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

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

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Electrical Machines
The introduction of interpoles in between the main poles improves the performance of a dc machine, because

 the inequality of air-gap flux on the top and bottom halves of the armature is removed
 a counter-emf is induced in the coil undergoing commutation
 the interpoles produce additional flux to augment the developed torque
 the flux waveform is improved with reduction in harmonics

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Electrical Machines
In a DC machine

 current and emf in armature are alternating.
 current and emf at the terminals are alternating.
 current and emf in armature are unidirectional
 emf in armature conductors and at the terminals is alternating.

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