ALTERNATOR – Air – DGCA Question Bank For Politics

#1. An alternator is:

a reversing input switch.

an AC generator.

a DC generator.

a static inverter.

#2. AC generators usually have a rotating field and a fixed armature to:

reduce the overall diameter of the of the generator.

allow the output to be taken from the stator.

reduce the weight of the generator.

prevent arcing at the commutator.

#3. The output of an AC generator is taken from:

the field coils.

the exciter windings.

the stator windings.

the rotor coils.

#4. The moving part of an alternator is:

the rotor.

the megacycle.

the stator.

the frequency.

#5. A frequency wild alternator must be:

paralleled.

a rotating magnet type.

self exciting.

unparalleled.

#6. In a 3 phase AC generator circuit, the phase voltage is:

greater than line voltage.

10% higher than line voltage.

less than line voltage.

equal to line voltage.

#7. If an alternator output is frequency wild, it would normally be used for:

flight instruments.

charging a battery.

all AC equipment.

prop and engine de-icing systems.

#8. The generator output voltage is increased by:

putting more load on it.

the frequency controller.

decreasing the generator field voltage.

increasing the generator field current.

#9. A constant frequency AC supply in an aircraft with only frequency wild generators is provided by:

an inverter.

a diode.

an auto-transformer.

a rectifier.

#10. An alternator normally used to supply an aircrafts power system would be:

single phase.

three phase.

two phase.

frequency wild.

#11. A permanent magnet in a rotating field generator:

provides for initial excitation of the field.

controls the amount of excitation in the stator windings.

provides the initial excitation in the voltage regulator.

can be flashed by the application of alternating current.

#12. Voltage control of an alternator output is achieved by varying the:

excitation of the rotating commutator.

load current.

excitation of the rotating field.

power factor.

#13. Frequency wild AC is produced when:

a transformer winding open circuits.

the voltage regulator is malfunctioning.

the rotational speed of the generator varies.

the alternator becomes angry.

#14. In a star connected supply system:

line and phase current are equal.

line current is greater than phase current.

line current is less than phase current.

phase current is 0.707 times line current.

#15. In a 3 phase supply system, line voltage would be sensed between the:

phases only.

phase and earth.

phase and neutral.

phases and earth.

#16. One advantage of three phase generation over single phase generation is that:

most aircraft services require a three phase supply.

it can be more easily transformed into DC

it gives more compact generators and allows lower cable weights.

the power factor is much lower.

#17. In a typical aircraft constant frequency supply system, the phase voltage is:

200

115

208

400

#18. An alternator with its output taken from its stationary armature, has:

a stationary field.

its field excitation fed directly to the armature.

AC excitation.

a rotating field.

#19. The phase voltage in a star wound three phase system is measured between:

phase and neutral.

two phases.

two lines.

neutral and earth.

#20. If one phase of a star wound three phase system becomes earthed, it will:

earth all three phases.

cause a large current to flow in the neutral.

have no effect on the other phases.

cause a reduction in the frequency of the supply.

#21. The alternators fitted in an aircrafts main power supply system would normally be:

brushed self excited machines.

frequency wild.

self excited.

externally excited.

#22. A voltage regulator works by:

sensing the battery voltage.

assessing the impedance of the circuit.

varying the circuit voltage.

varying the rotating field strength.

#23. To ensure correct load sharing on paralleled alternators:

both real and reactive loads should be balanced.

actual loads should be the same.

reactive loads should be the same.

the load impedance should be constant.

#24. Reactive load sharing is achieved by:

altering the loads on the bus bars.

varying the generator rotational speed.

varying the generator field current.

altering the C.S.D.U. output torque.

#25. Real load sharing is achieved by:

varying the alternator rotational speed.

varying the generator field current.

altering the loads on the bus bar.

the voltage regulator.

#26. The phase relationship of paralleled generators should be ;-

unimportant.

180° apart.

synchronous.

120° apart.

#27. In a constant speed parallel operation alternator system:

each alternator has its own constant speed drive unit.

all engines are run at the same speed.

all alternators are driven by the same engine.

engine speed is governed by the constant speed drive unit.

