Downsized and high efficient direct power converters for high-power servo application

This paper proposes to apply an AC/AC direct converter topology for servo systems. In the conventional AC/AC converter which consists of a PWM rectifier and a PWM inverter, the p-n junction temperature becomes high at the low output frequency or the servo-lock operation because the output current concentrates at the specific switching devices in the inverter. On the other hands, the AC/AC direct converter such as matrix converter is able to reduce the junction temperature of the switching devices. In this paper, the junction temperature of each type of the converters is evaluated by using the thermal simulation of the p-n junction. The output frequency of the conventional matrix converter and the indirect matrix converter are 1/8 and 1/2 smaller compared to the conventional AC/AC converter when the same temperature ripple is obtained in low output frequency region. That is, when these converters use the same current rating device, the matrix converter can operate at a frequency lower than the conventional AC/AC converter.