Furnace power supply device, system for power supply of electric arc furnace or submerged arc resistance furnace, electric arc furnace or submerged arc resistance furnace, and operating method

Abstract

The present invention provides a novel furnace power supply device for supplying electrical energy to an electric arc furnace or a submerged arc resistance furnace. [Solution] A furnace power supply device (100) wherein the furnace power supply device (100) is connectable to a three-phase power network (110), the furnace power supply device (100) is connectable to at least one electrode (120) of the electric arc furnace or the submerged arc resistance furnace, the furnace power supply device (100) comprises a three-phase transformer (200) having a primary circuit for each phase and a secondary circuit for each phase, a rectifier circuit (210), and a smoothing circuit (220) connected to the rectifier circuit (210), wherein the three-phase transformer (200) is a phase-shift transformer (200), the smoothing circuit (220) has a capacitor bank connected in parallel to the rectifier circuit (210), and the furnace power supply device (100) comprises an inverter circuit (240) connected to the smoothing circuit (220).

Description

Technical Field

[0001] The present invention relates to a furnace power supply device, a system for supplying power to an electric arc furnace or a submerged arc resistance furnace, an electric arc furnace or a submerged arc resistance furnace, and an operating method.

Background Art

[0002] Metals, especially steel, are periodically melted and heated by an electric arc in a melting unit. These electrically operated melting units, especially electric arc furnaces or submerged arc resistance furnaces, operate with direct current, alternating current (AC), or three-phase AC current. Usually, for this purpose, at least one electrode protruding into the furnace vessel through the furnace lid is used, while other electrodes are provided corresponding to the first electrode or arranged at the bottom of the melting vessel.

[0003] An electric arc furnace or a submerged arc resistance furnace represents a very non-linear load, which means that the operation of the electric arc furnace or the submerged arc resistance furnace can cause undesirable electrical network distortions on the electrical supply network, especially flicker, harmonic currents, etc.

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present invention is based on the task of providing an improvement or an alternative to the state of the art.

Means for Solving the Problems

[0005] According to a first aspect of the present invention, this task is solved by a furnace power supply device for supplying electrical energy to an electric arc furnace or a submerged arc resistance furnace, - The furnace power supply device is connectable to a three-phase power network, - The furnace power supply device is connectable to at least one electrode of the electric arc furnace or the submerged arc resistance furnace, - The furnace power supply device is, - A three-phase transformer having a primary circuit for each phase and a secondary circuit for each phase, in particular having exactly one secondary circuit for each phase, -Rectifier circuit and, - Preferably, comprising a smoothing circuit connected to a rectifier circuit, - A three-phase transformer is a phase-shift transformer.

[0006] The following terms will be explained in more detail. First, in the context of this patent application, it is necessary to clearly state that, unless it is clearly evident from the context, or it is obvious to a person skilled in the art that it can only mean "exactly one," "exactly two," etc., or it is technically essential, indefinite articles and numbers such as "1," "2," etc. should generally be understood as "at least" information, i.e., "at least one," "at least two," etc.

[0007] In the context of this patent application, the term “in particular” should always be understood to mean the introduction of an optional preferential feature. This expression should not be understood as “that is.”

[0008] An "electric arc furnace" is a furnace that uses electrical energy provided and / or processed by a "furnace power supply device" to generate an electric arc in order to melt a metal mass, particularly scrap metal and / or scrap metal mixtures and / or directly reduced iron (DRI) and / or hot briquetted iron (HBI) and / or hot metal and / or flux material within the electric arc furnace. An electric arc furnace may be a ladle furnace.

[0009] An electric arc is formed between a charged material and an electrode. The charge in an electric arc furnace is heated by both the electric current passing through the charge and the radiant energy emitted by the arc. The electric arc temperature can reach approximately 3,000°C or higher.

[0010] A "submerged arc resistance furnace" is a furnace that uses electrical energy provided and / or processed by a furnace power supply to generate an arc between electrodes and the charged material, or to heat the charged material by resistance heating (Joule effect). The charged material is typically non-ferrous metals, ferrous alloys, waste recycling, slag, and slag cleaning.

[0011] An electric arc furnace or submerged arc resistance furnace may have a charge capacity of 1 ton or more, preferably 20 tons or more, and particularly preferably 50 tons or more. More advantageously, an electric arc furnace or submerged arc resistance furnace may have a charge capacity of 100 tons or more, preferably 200 tons or more, and particularly preferably 400 tons or more.

[0012] The furnace power supply unit can be connected to an electric arc furnace or a submerged arc resistance furnace, and in particular to the electrodes and / or furnace transformer of the electric arc furnace or submerged arc resistance furnace, by busbars that can be cooled with air, gas, water, or another suitable cooling medium different from water or gas, by cables or other suitable power transmission mediums such as graphite.

[0013] An "electrode" is a conductor used to contact a part of a circuit, particularly an electric arc furnace or submerged arc resistance furnace circuit, especially the non-metallic part of the circuit. In the case of an electric arc furnace or submerged arc resistance furnace, the non-metallic part of the circuit can correspond to the atmosphere inside the electric arc furnace or submerged arc resistance furnace.

[0014] The electrodes can be manufactured from high-density graphite and / or Wolfram. The electrodes may be designed to transmit electrical energy to form an arc between the tip and the charging material.

[0015] The electrodes may be pre-fired electrodes or self-fired electrodes (Soederberg electrodes), and / or extruded / composite electrodes which are a combination of a Soederberg electrode as a core and a pre-fired electrode, and / or hollow electrode systems which allow for filling of fine powder through a central hole (pre-fired, self-fired), thereby the selection of electrode type may depend on economic aspects such as electrode size, material / metallurgy used for manufacturing, and operating costs.

[0016] The electrodes of an electric arc furnace or submerged arc resistance furnace may be located at the top of the electric arc furnace or submerged arc resistance furnace. Preferably, electrodes located at the top are connected to height adjustment means, which can change the distance of the electrodes to the designated scrap and / or designated molten metal in the electric arc furnace or submerged arc resistance furnace. Such variations can be controlled and / or adjusted by an electrode adjuster.

