A synchronous motor can develop synchronous torque:
Correct answer: C. only at synchronous speed
- A. when under loaded
- B. while over-excited
- C. only at synchronous speed
- D. below or above synchronous speed
Explanation
Synchronous torque is produced when the rotor is locked magnetically with the rotating stator field, which occurs at synchronous speed. Below that speed the motor is accelerating, while above it the rotor cannot remain in synchronism.
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