Abstract: A three-phase voltage stiff convertor (SR) has two six-pulse partial convertors (SR1, SR2). The alternating voltage terminals of the partial convertors are connected to a transformer (TR) with the aid of which the resultant alternating voltage of the converter is formed as the difference between the alternating voltages of the partial convertors. Each partial converter has a separate direct voltage source (C1, C2). The converter has control members (SD) which control the two partial convertors which a mutual phase displacement alternating between +150.degree. and -150.degree..

Abstract: A drive equipment has an AC motor and a self-commutated static converter for transmitting electrical power between the motor and a network for driving and braking the motor. The equipment has braking resistors, each of which is connected between a DC terminal and an AC terminal of the converter. Connected in series with each braking resistor is a thyristor which acts to control the current through the braking resistor.

Abstract: A self-commutated inverter has two alternately conducting main branches which, in series with each other, are connected to a d.c. voltage source. The point of connection of the main branches constitutes the phase terminal of the inverter and a turn-off circuit is connected to this connection point. Each main branch includes a commutating inductor at least one of which is provided with an auxiliary winding. The auxiliary winding is connected in series with diodes means and this series connection is connected to the d.c. voltage source for feedback of surplus energy in a commutating circuit and symmetrization of commutating capacitor voltage.

Abstract: An electrical inverter with controllable output voltage comprises a three-phase self-commutated inverter bridge which is supplied from a d.c. voltage source. A reference signal generator generates a three-phase binary reference signal for controlling the shape of the curve of the output voltage of the inverter. This signal is modulated or mixed in a mixing stage with a binary pulse train having a controllable pulse-width ratio and a relatively high frequency. The output signal from the mixing stage is supplied to the inverter bridge in such a way that the output voltage of the inverter bridge corresponds to the product of the reference signal and the pulse train.

Abstract: A static convertor with forced commutation is connected between an alternating voltage network and a direct voltage network. A filter is connected in parallel with a smoothing capacitor on the DC side of the convertor. The filter consists of the series-connection of an inductor, a filter capacitor and two controllable semiconductor valves that are connected in parallel in opposed relation. The natural frequency of the filter is higher than the product of the frequency of the alternating voltage network and the pulse number of the converter. The valves are made to carry current in time with the fundamental tone of the AC component present in the direct current of the convertor. In this way, the variations of the direct voltage of the convertor, caused by the AC direct current component, may be practically eliminated.

Abstract: A DC convertor for converting power at a particular input voltage level to a higher or a lower voltage level and operable despite changes in the direction of power flux between the input and output voltage levels. Main switching thyristors operate in conjunction with turn-off thyristors, a commutation capacitor, magnetically coupled inductor windings and bypass diodes to define the magnitude and direction of the flow of current in the convertor and the voltage conversion ratio of the convertor.