Question

Choose the INCORRECT statement with respect to the single-phase hysteresis motor.

1. The rotor is a smooth solid cylinder of hard steel and does not carry any winding.
2. The stator is wound with only one winding without capacitor.
3. The hysteresis motor has a low noise figure compared to the single-phase induction motor.
4. The phenomenon of hysteresis causes the rotor magnetisation to lag behind the stator-created MMF wave.

Answer 1

Correct Answer - Option 2 : The stator is wound with only one winding without capacitor.

Concept of Hysteresis Motor:

Hysteresis motor is a single-phase synchronous motor with a cylindrical rotor made up of ferromagnetic material and does not require any DC excitation to the rotor.

Construction of Hysteresis motor: Hysteresis motor consists of a stator and rotor.

• Stator:  The stator is wound with main and auxiliary windings so as to produce the rotating magnetic field. In some hysteresis motor, the stator can also be shaded pole type. The stator is designed to produce synchronizing revolving field from a single-phase supply.
• Rotor:  The rotor is the smooth cylindrical type made up of hard magnetic material like chrome steel or alnico for high retentivity. The rotor does not carry any winding or teeth.​

​

Working of Hysteresis Motor:

• When hysteresis motor is started it behaves as a single-phase induction motor and while running it behaves like a synchronous motor.
• When the stator is energized with a single-phase AC supply it produces a rotating magnetic field.
• The main and auxiliary, windings must be supplied continuously at the start as well as in running condition so as to maintain the rotating magnetic field.