Electric power supply device for electric arc furnace

Abstract

The invention relates to a power supply device (10) for an electric furnace (11), comprising at least one basic power supply module (20, 20A, 20B) having a first sub-module (21), a second sub-module (22) and a third sub-module (23), which are connected at inputs to a three-phase network (13) by means of respective transformers (24, 25, 26), respectively, and at an output, connected to a three-phase power supply line (32) configured to supply power to one or more electrodes (16) of the electric furnace (11).

Description

Technical Field

[0001] This invention relates to a power supply device for an electric furnace used in steelmaking applications for producing steel or in other fields for processing metals, glass materials, or other similar or comparable materials. The power supply device is particularly suitable for electric furnaces operating with alternating current and voltage. Background Technology

[0002] As is well known, electric furnaces used for smelting metals in steelmaking applications require a high-power, efficient power supply system.

[0003] It is also known that the smelting process includes several steps, typically including drilling into the metal material, smelting the material, and refining.

[0004] The power and electrical energy required by the electric furnace in the smelting process can vary greatly between different steps, so it is necessary to adjust the amount of electrical energy supplied each time.

[0005] In particular, the power absorbed by the electric furnace during the drilling of the metal material, or even during the smelting step, is usually greater than that required during the refining step, and varies greatly even within the same process step, depending on the type of material fed into the furnace.

[0006] Known power supply equipment for electric arc furnaces is connected to a power grid that is typically three-phase, and converts the voltage and current supplied by the power grid into voltage and current suitable for powering the electrodes of the electric arc furnace.

[0007] Known devices include: a rectifier that converts alternating current (AC) supplied by the power grid into direct current (DC); and one or more inverters that convert DC into AC to supply power to the electrodes.

[0008] The amount of electrical energy supplied to the electrodes is then regulated by appropriately controlling the inverter.

[0009] Typically, these inverters consist of one or more switches that are turned on and off at high frequencies. Therefore, if the amount of electrical energy supplied to the electric furnace needs to be changed dynamically, voltage fluctuations will occur even if multiple inverters are present. This will also have a reverse effect along the circuit, causing problems for the power grid.

[0010] In fact, these inverters can cause current modulation, generating current harmonics, which can be harmful if fed into the power grid.

[0011] Therefore, there is a need to improve a power supply device for DC user installations that can overcome at least one of the shortcomings of the prior art.

[0012] One object of the present invention is to provide an apparatus and method for supplying power to an electric arc furnace, which allows for efficient adjustment of the furnace's operation and power as required.

[0013] Another object of the present invention is to provide an apparatus and a method for implementing a method that allows for the regulation of the characteristics of the voltage and current supplied to an electric furnace (especially an electric arc furnace) to ensure the stability of the electric arc during various steps of the smelting process.

[0014] Another objective of this invention is to improve a balanced power supply device that minimizes any interference on the power grid side.

[0015] Another object of the present invention is to improve a power supply device having a modular structure, and thus being able to be adapted based on the requirements of the plant or the characteristics of the electric furnace to which it is applied.

[0016] Another object of the present invention is to improve a method for supplying power to an electric furnace, which allows for the supply of the required and necessary amount of electrical energy each time, while preventing possible interference with the power grid.

[0017] The applicant has designed, tested and implemented the present invention to overcome the disadvantages of the prior art and to obtain these and other objectives and advantages. Summary of the Invention

[0018] This invention is set forth and characterized by the independent claims. The dependent claims describe other features of the invention or variations thereof on the main inventive concept.

[0019] In accordance with the above objectives, an electric power supply device according to the present invention is provided, suitable for supplying power to an electric furnace used in steelmaking applications for producing steel, or in other fields for processing metals, glass materials or other similar or comparable materials.

[0020] The device includes at least one basic power supply module having a first submodule, a second submodule, and a third submodule, and a corresponding three-phase transformer for each submodule. The first submodule, the second submodule, and the third submodule are respectively connected to a three-phase power grid at their inputs via the corresponding transformers, and are connected at their outputs to a three-phase power supply line configured to supply power to the electrodes of the electric furnace.

