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Increase in flux density at one end of the pole is less than the decrease at the other end. This is called as ____________

(a) Demagnetizing mmf

(b) Cross-magnetizing mmf

(c) Anti-magnetizing mmf

(d) Magnetizing mmf

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The origin of the question is Armature Reaction -1 in division Armature Reaction of DC Machines

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Best answer
The correct choice is (a) Demagnetizing mmf

The explanation: If the main pole excitation is such that iron is in the saturated region of magnetization (this is the case in a practical machine), the increase in flux density at one end of the poles caused by armature reaction is less than the decrease at the other end, so that there is a net reduction in the flux/pole, a demagnetizing effect.

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