1. Hysteresis Motors Stator Rotor same as for induction motor
Smooth cylinder

2. Principle of Operation
Stator Flux establishes these magnetic poles
Rotor poles “induced” by Stator Flux

3. Spin the stator poles with the rotor blocked
Rotor poles follow the rotating flux, but lag behind by angle δh
Stator poles moving CCW

4. Spin the stator poles with the rotor blocked
If the rotor is released, it will accelerate to synchronous speed

5. Hysteresis Power Loss, Ph
where
fr = frequency of flux reversal in the rotor (Hz)
Bmax = maximum value of flux density in the air gap (T)
Ph = heat-power loss due to hysteresis (W)
kh = constant

6. Mechanical Power developed

7. Mechanical Power Developed (cont)
Independent of frequency and speed!

8. Hysteresis Motor at Synchronous Speed
No load and negligible rotational losses
Induced rotor magnets remain locked with the rotating poles produced by the stator

9. Hysteresis Motor at Synchronous Speed
The rotor slows down and the induced rotor magnets lag the rotating poles of the stator by an angle δmag .
The rotor returns to synchronous speed at the new torque angle.
Apply a step increase in shaft load.

10. Hysteresis Motor at Synchronous Speed
If shaft load causes δmag>90°, the rotor pulls out if synchronism, the magnet torque drops to zero, and the machine develops hysteresis torque. This torque is not sufficient to carry the load.

11. Torque-Speed Characteristic
Constant Hysteresis Torque allows the motor to synchronize any load it can accelerate
“Normal” Operating Range