[0021] According to the invention, each submodule includes, sequentially arranged one after another: a rectifier connected to a corresponding three-phase transformer, configured to convert three-phase AC current and voltage into DC current and voltage; a DC intermediate circuit or DC link configured to store electrical energy; and two inverters, each connected to the intermediate circuit and configured to convert DC voltage and current into AC supply voltage and current suitable for supplying different phases of the power supply line, wherein each submodule is configured to supply a pair of phases of the power supply line, and said pair of phases is different from the pairs of phases supplied by the other submodules. In this way, at least one basic power supply module has two connections at its output for each of the three phases of the power supply line.

[0022] This approach offers the advantage of balancing the voltage and current supplied to the electrodes, since at least one component for each phase is powered by two different submodules.

[0023] Each basic module is configured with three input phases and two output phases. This allows the three-phase current to be reorganized through the synergy of the three sub-modules, and also allows for the management of any failure of one of the sub-modules, since the two sub-modules are still sufficient to power the three phases in any case.

[0024] According to some embodiments, the rectifier includes a rectifier circuit for each phase, and all rectifier circuits are connected to the same DC intermediate circuit.

[0025] This allows the electrical energy supplied by the three phases to be centrally stored between the rectifier and inverter.

[0026] According to one aspect of the invention, each transformer includes a primary transformer and a secondary transformer, both having three-phase input and output terminals, wherein the input terminal of the primary transformer is connected to a phase of the power grid, and the output terminals of the secondary transformer are respectively connected to one of the rectifier circuits.

[0027] According to some embodiments, the phase portions of the primary and secondary windings of one or more transformers are connected in a star configuration and in part in a delta configuration to standardize the voltage and current within the base module (or each base module), respectively.

[0028] According to another aspect of the invention, the device includes a plurality of basic modules connected in parallel between the power grid and the power supply line, wherein each basic module receives three three-phase connections at its input and provides two three-phase connections at its output.

[0029] The number of basic modules can be multiplied as required, for example, doubled, tripled, quadrupled, etc., to obtain a total of six, nine, twelve, eighteen sub-modules, and so on.

[0030] This modular structure advantageously enables power supply equipment to adapt to equipment requirements: the total number of basic modules can be limited during the design phase based on the required scale and capacity needs, and the supplied power can be optimized and adjusted during the usage phase as required, for example, keeping only a portion of the basic modules in operation at any given time.

[0031] According to one aspect of the invention, at least one transformer, relative to at least another transformer associated with the same base module or possibly belonging to different base modules, has different connections between corresponding phases of the transformer primary and / or transformer secondary, differing in at least one of the following: star connection or delta connection, or phase shift between the corresponding phases.

[0032] According to another aspect of the invention, the phase portions of the corresponding primary and secondary windings of the transformer are connected in a star configuration and in part in a delta configuration.

[0033] According to another aspect of the invention, in the case of a star connection, the corresponding phase of at least one connection has a phase offset (out of phase) relative to the phase of another connection in one or another direction, including a phase angle between 10° and 20°.

[0034] Typically, if there are two or more basic modules, the phase connections of each transformer can adopt partial or completely different structures to achieve overall voltage and current balance and standardization in each sub-module and between one basic module and another.

[0035] According to another aspect of the present invention, a method for supplying electricity to an electric furnace includes: - Utilizing a three-phase power grid to supply alternating current and voltage with a predefined frequency; - Using a corresponding transformer, the alternating current and voltage are converted into three-phase alternating current and voltage suitable for powering at least a first sub-module, a second sub-module and a third sub-module of the base module, respectively, wherein the base module is configured to convert the electrical energy supplied by the transformer into electrical energy suitable for powering a three-phase power supply line; - Power is supplied to one or more electrodes of the electric furnace via the phase of the power supply line.

