to maintain a wet-cell, lead-acid, storage battery in a fully charged state during long periods of disuse?
Trickle charging circuit
399) Which of the listed figures shown in the illustration EL-0084 represents devices connected in a three-phase delta-wye arrangement?
C
400) Which of the listed forms of water should be added to a lead-acid battery?
distilled water
401) Which of the listed ranges represents specific gravity corrected for temperature for the electrolyte of a fully charged portable lead-acid battery?
1.280 to 1.300
402) Which of the listed safety features should be provided in small rooms or lockers where batteries are stored?
An exhaust duct is to be provided and led from the top of the locker to the open air.
403) Which of the problems listed will occur if a lead-acid battery is allowed to remain in a discharged condition for a long period of time?
The battery may be unable to accept a full charge.
404) Which of the processes listed occurs during the charging of a lead-acid storage battery?
Positive plates change to lead peroxide.
405) Which of the substances listed should be applied to battery terminals to help prevent corrosion?
Petroleum jelly
406) Which of the synchroscope illustrations EL-0053 depicts the appropriate direction of rotation and position for closing the circuit breaker when paralleling AC generators?
D
407) While paralleling two (2) AC generators using synchronizing lamps only, both lamps will go dark when the generators are
in phase
408) Why is it desirable to operate paralleled AC generators at the same power factor?
Circulating currents are kept to a minimum.
409) You are attempting to parallel two AC generators and the synchroscope pointer is revolving in the slow direction This indicates that the frequency of the incoming machine is
lower than the bus frequency
410) You are attempting to parallel two AC generators and the synchroscope pointer is revolving slowly in the fast direction You should
close the circuit breaker when the synchroscope pointer approaches the 0° position
411) You are attempting to parallel two AC generators and the synchroscope pointer stops at a position other than 0° If you close the circuit breaker at this moment
a hazardous condition will be created by the cross current between the machines
412) You are attempting to parallel two AC generators and the synchroscope pointer stops at a position other than 0° prior to closing the circuit breaker This indicates
the frequency of the incoming machine is the same as the bus frequency
413) You are attempting to parallel two AC generators, and the synchroscope pointer is revolving in the fast direction This indicates that the frequency of the incoming machine is
higher than the bus frequency
414) You are paralleling two alternators The synchronizing lamps grow dim and are totally darkened as the synchroscope pointer approaches the 0° position This indicates that the
circuit breaker can be closed
415) You can determine if a circuit breaker has tripped by
examining the position of the handle
416) A burned-out LED should be indicated by
no illumination
417) A loud buzzing noise in an AC controller is probably caused by
a broken shading coil
418) A shading coil used in an AC magnetic controller, functions to
reduce vibration and noise in the contactor
419) A temperature instrumentation system for an engine room console consists of a resistance temperature detector (RTD), a measuring bridge circuit, and a meter (or alarm circuit)Which of the following statements is true concerning the measuring bridge circuit
The resistance bridge is said to be balanced when its output voltage is zero.
420) A tubular fuse should always be removed from a fuse panel with
fuse pullers
421) Aboard ship, a grounded field coil in an AC motor can be determined by using a
Megohmmeter
422) An advantage of DC motors over AC motors is that they
- offer a more effective means of controlling speed
423) An electrical connection between the wiring of an electric motor and its metal frame is known as a/an
Ground
424) As shown in the illustrations, feedback or rudder angle repeatback is used by the steering stand in which operational modes?
Gyro-compass and hand steering only
425) As shown in the illustrations, ordered rudder angle is fed back from the
power unit to the magnetic amplifier
426) Before touching a small capacitor connected to a de-energized circuit, or even one that is completely disconnected, you should
short circuit the terminals to make sure that the capacitor is discharged
427) Compressed air should not be used to clean motor controller equipment because
it may force metallic particles into coil insulation
428) Electrical failures in motors are caused by the breakdown of insulation, which may be caused by
all of the above
429) Encrusted dirt accumulated inside a motor should be removed with a
fiber scraper
430) For more complete vessel protection when using an impressed current cathodic system
straps connect the rudder with the hull and the propeller shaft is grounded through a slip ring/brush arrangement
431) If 450 volts AC were measured across the load as shown in the illustration EL-0083 it would indicate a/an
- open winding between X1 and X4
432) If a small electric motor has been submerged in saltwater for a short period of time, you should
rinse it with warm freshwater and bake it dry in an oven
433) If a small electric motor is imersed in salt water it should be I washed in fresh water II dried in an oven
both I and II
434) If an electric motor fails to start, you should FIRST check the
fuse or circuit breaker
435) If the illustrated EL-0007 motor fails to start and gives a loud hum when the start button is pushed, the problem is
- one of the phases to the motor is not energized because of an open motor lead
436) If the line voltage to the controller shown in the illustration is 440 volts, what voltage is applied across the motor when contacts S close?
220 volts
437) If the line voltage to the controller shown in the illustration is 440 volts, what is applied across the control circuit?
440V
438) If the motor fails to start and a voltmeter reading between 1 and 6, as illustrated in EL-0007, indicates line voltage, your next step should be to
reset and determine the cause of the overload
439) If there is a reduction in the normally supplied frequency to a 120/240 volt, three-phase AC current motor from 60 hertz to 55 hertz, the motor would
run at a slower speed
440) Impressed current cathodic protection is used on vessels instead of
sacrificial zincs
441) In a cartridge-type fuse, the metal element is contained in a
fiber tube
442) In an AC generator, direct current from a separate source is passed through the windings of the rotor
by means of slip rings and brushes
443) In an impressed current cathodic protection system, the anode is
insulated from the hull and does not waste away
444) In the illustration EL-0031, the component labeled G is
hard rubber, plastic or bituminous composition
445) In the illustration EL-0042 if the compressor fails to start but the condenser fan motor is running the problem is
the overload is open
446) In the illustration EL-0043 if the compressor fails to start but the condenser fan motor is running the problem is
the overload is open
447) Magnetic controller contacts may become welded together during operation because of
low contact pressure
448) Motor controller or starter contacts may become pitted and welded together if the contacts
close slowly with light pressure
449) Motor starter or controller contacts may become welded together if the contacts
close under excessive starting current
450) Protection against sustained overloads occurring in molded-case circuit breakers is provided by a/an
thermal acting trip
451) Reduced voltage applied to a motor during the starting period will
lower the starting current and increase accelerating time
452) Section II of the circuit shown in the illustration is the
rectifier
453) Since fuse elements are made of zinc or any alloy of tin and lead, the melting point of the fuse element must be
lower than that of copper
454) The amount of current flow required for the cathodic protection of a vessel is dependent upon the
all of the above
455) The basic measuring unit of inductance is the
Henry
456) The cross-sectional area of shipboard electrical cable is expressed in
circular mils
457) The device shown in the illustration EL-0083 is being used
in a step-down operation
458) The device that most commonly utilizes the principle of electromagnetic induction is the
Transformer
459) The greatest detrimental effect on idle electrical equipment, such as cargo pump motors, is the
absorption of moisture in the insulation
460) The illustrated EL-0024 circuit is a wheatstone bridge If the meter G reads 0 with the switch closed then
the current through R1 - R2 is equal to the current through R3 – Rx
461) The main difference between a motor control circuit containing low voltage protection and low voltage release is that the latter contains
a momentary-contact start button
462) The motor starts when the start button in the illustration EL-0007 is pushed, but stops when the button is released the trouble is
a faulty holding relay contact
463) The only point in the steering stand shown in the illustration which needs periodic lubrication is the
steering wheel bearing
464) The part of a fuse that melts and opens the circuit is made of
zinc or an alloy of tin and lead
465) The primary function of an electric motor is to
develop torque
466) The proper way to apply plastic electrical tape to an electric cable splice is to
wind the tape so that each turn overlaps the turn before it
467) The purpose of an impressed current cathodic protection system aboard ship is to
prevent corrosion of the hull, propeller, rudder and line shafting
468) The speed of a squirrel-cage motor is usually changed by
changing the number of connected poles in the stator
469) The symbol in figure A shown in the illustration EL-0065 represents a
unijunction transistor
470) The turns ratio of device A shown in the illustration EL-0082 is four to one and all taps are evenly spaced If 110 volts were applied to terminals X1 and X3, what would be indicated across H1 and H2?
