Electrical Machines
The stator frame in an induction motor is used to

  hold armature stamping in position.
  provide return path for the flux.
  protect the whole machine.
  ventilate the armature.

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Electrical Machines
Cogging and crawling are phenomena associated with

 any of the above.
 the former at a fraction of its rate speed and the latter during starting.
 the former during starting and the latter at a fraction of its rated speed.
 cage induction machines and they are essentially the same.

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Electrical Machines
Consider the following statements about commutating poles which are fitted on most large dc Shunt motors: 1. The commutating poles are placed in the geometric neutral plane and their number is usually Equal to the number of main poles 2. The winding on the commutating poles is connected in series with the shunt-field winding on the main poles 3. The polarity of the commutating pole must be that of the next pole further ahead 4. The commutating poles neutralize the reactance voltage produced in the coil undergoing Commutation. Of these statements,

 2, 3 and 4 are correct
 1, 2 and 3 are correct
 1, 2 and 4 are correct
 1 and 4 are correct

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