MARINE ENGINEERING SELF EXAMINER, ELECTRICALS- CAPT AJIT VADAKAYIL

ELECTRICAL KNOWLEDGE ON SHIPS- CAPT AJIT VADAKAYIL

 

Test for chief engineers who agree to join ships without electrical officer-

>50% marks -- Can be posted on a ship <10 years old without electrical officer

< 20% marks-- Must not be re employed as chief engineer in XXX ( pretender / senile ).

>90% marks--  Give him a special electrical allowance—he is an asset to the company.

 

20 nos easy questions , which even a common-place motor man can answer are interspersed so that the wanna –be electrical engineer does NOT throw down the towel – and stop taking the test.

Grading:

Correct- plus two marks

Wrong - minus one marks

Did not attempt- minus two marks

Time allowed- 60 minutes

                               
   

At sea you are only respected for what you are worth! A donkey on a throne is still a donkey !!

          

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1) A semiconductor that decreases resistance with an increase in temperature is known as a 

a)resistor

b)thermistor

c)diode

d)thermopile

2) Brushless generators are designed to operate without the use of 

a)brushes

b)slip rings

c)commutators

d)all of the above

3) A ground can be defined as an electrical connection between the wiring of a motor and its 

a)shunt field

b)circuit breaker

c)metal framework

d)interpole

4) Which of the following statements represents the main difference between a relay and a contactor?

a)Contactors control current, relays control voltage.

b)A relay is series connected and contactor is parallel connected.

c)Contactors can handle heavier loads than relays.

d)Contactors are made from silver and relays are made from copper.

5) The electrolyte used in a nickel-cadmium battery is distilled water and 

a)diluted sulfuric acid

b)potassium hydroxide

c)lead sulfate

d)zinc oxide

 

 6) A resistance in a circuit of unknown value is to be tested using the voltmeter/ammeter method. Therefore, the meters should be connected with 

a)both meters in series with the resistance

b)both meters in parallel with the resistance

c)the ammeter in series and the voltmeter in parallel with the resistance

d)the ammeter in parallel and the voltmeter in series with the resistance

7) One factor that determines the frequency of an alternator is the 

a)number of turns of wire in the armature coil

b)number of magnetic poles

c)strength of the magnets used

d)output voltage

 

8) The number of cells in a 12 volt lead-acid battery is 

a)three cells

b)four cells

c)six cells

d)twelve cells

 

9)  A delayed-action fuse is most frequently used in which of the listed circuits?

a)lighting circuit

b)motor circuit

c)electric heater circuit

d)radar circuit

 10) The freezing point of the electrolyte in a fully charged lead-acid battery will be

a)higher than in a discharged battery

b)lower than in a discharged battery

c)the same as in a discharged battery

d)higher than in a discharged battery, but the specific gravity will be less

 

11) Fuses are rated in

a)voltage

b)amperage

c)interrupting capacity

d)all of the above

 12) Power transformers are rated in

a)kilowatts

b)ampere-turns

c)kilowatt-volts

d)kilovolt-amperes

 13) Which of the following devices will prevent a DC generator from becoming motorized?

a)overcurrent relay

b)motorization trip

c)reverse power relay

d)reverse current relay

14) 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?

a)overspeed trip

b)thermal overload relay

c)three-pole safety switch

d)magnetic blowout coil

 

15) Across-the-line starters are used with AC motors to provide

a)reduced starting current

b)regulated starting current

c)high starting torque

d)controled starting acceleration

16) In testing a three-phase delta winding for an open circuit using a megger, you must

a)test each phase with all connections intact

b)measure the voltage across the open connections while testing

c)test the windings as parallel groups to avoid short circuiting

d)open the delta-connctions to avoid shunting the phase being tested

17) Mercury filled thermometers should never be used to determine the temperature of the battery electrolyte because accidental breakage of the thermometer can cause

a)severe sparking and explosions

b)rapid oxidation of battery plates

c)contamination of the electrolyte

d)corrosion on the battery terminals

18) The purpose of a main switchboard circuit breaker's reverse-power trip is to

a)prevent main circuit overload

b)protect the circuit breaker blowout coil

c)prevent alternator motorization

d)prevent low voltage tripout

19) Regarding an induction motor, the power developed by the rotor automatically adjusts itself to

a)power required to drive the load

b)speed required to drive the load

c)current flow in the motor stator

d)torque developed by the rotating field

20)The purpose of  a magnetic relay is to

a)open a circuit only in the event of overload

b)remotely open and close contacts

c)provide overcurrent  protection during starting

d)relay voltages at increased power

21) A semiconductor is a material with a

a)conductivity higher then a normal conductor

b)conductivity higher then a normal insulator

c)high conductivity at low temperatures

d)low conductivity at high temperatures

22) The charge of an alkaline battery is determined with a—

a)hydrometer

b)ammeter

c)voltmeter

d)hygrometer

23)The advantage of an alkali battery over a lead acid battery is—

a)it has no electrolyte loss.

