Question

State two ways by which the speed of rotation of an electric motor can be increased.

Answer 1

The speed of rotation of an electric motor can be varied based on the following factors:

• Magnetic flux - By decreasing the flux, the speed of the motor can be increased. The flux can be changed by changing the current with a shunt field rheostat.
• Resistance of the armature circuit - By decreasing the resistance, there is increase in the armature current which causes a larger torque to be developed. This increased torque causes the dc motor to increase in speed.
• Applied voltage - The armature is supplied with different voltages by means of a switch gear. Different speeds can be obtained from different voltages.