Abstract: A circuit for controlling the power supplied to a load. The circuit includes a controlled self-conducting semiconductor switch (4) connected in-series with the load (2). Further, a first energy storage circuit (9a) is provided in-series with the load and includes a first energy storage element (6a) and a first rectifier (8a) connected in-series thereto. A controlled auxiliary switch (12) is also included in the circuit in-parallel fashion to the first energy storage element. A control sub-circuit (13) is provided near the energy storage element which is associated with the self-conducting semiconductor switch and the auxiliary switch. The control sub-circuit closes or opens the auxiliary switch when the voltage on the first energy storage element exceeds a predetermined first value or falls short of a predetermined second value.

Abstract: A circuit for controlling the power supplied to a load. The circuit includes a controlled self-conducting semiconductor switch (4) connected in-series with the load (2). Further, a first energy storage circuit (9a) is provided in-series with the load and includes a first energy storage element (6a) and a first rectifier (8a) connected in-series thereto. A controlled auxiliary switch (12) is also included in the circuit in-parallel fashion to the first energy storage element. A control sub-circuit (13) is provided near the energy storage element which is associated with the self-conducting semiconductor switch and the auxiliary switch. The control sub-circuit closes or opens the auxiliary switch when the voltage on the first energy storage element exceeds a predetermined first value or falls short of a predetermined second value.

Abstract: An inverter with a self-commutated pulse converter connected to the power mains and at least one self-commutated pulse converter connected to a load. The line-side converter is electrically connected to the load-side converter through a DC intermediate circuit. A line filter can also be connected before the self-commutated pulse converter on the line side. The disconnectable converter valves of the line-side and load-side converters are implemented as semiconductor switches with different circuit topologies and can operate at different pulse frequencies. Each of the line-side and load-side converters can be optimized for a desired pulse frequency, which saves cost and space.

Abstract: An inverter with a self-commutated pulse converter connected to the power mains and at least one self-commutated pulse converter connected to a load. The line-side converter is electrically connected to the load-side converter through a DC intermediate circuit. A line filter can also be connected before the self-commutated pulse converter on the line side. The disconnectable converter valves of the line-side and load-side converters are implemented as semiconductor switches with different circuit topologies and can operate at different pulse frequencies. Each of the line-side and load-side converters can be optimized for a desired pulse frequency, which saves cost and space.

Abstract: A method and apparatus directly regulate the output currents (i.sub.RX, i.sub.SX, i.sub.TX) of an inverter that feeds a predetermined number of induction machines. This method and apparatus is applicable to an inverter feeding one or more induction machines without rotational speed actual value sensors. The regulation is achieved by means of a secondary current control to which is supplied a current command variable system (i.sub.RW, i.sub.SW, i.sub.TW). According to the invention the current command variable system (i.sub.RW, i.sub.SW, i.sub.TW) is determined from the inverter output currents (i.sub.RX, i.sub.SX, i.sub.TX) and the state signals (S.sub.R, S.sub.S, S.sub.T) of the current switches of the inverter, from a calculation of the actual values of the active and reactive powers (P/U.sub.d, P.sub.q /U.sub.d) supplied to the motor, and a given rotational speed setpoint (n.sub.set), using field-oriented variables and simulating the actual rotational speed (n.sub.act).