Apparatus and Method to Electrically Power an Electric Arc Furnace

Electric power supply apparatus for an electric arc furnace comprising at least one electrode and electrically connectable to a power network to supply to said electrode electric energy to generate an electric arc to melt a metal mass, said apparatus comprising an electric regulation unit interposed 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 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 control and command unit electrically connected to said electric regulation unit, to said power network, and to said positioning device, said control and command unit configured to control said electric regulation unit and said positioning device and to carry out a first control of the electric arc by acting on the electric regulation unit and respectively a second control of the electric arc by acting on the positioning device, wherein said electric regulation unit comprises a converter device configured to convert electric energy from the power network into the electric energy to generate the electric arc at said electrode, and wherein said converter device includes a plurality of modules electrically connected in parallel with each other and with the power network, and each of the plurality of modules comprising a phase sub-module for a phase of a network current supplied by the power network, each phase sub-module comprising (i) a straightening circuit configured to straighten and regulate the phase of the network current to generate a straightened current, (ii) an intermediate circuit configured to store in direct current energy from the straightened current to create a separation between the power network and the electrode, and (iii) an inverter circuit including a multi-impulse commutation circuit and configured to invert the straightened current from the intermediate circuit by regulating a frequency and an amplitude of a fundamental harmonic of an alternating current providing the energy to the electrode.