#28. An aircrafts constant frequency supply is maintained at:

between 350 - 450 Hz.

between 380 - 420 Hz.

between 115 - 200 Hz.

between 395 - 495 Hz.

#29. For a modern aircraft powered by an AC system, the ground power unit must supply:

28 volts AC only.

200 volts.

115 volts, three phase.

200 volts, three phase, 400 Hz.

#30. Oil for the operation of a C.S.D.U. is:

supplied from the engine oil system.

a separate self contained supply.

drawn from a common tank for all C.S.D.U.s.

only required for lubrication purposes.

#31. Malfunction of a C.S.D.U. requires:

automatic electrical disconnection of the drive at any time in flight.

that the input drive will shear on the ground only.

operation of the drive disconnect switch at any time in flight.

operation of the drive disconnect switch on the ground only.

#32. Before two constant frequency AC generators can be connected in parallel:

their frequency, phase, phase sequence and voltage must match, and a means of automatic real and reactive load sharing must be available.

real and reactive loads must match. Frequency, phase and voltage must be within limits.

the synchronisation lights on the alternator control panel must be fully bright.

suitable control arrangements must exist for the sharing of real and reactive loads. these will correct any phase or frequency error existing at the time of connection.

#33. The generator control relay (G.C.R) is:

in the excitation circuit.

between the alternator and its load bus bar.

in the stator circuit.

between the load bus bar and the synchronous bus bar.

#34. The running excitation current for an alternator is:

AC

DC from the aircraft batteries.

DC from the static inverter.

DC which is rectified AC and could be from a separate excitation generator on the main rotor shaft.

#35. If each phase of a three phase star wound system has a phase voltage of 115 volts, the voltage obtained by bridging two phase would be:

200 volts AC

173 volts DC

28 volts DC

173 volts AC

#36. Protection from ‘earth’ faults and ‘line to line’ faults is given by:

a negative earth detector.

a fault protection system including a differential protection monitor.

the synchronisation unit.

reactive load sharing circuits.

#37. Warnings of C.S.D.U. oil overheat are given in the cockpit by:

audio warning.

an ‘oil overheat’ warning light.

a ‘low oil pressure’ warning light.

a temperature gauge.

#38. One disadvantage of parallel operation is that:

faults can propagate, and any error in supply can affect all services.

the system is less flexible due to the need for additional control and protection circuits.

the greater load on the C.S.D.U.s means that their power / weight ratio is much reduced.

there is a considerable increase in complexity compared with a non-paralleled system, due to the need for C.S.D.U.s and load sharing circuits.

#39. Alternators in parallel operation require the maintenance of constant frequency and phase synchronisation to:

balance the battery voltage when more than one battery is being used.

prevent recirculating currents.

control their voltage.

reduce their magnetic fields.

#40. The A.P.U. generator can only be used when:

another generator is on line.

the aircraft is on the ground.

the bus bars are being fed from another source.

when no other power source is feeding the bus bar.

#41. The purpose of the differential protection circuit in a three phase AC system is:

to compare alternator output current to bus bar current.

to compare on and off load currents.

to compare the alternators reactive load to its real load.

to compare the C.S.D.U. efficiency ratings.

#42. An alternator driven by a C.S.D.U:

can never be paralleled.

will require a voltage controller.

will require a lubrication system separated from its drive oil system.

will not require a voltage controller.

#43. In the event of a mechanical malfunction of the alternator:

the drive disconnect unit will automatically separate the C.S.D.U. from the alternator.

the real load will be adjusted to compensate.

the quill drive will fracture.

the C.S.D.U. oil temperature will decrease.

#44. The load meter, upon selection to “KVAR” would indicate:

total power available.

reactive loads.

active loads.

only DC resistive loads.

#45. Disconnection of the C.S.D.U. in flight would be advisable if:

the frequency meter indicated a discrepancy of greater than 5 Hz between alternators.

there was an over or under voltage.

the oil temperature was high or the oil pressure was low.

the engine failed.

