Top 10 Synchronous Motor MCQs

1. The correct statement about the speed of synchronous motor:

1. It remains the same from no load to full load
2. It starts decreasing and becomes zero at full load
3. It starts increasing and bursts at full load
4. It has divergent behavior

Correct answer: 1.

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2. Hunting in synchronous motor can arise due to:

1. Change in excitation
2. Change in speed
3. Any change in system powering the motor
4. Any of above

Correct answer: 4.

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3. Which of the following terms can correctly explain the synchrnous motor:

1. Single fed
2. Single PF
3. Constant speed motor
4. None of above

Correct answer: 3

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4. The V curve in a synchronous motor illustrates relation between:

1. Armature current and Voltage
2. Field current and voltage
3. Armature current and Field current
4. Field Current and Armature voltage

Correct answer: 3

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5. A synchronous motor for power factor correction operates at:

1. No load and under excited
2. No load and over excited
3. Full load and under excited
4. Full load and over excited

Correct answer: 2

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6. The foremost reason for employing amortissuer windings is:

1. Reduce losses
2. Improve power factor
3. Start motor
4. Increase haunting

Correct answer: 3

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8. A 50 Hz salient pole motor having 30 poles turns at:

1. 100 r.p.m
2. 200 r.p.m
3. 300 r.p.m
4. 350 r.p.m

Correct answer: 2

Speed = (120 * f)/P = 120*50/30 = 200 r.p.m

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9. The condition at which synchronous motor tends to be cheaper then induction motor:

1. High speed, High efficiency
2. High speed, Low efficiency
3. Low speed, High efficiency
4. None of above

Correct answer: 3

At low speeds, the induction motor are costly and have low power factor as well as efficiency

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10. The number of poles on a 60 Hz synchronous motor turning at 200 rpm is:

1. 16
2. 30
3. 32
4. 36

Correct answer: 4

Number of poles = (120 * 60 Hz) / 200 = 36