Abstract: A device for converting current and voltage between a first single-phase side and a second single- or multi-phase side is provided. At least two converter modules are connected between these sides. Each converter module has two converters interacting with one of the sides and an intermediate link interconnecting them. The converter modules are connected in series on the first side.

Abstract: At least one arc furnace and at least one induction furnace are connected to the same AC network, the induction furnace being connected via a controllable alternating voltage converter so as to permit compensation of active power fluctuations in the network caused by operation of the arc furnace and the induction furnace being designed to contain scrap for its inductive preheating before charging in the arc furnace.

Abstract: In a convertor plant for connection between a DC network and an AC network which includes at least one convertor group formed of two convertors with AC terminals for connection to the AC network and DC terminals for connection to the DC network, a reactor is connected on the DC side of one of the convertors and switches are provided for alternatively connecting the DC terminals of the convertor to the DC network in parallel with the other convertor or for connecting the reactor between the DC terminals of the convertor. Preferably the plant includes two or more convertor groups, each of which is provided with a transformer for connection to the AC network, and the transformers have different circuit angles for increasing the resulting pulse number of the plant.