b)it maintains a max voltage of 1.75

c)it has a longer life

d)all of above

 

24) If the pointer fails to come back to zero when the megger is not in use it means—

a)the megger is out of calibration

b)this is normal

c)the hairsprings are burnt out

d)the pointer is stuck

25) the power factor of an induction motor operating at full load is-

a)leading

b)lagging

c)unity

d)no change

26) In a 3 phase delta connection, the line current will be the product of phase current and

a)1.501

b)2.216

c)1.414

d)1.732

27) The principal difference between a 3 phase squirrel cage induction motor and a single phase induction motor is-

a)one is a split phase motor using a capacitor, while the other uses an inductor

b)one has a revolving field which drags the rotor slightly behind it, while the other runs in step.

c)there is no difference

d)one needs DC excitation, the other need no excitation

28) Which of the following devices are used for protection of AC propulsion motors and generators?

a)jamming relays

b)low voltage release

c)timing relays

d)phase balance relays

29) 2 alternators are operating in parallel. If there is an increase in load and decrease in voltage, the AVR will

a)cut out the field resistance

b)cut in the field resistance

c)cut in armature resistance

d)cut out armature resistance

30) A galvanometer is used to measure-

a)small voltages

b)small currents

c)large currents

d)large voltages

31) In a 3 wire system the earth wire is coloured

a)red

b)black

c)white

d)green

32) A power factor meter in ECR shows-

a)true power

b)apparent power

c)relationship between volts and amperes

d)relationship between true power and apparent power

33) Before synchronizing alternators, they must have

a)load equalised

b)same frequency

c)same voltage

d)same amperage

34) The advantage of DC motors over AC motors is that, they have-

a)higher speeds

b)handle heavier loads

c)have better speed control

d)have a longer life

35) Which of the following is not required for synchronizing alternators

a)same voltage

b)same phase rotation

c)same speed expressed as frequency

d)same KW rating

36)Temperatures in AC generators are indicated by-

a)imbedded thermocouples

b)deep well thermometers

c)pyrometers

d)standard thermometers

37) If the resistance of a circuit is doubled and the applied voltage kept constant, the current will-

a)increase 4 times

b)be doubled

c)cut into half

d)no change

38) If the polarity of a DC line is reversed the connecting motors will-

a)stop

b)increase in speed

c)reverse

d)rotate as before

39) Which of the following parts of an AC motor corresponds to the armature of a DC  motor-

a)field coils

b)stator

c)rotor

d)armature

40) Which of the following parts of an AC motor corresponds to the field of a DC motor?

a)stator

b)the field coils

c)rotor

d)armature

41) The purpose of a commutator is to—

a)keep a constant voltage

b)rectify armature current

c)convert magnetic lines of force into flux

d)keep a constant amperage

42) If a transformer was plugged into a DC circuit—

a)the fuse would blow

b)the primary would overload and the secondary would be dead

c)the secondary would burn out

d)any of above

43) A fully charged lead acid battery SG reads from—

a)1.28 to 1.30

b)1.02 to 1.07

c)1.46 to 1.48

d)1.16 to 1.20

44) The normal cell voltage of a fully charged lead acid battery is—

a)2 to 2.2

b)1.4 to 1.8

c)1.2 to 1.4

d)5.8 to 6.0

45) A megger is always used on a –

a)grounded circuit

b)live circuit

c)deenergised circuit

d)short circuit

46) A megger is used to measure

a)kilo ohms

b)mega ohms

c)milli ohms

d)micro ohms

47) A megger is a—

a)hand cranked instrument for measuring current

b)hand cranked AC generator

c)hand cranked DC generator

d)meter for measuring thickness of insulation

 

