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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