Method for determining rotor position

A method for use in determining an absolute position of a rotor of a permanent magnet motor, comprising the steps of:

• detecting an angular position of a direct axis of the rotor;
• and
• detecting a polarity of the rotor to determine the absolute position of the rotor, wherein the step of detecting the polarity of the rotor comprises the sub-steps of:
• applying a square wave voltage to phase windings of a stator of the motor to generate an mmf vector parallel to the direct axis of the rotor;
• measuring phase currents of the phase winding;
• determining a direct axis current responsive to the measured phase currents and the angular position, wherein the direct axis current is parallel to the direct axis of the rotor;
• determining that the rotor is aligned with the mmf vector if the direct axis current is shifted positive;
• and
• determining that the rotor is aligned 180 degrees out of phase with the mmf vector if the direct axis current is shifted negative.