| 摘要 |
PURPOSE:To suppress the abnormal rise of a snubber capacitor voltage by providing shortcircuiting switch elements at the parallel resistors of reactors of a current change rate suppressor, and shortcircuiting the parallel resistors when a large abnormal current is interrupted. CONSTITUTION:A DC power from a DC power source 1 is supplied to switch circuits 100, 200 of positive and negative electrode sides connected in series, and an induction motor 700 is connected with the midpoint of the both switch circuits. Each of the circuits 100, 200 has a GTO thyristor 41, a circulating diode 42 connected in anti-parallel with the thyristor, and a snubber circuit made of a snubber capacitor 43. A current change rate suppressor formed of a reactor 31, a diode 32, a parallel resistors 33 and a thyristor 34 of a shortcircuiting switch element is connected in series with the GTO 41. Thus, when the GTO 41 interrupts the defective current due to an arm shortcircuiting defect, and simultaneously turns ON the thyristor 43 to shortcircuit the resistor 33, thereby increasing the circulating current attenuating time constant. |
