The operation of the hysteresis motor depends upon the hysteresis effect.
Hysteresis effect- In this effect the magnetization of ferromagnetic material whose relative permeability is greater than 1, due to varying magnetic field lags behind the magnetizing force.
Construction-
1. Stator-
It is designed in such a way that to produced synchronous revolving field from a single phase AC supply which is achieved by using permanent-split Capacitor type construction. The starting winding and main winding are connected in the same manner under running operation as well as starting operation.
2. Rotor-
It is designed by a smooth cylinder of magnetically hard steel, without winding or teeth on the rotor.
Operation-
(i) When the stator of the motor is energized from a single-phase supply, then a synchronously revolving field is produced due to split-phase operation.
(ii) Due to the hysteresis effect, the axis of magnetization of the rotor will lag behind the axis of the stator field by hysteresis lag angle an as shown in Fig. and rotor and stator pole become locked.
(iii) If the rotor is stationary, the starting torque produced is given by:
Starting torque proportional to the product of starting flux and rotor flux and sine angle of rotor and stator.
(iv) When motor reach at synchronism then motor become continue to run at synchronous speed and adjust torque angle.
Characteristics-
- It synchronized at any load, no matter how great is inertia.
- hysteresis motor is inherently quiet and produces smooth rotation of the load.