220 volts
471) The Wheatstone bridge is a precision measuring instrument utilizing the principle of changes in
Resistance
472) Time delayed or delayed action-type fuses are designed to
permit momentary overloads without melting
473) To effectively clean a commutator in good physical condition, you should use
a canvas wiper
474) To repair a small electrical motor that has been submerged in saltwater, you should
wash it with fresh water and apply an external source of heat
475) What controls rudder movement when the Operation Selector Switch shown in the illustration is in the NFU position?
Non-followup controller
476) What precaution should be taken with a vessels impressed current cathodic protection system after a drydocking period during which the hull has been painted?
The unit should remain off for the specified amount of time so as not to disturb curing.
477) What type of electric motor is commonly used to start small auxiliary diesel engines?
Series
478) What will be the phase angle relationship of a six-pole, three-phase, rotating field generator?
120°
479) When power is restored after a complete power failure, a steering gear pump motor will
restart automatically
480) When reading electrical motor controller diagrams, it helps to know that
current paths in the power circuit are drawn as heavy lines and in control circuit as lighter lines
481) When removing ball or roller bearings from the shaft of a motor, you should use a
wheel puller
482) When testing a capacitor with an analog type ohmmeter, a good capacitor will be indicated when
the meter deflects to a low resistance value and slowly increases towards infinity
483) When testing for blown fuses in a three-phase supply circuit to a motor, you should first
ensure the circuit is de-energized, and then use a continuity tester
484) When the motor shown in the illustration EL-0010 is running and the stop button is pushed, which of the following statements will hold true?
Contacts M and CR will open.
485) When troubleshooting a console circuit card which is suspected of being faulty, the first step would be to
de-energize and pull the card to visually inspect for burned components
486) Which component of the circuit shown in the illustration EL-0081 is the ballast?
A
487) Which of the following actions must be carried out before a voltage tester can be used to test the three line fuses to a three-phase motor?
The starter must be placed in the STOP position to stop the motor.
488) Which of the following procedures should be used to maintain a large electric motor during periods of inactivity?
Space heaters should be used to prevent condensation of moisture.
489) Which of the following statements is true concerning the operating characteristics of a squirrel-cage motor?
Rotor slip is dependent upon the motor load.
490) Which of the illustrations listed below is representative of a motor controllers schematic or elementary diagram?
491) Which of the instruments listed could be use to locate a grounded field coil in a synchronous motor?
Megohmmeter
492) Which of the listed precautions should be taken when cleaning the internals of a motor with compressed air?
All of the above.
493) Which of the listed types of motor controllers and starters is illustrated?
Autotransformer
494) Which section of the circuit shown in the illustration changes AC to DC?
II
495) While troubleshooting a circuit in an engine room central control console, a resistor is suspected of being faulty Which of the following precautions must be observed if an ohmmeter is to be used to check its value?
Resistors circuit must be de-energized and at least one end of the component isolated.
496) A contactor differs from a relay in that:
its contacts can interrupt large motor currents.
497) A cycling ballast that turns power OFF and ON is most likely caused by:
an overheated ballast.
498) A handheld digital tachometer could give a bad reading if
partially aimed at a 60 Hz. fluorescent light
499) A hydrometer is used to measure the
specific gravity of a battery electrolyte
500) A loud buzzing noise at the contacts of a magnetic controller could indicate
misalignment of the magnet faces
501) A loud buzzing noise coming from the contacts in a magnetic controller can be caused by
dirt on magnet faces
502) A low-voltage protection circuit is used in electric motor starting equipment to
prevent the motor from restarting automatically on restoration of voltage
503) A semiconductor is a material with a
conductivity higher than a normal insulator
504) A semiconductor that decreases in resistance with an increase in temperature is known as a
Thermistor
505) A silicon controlled rectifier (SCR) is a solid state device used to change
AC to DC and control relatively high load current
506) A strain-relief device must be provided where a cord enters an appliance. The purpose of this device is:
to prevent the cord from being pulled out of the appliance.
507) A trilight or dual filament lamp is rated for 40-60-100 W. This bulb would contain:
- one 40-W and one 60-W filament.
508) An electromechanical relay is basically:
an electromagnet used to switch contacts.
509) As an armature revolves within a magnetic field, friction is developed between the rotated magnetized particles as they pass through each magnetization cycle This results in
hysteresis loss
510) As shown in the illustration, S is the
stop button
511) Component A of section I shown in the illustration represents a
Bell
512) Component B of section I shown in the illustration represents a
small generator
513) For an electromechanical relay, the amount of voltage and current required to energize the relay coil is:
more than what is required to de-energize the coil
514) High-intensity discharge lamps:
- operate at low brightness when first turned on.
515) Humming or buzzing of electric contacts is a symptom of
low voltage on the operating coil
516) If a magnetic controller contact fails to pick up when the operating coil is energized, one possible cause may be
low voltage to the coil
517) If a magnetic controller contactor fails to pick up when the coil voltage is applied to the contactor coil, the cause may be
an open contactor coil
518) If a magnetic controller relay fails to drop out when the coil voltage is removed from the relay, the probable cause may be
welded contacts
519) If deck machinery is expected to be idle for an extended period of time you should
check run at regular intervals to insure correct operation and to renew the internal coating of lubrication
520) If the approximate voltage to be measured in a circuit is not known, you should
use the highest voltage range on the voltmeter
521) In the pitch control diagram shown in the illustration, what are the present plant operating conditions?
Both engines are on line, maneuvering mode is selected and the engine room is in control.
522) Magnetic controller contacts may become welded together during operating conditions as a result of
low voltage on operating coil
523) Modern handheld digital tachometers operate by counting light pulses returned to the unit by
a piece of reflective tape
524) Motor drive systems are used:
all of these
525) On tank vessels with an electrically-driven capstan, the motor should be meggered periodically to test
insulation resistance
526) Power necessary to operate the horn shown in the illustration
is supplied from a 115 volt source
527) Relays are primarily used to switch currents in the:
load circuit.
528) Relays with no contacts, which are switched entirely by electronic devices, are called:
solid-state relays.
529) The arc resulting from the tripping of a circuit breaker is prevented from damaging the contacts by
directing the arc into an arc chute
530) The best way to test an incandescent lamp filament is:
to check it for continuity with an ohmmeter.
531) The current drawn by a motor is:
both b and c
532) The diagrams shown in the illustration represent a/an
sound powered telephone system
533) The electrical energy necessary to power a sound-powered telephones small vibrating bell is obtained from
each stations hand-cranked generator
534) The electrical energy necessary to transmit a persons voice over a sound-powered telephone circuit is obtained from
the speakers voice
535) The fluorescent bulb produces light by:
means of an electron arc established between two cathodes.
