Electrical Machines
Torque angle of a synchorous machine operating from a constant voltage bus is usually defined as the space angle between

 Rotor mmf wave and resultant flux density wave.
 Stator mmf wave and resultant mmf wave.
  Rotor mmf wave and stator mmf wave.
 Stator mmf wave and resultant flux density.

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

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

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

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