Electrical Machines
In a dc machine, the demagnetizing effect of armature reaction is due to

 non-sinusoidal nature of armature mmf
 magnetic saturation in half of the field pole
 component of armature mmf along field axis
 uneven air-gap length

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

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