536) The illustrated EL-0024 circuits are used to measure
resistance
537) The instant-start fluorescent tube:
all of these
538) The pitch controller module shown in the illustration is fed the actual pitch position of the propeller from the
pitch feedback potentiometer
539) The pitting of controller contacts can be caused by
insufficient contact pressure
540) The purpose of a magnetic relay is to
remotely open and close contacts
541) The purpose of overload protection on a motor is to protect:
the motor from sustained overcurrents.
542) The pushbutton on the handset of a ships sound-powered telephone must be depressed to
both talk and listen
543) The resistance of a 200-W, 120-V incandescent lamp would be:
lower than that of a 40-W, 120-V incandescent lamp.
544) The schematic diagram shown in the illustration EL-0069 represents which of the listed solid-state circuits?
Bridge rectifier
545) The shipboard general alarm system must receive its main source of power from
a storage battery
546) The timer element of a reverse power relay cannot be energized unless
the power flow is the same as the tripping direction
547) The timer element of a reverse power relay cannot be energized unless
the power flow is the same as the tripping direction
548) The transmit and receive elements of a sound-powered telephone handset are
identical and can be used for either function
549) The use of four diodes, in a full-wave bridge rectifier circuit, will
provide unidirectional current to the load
550) Un semiconductor a carui rezistenta electrica descreste odata cu cresterea temperaturii este cunoscut sub numele de
Termistor
551) What are the plant conditions existing in the engine speed control diagram shown in the illustration?
The Engine Room is in control in the auto. maneuver mode.
552) What do we mean by viscosity
a resistance to flow
553) What principle of measurement is the viscosity controller based on ?
measurement of differential pressure
554) When attempting to measure AC current with the device shown and you are unsure of the range, the range switch should be set to
unable to accurately measure AC current with this device as illustrated
555) When the operating handle of a molded-case circuit breaker is in the mid-position, the circuit breaker is indicated as being
Tripped
556) Which of the following applies to stopping a motor by electronically reversing the motor while it is still running in the forward direction?
Plugging
557) Which of the following devices are protected from being motorized by a reverse-power relay?
Alternators
558) Which of the following is designed to provide machine operation protection by requiring the motor to be restarted after a power failure?
low-voltage protection
559) Which of the following is not a characteristic of AC motors?
high torque at low speed
560) Which of the following is not a common application for a relay?
change alternating current to direct current
561) Which of the following is not an advantage of fluorescent lamps over the incandescent types?
lower initial cost
562) Which of the following is not an advantage of high-intensity discharge lamps?
They operate at low current.
563) Which of the following statements concerning the maintenance of solid-silver contacts in relays and auxiliary control circuits is correct?
They should be filed with a fine-cut file when projections extend beyond the contact surface.
564) Which of the following statements is correct concerning the circuits in a sound powered telephone system?
The common talking circuit is composed of two ungrounded wires.
565) Which of the following statements represents an application of a silicon controlled rectifier?
To provide DC power for a main propulsion motor.
566) Which of the following statements represents the important factor that must be considered when replacing a faulty diode in the exciter rectifier assembly?
Be certain that the replacement diode is the same polarity as the one removed.
567) Which of the following statements represents the main difference between a relay and a contactor?
Contactors can handle heavier loads than relays.
568) Which of the listed conditions describes the effect on intrinsic semiconductor operation as a result of a temperature increase?
Conductivity will increase
569) Which of the listed devices is used to measure pressure and convert it to an electrical signal ?
Transducer
570) Which of the listed precautions should be observed before spraying liquid solvent on the insulation of an electric motor?
Disconnect the motor from the power source.
571) Which of the motors for the devices listed below is fitted with an instantaneous overload relay?
Winch
572) Which of the referenced waveshapes would appear at point X of the circuit shown in the illustration?
A
573) Which of the wave forms shown in the illustration will be produced when the circuit is in use?
B’
574) A circuit breaker and a fuse have a basic similarity in that they both
should open the circuit when overloaded
575) A circuit breaker differs from a fuse in that a circuit breaker
trips to break the circuit and may be reset
576) A circuit is protected from overheating by a/an
thermal overload relay
577) A delayed-action fuse is most frequently used in which of the listed circuits?
Motor circuit
578) A four-pole induction motor, operating on three-phase 60 cycle current will operate at approximately
1,750 RPM
579) A low voltage source is being used for testing armature coils A coil short circuit will be indicated by a
low or zero voltage reading, while the other coils will have higher readings
580) A shore power circuit breaker should be closed only
when the ships generators have been removed from the bus
581) A single-phase induction motor will only start if you spin the rotor rapidly with the line switch closed After starting, its speed fluctuates between very slow and half-speed The problem probably lies in the
running winding
582) A three-phase, induction-type motor experiences an open in one phase Which of the listed automatic protective devices will prevent the machine from being damaged?
Thermal overload relay
583) A three-phase, squirrel cage, induction motor will run hot due to
- open stator coils
584) AC circuits possess characteristics of resistance, inductance, and capacitance The capacitive reactance of a circuit is expressed in
Ohms
585) An adjustable resistor, whose resistance can be changed without opening the circuit in which it is connected, is called a
Rheostat
586) An electric heating element supplied with 120 volts draws 15 amps How much power will be consumed?
1800 watts
587) An electrical device which employs a stationary armature and a rotating electromagnetic field is used aboard ship as a
ships service alternator
588) An electrical device which prevents an action from occurring until all other required conditions are met is called a/an
Interlock
589) As a general rule, the first troubleshooting action to be taken in checking faulty electric control devices is to
test all fuses and measure the line voltage
590) As shown in the illustration, what happens when A is closed, B is in position 2 and component E2 burns out?
G sounds an alarm and F illuminates.
