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Objective questions and answers or MCQ of Electrical Machines page-22


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341. For which of the following alternators, the distribution factor will be 0.96?

a) Three phase alternator, 4 pole wound on 72 slots core
b) Three phase alternator, 8 pole wound on 80 slots core
c) Three phase alternator, 8 pole wound on 72 slots core
d) Three phase alternator, 6 pole wound on 72 slots core

Ans: (c)

342. Which of the synchronous alternators will complete 1080 electrical degrees in one revolution?

a) 8 pole synchronous alternator
b) 6 pole synchronous alternator
c) 4 pole synchronous alternator
d) 10 pole synchronous alternator

Ans: (b)

343. How many cycles of alternating current will be generated in one revolution of 8 pole synchronous alternator?

a) 10 cycles
b) 4 cycles
c) 8 cycles
d) 16 cycles

Ans: (b)

344. How many poles will be required if an alternator runs at 1500 rpm and given frequency of 50 Hz?

a) 8 pole
b) 6 pole
c) 4 pole
d) 2 pole

Ans: (c)

345. Two generators are running in parallel. One of the generator may run as motor for following reasons?

a) The speed of that generator is increased
b) The direction that generator is reversed
c) The generator takes large share of loads
d) The field of that generator is weakened

Ans: (c)

346. Which of the following statements is correct?

a) A single phase induction motor has very high starting torque.
b) A single phase induction motor has zero starting torque.
c) A single phase starting torque is as good as that of 3 phase induction motor.
d) A single phase motor has very small torque but greater than zero.

Ans: (b)

347. The primary applied voltage in an ideal transformer on no load is balanced by

a) Primary induced emf
b) Secondary induced emf
c) Secondary voltage
d) Core and copper losses

Ans: (b)

348. The air cores in transformers are preferred for

a) Low frequency transformers
b) High frequency transformers
c) 5 kVA, 50 Hz transformers
d) None of these

Ans: (b)

349. The synchronous motor can be made self starting by providing.

a) Damper winding on rotor poles
b) Damper winding on stator
c) (a) or (b)
d) None of the above

Ans: (a)

350. The amplidyne is

a) Fully compensated cross field machine
b) Half compensated cross field machine
c) Over-compensated cross field machine
d) Under-compensated cross field machine

Ans: (a)


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