[0017] In addition, the second electrode may be installed inside the furnace vessel of an electric arc furnace or a submerged arc resistance furnace, or it may be a component of the inner wall of the furnace vessel.

[0018] Optionally, the second electrode may also be positioned on top of the electric arc furnace or submerged arc resistance furnace, and preferably connected to height adjustment means.

[0019] It should be noted that electric arc furnaces or submerged arc resistance furnaces may also have three, four or more electrodes.

[0020] Electric arc furnaces or submerged arc resistance furnaces can be operated by direct current or alternating current.

[0021] In electric arc furnaces or submerged arc resistance furnaces operating on direct current, the electrodes are sometimes referred to as the anode and cathode. The anode can also be divided into several segments.

[0022] The anode, preferably the bottom electrode, is a metal and / or conductive material at the bottom of the furnace, and the arc is formed between the charged material and the cathode from above, preferably a cathode made of graphite or carbon.

[0023] An alternating current electric arc furnace or a submerged arc resistance furnace can be powered by a single-phase power supply or a polyphase power supply, particularly a three-phase power supply.

[0024] A "transformer" is a component that transfers electrical energy from one electrical circuit to another without a conductive connection between the two circuits. The transformer converts alternating current (AC) at the primary of the transformer to AC at the secondary of the transformer.

[0025] In the context of this description, the term transformer is synonymous with a three-phase transformer. In other words, it always means a three-phase transformer here. However, a three-phase transformer can also be understood as a combination of three single-phase transformers.

[0026] A transformer can have one or at least one primary circuit per phase and one or at least one secondary circuit per phase. In particular, the transformer can have exactly one secondary circuit per phase. The transformer can be a dry-type power transformer or an oil-cooled transformer. In particular, the transformer can also be cooled with other suitable cooling fluids or gases.

[0027] In particular, the secondary voltage can be 1,000 V, or less than 1,000 V, or more than 1,000 V.

[0028] The transformer can be a high-voltage - medium-voltage transformer that converts the high voltage at the primary of the transformer to a medium voltage at the secondary of the transformer.

[0029] The transformer can be a high-voltage - low-voltage transformer that converts the high voltage at the primary of the transformer to a low voltage at the secondary of the transformer.

[0030] A transformer can be a medium-voltage to medium-voltage transformer that converts a medium voltage in the primary of the transformer to a medium voltage in the secondary of the transformer.

[0031] A transformer can be a medium-voltage to low-voltage transformer that converts a medium voltage in the primary to a low voltage in the secondary. The transformer can be connected to a power supply network at its primary.

[0032] The high voltage can be 36kV or higher, preferably 60kV or higher, and particularly preferably 100kV or higher. More advantageously, the medium voltage can be 150kV or higher, preferably 200kV or higher, and particularly preferably 300kV or higher. The medium voltage can be 400kV or lower. More advantageously, the medium voltage can be 300kV or lower, preferably 200kV or lower, and particularly preferably 150kV or lower.

[0033] The intermediate voltage can be AC ​​of 1kV or higher or DC of 1.5kV or higher, preferably 2kV or higher, and particularly preferably 10kV or higher. More advantageously, the intermediate voltage can be 15kV or higher, preferably 20kV or higher, and particularly preferably 30kV or higher. The intermediate voltage can be 36kV or lower. More advantageously, the intermediate voltage can be 30kV or lower, preferably 20kV or lower, and particularly preferably 15kV or lower.

[0034] The low voltage can be 50V or higher, preferably 60V or higher, and particularly preferably 100V or higher. More advantageously, the low voltage can be 120V or higher, preferably 220V or higher, and particularly preferably 240V or higher. The low voltage can be 1,000V or lower, and particularly preferably 900V or lower. More advantageously, the low voltage can be 600V or lower, preferably 240V or lower, and particularly preferably 220V or lower. Preferably, the voltage level of an electric arc furnace or submerged arc resistance furnace can be defined according to IEC 60519-4.

[0035] A "phase-shift transformer" is a special type of transformer that can be configured to adjust the phase relationship between its primary circuit and its secondary circuit, making it possible to control the power flow on a three-phase power transmission network.

[0036] The phase angle of a three-phase transformer is a function of the vector group of the three-phase transformer.

[0037] Vector grouping, defined elsewhere by connection symbols, is an International Electrotechnical Commission (IEC) method for classifying the configurations of the primary windings, preferably high-voltage (HV) windings, and secondary windings, preferably low-voltage (LV) windings, of a three-phase transformer. Vector grouping indicates the winding configuration and the phase angle difference between them.

[0038] The vector group provides a simple way of showing how the transformer connections are configured. Different configurations are possible with respect to how the primary winding, preferably the MV winding, and the secondary winding, preferably the LV winding, are connected to each other. In particular, they can be connected to each other in a delta, star, or zigzag circuit, thereby allowing the primary winding, preferably the MV winding, and the secondary winding, preferably the LV winding, to be connected differently, resulting in a phase shift between the primary and secondary of a phase-shift transformer.

[0039] For example, a star MV winding and a delta LV winding can be combined to form a vector group, resulting in a 30-degree phase shift between the primary and secondary windings.

[0040] By optimizing the selection of vector sets, the total harmonic distortion injected into the network can be minimized.

[0041] Total harmonic distortion (THD) can be defined as the ratio of the root mean square (RMS) amplitude of a set of harmonic frequencies to the RMS amplitude of the first harmonic or fundamental frequency. This can be calculated using the following formula:

[0042]

number

[0043] During the ceremony, THD Y = Total harmonic distortion of signal Y Y h =h 次 Harmonic amplitude Y 1,RMS = RMS value of the amplitude of the fundamental frequency

[0044] Electrical loads on a three-phase power network during the operation of an electric arc furnace or submerged arc resistance furnace can be asymmetrical, causing harmonic distortion in the three-phase power network. The total harmonic distortion of the three-phase power network can be influenced by the selection of the vector set of the three-phase transformers. In particular, the total harmonic distortion caused in a three-phase power network can be minimized by using phase-shift transformers. A three-phase transformer may have one or more sets of secondary windings. If the transformer has several sets of secondary windings, the power may be divided among the existing sets of secondary windings. Different vector sets can be advantageously selected between the primary winding, preferably the MV winding, and each set of secondary windings, preferably the LV winding, so that power can be transmitted with different phase offsets. Depending on the number of sets of secondary windings, the individual phase shifts may be advantageously selected in such a way that the harmonic course of the phase results in a simultaneous increase in the number of pulses provided. The overall harmonics of the power network can also be improved by using two or more sets of secondary windings.

