Abstract: An electronic-controlled furnace transformer, which enables the reactive power, consumed by the furnace to be kept constant, thus reducing flicker. This is achieved by associating with a conventional power system of the electric arc furnace with current controllers and a booster transformer. By regulating the (reactive) power input with the help of the new control method, any disturbances in the power system can be reduced to a minimum.

Abstract: The present invention relates to a method for weighing an electrode submerged in the charge of an electric smelting furnace. The electrode is moved in vertical direction at least once, whereafter the electrode is lifted and the weight of the electrode is registered shortly after the electrode has been lifted.

Abstract: A power source for an arc furnace having an intermediate circuit transformer including a magnetic decoupled booster transformer and an AC main-driven converter. Such a power source comprises a current controller and a zero voltage switch. The current controller and the zero voltage switch are integrated in the intermediate circuit transformer. The zero voltage switch short-circuits the main reactance of the booster transformer whenever the current controller faces a current cut off and is blocked.

Abstract: In the operation of a dc arc furnace components of the furnace are monitored to detect unwanted arcs. A first low impedance path is continuously established between the components. When an arc is detected a second conductive path of a predetermined impedance is established between the components, in parallel to the first low impedance path, to extinguish the arc. After the arc has been extinguished the second path is open circuited to restore the furnace to normal operation.

Abstract: A method for regulation or control of the melting process in a three-phase arc furnace having at least three electrodes whose height is adjustable individually and independently of one another. Each phase of the three-phase current which feeds the three-phase arc furnace is assigned at least one electrode. The temperature of the three-phase arc furnace is monitored, particularly at points which are at risk of overheating, such as the walls of the three-phase arc furnace in the vicinity of the electrodes. When the three-phase arc furnace reaches a critical temperature in the vicinity of an electrode, the power emission from this electrode is reduced in such a manner that overheating of the three-phase arc furnace is prevented, and in that the power emission from the other electrodes or from some of the other electrodes is increased in such a manner that the total power emission from the electrodes is a maximum at a predetermined voltage.

Abstract: This invention relates to a method for measuring the electrode-related electric quantities of an AC electric-arc furnace. The method is based on observing the mutual correlation between electrode currents and total power supplied into a furnace by utilizing the fast, natural fluctuation of currents and power supplies into a furnace, and on estimation observations. The information required in estimation is collected by performing a plurality of successive current and voltage measurements at adjacent instants and at various energy distributions of a furnace. The measurement results are used to calculably determine the estimates for electrode-related voltages, impedances and powers. It is further possible to split the electrode-related powers and voltages on the one hand in the electric-arc power and voltage and on the other hand in the power and voltage loss caused by resistive conduction. The effect of mutual impedances is automatically taken into account in estimation.

Abstract: Procedure for regulating the heating of a furnace implementing a conventional means of regulation and a fuzzy logic supervisor which, on the basis of the given situation and the information which it receives on its inputs, adapts the parameters of the regulator, wherein the procedure includes the following steps:detection of the state of the process to be controlled and regulated;transient state or steady state is selected depending on the instructions/measurement discrepancy;selection of a control algorithm on the basis of the state (transient state or steady state) with the aid of a toggle based on the principle of fuzzy logic, while ensuring a smooth changeover between the states, with no discontinuity of control; andcalculation of the parameters of the regulator on the basis of the specific requirements, taking into account the following factors: volume production and rate of production, i.e., of the mass of the products treated in the furnace and of the speed of production; and temperature of the charge.

Abstract: In an electric arc furnace having a power source for applying at least one AC/DC voltage to at least one electrode, and the electrode being spaced apart from a grounded container for receiving scrap metal, wherein the application of the at least one AC/DC voltage to the at least one electrode causes generation of an arc between the electrode and the container for melting the scrap metal, a predictive line controller comprising a plurality of AC switches intermediate the power source and the electrode, and a central controller for monitoring the at least one AC/DC voltage and generating a signal model thereof, and in response generating and applying a plurality of gating signals to the plurality of AC switches, the gating signals being delayed by respective predetermined amounts based on the model, for causing the plurality of AC switches to gate the at least one AC/DC voltage in accordance with the model so as to minimize flicker in the electric arc furnace.

