In D.C. machines fractional pitch winding is used__________?
Correct answer: D. to reduce the sparking
- A. to improve cooling
- B. to reduce copper losses
- C. to increase the generated e.m.f.
- D. to reduce the sparking
Explanation
Fractional-pitch coils reduce the e.m.f. induced in a coil during commutation, making current reversal easier and reducing sparking at the brushes. They are not used to increase generated e.m.f., since short-pitching slightly reduces it.
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