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    • 专利摘要:
    Continuous intensity regulation device for an electric arc furnace. The present invention is directed to a device, an installation and a method for regulating the electric intensity in an electric arc furnace; In particular, the invention is directed to a device that regulates the intensity that circulates through the electrodes of the electric arc furnace and that makes it possible to avoid the circulation of short-circuit currents that could damage the electrodes, as well as the power cut by a device. protection that would stop the oven from operating. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2836000A1
    申请号:ES201931149
    申请日:2019-12-23
    公开日:2021-06-23
    发明作者:Guixot Manuel Visiers
    申请人:Fund Cener；
    IPC主号:
    专利说明:

    [0004] OBJECT OF THE INVENTION
    [0006] The present invention is directed to a device, an installation and a method for regulating the electric intensity in an electric arc furnace supplied with normally three-phase alternating current; In particular, the invention is directed to a device that regulates the intensity that circulates through the electrodes of the electric arc furnace and that makes it possible to avoid the circulation of short-circuit currents that could damage the electrodes, as well as the intervention of any element that produces the cut. of current by a protection device that would stop the furnace operation in case of short circuits.
    [0008] BACKGROUND OF THE INVENTION
    [0010] Electrode wear in an electric arc metallurgical furnace caused by short circuits in the tank is a well-known technical problem in steelworks using electric arc furnaces.
    [0012] These electric arc furnaces comprise three electrodes, one for each phase of the electrical system. For the scrap melting, the heat generated by the electric arc between the electrodes and the scrap itself in contact with the furnace mass is used. To power the furnace, a power transformer is normally used with the possibility of modifying the number of active turns, so it has the possibility of modifying the applied voltage in a stepwise manner. However, this number of positions is very limited, so the voltage variations that can be obtained are small and it is not possible to use it under load, so it is considered that the voltage applied to the furnace is constant during a certain process. .
    [0014] This fact makes it necessary to modify the impedance in order to control the melt current. The variation of the impedance is achieved by modifying the position of the electrodes, which is achieved by moving them closer to or away from the scrap metal; By bringing the electrodes closer to the material, the arc finds a path of lower impedance and the material melts through the Joule effect. As the scrap melts, the impedance goes modifying, so as the voltage is constant, the current varies and it is necessary to move the electrodes by means of mechanical elements to keep the current approximately constant within a range of given values, avoiding the tripping of the protection devices and interrupting the current to prevent a short circuit when the impedance is practically zero.
    [0016] The movement of the electrodes is carried out with mechanical drives that are very slow compared to the current variations, which makes it very difficult to effectively control the current that flows. This causes the wear of the electrodes and causes the impact of the electrodes with the scrap, which in turn causes breakage in them. Electrode breakage requires replacement to keep the oven running.
    [0018] Although to date the breakage of electrodes did not have a strong economic impact, the situation has changed with the increase in prices of graphite, which is the material from which the electrodes are generally made, so the protection of the electrodes has been become a priority problem for the metallurgical industry, which is already looking for technical solutions to solve the problem.
    [0020] DESCRIPTION OF THE INVENTION
    [0022] The present invention proposes a solution to the above problems by means of a device for continuous intensity regulation according to claim 1, an electric arc furnace installation according to claim 11 and a method of intensity regulation according to claim 12. In the Dependent claims define preferred embodiments of the invention.
    [0024] A first inventive aspect provides a device for continuous intensity regulation for an electric arc furnace, wherein for each phase
    [0026] the furnace comprises at least one furnace electrode to which a voltage Vh is applied, and through which an intensity Ih circulates, and
    [0028] the furnace is connected to a voltage source that generates a voltage Vt,
    [0030] characterized in that the device is configured to be connected in series between the voltage source and a furnace electrode, and comprises:
    [0032] - a switching means, configured to be connected in series between the voltage source and the at least one furnace electrode, and wherein the switching means are configured to enable or disable the phase of the regulation device to which it is connected;
    [0034] - a converter, connected in parallel to the switching means, so that the current flows through the converter when the switching means are open, and wherein the converter comprises,
    [0036] at least one inverter, with its alternating terminals configured to be connected in series between the voltage source and the at least one furnace electrode, wherein the at least one inverter is configured to convert direct voltage to alternating voltage,
    [0038] capacitive means connected to the DC terminals of the at least one inverter, between which a voltage Vc is maintained, and
    [0040] an energy sink connected in parallel to the capacitive means, wherein the energy sink comprises an electronic regulator and resistive means connected in series with the electronic regulator;
    [0042] - voltage measuring means for measuring voltage Vh, voltage measuring means for measuring voltage Vt, voltage measuring means for measuring voltage Vc and intensity measuring means for measuring current Ih, where the measurement means are configured to emit measurement signals SVh, SVt, Svc, Sí corresponding to the measured voltage and intensity values;
    [0044] - at least one control means configured to receive and process the measurement signals Svh, Svt, Svc, Si from the measurement means, and to emit control signals to the converter and to the switching means in response to a time variation of the intensity Ih that exceeds an intensity threshold Ih max as a consequence of the initiation of a short circuit induced by the electric arc, where the control means emit,
    [0045] a control signal S1 to the switching means to enable the device,
    [0047] a control signal S2 to enable the inverter, and
    [0049] an S3 control signal to enable the heatsink,
    [0051] so that the electronic regulator of the energy dissipator regulates the flow of current towards the resistive media by controlling the dissipated energy and maintaining the controlled direct voltage Vc between the inverter direct terminals, which converts the voltage Vc into a regulated alternating compensation voltage in phase and amplitude Vx, which in turn is subtracted from the voltage Vt of the voltage source, so that the voltage Vh applied to the furnace electrodes is reduced and therefore the intensity Ih does not exceed the threshold Ih max.