Abstract: Method to control the power supply for electric arc furnaces, whether they be fed with AC or DC, the furnaces including a melting cycle which includes the loading of the scrap carried out at time T.sub.0, an initial step of pre-melting the scrap with low and average power with a duration of (T.sub.1 -T.sub.0), a step of melting at maximum power with a duration of (T.sub.2 -T.sub.1) and a refining step with a duration of (T.sub.3 -T.sub.2), the method including the dynamic identification of the approximate moment when situations of risk inside the furnace cease, with a consequent permission to start delivery of maximum power, the dynamic identification being governed by the control and analysis of the electrical quantities, tension and current, fed to the furnace.

Abstract: A gas treatment unit is operated or placed in over-capacity mode during periods of low or zero electrical consumption by a metal treatment unit in order to produce a gas, at least a major part of which is not sent to the metal treatment unit during those periods but is at least temporarily stored in liquid or gas form.

Abstract: During a heating process in a three-phase, electric furnace, power can be controlled by dividing the heating process into intervals and then controlling the average power generated during each of these intervals, and by individually controlling the power generated by each phase. The latter is accomplished without requiring access to a neutral wire.

Abstract: In operation, DC arc furnaces generate undesired reactive load fluctuations which are compensated for by a power controller without special compensation reactance. In order to permit a melting operation of the arc furnace in weak AC systems the DC furnace is operated with at least two melting electrodes. A current controller is connected to each cathode via rectifiers. Each cathode is controlled with respect to its spacing from a melt by an electrode adjusting device and an electrode controller. Only one current controller one electrode controller are operationally connected, on an input side, to a power factor controller. Power factor control is thus performed with only one electrode assembly.

Abstract: A process and a device for regulating the position of the tip of an electrode immersed in an electric furnace heated by electric arc or resistance heating. To precisely measure the position of the electrode tip and to position it in operation, a series of gas containers are introduced into the electrode in succession at certain intervals, with each gas container being given a serial number (n.sub.i). The position of the electrode tip is determined by computer from the data of the last gas container with the serial number (n.sub.j) and the current number of the melted-open gas container, determined by gas analysis, using the gas that rises in the furnace through the melting process. Control technology is then applied to the drive of the electrode bearing device.

Abstract: A power converter device for supplying direct current to an electric arc furnace comprises at least one transformer with its primary fed with a three-phase alternating current and delivering to at least one secondary a three-phase current applied to a rectifier system outputting to the load a rectified voltage and current. The rectifier system comprises controlled semiconductors for each secondary and a freewheel circuit. The controlled semiconductors are triggered with essentially variable firing angles, modified to increase the duration of conduction in the freewheel circuit whilst reducing the duration of conduction in the triggered semiconductors, and vice versa, so as to deliver to the load a substantially constant active power or reactive power despite variations in the impedance of the load.

Abstract: An apparatus and method for controlling electrode gap in a vacuum arc remelting furnace, particularly at low melting currents. Spectrographic analysis is performed of the metal vapor plasma, from which estimates of electrode gap are derived.

Abstract: In operation, DC arc furnaces produce reactive load fluctuations which lead to undesirable flickering phenomena especially in a frequency range from 2 Hz-20 Hz. In order to reduce these flickering phenomena, comparatively fast reactive power regulation is superimposed on slow current regulation of the DC arc furnace which is controlled by rectifiers. In consequence, the use of a reactive-power compensator to compensate for reactive power fluctuations in superfluous.

Abstract: An arc furnace (1) has an electrode (13) and connection members (14) for connection to a power-supply network (20) for supplying an arc (16) at the electrode with current. The furnace is provided with a voltage-pulse generating member (3) adapted, in connection with an interruption in the arc, to supply voltage pulses to the furnace for striking the arc.

Abstract: DC arc furnaces have a current regulator for maintaining the current of an arc constant and an electrode regulator for affecting the position of an electrode of the arc furnace and thus the length of the are. Adjustment of the position of the electrode takes place by a hydraulic electrode adjustment device, which is controlled as a function of the difference between a predeterminable electrode regulator command variable signal and a voltage actual signal. The arc length is adjusted in such a way that a rectifier operates on the average with a deflection of, for example, 35.degree. el., independently of the secondary voltage of a furnace transformer and a set current set value. To be able to better protect the wall of the arc furnace and to better utilize the fed-in energy during operation with foaming slag, the arc length is automatically adapted to a slag height.

