Loss minimization control of an induction motor drive

A practical method is presented for operation of an inverter-fed induction motor drive at the point of maximum efficiency while maintaining any particular torque-speed load point. The design and operation of an economical, microprocessor-based adaptive controller used to modify a commercially available six-step inverter for minimum loss operation of an induction motor are described. Experimental results are presented in graphical form, making it possible to compare the overall drive system efficiencies of loss minimization control and constant volts/hertz control operation for a standard-efficiency induction motor of 10 hp rating. The greatest potential for energy savings is found to exist for the case of loads with nonlinear torque-speed characteristics, such as a fan or pump load.<
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