591) Before working on an electric cargo winch master switch or controller, you should
- open the circuit breaker in the power supply and tag
592) During start-up of the circuit shown in the illustration EL-0081, it is noted that the ends of component C alternately glow and become dark without the tube illuminating The most probable cause for this is that
component A is shorted and therefore unable to produce the high voltage required to start the lamp
593) Electric strip heaters are used in motor controllers to
prevent condensation of moisture
594) Electrical circuits are protected against overheating by means of a/an
circuit breaker
595) Electrical leads and insulation on a motor should be painted with
insulating varnish
596) Excessive heat in an operating motor controller can result from
loose connections
597) Excessive humming of AC contactors may be caused by
a broken shading coil
598) Heat sinks are frequently used with
power transistors
599) If power were lost to the winch shown in the illustration while in second point hoist the winch would stop When power is restored the winch would
remain stopped until the master switch is returned to off closing the reset contacts and then moved to any run position
600) If the illustrated EL-0027 test is being performed to determine which winding is grounded and the light does not come on then
winding is not grounded and you should continue on to the next winding until the light comes on designating that winding as grounded
601) In a three-phase, squirrel-cage type, induction motor the rotating magnetic field is established by the
application of a three-phase voltage supply to the stator windings
602) In an emergency, the fastest way to interrupt power and stop the winch shown in the illustration is for the
winch operator to open the safe switch at the master switch
603) In an induction motor, rotor currents are circulated in the rotor by
inductive reaction of the rotating stator field
604) In general, polyphase induction motors can be started on full line voltage by means of
across-the-line starters
605) In the event of a power failure during cargo loading operations, the movement of an electric powered cargo winch will be stopped by
a spring set brake
606) Incandescent lamps are classified according to
all of the above
607) Magnetic controller contacts may become welded together during operation due to
low contact pressure
608) Most three-phase induction motors used for driving engine room auxiliaries are started by
across-the-line starters
609) Motor controllers are seldom troubled with grounds because
the contactors and relays are mounted on a nonconducting panel
610) Section III of the circuit shown in the illustration is a
filter
611) Some large AC motors are equipped with with heaters These could be I resistance heaters bolted directly to the frame II low voltage windings embedded in the motor windings
either I or II
612) The air gap in an induction motor should be checked periodically with a feeler gage to detect
excessive bearing wear
613) The air gap in an induction motor should be periodically checked with a feeler gage to prevent possible
rotor contact with the stator
614) The alarm system for an engine order telegraph uses small selsyn motors attached to the indicators The alarm sounds when the rotors are
not synchronized, current is flowing, and the relays are closed
615) The devices marked T in the illustration are
timing relay components whose contacts open or close depending on the setting of their pneumatic adjustment
616) The difference between the synchronous speed of an induction machine and its operating speed (slip) may be correctly expressed
as a percent of synchronous speed
617) The first requirement for logical troubleshooting of any system is the ability to
recognize normal operation
618) The heaters for the winch circuit shown in the illustration are powered from
a separate source
619) The heating of conductors as a result of resistance in a distribution circuit causes a power loss expressed as
line loss
620) The process, whereby electrons gain sufficient energy to be released from the surface of a thin, heated metal plate, is known as
thermionic emission
621) The purpose of a heat sink, as frequently used with transistors, is to
prevent excessive temperature rise
622) The purpose of R6 in the winch circuit shown in the illustration is to
act as the armature dynamic braking load to assist the winch in stopping
623) The purpose of the heater resistors for the winch circuit shown in the illustration is to
dispel moisture in the master switch housing & control panel
624) The rate at which heat is produced in a direct current circuit is equal to
I squared times R
625) The rated temperature rise of an electric motor is the
normal temperature rise above the standard ambient temperature at rated load
626) The reset contacts of the master switch shown in the illustration provides the winch controller with
low voltage protection
627) The reversal of an AC, three-phase, induction motor is accomplished by
interchanging any two of the three motor leads
628) The rotation of a three-phase induction motor can be reversed by
interchanging any two of the three line leads to the stator
629) The speed of a multi-speed, squirrel-cage, induction motor operating in a fixed frequency system can be changed by
reconnecting stator windings for different numbers of poles
630) The speed of a squirrel-cage induction motor is determined by the
number of stator poles
631) The speed of a three-phase squirrel-cage induction-type motor operating in a fixed frequency system is varied by changing the
number of stator poles
632) The synchronous speed of an induction motor is the
speed of the rotating field
633) The torque produced by a motor when its shaft will not turn, even though rated voltage is applied to the stator, is known as
locked-rotor torque
634) The winch shown in the illustration operates in any of the positions with the master switch in the lower direction, but will not hoist in any of the master switch hoist positions Which of the listed faults could be the cause?
Master switch contact MS3 may have defective springs.
635) The winch shown in the illustration will not operate in any speed in the lowering direction and at an abnormal speed in first point hoist The possible cause is that
resistor R8-A2 has an open
636) Two contributors of electronic console failures are heat and vibration To combat some of their effects, preventive maintenance procedures should include
periodic changing or cleaning of console ventilation and control room air conditioning filters
637) Under normal conditions, the speed of a two-speed squirrel cage induction motor is changed by varying the
number of field poles
638) Under which of the listed conditions can the engine room retake the throttle control from the bridge?
Any time it is deemed necessary.
639) What is indicated by gradual blackening at the ends of component C shown in the illustration EL-0081?
The tube is nearing the end of its useful life.
640) What power is consumed by a heating element using a current of 20 amperes at 120 volts?
2400 watts
641) When the control handle is in the off position, the solenoid actuated brake of the electric winch is
de-energized and the brake is set by a spring
642) When the operating handle is in the off position, which master switch contacts for the winch shown in the illustration are closed?
MS-3, 7 & Reset
643) When you are making a high potential test on a piece of repaired electrical machinery, a rise in leakage current indicates
bad insulation
644) Which component of the circuit shown in the illustration EL-0081 is the lamp?
C
645) Which of the damages listed can occur to the components of a winch master control switch, if the cover gasket becomes deteriorated?
Rapid corrosion of switch components.
646) Which of the following represents the accepted method of cleaning dust and foreign particles from electrical equipment while limiting damage to electric components?
Using a vacuum cleaner to remove debris from the components.
647) Which of the following statements describes the significance of ambient temperature in relation to the service life of electronic components?
Increased ambient temperature decreases the service life of electronic components.
648) Which of the listed conditions occur when selection is made for third point hoist on the winch shown in the illustration?
Master switch contacts 3,4, 6, 8, and 9 close.
649) Which two components, shown in the illustration, acting together will disconnect the motor from the line in case of a sustained motor overload?
E and I
650) Principial, actionarea detectorului de nivel minim ulei carter din cadrul unei instalatii de semnalizare si protectie motor auxiliar va
va declansa o alarma optica si acustica
651) Principial, actionarea detectorului de supratemperatura gaze evacuare din cadrul unei instalatii de semnalizare si protectie motor auxiliar
va declansa o alarma optica si acustica
652) Autonomia iluminatului de urgenta alimentat din baterii de acumulatori, considerat sursa tranzitorie, este de minim
1/2 ora
653) Autonomia iluminatului de urgenta alimentat din baterii de acumulatori, se considera timpul de functionare astfel incat tensiunea la bornele celui mai indepartat consumator sa nu scada cu mai mult de
0.03
654) Blocul de protectie a unui generator sincron naval se afla instalat in
sectia generatorului din TPD
655) Capacitatea bateriei de acumulatori destinate pornirii DGA trebue sa asigure
6 porniri
656) Care dintre tipurile de retea este preferata la navele comerciale ?
Radial
657) Care este abaterea maxima admisibila a tensiunii nominale ale unui generator sincron independent dotat cu regulator de tensiune?
+/- 2,5%
658) Care este numarul de bare dintr-un TPD al unei centrale in Curent Alternativ Trifazat?
3
659) Care este numarul de bare dintr-un TPD al unei centrale in Curent Continuu?
3
660) Care este tensiune unui element de acumulator acid cu Pb
2 V
661) Care este tensiune unui element de acumulator alcalin Fe-Ni
1,2 V
662) Care sunt protectiile minime necesare motorului termic de actionare a generatorului de avarie
presiune minima ungere, temperatura maxima racire, supraturatie
663) Ce rol are un corectorul de tensiune din cadrul unui regulator de tensiune inductiv?
Asigura o variatie de tensiune de maxim 2,5 %
664) Conceptual, unde este amplasat tabloul de distributie pentru iluminatul de urgenta ?
Impreuna cu statia de incarcare
665) Conditiile necesare pentru cuplarea unui generator sincron in paralel la barele TPD sunt:
egalitatea tensiunilor, egalitatea frecventelor, aceiasi succesiune a fazelor, unghi zero intre tensiunile de faza;
666) Cos fi -metru indica:
Raportul dintre puterea activa si puterea aparenta
667) Cu ce aparate electromagnetice se poate realiza protectia la suprasarcina a unui generator sincron?
releu de curent, temporizat
668) Cum controlam saptamanal rezistenta de izolatie a iluminatului de urgenta ?