    [0053] Throughout this document, it should be understood that the voltage source, the furnace, and the continuous current regulation device are single-phase elements configured for use in single-phase or three-phase systems.
    [0055] Likewise, throughout this document reference will be made interchangeably to power or energy dissipated, the power dissipated being the amount of energy dissipated per unit of time.
    [0057] Voltage source is understood to be any means capable of supplying a suitable sinusoidal voltage to supply an electric arc furnace; In a particular embodiment, three voltage sources are grouped together to form a three-phase voltage source.
    [0059] In this document the terms electrode, furnace electrode and furnace electrode are to be understood as equivalents; it should also be understood that a three-phase furnace comprises at least three electrodes.
    [0061] It should be understood that the term DC bus refers to the set of elements connected to the DC terminals of the inverter.
    [0063] The alternating voltage generated by the continuous regulation device will also be called the compensation voltage or Vx, while the voltage between the inverter DC terminals will also be called the DC bus voltage or V c .
    [0065] To regulate the intensity that circulates through the electrodes of the electric furnace, the device generates a sinusoidal voltage controlled in amplitude and phase in series between the supply voltage source of the furnace and the electric arc furnace itself. This sinusoidal voltage, or offset voltage, is subtracted from the voltage supplied by the voltage source, so that for a given furnace impedance, the circulating current is modified by varying the offset voltage continuously.
    [0067] The compensation voltage generated by the device is produced between the AC terminals of the inverter, which on its DC side is connected in parallel to capacitive means that are charged as current passes through the inverter, and to an energy dissipator with resistive media and an electronic regulator, where the function of the heat sink energy is converting the excess energy generated into thermal energy that is dissipated into the environment.
    [0069] When applying the compensation voltage, the intensity of alternating current that circulates through the inverter causes the absorption of an energy that primes the capacitive means, raising the voltage Vc. This energy must be dissipated to maintain the voltage Vc, and protect the device, particularly the capacitive media, and for this function the electronic regulator and resistive media are used. As the voltage rises, the regulator connects more resistors, which reduces the total ohmic value of the resistance of the resistive media, and increases the dissipated power.
    [0071] The electronic regulator and the resistive elements allow controlling the DC bus voltage, V c . The inverter converts this voltage V c into an alternating voltage called the offset voltage Vx, controlled in phase and amplitude.
    [0073] In a particular embodiment, the energy dissipator is used to channel the excess energy towards other elements in which it can be used.
    [0075] The energy sink, the inverter and the switching means are enabled by means of control, which in response to voltage and current signals in the furnace and in the voltage source are capable of generating control signals to regulate in amplitude and phase compensation voltage.
    [0077] Advantageously, the intensity regulation device can be installed in an existing electric arc furnace system or in a new installation, and it makes it possible to avoid the problems caused by short circuits that occur in the furnace tub during its operation. In particular, the invention makes it possible to control the currents flowing through the furnace electrodes both to avoid damage to the electrodes by short-circuit currents and to prevent the short-circuit protection elements from frequently interrupting the operation of the furnace. Even more advantageously, in a particular embodiment three current regulation devices, one for each phase, are connected in series between three voltage sources and the electrodes of a three-phase furnace.
    [0079] In general, the present invention achieves that the circulating currents are more stable and remain centered on the nominal operating value of the furnace, achieving more stable and shorter melting processes, and improving the efficiency of the furnace. productive process.
    [0081] The current control also allows to solve the problem of the mechanical displacement of the electrodes to vary the impedance of the furnace; the continuous control of the current avoids having to move the electrodes abruptly, so the impacts of the electrodes against the scrap will be less, reducing the breakage of the electrodes or completely avoiding the damage to the ends of the electrodes.
