Question

Armature reaction in a machine is demagnetizing due to _________

(a) Machine is designed with iron which is slightly saturated

(b) Machine is designed with iron which is unsaturated

(c) Depends on the application where machine is being is used

(d) Can’t tell

This question was posed to me in an interview for internship.

I want to ask this question from Armature Reaction in portion Armature Reaction of DC Machines

Answer 1

Correct choice is (a) Machine is designed with iron which is slightly saturated

For explanation I would say: The armature reaction in a DC machine is cross-magnetizing causing distortion in the flux density wave shape and a slight shift in MNA. It also causes demagnetization because a machine is normally designed with iron slightly saturated.