Melting method in an electric arc furnace and melting apparatus

An apparatus for melting metal material (M) comprising an electric arc furnace (11) and an electric power supply apparatus (31) of the electric furnace (11), which comprises:

• at least one transformer (15) connected to an electric power grid (16) for supplying a mains voltage (Ur) and a mains current (Ir), having a predefined mains frequency (fr), said transformer (15) being configured to transform said mains voltage (Ur) and said mains current (Ir) respectively into an alternating base voltage (Ub) and an alternating base current (Ib);
• a plurality of rectifiers (19) connected to the transformer (15) and configured to transform said base voltage (Ub) and said base current (Ib) into direct voltage and electric current;
• a plurality of converters (20) connected to said rectifiers (19) and configured to convert direct voltage and current into an alternating supply voltage and current;
• a control and command unit (21) configured to control and command the functioning of said converters (20) and to regulate said supply voltage (Ua) and supply current (Ia) over time;
• power regulating means (24a, 24b, 24c) associated with, and controllable by, said control and command unit (21) and configured to regulate the power supply of the electrodes (13a, 13b, 13c) in an independent manner one with respect to the other in order to vary the respective lengths of the electric arcs and regulate the distribution of the thermal power inside the electric furnace (11) so as to maximize the thermal power in different zones of the electric furnace (11) as a function of one or several of either the phase of the melting cycle, the position or quantity of the solid metal material (M) in the electric furnace (11), or the type of metal material (M) to be melted.

A melting method in an electric arc furnace (11) comprising:

• a step of loading solid metal material (M) into the electric furnace (11);
• a step of electric power supply of the electric furnace (11) and generation of an electric arc between at least one electrode (13a, 13b, 13c) and the metal material;
• a step of melting the solid metal material (M) to obtain molten material, wherein the power supply step comprises:
• the supply, by means of an electric power grid (16), of a mains voltage (Ur), and a mains current (Ir) having a predefined mains frequency (fr);
• the transformation, with at least one transformer (15), of the mains voltage (Ur) and mains current (Ir) into a base voltage (Ub) and a base current (Ib) which are selectively settable;
• the rectifying of the base voltage and base current with a plurality of rectifiers (19) to obtain a direct voltage and electric current;
• the conversion, with a plurality of converters (20), of the direct voltage and electric current into an alternating supply voltage (Ua) and an alternating supply current (Ia) which are selectively settable by means of a control and command unit (21) connected to said converters (20);
• the supply of the supply voltage (Ua) and supply current (Ia) to the at least one electrode (13a, 13b, 13c) of the electric furnace (11);
• the displacement of the position of the at least one electrode (13a, 13b, 13c) in at least one direction (X) transverse to a longitudinal axis thereof with respect to at least the walls of the furnace (11) and to the position of possible other electrodes (13a, 13b, 13c) in order to regulate the distribution of the thermal power inside the electric furnace (11) and maximize the electric power in different zones of the electric furnace (11) as a function of at least one of either the phase of the melting cycle, the position or quantity of the solid metal material (M) in the electric furnace (11), or the type of metal material to be melted.

An apparatus for melting metal material (M) comprising an electric arc furnace (11) and an electric power supply apparatus (31) of the electric furnace (11), which comprises:

• at least one transformer (15) connected to an electric power grid (16) for supplying a mains voltage (Ur) and a mains current (Ir), having a predefined mains frequency (fr), said transformer (15) being configured to transform said mains voltage (Ur) and said mains current (Ir) respectively into an alternating base voltage (Ub) and an alternating base current (Ib);
• a plurality of rectifiers (19) connected to the transformer (15) and configured to transform said base voltage (Ub) and said base current (Ib) into direct voltage and electric current;
• a plurality of converters (20) connected to said rectifiers (19) and configured to convert direct voltage and current into an alternating supply voltage and current;
• a control and command unit (21) configured to control and command the functioning of said converters (20) and to regulate said supply voltage (Ua) and supply current (Ia) over time;
• transverse movement means (26) configured to move the at least one electrode (13a, 13b, 13c) in at least one direction (X) transverse to a longitudinal axis of said at least one electrode (13a, 13b, 13c) with respect to at least the walls of the furnace (11) and the position of possible other electrodes (13a, 13b, 13c), in order to regulate the distribution of the thermal power inside the electric furnace (11) and maximize the electric power in different zones of the electric furnace (11) as a function of at least one of either the phase of the melting cycle, the position or quantity of the solid metal material (M) in the electric furnace (11), or the type of metal material (M) to be melted.