48) When megger testing a new armature coil to ground-the readings should be at least-

a)1 meg

b)100 megs

c)1000 megs

d)infinity

49) an ammeter is connected to a circuit in

a)series-parallel

b)parallel

c)series

d)contact

50) 60 cycles or Hertz meams the cycle is repeated-

a)60 times a minute

b)60 times an hour

c)60 times a second

d)none of above

51) To reverse the rotation of an AC motor-reverse

a)any 2 of the 3 leads

b)the field leads

c)the armature leads

d)both the field and the armature leads

52) Which of the following is not found on AC generators-

a)slip rings

b)commutator

c)brushes

d)field coils

53) Doubling the diameter of a wire –

a)increases the resistance 4 times

b)reduces the resistance 4 times

c)decreases the resistance 2 times

d)increases the resistance 2 times

54)Field excitation when requires is always supplied from

a)a source of DC

b)an alternator

c)a magnet

c)a selenium rectifier.

55)An oscilloscope can measure—

a)peak voltage

b)frequency

c)phase angle

d)all above

56)For charging a lead acid battery, you allow a current to flow from an external EMF source through the battery

a)in the same direction

b)in the reverse direction

c)current in same and reverse direction alternately.

d)none of above

57) A 2 pole alternator running at 3600 rpm can be paralleled with a 4 pole alternator running at—

a)3600 rpm

b)1800 rpm

c)900 rpm

d)7200 rpm

58) What is the difference between a AC generator and a DC generator—

a)AC generator has a commutator

b)DC generator has slip rings

c)AC generator has slip rings

d)none of above

59) What is the diference between a DC motor and a DC generator

a)DC generator does not have residual magnetism when put off

b)there is no difference

c)DC motor does not have commutator

d)DC motors do not have interpoles

60) If an AC generator on load slows down –

a)current drops

b)frequency drops

c)voltage drops

d)all of above

61) An electrical device for converting DC to AC is called

a)transformer

b)inverter

c)rotary convertor

d)synchronous converter

62) If an AC generator was slowed down, the following would happen within limits

a)voltage would increase

b)amperes would increase

c)frequency would increase

d)all of above

63) A 3 phase system

a)gives 3 distinct voltages out of step with each other

b)has a peak voltage 3 times every 360 degrees

c)is like comparing a single cylinder engine with a 3 cylinder engine

d)all of above

64) Power factor is

a)true power divided by the product of amperes and volts

b)true power divided by apparent power

c)KW divided by KVa

d)all of above

65)After main power is restored, a timed sequential restart of motor-driven auxilliaries is necessary  to avoid:

a)Generator overload due to many motors starting at simultaneously

b)Overloading creating earth faults

c)Overvoltage due to current surges

d)Over-frequency due to overspeed of generator

66)A 3-phase induction motor is rated at 200  Amperes. Its initial direct- on-line starting current will be approximately:

a)100A

b)200A

c)50A

d)1000 A

67)An earth fault exists on the blue line of a 100 A bilge pump circuit. A second earth fault occurs on the yellow line of a 10 A ventilation fan circuit. The likely outcome is that:

a)An open circuit occurs between earth fault and both motors trip out

b)Both motors trip out on overload

c)A short circuit occurs between earth faults and the ventilation fan fuse blows

d)A short circuit occurs between earth fault and the bilge pump fuse blows

68)The insulation resistance (IR) to earth of a new galley hot-plate is measured to be 30 Mohm. When three identical hot-plates are tested together their combined IR will be:

a)90 M ohm

b)30 M ohm

c)10 Mohm

d)6 M ohm

69)A motor is protected by a thermal overcurrent relay. After tripping on overload it will not be possible to reset the overcurrent relay because the:

a)Bimetallic strips need time to cool down

b)Starter isolator automatically applies an interlock

c)Oil dash-pot has also to be reset.

d)Line contactor spring also has to be reset

70)A 3-phase A.C. induction motor is running normally at its rated current of 150 A when a single phasing fault (open circuit) occurs in one line. The likely outcome will be:

a)Line currents: 0 A, 150 A, 300 A. Trip condition: trip on overload.

b)Line currents: 75 A, 75 A, 75 A.  Trip condition: no trip but speed falls.

c)Line currents: 150 A,150 A,150 A.  Trip condition: fuses blow on short circuit.

d) Line currents: 0 A, 180 A, 180 A. Trip condition: trip on overload.

