# How the synchronous motor does behave when it is under Excited?

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## What happens when synchronous motor is under Excited?

Synchronous motor: … Lagging power factor: If field excitation is such that Eb < V the motor is said to be under excited and it has a lagging power factor. Leading power factor: If field excitation is such that Eb > V the motor is said to be over-excited and it draws leading current.

## How do synchronous motors control excitation?

The excitation system can be as simple as a fixed dc power supply connected to the field of the synchronous motor or, with additional sophistication, an automatic controller can be provided with var/power factor control or voltage regulation.

## How does synchronous motor behave at no load?

A synchronous motor running with no load will lead the current i.e. leading power factor like a capacitor. This synchronous motor running without load i.e. over-excited is synchronous condenser.

## What is exciter in synchronous motor?

The exciter provides the power to the electromagnets that form the poles on the rotor that in turn follow the rotating magnetic field from the system.

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## When the synchronous machine is connected to the AC system and is over excited it behaves like?

Explanation: An over excited synchronous machine delivers reactive power whereas an under excited one absorbs reactive power. Explanation: δ = atan(0.5*0.8/1.3) = 17.92°.

## When excitation is increased the synchronous generator operates at?

In synchronous generator, inverted V curve is drawn between field current on X-axis and power factor on Y-axis. At critical excitation the power factor is unity. If excitation is decreased, the generator operates at leading power factor and if excitation is increased, the generator operates at lagging power factor.

## When load on an over excited or under excited synchronous motor is increased rate of change of its armature current as compared with that of power factor is?

V curve of synchronous motor:

When the load on an over-excited or under excited synchronous motor is increased, the rate of change of its armature current as compared with that of the power factor is less and the same can be observed by using v curves as shown below.

## Why are synchronous motors not started under load?

3.2.

Synchronous motors are inherently not able to self-start on an AC power source with the utility frequency of 50 or 60 Hz. As stated in Chapter 1, this is because synchronous motors can develop a torque only when running at the synchronous speed.