[0045] The portion of instantaneous power that results in net energy transfer in one direction is known as instantaneous "active power." The portion of instantaneous power that does not result in net energy transfer but instead oscillates between the power source and the load in each cycle due to stored energy is known as instantaneous "reactive power."

[0046] The phase angle may be affected by the phase-shift transformer within a range of primary-to-secondary phase shift of ±5° or less, preferably within a range of ±10° or less, and particularly preferably within a range of ±15° or less. Furthermore, the phase angle may be affected by the phase-shift transformer within a range of primary-to-secondary phase shift of ±20° or less, preferably within a range of ±25° or less, and particularly preferably within a range of ±30° or less. Furthermore, the phase angle may be affected by the phase-shift transformer within a range of primary-to-secondary phase shift of ±35° or less, preferably within a range of ±40° or less, and particularly preferably within a range of primary-to-secondary phase shift of ±45° or less. The above phase shift values ​​should be understood as being read between the nearest adjacent upper or lower inversion points of the primary and phase-shifted secondary AC waveforms.

[0047] Phase-shift transformers are a simple, robust, and reliable technology.

[0048] A "rectifier circuit" is an electrical device that converts alternating current, which periodically reverses direction, into direct current, which flows in only one direction.

[0049] The rectifier circuit can be a three-phase rectifier circuit.

[0050] The rectifier circuit may have a topology that includes and / or consists of diodes. A three-phase rectifier circuit may be an uncontrolled n×6 pulse diode rectifier circuit, in particular a 6-pulse diode rectifier circuit, a 12-pulse diode rectifier circuit, an 18-pulse diode rectifier circuit, and so on.

[0051] By using transistors and / or thyristors, rectifier circuits can be controlled or adjusted.

[0052] The rectifier can be protected by a high-current fuse.

[0053] Drawing a DC voltage from an AC power source within a power supply, particularly within a reactor power supply system, typically results in ripple voltage. Ripple voltage is a residual periodic fluctuation.

[0054] To smooth out the ripple voltage, the rectifier circuit is connected to a "smoothing circuit" that is configured to straighten out the ripple voltage.

[0055] The smoothing circuit may have a capacitor bank connected in parallel with the rectifier circuit.

[0056] The smoothing circuit may have an inductance bank connected in series with the rectifier circuit.

[0057] Electric arc furnaces or submerged arc resistance furnaces represent highly nonlinear loads. Such nonlinear loads can cause flicker and / or harmonic distortion in power networks connected to electric arc furnaces or submerged arc resistance furnaces.

[0058] Here, it is proposed to control the amount of total harmonic distortion (THD) using a phase-shift transformer, and in particular to reduce the amount of THD. This can significantly reduce grid interference, as THD can be minimized or prevented, and at the same time, improve the efficiency of energy use provided by the power network.

[0059] More preferably, the phase-shift transformer is proposed to be located between the three-phase power network and the rectifier circuit. Advantageously, this allows the furnace power supply to have a transition point between the power network and the DC bus. This makes it possible to achieve the multi-purpose utility of the furnace power supply proposed herein. In particular, according to a first modification, the furnace power supply can be applied in combination with a chopper circuit to supply power to a DC-fed electric arc furnace or a DC-fed submerged arc resistance furnace, or according to a second modification, it can be applied in combination with an inverter circuit to supply power to an AC-fed electric arc furnace or an AC-fed submerged arc resistance furnace. Therefore, existing systems do not possess the modularity and multi-purpose utility that can be achieved herein.

[0060] Thus, a particularly advantageous modular design for the reactor power supply system can be achieved, which does not require separate modifications to reduce total harmonic distortion.

[0061] To increase the power that can be supplied to the phases of an electric arc furnace or submerged arc resistance furnace, the above modifications of the furnace power supply device can be connected together by a parallel circuit. In the case of a DC-fed electric arc furnace or a DC-fed submerged arc resistance furnace, the furnace power supply devices can be connected in parallel to each other by cathode busbars and anode busbars.

[0062] In a parallel connection of multiple power supply devices, multiple groups consisting of phase-shift transformers and rectifiers can be connected in parallel, and these are connected to a common smoothing circuit. Furthermore, in a parallel connection of multiple power supply devices, multiple groups each comprising a phase-shift transformer, a rectifier, and a smoothing circuit can be connected in parallel.

[0063] When several reactor power supply units are connected in parallel, they are completely independent of each other but can be interconnected by a common electronic linkage and adjustment unit for individual control or adjustment. Furthermore, each reactor power supply unit in a parallel connection of several reactor power supply units may feature a different phase shift.

[0064] Depending on the number of furnace power supply devices connected in parallel, the individual phase shift of each device can be favorably selected in such a manner that the harmonic course of the phase results in a simultaneous increase in the number of pulses supplied. This can significantly reduce the degree of total harmonic distortion caused in the power network by the operation of an electric arc furnace or a submerged arc resistance furnace.

[0065] For the operation of a multiphase electric arc furnace or a multiphase submerged arc resistance furnace, in particular a three-phase AC-fed electric arc furnace or a three-phase AC-fed submerged arc resistance furnace, a parallel connection of one of the above modifications can be used to provide a third modification of the furnace power supply, where different sub-modifications are possible. Thereafter, each subset of a single furnace power supply or a parallel configuration of furnace power supplies can provide phases of a multiphase system. The phase shift between each phase of a multiphase system, expressed in radians and characterized by favorable harmonic courses of the phases, can be calculated by the following equation: PS=2 * PI / N During the ceremony, PS = Phase Shift (in radians) PI = 3.141592... N = Number of phases

[0066] In a configuration for operating a multiphase AC-powered electric arc furnace or a multiphase AC-powered submerged arc resistance furnace, each phase may be provided with an equal number of furnace power supply devices connected in parallel to one another.