De la nivelul tabloul de incarcare/distributie cu aparatele dedicate
669) Cum se realizeaza decuplarea consumatorilor neesentiali din cadrul unei CEN in CAT?
prin declansatoare ale intrerupatoarelor automate
670) Cuplarea la barele TDA a generatorului de avarie NU este conditionata de
actionarea confirmata a protectiei de suprasarcina a DGA
671) Cuplarea Tabloului de Mal la TPD este conditionata de
starea intrerupatoarelor de cuplare la bare a generatoarelor
672) De ce acumulatorul acid cu Pb este preferat in pornirea cu demaror electric a motoarelor termice ?
Deoarece pot ceda instantaneu curenti mari
673) De ce acumulatorul alcalin este preferat in alimentarea circuitelor de iluminat de urgenta ?
Deoarece uzual pot fii complet descarcati
674) De ce se prefera ca protectia la scurtcircuit a unei alimentari din TPD din cadrul unei CEN in CAT sa fie executata atat de intrerupator automat cat si de sigurante fuzibile?
Se poate regla corect nivelul de protective
675) Grupul de avarie trebuie sa functioneze independent minim
18 ore
676) In cazul iesirii din parametri reglati, blocul de protectie a unui generator sincron naval
decupleaza generatorul de la bare
677) In cazul iesirii din parametri reglati, blocul de protectie a unui generator sincron naval actioneaza asupra
intrerupatorului automat de cuplare la bare al generatorului
678) Uzual, in conditii normale ale unei CEN in CAT , TDA este alimentat direct din
TPD
679) Indicati in care din situatiile prezentate, motoarele auxiliare de mare putere sunt oprite?
Intreruperea functionarii exhaustoarelor de gaze din carterul motorului.
680) La functionarea in paralel a doua generatoare sincrone de puteri egale observam o incarcare de puteri active egala dar o incarcarea de curent de sarcina inegala Acest fapt se datoreaza unui
reglaj incorect al regulatorului de tensiune
681) La navele comerciale se prefera o retea radiala deoarece
se asigura o buna selectivitate a protectiilor
682) O Centrala Electrica Navala include
sursele de energie electrica si tabloul principal de distributie
683) Pe sectiunea din TPD a unui generator sincron din cadrul unei CEN de CAT vom avea minim urmatoarele aparate de masura:
un voltmetru dublu, un frecventmetru dublu, un kilowattmetru, un ampermetru de sarcina
684) Pentru ca doua generatoare sincrone navale, actionate de motoare auxiliare, sa poata functiona in paralel trebuie ca
puterile lor sa nu difere mai mult cu 1/3
685) Pentru ca doua generatoare sincrone navale, actionate de motoare auxiliare, sa poata functiona stabil in paralel, trebuie ca
sa existe o reactie inversa intre regulatoarele de tensiune
686) Pot functiona in paralel un DG si un turbo-gen ?
Da - daca avem un sincro-repartitor de sarcina
687) Protectia Mayer din cadrul unei CEN in CAT este
protectie progresiva la suprasarcina cu decuplarea consumatorilor ne-esentiali
688) Releul de putere inversa:
Pastreaza functionarea masinii electrice ca generator
689) Separatoarele de bare se folosesc la
separarea pe sectiuni a barelor tabloului principal de distributie
690) Sincronoscopul este folosit la
Punerea in paralel a generatoarelor de CA
691) Sistemul de iluminat de urgenta alimentat din baterii de acumulatori este considerat sursa tranzitorie
atunci cand exista si DGA
692) Sistemul trifazat cu nul izolat, folosit in CEN de CAT, se justifica prin
posibilitatea controlului permanent al rezistentei de izolatie
693) Un grup DG portabil asezat pe punte si cuplat la TPD prin tabloul de mal pate fi considerat o sursa de energie electrica de avarie ?
Nu - deoarece alimenteza TPD si nu un grup de consumatori dedicati
694) Uzual, blocul de protectie a unui generator sincron actioneaza asupra intrerupatorului automat de cuplare la bare prin
bobina de minima tensiune
695) Uzual, un intrerupator automat folosit la cuplarea unui generator sincron ? 30 KVA la barele TPD are incorporat urmatoarele protectii:
scurtcircuit si tensiune minima
696) Actionarea motoarelor electrice ale pompelor de combustibil, transfer ulei si separatoare trebuie sa fie dotate cu
sisteme de deconectare de la distant
697) Alimentarea cu energie electrica a pompelor aferente MP se face :
direct din TPD
698) Alimentarea instalatiilor de automatizare necesare pornirii si functionarii generatorului de avarie se face din
bateriile de acumulatori dedicate sau bateriile de acumulatori de pornire
699) Alimentarea sistemului de comanda la distanta a instalatiel de guvernare se face
din circuitele de alimentare ale instalatiei
700) Arzatorul caldarinei asigura:
Pulverizarea combustibilului,debitul de aer necesar arderii, initierea aprinderii si controlul flacarei.
701) Cand sarcina variaza instantaneu cu 100%, variatia de turatie nu trebuie sa fie mai mare de:
10% din turatia nominal
702) Comanda de la distanta a electromotoarelor pompelor aferente MP se face cu ajutorul :
contactoarelor de comanda
703) Dispozitivul auxiliar de actionare a carmei trebuie sa asigure bandarea de la 5° intr-un bord la 5° in celalalt bord in maxim
60 sec
704) In care din situatiile mentionate mai jos se declanseaza semnalizarile optice si sonore, pe treapta I-a de protectie a MP?
Presiunea uleiului de ungere a motorului principal a scazut pana la valoarea minima treapta I-a.
705) In care situatie de avarie se semnalizeaza si se reduce automat turatia motorului principal ?
Temperatura uleiului de ungere a motorului principal a crescut pana la valoarea maxima, treapta a-II-a.
706) In cazul aparitiei unei suprasarcini de lunga durata la un electromotor pompa transfer combustibil :
electromotorul este oprit
707) In cazul aparitiei unei suprasarcini de scurta durata la un electromotor pompa racire ulei MP :
electromotorul nu este oprit
708) In cazul scaderii frecventei tensiunii de alimentare cu 3% din valoarea nominala, elecromotorul pompei de racire injectoare in funciune :
nu se opreste
709) In cazul scaderii tensiunii de alimentare la 90 % din valoare, electromotorul pompei de racire cilindrii in functiune :
nu se opreste
710) In ce situatie de avarie se semnalizeaza si se opreste automat motorul principal?
Presiunea uleiului de ungere a motorului principal a scazut la valoare minima treapta a II-a..
711) In regim normal de functionare, comanda de oprire a compresorului instalatiei frigorifice este data de :
Releul de presiune minima montat pe conducta de aspiratie spre compresor.
712) In urma unui BLACK-OUT care a dus la oprirea MP, dupa aparitia tensiunii la barele TPD :
pornesc pompele aferente MP care au fost in stand-by inainte de BLACK-OUT
713) Indicati ce marimi urmaresc circuitele de protectie si semnalizare ale MP:
Valorile temperaturilor pentru : apa racire motor principal, ulei ungere motor principal, ulei reductor, ulei lagar axial si valorile presiunilor pentru : ulei ungere motor principal, ulei comanda, ulei ungere reductor.
714) Instalatia de telecomanda a motorului principal asigura :
Lansarea motorului; reglarea turatiei; oprirea motorului; inversarea sensului de rotatie al arborelui portelice; semnalizarea depasirii parametrilor nominali; protectie in cazul aparitiei unor avarii.
715) La cresterea temperaturii apei de racire a motorului pana la valoarea maxima treapta a II- a, schema de protectie executa:
Semnalizarea optica; acustica si reducerea automata a turatiei pana la valoarea corespunzatoare mersului la relanti.
