Abstract: A contact monitoring unit is for a safety-critical triggering apparatus of a switching device, including a connection diagram arranged on a first circuit carrier medium for a triggering apparatus and triggering electronics arranged on a second circuit carrier medium. The contact monitoring unit includes redundant electrical connections that are monitored such that, even a failure of a redundant electrical connection is detected.

Abstract: An apparatus for regulating an electric arc furnace connected to a power supply system with at least one system phase that applies an AC voltage to a furnace electrode and an arc current for melting. A control loop device includes an electrical converter designed for negative feedback of an amplitude and/or frequency of the AC voltage to produce an amplitude and/or frequency of the arc current. The converter includes an input port having a system power supply connected thereto, and an output port having a melting furnace power supply and a primary circuit of a first transformer connected thereto, wherein a secondary circuit of the first transformer is connected to the arc furnace electrode. A primary coil of a second transformer is connected in parallel with the converter input port, and a secondary coil of the first transformer is connected in series with a secondary coil of the second transformer.

Abstract: An apparatus for regulating an electric arc furnace connected to a power supply system with at least one system phase that applies an AC voltage to a furnace electrode and an arc current for melting. A control loop device includes an electrical converter designed for negative feedback of an amplitude and/or frequency of the AC voltage to produce an amplitude and/or frequency of the arc current. The converter includes an input port having a system power supply connected thereto, and an output port having a melting furnace power supply and a primary circuit of a first transformer connected thereto, wherein a secondary circuit of the first transformer is connected to the arc furnace electrode. A primary coil of a second transformer is connected in parallel with the converter input port, and a secondary coil of the first transformer is connected in series with a secondary coil of the second transformer.

Abstract: From two path- or angle-dependent signals (A, B) of identical amplitude and period generated by an incremental generator (GS) which signals have a phase shift of 90.about. el. to each other a sequence signal .vertline.A.vertline./(.vertline.A.vertline.+.vertline.B.vertline.) dependent linearly on the path or angle is formed in that the generator signals (A, B) are rectified and a signal is formed in a converter (U1 ) corresponding to the quotient of the magnitude (.vertline.A.vertline.) of one of the two generator signals (A) to the sum of the magnitudes (.vertline.A.vertline.+.vertline.B.vertline.) of both generator signals (A, B). From the sequence signal the position within a particular quarter period is determined. Which quarter period this is in each instance is determined by an investigation of the position of the generator signals (A, B) with respect to each other.