Thyristor Switched Series Reactor for Electric Arc Furnaces

Supplementary series reactors are widely used in high power AC electric furnace to allow furnace operation with longer arcs, lower currents and lower electrode consumption. Such reactors can be switched off in the final stages of the melting process when the electric arc is stable and arc ignition is not of great concern. Bypassing the reactors with the use of conventional high voltage circuit breakers is not practical due to the maintenance problems related to the great number of operations. This paper describes an oil-immersed thyristor switch with a proper design for installation at a high voltage industrial substation to switch on and off the series reactor of the electric arc furnace circuit in order to improve furnace productivity. The concept of Thyristor Switched Series Reactors, TSSRs, can also be used to minimize or even replace on load tap changing of the furnace transformer.