Abstract: A control method for a PWM cyclo-converter is provided in which a voltage can be accurately generated even when a voltage command is small. In the PWM cyclo-converter, the turning on and off operations of two-way semiconductor switch are repeated at intervals of short time. As switching patterns, within the intervals of short time, a first terminal of output side terminals outputs in order a maximum potential phase P, an intermediate potential phase M and the maximum potential phase N, a second terminal of the output side terminals outputs in order the maximum potential phase P, the intermediate potential phase M, a minimum potential phase N, the intermediate potential phase M and the maximum potential phase P, and a third terminal of the output side terminals outputs in order the intermediate potential phase M, the minimum potential phase N and the intermediate potential phase M.

Abstract: A control method for a PWM cyclo-converter is provided in which a voltage can be accurately generated even when a voltage command is small. In the PWM cyclo-converter, the turning on and off operations of two-way semiconductor switch are repeated at intervals of short time. As switching patterns, within the intervals of short time, a first terminal of output side terminals outputs in order a maximum potential phase P, an intermediate potential phase M and the maximum potential phase N, a second terminal of the output side terminals outputs in order the maximum potential phase P, the intermediate potential phase M, a minimum potential phase N, the intermediate potential phase M and the maximum potential phase P, and a third terminal of the output side terminals outputs in order the intermediate potential phase M, the minimum potential phase N and the intermediate potential phase M.

Abstract: A PWM inverter with a PWM pulse output. The PWM pulse signal is output upon magnitude comparison of phase voltage commands with a carrier wave of a triangular or a saw-tooth waveform. A maximum phase whose absolute value is a maximum among absolute values of phases of the phase voltage commands is selected. In a case where the phase voltage commands of the maximum phase are larger than a maximum value of the carrier wave. A difference obtained from a first subtraction of the maximum value of the carrier wave from phase voltage commands of the maximum phase is set as a first differential. The first differential is subtracted from the phase voltage commands of the respective phases in a second subtraction. The first and second subtraction results are set as phase output voltage commands of the respective phases.

Abstract: Transition from a sinusoidal wave voltage output to a six-step voltage output involves problems that smooth mode switching is difficult and that switching processing becomes complicated. The present invention provides a PWM inverter having PWM pulse output means (2) for outputting PWM pulse signals upon magnitude comparison of phase voltage commands with a triangular carrier wave.