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   Electromagnetic and Acoustic Emissions From a Digitally Controlle...   [View] 
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 Author(s)   L. Xu; Z.Q. Zhu; D. Howe 
 Abstract   The electromagnetic interference and the radiated acoustic noise from a microprocessor-controlled induction machine are investigated, with particular reference to comparing the influence of PWM strategies, viz. space vector and random PWM, with direct torque control. In contrast to space vector PWM which results in concentrated harmonic spectrum and tonal acoustic noise emission, random PWM and direct torque control strategy result in similar wideband harmonic spectra and indeed less irritating atonal acoustic noise. However, they produce almost identical conducted and radiated EMI spectra, on which it was found that there exist dominant discrete peaks due to the energy concentrated into discrete bands by the action of periodic signals on the external and internal buses of the microprocessor system. A technique, referred to as software waiting loop length control (SWLLC), is proposed to reduce the radiated EMI from digital PWM drive system. By randomly changing the length of the software waiting loops, discrete EMI components can be spread across a larger frequency range. Using this technique, significant reduction of radiated interference levels has been achieved in a typical PWM drive system. 
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Filename:EPE1999 - PP00551 - Xu.pdf
Filesize:207.8 KB
 Type   Members Only 
 Date   Last modified 2004-03-23 by System