Circuit arrangement for protection of the semiconductor switches while switching a mains converter bridge, which feeds energy back into an electrical mains system, in a DC intermediate-circuit converter

摘要

It is intended to specify a circuit arrangement for protection of the semiconductor switches during switching of a mains-commutated mains converter bridge (1.2) which feeds energy back into the mains (L1, L2, L3) and effectively protects the semiconductor switches both against overvoltages and against overcurrents, at a low cost and in an operationally reliable manner. The mains converter bridge (1.2) which feeds energy back into the mains is operated, without any circulating currents, with a second mains converter bridge (1.1) in a DC intermediate-circuit converter which is operated in the four-quadrant mode. The second mains converter bridge (1.1) is connected in parallel, but in the opposite polarity to said first mains converter bridge (1.2), is mains-commutated and draws energy from the mains. In the case of the DC intermediate-circuit converter, an intermediate-circuit capacitor (3), which is connected to the terminals of a self-commutated converter on the load side, is connected via at least one intermediate-circuit inductor (5.1, 5.2) to the two mains converter bridges (1.1, 1.2). According to the invention, that output of the two mains converter bridges (1.1, 1.2) which is on the intermediate circuit side is bridged (shorted) by a short-circuiting thyristor (2.1) which switches on in the event of an overvoltage and/or in the event of an overcurrent (Id) flowing via those terminals of the mains converter bridges (1.1, 1.2) which are on the intermediate circuit side. A load-relief diode (2.2), which is connected in the opposite polarity to the operating polarity of the intermediate-circuit capacitor (3), is connected in parallel with said intermediate-circuit capacitor (3). When the short-circuiting thyristor (2.1) is triggered, the [lacuna] by the intermediate-circuit capacitor (3) and the ... stores Original abstract incomplete. IMAGE