716) La cuplarea virorului, lansarea MP este blocata printr-un
Limitator
717) La pompele alimentare cu combustibil MP stand-by-ul este asigurat prin :
Presostat
718) La pompele ulei ungere MP stand-by-ul intra in fucntiune cand :
a+b
719) La scaderea presiunii uleiului de ungere a motorului principal pana la limita minima treapta I- a, schema de protectie executa:
Semnalizarea acustica si optica
720) Masina carmei trebuie sa asigure bandarea de la 35° dintr-n bord la 30° in celalalt bord in maxim
28 sec
721) Motoarele electrice de actionare a carmei trebuie sa suporte timp de un minut suprasarcini de
1,5 ori
722) Motoarele electrice de forta ale unei masini de carma electrohidraulice au oblogatoriu
doua sisteme de alimentare cu energie electrica
723) Motoarele electrice de forta ale unei masini de carma electrohidraulice au protectii la
Scurtcircuit
724) Pe timpul executarii degivrarii in instalatia frigorifica, schema electrica realizeaza:
Blocarea circuitului de absortie spre compresor,intreruperea alimentarii termostatelor, intreruperea ventilatiei si conectarea rezistentelor de incalzire pentru topirea ghetei.
725) Pompele duble ulei MP pot avea pornirea :
local + remote din tabloul de comanda + remote din PC-urile de comanda (din PCC si CN)
726) Pornirea electromotoarelor care actioneaza pompele aferente unui MP cu o putere de 15000 KW, se face prin:
pornire directa
727) Protectiile electromotoarelor care actioneaza pompele aferente MP sunt :
suprasarcina, scurcircuit
728) Schema de protectie a caldarinei actioneaza numai prin semnalizare optica si sonora in urmatoarele situatii:
Nivel ridicat sau scazut al apei in caldarina,presiune scazuta combustibil.
729) Sistemele de guvernare trebuie sa asigure un numar de
350 deplasari ale carmei pe ora
730) Amplificatoarele electrice utilizate in domeniul naval sunt construite cu tranzistoare :
NPN si PNP deci a+b
731) Amplificatoarele hidraulice pot fi amplasate :
- orice pozitie relative
732) Ce se va intampla atunci cand bobina tranei electromagnetice a unui vinci de marfa se va arde?
frana va bloca rotorul sub actiunea resoartelor
733) Functionarea analizoarelor de ceata se bazeaza pe principiul :
Opacitatii
734) In cadrul sistemului de monitorizare-control, semnalul (temp,.presiune,debit.etc.) este transformat si amplificat cu amplificatoare :
electrice + magnetice si hidraulice+pneumatic deci a+b
735) In cazul motoarelor navale, pentru masurarea temperaturii se foloseste :
metoda de masurare prin dilatare termica si metoda electrica de masurare deci a+b
736) In domeniul naval, pe MP, cel mai utilizat este traductor cu platina :
Pt 100
737) La analizorul de ceata tip Graviner model comparator, continutul tubului de referinta este format din :
ceata de ulei normal
738) La analizorul de ceata tip Graviner, model level, continutul tubului de referinta este format din :
aer curat
739) La depasirea concentratiei maxime admise a cetii de ulei in carter :
MP isi reduce automat turatia
740) Masurarea debitului in cadrul operatiunilor de supraveghere si protectie a MP se face cu ajutorul :
debimetru diferential + debimetru electromagnetic si debimetru cu turbine deci a+b
741) Masurarea nivelului in tancul de combustibil greu al MP poate fi facuta cu :
traductoruld e nivel diferential
742) Masurarea turatiei MP se face cu ajutorul tachometrelor :
mecanice , electrice si electronice si magnetice si stroboscopice deci a+b
743) Metoda electrica utilizeaza pentru masurarea temperaturturii parametrilor MP :
termorezistente si termistoare termocupluri deci a+b
744) Motorul electric folosit la vascosimetru este un motor cu putere cuprinsa :
0,5 - 1 KW
745) Analizoare de ceta tip Graviner model comparator se folosesc la MP :
lente cu cap de cruce
746) MP dotate cu analizoare de ceta tip Groviner model level se folosesc la MP :
semirapide si rapide
747) Presostatul este un regulator :
Neliniar
748) RA pentru procese rapide se fosloseste la reglarea :
Turatiei
749) Regulatoarele automate de presiune pot fi :
directe si electronice si indirecte si specializate deci a+b
750) Regulatoarele automate de temperatura pot fi :
directe si electronice si indirecte si specializate deci a+b
751) Regulatoarele de turatie a MP pot fi :
mecanice sau hidraulice ( tip Woodward) si electronice deci +b
752) Regulatoartele automate pentru procese lente se folosesc la reglarea :
presiune + temperatura + debit + nivel
753) T achometrele electrice ce se folosesc pentru masurarea turartiei MP pot fi :
de c.c. si c.a. cu impulsuri deci +b
754) Telegraful masinilor poate fi :
telegraf cu impulsuri sau selsine sau telegraf cu potentiometru sau butoane deci +b
755) Traductoarele de presiune se impart in :
traductoare bazate pe deformarea elastica a corpurilor sasu traductoare cu coloana de lichid + cele bazate pe schimbarea proprietatii corpurilor odata cu presiunea deci +b
756) Valvula termoregulatoare este un regulator
liniar de tip P
757) Viscosimetrul este un agregat folosit la :
mentinerea constanta a temperaturii combustibilului inainte de intrarea in MP
758) Actionarea electrica cu tiristoare a unui mecanism de actionare a instalatiilor de ridicat foloseste :
motor asincron cu o singura viteza cu schimbarea frecventei sau tensiunii aplicate
759) Care este regimul cel mai frecevent utilizat pentru instalatia de guvernare ?
Automata.
760) Care este timpul de functionare al unui motor electric de actionare a unui vinci ancora pe trapta a I-a?
30 min
761) Care sunt posibilitatile de oprire in caz de avarie ale unei macarale de bord ?
buton de oprire
762) Care sunt protectiile specifice ale vinciului de ancora actionat electric
scurtcircuit, suprasarcina, tensiune minima, lipsa operator, stop de avarie,
763) Care sunt protectiile specifice ale vinciului de ancora actionat electric
scurtcircuit, suprasarcina, tensiune minima, lipsa operator, stop de avarie,
764) Ce clasa de izolatie se utilizeaza la alegerea motorului de actionare mecanime punte :
F
765) Ce conditii trebuie sa indeplineasca un motor electric ce actioneaza un grui barca de salvare ?
conform cu diagrama de sarcina
766) Ce reprezinta franarea in contracurent unui motor electric de c.a. ?
franarea prin inversarea sensului de rotatie.
767) Ce reprezinta franarea prin cuplare inversa a unui motor electric de c.a. ?
nu exista.
768) Ce reprezinta protectia la scurtcircuit la un motor electric de c.a. care actioneaza un cabestan ?
deteriorarea rezistentei de izolatie dintre infasurari
769) Ce tip de motor se utilizeaza pentru actionarea mecanismelor de punte din punctul de vedere al gradului de protectie ?
IP54
770) Cresterea temperaturii apa dulce racire injectoare conduce la :
semnalizarea defectiune + shut down
771) Cresterea temperaturii ulei ungere MP conduce la :
semnalizarea defectiune + shut down
772) Cum este asigurata protectia liftului in momentul atingerii nivelului superior sau inferior?
Limitatori de capat de cursa.
773) Cum este realizata protectia la supratemperaturi a bobinajului unui electromotor de actionare a instalatiilor de punte de putere mare ?
