Arc stability criteria in AC arc furnace and optimal converter topologies

In this paper, the fundamental features of the arc stability in nonferrous metal AC arc furnace have been investigated, from the converter point of view. Due to the limited access to the measured arc data from the arc furnaces, the advanced arc simulations of magnetohydrodynamics (MHD) and the well known Cassie-Mayr arc model have been extensively used. The MHD based arc simulation has been validated in the subcomponent level, for the free burning arc set up in the laboratory. The arc simulation predicted the arc voltage for different currents with the accuracy which satisfies engineering requirements. It has been shown that the arc current steepness at current zero determines the arc stability, and the associated peak arc resistance can be used as its quantitative measure. Based on the presented insight into the AC arc stability, a converter topology solution which realizes an optimal arc stability has been proposed. The main results presented in this paper provide a design guideline for the future AC arc furnace converter topology developments.