Circuit arrangement for protection of the semiconductor switches when a mains converter bridge, which feeds energy back into an electrical mains power supply, switches over in a DC intermediate-circuit converter

摘要

The main Patent P 4322379 describes switching-over protection for two mains converter bridges, which are connected to the electrical mains power supply via radio suppression filters, are operated without any circulating current and are connected in parallel in opposition, in a DC intermediate-circuit converter operating in the four-quadrant mode. In this case, a short-circuiting thyristor which bridges over the terminals, on the intermediate-circuit side, of the mains converter bridges is triggered when the generated intermediate-circuit current or the input voltage on the mains side exceed upper limits. In order that the short-circuiting thyristor is not triggered in the case of mains converter bridges which are protected by input fuses on the mains side, in the event of external mains overvoltages and operation of the motor mains converter bridge, and in order that the fuses are thus not triggered, the rectified input voltage (UGmains) on the mains side is passed, according to the invention, via an AND gate (19) in addition to the evaluation of the generated intermediate-circuit current (IdG') for triggering of the short-circuiting thyristor, which AND gate (19) at the same time receives a signal (GEN) which indicates operation of the generator mains converter bridge. <IMAGE>