single phase motor Speed control
The synchronous rotational speed of the rotor (i.e. the theoretical unloaded speed with no slip) is controlled by the number of pole pairs (number of windings in the stator) and by the frequency of the supply voltage. Before the development of cheap power electronics, it was difficult to vary the frequency to the motor and therefore the uses for the induction motor were limited. r has no brushes and is easy to control, many older DC motors are being replaced with induction motors and accompanying inverters in industrial applications.