Armature reaction in the alternator primarily affects terminal voltage per phase.
Armature reaction refers to the effect of the magnetic field produced by the stator windings on the magnetic field produced by the rotor windings in an alternator.
When the rotor rotates, it generates a magnetic field that passes through the stator windings, inducing a voltage in the stator windings.
The magnetic field produced by the stator windings also interacts with the magnetic field produced by the rotor windings, which can cause a distortion in the magnetic field and the resulting voltage output.
This distortion in the magnetic field due to the armature reaction can cause a reduction in the terminal voltage per phase of the alternator.
The extent of this reduction depends on various factors, such as the magnitude and direction of the load current, the position of the rotor with respect to the stator windings, and the excitation current of the rotor.
To compensate for the effect of armature reaction and maintain a stable voltage output, the alternator is designed with various measures, such as brushless excitation systems, static compensators, and voltage regulators.
These measures help to control the excitation current of the rotor and the voltage output of the alternator, ensuring a stable and reliable power supply.