[0067] The modularity and multi-purpose utility achieved here can further significantly reduce maintenance and overall spare parts inventory costs.

[0068] In a convenient embodiment, the primary of the transformer is connectable to a three-phase power network, and the secondary of the transformer is directly connected to a rectifier circuit.

[0069] According to a preferred embodiment, the furnace power supply system includes an electronic control unit connectable to an electronic linkage and adjustment unit, the electronic control unit being operably connected to a rectifier circuit and adapted to adjust the active power flow of the furnace power supply system.

[0070] The following terms will be explained in more detail. An "electronic control unit" is any electronic system adapted to receive signals, and / or store signals, and / or process signals, and / or control or adjust the reactor power supply in accordance with at least one signal.

[0071] The reactor power supply unit may include one or more sensors for providing information regarding harmonic distortion and / or flicker and / or the ratio of active power flow to reactive power flow in the power network. An electronic control unit may be operably connected to one or more such sensors, receive sensor signals, process them, and use them to control or adjust the reactor power supply unit.

[0072] The electronic control unit can be configured to control or adjust the rectifier circuit, and in particular to reduce or prevent harmonic distortion and / or flicker in the power network, and in particular to reduce flicker.

[0073] The electronic control unit can be configured to control or adjust the rectifier circuit, in particular to optimize the ratio of active power flow to reactive power flow in the power network.

[0074] The electronic control unit can be configured to control or adjust a chopper circuit or inverter circuit in a power network, particularly preferably by applying a pulse width modulation strategy algorithm, in order to reduce or prevent harmonic distortion and / or flicker, and in particular to reduce flicker.

[0075] The pulse-width modulation strategy algorithm (PWM) is a method for reducing the average power delivered by an electrical signal by effectively chopping the signal into discrete parts. The average voltage and / or current supplied to a load can be controlled by rapidly switching the power supply and load on and off. The longer the switch is on compared to the off period, the greater the total power supplied to the load. This results in a discrete signal to the load. A high PWM switching frequency is advantageous, especially if it is high enough not to affect the load. In other words, the smoother the resulting waveform perceived by the load, the better it is for the load. The speed or frequency at which the PWM switching frequency operates depends on the load.

[0076] An "electronic linkage and adjustment unit" is any electronic system adapted to communicate with one or more electronic control units. Preferably, the electronic linkage and adjustment unit is adapted to communicate with one or more electrode adjusters, particularly for the purpose of reducing harmonic distortion and / or reducing flicker, especially mitigating flicker and / or improving the power factor.

[0077] The electronic linkage and adjustment unit can be configured to take over higher-level control or adjustment of some connected regulators within the reactor power supply system, particularly one or more connected electronic control units and / or one or more electrode regulators.

[0078] The electronic coordination and adjustment unit can control or adjust the voltage setpoint of one or more reactor power supply devices.

[0079] The electronic coordination and adjustment unit can control or adjust the current setpoint of one or more reactor power supply devices.

[0080] The electronic coordination and adjustment unit can control or adjust the active power setpoint of one or more reactor power supply devices.

[0081] The electronic coordination and adjustment unit can control or adjust the reactive power setpoint of one or more reactor power supply devices.

[0082] The electronic coordination and adjustment unit can control or adjust the frequency setpoint of one or more reactor power supply devices.

[0083] The electronic coordination and adjustment unit can control or adjust the impedance or resistance setpoint of one or more reactor power supply devices.

[0084] The electronic coordination and adjustment unit can control or adjust the power factor of one or more reactor power supply devices, and in particular can improve the power factor.

[0085] The electronic linkage and adjustment unit can link single-electrode or multi-electrode adjusters of one or more AC furnace power supply devices.

[0086] By controlling and / or adjusting the rectifier circuit, harmonic distortion and / or flicker can be reduced.

[0087] In an optional embodiment, the furnace power supply device includes a chopper circuit connected to a smoothing circuit.

[0088] The following terms will be explained in more detail. A "chopper circuit" is an electronic switching circuit used to interrupt one signal under the control of another signal. A chopper circuit can be used to directly convert a fixed DC input to a variable DC output voltage.

[0089] Since the switching elements in this chopper circuit are either fully on or fully off, losses are low, and the chopper circuit can provide high efficiency. A high switching speed of 100 Hz or more, preferably 600 Hz or more, and particularly preferably 1,000 Hz or more, can be advantageously used to stabilize the electric arc and protect the furnace power supply from possible drift.

[0090] An "H-bridge" and / or "half-H-bridge" are well-known electronic circuits that switch the polarity of the voltage applied to a load.

[0091] The chopper circuit can feature a half-H bridge, and in particular, eight half-H bridges.

[0092] A chopper circuit can be used, particularly in relation to an electronic control unit, to reduce or prevent flicker in a power network, especially to reduce flicker, by controlling a control signal for switching the chopper circuit.

[0093] Optionally, the reactor power supply system includes an inverter circuit connected to a smoothing circuit.

[0094] The following terms will be explained in more detail. An "inverter circuit" is a power electronic device or circuit that converts direct current (DC) to alternating current (AC). The resulting AC frequency depends on the switching algorithm.

[0095] The inverter circuit can be controlled by applying a pulse width modulation strategy algorithm.

[0096] The inverter circuit may include an H-bridge, particularly a quadruple H-bridge.

[0097] Inverter circuits can be used, particularly in relation to electronic control units, to reduce or prevent flicker in power networks, especially to mitigate flicker, by controlling control signals for switching the inverter circuit.

[0098] According to a preferred embodiment, the rectifier circuit and / or chopper circuit and / or inverter circuit includes at least one semiconductor element containing silicon carbide.

[0099] The following terms will be explained in more detail. A "semiconductor device" includes the conductivity value between a conductor, such as metallic copper, and an insulator, such as glass. Semiconductor devices can be used for amplification, switching, and energy conversion.

[0100] The first embodiment of a semiconductor device is a diode.

[0101] A second embodiment of the semiconductor device is a transistor, preferably an insulated gate bipolar transistor (IGBT).

