Energy-saving operation of the hysteresis motor utilizing overexcitation phenomenon

The hysteresis motor produces the torque by magnetic hysteresis. The overexcitation for a short period of the hysteresis motor running at synchronous speed reduces the stator current and increases the pull-out torque at the same time. This excellent effect after one-time overexcitation lasts theoretically forever. However, the sudden changes of stator voltage or load torque reduce and vanish it. The duration time of the effect after one-time overexcitation is not clear in ideal condition without stator voltage or load torque changes. We used the three-phase balanced voltage source and measured the duration time after one-time overexcitation under no changes of the stator voltage and load torque. It was found that the effect by one-time overexcitation lasted for two weeks of the experimental period. It seems that the effect will last forever. It is clear that energy-saving operation of the hysteresis motor utilizing overexcitation phenomenon is quite useful.