AC Generator Most Important MCQ

AC Generator 30 Most Important MCQ
Answer লেখা ইমেজে ক্লিক করলে উত্তর অপশন দেখাবে।

1) The frequency of alternator having 4-poles and rotating speed at 1500 rpm is — Hz
A. 50
B. 60
C. 120
D. 48

2) If an alternator winding has a fractional pitch of 5/6, the coil span is…..degrees.
A. 150
B. 180
C. 160
D. 320

3) A 50 Hz alternator will run at the greatest possible speed if it is wound for…..poles.
A. 4
B. 2
C. 8
D. 12

4) Armature reaction in an alternator primarily affects
A. generated voltage per phase
B. frequency of armature current
C. rotor speed
D. none of above

5) When speed change of an alternator is changed from 3600 rpm to 1800 rpm, the generated voltage/phase will become-
A. twice
B. one-half
C. one fourth
D. none of this options

6) Under no load condition , power drawn by the prime mover of an alternator goes to
A. produce power in armature
B. meet no-load losses
C. meet cu losses
D. meet induced emf in armature winding

7) As load power factor of an alternator becomes more leading , the value of generated voltage required to give rated terminal voltage–
A. increase
B. unchanged
C. Decrease
D. None of above

8) The power factor of an alternator is determined by its–
A. excitation
B. speed
C. load
D. frequency

9) At lagging load , armature reaction in an alternator is.
A. cross-magnetizing
B. demagnetizing
C. magnetizing
D. None of above.

10) Zero power factor method of an alternator is used to find its–
A. armature resistance
B. voltage regulation
C. efficiency
D. impedance

11) Two identical alternator are running in parallel and carry equal loads. If excitation of one alternator is increased without changing its fuel supply, then
A. it will keep supplying almost same load
B. its p.f will increase
C. KVA decrease
D. None of above.

12) Condition of parallel operation of alternator–
A. voltage rating same
B. frequency same
C. phase sequence same
D. All of these 3 options

13) At leading power factor, the armature flux in an alternator …..the rotor flux
A. opposes
B. Aids
C. does not effect
D. distorts

14) For a machine on infinite bus active power can be varied by–
A. changing field excitation
B. changing of prime mover speed
C. both option right
D. None of above

15) For proper parallel operation, a.c polyphase alternator must have the same–
A. Voltage rating
B. Speed
C. KVA Rating
D. Excitation

16) The load sharing between two steam driven alternator operating in parallel may be adjusted by varying the.
A. steam supply to ther prime mover
B. p.f of the alternator
C. field strength of the alternator
D. all of above

17) To determine the losses of an alternator is driven by
A. synchronous motor.
B. compensated DC motor.
C. calibrated DC motor.
D. AC series motor.

18) Which is alternator rating–
A. KVA
B. KW
C. HP
D. None of above

19) Which option is wrong for AC Generator?
A. emf/phase = 4.44φfT KpKd volt
B. N= 120f/P
C. %Vr = Vfl-Vnl/vnl X100
D. Wrong all of above

20) Can d.c generator converted into an alternator?
A. No
B. Yes

21) The winding of a 4-pole alternator having 36 slots and a coil span of 1 to 8 is short-pitched by ..degrees.
A. 140
B. 80
C. 20
D. 40

22) The harmonic which would be totally eliminated from the alternator e.m.f. using a fractional pitch of 4/5 is
A. 3rd
B. 7th
C. 5th
D. 9th

23) If, in an alternator, chording angle for fundamental flux wave is α, its value for 5th harmonic is
A. 5α
B. α/5
C. 25α
D. α/25.

24) The load sharing between two steam-driven alternators operating in parallel may be adjusted by varying the
A. field strengths of the alternators
B. power factors of the alternators
C. steam supply to their prime movers
D. None of above.

25) Keeping its excitation constant, if steam supply of an alternator running in parallel with another identical alternator is increased, then
A. it would over-run the other alternator
B. its rotor will fall back in phase with respect to the other machine
C. it will supply greater portion of the load
D. its power factor would be decreased.

26) A winding is having number of slots is equal to number of poles, then this winding is called
A. short pitch winding.
B. full pitch winding.
C. concentrated winding.
D. distributed winding.

27) Which alternator are more suitable for high-speed system?
A. Salient pole.
B. Non-salient pole.
C. Both A and B option
D. None of these.

28) The number of poles in turbo alternator are
A. 2.
B. 6.
C. 8.
D. 10.

29) The stationary alternator must not be connected to live bus bars because it will results –
A. short circuit.
B. open circuit.
C. nothing will happen.
D. floating.

30) Factors on which frequency of alternator depends upon
A. number of poles and synchronous speed.
B. number of poles and rotor speed.
C. synchronous speed.
D. independent of any factors.

** An electric generator, or dynamo, is a electrical machine which converts mechanical energy into electrical energy.

** AVR is an abbreviation for Automatic Voltage Regulator. It is important part in Synchronous Generators, it controls the output voltage of the generator by controlling its excitation current. Thus it can control the output Reactive Power of the Generator.

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