Results
Q1. An alternator is:
Correct answer is – an AC generator
Q2. To prevent high circulating currents between paralleled alternators, the following conditions should be met:
Correct answer is – their voltage, frequency, phase and phase sequence must all be the same
Q3. The output of an AC generator is taken from:
Correct answer is – the stator windings
Q4. The moving part of an alternator is:
Correct answer is – the rotor
Q5. A frequency wild alternator must be:
Correct answer is – unparalleled
Q6. In a 3 phase AC generator circuit, the phase voltage is:
Correct answer is – less than line voltage
Q7. If an alternator output is frequency wild, it would normally be used for:
Correct answer is – prop and engine de-icing systems
Q8. The generator output voltage is increased by:
Correct answer is – increasing the generator field current
Q9. A constant frequency AC supply in an aircraft with only frequency wild generators is provided by:
Correct answer is – an inverter
Q10. An alternator normally used to supply an aircraft’s power system would be:
Correct answer is – three phase
Q11. A permanent magnet in a rotating field generator:
Correct answer is – provides for initial excitation of the field
Q12. Voltage control of an alternator output is achieved by varying the:
Correct answer is – excitation of the rotating field
Q13. Frequency wild AC is produced when:
Correct answer is – the rotational speed of the generator varies
Q14. In a star connected supply system:
Correct answer is – line and phase current are equal
Q15. In a 3 phase supply system, line voltage would be sensed between the:
Correct answer is – phases only
Q16. One advantage of three phase generation over single phase generation is that:
Correct answer is – it gives more compact generators and allows lower cable weights
Q17. In a typical aircraft constant frequency supply system, the phase voltage is:
Correct answer is – 115
Q18. An alternator with its output taken from its stationary armature, has:
Correct answer is – a rotating field
Q19. The phase voltage in a star wound three phase system is measured between:
Correct answer is – phase and neutral
Q20. If one phase of a star wound three phase system becomes earthed, it will:
Correct answer is – cause a large current to flow in the neutral
Q21. The alternators fitted in an aircraft’s main power supply system would normally be:
Correct answer is – self-excited
Q22. A voltage regulator works by:
Correct answer is – varying the rotating field strength
Q23. To ensure correct load sharing on paralleled alternators:
Correct answer is – both real and reactive loads should be balanced
Q24. Reactive load sharing is achieved by:
Correct answer is – varying the generator field current
Q25. Real load sharing is achieved by:
Correct answer is – varying the alternator rotational speed
Q26. The phase relationship of paralleled generators should be:
Correct answer is – synchronous
Q27. In a constant speed parallel operation alternator system:
Correct answer is – each alternator has its own constant speed drive unit
Q28. An aircraft’s constant frequency supply is maintained at:
Correct answer is – between 380 – 420 Hz
Q29. For a modern aircraft powered by an AC system, the ground power unit must supply:
Correct answer is – 115/200 volts, three phase, 400 Hz
Q30. Oil for the operation of a CSDU is:
Correct answer is – a separate self-contained supply
Q31. Malfunction of a CSDU requires:
Correct answer is – operation of the drive disconnect switch at any time in flight
Q32. Before two constant frequency AC generators can be connected in parallel:
Correct answer is – their frequency, phase, phase sequence and voltage must match, and a means of automatic real and reactive load sharing must be available
Q33. The generator control relay (GCR) is:
Correct answer is – in the excitation circuit
Q34. The running excitation current for an alternator is:
Correct answer is – DC which is rectified AC and could be from a separate excitation generator on the main rotor shaft
Q35. 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:
Correct answer is – 200 volts AC
Q36. Protection from ‘earth’ faults and ‘line to line’ faults is given by:
Correct answer is – a fault protection system including a differential protection monitor
Q37. Warnings of CSDU oil overheat are given in the cockpit by:
Correct answer is – an ‘oil overheat’ warning light
Q38. One disadvantage of parallel operation is that:
Correct answer is – there is a considerable increase in complexity compared with a non-paralleled system, due to the need for CSDUs and load sharing circuits
Q39. Alternators in parallel operation require the maintenance of constant frequency and phase synchronization to:
Correct answer is – prevent recirculating currents
Q40. The APU generator can only be used when:
Correct answer is – when no other power source is feeding the bus bar
Q41. The purpose of the differential protection circuit in a three phase AC system is:
Correct answer is – to compare alternator output current to bus bar current
Q42. An alternator driven by a CSDU
Correct answer is – will require a voltage controller
Q43. In the event of a mechanical malfunction of the alternator:
Correct answer is – the quill drive will fracture
Q44. The load meter, upon selection to “kVAR” would indicate:
Correct answer is – reactive loads
Q45. Disconnection of the CSDU in flight would be advisable if:
Correct answer is – the oil temperature was high or the oil pressure was low
Q46. To increase the real load taken by a paralleled AC generator, the:
Correct answer is – generator drive torque is increased
Q47. Load sharing circuits are necessary whenever:
Correct answer is – generators are operating in parallel
Q48. Paralleled alternators will have:
Correct answer is – one load meter for each alternator
Q49. Frequency controlled generators are:
Correct answer is – not always paralleled
Q50. If the CSDU drive disconnect unit has been used, the drive can:
Correct answer is – only be reconnected when the aircraft is on the ground
Q51. When selected to ‘kW’, the alternator load meter will indicate the:
Correct answer is – real load
Q52. An AC generator’s IDU oil system:
Correct answer is – is self-contained
Q53. An alternator driven by a non-integrated constant speed drive unit, has windings that are cooled by:
Correct answer is – air
Q54. The load in a paralleled AC system is measured in:
Correct answer is – kW & KVAR
Q55. Paralleled generators must share real and reactive loads:
Correct answer is – to prevent large flows of current from one generator to another
Q56. One advantage of running alternators in parallel is that:
Correct answer is – a large capacity is available to absorb heavy transient loads when switching of heavy currents occurs
Q57. When an external AC supply is feeding the bus bars:
Correct answer is – the aircraft generators are taken off line
Q58. A three phase AC system can be used to supply:
Correct answer is – both one or three phase equipment
Q59. In a frequency wild generation system:
Correct answer is – generators can never be run in parallel, but after rectification, the DC can be fed to a common bus bar to provide a redundancy of supply
Q60. A fault on one phase of a three phase AC star connected system would:
Correct answer is – affect all three phases
Q61. The purpose of an inverter is:
Correct answer is – to change DC into AC
Q62. A low reactive load on one generator is compensated for by:
Correct answer is – altering the excitation current flowing in its field circuit
Q63. In the event of a mechanical failure occurring in the generator, the CSDU is protected by:
Correct answer is – a quill drive
Q64. To increase the real load which is being taken by a paralleled alternator:
Correct answer is – its drive torque is increased
Q65. An earth fault on a bus bar of a parallel generator system:
Correct answer is – would require that both the appropriate GCB and BTB should open
