Armature reaction is the effect of armature flux on the main field flux. The effects of armature reaction are follows.
a. Armature reaction destroys (cross magnetizes) and weakens the main field flux produced by the main pole.
b. It causes to reduce the induced emf in the armature.
c. It causes to reduce the efficiency of machine.
d. It causes to produce sparking at the brushes due to the shifting of M.N.A (magnetic neutral axis).
e. At short-circuited loads or at very heavy loads, in case of self-excited generators de-magnetising of pole cores (wiping of residual magnetism) may takes place.
