Electrical Machines
A small air gap in poly phase induction motor helps to

 reduce chance of cogging.
  reduce magnetizing current.
 increase starting torque.
 reduce chance of crawling.

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Electrical Machines
A dc shunt generator, when commissioned after a major repair of the field system, failed to build Up voltage. It was because

 field winding was wrongly connected
 there was a break in the armature circuit
 field resistance was higher than critical resistance
 field system lost residual magnetism

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