    [0083] During the normal operation of the furnace, the switching means allow the passage of current through its branch, so that the current does not circulate through the parallel branch of the converter, so that the elements of the converter neither consume little energy, nor suffer degradation. This translates into a longer service life of the elements, thus the reliability of the device is very high.
    [0085] In a particular embodiment, the at least one inverter comprises at least one single-phase inverter bridge with semiconductor devices.
    [0087] Advantageously, an inverter bridge makes it possible to transform a direct current to a sinusoidal current, in particular an inverter bridge formed by semiconductor elements or devices makes it possible to obtain an efficient, compact inverter without mechanical elements susceptible to failure.
    [0089] In a particular embodiment, the at least one inverter comprises a bridge of four semiconductor devices, preferably insulated gate bipolar transistors with four anti-parallel connected diodes ( IGBT's).
    [0091] Advantageously, an inverter formed by IGBTs allows transforming a direct voltage to a sinusoidal voltage without harmonic components that damage the voltage sources, the furnace or the elements of the device.
    [0093] In a particular embodiment, the switching means comprise a switch and configured to disable the device, and a static bypass switch and configured to enable or disable voltage regulation on load instantaneously, where the switch and the static switch of bypass are connected in parallel with each other.
    [0095] Advantageously, the switch makes it possible to enable or disable the power regulation device. intensity without physically disconnecting it from the installation, for example to carry out maintenance tasks; the static bypass switch allows to enable or disable the operation of the regulation device while the oven is in operation and instantaneously. During normal operation, the switch will be normally open, and the static bypass switch will be normally closed.
    [0097] In a particular embodiment, the switch is one of the following list: an automatic switch, a load switch, a motorized vacuum disconnector.
    [0099] Advantageously, the switch can be manually actuated by an operator or it can be actuated by an external control signal, either on load or empty.
    [0101] In a particular embodiment, the static bypass switch comprises thyristors, IGCT's, GTO's and / or IGBT's.
    [0103] Advantageously, the static bypass switch comprises a specific type of semiconductor device depending on the desired response speed.
    [0105] In a particular embodiment, the static bypass switch comprises an auxiliary switching circuit configured to interrupt the current on load. Advantageously, the auxiliary circuit, comprising thyristors, capacitors and inductances, makes it possible to cancel the current flowing through the semiconductor devices of the static bypass switch thanks to the current generated by the discharge of the capacitors.
    [0107] In a particular embodiment, the electronic regulator comprises semiconductor devices of the IGBT type.
    [0109] Advantageously, the response speed of the IGBT allows to carry out a very fast control that manages to maintain the DC voltage of the DC bus in response to control signals that enable the electronic regulator.
    [0111] In a particular embodiment, the resistive means comprise a plurality of resistors with different electrical resistance values, the control means being configured to emit a control signal S4 to enable or disable a control of the electronic regulator that selectively connects at least one resistance of the plurality of resistors .
    [0112] Advantageously, the resistive means make it possible to regulate the amplitude of the DC bus voltage by varying the total resistive load connected in series with the electronic regulator.
    [0114] In a particular embodiment, the control means act on at least one phase of the device.
    [0116] In a particular embodiment, the device comprises respective secondary control means to enable or disable the elements of the switching means, of the converter and / or of the energy sink, wherein the secondary control means are configured to operate in response. to the signals S1, S2 and / or S3 of the control means, signals S1, S2 and / or S3 emitted in turn by the control means in response to the measurement signals SVh, SVt, Svc, Si.
    [0118] Advantageously, the control means only emit signals to enable or disable the controlled elements of the device, in particular the switching means, the converter and the energy sink, and the secondary control means generate the signals required to control each of the constituent elements of the switching means, the converter and the energy sink. In a particular embodiment, the secondary control means are capable of emitting firing pulses to the semiconductor devices of the switching means, of the converter and of the energy sink.
    [0120] Advantageously, the control means receive signals, process and emit control signals from each of the phases. In a particular embodiment, the control means emits control signals for three phases simultaneously, in particular it emits control signals to enable three phases of the switching means. In this way, it is achieved that before the appearance of a short-circuit current in one phase, the device can react quickly before the short-circuit passes to the remaining phases.
    [0122] In a second inventive aspect, the invention provides a three-phase electric arc furnace installation, comprising a three-phase voltage source with at least three voltage sources, a three-phase electric arc furnace with at least three furnace electrodes, and at least a device for continuous intensity regulation according to the first inventive aspect for each of the three phases .
    [0123] In a particular embodiment, the control means are common for the three phases of the installation.