[0036] According to one aspect of the power supply method of the present invention, each submodule provides: rectification of the corresponding phase voltage and current to obtain a three-phase common DC voltage and current; temporary storage of energy by means of a DC intermediate circuit and isolation between the grid and the electrodes; and inversion of the DC voltage and current by means of two inverters to obtain corresponding phase AC voltage and current, the phase AC voltage and current being adapted to supply power to different phases of the power supply line respectively, wherein each submodule supplies power to a pair of phases of the power supply line, and the pair of phases is different from the pairs of phases supplied by other submodules, such that at least one base module provides two connections at the output for each phase. Attached Figure Description

[0037] These and other aspects, features, and advantages of the invention will become apparent from the following description of some embodiments given as non-limiting examples with reference to the accompanying drawings, in which: - Figure 1 This is a schematic diagram of a power supply device according to some embodiments described herein, which has a single base module comprising three sub-modules and is applied to an electric arc furnace; - Figure 2 for Figure 1 A schematic diagram of the circuit of a sub-module of the power supply equipment; - Figure 3 The diagram shows a power supply device based on some variations, which includes two basic modules and is applied to an electric arc furnace. - Figures 4a to 4f Show Figure 3 Some schematic examples of star and / or delta connections between the primary and secondary windings of a transformer in a power supply device.

[0038] For ease of understanding, the same reference numerals are used as much as possible in the accompanying drawings to denote the same common elements. It should be understood that elements and features in one embodiment can be readily combined or incorporated into other embodiments without further explanation. Detailed Implementation

[0039] We will now refer in detail to feasible embodiments of the invention, more than one example of which is illustrated in the accompanying drawings by way of non-limiting illustration. The wording and terminology used herein are also for the purpose of providing non-limiting examples only.

[0040] The embodiments described herein with reference to the accompanying drawings relate to an electrical power supply device 10 for an electric furnace 11, particularly an AC electric furnace.

[0041] The electric furnace 11 may be, for example, an electric arc furnace of the type that can be used in equipment 15 for steelmaking applications, which melts scrap steel or other metal materials by means of an electric arc ignited by two or more electrodes 16a, 16b, 16c (generally referred to as 16).

[0042] These electrodes 16 typically extend from the top of the furnace into the interior of the furnace chamber and can usually be moved toward or away from the material to be melted.

[0043] The electric furnace 11 can also be a submerged arc furnace.

[0044] The power supply equipment 10 includes power supply means 12, which is suitable for supplying electrical energy with predefined voltage, current and frequency values.

[0045] According to some embodiments, the power supply component 12 includes a three-phase power grid 13 configured to supply alternating current (AC) power. Figure 1 In the diagram, the letters R, S, and T represent three phases.

[0046] The power supply equipment 10 is connected to the power grid 13 and the electric furnace 11 by means of appropriate input and output connection components.

[0047] Input and output connection components typically include connection cables, connectors, etc.

[0048] The device 10 preferably has a modular structure and includes at least a first submodule 21, a second submodule 22 and a third submodule 23. These submodules are configured to receive three power lines at the input end, corresponding to an AC current and voltage phase R, S and T respectively, and to provide two AC current and voltage power lines at the output end, corresponding to one of the aforementioned phases R, S and T respectively.

[0049] According to some embodiments, each submodule 21, 22, 23 is powered by a different pair of phases RS, ST, RT than the other submodules 21, 22, 23.

[0050] In this way, although each module 20 provides three-phase power lines 13 and 32 at both its input and output, each sub-module 21, 22, and 23 helps to supply power to two of the aforementioned phases R, S, and T of the three-phase power supply line 32 at its output.

[0051] According to one aspect of the invention, three sub-modules 21, 22, and 23 jointly define a base module 20 of the device 10, which can be expanded N times according to requirements or parameters (e.g., the power required by the furnace 11, the required production capacity, the number of electrodes 16, etc.).

