Running Three Phase motors with single Phase supply

A three phase device can be run with a single phase converter by means of a static capacitor phase converter.  The phase converter converts the single phase voltage into three voltages which can be connected to the three phases of the motor. 

The single phase supply is connected to two of the motor phase terminals.  The other terminal is connected to one of the single phase terminals through a capacitor.  The capacitor introduces a phase shift which causes the third phase to be out of phase by 120 degrees.  The produces the rotating magnetic field required for starting and running the three phase motor.    

In motors, the starting current is usually about six times the rated current.  Hence, a bigger value capacitor is usually used as a starting capacitor.  The starting capacitor is kept in line by means of a switch which is opened as the motor picks up speed. 

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