Electrical Machines
The coil spam

 none of above.
 can never be equal to pole pitch.
  may or may not be exactly equal to people pitch.
 must be exactly equal to people pitch.

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Electrical Machines
Which of the following factors improve commutation in a dc machine ? 1. High contact resistance of brushes 2. High inductance of the coils undergoing commutation 3. Shifting of brushes in the direction of rotation for a generator and in the opposite direction For a motor 4. Narrow width for the commutation bars Select the correct answer using the codes given below : Codes :

 1 and 3
 1, 2 and 4
 1, 2, and 3
 2, 3 and 4

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