Abstract: A crowbar device has a first terminal and a second terminal, the terminals being connectible to a medium to high impedance AC voltage source including a trigger circuit configured to output a trigger signal responsive to exceeding a threshold voltage across at least one trigger element of the trigger circuit; a positive-side signaling circuit and a negative-side signaling circuit configured to output a positive or a negative clamping signal, respectively, according to a positive-voltage or a negative-voltage signal, respectively, input from the trigger circuit; and a positive-side overvoltage clamping circuit and a negative-side overvoltage clamping circuit configured to control their respective semiconductor element to be in a conducting state, when the clamping signal from the corresponding signaling circuit is present, and configured to control their semiconductor element to be in a non-conducting state, when the corresponding clamping signal has not been present for a predetermined time period.

Abstract: A power conversion apparatus including a three-phase transformer having at least four three-phase windings, and three converter arms each configured by connecting one or plural unit converters each including a switching device and an energy storage element in series. A power source or a load is connected to a first three-phase winding of the transformer, three series circuits which connects second and third three-phase windings of the transformer, and the converter arms in series with each other are connected in parallel, the parallel connection point is a DC terminal, and a magnitude relationship between a coupling coefficient of the first and second three-phase windings, and a coupling coefficient of the first three- and third three-phase windings is equal to a magnitude relationship between a coupling coefficient of the fourth and second three-phase windings, and a coupling coefficient of the fourth and the third three-phase windings.

Abstract: A transistor driver includes an inductor coupled to a gate terminal of a transistor and a switching circuit coupled to the inductor and configured to charge a capacitance at a gate terminal of the transistor from a source via the inductor responsive to a first state of a control input, to block discharge of the charged capacitance responsive to a voltage at the gate terminal and to return charge from the charged capacitance to the source responsive to transition of the control input to a second state. The switching circuit may include a switch coupled in series with the inductor and the source and configured to conduct responsive to transition of the control input to the first state and a rectifier coupled in series with the inductor and the source and configured to block discharge of the charged capacitance responsive to the voltage at the gate terminal.

Abstract: An SCR firing circuit is provided which includes a plurality of opto-couplers, diodes, a capacitor and an SCR, utilized to control the AC power applied to a load, such as a vibratory feeder. In various embodiments of the invention, one or more opto-couplers act as solid state switches and also isolate a control signal from the AC line voltage. The capacitor is charged from an AC power source through the diode during a half cycle of the AC line voltage, and remains charged until the SCR is triggered. In response to a control signal rendering the opto-couplers conductive, the capacitor is discharged through the opto-couplers to fire the SCR and provide AC power to the load. A back-to-back SCR firing circuit is also provided which fires a first SCR when a line voltage is positive and which fires a second SCR when the line voltage is negative, which may be utilized to adjust the frequency of the application of power to the load independently of the frequency of the AC power supply.

Abstract: A dipole component with a controlled breakover sensitivity includes a main thyristor having its gate connected to its anode through a pilot thyristor, and a triggering transistor disposed in parallel with the pilot thyristor, the base of the triggering transistor being connected to the gate of the pilot thyristor.