A resonant turn-off snubber for high power IGBT converters

This paper presents a resonant active turn-off snubber for high power IGBT power converter applications. The main feature of this snubber is that the maximum current rating of the auxiliary switching devices is small compared to that of the main switches. Comparing the costs of the snubber elements, to the benefits of the snubber makes it an extremely attractive option for reducing switching losses and EMI in high power converters. The snubber components can be combined into a single module which can be fitted to an existing converter without any modifications to the control method or basic structure of the converter. The basic operation of the snubber is described and theoretically analyzed. An experimental version of the snubber is evaluated on an 80 kVA phase-arm. A reduction of 72% in the effective turn-off losses was measured. The effect of the snubber on the sources of EMI namely the magnetic and electric fields near the converter are also investigated.