An analysis of noise reduction in variable reluctance motors using pulse position randomization. PDF
Preview An analysis of noise reduction in variable reluctance motors using pulse position randomization.
DUDLEY KNOX LIBRARY NAVAL POSTGRADUATE SCHOOL MONTEREY CA 93943-5101 An Analysis of Noise Reduction in Variable Reluctance Motors Using Pulse Position Randomization by Melissa C. Smoot B.S. Elec. Eng. and Comp. Sci., Princeton University (1982) Submitted to the Department of Ocean Engineering and the Department of Electrical Engineering and Computer Science in partial fulfillment of the requirements for the degrees of Naval Engineer Master of Science in Electrical Engineering and Computer Science at the MASSACHUSETTS INSTITUTE OF TECHNOLOGY May, 1994 ©Melissa C. Smoot, 1994. All rights reserved. t,i DUDLEY KNOX LIBRARY NAVAL POSTGRADUATE SCHOOL MONTEREY CA 93943-5101 An Analysis of Noise Reduction in Variable Reluctance Motors Using Pulse Position Randomization by Melissa C. Smoot Submitted to the Department of Ocean Engineering and the Department of Electrical Engineering and Computer Science on May 13, 1994 in partial fulfillment of the requirements for the Degrees of Naval Engineer and Master of Science in Electrical Engineering and Computer Science Abstract The design and implementation of a control system to introduce randomization into the control of a variable reluctance motor (VRM) is presented. The goal is to reduce noise generated by radial vibrations of the stator. Motor phase commutation angles are dithered by 1 or 2 mechanical degrees to investigate the effect of VRM randomization on acoustic noise. commutation points are varied using a uniform probability density function and a 4 state Markov chain among other methods. VRM The theory of and inverter operation and a derivation of the major source of acoustic noise are developed. The experimental results show the effects of randomization. Uniform dithering and Markov chain dithering both tend to spread the noise spectrum, reducing peak noise components. No clear evidence is found to determine which is the optimum randomization scheme. The benefit of commutation angle randomization in reducing VRM loudness as perceived by humans is found to be questionable. Thesis Supervisor: Dr. John G. Kassakian Title: Professor of Electrical Engineering
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