Publication Date


Document Type


First Advisor

Woo, Peng-Yung

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Electrical Engineering


Electric current regulators; Electric controllers; Electric motors; Induction


The development and analysis of an asynchronous current regulator for a variable-speed induction motor controller is presented in this thesis. An asynchronous current regulator has a sampling time which is not fixed to the PWM waveform of the motor controller. This asynchronous aspect would offer an operator the ability to change the PWM frequency of the motor controller to almost any desired frequency. Typical mid- to high-performance currentregulated motor controllers operate with a synchronous current regulator which allows only a few fixed PWM frequencies for a given sampling time. A synchronous current regulator was first analyzed and simulated to provide a properly tuned system which would make a good baseline regulator. This synchronous system was modified to operate with the sampling time no longer fixed with the PWM waveform. The effects of this mode of operation were oscillations in both the torque and flux currents as well as a slight increase in overshoot in the step response. An asynchronous current regulator was then developed and simulated allowing the selection of any PWM frequency for a given sampling time. At the heart of this new regulator is a PWM phase-angle compensation algorithm which was developed to minimize the oscillations caused by asynchronous operation. Simulations of this asynchronous implementation show that any choice of PWM frequency can be selected with negligible loss in response and significantly less ripple as opposed to the response of a typical synchronous current regulator.


Includes bibliographical references (leaf [72])


ix, 100 pages




Northern Illinois University

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