Termocontacte
774) Cum se alege cablul de alimentare al unui vinci de ancora in CAT ?
dupa curentul maxim admisibil
775) Cum se alege un motor electric de c.a. care actioneaza un mecanism de ridicare ?
dupa cuplul echivalent-diagrama de sarcina.
776) Cum se poate realizata ventilatia unui motor electric in CAT , care actioneaza un mecanism de punte ?
cu ventola cuplata la axul motorului
777) Cum se realizeaza alimentarea cu energie electrica a unei macarale de bord ?
direct din TPD
778) Cum se realizeaza franarea dinamica a unui motor electric de c.a. ?
conectarea a doua faze la o sursa de c.c.
779) Cum se realizeaza inversarea sensului de rotatie la un motor electric trifazat ?
schimbarea a doua faze intre ele.
780) Cum se realizeaza protectia la suprasarcina a unui motor electric ce actioneaza un vinci de ancora ?
cu termistori introdusi intre infasurarile motorului
781) Cum sunt numerotate capetele infasurarilor unui motor electric de c.a. cu trei trepte de viteza (in cutia de borne) ?
U,V,W (1,2,3)
782) De ce trebuie sa tinem cont la alegerea unui motor electric de actionare in CAT al unui mecanism de ridicat ?
temperatura de lucru
783) E numerati modurile de franare ale unui motor electric de c.a. ?
franarea dinamica.
784) Frana electromagnetica a unui vinci electric de marfa functioneaza
automat, blocand sarcina in caz de disparitie a tensiunii de alimentare a electomotorului
785) Franarea electromotorului de actionare a vinciurilor de ancora este realizata prin :
Electromagnetic.
786) Identificati o cerinta a societatilor de clasificare privind alegerea electromotoarelor de actionare a unui mecanism de sarcina ?
proba cu greutati
787) Identificati o proba privind verificare in functionare a unui electromotor in CAT pentru instalatii de ridicat dpdv al societatilor de clasificare ?
functionare in sarcina la curent nominal
788) Identificati una dintre protectiile unei instalatii de ridicat in CAT .
la coborarea carligului
789) In actionarea electrica a vinciului de ancora avem posibilitatea deblocarii manuale progresive a franei electromagnetice Cand folosim scest dispozitiv ?
cand se deterioreaza bobina franei electromagnetice
790) In actionarea electrica a vinciului de ancora avem un rezistor in paralel cu bobina franei electromagnetice La ce foloseste acest montaj ?
la descarcarea tensiunii autoinduse la intreruperea alimentarii bobinei
791) In actionarea electrica a vinciului de ancora exista posibilitatea anularii immediate a protectiei la suprasarcina Cu se realizeaza acest luctru?
printr-ub buton situat pe controller
792) In actionarea electrica a vinciului de ancora se prefera in actionarea franei electromagnetice
- o bobina toroidala alimentata in CC
793) In cazul actionarii electrice a vinciului de ancora avem posibilitatea opririi instalatiei in caz de pericol printr-n intrerupator de pe controler, care
decupleaza linia de alimentare a releului de tensiune nula
794) In cazul actionarii electrice a vinciului de ancora pentru a preveni functionarea in contracurent (virare cu ancora la pic)
se temporizeaza actionarea franei electromagnetice
795) In cazul actionarii vinciului de marfa cu motoare de c.c. cel mai utilizat la bordul navelor este :
actionarea cu sistem generator-motor
796) In cazul aparitiei unei suprasarcini pe trapta a treia a actionarii unui vinci de ancora cu un motor asincron in trei trepte, cu rotorul in scurtcircuit
motorul electric trece pe o turatie inferioara de putere sporita
797) In cazul comenzii prin controler a unui cabestan conectarea tensiunii de alimentare se face printr-un :
contactor de linie
798) In cazul opririi unei electrosuflante :
MP poate fi pornit cu anularea unor protectii
799) In cazul unei actionari a vinciului de ancora cu un motor asincron in trei trepte, cu rotorul in scurtcircuit, se prefera pentru primele doua trepte o infasurare triundgi-dubla stea De ce?
pentru a putea trece de la un regim de turatie la altul fara a modifica cuplul electromagnetic
800) In cazul unei actionari a vinciului de ancora cu un motor asincron in trepte, cu rotorul in scurtcircuit, frana electromagnetic
blocheaza rotorul motorului
801) In cazul unei actionari a vinciului de ancora cu un motor asincron in trepte, cu rotorul in scurtcircuit, uzual, frana electromagnetica este actionata temporizat prin
marimea intrefierului ei
802) In cazul unei actionari a vinciului de ancora cu un motor asincron in trepte, cu rotorul in scurtcircuit, frana electromagnetica este alimentata printr-un circuit economizator De ce?
pentru a reduce curentul prin bobina dupa ce armatura acesteia afost actionata
803) In cazul unei actionari a vinciului de ancora cu un motor asincron in trepte, cu rotorul in scurtcircuit, sunt preferate infasurari
triunghi-dubla stea
804) In cazul unui black-out actionarea cabestanului la revenirea sursei de alimentare se face din pozitia controlerului care trebuie sa fie :
din zero
805) In conectarea la alimentare a bobinei franei electromagnetice a unei actionari electrice a vinciului de ancora, se prefera folosirea unui contactor cu suflaj magnetic al arcului electric
806) Instalatia de detectare a incendiului prin prezenta fumului se bazeaza pe
Opacitatea fumului
807) Intrerupatorul automat din TPD de alimentare a actionarii vinciului de ancora are protectii la
Scurtcircuit
808) Lansarea barcilor de salvare se face cu ajutorul electromotoarelor asincrone cu :
Gravitational.
809) Mentionati avantajul utilizarii schemei electrice de comanda cu relee si contactoare a unui vinci de incarcare actionat cu motor de c.c. :
la intreruperea brusca a tensiunii de alimentare electromotorul functioneaza in regim de franare dinamica
810) O caracteristica ce apare pe placa de timbru a unui motor de curent alternativ este
temperatura nominal
811) Oprirea electromotorului de actionare a unui grui barca salvare in caz de avarie se face prin :
Intrerupator de avarie.
812) Oprirea instalatii de guvernare in cazul unei suprasarcini la electromotorul de actionare se face prin:
Nu se face.
813) Oprirea unei electrosuflante in timpul mavrei cauzeaza :
semnalizarea + slow-down
814) Pentru functionarea vinciurilor si macaralelor actionate cu motoare asincrone in scurt-circuit se recomanda la schimbarea turatiei (vitezei) folosirea numarului de poli :
2p=4/8/32
815) Pentru pornirea ventilatoarelor magaziilor se foloseste :
pornirea directa.
816) Protectia la lipsa-tensiune sau lipsa-operator este realizata la instalatiile de ridicat prin ?
interblocaj la pornire
817) Protectia la suprasarcina pentru actionarile electrice ale vinciurilor de ancora se prefera a fi executate cu
Termocontacte
818) Reducerea turatiei MP este comandata automat cand actioneaza unul din semnalele :
Nivel inalt al temperaturii uleiului de ungere al MP + nivel inalt al temperaturii apei de racire MP sau Nivel inalt al tempertaurii gazelor de evacuare + nivel inalt al temperaturii uleiului de ungere al reductorului deci a+b
819) Rolul controlerului la o instalatie de punte este :
Comutarea treptelor de viteza.
820) Scaderea presiunii ulei ungere MP conduce la :
semnalizarea defectiune + shut down
821) Semnalizarea automata de incendiu a fost conceputa pentru a detecta automat , la timp :
Locul unde exisat incendiu.
