Equivalent Circuit Model for a Shaded-Pole Induction Motor: II. One Shading Coil with a Stepped Air Gap

The rotating coupled circuit equations for an induction motor with a nonuniform air gap and two stator windings at an arbitrary displacement angle are transformed to formulate d-q, forward-backward, and equivalent circuit models. The air gap is assumed to be a constant plus a second harmonic variation. Shaded-pole performance is simulated by setting the auxiliary winding voltage to zero and adding the effect of mmf and permeance harmonics. Comparisons between test data and model predictions show reasonably good correlation. The major difference between modeling the reluctance variation and using an average constantair gap is seen in the value of starting torque. For the motor simulated, modeling the variable air gap more than triples the calculated starting torque