EMI experimental comparison of PWM inverters between hard- and soft-switching techniques

Electromagnetic interference (EMI) is a major concern for inverter driven motor drives. The sources of EMI have been commonly identified as coming from high switching dv/dt and di/dt rates interacting with inverter parasitic components. The reduction of parasitic components relies on highly integrated circuit layout and packaging. On the other hand, switching dv/dt and di/dt can be potentially reduced by soft-switching techniques. In this paper, the EMI sources of a hard-switching SPWM inverter are identified and measured with separation of common-mode and differential-mode noises. The noise reduction by an auxiliary resonant snubber inverter is presented. The test condition and circuit layout is described as the basis of the study. Finally, the experimental EMI spectra of both hard- and soft-switching inverters is compared.