What happens if excitation fails in alternator?

When the excitation fails the power delivering capacity of machine suddenly reduces. So the mechanical power input is greater than electrical power output. This imbalance will accelerate the rotor and force it to run above synchronous speed.

What happens if generator loses its excitation?

When a generator loses its excitation, the rotor current decreases gradually and the field voltage slowly decays as dictated by the field time constant. As a final outcome, the generator starts to consume reactive power from the power system instead of supplying it.

What happens if one of the alternators of which excitation is changed?

If the excitation is changed, it will change the field magnetism created inside the alternator and the voltage generated in the stator winding is likely to be affected.

What is loss of excitation protection?

Loss of excitation protection is used to protect the synchronous machine (alternator or generator) acts as induction motor when the excitation fails. Loss of field or loss of excitation results in loss of synchronism between rotor flux & stator flux (the generator still in online with the grid).

What causes loss of excitation?

Loss of excitation is a very common fault in synchronous machine operating and can be caused by short circuit of the field winding, unexpected field breaker open or loss-of-excitation relay mal-operation.

How does change in excitation affects the voltage regulation of alternator?

As the load on the generator is increased, an increase in current flow causes the voltage to drop. The excitation system senses this decrease in voltage and increases the strength of the magnetic field to return the voltage to the desired level.

Does alternator need excitation?

Originally Answered: Why does an alternator need excitation? The field windings on the rotor (shaft) of an alternator need to be energized (creating field excitation) in order to create a magnetic field to induce voltage when passed through the conductors of the alternator’s armature.

What is the importance of using exciter in an alternator?

The main purpose of exciter in a generator(alternator) is to provide stationary rotating magnetic field. Which is used to induce the e.m.f in the armature coil. So, DC power is given to exciter and the exciter is nothing but a coil, and the exciter creates a magnetic field.

Which protection scheme is employed against loss of excitation of an alternator?

Loss of excitation protection is used to protect the synchronous machine (alternator or generator) acts as induction motor when the excitation fails. Loss excitation protection operates under many circumstances such as diode failure, rotor winding short circuit, AVR failure, etc.

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