What will be the power factor when the synchronous motor is over excited?

What will be the power factor when the synchronous motor is over excited?

If DC field excitation of a synchronous motor is such that back EMF Eb is greater than applied voltage V, then the motor is said to be over-excited. An over-excited synchronous motor draws leading current. Therefore, if the field of the synchronous motor is overexcited then its power factor will be leading.

Does an over excited grid connected synchronous motor operate with leading or lagging power factor?

An over-excited synchronous motor has a leading power factor. This makes it useful for power-factor correction of industrial loads.

Does a change in the excitation of a synchronous motor affect its power factor?

If the excitation is further increased (i.e., over excitation), the motor power factor becomes leading. Note. The armature current (Ia) is minimum at unity p.f and increases as the power factor becomes poor, either leading or lagging.

Can power factor of a synchronous motor be controlled?

The advantages of the synchronous motor are the ease with which the power factor can be controlled and the constant rotational speed of the machine, irrespective of the applied load. Synchronous motors, however, are generally more expensive and a d.c. supply is a necessary feature of the rotor excitation.

What is excitation current in motor?

Synchronous motor excitation refers to the DC supply given to rotor which is used to produce the required magnetic flux. The field current, which causes this unity power factor is called normal excitation or normal field current.

How can the power factor of a synchronous motor be adjusted?

By varying the DC excitation of the motor, the power factor of the motor can be varied widely. Overexcited synchronous motors operate at leading power factor and provide reactive kVAR-like capacitors. This yields an improved power factor for the power-supply system.

How does excitation effect power factor?

A change in the excitation, thus, affects only the power factor of its output. This reduces the terminal voltage slightly, so let the excitation of the first alternator be increased so as to bring the terminal voltage back to its original value.

When does a synchronous motor have a lagging power factor?

If the field excitation is such that back EMF E b is less than the applied voltage V, then the motor is said to be under-excited. An under excited synchronous motor has a lagging power factor. If DC field excitation of a synchronous motor is such that back EMF E b is greater than applied voltage V, then the motor is said to be over-excited.

Which is true of an over excited synchronous motor?

An under excited synchronous motor has a lagging power factor. If DC field excitation of a synchronous motor is such that back EMF E b is greater than applied voltage V, then the motor is said to be over-excited. An over-excited synchronous motor draws leading current.

What happens to the V curve of synchronous motor?

The plot of power factor against the field current of synchronous motor is known as V curves of synchronous motor. The V curves at different power inputs are shown in Figure. With an increase in load, the V curves get shifted upwards, as shown in Figure.

When do you use a synchronous phase modifier?

For controlling the voltage of a transmission line, at the receiving end, a synchronous motor is used. In this application, the synchronous motor is made to run on no load and draw a leading current. The synchronous motor when used for the above purpose is called synchronous phase modifier.