Patent ID: 7622882

Claim:
A permanent magnet machine, comprising: a motor with a stator having cores with windings thereon and a rotor, which is movable relative to the stator, having permanent magnets, the motor having an odd number of pole pairs; a resolver configured to indicate an even number of pole pair positions, whereby upon start-up the resolver identifies a rotor position ambiguous by a predetermined value; and a controller configured to receive a position signal from the resolver and generating a driving signal for moving the motor and wherein, upon start-up, the controller is configured to (i) pulse a first voltage pattern to the windings in the form of the drive signal corresponding to a presumed rotor position and obtain a first measurement of current in the windings resulting from the application of the first voltage pattern, (ii) pulse a second voltage pattern, opposite of the first voltage pattern, and obtain a second measurement of current in the windings resulting from the application of the second voltage pattern, and (iii) compare the first and second current measurements to resolve said rotor position ambiguity.