Magnetic Noise Caused by Output Waveform Harmonics of Voltage Source Inverters

Abstract

Harmonic components included in the output waveforms of inverter circuits cause magnetic noise, that is, audio noise, from the output transformers or load motors. In order to estimate the magnetic noise due to the harmonic components, we have already proposed the equivalent noise voltage E_s and current I_s.
In this paper, by applying the above E_s, we compare quantitatively the magnetic noise in the various ordinary voltage source inverters, both PWM inverters with multi-pulse waveforms and PAM inverters with multi-step waveforms. Then, in order to reduce the magnetic noise, we improve the output waveforms of the PWM inverters by applying E_s into the idea of harmonic elimination. Moreover, by employing PAM system as voltage regulation in the above method, we can get the more improved output waveforms with lower noise and also lower distortion.