Abstract: With a power conversion device, it is possible to lengthen the lifespan of a mechanical switch by preventing an absorption by the mechanical switch of induction energy accumulated in a reactor when there is a problem. When a mechanical switch is turned off when there is a problem, an absorption by the mechanical switch of induction energy accumulated in a reactor is prevented by the energy accumulated in the reactor being released to a capacitor via a diode, thus enabling a lengthening of the lifespan of the mechanical switch.

Abstract: A power conversion equipment or apparatus includes an AC/DC conversion circuit which rectifies and converts an alternating current power source to a direct current, and a DC/AC conversion circuit which converts the direct current to a high frequency three-phase alternating current voltage having 3N pulses times a fundamental wave frequency in a half cycle, the fundamental wave frequency being higher than the frequency of the alternating current power source. The power conversion equipment also includes a three-phase high frequency transformer having a primary winding that is connected to the output of the DC/AC conversion circuit, a rectifier circuit which rectifies a secondary winding voltage of the three-phase high frequency transformer, and a filter circuit connected to the direct current output of the rectifier circuit.

Abstract: With a power conversion device, it is possible to lengthen the lifespan of a mechanical switch by preventing an absorption by the mechanical switch of induction energy accumulated in a reactor when there is a problem. When a mechanical switch is turned off when there is a problem, an absorption by the mechanical switch of induction energy accumulated in a reactor is prevented by the energy accumulated in the reactor being released to a capacitor via a diode, thus enabling a lengthening of the lifespan of the mechanical switch.

Abstract: An electric power system comprises an AC motor, a first DC voltage unit, an inverter as a power converter, being connected between the AC motor and first DC voltage unit, for exchanging power between these two components; and a controlled DC power supply which is connected between an arbitrary spot of a coil of the AC motor and a positive or negative electrode of the first DC voltage unit and which connects at least one semiconductor switching element and a battery as a second DC voltage unit in series.

Abstract: In a power conversion device, a capacitor series circuit is connected in parallel with a direct current power supply, outputs an alternating current voltage having three or more potentials in a half-cycle period with the capacitor series circuit as a direct current input, wherein a neutral point of an alternating current load and an intermediate connection point of the capacitor series circuit are directly connected, the voltage of each of the capacitors is detected, and a zero voltage vector obtained by making each alternating current output of the same potential is adjusted in accordance with the difference between the voltages.

Abstract: An electric power system comprises an AC 100, a first DC voltage unit 20, an inverter 10 as a power converter, being connected between the AC motor 100 and first DC voltage unit 20, for exchanging power between these two components; and a controlled DC power supply 60 which is connected between an arbitrary spot of a coil of the AC motor 100 and a positive or negative electrode of the first DC voltage unit 20 and which connects at least one semiconductor switching element 62 and a battery 61 as a second DC voltage unit in series.

Abstract: An inverter converting by using semiconductor power switching devices a DC voltage supplied from a main battery to an AC voltage supplied to an AC motor. Unipolar switching devices such as MOSFETs are used as the power switching devices. The power switching devices are controlled so that the output voltage of the inverter is composed of pulses taking three levels in the operation range of high output power. This makes it possible to reduce the stationary loss and switching loss of the switching devices, and to increase the efficiency of the inverter.

Abstract: An AC variable speed driving apparatus including an AC motor and an inverter for driving the motor. The AC motor includes a synchronous motor and an induction motor. The synchronous motor includes first stator windings and a first rotor having a permanent magnet. The induction motor includes second stator windings and a second rotor. The first and second stator windings are disposed so that they do not magnetically interfere with each other. The first and second rotors are mounted on a common axis of rotation. The inverter supplies AC power to the stator windings so that the synchronous motor and the induction motor are driven independently. A highly efficient, large output and low cost system can be realized in a wide speed range.

Abstract: An electric system for an electric vehicle includes a main battery used for driving the vehicle, an auxiliary battery used for accessories of the vehicle, an AC motor for driving one or more wheels, an inverter for converting DC power supplied from the main battery to AC power to be supplied to the AC motor, and an auxiliary battery charging circuit for charging the auxiliary battery by using the AC power from the inverter. When charging the auxiliary battery, the AC power is insulatedly transformed and then rectified. In another example, an input capacitor in the inverter is charged by a DC-DC converter connected with the auxiliary battery as its power supply when the inverter starts. The system enables the auxiliary battery charging circuit to be small, light and low cost. The system can also charge the auxiliary battery for accessories even when the vehicle is stopping.