Abstract: A new design method for high-impedance electric arc furnace transformer voltages and rated current is put forward. After the “reactor short-circuit”， in order to ensure electrical efficiency by maintaining the arc voltage at the peak value in foaming slag， and to make full use of the transformer capacity， the stepped voltage and rated current of the transformer should be properly designed. The design principle for stepped voltage and rated current is established considering the constraint conditions of foaming slag thickness，power factor and transformer capacity， which will increase the transformer utilization and arc power， and cut down the melting time. At the same time，the designs of the maximum and minimum secondary voltages and transformer capacity are introduced. The results of analyzing the theoretical operation and design parameters of a 80 t high-impedance arc furnace show that the optimum stepped voltage is 734V. Above 734V， the limiting factor of increasing arc power is the rated current.

Key words: high-impedance electric arc furnace, transformer capacity, transformer rated current, transformer secondary voltage, reactor short-circuit