A DC power supply is disclosed which returns excessive regenerative energy to the AC line. The regenerative power supply generates a DC bus voltage from an AC power line and regulates the maximum DC bus voltage by returning to the AC power line energy supplied through the DC bus from the load. A conventional full wave rectifier bridge is used to rectify the incoming AC power line voltage into a DC bus voltage. A capacitor is connected across the DC bus to dampen high frequency transient voltages which may be present on the DC bus voltage. In anti-parallel with each of the rectifying diode circuits is a power transistor which is controllable to allow current conduction in a direction opposite to its associated rectifying diode. Control circuitry, associated with each of the anti-parallel transistors, senses excessive DC bus voltage and initiates conduction of the transistor when the AC power line phases are at the correct potential for receiving the regenerative energy.
A cut-off amplifier regulating the supply voltage of a load. This cut off amplifier comprises n bidirectional switches receiving input voltages which are alternatively positive and negative. These switches are connected to the load through a choke and to control means which place only one of the switches in the "on" state when the others are in the "off" state. The phase of the input voltage which is off (selected by the switches) depends on the comparison between the voltage applied to the load and a reference voltage.
An AC-to-DC power conversion by connecting GTO elements to the positive arms of a three-phase full wave bridge circuit and by repeating the mode of supplying power to a load from an AC power supply by controlling the GTO elements, and the mode of making the current flowing to the load flow back at the time of interruption of the power supply mode, when the power supply mode and the flow-back mode are switched over, overvoltage at the time of the switching is suppressed by simultaneously causing the power supply and flow-back currents to flow.
In an AC motor drive, a voltage-source inverter is provided in the DC-link thereof with a GTO switching arrangement which upon braking allows matching the voltage, current domains for the forward power and regeneration modes, the GTO devices being interrupted with a duty cycle selected in response to the voltage difference between the inverter DC input voltage and a constant reference voltage.
A method for directing the power of a d.c. voltage source between a three-phase mains and a d.c. circuit, which comprises the steps of employing a diode bridge comprising a plurality of first diodes to rectify a three-phase mains voltage to a d.c. voltge when power is flowing from the three-phase mains to the d.c. circuit, converting the d.c. voltage to a three-phase a.c. voltage, when power is flowing from the d.c. circuit to the three-phase mains, by means of transistors in parallel with the diodes, employing control means for controlling the transistors, forming control voltages for the control means by a plurality of second diodes from the three-phase mains in such manner that each the transistor is conductive during the conduction time of the respective diode in parallel therewith, and shortening the conduction times of the transitors, in order to reduce the power circulating in the d.c. circuit, by connecting Zener diodes in series with respective ones of the transistors.
A method and a device for protecting a matrix converter is disclosed. The matrix converter has nine bi-directional circuit-breakers which are arranged in a 3.times.3 switch matrix. A highest potential is detected from all input and/or output potentials or from all input potentials and at least one output potential. Bi-directional circuit-breakers of the matrix converter are controlled when a predetermined threshold value is exceeded. This arrangement protects the entire matrix converter from overvoltages. The converter can be produced easily and cost-effectively.
