In an alternator, the effect of armature reaction is minimum at the power factor of
In an alternator, the effect of armature reaction is minimum at the power factor of Unity.
This is because at the unity power factor, the armature current is in phase with the terminal voltage, and the flux produced by the armature current is perpendicular to the flux produced by the field winding.
As a result, the net effect of the armature reaction on the main field is minimal, and the alternator operates with minimum distortion in the voltage waveform and minimum loss of terminal voltage.
At other power factors, the armature reaction can cause voltage drop, distortion in the waveform, and other performance issues, which need to be compensated for by various methods such as field weakening, automatic voltage regulators (AVRs), and other control techniques.