Design of an EMI filter for static converters with off-line simplified measurements

In the last ten years there has been general concern on the electromagnetic compatibility of pulse-width modulation (PWM) inverter drives with particular attention to radiofrequency (RF) conducted disturbance. This paper addresses the problem of correct design and characterization before installation of the filter for conducted electromagnetic interference (EMI). General design guidelines are indicated, several materials are considered for the ferrite choke and the capacitors and a simple procedure is presented for the rapid evaluation of the filter insertion loss; the predicted emissions are shown to be very close to the real (measured) ones, obtained with the EMI filter installed inside the static converter.