The electrical power parameters of a 50 t/32 MVA electric arc furnace (EAF) in steelmaking at CIRIC Heavy Machinery Co Ltd were measured by electrical monitoring instrument to obtain 52 310 valid data. The results show that the power factors of reactor's primary side on load are all more than 0. 800 and during steelmaking the three phase voltage

current and power factors of power supply circuit are balance. Taking the working current at secondary side of transformer as independent variable

the nonlinear reactance model is established to get the electrical operation characteristics curves and determine the permissible range of working current at each voltage tap. The research results show that as the operation voltage tap of reactor modifies to tap 4 from original tap 3

the utilization ratio of EAF transformer shall increase by 7. 30%

and the power factor shall raise to 0. 841 from original 0. 812.