Synchronous Motors MCQ Test - Set 06 - ObjectiveBooks

# Practice Test: Question Set - 06

1. A synchronous machine with large air gap has
(A) A higher value of stability limit
(B) A small value of inherent regulation
(C) A higher synchronizing power which makes the machine less sensitive to load variations
(D) All of the above

2. If in a synchronous motor, driving mechanical load and drawing current at lagging power factor from constant voltage supply, its field excitation is increased, then its power factor
(A) Become more
(B) Become less
(C) Remain constant
(D) None of the above

3. If one-phase of a 3-phase synchronous motor is short-circuited, motor
(A) Will refuse to start
(B) Will overheat in spots
(C) Will not come up to speed
(D) Will fail to pull into step

4. A 3-phase synchronous motor is running clockwise. If the direction of its field current is reversed
(A) The motor will stop
(B) The motor continue to run in the same direction
(C) The winding of the motor will burn
(D) The motor will run in the reverse direction

5. The back e.m.f. in the stator of a synchronous motor depends on
(A) Number of poles
(B) Flux density
(C) Rotor speed
(D) Rotor excitation

6. If the field winding of an unloaded salient pole synchronous motor is open circuited, the motor will
(A) Stop
(B) Run as induction motor
(C) Function as static condenser
(D) Burn with dense smoke

7. A synchronous motor which works on a leading power factor and does not drive a mechanical load is called as
(A) Static condenser
(B) Condenser
(C) Synchronous condenser
(D) None of the above

8. A pony motor is basically a
(A) Small induction motor
(B) D.C. series motor
(C) D.C. shunt motor
(D) Double winding A.C./D.C. motor

9. Mostly, synchronous motors are of
(A) Alternator type machines
(B) Induction type machines
(C) Salient pole type machines
(D) Smooth cylindrical type machines

10. In a synchronous motor which loss varies with load?
(A) Windage loss
(B) Bearing friction loss
(C) Copper loss
(D) Core loss

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