| 摘要 |
PURPOSE:To suppress unbalance in a terminal voltage of a load of each phase due to the unbalance of the load. CONSTITUTION:A detected value of a phase-A current detected by CT 21 and obtained through a gain regulator 61 and a detected value of a neutral conductor current detected by CT 51 provided at a neutral conductor 9 and obtained through a gain regulator 64 are added up in a second adder 52, with waveforms left as they are, and an added value thus obtained is made the amount of correction of a voltage command value set by a voltage setting unit 27. When phases of the detected value of the phase-A current and the detected value of the neutral conductor current are the same, the amount of correction increases, and when they are reverse, this amount decreases. A deviation of the result of this correction from a detected value of a voltage between A and N is computed in a first adder 31 and the result of this computation is controlled to be zero by a voltage regulator 41. The same control is executed also for phases B and C. Even when loads of discrete phases are unbalanced and the current flows through the neutral conductor 9, an output voltage of each phase of a three-phase AC power source 10 is controlled by these operations. Thereby terminal voltages of the loads are balanced and a prescribed voltage is maintained. |