[0052] The quantity N can vary between 2 and 40, for example, 3, 4, 5, 6, 8, 10, 12, 18, 24, 36, or even other intermediate even or odd numbers.

[0053] Preferably, the number N of basic modules 20 is a multiple of 3.

[0054] As an example, Figure 3 The diagram shows two basic modules 20a and 20B, therefore there are a total of two first submodules 21A and 21B, two second submodules 22A and 22B, and two third submodules 23A and 23B. Clearly, by expanding the basic module 20 to a quantity N, the number of submodules 21, 22, and 23 of each type will also correspondingly increase to N.

[0055] According to some embodiments, each submodule 21, 22, 23 includes, one after another, the following: a rectifier 27 (configured to convert three-phase AC current and voltage into DC current and voltage), a DC intermediate circuit 28 or DC link shared by all phases, and two inverters 29, 30 (both connected to the intermediate circuit 28 and configured to convert DC voltage and current into AC voltage and current).

[0056] According to some embodiments, device 10 (i.e., each basic module 20) may include inductors 17, 18 connected between the respective inverters 29, 30 and the power supply line 32.

[0057] According to some embodiments, each rectifier 27 includes a corresponding rectifier circuit 27R, 27S, 27T for each phase R, S, T.

[0058] The rectifier 27, particularly each rectifier circuit 27R, 27S, 27T, can be made into a diode bridge or a thyristor bridge, and includes devices selected from diodes, silicon controlled rectifiers (SCRs), gate turn-off (GTO) thyristors, integrated gate commutated thyristors (IGCTs), metal-oxide-semiconductor controlled thyristors (MCTs), bipolar junction transistors (BJTs), metal-oxide-semiconductor field-effect transistors (MOSFETs), insulated gate bipolar transistors (IGBTs), or silicon carbide (SiC) devices.

[0059] According to some embodiments, each rectifier circuit 27R, 27S, 27T is connected to the same DC intermediate circuit 28.

[0060] The intermediate circuit 28 may include one or more capacitors 35 (e.g., capacitor banks) adapted to store energy and provide isolation between the rectifier circuits 27R, 27S, 27T and the inverters 29, 30, and also between the power grid 13 and the electrode 16.

[0061] According to some embodiments, inverter devices 29, 30 may include more than one switch 36, such as thyristors or transistors selected from the following types: gate turn-off (GTO) thyristor, integrated gate commutated thyristor (IGCT), metal-oxide-semiconductor controlled thyristor (MCT), bipolar junction transistor (BJT), metal-oxide-semiconductor field-effect transistor (MOSFET), insulated-gate bipolar transistor (IGBT), etc. Switch 36 may typically be associated with a corresponding diode (not shown).

[0062] According to some embodiments, each inverter device 29, 30 may also be configured to include multiple inverter circuits connected in parallel with each other, wherein the inverter circuits of the same inverter device 29, 30 are all connected to the same phase of the power supply line 32 at their output terminals.

[0063] The operation of the inverters 29 and 30 (and consequently switch 36) can be regulated by the control unit 40 to obtain a current with the desired intensity and frequency at the output.

[0064] The control unit 40 can be configured to manage and control the inverters 29 and 30 according to the specific steps of the smelting process performed in the electric furnace 11, so as to change one or more parameters of the current and voltage supplied to the electrode 16, such as intensity and / or frequency.

[0065] According to a feasible embodiment of the present invention, the control unit 40 may include or be connected to an adjustment device (not shown) configured to adjust the power supply frequency of the voltage and current supplied to the electrode 16 in order to obtain the situational variation of the reactance value of the power supply circuit of the electrode 16.

[0066] As an example, the regulating device may include a hysteresis modulator or a PWM (pulse width modulation) modulator.

[0067] According to some embodiments, the two inverters 29 and 30 of each submodule 21, 22, 23 provide corresponding AC current and voltage at the output end to supply power to different phases R, S, T of the three-phase power supply line 32.