71)The function of the fuses in a motor starter circuit is to provide:

a)Overload protection.

b)Undervoltage protection.

c)Short circuit protection.

d)Open circuit protection.

72)If the A.C. line current in a generator is doubled, the heating effect in the stator windings will be :

a)4 times

b)Same

c)Half

d)Twice

73)When a large motor load suddenly is disconnected from the switchboard and the genarator is AVR  controlled,  the  voltage will:

a)Initially fall, then reset to the set value.

b)Initially rise, then reset to the set value

c)Remain approximately constant, due to governor action.

d)Remain approximately constant, due to AVR action

74)Unloading a generator, it is necessary to gradually decrease the load in order to avoid:

a)Undue overload on the switchboard.

b)Undue overcurrent

c)Undue overspeeding.

d)Undue temperature rise.

75)The pair of instruments necessary for generator synchronising  are:

a)Voltmeter and synchroscope

b)kW meter and frequency meter

c)Amp-meter and volt-meter

d)Synchroscope and kVa-meter

76)Prior to synchronising, the generator voltage and frequency are respectively controlled by:

a)Speed governor and load power factor

b)Synchroscope and speed governor

c)Voltmeter and frequency meter

d)AVR and speed governor

77)For ideal synchronising, the phase angle difference between the incomer e.m.f. and the busbar voltage should be:

a)0°

b)30° behind

c)90° lag

d)30° ahead

78)During synchronising, the incoming generator should be running slightly "fast" compared to the busbar frequency.This is to ensure that the:

a)Incomers reverse power trip is tested

b)Incomer picks up as a motor

c)Most rapid synchronising action is achieved

d)Incomer picks up as a generator

79)The correct time to synchronise is usually taken to be when the synchroscope reaches the "5 to 12" position. This to allow for:

a)Synchroscope pointer time lag

b)Circuit breaker operating time

c)Synchroscope error

d)Generator phase difference error

80)Generator 1 and 2  are working in parallel. Prime-mover 2 suffers a total fuel loss. The likely outcome is:

a)No.2 generator trips on reverse power

b)Generator set 1 trips on reverse speed

c)No.1 machine overloads and trips out on overspeed

d)No.1 machine overspeeds and trips out on overload

81) You have just syncronized a second alternator onto the main switchboard, and want to equally share the load between the "on" and incoming alternators. What would you do first?

a)Adjust voltage rheostat for the incoming alternator on the front of the switchboard

b)Lower the governor speed controller of the incoming alternator and increase the governor speed controller of the alternator already on the switchboard

c)Trip the circuit breaker of the incoming alternator and check the voltage and speed adjustments before trying again

d)Raise the governor speed controller of the incoming alternator and reduce the governor speed controller of the alternator already on the switchboard

82) Advantage of Ni Cad battery

a)no need to top up

b)no damage due to short circuit

c)no corrosive/ explosive vapours

d)all above

83) At which point do you engage the main circuit breaker of the incoming alternator when paralleling two alternators?

a)With the pointer of the synchronoscope rotating fast and both synchronizing lamps flashing on and off

b)In none of the mentioned alternatives

c)With the pointer of the synchronoscope at 0° (12 O'clock) and both synchronizing lamps dark (off)

d)With the pointer of the synchronizer stopped at any position and both synchronizing lamps bright (on)

84) With no.1 and no.2 alternators running in parallel and the kW loads equally shared, one alternator is drawing much higher current than the other. What does this indicate?

a)Alternator frequencies are different and should be adjusted on the governor speed controllers

b)Alternators are out of phase and should be tripped and paralleled again

c)One alternator has lost one of its phases

d)The alternators are not generating the same voltages and should be adjusted on automatic voltage regulator rheostats

85) With two alternators running in parallel, you wish to stop one. The first step is to:

a)Remove the load from the alternator to be stopped

b)Make sure the load is evenly shared

c)Trip the main circuit breaker

d)Increase the frequency on the switchboard

86) You are paralleling two alternators and the pointer of the synchronoscope slowly stops rotating and remains stopped in one position before the circuit breaker is closed. This would indicate:

a)The frequency of the incoming alternator is the same as that of the main switchboard

b)The synchronoscope is not functioning properly and should be checked

c)The voltage of the incoming alternator is the same as that of the main switchboard

d)The incoming alternator is in phase with the switchboard, but the frequency is not the same

