Electrical Machines
The following statements relate to compensating winding (CW) and interpole winding (IW) of a dc machine : 1. CW neutralizes the armature reaction under a pole pitch 2. IW is connected in series with armature circuit 3. IW produces mmf in the commutating zone only 4. CWmmf is directed along the brush axis 5. Mmf produced by IW is equal to armature mmf From these, the correct statements are

 1, 3, 4, 5
 2, 3, 4, 5
 2, 3, 4
 1, 2, 3, 4 and 5

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Electrical Machines
Cogging of induction motor occurs at

 high voltage and when stator and rotor poles are equal.
 low voltage and when stator and rotor poles are equal.
 low voltage and when stator and rotor poles are not equal.
 high voltage and when stator and rotor poles are not equal.

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Electrical Machines
An ideal synchronous motor has no starting torque because

 rotor winding is highly reactive.
 relative velocity between the stator and rotor mmf’s is zero.
  relative velocity between stator and rotor mmf’s is not zero.
 rotor is made up of salient poles.

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Electrical Machines
The 3 - Φ induction motors are, by a very considerable margin, the most widely used AC motors as

  they have maximum efficiency and maximum starting torque.
  they are capable of operation under range of leading and lagging pf.
  these are cheaper in cost, simple and rugged in construction.
  they have very good speed regulation.

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