822) Semnalul primar masurat de senzori pentru turatia MP este transformat in semnal electric masurat in :
mA
823) Senzorii pentru masurarea turatiei MP sunt in numar de :
4
824) Top bracing unit are in compunere :
doua pompe electrice de ulei
825) Top bracing unit este :
un sistem pentru amortizarea vibratiilor MP
826) Treapta de lucru a unui vinci de ancora este considerata a fi :
Treapta I si II
827) Umiditatea, ca rezultata al condensarii, poate fii redusa, in interiorul unui controler al unui vinci de marfa prin
rezistente de incalzire montate in interior
828) Un generator fara perii este destinat a functiona fara
toate cele nominate
829) Un generator sincron trifazat lucreaza la 450 V Ampermetrul de sarcina indica 300 A iar Kilowatmetrul 163,6 Kw la un factor de putere de 0,7 Care va fi diferenta de putere indicata de Kilowatmetrul cand factorul de putere creste la 0,8 ?
23.2 KW
830) Un indicator electric tahometric primeste semnalul de viteza al unui motor termic de la
un mic generator montat pe motorul termic
831) Un motor electric de mica putere poate fi pornit cu un pornitor
Direct
832) Un shunt ampermetric este conectat in
serie cu sarcina si in paralel cu aparatul de masura
833) Unde este amplasat intrerupatorul de avarie al unui grup barca salvare ?
langa butonul de actionare.
834) Care dintre propozitii este corecta?
Viteza unghiulara a miscarii de precesie este direct proportionala cu momentul fortei exterioare si invers proportionala cu momentul cinetic.
835) Care este turatia aproximativa a unui giromotor?
30.000 RPM
836) Care sunt erorile unui girocompas?
Toate cele nominate.
837) Ce este un giromotor?
Este un motor electric al carui rotor este un tor giroscopic.
838) Ce propietate a giroscopului este folosita pentru transformarea acestuia in girocompas?
Precesia
839) Centrarea unei girosfere in interiorul sferei de urmarile, la girocompasele cu element sensibil suspendat in lichid, se face cu
toate cele nominate
840) Centrarea unei girosfere in interiorul sferei de urmarile, la girocompasele cu element sensibil suspendat in lichid, se face cu ajutorul
bobine de suflaj
841) Clasificarea girocompaselor dupa modul de modul de suspensie a elementului sensibil, cuprinde:
girocompase pe inele cardanice
842) Clasificarea girocompaselor dupa modul de transformarea a giroscopului in girocompas, cuprinde:
girocompase pendulare
843) Cum se face transformarea unui giroscop liber in girocompas?
Toate cele nominate.
844) Cum se face transformarea unui giroscop liber in girocompas?
Coborarea centrului de greutate al giroscopului.
845) De cine depinde turatia unui giromotor?
de frecventa tensiunii de alimentare
846) De unde se alimenteaza giromotoarele unui girocompas?
Din convertizor dedicate
847) Eliminarea erorilor balistice ale unui girocompas se face:
prin montarea unor vase suspendate cu ulei
848) Eliminarea erorilor de viteza ale unui girocompas se face:
printr-un bloc corector sau prin tabele corectoare
849) Eliminarea erorilor de balans ale unui girocompas se face:
prin montarea a doua giromotoare
850) Girosfera este elementul specific al unui girocompas
cu suspensie in lichid
851) Greutatea girosferei si densitatea lichidului sunt calculate astfel incat, la temperatura de regim, girosfera are flotabilitate
usor negative
852) La marea majoritate a girocompaselor, ce tip de moror electric este un giromotor?
asincrone trifazate
853) Racirea girocompaselor cu element sensibil suspendat cardanic se face cu
Aer
854) Racirea girocompaselor cu element sensibil suspendat in lichid se face cu
aer sau apa
855) Sfera de urmarire asigura
alimentarea girosferei, fiind si traductorul sistemului de urmarire
856) Sistemul de urmarire asigura
mentinerii sferei de urmarire in aceiasi pozitie cu girosfera
857) Traductorul de urmarire la girocompasele cu element sensibil suspendant in aer este de tip
Inductive
858) Traductorul de urmarire la girocompasele cu element sensibil suspendant in lichid este de tip
Rezistiv
859) Traductorul de urmarire, la girocompasele cu element sensibil suspendant in lichid, comanda un
motor asincron monofazat
860) Unui girocompas, la care a intervenit o defectiune la sistemului de urmarire, mai poate fii folosit?
Da - atunci cand este posibil citirea drumului direct pe sfera de urmarire
861) Blocul derivativ al pilotului automat al navei tine cont de
viteza de variatie a marimii unghiului abaterii (viteza de deviatie de la drum) de la drum a navei
862) Blocul integrator al pilotului automat al navei tine cont de
asimetria oscilatiilor drumului navei
863) Blocul proportional al pilotului automat al navei tine cont de
marimea unghiului abaterii de la drum a navei
864) Consola de conducere a drumului navei poate functiona in urmatoarele regimuri:
urmarire(FU) sau stabilizare(AUT) sau butoane(NFU)
865) In cadrul sistemului automat de conducere a drumului navei (in circuit inchis cu doua bucle de reactie), pilotul automat este considerat
blocul regulator
866) In cadrul unui sistem automat de conducere a drumului navei (in circuit inchis cu doua bucle de reactie), reactia inversa exterioara este realizata de obicei de
Girocompas
867) In cadrul unui sistem automat de conducere a drumului navei (in circuit inchis cu doua bucle de reactie), reactia inversa exterioara poate fi realizata de
toate cele nominate
868) Pilotul automat poate functiona in urmatoarele regimuri:
urmarire(FU) sau stabilizare(AUT)
869) Sistemul automat de conducere a drumului navei contine
instalatia de guvernare, pilotul automat si circuitele de reactie inversa interioare
870) Functionarea traductorlori magnetostrictivi de ultrasunete
se bazeaza pe modificarea dimensiunilor unei bare de material feromagnetic, plasata intr-un camp magnetic variabil
871) Functionarea traductorlori piezoelectrici de ultrasunete
se bazeaza pe propietatea electro-mecano-optice ale unor cristale utilizate ca resonator
872) Sondele ultrason folosesc unde ultrasonice ce frecvente mai mari de
20 KHz
873) Traductorul de emisie poate fi si traductor de receptie ?
DA
874) Ultrasunetele, folosite la sondele ultrason navale, pot fi produse de traductori
Piezoelectrici
875) Ultrasunetele, folosite la sondele ultrason navale, pot fi produse de traductori
Magnetostrictive
876) Viteza de propagare a ultrasunetelor depinde de
temperatura, salinitatea si presionea stratului de apa
877) Care dintre formule este corecta in explicarea principiului de functionare al lochului hidrodinamic ?
Pt=Pd+Ps
878) Care dintre presiuni, este marimea de iesire din comparatorul hidraulic al unui loch hidrodinamic?
Pd (presiunea dinamica)
879) Cati electrozi are traductorul de viteza a unui loch de inductie ?
2
880) Efectul Doppler se refera la diferente de
Frecventa
881) Indicatorul de distanta parcursa proceseaza viteza in timp dupa o formula de
Integrare
882) Lochul ultrasonic Doppler masoara
viteza reala
883) Lochul ultrasonic Doppler se foloseste la masurarea reala de
viteze si distante mici
884) Lochurile se clasifica dupa principiul de functionare. Care dintre cele enumerate nu apartine acestei clasificari ?
Electronice