    [0125] In a third inventive aspect, the invention provides a continuous intensity regulation method for an electric arc furnace with a intensity regulation device according to the first inventive aspect, comprising the following steps:
    [0126] - provide a regulation device for each phase connected in series between the voltage sources and the furnace electrodes;
    [0127] - for each phase, when the furnace is in operation, the voltage measurement means measure the voltages Vh, Vt, Vc and the intensity measurement means measure the current Ih, and continuously emit measurement signals SVh, SVt , Svc, Yes to the means of control;
    [0128] - for each phase, if the temporal variation of the current Ih increases above a threshold value Ih max, the control means:
    [0129] • emit a signal S1 to open the switching means and enable the device;
    [0130] • depending on the measurement signals Svh, Svt, Svc, Si, they emit a control signal S3 to the energy sink;
    [0131] • for each phase, the control means emits a control signal S2 to the inverter,
    [0132] in such a way that for each phase the electronic regulator of the energy dissipator controls the flow of current towards the resistive media, controlling the energy dissipated and maintaining a controlled direct voltage V c between the direct terminals of the inverter, which converts the voltage VC into a voltage phase and amplitude regulated alternating compensation Vx, which in turn is subtracted from the voltage Vt of the voltage source, so that the voltage Vh applied to the furnace electrodes is reduced and consequently the current Ih does not exceed the threshold Ih max .
    [0134] Advantageously, the continuous intensity regulation method makes it possible to avoid the passage of short-circuit currents through the oven electrodes, ensuring that the tripping of the protections does not constantly interrupt the oven process and avoiding the deterioration of the electrodes caused by impacts resulting from the control. by sudden displacement of the electrodes.
    [0136] All features and / or method steps described in this specification (including
    [0139] claims, description and drawings) may be combined in any combination except combinations of such mutually exclusive features.
    [0141] DESCRIPTION OF THE DRAWINGS
    [0143] These and other characteristics and advantages of the invention will become more apparent from the detailed description that follows of a preferred embodiment, given solely by way of illustrative and non-limiting example, with reference to the accompanying figures. .
    [0145] Figures 1a-1b These figures show two embodiments of the intensity regulation device connected in series with the voltage generator and the furnace, for a single-phase system and for a three-phase system.
    [0146] Figure 2 This figure shows the single-phase circuit connected in series with a furnace electrode.
    [0147] Figure 3 This figure shows the device converter.
    [0148] Figure 4 This figure shows the device with its control circuit and its operational connections.
    [0149] Figure 5 This figure shows examples of waveforms for various relevant quantities.
    [0151] DETAILED EXHIBITION OF THE INVENTION
    [0153] Figure 1 shows a set of three current regulation devices (1) connected in series between a three-phase source and a three-phase furnace. The three-phase source shown is equivalent to a set of three alternating single-phase voltage sources (9); generally the three-phase source comprises a three-phase transformer, not shown in the figures, to adapt the supply voltage of the network to the working voltage of the furnace. Additionally, the three-phase source comprises a series of protection devices, not shown in the figures, which are common in this type of installation, especially switches configured to interrupt the current against a short-circuit current, for example, a magnetothermic switch.
    [0155] The three-phase furnace, in addition to other elements that allow the metal to melt, such as the tank, comprises at least three furnace electrodes (8); These electrodes are normally made of graphite, and include a mechanical drive that allows the distance to be varied. between the end of the electrodes (8) and the material that is melting in the tank.
    [0157] The regulation device (1) is configured to be connected in series between a voltage source (9) of a three-phase source and an electrode of the furnace (8), for the simplicity of its mounting on the installation of an existing furnace, and to facilitate both the control response and the intensity regulation. The series connection is made through some connection terminals (1.1) of the device. The intensity regulation must be carried out individually for each phase, since generally the short circuit will not occur simultaneously in the three electrodes of the furnace (8). For this reason, in each three-phase installation, three devices (1) that can work independently must be installed, and as shown in Figure 2, each of the phases in turn comprises switching means (2) and a converter ( 3) which is the element that properly regulates the intensity.
    [0159] The switching means (2) and the converter (3) are connected in parallel with each other to enable or disable each phase of the device (1) separately; that is, the change of state of the switching means (2) allows the current to selectively flow through the converter branch (3) and the intensity regulation begins.
    [0161] The switching means (2) can have different configurations, depending on the characteristics and needs of the installation, specifically depending on the power of the furnace installation and the speed of response required. Preferably, the switching means (2) will act to enable the three phases.
    [0163] In a particular embodiment, the switching means (2) comprise a switch (2.1), or main switch, to disconnect the device to carry out maintenance operations, although not necessarily capable of interrupting the load current; in this embodiment the switch (2.1) is an automatic switch type element. In another embodiment, the switch (2.1) is a vacuum disconnector or a load switch; These elements have the capacity to interrupt the load current, but their response time makes them poorly suited for the type of regulation required by the present invention.