[0102] A third embodiment of a semiconductor device is a thyristor.

[0103] Advantageously, the semiconductor switch, particularly the transistor or thyristor, includes a switching speed of 100 Hz or higher, preferably 600 Hz or higher, and particularly preferably 1,000 Hz or higher.

[0104] Using silicon carbide can enable various advantages.

[0105] Silicon carbide can have a wide band gap of 3 eV or more, can be used stably up to a high operating temperature of 150°C, and has particularly high thermal conductivity, especially three times higher than that of silicon, which allows semiconductor devices made of silicon carbide to cool more effectively and quickly compared to other materials.

[0106] Furthermore, by using silicon carbide, it is possible to achieve a 10-fold higher electric field strength compared to silicon, with a higher maximum current and better efficiency in the semiconductor device.

[0107] Overall, it is possible to achieve rectifier and / or chopper and / or inverter circuits that have lower losses, can operate at higher ambient temperatures, and therefore reduce cooling requirements, and can operate at higher operating voltages and higher switching frequencies.

[0108] Furthermore, silicon carbide is particularly insensitive to radiation, especially electromagnetic radiation from electric arc furnaces or submerged arc resistance furnaces, compared to other semiconductor materials, particularly silicon. Therefore, when using silicon carbide, higher reliability and availability can be achieved in rectifier circuits and / or chopper circuits and / or inverter circuits.

[0109] By using silicon carbide semiconductor switches, particularly compact and / or efficient designs can be achieved.

[0110] Conveniently, the reactor power supply system is equipped with a three-phase disconnector for AC power.

[0111] The following terms will be explained in more detail. A "disconnector" is a switching element that ensures an electrical circuit is completely shut off for service or maintenance. A three-phase disconnector has three phases.

[0112] Optionally, the reactor power supply system may be equipped with a single-phase disconnector.

[0113] Preferably, the disconnector is located between the designated connection point of the electrode and the inverter circuit or chopper circuit.

[0114] The disconnector proposed here ensures that the furnace power supply can be switched to a voltage-free state, thereby allowing maintenance work to be performed safely.

[0115] Preferably, the disconnector connects the furnace power supply to ground potential when in the open position. This increases the safety of maintenance work.

[0116] Furthermore, in a system equipped with multiple reactor power supply units, it is possible to completely isolate each reactor power supply unit from the rest of the system without affecting the overall function of the system.

[0117] According to a preferred embodiment, the electric furnace power supply device comprises an electronic control unit connectable to an electronic linkage and adjustment unit, thereby the electronic control unit is adapted to control the active power of the furnace power supply device having a current loop and / or voltage loop and / or impedance loop and / or active power loop and / or hysteresis loop.

[0118] For this purpose, the electronic control unit may be configured to be operably connected to the rectifier circuit and / or the chopper circuit and / or the inverter circuit, and to be able to influence the respective controlled quantities.

[0119] Preferably, the electronic control unit uses an algorithm for a pulse width modulation strategy, preferably a synchronous, asynchronous, or interleaved pulse width modulation strategy.

[0120] According to a second aspect of the present invention, the task is solved by a system for supplying electrical energy to two electrodes of an electric arc furnace or a submerged arc resistance furnace. - The system can be connected to a three-phase power network. - The system can be connected to the electrodes of an electric arc furnace or a submerged arc resistance furnace. - The system comprises a plurality of furnace power supply devices according to a first aspect of the present invention, - Multiple reactor power supply units are connected to each other in parallel.

[0121] The advantage of the furnace power supply device according to the first aspect of the present invention is understood to be the direct transition to a system comprising the furnace power supply device according to the first aspect of the present invention, as described above.

[0122] In particular, connecting multiple reactor power supply units in parallel is advantageous in order to provide a higher connection load.

[0123] This approach automatically results in a greater number of phase-shift transformers, and therefore, advantageously, also provides a greater number of control options for reducing harmonic distortion.

[0124] In particular, it should be kept in mind that multiple phase-shift transformers in multiple reactor power supply devices may have different vector sets, and especially that each of them may have a different vector set.

[0125] In this way, each reactor power supply unit can provide a different phase shift, and the number of pulses provided by the system can also be increased. In short, harmonic distortion can be reduced in this manner.

[0126] The system may preferably have two furnace power supply devices, each having a different set of vectors, thereby doubling the number of pulses compared to a single furnace power supply device of the same design.

[0127] The system may preferably have three furnace power supply devices, each having a different set of vectors, thereby tripling the number of pulses compared to a single furnace power supply device of the same design.

[0128] The system may preferably have four furnace power supply devices, each having a different set of vectors, thereby allowing the number of pulses to be four times greater compared to a single furnace power supply device of the same design.

[0129] The system may preferably have five furnace power supply devices, each having a different set of vectors, thereby allowing the number of pulses to be five times greater compared to a single furnace power supply device of the same design.

[0130] The system may preferably have six furnace power supply devices, each having a different set of vectors, thereby increasing the number of pulses sixfold compared to a single furnace power supply device of the same design.

[0131] For example, in a system having six power supply devices, the first power supply device may preferably be configured to provide a phase shift such that the pulse lags 25° from the phase of the power network. Furthermore, the second power supply device may provide a phase shift such that the pulse lags 15° from the phase position of the power network. The third power supply device may provide a phase shift such that the pulse lags 5° from the phase of the power network. The fourth power supply device may provide a phase shift such that the pulse leads 5° from the phase of the power network. The fifth power supply device may provide a phase shift such that the pulse leads 15° from the phase of the power network. The sixth power supply device may provide a phase shift such that the pulse leads 25° from the phase of the power network.

[0132] Overall, a harmonic distribution of 36 different pulses, particularly those detectable behind the rectifier, can be achieved. This is especially advantageous for reducing harmonic distortion.

[0133] It should be clearly noted that this instruction can also be similarly adapted to different numbers of power supply devices.

[0134] It should be noted that the subject matter of the second embodiment can be advantageously combined with the subject matter of the prior embodiments of the present invention, either individually or cumulatively in any combination.

