In this research is proposed a control system used to obtain the maximum or a specific power of an electric arc. The plant taken into consideration is a three-phase electric arc furnace that is supplied from a special transformer. The process is modeled using an exponential model of the electric arc. By simulating the model in Matlab/Simulink environment the arc powers for five of the transformer's taps were obtained. Also by ranging the arc length value in a specific domain was obtained the optimal length to achieve the maximum power for a specific tap. In the closed-loop control system is used a fuzzy controller. In order to test the system performance the control system is tested in two cases. Fist case is at injection of disturbances in the process, the transformer is set on a specific tap and the set-point value is varied in a specific domain. The second case in when are injected disturbances in the process, the transformer tap is changed and the set-point value is kept constant at a power representing the maximum arc power for each of the transformer's tap.