    [0165] Therefore, as a complement to the switch (2.1), a static bypass switch (2.2) connected in parallel with the switch (2.1) is required; The static bypass switch (2.2) is configured to interrupt the current instantaneously when the initiation of a short circuit, so it must be an element capable of working with high powers and with a high response speed. In one embodiment, the static bypass switch (2.2) comprises a series of semiconductor devices capable of interrupting the load current when they receive an opening signal S1 from the processing means. The static bypass switch (2.2) in some embodiments is made up of thyristors, IGCT's, GTO's, IGBT's or a combination of them. If the selected semiconductor devices or their configuration do not allow the circulating current to be interrupted by themselves in the time required by the application, the static bypass switch (2.2) includes an auxiliary switching circuit, or secondary control means, formed by inductances, auxiliary capacitors and thyristors; The capacitor, previously charged, is discharged when the auxiliary thyristors are triggered, providing an intensity that cancels the intensity that circulates through the semiconductor devices of the static bypass switch (2.2), which causes it to block as it passes through zero.
    [0167] During the normal operation of the furnace (8), the switch (2.1) is open, and the static bypass switch (2.2) is closed, so that the current flows only through the branch of the switching means (2) until the static bypass switch (2.2) receives the opening signal S1 to open the branch or branches corresponding to the switching means (2) and make the current pass through the branch or branches of the converter (3). The switch (2.1) is configured to operate when the device (1) has to be disabled, for example to carry out maintenance operations on the installation.
    [0169] Figure 2 shows the converter (3) connected in parallel with the switching means (2), the converter (3) formed by an inverter (3.1) and a power sink (4). The function of the inverter (3.1) is to switch the DC bus voltage from DC to AC, which is kept constant by the energy sink (4).
    [0171] The inverter (3.1) is shown in Figure 3 as a generic inverter with AC terminals (3.1.1) and DC terminals (3.1.2), capable of transforming a direct voltage Ve into an alternating voltage Vx. The elements of the DC side, also called DC bus, are connected to the DC terminals (3.1.2) and comprise capacitive means (3.2), which in the embodiment shown is a single capacitor, and connected in parallel to the capacitive means (3.2), a set of electronic regulator (4.1) and resistive means (4.2), connected in series with the electronic regulator (4.1).
    [0174] In a preferred embodiment, the inverter (3.1) is formed by a bridge of four of IGBTs. It is possible to use other types of semiconductor devices, but IGBT's allow a fast response, and have the additional advantage of generating a sinusoidal signal that does not introduce harmonic components, which avoids the circulation of harmonic currents and the need to include expensive equipment to correct. these problems. In order to carry out the inversion, the IGBTs need to receive trigger pulses generated by an auxiliary control circuit that is enabled in response to a control signal S2 from the control means (7).
    [0176] The electronic regulator (4.1) of the embodiment shown in Figure 3 is a chopper or chopper enabled by the S3 signal, and comprises several IGBT's that allow one or more resistors to be connected, thereby varying the ohmic value connected to the bus and regulating the current that circulates through the resistive media (4.2) and the dissipated energy.
    [0178] On the other hand, the passage of current through the resistive means (4.2) produces a power consumption, which is dissipated into the environment. In a preferred embodiment, the resistive means (4.2) comprise a plurality of resistors that can be selectively connected and disconnected, and with different nominal resistance values and different connection schemes, for example in series or in parallel, so that the value Resulting resistance can be modified as needed; To this end, the control means (7) emit a signal or set of control signals, S4, which allow modifying the total value of the electrical resistance. As a result, the power consumed depends on the total value of the connected electrical resistance.
    [0180] The direct voltage Ve is converted into an alternating compensation voltage Vx after passing through the inverter (3.1), whose alternating terminals (3.1.1) are connected in series between the voltage source (9) and the furnace electrode (8 ), so that the compensation voltage Vx is subtracted from the voltage of the voltage source (9), Vh. The result is that for a given impedance at the furnace electrode (8), Zh, and a constant supply voltage Vh, the circulating current at the furnace electrode (8) is reduced by the effect of the compensation voltage Vx:
    [0182] Ih = vt -vx
    [0183] Zh
    [0184] Thus, although the voltage of the source (9) remains constant and the impedance Zh of the electrode (8) is not modified by moving the electrodes (8), the current Ih does not increase above the maximum value allowed by the installation as a consequence of the initiation of the short circuit.
