In the paper we present a new type of cycloconvertor that is based on the static induction transistor (SIT). We also present a new control method, which we develop by using a pulsewidth-modulation (PWM) technique. The control algorithm is extremely simple in this method, enabling microprocessor-based control. A prototype six-pulse cycloconvertor is controlled by a small-scale controller based on TMS9995. The results show that many problems that arise when using the conventional cycloconvertor can effectively be solved by our new control method.