[0135] According to a third aspect of the present invention, the task is solved by a system for supplying electrical energy to multiple electrodes of an electric arc furnace or a submerged arc resistance furnace. - The system can be connected to a three-phase power network. - The system can be connected to multiple electrodes of an electric arc furnace or a submerged arc resistance furnace. - The system comprises a plurality of systems for supplying one electrode according to a second aspect of the present invention, Each system for supplying one electrode can be connected to one of several electrodes.

[0136] Here, it is proposed that a multiphase electric arc furnace or a multiphase submerged arc resistance furnace be combined with a plurality of systems according to a second aspect of the present invention, each system according to the second aspect of the present invention being connectable to exactly one electrode of the multiphase electric arc furnace or multiphase submerged arc resistance furnace.

[0137] In particular, the systems proposed herein can be advantageously used to supply power to a multiphase AC-fed electric arc furnace or a multiphase AC-fed submerged arc resistance furnace.

[0138] As described above, the advantages of a system for supplying electrical energy to one electrode of an electric arc furnace or submerged arc resistance furnace according to a second aspect of the present invention are understood to directly translate to a system comprising such a system according to a second aspect of the present invention.

[0139] It should be noted that the subject matter of the third embodiment can be advantageously combined with the subject matter of the prior embodiments of the present invention, either individually or cumulatively in any combination.

[0140] According to a fourth aspect of the present invention, the task is solved by a system for supplying electrical energy to multiple electrodes of an electric arc furnace or a submerged arc resistance furnace. - The system can be connected to a three-phase power network. - The system can be connected to multiple electrodes of an electric arc furnace or a submerged arc resistance furnace. - The system comprises a plurality of furnace power supply devices according to a first aspect of the present invention, -A first number of at least two reactor power supply devices are connected in parallel to each other and are connectable to the first electrode, - At least one reactor power supply device can be connected to the second electrode.

[0141] In particular, the systems proposed herein can be advantageously used to supply power to a multiphase AC-fed electric arc furnace or a multiphase AC-fed submerged arc resistance furnace.

[0142] The advantage of the furnace power supply device according to the first aspect of the present invention is understood to be the direct transition to a system comprising the furnace power supply device according to the first aspect of the present invention, as described above.

[0143] In a convenient embodiment, the system can be connected to three electrodes of an electric arc furnace or a submerged arc resistance furnace in a star or delta configuration.

[0144] In a preferred embodiment, the system comprises electrode adjusters, preferably one electrode adjuster for each electrode.

[0145] The following terms will be explained in more detail. The electrodes can be automatically raised and lowered by a positioning system and / or a handling system, the handling system of which can be an electric winch hoist or a hydraulic cylinder, etc. The position of the electrodes can be controlled and / or adjusted by an electrode adjuster. The electrode adjuster can pursue different purposes individually or in combination, in particular to maintain a nearly constant voltage and / or constant current and / or power input during the melting of the charge, even though the scrap may move under the electrodes when it melts. The arc length can be increased with increasing voltage supplied to the electric arc furnace or submerged arc resistance furnace.

[0146] In this way, the electrode regulator supports the system in reducing or preventing flicker in power networks, particularly in reducing flicker.

[0147] Conveniently, the system includes an electronic linkage and adjustment unit which is operably connected to an electronic control unit and / or an electrode adjuster, preferably an electronic linkage and adjustment unit which is operably connected to each electronic control unit and / or each electrode adjuster.

[0148] The electronic linkage and adjustment unit allows for the collectively use of numerous individual control and / or adjustment possibilities to advantageously achieve an overall objective, particularly in reducing or avoiding flicker in power networks, and preferably maximizing energy transfer for scrapping molten material.

[0149] It should be noted that the subject matter of the fourth embodiment can be advantageously combined with the subject matter of the preceding embodiments of the present invention, either individually or cumulatively in any combination.

[0150] According to a fifth aspect of the present invention, the task is solved by an electric arc furnace or submerged arc resistance furnace comprising a furnace power supply device according to a first aspect of the present invention and / or a system according to a second aspect of the present invention and / or a third aspect of the present invention and / or a fourth aspect of the present invention.

[0151] The advantage of the furnace power supply device according to the first aspect of the present invention and / or the system according to the second aspect, / or the third aspect, and / or the fourth aspect of the present invention is understood to be a direct transition to an electric arc furnace or submerged arc resistance furnace equipped with the furnace power supply device according to the first aspect of the present invention and / or the system according to the second aspect, / or the third aspect, and / or the fourth aspect of the present invention, as described above.

[0152] It should be noted that the subject matter of the fifth embodiment can be advantageously combined with the subject matter of the preceding embodiments of the present invention, either individually or cumulatively in any combination.

[0153] According to a sixth aspect of the present invention, the task is solved by a method for operating an electric arc furnace or a submerged arc resistance furnace, particularly an electric arc furnace or a submerged arc resistance furnace according to a fifth aspect of the present invention, wherein the ratio of active power flow to reactive power flow is controlled and / or regulated by influencing a control variable of the rectifier circuit, and in particular the reactive power flow is minimized by influencing a control variable of the rectifier circuit.

[0154] The advantages of the electric arc furnace or submerged arc resistance furnace according to the fifth aspect of the present invention are understood to be directly related to the method for operating the electric arc furnace or submerged arc resistance furnace according to the fifth aspect of the present invention, as described above.

[0155] It should be noted that the subject matter of the sixth embodiment can be advantageously combined with the subject matter of the preceding embodiments of the present invention, either individually or cumulatively in any combination.

[0156] The remaining harmonics can be further reduced or filtered by a reactor-capacitor bank connected in parallel to the reactor power supply unit on the same supply network.