Abstract: A control system for controlling overshoot and undershoot power values when switching power from a single inverter power source to a plurality of inductive loads, or a single load having a plurality of zones, having different resonant frequencies. The control system causes a preselected amount of power to be drawn from the inverter power source and delivered to the loads, or zones in a time-shared manner. The control system varies the phase shift between load voltage and load current and selectably adjusts the amount of variation in response to overshoot and/or undershoot of power drawn from the inverter and delivered to a load or zone which can occur when switching between loads or zones.

Abstract: The direct current-electric arc furnace system includes a furnace vessel 8, one or more electric arc electrode 7 connected as a cathode, a bottom contact 12 connected as an anode, a furnace transformer 2 and a rectifier assembly 5 for feeding the furnace, an electrode control system E, and a current regulator I. A choke 6 is switched into the direct current main current circuit. A voltage control circuit F underlies the current control circuit I, whereby the output voltage of the current regulator 14 delivers the desired value for the voltage regulator 24. A filter 25 tuned to the flicker frequency follows the voltage regulator 24 with a frequency response, which is tuned to the frequency sensitivity of the human eye. Optionally, an additional control voltage signal U.sub.flick that is delivered by flicker meter can be provided to the voltage control circuit F.

Abstract: An improved arc furnace regulator employs neural circuits connected in a multi-layer network configuration with various weighted relationships between the successive layers which are automatically changed over time as a function of an error signal by means of the back-propagation method so that the regulator gradually improves its control algorithm as a result of accumulated experience. The network is implemented in software which can be developed and run on a PC with extra co-computing capability for greater execution speed. A second trainable neural network which emulates the arc furnace is used to develop the error signal, and is trained in mutually exclusive time periods with the training of the regular network.

Abstract: Direct current arc furnaces (8) have a current regulator (14) for maintaining the current of an arc (10) constant, and an electrode control (18) for affecting the position of an electrode (7) of the arc furnace (8) and thus the length of an arc (10). Control of the position of the electrode (7) is effected by means of a hydraulic electrode adjustment device (21), which is controlled as a function of the difference between a predeterminable electrode control input signal (.alpha..sub.soll) and an actual rectifier value signal (.alpha..sub.ist) at the output of the current regulator (14). In this way the length of the arc is controlled in such a way that a rectifier (5) operates with a mean control of, for example, 25.degree. el., independent of the secondary voltage of a furnace transformer (2) and of a set current reference value (i.sub.soll).

Abstract: Method and apparatus for controlling electrode immersion depth in an electroslag remelting furnace. The phase difference of the alternating current circuit established in the furnace is calculated in real time and employed to more accurately control immersion depth than possible with voltage-swing systems.

Abstract: In a direct-current arc furnace having a bottom contact (3) which has a large area, electromagnetically produced bath agitations are influenced by an electromagnet (9) disposed underneath the vessel bottom (4) such that the natural flow in the melt bath, caused by the current flow in the melt, is reversed in direction. In this way the stability of the bottom electrode (3) is substantially increased. The electromagnet (9) is preferably integrated into the electric supply system of the furnace and serves as a smoothing choke.

Abstract: A feedback control system for the impedance control of an electric arc furnace having at least one electrode, a hydraulic electrode actuator for adjusting the electrode. The actuator is adapted to be supplied with hydraulic fluid through a control valve. The furnace further includes a controller, which is connected to the valve actuator for the control valve, and impedance signal generator for delivering impedance signals to one input of the controller and a setpoint signal generator for delivering a setpoint signal representing a desired impedance to another input of the controller.

Abstract: Method to feed a three-phase direct-arc electric furnace with controlled current and also a three-phase electric furnace thus fed for the smelting of metals, e.g.

