Patent ID: 7800929

Claim:
A method for controlling a PWM cyclo-converter as a power converter for directly connecting each phase of a three-phase AC power source to each phase of the power converter having three-phase outputs by a two-way semiconductor switch that is a combination of two one-way semiconductor switches supplying electric current only in one direction and capable of being respectively independently turned on and off, wherein when the phase of the highest potential of the three-phase AC power source is called a maximum potential phase, the phase of an intermediate potential is called an intermediate potential phase and the phase of the lowest potential is called a minimum potential phase, the method comprising: a step for selectively turning the two-way semiconductor switch on and off; and a step for outputting the maximum potential phase, the intermediate potential phase and the minimum potential phase to output side terminals, wherein the turning on and off operations of the two-way semiconductor switch are repeated at intervals of short time, within the intervals of short time, a first terminal of the output side terminals outputs in order the maximum potential phase, the intermediate potential phase and the maximum potential phase, a second terminal of the output side terminals outputs in order the maximum potential phase, the intermediate potential phase, the minimum potential phase, the intermediate potential phase and the maximum potential phase, and a third terminal of the output side terminals outputs in order the intermediate potential phase, the minimum potential phase and the intermediate potential phase.