Effects of nonsinusoidal inductance variation on saliency based position detection techniques in interior permanent magnet synchronous machines

An investigation into the effect of non-sinusoidal inductance variation on sensorless position detection in interior permanent magnet machines is presented. A rotor position method, based on determining the major axis of an ellipse defined by the motor current, is modified to provide position information over one cycle. The effect of non-sinusoidal inductance variation, caused by stator slotting, is demonstrated and it is shown that the accuracy of the elliptical technique can be significantly reduced as a result. A compensation scheme to improve accuracy is proposed.