Motor

An electromechanical device (electrical machine) that converts electrical energy or power (EI) into mechanical energy or power (ωT) is called a motor.

Electric motors are used for driving industrial machines, for example, hammer presses, drilling machines, lathes, shapers, blowers for furnaces, etc., and domestic appliances, for example, refrigerators, fans, water pumps, toys, mixers, etc. The block diagram of energy conversion, when the electromechanical device works as a motor, is shown in Figure 11.3.

Fig. 11.3  Motor

Note: The same electromechanical device is capable of operating either as a motor or generator depending upon whether the input power is electrical or mechanical. Thus, the motor and generator actions are reversible.

The conversion of energy either from electrical to mechanical or from mechanical to electrical takes place through magnetic field. During the conversion, whole of the energy in one form is not converted in the other useful form. In fact, the input power is divided into the following three parts:

1. Most of the input power is converted into useful output power.
2. Some of the input power is converted into heat losses (I²R) that are due to the flow of current.