Abstract: A power converter including a plurality of arms. Each of the arms is composed of series connected first and second switching devices, first and second freewheeling diodes respectively connected in antiparallel with the first and second switching devices, and a phase capacitor connected in parallel with a series circuit of the first and second switching devices. The power converter further includes a DC power source connected between a DC positive bus and a DC negative bus, and a filter capacitor connected between the DC positive bus and the DC negative bus and in parallel with the DC power source. Each of the arms of the power converter is connected individually to the filter capacitor between the DC positive bus and the DC negative bus.

Abstract: A power conversion system always keeps a constant voltage level relative to the ground potential and shows an improved controllability for the noise compensation current. In the noise reduction circuit of the system, a rectified DC voltage is applied to the positive side output line and the negative side output line. The DC voltage is divided by a pair of capacitors connected in series with the intermediary point held to the ground potential. Thus, the positive side output line can always supply a positive voltage that is held to a constant level relative to the ground potential. Similarly, the negative side output line can always supply a negative voltage that is held to a constant level relative to the ground potential. Additionally, as the transistors are controlled for on/off operations by the amplifier, the noise compensation current flows through the noise reduction circuit between the input grounding terminal of the full-wave rectifier and the ground.

Abstract: In an inverter apparatus of the type comprising a plurality of thyristors connected between a DC source and an AC load, a control circuit for sequentially turning ON and OFF the thyristors according to a predetermined sequence, and a reverse bias circuit including a pair of power transistors respectively connected in series with the DC source and ON.sup.. OFF controlled by the control circuit for applying a reverse bias to the thyristors to effect simultaneous commutation thereof, and a pair of diodes connected across the DC source, there are provided a second thyristor connected between the plurality of thyristors and the power transistors and turned ON at the time of commutation of the plurality of thyristors by the control circuit and a reactor connected in parallel with the second thyristor.