Allen-Bradley Company, LLC

David M Brod

Thomas Arthur Nondahl

Luis J Garces

Robert L Pitsch

A system for accurately determining a torque current i.sub.qe for use in field oriented control of an induction motor at low rotor frequencies (e.g., about half of the motor rated frequency) which provides an ideal no load current and still enables high torque at low speed. The system includes a frequency/correction angle identifier which, based on an applied stator voltage frequency, provides a correction angle which is added to a perceived phase angle to generate a corrected phase angle which is used to calculate the torque current component i.sub.qe. The torque current component is then used by a slip calculator and an IR compensator to adjust motor operation.

Apparatus to reduce no load current at low frequencies

A dual phase resolver to digital converter having two separate channels for generating rotor position data. The first channel generates an indication of rotor position based on a sinewave type reference signal applied to a first stator winding and the rotor signal while the second channel provides an indication of rotor position based on a cosinewave type reference signal applied to the second stator winding and the rotor signal. Logic circuitry associated with the data channels provide separate fault data indicative of when position data may be subject to error. The data from the two channels are selectively combined in the output of the converter. Data from one channel is used when the other channel is subject to fault. An average of the data is used when both channels are operating properly in order to provide greater accuracy.

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Greendale, WI, United States of America

David M Brod