    [0186] This regulation requires adapting the voltage value to the variation of the circulating current. This is achieved by constantly monitoring the main variables of the installation, Vh, Vt, Vc and Ih, which correspond to the voltage applied to the furnace electrode (8), to the voltage of the voltage source (9), the voltage of the capacitive media (3.2) and the current flowing through the oven electrode (8); As shown in Figure 4, the monitoring is carried out by means of respective voltage measurement means (5.1, 5.2, 5.3) and intensity (6), which continuously emit measurement signals Syh, Syt, Svc, Si at the control means (7). In this way, before a sudden increase in the intensity Ih that anticipates a short circuit, the control means (7) initiate the necessary control actions to produce a compensation voltage Vx in accordance with the variation of the intensity Ih.
    [0188] The control means (7) process the signals of each phase independently, but physically they can be integrated in the same device common to the three phases; in any case, the control signals are output individually for each phase. Advantageously, the control means (7) of each phase are operatively connected to each other.
    [0190] In one embodiment, the control means (7) are integrated into a single physical device, with one channel for each phase. In one embodiment, the device that implements the control means (7) is a computer, a PLC, a system with microprocessors, etc.
    [0192] As shown in Figure 4, the control means (7) receive the measurement signals Svh, Svt, Svc, Si from the measurement means (5.1, 5.2, 5.3, 6) continuously; the control means (7) process the signals also continuously, and if the temporal variation of the measurement signals, in particular the intensity measurement signal Si, anticipates a short circuit, the control means (7) depending on of the other measurement signals determine what the compensation voltage Vx should be, and emit the corresponding control signals: a control signal S1 to enable the switching means (2) so that the converter branch (3) is enabled, a control signal S2 to enable the inverter semiconductor devices (3.1) and a control signal to the power sink (4) to enable dissipation
    [0195] power.
    [0197] In the embodiment in which the resistive means (4.2) are a plurality of resistors that can be selectively connected, the control means (7) additionally emit a signal or set of control signals S4 that allow the total value of the resistance to be varied of the resistive media (4.2).
    [0199] In one embodiment, the device comprises secondary control means (not shown); These secondary control means operate as a distributed control for the switching means (2), the converter (3) and the energy sink (4), to which they are operatively connected. In this embodiment, the secondary control means are enabled by means of the S1, S2 and / or S3 signals emitted by the control means (7), and once enabled, the secondary control means emit the trigger signals to activate or deactivate each of the semiconductor devices of the switching means (2), the converter (3) and the energy sink (4).
    [0201] Furthermore, in another embodiment, the device comprises secondary control means (not shown) to enable or disable the elements of the resistive means (4.2); These secondary control means, enabled by signal S4, operate in the same way as the secondary control means of the switching means (2), the converter (3) and the energy sink (4).
    [0203] Operation of the continuous intensity regulation device
    [0205] At the start of the process and during normal operation, the switch (2.1) is open and the static bypass switch (2.2) is closed, allowing the current to pass from the voltage source (9) to the furnace (8).
    [0207] At the moment in which a temporal variation of the intensity Ih is detected that exceeds an intensity threshold Ih max that allows anticipating a short-circuit intensity, and before the intensity reaches the value that would correspond to the short-circuit, the control means (7 ) emit a control signal S1 to the switching means (2) to enable the device (1), and as a consequence, the static bypass switch (2.2) opens.
    [0209] At the same time the converter (3) starts up and through the inverter (3.1) generates the compensation voltage Vx, calculated from the values of the voltage Vh, the voltage Vt, the voltage
    [0212] Vc and current Ih. When generating the compensation voltage Vx, the intensity of alternating current circulating through the inverter causes the absorption of energy from the alternating current side to the direct current side of the inverter (3.1) and the capacitive means (3.2) absorb energy and charge , raising the voltage V c between the terminals of the capacitive means (3.2). This energy must be dissipated to maintain the voltage Vc, and protect the device, and for this function the electronic regulator (4.1) and the resistive means (4.2) are used. As the voltage rises, the electronic regulator (4.1) connects more resistances of the resistive media (4.2), thereby reducing the total ohmic value of the resistance of the resistive media (4.2), and increasing the absorbed power and energy. dissipated.
    [0214] The voltage Vh, which results from subtracting Vx from the voltage of the voltage source Vt, is applied to the furnace (8), and will be such that the intensity resulting from the quotient between said voltage Vh and the impedance of the furnace remains below the threshold value Ih max.
    [0216] Once the short-circuit has ceased, or when the current Ih falls below the threshold value Ih max, the voltage Vx is canceled and the static bypass switch (2.2) closes, returning to the initial state.
    [0218] Figure 5 shows an example of the temporal evolution of four relevant magnitudes of the device for the same period of time: Vt, Ih, Vx Vh. Thanks to this graph, the relationship between voltages and currents described above can be verified.