Abstract: Two DC electric arc furnaces are provided side by side. The both DC electric arc furnaces are connected by a duct. Each of two power source apparatuses is mounted near and associated with each of the DC electric arc furnaces. The anodes of the both power source apparatuses are mutually connected by an anode cable and the cathodes of the apparatuses by a cathode cable. The anodes and the cathodes of the both DC elecric furnaces are connected to the anode cable and the cathode cable, respectively, via a connection circuit adapted to supply electric power alternately to either of the DC electric arc furnaces. When a raw material is molten in one of the DC electric arc furnaces, electric power is supplied by the both power source apparatuses to this DC electric arc furance. The exhaust gas at a high temperature produced in this DC electric arc furnace is sent to the other DC electric arc furnace through the duct and preheats another raw material charged there beforehand.

Abstract: An improved arc furnace regulator employs neural circuits connected in a multi-layer network configuration with various weighted relationships between the successive layers which are automatically changed over time as a function of an error signal by means of the back-propagation method so that the regulator gradually improves its control algorithm as a result of accumulated experience. The network is implemented in software which can be developed and run on a PC with extra co-computing capability for greater execution speed. A second trainable neural network which emulates the arc furnace is used to develop the error signal, and is trained in mutually exclusive time periods with the training of the regular network.

Abstract: The invention provides a direct current electric arc furnace which is composed of a feeding system of direct current to the furnace, a movable electrode at the roof of the furnace, and a bottom electrode attached to the bottom of the furnace at the position deviated from the center of the bottom of the furnace, the deviated distance from the center being determined by a magnetic field, generated by a current in the steel bath of the furnace, from under an arc generated by the movable electrode to the bottom electrode, which can cancel a second magnetic field generated by the current of the feeding system.

Abstract: A flicker compensating apparatus for compensating for flickering due to a variation in the reactive power generated from a DC arc furnace connected by an AC/DC converter to an AC power system, comprises: a current detector for detecting a DC current flowing in the DC arc furnace; a controller for determining the phase control angle of a thyristor included in the AC/DC converter in accordance with the difference between the detected DC current and a predetermined reference current; a calculator for calculating reactive power to be generated by the DC arc furnace, from the detected DC current, the determined phase control angle, and a no-load DC voltage; a compensator including a reactive load connected via thyristor to the power system; and a controller for controlling the phase control angle of the thyristor of the compensator in accordance with the calculated reactive power, for controlling a current flowing across the reactive load, and for permitting the compensator to generate such reactive power as to co

Abstract: A direct current electric arc furnace comprises a main body, a moving electrode attached at the center of a roof of the furnace which generates an arc under the moving electrode, a bottom electrode attached at the center of the bottom, conductors which are connected to the bottom electrode, so that the deviation of the arc caused by a magnetic field originated at the outside of the main body is cancelled by another magnetic field caused by the conductors when electric currents are fed to the conductors and means of feeding direct currents to the conductors.

Abstract: The invention provides a direct current electric arc furnace which is composed of a feeding system of direct current to the furnace, a movable electrode at the roof of the furnace, and a bottom electrode attached to the bottom of the furnace at the position deviated from the center of the bottom of the furnace, the deviated distance from the center being determined by a magnetic field, generated by a current in the steel bath of the furnace, from under an arc generated by the movable electrode to the bottom electrode, which can cancel a second magnetic field generated by the current of the feeding system.

Abstract: System for controlling the positions of each of the three electrodes of a three phase electric furnace to maintain optimum real power delivered to the furnace in the event of electrode short circuiting or arc extinction due to scrap movement in the furnace. The system includes means for determining the magnitude of arc voltage and arc current and means to change the position of selected electrodes when either arc voltage or arc current is determined to be zero.

Abstract: A method for on-line monitoring and/or control of an electric arc furnace utilizing a method of data transfer between a programmable logic controller and a microprocessor comprising monitoring data from the furnace over a fixed time cycle, assigning data values to the monitored data during such time cycle, dividing the fixed time cycle into a multiple of N time subintervals, dividing the data values into data subsets, assigning designated time subintervals to each of the data subsets, transmitting data to the microprocessor in each time subinterval to execute program code corresponding to the data subset in such time subinterval and calculating control factors from the transmitted data for providing control information.

