Three-phase motors in single-phase operation

 

Three-phase motors can also be operated with single-phase alternating voltage. A time shift in the current in one winding strand is normally achieved using an operating capacitor. This in turn causes a magnetic field to be generated. However, due to the capacitor the currents flowing in the windings are not all of equal magnitude. The rotating field is no longer circular but has an elliptical shape. This leads to a considerable drop in power and starting torque.