Abstract: A static circuit arrangement for the production of three-phase current, comprising a plurality of waveform generating stages arranged in cascade. Each stage is adapted to provide either a positive or negative voltage.The stages are controlled so that in the case of increasing a voltage from zero to a maximum (either positive or negative) the first stage is rendered conductive, then the second, third and so on until the nth stage is conductive together with all the other stages, and in the case of a voltage decreasing from a maximum to zero all the stages are conductive and these are rendered non-conductive one at a time starting with the nth, then (n-1)th and so on until the first stage is rendered non-conductive.The first stage comprises three amplifier circuits, one for each phase, whereas the second and successive stages each comprise a single circuit which is common for all phases of a voltage to be generated. Each circuit of the first stage has its own phase load, e.g. a motor winding connected thereto.

Abstract: A blocking circuit for thyristors comprises a DC power source coupled to a capacitor which is switched into a thyristor circuit by a switching transistor and auxiliary thyristor. A high power current pulse from the capacitor is applied to the thyristor for blocking purposes. A common blocking circuit may be switched into a plurality of thyristor circuits eliminating separate capacitors and power sources. In a second embodiment, a high power DC output voltage would be generated from a three phase current source by means of three full wave rectifiers coupled to achieve a charging process six times per cycle. This latter arrangement offers the possibility of saving the charging capacitor altogether as the rectified phases overlap with only a slight ripple.