What mean over excitation motor

Question

what value of excitation motor

Answer 1

Excitation is the DC current applied to the rotor of a synchronous machine to produce the magnetic field.

Over exciting causes the machine to run at a less lagging power factor. Some machines can be over excited to the point that they have a leading power factor.

The reason for doing this, and, the reason for having the synchronous motor is for correcting the overall power factor of the facility.

Since synchronous motors tend to be more expensive, power factor correction capacitors are used more these days.

When over exciting the rotor, you must be careful not to exceed the current rating of either rotor or stator. Not all motors will actually go leading power factor as the coils become saturated first.

Answer 2

This refers to the DC current passing through the armature of a synchronous machine. If under excited (current too low) then the stator has lagging current. If over excited (current too high), leading current. Over excitation is sometimnes used instead of capacitors to provide VARS.