Abstract: A power supply device for an electromotive railcar, including a series circuit composed of a plurality of first capacitors, connected to receive a first DC voltage from an electric power line; a plurality of DC/AC/DC converters. Each of the DC/AC/DC converters including an inverter bridge with an input thereof connected in parallel to one of the first capacitors and having a plurality of power transistors, an insulating transformer with a high carrier frequency and having a primary winding connected to an output of the inverter bridge, and a rectifier circuit connected to a secondary winding of the insulating transformer to output a DC voltage.

Abstract: A power supply device for an electromotive railcar comprises a first capacitor connected to receive a DC voltage for outputting a first DC voltage, a DC/AC/DC converter, including an inverter bridge including power transistors connected to the first capacitor in parallel, an insulating transformer with high carrier frequency having a primary winding connected to an output of the inverter bridge and a rectifier circuit connected to a secondary winding of the insulating transformer to receive a second DC voltage, and a three-phase inverter including a bridge circuit of power transistors for generating a three-phase AC voltage on the basis of the second DC voltage.

Abstract: A circuit for driving a self-arc-extinguishing type power element 1 such as an IGBT, includes a signal supply circuit 7 for supplying an ON/OFF signal to the power element 1, an insulation circuit 5 for insulating an output signal of the signal supply circuit 7, a control section 100 for controlling rise time or fall time of a current flowing through the power element 1 based on an output of the insulation circuit 5, and a power amplifier 2, 3, 4 for driving the power element 1 based on an output of the control section 100.

Abstract: A control equipment for a resistance welding machine for welding a material by the Joule's heat generated in the material by applying an electric power to the material, including an inverter for converting a DC voltage to an AC voltage by pulse width modulation control, a transformer having a primary winding to which the AC voltage is applied and having a secondary winding which supplies an AC current to the material, and a control unit for generating an AC current reference with a rectangular waveform of a specified frequency, comparing the AC current reference with an output current of the inverter to obtain an error, and for PWM controlling the inverter so that the error becomes zero.

Abstract: A control equipment for a resistance welding machine for welding a material by the Joule heat generated in the material by applying an electric power to the material, including an inverter for converting a DC voltage to an AC voltage by pulse width modulation control, a transformer having a primary winding to which the AC voltage is applied and having a secondary winding which supplies an AC current to the material, and a control unit for generating an AC current reference with a rectangular waveform of a specified frequency, comparing the AC current reference with an output current of the inverter to obtain an error, and for PWM controlling the inverter so that the error becomes zero.

Abstract: A method of controlling a battery car in which a motor is driven by a battery and the battery is charged with regeneration power generated by deceleration torque comprises the steps of charging a large-capacitance capacitor connected in parallel with the battery and the motor while restricting a current flowing from the battery to the large-capacitance capacitor, when the voltage of the large-capacitance capacitor is lower than a first voltage, charging the battery to a preset voltage while restricting a current flowing from the large-capacitance capacitor to the battery, when a charging voltage of the large-capacitance capacitor is increased above a predetermined voltage by the regeneration power, and driving the motor with only the charge stored in the large-capacitance capacitor, when the voltage of the large-capacitance capacitor is at least a second voltage.