Abstract: An air-cooled power converter with gate turn-off power semiconductors, is described in which the cooling capacity is such that the temperature of the gate turn-off power semiconductor does not exceed a critical temperature limit, the power converter having optimized heat sinks, at least some of which are thermally connected in parallel, and the power converter is designed to operate at a continuous load of 1 to 20 megawatts, preferably of 2 to 10 megawatts.

Abstract: A driving arrangement for rolling stands of a rolling mill, is described. The driving arrangement includes a control system which prescribes desired values for the rolling stands via control units, the rolling stands having at least one electric motor which is supplied with electric energy by a power supply system via at least one converter having turn-off power semiconductors. The converter has an air-cooled design. The cooling power is dimensioned such that the temperature of the turn-off power semiconductors does not exceed a critical temperature limit for continuous operation. The converter includes heat sinks which have an optimum design. At least some of the heat sinks are connected thermally in parallel.

Abstract: In chatter monitoring of twin drives of roll stands, vibrations of an upper drive and a lower drive are detected and monitored to determine whether a predetermined amplitude has been exceeded. If the amplitude has been exceeded, a chatter detection signal is generated. In order to prevent the chatter detection signal from being generated erroneously due to an operational pass vibrations, the frequencies of the vibrations of the upper drive and the lower drive are monitored for identity; when the frequencies are identical, the chatter detection signal is suppressed.