    [0220] The first graph shows the signal of the supply voltage or the voltage source (9), Vt, which is a sinusoidal voltage constant in amplitude and phase.
    [0222] The second shows the signal of the current Ih that circulates through the furnace (8); In this graph it can be seen how a current peak occurs at a given moment, which could anticipate a short circuit.
    [0224] The third graph shows the signal of the compensation voltage Vx, which is generated in the device (1) in response to the current peak; It can be seen how its amplitude increases practically at the moment in which the current peak of Ih begins, and its amplitude varies until it disappears again.
    [0225] Finally, the fourth graph shows the voltage signal Vh applied to the furnace (8), which results from the combination of the Vt signal and the Vx signal. In the central area of the graph, that is, when the current peak occurs that could anticipate a short circuit, the result of subtracting the compensation voltage Vx, from the supply voltage or from the voltage source (9), Vt ,, so that the voltage Vh that reaches the furnace (at the electrodes) is lower, and consequently also the intensity Ih that circulates through said electrodes (8) of the furnace, which does not exceed the threshold Ih max.
    1
    权利要求:
    Claims (12)
    [1]
    1. Device (1) for continuous intensity regulation for an electric arc furnace, where for each phase
    The furnace comprises at least one furnace electrode (8) to which a voltage Vh is applied, and through which an intensity Ih circulates, and
    the furnace is connected to a voltage source (9) that generates a voltage Vt,
    characterized in that the device (1) is configured to be connected in series between the voltage source (9) and an electrode of the furnace (8), and comprises:
    - switching means (2), configured to be connected in series between the voltage source (9) and the at least one furnace electrode (8), and wherein the switching means (2) are configured to enable or disable the phase of the regulation device (1) to which it is connected;
    - a converter (3), connected in parallel to the switching means (2), so that the current flows through the converter (3) when the switching means (2) are open, and where the converter (3) understands,
    at least one inverter (3.1), with its alternating terminals (3.1.1) configured to be connected in series between the voltage source (9) and the at least one furnace electrode (8), where the at least one inverter (3.1) is configured to convert direct voltage into alternating voltage,
    capacitive means (3.2) connected to the DC terminals (3.1.2) of the at least one inverter (3.1), between which a voltage Vc is maintained, and
    an energy sink (4) connected in parallel to the capacitive means (3.2), where the energy sink (4) comprises an electronic regulator (4.1) and resistive means (4.2) connected in series with the electronic regulator (4.1 );
    - voltage measuring means (5.1) for measuring voltage Vh, voltage measuring means (5.2) for measuring voltage Vt, voltage measuring means (5.3) for measuring voltage Vc and measuring means of intensity (6) to measure the current Ih, where the measurement means (5.1, 5.2, 5.3, 6) are configured to emit measurement signals Svh, Svt, Svc, Si corresponding to the measured voltage and intensity values;
    - at least one control means (7) configured to receive and process the measurement signals Svh, Svt, Svc, Si from the measurement means (5.1, 5.2, 5.3, 6), and to emit control signals to the converter ( 3) and to the switching means (2) in response to a temporal variation of the intensity Ih that exceeds an intensity threshold Ih max as a consequence of the initiation of a short-circuit induced by the electric arc, where the control means (7) emit,
    a control signal S1 to the switching means (2) to enable the device (1),
    a control signal S2 to enable the inverter (3.1), and
    a control signal S3 to enable the power sink (4),
    so that the electronic regulator (4.1) of the energy sink (4) regulates the passage of current towards the resistive means (4.2) controlling the dissipated energy and maintaining the controlled direct voltage Vc between the direct terminals (3.1.2) of the inverter (3.1), which converts the voltage VC into a phase and amplitude regulated alternating compensation voltage Vx, which in turn is subtracted from the voltage Vt of the voltage source (9), so that the voltage Vh applied to the oven electrodes (8) are reduced and consequently the intensity Ih does not exceed the threshold Ih max.
    [2]
    2. Device (1) for continuous intensity regulation according to the preceding claim, characterized in that the at least one inverter (3.1) comprises at least one single-phase inverter bridge with semiconductor devices.
    [3]
    3. Device (1) for continuous intensity regulation according to the preceding claim, characterized in that the at least one inverter (3.1) comprises a bridge of four semiconductor devices, preferably bipolar insulated gate transistors with four diodes connected in anti-parallel ( IGBT's).
    [4]
    4. Device (1) for continuous intensity regulation according to any of the preceding claims, characterized in that the switching means (2) comprise a switch (2.1) and configured to disable the device (1), and a static bypass switch (2.2) and configured to enable or disable on-load voltage regulation instantaneously, where the switch (2.1) and the static bypass switch (2.2) are connected in parallel with each other.
