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Consider the following statements: The armature reaction mmf in a dc machine is: 1. Stationery with respect to the field 2. Rotating with respect to the field poles 3. Rotating with respect to the armature Which of these statements are correct?

Consider the following statements: The armature reaction mmf in a dc machine is: 1. Stationery with respect to the field 2. Rotating with respect to the field poles 3. Rotating with respect to the armature Which of these statements are correct? Correct Answer 1 and 3 only

Armature reaction:

The effect of armature flux (ϕa) on main field flux (ϕm) is called armature reaction.

The armature reaction mmf produces two undesirable effects on the main field flux and these are

(1) Net reduction in the main field flux per pole

(2) Distortion of the main field flux wave along the air gap periphery.

The armature mmf in a dc machine is stationary with respect to field poles but rotating with respect to armature.

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