Synchronous Motor multiple Choice Questions and Answers - Set 11 - ObjectiveBooks

Synchronous Motor multiple Choice Questions and Answers - Set 11

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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