[0157] The flicker value can be further reduced by a static reactive power compensator (SVC) or static synchronous compensator (STATCOM) system connected in parallel to the reactor power supply unit on the same supply network. In an optional embodiment, the reactor power supply unit cooperates with an SVC control system or a STATCOM control system. [Brief explanation of the drawing]

[0158] Further advantages, details, and features of the present invention will be described in the following description of embodiments. [Figure 1] A schematic diagram of the first embodiment of the reactor power supply device is shown. [Figure 2] A schematic diagram of a second embodiment of the reactor power supply device is shown. [Figure 3] A schematic diagram of a third embodiment of the reactor power supply device is shown. [Figure 4] A schematic diagram of one embodiment of a system for supplying electrical energy to one electrode of a DC-fed electric arc furnace or a DC-fed submerged arc resistance furnace is shown. [Figure 5] A schematic diagram of a first embodiment of a system for supplying electrical energy to a single-phase AC-powered electric arc furnace or a single-phase AC-powered submerged arc resistance furnace is shown. [Figure 6] A schematic diagram of a second embodiment of a system for supplying electrical energy to a single-phase AC-powered electric arc furnace or a single-phase AC-powered submerged arc resistance furnace is shown. [Figure 7] A schematic diagram of one embodiment of a system for supplying electrical energy to a three-phase AC-powered electric arc furnace or a three-phase AC-powered submerged arc resistance furnace is shown. [Modes for carrying out the invention]

[0159] In the following descriptions, the same reference number describes the same element and feature, and as a result, a description of one element made by referring to one figure is also valid for other figures, and consequently, repetition of each feature is omitted.

[0160] The reactor power supply device 100 in Figure 1 essentially consists of a transformer 200 which is a three-phase phase shift transformer 200, a rectifier circuit 210, a smoothing circuit 220 connected to the rectifier circuit 210, and an electronic control unit 230 connected to the rectifier circuit 210.

[0161] The reactor power supply device 100 can be connected to a three-phase power network 110. Furthermore, the reactor power supply device 100 can be connected to two electrodes 120.

[0162] According to one embodiment, the first electrode 120 may be positioned on top of a designated electric arc furnace or a designated submerged arc resistance furnace, and in particular may be connected to height adjustment means (not shown) operably connected to an electrode adjuster (not shown) for the first electrode 120. The second electrode 120 may be positioned inside a designated electric arc furnace or a designated submerged arc resistance furnace (not shown), and the second electrode may be operably connected to designated scrap (not shown) and / or designated molten metal (not shown) inside the electric arc furnace or submerged arc resistance furnace.

[0163] The electronic control unit 230 is configured to control and / or adjust the rectifier circuit 210.

[0164] The furnace power supply device 100 in Figure 2 further comprises an inverter circuit 240 or a chopper circuit 250, depending on whether the furnace power supply device 100 is intended for use with an AC-fed or DC-fed electric arc furnace, or an AC-fed or DC-fed submerged arc resistance furnace (not shown).

[0165] The inverter circuit 240 or chopper circuit 250 is operably connected to an electronic control unit 230 that controls or adjusts the inverter circuit 240 or chopper circuit 250.

[0166] The furnace power supply device 100 in Figure 3 further comprises a three-phase disconnector or circuit breaker 260 and / or a single-phase disconnector 270.

[0167] The furnace power supply device 100 can be connected to or disconnected from the three-phase power network 110 by a three-phase disconnector or circuit breaker 260. The furnace power supply device 100 can be connected to or disconnected from the electrodes 120 of an electric arc furnace or a submerged arc resistance furnace (not shown) by a single-phase disconnector 270. Preferably, when the disconnectors 260 and 270 are in the open position, the furnace power supply device is connected to ground potential. This increases the safety of maintenance work.

[0168] The system (not marked) for supplying electrical energy to two electrodes 120 of a DC-fed electric arc furnace or DC-fed submerged arc resistance furnace (not shown) in Figure 4 essentially consists of two or more furnace power supply devices 100 connected in parallel with each other.

[0169] The anode 124 of a DC-powered electric arc furnace or a DC-powered submerged arc resistance furnace (not shown) is connected to a plurality of furnace power supply devices 100 via an anode busbar (not shown). The cathode 122 of a DC-powered electric arc furnace or a DC-powered submerged arc resistance furnace (not shown) is connected to a plurality of furnace power supply devices 100 via a cathode busbar (unmarked).

[0170] Multiple reactor power supply devices 100 are connected to a three-phase power network 110.

[0171] Furthermore, multiple reactor power supply units 100 are connected to an electronic linkage and adjustment unit 300.

[0172] The electrode adjuster 310 is connected to the electronic linkage and adjustment unit 300 and is operably connected to the height adjustment means (not shown) of the cathode 122.

[0173] Anode 124 is located inside an electric arc furnace or submerged arc resistance furnace and is in electrical contact with designated scrap (not shown) and / or designated molten metal (not shown) within the electric arc furnace or submerged arc resistance furnace (not shown).

[0174] According to a modified embodiment (not shown) of a system for supplying electrical energy to at least two electrodes of a DC-fed electric arc furnace or DC-fed submerged arc resistance furnace shown in Figure 4, the system comprises two or more cathodes, each cathode connected to a combined or individual height adjustment means, each height adjustment means operably connected to a separate electrode adjuster. The anodes are located inside a designated electric arc furnace or designated submerged arc resistance furnace and are in electrical contact with designated scrap and / or designated molten metal within the electric arc furnace or submerged arc resistance furnace.

[0175] The system (not marked) for supplying electrical energy to two electrodes 120 of a single-phase AC-fed electric arc furnace or a single-phase AC-fed submerged arc resistance furnace (not shown) in Figure 5 essentially consists of two or more furnace power supply devices 100 connected in parallel with each other.

[0176] The first electrode 120 may be positioned on top of a designated electric arc furnace or a designated submerged arc resistance furnace, and in particular may be connected to height adjustment means (not shown) operably connected to an electrode adjuster 310 for the first electrode 120.

[0177] The second electrode 120 is located in an electric arc furnace or a submerged arc resistance furnace (not shown) and is operably connected to a designated scrap metal and / or designated molten metal within the electric arc furnace or submerged arc resistance furnace.

[0178] The electrode adjuster 310 is connected to the electronic linkage and adjustment unit 300 and is operably connected to the height adjustment means (not shown) of the first electrode 120 of a single-phase electric arc furnace or a single-phase submerged arc resistance furnace (not shown).

[0179] The system (not marked) for supplying electrical energy to two electrodes 120 of a single-phase AC-fed electric arc furnace or a single-phase AC-fed submerged arc resistance furnace (not shown) in Figure 6 presents two electrodes 120, each connected to a separate height adjustment means (not shown).

