Accurate estimation of rotor position and speed of induction motors near standstill

It is demonstrated by numerical analysis that the leakage inductance as seen from the stator windings of standard induction motors varies with the rotor position angle. The effect can be exploited to extract the rotor position, and speed, from measured stater voltages. The extraction algorithm is incorporated based on a modification of the pulsewidth modulator. Experimental results demonstrate position measurement with good noise rejection at any speed including standstill.