| 摘要 |
PROBLEM TO BE SOLVED: To provide a technique for obtaining three-phase alternating currents the sin curves of which do not contain harmful noise and are neat. SOLUTION: A capacitor is connected with each phase on the primary side and secondary side of a three-phase transformer 12, and each is provided with a resonance circuit. A direct current interrupted through switching circuits S1 to S6 that are alternately and repeatedly turned on and off with a slight dead time provided by a control circuit 24 is supplied to the primary-side resonance circuits so that the rise time is delayed by an electrical angle of 120 deg. for every phase. Thereby, a three-phase alternating voltage is induced in the coil in each phase on the primary side and the coil in each phase on the secondary side, and three-phase AC power supply is obtained from both the ends of capacitors Csu, Csv, and Csw for resonance on the secondary coil side. In this case, it is recommendable to utilize the ascending portion of F-V characteristic curve of induced voltage in each phase on the secondary side to vary the control frequency for direct current interruption in the switching circuits and thereby make the secondary voltage of the three-phase transformer substantially proportional to the control frequency. |
