Electric motors - continued.

There are many types of electric motors. The most common types are:

a. Synchronous motors

b. Induction motors

Synchronous Motors

As in all electric motors, in a synchronous motor, magnetic fields are generated in both the stator and the rotor.

Usually the stator is supplied with alternating current (ac) and the rotor is supplied with direct current (dc.)

The key feature of a synchronous motor is that it runs at a constant speed, irrespective of the load it is carrying. A synchronous motor is relatively more expensive and the maintenance cost is also relatively high.

In industrial applications, synchronous motors are not very common. In a large industrial facility, usually less than 2% of the electric motors are likely to be of this type.

The figure provided here illustrates a synchronous motor which uses permanent magnets in the stator. An alternate method is to supply the stator with DC power.