    [5]
    5. Device (1) for continuous intensity regulation according to the preceding claim, characterized in that the switch (2.1) is one of the following list: an automatic switch, a load switch, a motorized vacuum disconnector.
    [6]
    6. Device (1) for continuous intensity regulation according to any of claims 4 or 5, characterized in that the static bypass switch (2.2) comprises thyristors, IGCT's, GTO's and / or IGBT's.
    [7]
    7. Device (1) for continuous intensity regulation according to any of the preceding claims, characterized in that the electronic regulator (4.1) comprises semiconductor devices of the IGBT type.
    [8]
    8. Device (1) for continuous intensity regulation according to any of the preceding claims, characterized in that the resistive means (4.2) comprise a plurality of resistors with different electrical resistance values, the control means (7) being configured to emit a control signal S4 to enable or disable a control of the electronic regulator (4.1) that selectively connects at least one resistor of the plurality of resistors.
    [9]
    9. Device (1) for continuous intensity regulation according to any of the preceding claims, characterized in that the control means (7) act on at least one phase of the device (1).
    [10]
    Device (1) for continuous intensity regulation according to any of the preceding claims, characterized in that it comprises respective secondary control means to enable or disable the elements of the switching means (2), of the converter (3) and / or of the energy sink (4), wherein the secondary control means are configured to operate in response to signals S1, S2 and / or S3 from the control means (7), signals S1, S2 and / or S3 emitted in turn by the control means (7) in response to the measurement signals Svh, Svt, Svc, Si.
    [11]
    11. Installation of a three-phase electric arc furnace, comprising a three-phase voltage source with at least three voltage sources (9), a three-phase electric arc furnace with at least three furnace electrodes (8), and at least one device (1) of continuous intensity regulation according to any of the preceding claims for each of the three phases.
    [12]
    12. Continuous intensity regulation method for an electric arc furnace with an intensity regulation device (1) according to any of the preceding claims 1 to 10, comprising the following steps:
    providing a regulation device (1) for each phase connected in series between the voltage sources (9) and the furnace electrodes (8);
    For each phase, when the furnace is in operation, the voltage measuring means (5.1, 5.2, 5.3) measure the voltages Vh, Vt, Vc and the intensity measuring means (6) measure the current Ih, and emit continuously measuring signals SVh, Svt, Svc, Si to the control means (7);
    for each phase, if the temporal variation of the current Ih increases above a threshold value Ih max, the control means (7):
    • emit a signal S1 to open the switching means (2) and enable the device (1);
    • depending on the measurement signals Svh, Svt, Svc, Si, they emit a control signal S3 to the energy sink (4);
    • for each phase, the control means (7) emit a control signal S2 to the inverter (3.1),
    so that for each phase the electronic regulator (4.1) of the energy dissipator (4) controls the passage of current towards the resistive means (4.2) by controlling the dissipated energy and maintaining a controlled direct voltage Vc between the direct terminals (3.1. 2) of the inverter (3.1), which converts the voltage Vc into an alternating compensation voltage regulated in phase and amplitude Vx, which in turn is subtracted from the voltage Vt of the voltage source (9), so that the voltage Vh applied to the oven electrodes (8) is reduced and therefore the intensity Ih does not exceed the threshold Ih max.
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    同族专利:
    公开号 | 公开日
    ES2836000B2|2021-12-01|
    WO2021130244A1|2021-07-01|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    WO2002063927A2|2001-02-08|2002-08-15|Hatch Ltd.|Power control system for ac electric arc furnace|
    CN104037767A|2014-06-20|2014-09-10|哈尔滨帕特尔科技股份有限公司|Suppression device for overvoltage and harmonic of energy storage type power grid|
    CN209119804U|2018-08-23|2019-07-16|潘政强|Electric furnace overvoltage energy absorption protective device|
    CN1845430A|2006-04-12|2006-10-11|华北电力大学|Load current quality regulator|
    ITUB20152674A1|2015-07-30|2017-01-30|Danieli Automation Spa|APPARATUS AND METHOD OF ELECTRIC SUPPLY OF AN ARC ELECTRIC OVEN|
    法律状态:
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    ES201931149A|ES2836000B2|2019-12-23|2019-12-23|CONTINUOUS INTENSITY ADJUSTMENT DEVICE FOR AN ELECTRIC ARC OVEN|ES201931149A| ES2836000B2|2019-12-23|2019-12-23|CONTINUOUS INTENSITY ADJUSTMENT DEVICE FOR AN ELECTRIC ARC OVEN|
    PCT/EP2020/087664| WO2021130244A1|2019-12-23|2020-12-22|Continuous current regulating device for an electric arc furnace|
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