What is meant by Armature reaction?

1.	What is meant by Armature reaction?
Answer» The effect of armature flux on the main field flux is called Armature reaction, where armature flux weakens the main field flux. In Alternator, power factor contributes more importance in Armature reaction. a) In Unity, power factor field strength is average and effect is distortion. So voltage variation will not be too much. b) In lagging, power factor armature flux is directly opposite to the main field flux. That is armature flux is lagging 90ο by main field flux. So the result is demagnetizing the field. Due to less field flux, less voltage at the alternator terminals and excitation required is more. c) In leading, power factor armature flux is leading by 90ο to the main field flux. The result is additive and main field strength is more and excitation has to be reduced. Otherwise, end parts or overhang portion of the generator will heat.

Answer»

The effect of armature flux on the main field flux is called Armature reaction, where armature flux weakens the main field flux. In Alternator, power factor contributes more importance in Armature reaction.

a) In Unity, power factor field strength is average and effect is distortion. So voltage variation will not be too much.

b) In lagging, power factor armature flux is directly opposite to the main field flux. That is armature flux is lagging 90ο by main field flux. So the result is demagnetizing the field. Due to less field flux, less voltage at the alternator terminals and excitation required is more.

c) In leading, power factor armature flux is leading by 90ο to the main field flux. The result is additive and main field strength is more and excitation has to be reduced. Otherwise, end parts or overhang portion of the generator will heat.

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