Research on common mode noise evaluation method

Common mode noise produced in single-phase full-bridge converter with bipolar SPWM is analysized. Common mode noise level evaluation method must be monodromy value and calculated simply in common mode EMI suppression system. The three evaluation indexes of maximal spectrum, average spectrum and common mode noise energy are proposed to express the common mode noise level. The computational complexity of three evaluation indexes and the relationship between three evaluation indexes and the delay time difference of two driving signals on three different conditions are studied. The computation of Common mode noise energy is very convenience without calculation of DFT or FFT. Simultaneously, the research results show that different operation conditions have no effect on the relationship between common mode noise energy and delay time difference of two driving signals. It is conclusion that common mode noise energy is a monodromy index ant can be considered as a good evaluation index of the common mode noise level.