Practice Test: Question Set - 11
1. When the excitation of an unloaded salient pole synchronous motor suddenly gets disconnected
- (A) The motor stops
- (B) It runs as a reluctance motor at the same
speed
- (C) It runs as a reluctance motor at a lower
speed
- (D) None of the above
2. Synchronous motor always runs at
- (A) The synchronous speed
- (B) Less than synchronous speed
- (C) More than synchronous speed
- (D) None of the above
3. An overexcited synchronous motor takes
- (A) Leading current
- (B) Lagging current
- (C) Both (A) and (B)
- (D) None of the above
4. For V-curves for a synchronous motor the graph is drawn between
- (A) Field current and armature current
- (B) Terminal voltage and load factor
- (C) Power factor and field current
- (D) Armature current and power factor
5. When the field of a synchronous motor is under-excited, the power factor will be
- (A) Leading
- (B) Lagging
- (C) Unity
- (D) Zero
6. The percentage slip in case of a synchronous motor is
- (A) 1 %
- (B) 100 %
- (C) 0.5 %
- (D) Zero
7. The maximum power developed in a synchronous motor occurs at a coupling angle of
- (A) 30°
- (B) 60°
- (C) 90°
- (D) 180°
8. The standard full-load power factor ratings for synchronous motors are
- (A) Zero or 0.8 leading
- (B) Unity or 0.8 lagging
- (C) Unity or 0.8 leading
- (D) Unity or zero
9. Slip rings are usually made of
- (A) Carbon or graphite
- (B) Brass or steel
- (C) Silver or gold
- (D) Copper or aluminium
10. Slip-rings in a synchronous motor carry
- (A) Direct current
- (B) Alternating current
- (C) No current
- (D) All of the above
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