[0068] The three-phase power supply line 32 can then be connected to the electric furnace 11 that needs to be powered.

[0069] Specifically, with three electrodes 16, each phase R, S, T can be connected to the corresponding electrodes 16a, 16b, 16c.

[0070] When the number of electrodes 16 is less or more, only some of the three phases R, S, T can be connected, or more than two phases can be connected to more than two electrodes 16.

[0071] The device 10 also includes corresponding transformers 24, 25, and 26 for each submodule 21, 22, and 23, which are configured to convert the three-phase primary AC voltage and current supplied by the grid 13 into three-phase secondary AC voltage and current with desired characteristics to power the corresponding submodules 21, 22, and 23 and ultimately power the electric furnace 11.

[0072] exist Figure 3 In the meantime, for ease of identification, transformers 24, 25, and 26, which are associated with each of the basic modules 20a and 20B respectively, are also marked with the corresponding letters A and B, in addition to the reference number.

[0073] Each transformer 24, 25, 26 has a corresponding three-phase output and input terminal, and includes a transformer primary 33 connected to the power grid 13 during use and a transformer secondary 34 connected to the rectifier 27.

[0074] Specifically, each output terminal of the transformer secondary 34 is connected to the corresponding rectifier circuits 27R, 27S, and 27T.

[0075] According to some embodiments, the phases R, S, and T of the primary winding 33 and the secondary winding 34 of the transformer can be connected in a star or delta configuration.

[0076] Preferably, the connection between the corresponding phases R, S, T of the primary transformer 33 and / or secondary transformer 34 of at least one transformer 24, 25, 26 is of a different type compared to at least one other transformer 24, 25, 26.

[0077] "Different types of connections" can mean either the following: at least one of the primary transformer 33 or the secondary transformer 34 of one of the transformers 24, 25, and 26 has a star connection for phases R, S, and T, while the other transformer has a delta connection for phases R, S, and T; or the following: both have the same type of connection (e.g., delta), but there is a certain angle of phase shift between each phase R, S, and T.

[0078] According to feasible embodiments, transformers 24, 25, and 26 associated with the same basic module 20 each have different connections to each other.

[0079] With several basic modules 20 set up, the connections between the input and output phases R, S, T of each transformer 24, 25, 26 can all be different from each other, or can be repeated in the desired order.

[0080] The different configurations of the phase connections of transformers 24, 25, 26 in a basic module 20 or between several basic modules 20 are preferably selected in such a way that they are different from each other at least in terms of connection type or phase angle between phases, so as to achieve current and voltage balance within a single basic module 20 and within the device 10 as a whole.

[0081] Figure 4 shows an example. Figure 3 The various connection configurations that can be adopted for the transformers 24A, 25A, 26A, 24B, 25B, and 26B of device 10. Although they are shown in a given order, it is clear that the order can be modified, or other configurations may be provided.

[0082] Figure 4a Transformer 24A is shown as an example, with the phases of its primary 33 and secondary 34 connected in a star configuration.

[0083] Figure 4b and Figure 4c Two transformers, labeled 25A and 26A, are shown as examples. The phases of the primary winding 33 of the transformer are connected in a star configuration, while the phases of the secondary winding 34 are connected in a delta configuration. In this example, the phases of the primary winding 33 are in phase with each other, while the phases of the secondary winding 34 are each offset by a phase angle of 2α.

[0084] Figures 4d to 4f Three transformers, labeled 24B, 25B, and 26B respectively, are shown as examples, with the phases of their primary winding 33 and secondary winding 34 connected in a delta configuration. In this example, the phases of the secondary winding 34 are in phase with each other, while the phases of the primary winding 33 of the two transformers 25B and 26B are phase-shifted by a phase angle α relative to the phase of transformer 24B in one direction or the other.

[0085] The phase angle α can, for example, be between 10° and 20°. This allows for better energy balance, thereby reducing any interference to the 13th terminal of the power grid.