Abstract: According to this process and this device:a signal representing the derivative of the intensity of the current in the arc is sensed,the sensed signal is amplified,the amplified signal is directed simultaneously into two band pass filters (6, 7) respectively having a high frequency broad band (6) and having a narrow band centered on a low fundamental frequency (7),the signals emanating from the filters (6, 7) are transmitted to effective value extractors (8, 9),by means of a divider module (11) an energy signal is formulated, which is proportional to the ratio of the effective value of the signal emanating from the broad band filter (6) and the effective value of the signal emanating from the narrow band filter (7),and the proportional energy signal obtained is displayed on a scale (12), where it is expressed as a percentage, this percentage being indicative of the behaviour of the arc, signifying the formulation phase.

Abstract: A method for electric refining of lead with alternating current in which the basic stage of the process is preceded by two stages, a preparatory stage and an initial stage. The preparatory stage involves pretreatment of the electrode surfaces by means of alternating current of equal width and amplitude of the forward and reverse pulses. During the initial stage there is effected an electric refining with alternating current having reduced current density.A circuit for electric refining of lead with alternating current has two controllable current rectifiers, each of which is connected to a separate group of electrolytic baths. The groups of electrolytic baths and the controllable current rectifiers are connected in series and opposite to one another.

Abstract: A clear optical path is provided in a furnace in which high intensity top surface heating is carried out. The path extends through a viewport to the interior of the furnace chamber. The path extends to a clear metal mirror surface and from the mirror surfaced to other portions of the furnace chamber which are not viewable directly through the viewport.

Abstract: Apparatus for the detection and evaluation of process parameters arising during the remelting of an electrode (31) to a metallic block (32) in a vacuum arc furnace detects deviations of at least one process parameter from a predetermined course and uses them to locate faults in the electrode and/or in the metal block (32).

Abstract: The reactive power compensation system used for preventing the power voltage fluctuation includes an inverter which operates in response to a high-frequency PWM signal based on the reactive power determined from the voltage and current at the receiving point to compensate a sharp varying component of reactive power created by the load, and a capacitor which is connected or disconnected with the power system through a semiconductor switch on the basis of comparison of the load reactive power with preset values so as to supply the leading reactive power back to the power system.

Abstract: A method of monitoring the degree of exposure of an electric arc within a furnace having a molten charge, e.g. an arc furnace or ladle furnace, in which characteristic frequency spectra of the waveforms from the supply associated with (a) arc-exposure and (b) arc-submersion are predetermined and in which signals (e.g. indicative of the arc current) emitted during operation are measured and processed and a comparison effected with a set level established from these characteristic signals whereby to provide an indication of the degree of arc exposure.The predetermined characteristic frequency spectra selected may be the harmonic content of the arc current.

Abstract: A method for the optimum regulation of the electrodes of a three-phase electric arc furnace wherein each electrode has an associated arc voltage regulator which receives the associated arc voltage as its actual value and a desired arc voltage value as its reference value; and wherein, to form the desired arc voltage value, during each halfwave, a voltage porportional to the actual arc current and a limit value, which corresponds to the desired arc length, are provided, and the smaller momentary value, with respect to magnitude, of the current proportional voltage and of the limit value is always fed to the arc voltage regulator as the desired arc voltage value.

Abstract: The height position of three-phase electrodes R, S, T immersed in a resistive medium is controlled first in dependence of the values for the equivalent star network load impedances Z.sub.RO, Z.sub.SO, Z.sub.TO of the electrodes, these impedances being calculated on the basis of measured values representative of valid delta network load impedances Z.sub.RS, Z.sub.ST and Z.sub.TR of the electrodes. The height positions of the electrodes are then equalized by selective adjustment of the electrical conductivity of the resistive medium at respective electrodes, preferably by using the so-called derivative method.

Abstract: In a reactive power compensation apparatus for compensating reactive power generated by a load connected to an AC power supply system, dual phase current signals obtained by dual phase-converting the load currents and unit dual phase voltage signals synchronized with voltages of an AC main line connected to the load are used, and arithmetic operations thereof are performed to separately detect an in-phase reactive component signal and opposite phase component signals of the load currents. Current commands are generated on the basis of the separately detected signals, thereby controlling the reactive power compensation apparatus on the basis of the current commands.

