What is over excitation in generator?

The over-excitation limiter protects the generator against over-temperature caused by high field current for long time. Under-excitation limiter prevents the decrease of generator field current to the values lower than the stability margin or the thermal limit of end side of the stator core.

What is meant by over excitation?

: excited to an excessive degree overexcited children overexcited neurons an overexcited imagination “Oh, cool!” I said, maybe a little overexcited because I was trying to get him psyched up.— R. J. Palacio.

What is over excitation of synchronous generator?

Excitation of Synchronous Generator (Alternator): Lagging power factor: If field excitation is such that Eb > V the generator is said to be over-excited and it draw lagging current. So that it delivered reactive power.

What is over excitation in alternator?

An overexcited alternator always supplies lagging current to the connected load, which means that load is of lagging nature. Lagging load take active and reactive power from the supply or alternator. Therefore, reactive power flows outwards from an over-excited alternator.

What happens if excitation is changed?

A change in the excitation of an alternator running in parallel with other affects only its KVA output; it does not affect the KW output. A change in the excitation, thus, affects only the power factor of its output.

What is over excitation protection?

The overexcitation protection function is applied to protect generators and unit transformers against high flux values causing saturation of the iron cores and consequently high magnetizing currents.

What is over excitation in synchronous motor?

The synchronous motor is said to be over-excited if the field excitation is such that (Ef>V). Under such conditions, the armature current (Ia) leads the supply voltage (V) and the motor supplies lagging reactive power to the system.

What is the application of over excited synchronous generator?

Application. An over-excited synchronous motor has a leading power factor. This makes it useful for power-factor correction of industrial loads. Both transformers and induction motors draw lagging (magnetising) currents from the line.

Why is over fluxing harmful for the transformer?

Due to over fluxing in transformer its core becomes saturated as such induced voltage in the primary circuit becomes more or less constant. If the supply voltage to the primary is increased to abnormal high value, there must be high magnetising current in the primary circuit.

Why is excitation always DC?

Why only D.C is used for Excitation in Alternators? Excitation voltage or current is supplied to the field windings of a rotor to produce a static magnetic field. If we use alternating current instead of direct current; we will get a fluctuating magnetic field.

What will happen if excitation is decreased in alternator?

If you reduce the excitation you reduce the output power and torque load on the rotor. When excitation reaches zero so does the output energy.