Patent ID: 7602139

Claim:
A system for estimating rotor angle for controlling a permanent magnet AC motor having sinusoidal current excitation, comprising in combination: a first unit for supplying a high-frequency current signal to said motor; and a second unit for extracting estimated rotor angle information from a current feedback signal from said motor; wherein said first unit supplies sine and cosine signals to said motor; and wherein said second unit measures amplitudes of three component signals u, v and w in said current feedback signal from said motor, computes a pair of calculated signals, and extracts said rotor angle information from said pair of calculated signals, further comprising a third unit for detecting a rotor magnetic axis polarity based on said current feedback signal from said motor; wherein said third unit injects a d-axis DC current to said motor at a first level and a second level, measures first and second time average ripple currents in said current feedback signal when said d-axis current is at said first level and at said second level, and determines said magnetic polarity from said first and second time average ripple currents.