Analysis of Noise Current From an Inverter at High Frequency by a Spectrum Analyzer

This paper provides measurement results of the common-mode noise of a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$380-\mathrm{V}$</tex> inverter system by a spectrum analyzer (SA). Emphasis is on how to obtain the characteristics of the noise at 50 MHz, a frequency >1000x higher than the switching frequency. It is demonstrated that using the normal sweeping mode of SA, the results provide little information regardless of the RBW used. In contrast, the zero-span mode of SA can clearly reveal the property of the noise, thereby facilitating EMC diagnostic and optimization.