An analysis of noise reduction in variable reluctance motors using pulse position randomization.

218 Pages·1994·4.7 MB·en_US

by  Smoot, Melissa C.

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