Abstract: A power converter for an electric locomotive includes an insulating transformer, an AC/DC converter, an inverter, a PWM controller, and a voltage controller. The insulating transformer is supplied with high-voltage AC power from an AC overhead wire to convert a high voltage to a low voltage and output low-voltage AC power. The AC/DC converter receives the low-voltage AC power and performs AC/DC conversion. The inverter receives an output from the AC/DC converter and performs DC/AC conversion for supply to a load. The PWM controller outputs a PWM control signal having a predetermined pattern, the pattern for removing specific harmonic components from an output of the inverter or attenuating the specific harmonic components to at most a predetermined level. The voltage controller controls a DC output voltage of the AC/DC converter to control an output voltage of the inverter.

Abstract: A power converter for an electric locomotive includes an insulating transformer, an AC/DC converter, an inverter, a PWM controller, and a voltage controller. The insulating transformer is supplied with high-voltage AC power from an AC overhead wire to convert a high voltage to a low voltage and output low-voltage AC power. The AC/DC converter receives the low-voltage AC power and performs AC/DC conversion. The inverter receives an output from the AC/DC converter and performs DC/AC conversion for supply to a load. The PWM controller outputs a PWM control signal having a predetermined pattern, the pattern for removing specific harmonic components from an output of the inverter or attenuating the specific harmonic components to at most a predetermined level. The voltage controller controls a DC output voltage of the AC/DC converter to control an output voltage of the inverter.

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.