87) A 450 volt, 859 kW rated generator has not been in operation for several weeks. Prior to starting, insulation resistance readings are taken. The minimum acceptable insulation resistance reading on the main stator winding to allow you to proceed with running the generator is:

a)10 000 000  Ohms

b)10 0000  Ohms

c)10 000 Ohms

d)10 00  Ohms

88) On regular inspections of alternator windings it is found that windings are always covered with a heavy oil film coming from the atmosphere surrounding the auxiliary engine. After cleaning with an approved solvent, what do you do?

a)Take no additional action

b)Blank off intake air filters

c)Reinsulate the windings after each cleaning

d)Improve material of intake air filters

89) On routine daily inspection you notice that there is a light arching between an alternator's carbon brushes and rotor sliprings, with alternator operating at 70% load. Should you:

a)Increase the tension on the brushes

b)Reverse the polarity of the excitation voltage at the brush holder connection

c)Move the position of the brushes around the sliprings to find the correct neutral position

d)Check the surface of the sliprings, polish if necessary and bed in the brushes

90) What is the purpose of the alternator reverse power trip?

a)To prevent parallel operation if the excitation field voltage is reversed

b)To prevent the alternator from being paralleled if it is out of phase with the main c)switchboard

d)To prevent the alternator from "motoring" by being supplied  power from other parallel alternator

91) If you alter the field excitation voltage of one alternator operating in parallel, this will cause change in that alternators:

a)Reactive load (kVAR)

b)Frequency

c)None of the mentioned alternatives

d)Active load (kW)

92) The automatic voltage regulator is used to control the output voltage of the alternator at varying load conditions by:

a)Varying the excitation field strength by regulating excitation voltage/current

b)Regulating the voltage signal to the engine governor to regulate the speed to the desired load condition

c)Supplying variable current to compounding and no load transformers in the alternator stator winding circuit

d)all of the mentioned alternatives

93) The power requirements for the excitation winding/circuit for a 3-phase alternator operating at rated output power are supplied by:

a)Independent battery supply

b)Independent power supply and rectifier unit

c)The main switchboard via a three phase rectifier

d)The alternators output itself via the automatic voltage regulator

94) A three phase alternator is connected singularily to the main switchboard. The switchboard instruments show 440 Volts/950 amperes. With a power factor of 0.8 what will be the kW load?

a)215.9 KW

b)418 KW

c)334.4 KW

d)579.2 Kw

95) Before taking insulation resistance readings of generator windings the automatic voltage regulators should be isolated and all semiconductor short circuited or disconnected in order to:

a)Prevent charging of capacitive components within the automatic voltage regulator causing false regulation when generator restarts

b)Prevent operation of automatic voltage regulator during insulation testing

c)Prevent damage to sensitive electronic components from high voltage tester

d)Protect insulation resistance tester from being damaged

96) Following circuits are NOT used in digital computers

a)AND gate

b)NOT gate

c)IF gate

d)OR gate

97) megger readings versus temperature – 1 mega ohm at 75 deg c is equivalent to how much at 25 deg c.

a)1 mega ohm -- no change

b)30 mega ohms

c)1.2 mega ohms

d)0.7 mega ohms

98)the black terminal probe of the multimeter is

a)positive terminal

b)negative terminal

c)common terminal

d)earth terminal

99) a star delta starter

a)used for large motors like bow thruster

b)starting torque and starting current reduced to 1/3

c)long starting time

d)all above

100)direct on line starter

a)less time taken

b)can be started at full load

c)starting current is 7 times more than full load current

d)all above

CAPT AJIT VADAKAYIL ( 29 YEARS IN COMMAND )

 

ANSWERS:

1B
2D

3C
4C

5B
6C
7B
8C
9B
10B
11D
12D
13D
14B
15C
16D
17A
18C
19A
20B
21B
22C
23D
24B
25B
26D
27A
28D
29A
30B
31D
32D
33B
34C
35D
36A
37C
38D
39B
40C
41B
42B
43A
44B
45C
46B
47C
48A
49C
50C
51A
52B
53B
54A
55D
56B
57B
58C
59B
60D
61B
62B
63D
64D
65A
66D
67C
68C
69A
70D
71C
72A
73B
74C
75A
76D
77A
78D
79B
80A
81D
82D
83C
84D
85A
86A
87A
88D
89D
90D
91A
92A
93D
94D
95C
96C
97B
98C
99D
100D