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Torque limit of PM motors for field-weakening region operation

United States Patent

8,115,437
February 14, 2012
View the Complete Patent at the US Patent & Trademark Office
The invention includes a motor controller and technique for controlling a permanent magnet motor. In accordance with one aspect of the present technique, a permanent magnet motor is controlled by receiving a torque command, determining a physical torque limit based on a stator frequency, determining a theoretical torque limit based on a maximum available voltage and motor inductance ratio, and limiting the torque command to the smaller of the physical torque limit and the theoretical torque limit. Receiving the torque command may include normalizing the torque command to obtain a normalized torque command, determining the physical torque limit may include determining a normalized physical torque limit, determining a theoretical torque limit may include determining a normalized theoretical torque limit, and limiting the torque command may include limiting the normalized torque command to the smaller of the normalized physical torque limit and the normalized theoretical torque limit.
Royak; Semyon (Beachwood, OH), Harbaugh; Mark M. (Richfield, OH)
Rockwell Automation Technologies, Inc. (Mayfield Heights, OH)
12/ 036,099
February 22, 2008
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH & DEVELOPMENT This invention was made with Government support under contract number NREL-ZCL-3-32060-03; W(A)-03-011, CH-1137 awarded by Department of Energy. The Government has certain rights in the invention.