A power converting device, in one possible configuration, includes a chopper circuit with a first semiconductor switching device, a fast recovery diode, and an inductor of which one end is connected to a connection point connecting between the first semiconductor switching device and fast recovery diode; a series circuit, connected in parallel with the fast recovery diode, including a rectifying diode with a greater reverse recovery loss and a smaller forward voltage drop than those of the fast recovery diode, and a second semiconductor switching device. The second semiconductor switching device has a lower breakdown voltage and a smaller forward voltage drop than those of the first semiconductor switching device, is configured to turn on when the first semiconductor switching device is turned off, and is configured to turn off at a timing before the first semiconductor switching device shifts from an off-state to an on-state.

A protection circuit includes a pre-charge rectifying circuit, a pre-charge resistor, a varistor, a switch, a main rectifying circuit, a bulk capacitor, and a control circuit. The pre-charge rectifying circuit is connected with an AC power source. The pre-charge resistor and the varistor are connected between the pre-charge rectifying circuit and the switch. The switch is further connected with a first node. The main rectifying circuit is connected between the AC power source and the first node. The bulk capacitor and the control circuit are connected between the first node and a ground terminal. The control circuit generates a first control signal to control the switch. The control circuit further generates a control signal set to control the main rectifying circuit.

A converter includes a transformer including primary windings and secondary windings, switches connected to the primary windings, an output inductor connected to the secondary windings, and a controller connected to the switches. The controller turns the switches on and off based on dwell times calculated using space vector modulation with a reference current {right arrow over (I)}.sub.ref whose magnitude changes with time.

An AC/DC converter receives an AC voltage at a first terminal and a second terminal. A rectifying bridge has a first input terminal coupled via a resistive element to the first terminal and a second input terminal connected to the second terminal, with output terminals of the rectifying bridge coupled to third and fourth terminals of the converter for generating a DC voltage. A first controllable rectifying thyristor couples the first terminal to the third terminal and a second controllable rectifying thyristor couples the fourth terminal to the first terminal. The resistive element functions as an inrush protection device during a first phase when the thyristors are turned off. In a second phase, the thyristors are selectively actuated.

An AC/DC converter receives an AC voltage at a first terminal and a second terminal. A rectifying bridge has a first input terminal coupled via a resistive element to the first terminal and a second input terminal connected to the second terminal, with output terminals of the rectifying bridge coupled to third and fourth terminals of the converter for generating a DC voltage. A first controllable rectifying thyristor couples the first terminal to the third terminal and a second controllable rectifying thyristor couples the fourth terminal to the first terminal. The resistive element functions as an inrush protection device during a first phase when the thyristors are turned off. In a second phase, the thyristors are selectively actuated.

A voltage converter includes a circuit formed by a parallel association, connected between first and second nodes, of a first branch and a second branch. The first branch includes a first controlled rectifying element having a first impedance. The second branch includes a resistor associated in series with a second rectifying element having a second impedance substantially equal to the first impedance. The second rectifying element may, for example, be a triac having its gate coupled to receive a signal from an intermediate node in the series association of the second branch. Alternatively, the second rectifying element may be a thyristor having its gate coupled to receive a signal at the anode of the thyristor.

A discharge circuit for a power supply circuit for a motor is configured to discharge a capacitor provided in the power supply circuit. The discharge circuit includes a first voltage detector detecting a voltage inputted to a primary side of the power supply circuit, a second voltage detector detecting a voltage on the secondary side, and a discharge resistance provided in parallel with the power supply circuit on the secondary side of the power supply circuit. A power supply control means performs discharge control when a voltage detected by the second voltage detector exceeds a regenerative determination value and, in a case that a voltage on the primary side detected by the first voltage detector becomes lower than a power failure determination value, the power supply control means performs the discharge control after a lapse of a time period required for a stop operation of the industrial robot.

A selection circuit generates a voltage V.sub.S of a switching terminal VS or a power supply voltage V.sub.CC, whichever is higher, in a common line. A regulator stabilizes a voltage V.sub.COML of a reference line at a level lower than a voltage V.sub.COM of the common line by a predetermined voltage difference ΔV. A charge pump circuit is provided between the common line and the reference line and steps up a voltage difference ΔV between the common line and the reference line. A rectifying element charges a bootstrap capacitor between a bootstrap terminal and the switching terminal, with an output voltage of the charge pump circuit.

A method and line interface filter apparatus to couple a drive or group of drives to a shared multiphase AC bus, including individual phase circuits having an inductor coupled between a respective bus and drive phase lines, a resistor coupled to the respective drive phase line, and a capacitor coupled between the resistor and a common connection of the capacitors of the individual phase circuits, where the capacitance of the capacitors is 5 to 15 times a per-phase equivalent capacitance of the drive or group of drives, and the resistance of the resistors is two times a damping ratio times a square root of a ratio of the filter inductance to the filter capacitance, where the damping ratio is greater than or equal to 1.0 and less than or equal to 2.0.

A high voltage direct current (HVDC) transmission system comprises a first terminal comprising a first voltage source converter (VSC) having a first and second VSC terminals and a first line commutated converter (LCC) having first and second LCC terminals; a second terminal comprising a second VSC having third and fourth VSC terminals and a second LCC having third and fourth LCC terminals; and a transmission line pair comprising a positive transmission line that couples the first VSC terminal and the first LCC terminal of the first VSC and the first LCC, respectively, to the third VSC terminal and the third LCC terminal of the second VSC and the second LCC, respectively, and a second positive line that couples the second VSC terminal and the second LCC terminal of the first VSC and the first LCC, respectively, to the fourth VSC terminal and the fourth LCC terminal of the second VSC and the second LCC, respectively.