The injected e.m.f. in the rotor of induction motor must have__________?
Correct answer: B. the same frequency as the slip frequency
- A. zero frequency
- B. the same frequency as the slip frequency
- C. the same phase as the rotor e.m.f.
- D. high value for the satisfactory speed control
Explanation
The rotor e.m.f. exists at slip frequency, so an injected e.m.f. must have the same frequency to produce effective speed control. A zero-frequency or unrelated-frequency injection would not properly control the rotor current.
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