Electric machine rotor position encoder

摘要

A rotor position encoder for an electric motor comprises a disc member (18) mounted to rotate with the rotor shaft. The encoder has a set of radially extending features formed with angularly evenly spaced leading edges and unevenly spaced trailing edges. The leading edges induce a signal in a sensor (16) that corresponds to the relative timing of power switches for each motor phase. The trailing edges define a cyclical code by which motor controlling circuitry is able to determine the phase of rotation of the rotor and thus establish the correct power switch actuation sequence. An electric motor control system and methods of starting electric motors are also disclosed.