Synchronous running of shaded-pole permanent magnet motors

A mathematical model for the rotary motion of a shaded-pole permanent magnet motor is established and significant non-dimensional combinations of the electrical and mechanical parameters of the motor are identified. Criteria for the choice of these parameters to ensure that the motor is in synchronous running in only one direction are given. It is shown that such synchronous running is perturbed by unwanted oscillations but a criterion for determining a saliency parameter for these oscillations to have minimum amplitude is found. Conditions under which the motor can develop maximum torque are investigated and conclusions relevant to the design of shaded-pole motors given.