A single-phase induction motor is an AC motor designed for low-power applications fed from the single-phase 230 V supply found in homes and small businesses. Unlike three-phase motors, a single winding group cannot create a rotating magnetic field on its own, so it needs an extra arrangement to start.

Working Principle

When the main stator winding is fed from a single phase it produces a pulsating magnetic field, but this field alone cannot supply the starting torque to turn the rotor. Once the rotor is set in motion it runs on the induction principle, slipping slightly behind the magnetic field.

Starting Methods

To create starting torque, an auxiliary winding displaced by 90 degrees is used. A start capacitor in series with the auxiliary winding creates a phase difference; some types also keep a permanent run capacitor in circuit. The auxiliary winding is switched out by a centrifugal switch once the motor reaches a set speed.

Areas of Use

Single-phase induction motors are used where three-phase supply is unavailable: small water pumps, compressors, fans, washing machines, refrigeration units and workshop benches. They are generally chosen at powers up to a few kilowatts.

Single-Phase or Three-Phase?

If your premises have a three-phase supply, a three-phase induction motor of the same rating offers higher efficiency, lower vibration and simpler starting. DRG Motor supplies 400 V / 50 Hz three-phase motors for applications of 0.55 kW and above; we can determine the right solution together according to your need.