Abstract: A method of operating an electric arc furnace is disclosed by which an arc electrode provided in an electric arc furnace is supplied with electric power, an electric arc is extended from the arc electrode and raw material in the electric arc furnace is molten by the arc. Before operation of the electric arc furnace, an electric current I satisfying an equationd[Pi/(Pi-Pl-ql)]dI=0is first calculated where Pi is the secondary output of the used arc furnace transformer. Pl is the total ohmic loss of the secondary winding of the transformer and of an electric circuit connecting the secondary of the transformer with the arc electrode, ql is the heat loss of the used electric arc furnace and I is the electric current flowing from the secondary of the transformer to the arc electrode. Next, when electric power is really supplied to the arc electrode from the arc furnace transformer to operate the electric arc furnace, the beforehand obtained electric current is supplied to the arc electrode from the transformer.

Abstract: A method and apparatus for electrically balancing the phases of a three phase arc furnace, the furnace having a vessel containing a molten bath, three electrodes above the bath, and a transformer arrangement composed of three phases, each phase including a winding, the transformer arrangement being connected to the electrode so that each electrode conducts an arc current proportional to the voltage across the winding of a respective phase, by the steps of: matching the voltages between the electrodes and the bath to one another by adjusting the spacing between at least one electrode and the bath; and establishing symmetry among the arc currents by: varying the voltage across at least one phase winding by a selected increment; measuring the arc current amplitude in the electrode associated with the at least one phase winding after each variation step; and repeating the steps of varying and measuring until the differences between the arc current amplitudes of the three electrodes are less than a given value.

Abstract: This invention concerns a procedure for controlling the type of arc in an electrical furnace (F), which comprises the monitoring (R) of the short circuit power of the network line (L) during a period of inactivity of the arc, whereby the value thus monitored is processed (B) to determine a primary voltage (V) to be maintained at a transformer (T2) supplying the electrodes of the furnace (F), and whereby the processing (E) combines fixed parameters (P) and at least variable parameters relating to:pre-set conditions of the arc (S),conditions of a substation tap changer (VAR),and line parameters (C) including at least the state of connection of banks of capacitors (C1-C2).The invention also concerns an arc furnace (F) which employs a procedure for controlling the type of arc according to the methods described herein.

Abstract: A method for controlling an arc furnace is disclosed. In first step, many V-curved correlations between a value of arc current and a specific electric power consumption are obtained with respect to each of a plurality of measuring melting materials of various different scrap blendings. Next, in factory operation of the arc furnace, a melting material is melt at an arc current value in the bottom of the curve or in the vicinity of the bottom where the specific electric power consumption is minimal in the pre-obtained V-curve correlation with respect to the measuring melting material of scrap blending corresponding to scrap blending of the melting material to be melted.

Abstract: A control system for a DC arc furnace having a hearth adapted to contain a scrap or metal charge, an arcing electrode, a thyristor converter having a connection with the electrode and charge to form a circuit, current comparing comparator for comparing current in the circuit with a set-point current of fixed value and controlling the thyristor in response to the comparison so as to cause the current in the circuit to substantially equal the set-point current value, electrode positioning apparatus for moving the electrode up and down relative to a charge in the hearth, and a voltage comparison comparator for comparing the voltage in the circuit with a set-point voltage of fixed value and controlling the electrode positioning apparatus in response to the voltage comparison so as to keep the voltage in the circuit substantially equal to the set-point voltage.

Abstract: A method for controlling and balancing the power consumption in an electric smelting or heating furnace, in which power is fed into the furnace via at least two electrodes and in which the tips of the electrodes are maintained at the same level above the melt or at the same distance from the furnace cover throughout the process sequence. Power is controlled by adjusting the voltage between the furnace electrodes, the electrotechnical quantities of the furnace varying freely throughout the process sequence. Any disequilibrium due to the electrode structure or to changes in the furnace conditions is balanced out by adjusting the moving of furnace electrodes, corresponding to the wear of the electrodes, by using the quantities measured in the furnace and the short-term and long-term variations calculated with the aid of these quantities, and the linear functions with relation to time of the variations.

Abstract: A method and apparatus for vacuum arc furnaces monitors the arc by spectrum analysis of the arc's light obtained with a radiation receiver. Upon the occurrence of spectrum lines indicating vaporization of the crucible material, the melting process is stopped or adjusted to extinguish the arc burning on the crucible which vaporized the crucible material for the spectrum analysis.