If a shunt motor is started with its field winding open then___________?
Correct answer: C. It will rotate at dangerously high speed
- A. It will rotate at the same speed as that with its field winding closed
- B. It will rotate at less speed as that with its field winding closed
- C. It will rotate at dangerously high speed
- D. None of these
Explanation
With the shunt field open, only weak residual magnetism remains, so the motor can accelerate to an excessively high and unsafe speed. This is why a field-failure relay is used for protection.
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