[0086] Some embodiments described herein also relate to equipment 15, which includes a power supply device 10 according to the invention and an electric furnace 11, the electric furnace 11 being provided with one or more electrodes 16, each electrode being connected to phases R, S, T of a power supply line 32.

[0087] According to other embodiments, a method for supplying power to an electric furnace 11 is also provided, comprising: - AC current and voltage with a predefined frequency are supplied by a three-phase power grid 13; - Using corresponding transformers 24, 25, and 26, AC current and voltage are converted into three-phase AC current and voltage suitable for powering at least the first sub-module 21, the second sub-module 22, and the third sub-module 23 of the base module 20, respectively. The base module 20 is configured to convert the electrical energy supplied by transformers 24, 25, and 26 into electrical energy suitable for powering the three-phase power supply line 32. - Power is supplied to one or more electrodes 16, 16A, 16B, 16C of the electric furnace 11 via phases R, S, T of the power supply line 32.

[0088] According to one aspect of the invention, each submodule 21, 22, 23 is provided with: rectification of the corresponding phase voltages and currents R, S, T to obtain a DC voltage and current shared by the three phases R, S, T; temporary energy storage and isolation between the power grid 13 and the electrodes 16, 16a, 16b, 16c by means of a DC intermediate circuit 38; and inversion of the DC voltage and current by means of two inverters 29, 30 to obtain corresponding phase AC voltages and currents, respectively suitable for supplying power to different phases R, S, T of the power supply line 32.

[0089] According to another aspect of the method of the invention, each submodule 21, 22, 23 supplies power to a pair of phases RS, ST, TR, which is different from the pairs of phases supplied by the other submodules 21, 22, 23.

[0090] In this way, at least one basic module 20 provides two connections at the output for each of phases R, S, and T.

[0091] According to some embodiments, the method according to the invention provides for controlling the operation of inverters 29, 30 at least according to the type of electric furnace 11 to be powered or the characteristics of the smelting process performed therein, such as the type of material to be smelted, the required power, the number of electrodes 16 used, or different process steps.

[0092] According to some embodiments, the method provides: adjusting inverters 29, 30 by PWM regulation or hysteresis regulation.

[0093] According to other embodiments, in the presence of several basic modules 20, the method according to the invention can also provide: each time verifying the requirements of the equipment 15 or the characteristics of the electric furnace 11 or the material to be melted, and determining the characteristics of the voltage and current to be supplied to the electrode 16, and each time activating only all the basic modules 20 necessary and sufficient to supply a specific voltage and current.

[0094] Obviously, modifications and / or additions can be made to the power supply equipment 10 and method as described above without departing from the scope and range of the invention as defined by the claims.

[0095] In the following claims, the reference numerals in parentheses are for ease of reading only and should not be considered as limiting factors of the scope of protection defined in any particular claim.

Claims

1. A power supply device (10) for an electric furnace (11), comprising at least one basic power supply module (20, 20A, 20B), the basic power supply module having a first submodule (21), a second submodule (22), and a third submodule (23), the first submodule (21), the second submodule (22), and the third submodule (23) being connected at their input ends to a three-phase power grid (13) via respective transformers (24, 25, 26), and at their output ends to a three-phase power supply line (32) configured to supply power to one or more electrodes (16) of the electric furnace (11), characterized in that, Each of the submodules (21, 22, 23) includes, in sequence, a rectifier (27) connected to a corresponding three-phase transformer (24, 25, 26) configured to convert three-phase AC current and voltage into DC current and voltage; a DC intermediate circuit (28) or DC link configured to store electrical energy; and two inverters (29, 30), each connected to the intermediate circuit (28) and configured to convert DC voltage and current into AC supply voltage and current suitable for supplying different phases (R, S, T) of the power supply line (32), wherein each of the submodules (21, 22, 23) is configured to supply a pair of phases (RS, ST, TR) of the power supply line (32), and the pair of phases is different from the pairs of phases supplied by the other submodules (21, 22, 23), such that the at least one basic power supply module (20) has two connections at its output for each of the three phases (R, S, T) of the power supply line (32).