#46. To increase the real load taken by a paralleled AC generator, the:

generator drive torque is increased.

generator excitation is increased.

generator drive torque and field excitation are increased.

generator voltage regulator adjusts the generator rotor torque.

#47. Load sharing circuits are necessary whenever:

generators are operating in series.

generators are operating independently.

the ground power and the A.P.U. are serving the bus bars together.

generators are operating in parallel.

#48. Paralleled alternators will have:

one load meter which measures total system load.

one voltmeter for each alternator.

one load meter for each alternator.

one meter which indicates both voltage and frequency.

#49. Frequency controlled generators are:

always paralleled.

not always paralleled.

never paralleled.

paralleled only when the DC is paralleled.

#50. If the C.S.D.U. drive disconnect unit had been used, the drive can:

only be reconnected when the aircraft is on the ground.

be reinstated in flight from the electrical supply department.

be reinstated in flight from the flight deck.

be reinstated when necessary by using the Ram Air Turbine.

#51. When selected to ‘kW’, the alternator load meter will indicate the:

total circuit load.

real load.

reactive load.

current flowing in the field.

#52. An AC generator’s I.D.U. oil system:

is self contained.

is common with the engine oil system.

is used only for cooling.

is used only for lubrication.

#53. An alternator driven by a non-integrated constant speed drive unit, has windings that are cooled by:

water.

oil.

oil and water.

air and/or oil.

#54. The load in a paralleled AC system is measured in:

KW & KVA.

KW & KV.

KV & KVAR.

KW & KVAR.

#55. Paralleled generators must share real and reactive loads:

to prevent large current flows through the T.R.U.s.

to prevent out of balance forces being fed through the C.S.D.U.s to the engines.

to prevent large flows of current from one generator to another.

to prevent harmonic frequencies being created in the synchronous bus bars.

#56. One advantage of running alternators in parallel is that:

the supply to all circuits is in phase.

a large capacity is available to absorb heavy transient loads when switching of heavy currents occurs.

the risk of overloading the system is reduced.

there is only a requirement for one C.S.D.U.

#57. When an external AC supply is feeding the bus bars:

the internal bus bars are disconnected.

the aircraft generators are run in parallel with the external supply.

the aircraft generators are taken off line.

the synchronising unit will ensure that no frequency difference exists between the aircraft generators and the external supply.

#58. A three phase AC system can be used to supply:

both one or three phase equipment.

only three phase equipment.

only single phase equipment.

only inductive or capacitive loads.

#59. In a frequency wild generation system:

generators can be run in parallel only when all engine r.p.m.s match.

generators can never be run in parallel and there can be no duplication of supply.

generators can never be run in parallel, but after rectification, the D,C, can be fed to a common bus bar to provide a redundancy of supply.

capacitive and inductive loads can be fed with no problems of overheating.

#60. A fault on one phase of a three phase AC star connected system would:

have no effect.

effect only the phase concerned.

cause inductive loads to overheat.

affect all three phases.

#61. The purpose of an inverter is:

to change AC into DC

to change the frequency of the AC supply.

to act as a back up for the alternator.

to change DC into AC

#62. A low reactive load on one generator is compensated for by:

altering the excitation current flowing in its field circuit.

increasing the rotor speed.

increasing the real load on the other generators.

overall load reduction.

#63. In the event of a mechanical failure occurring in the generator, the C.S.D.U. is protected by:

a hydraulic clutch.

a universal joint.

a quill drive.

a feather drive.

#64. To increase the real load which is being taken by a paralleled alternator:

the voltage regulator adjusts the generator rotor torque.

both its drive torque and its excitation are increased.

only its excitation is increased.

its drive torque is increased.

#65. An earth fault on a bus bar of a parallel generator system:

would require that the appropriate G.C.B. should open.

would require that the appropriate B.T.B. should open.

would require that both the appropriate G.C.B. and B.T.B. should open.

would require that all alternators should operate independently.

#66. To prevent high circulating currents between paralleled alternators, the following conditions should be met:

their voltage and frequency must be the same.

their frequencies must be identical and their phase sequence must be the same.

their voltage, frequency, phase and phase sequence must all be the same.

their inductive and capacitive reactances must match exactly.

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