A hysteresis motor works on the principle of

A hysteresis motor works on the principle of

Working of Hysteresis Motor

The operation of the hysteresis motor depends on the permanently magnetized rotor which provides continuously revolving magnetic flux. It usually consists of the following components:

(a) The stator is wound with main and auxiliary windings. Usually, the auxiliary winding is connected in series with a permanent capacitor for the split-phase operation.

(b) The rotor is a smooth solid cylinder of hardened high-retentivity steel whose hysteresis loss is very high. It does not contain any winding.

• The rotating magnetic field produced by phase-splitting induces eddy currents in the steel of the rotor.
• High-retentivity steel produces a high hysteresis loss, thus consuming an appreciable amount of energy from the rotating field when the reversal of flux direction in the rotor takes place.
• Simultaneously, the rotor begins to rotate on account of the magnetic field set up by the eddy currents in the rotor.
• A high starting torque is developed as a result of high rotor resistance which is proportional to hysteresis loss.
• As the rotor approaches synchronous speed, the frequency of flux reversals in the rotor decreases, and the rotor becomes permanently magnetized in one direction as a result of the high retentivity of the steel rotor.
• The rotor revolves at synchronous speed because the rotor poles magnetically lock up with the revolving stator poles of opposite polarity.
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