2. The device (10) according to claim 1, characterized in that, The rectifier (27) includes rectifier circuits (27R, 27S, 27T) for each of the phases (R, S, T), and all rectifier circuits are connected to the same DC intermediate circuit (28).

3. The device (10) according to claim 2, characterized in that, Each transformer (24, 25, 26) has a corresponding three-phase input and output terminal, and includes a transformer primary (33) and a transformer secondary (34). The transformer primary (33) is connected to the phase (R, S, T) of the power grid (13) through the corresponding input terminal, and the transformer secondary (34) is connected to each of the rectifier circuits (27R, 27S, 27T) through the corresponding output terminal.

4. The device (10) according to claim 3, characterized in that, At least one of the transformers (24, 25, 26) has a different connection between the corresponding phases (R, S, T) of the primary (33) and / or the secondary (34) of the transformer relative to at least one of the other transformers (24, 25, 26).

5. The device (10) according to claim 4, characterized in that, The connection is different in that it is a star connection or a delta connection, or a phase shift between the corresponding phases (R, S, T).

6. The device (10) according to claim 4 or 5, characterized in that, The phases (R, S, T) in the corresponding primary (33) and secondary (34) of the transformers (24, 25, 26) are connected in a star configuration and in a delta configuration.

7. The device (10) according to claim 4, 5, or 6, characterized in that, In the case of a star connection, each phase (R, S, T) of at least one connection has a phase offset relative to the phase (R, S, T) of another connection in one or the other direction, including a phase angle between 10° and 20°.

8. The device (10) according to any of the preceding claims, characterized in that, The device includes N basic modules (20, 20A, 20B), which are connected in parallel between the power grid (13) and the power supply line (32), where N is a value between 2 and 40.

9. The device (10) according to any of the preceding claims, characterized in that, The device includes a control unit (40) configured to manage and control at least the inverters (29, 30) according to the specific steps of the smelting process performed in the electric furnace (11) to change one or more parameters of the current and voltage supplied to the power supply line (32) each time.

10. An apparatus (50) for smelting metallic materials, comprising a power supply device (10) according to any one of claims 1 to 9 and an electric furnace (11), the electric furnace (11) being provided with two or more electrodes (16, 16A, 16B, 16C), each electrode being connected to a phase (R, S, T) of the power supply line (32).

11. A method for supplying electricity to an electric furnace (11), comprising: - By means of a three-phase power grid (13) supplying AC current and voltage with a predefined frequency, the corresponding transformers (24, 25, 26) are used to convert them into three-phase AC current and voltage suitable for powering at least the first sub-module (21), the second sub-module (22) and the third sub-module (23) of the base module (20), which is configured to convert the electrical energy supplied by the transformers (24, 25, 26) into electrical energy suitable for powering the three-phase power supply line (32); - Power is supplied to one or more electrodes (16, 16A, 16B, 16C) of the electric furnace (11) by means of phases (R, S, T) of the power supply line (32); The feature is that each of the sub-modules (21, 22, 23) provides: rectification of the corresponding phase voltage and current (R, S, T) to obtain a DC voltage and current shared by the three phases (R, S, T); temporary energy storage by means of a DC intermediate circuit (38) and isolation between the grid (13) and the electrodes (16, 16A, 16B, 16C); and inversion of the DC voltage and current by means of two inverters (29, 30) to obtain corresponding phase AC voltage and current, which are suitable for supplying power to different phases (R, S, T), wherein each of the sub-modules (21, 22, 23) supplies power to a pair of phases (RS, ST, TR) of the power supply line (32), and the pair of phases is different from the pairs of phases supplied by the other sub-modules (21, 22, 23), such that the at least one base module (20) provides two connections at the output for each of the phases (R, S, T).

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