[0180] In this embodiment, height adjustment means bring both electrodes 120 closer to the designated scrap and / or molten metal in a single-phase AC-powered electric arc furnace or a single-phase AC-powered submerged arc resistance furnace from above. Each height adjustment means is operably connected to its respective electrode adjuster 310.

[0181] In Figure 7, three single-phase systems (not marked) for supplying electrical energy to one electrode 120 of an AC-fed electric arc furnace or a single-phase AC-fed submerged arc resistance furnace (not shown) are connected to a system (not marked) for supplying electrical energy to a three-phase AC-fed electric arc furnace or a three-phase AC-fed submerged arc resistance furnace (not marked), thereby supplying each single-phase system (not marked) to one electrode 120 of the three-phase AC-fed electric arc furnace or the three-phase AC-fed submerged arc resistance furnace (not marked).

[0182] For this purpose, all reactor power supply devices 100 are connected to a three-phase power network 110.

[0183] Furthermore, all reactor power supply units 100 are connected to a combined electronic linkage and adjustment unit 300.

[0184] The three electrodes 120 can be connected to each other in a star or delta configuration. [Explanation of Symbols]

[0185] 100 Furnace power supply device 110 Three-phase power network 120 electrodes 122 Cathode 124 anodes 200 Transformers / Phase Shift Transformers 210 Rectifier circuit 220 Smoothing circuit 230 Electronic control unit 240 Inverter Circuit 250 Chopper Circuit 260 Three-phase disconnector or circuit breaker 270 Single phase disconnector 300 Electronic Interoperability and Coordination Unit 310 Electrode Adjuster

Claims

1. A furnace power supply device (100) for supplying electrical energy to an electric arc furnace or a submerged arc resistance furnace, - The reactor power supply device (100) is connectable to a three-phase power network (110), - The furnace power supply device (100) is connectable to at least one electrode (120) of the electric arc furnace or the submerged arc resistance furnace. - The reactor power supply device (100) - A three-phase transformer (200) having a primary circuit for each phase and a secondary circuit for each phase, - Rectifier circuit (210), - comprising a smoothing circuit (220) connected to the rectifier circuit (210), - The three-phase transformer (200) is a phase-shift transformer (200), - The smoothing circuit (220) has a capacitor bank connected in parallel with the rectifier circuit (210), - A furnace power supply device (100) characterized in that the furnace power supply device (100) includes an inverter circuit (240) connected to the smoothing circuit (220).

2. The furnace power supply device (100) according to claim 1, characterized in that the primary of the transformer (200) is connectable to the three-phase power network (110), and the secondary of the transformer (200) is directly connected to the rectifier circuit (210).

3. The furnace power supply device (100) according to claim 1 or 2, characterized in that the furnace power supply device (100) comprises an electronic control unit (230) connectable to an electronic interoperation and adjustment unit (300), the electronic control unit (230) is operably connected to the rectifier circuit (210) and is adapted to adjust the active power flow of the furnace power supply device (100).

4. The furnace power supply device (100) according to claim 1, characterized in that the furnace power supply device (100) includes a chopper circuit (250) connected to the smoothing circuit (220).

5. The furnace power supply device (100) according to claim 1, characterized in that the rectifier circuit (210) and / or chopper circuit (250) and / or inverter circuit (240) include at least one semiconductor element containing silicon carbide.

6. The furnace power supply device (100) according to claim 1, characterized in that the furnace power supply device (100) comprises an electronic control unit (230) connectable to an electronic interoperation and adjustment unit (300), wherein the electronic control unit (230) is adapted to control the active power of the furnace power supply device (100) having a current loop and / or voltage loop and / or impedance loop and / or active power loop and / or hysteresis loop.

7. A system for supplying electrical energy to two electrodes (120) of an electric arc furnace or a submerged arc resistance furnace, - The system is connectable to a three-phase power network (110), - The system is connectable to the electrode (120) of the electric arc furnace or the submerged arc resistance furnace. The following characteristics: - The system comprises a plurality of furnace power supply devices (100) as described in claim 1, - A system characterized by the fact that the plurality of furnace power supply devices (100) are connected in parallel to one another.

8. A system for supplying electrical energy to multiple electrodes (120) of an electric arc furnace or a submerged arc resistance furnace, - The system is connectable to a three-phase power network (110), - The system is connectable to the plurality of electrodes (120) of the electric arc furnace or the submerged arc resistance furnace, The system comprises a plurality of systems for supplying one electrode (120) as described in claim 7, wherein each system for supplying one electrode (120) is connectable to one of the plurality of electrodes (120).

9. A system for supplying electrical energy to multiple electrodes (120) of an electric arc furnace or a submerged arc resistance furnace, - The system is connectable to a three-phase power network (110), - The system is connectable to the plurality of electrodes (120) of the electric arc furnace or the submerged arc resistance furnace, The following characteristics: - The system comprises a plurality of furnace power supply devices (100) as described in claim 1, - At least two reactor power supply devices (100) are connected in parallel to each other and are connectable to the first electrode (120), - A system characterized by the fact that at least one reactor power supply device (100) is connectable to a second electrode (120).

10. The system according to claim 7 or 9, characterized in that the system comprises one electrode adjuster (310), preferably one electrode adjuster (310) for each electrode (120).

11. The system according to claim 7 or 9, characterized in that the system comprises an electronic linkage and adjustment unit which is operably connected to an electronic control unit and / or an electrode adjuster (310), preferably each electronic control unit and / or each electrode adjuster (310).

12. An electric arc furnace or a submerged arc resistance furnace, characterized in that the electric arc furnace or the submerged arc resistance furnace comprises the furnace power supply device (100) described in claim 1 and / or the system described in claim 7 or 9.

13. A method for operating an electric arc furnace or a submerged arc resistance furnace, particularly the electric arc furnace or submerged arc resistance furnace described in claim 12, characterized in that the ratio of active power flow to reactive power flow is controlled and / or adjusted by influencing a control variable of a rectifier circuit (210), and in particular the reactive power flow is minimized by influencing the control variable of the rectifier circuit (210).

Images