Abstract: A new control method is used to regulate the reactive power consumption of an electric arc furnace. Active and reactive power values are used space vector variables and serve as control parameter of the power source, which consists of a furnace transformer with current controllers and a booster transformer. This method helps maintain constant reactive power consumption, reduce flicker at the point of common coupling and minimize the disturbances in the power system.

Abstract: An electronic-controlled furnace transformer, which enables the reactive power, consumed by the furnace to be kept constant, thus reducing flicker. This is achieved by associating with a conventional power system of the electric arc furnace with current controllers and a booster transformer. By regulating the (reactive) power input with the help of the new control method, any disturbances in the power system can be reduced to a minimum.

Abstract: A power source for an arc furnace having an intermediate circuit transformer including a magnetic decoupled booster transformer and an AC main-driven converter. Such a power source comprises a current controller and a zero voltage switch. The current controller and the zero voltage switch are integrated in the intermediate circuit transformer. The zero voltage switch short-circuits the main reactance of the booster transformer whenever the current controller faces a current cut off and is blocked.

Abstract: The invention comprises a control system for Arc Welding for steady and pulsed direct current welding with a single three-phase bridge converter (1) For steady direct current welding, output DC voltage (V.sub.d) and current (1.sub.d) are varied through the tapping of transformer (2). Finer voltages can be obtained through the variation of firing angles .alpha. of the thyristors of the converter (1). The contemplated control system can also be used for pulsed DC current welding with an impured dynamic response with less effort. The background current, which lies between the maximum and minimum firing angle .alpha. of the thyristors of the converter (1), is set by the transformation ratio of the transformer (2) and the pulsed current is superimposed thereon through the relatively rapid changing of the firing angle .alpha..