Accession Number : ADA283846

Title :   An Analysis of Noise Reduction in Variable Reluctance Motors Using Pulse Position Randomization

Descriptive Note : Master's thesis

Corporate Author : MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF OCEAN ENGINEERING

Personal Author(s) : Smoot, Melissa C.

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Report Date : MAY 1994

Pagination or Media Count : 104

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 randomization on acoustic noise. VRM commutation points are varied using a uniform probability density function and a 4 state Markov chain among other methods. The theory of VRM 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

Descriptors :   *NOISE REDUCTION, *ACOUSTIC SCATTERING, VIBRATION, CONTROL SYSTEMS, SIGNAL TO NOISE RATIO, INVERTERS, ELECTRIC MOTOR NOISE, LOUDNESS, ACOUSTIC FIELDS, MARKOV PROCESSES, THESES, PROBABILITY DENSITY FUNCTIONS, STATORS

Subject Categories : ACOUSTICS
      NOISE POLLUTION AND CONTROL

Distribution Statement : APPROVED FOR PUBLIC RELEASE

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