Subsynchronous torque calculation in a shaded pole hysteresis motor

This paper deals with the synchronous dips in the torque-speed characteristic of a shaded pole hysteresis motor. The case under consideration is that of the synchronous dip related to the third harmonic of the air-gap field. First we show that the torque Varies between a maximum and a minimum value when the motor runs at one third of synchronous speed and we relate the torque values to the (B,H) characteristics of the rotor ring. Then, we calculate the rotor fields from the supply voltage and current of the motor. At the end we compare the experimental and theoretical values of the torques for different supply voltages at one third of synchronous speed.