Apparatus and method to electrically power an electric arc furnace

Electric power supply apparatus for an electric arc furnace comprising at least one electrode, said electric power supply apparatus being electrically connectable to a power network to supply to said electrode electric energy to generate an electric arc to melt a metal mass, said power network being a three phase electric network with three phases, each phase providing a network current, said network current being alternate current (AC), said apparatus comprising an electric regulation unit interposed between and electrically connected to the power network and to the electrode and configured to regulate at least one of a current or a voltage for powering said electrode, wherein said apparatus comprises at least one detection device interposed between the electrode and said electric regulation unit and configured to detect said at least one of the current or the voltage, a positioning device configured to move the at least one electrode nearer to/away from the metal mass to be melted and a controller electrically connected to said electric regulation unit, to said power network, and to said positioning device, said controller being configured to control said electric regulation unit and said positioning device, wherein said electric regulation unit comprises a converter device configured to convert the network current into the electric energy to generate the electric arc at said electrode, wherein said converter device includes a plurality of modules electrically connected in parallel with each other and each of said modules is electrically connected to all of said three phases of the power network, wherein each of said modules comprises three phase sub-modules, wherein each of said three phase sub-modules comprises (i) a straightening circuit configured to rectify and regulate the network current to generate a straightened current, (ii) an intermediate circuit configured to store direct current (DC) energy from the straightened current, and (iii) an inverter circuit configured to invert the straightened current from the intermediate circuit by regulating a frequency and an amplitude of a fundamental harmonic of another alternating current providing the energy to the electrode, wherein said apparatus comprises a Pulse Width Modulation regulator configured to regulate the switching frequency of said inverter circuits and their band occupation.