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 of controlling the course over time of a target temperature of a molten metal in a ladle, for example, in which the required heating power is produced by at least one plasma torch. Determination is made of the variation with time of a target temperature, the mass of an outwardly flowing melt, and a specific heat value of the melt present in the ladle. From the foregoing values there is ascertained the course of a corresponding setting signal for obtaining the heating power necessary to obtain the desired temperature course. Simultaneously and continuously the actual temperature of the melt is measured. When the actual temperature of the melt deviates from its target temperature in excess of a predetermined tolerance, the setting signal for the heating power is changed by decreasing such setting when an actual temperature exceeds the target temperature, and increasing such setting when an actual temperature is less than the target temperature.

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 consumable electrode is positioned in a furnace under utilization of radially outwardly projecting ribs, at least one wheel with projection engages one of the longitudinal ribs and provides a deformation thereof in terms of indentation and thereby is and remains briefly in engagement with the rib such that the wheel with and through its projection holds and advances that electrode. The wheel has prongs, serrations or teeth and preferably cooperates with a counterwheel on the other side of the rib.

Abstract: Apparatus for controlling the distance of a melting electrode from the surface of melted material in a vacuum arc furnace which uses short circuits caused by the droplets between the melting electrode and the surface of the melted material as a control criterion. The short circuits occurring within a given period of time--the so-called droplet rate--are determined and supplied to an averager which is connected with a controller that controls an electric driving mechanism for the melting electrode. According to the invention, the controller is responsive to a signal representing the difference between the reciprocal value of the droplet rate signal formed by the averager and a desired time, this desired time being equal to the desired average time between two consecutive droplet short circuits.

Abstract: A compensation device for the influence of the weight of a power feed line on a weight measurement device determining the weight of an electrode and/or the melting rate in an electro-slag remelting process, in a vacuum arc furnace or the like. When an x-y device is adjusted, a weight jump occurs due to the forces of the power cable or the forces of the bellows, which has a disturbing effect on the rate definition. This weight jump can be prevented by means of mechanical devices, or can be made so small that it no longer constitutes a disturbance. However, the expenditure for this is disproportionately high. The invention is more cost efficient, since hardware or software means suffice. The weight function G=f(t) is extrapolated and compared with the actually measured weight G'=f(t). The magnitude of the difference between the two is stored and later added as a correction value.

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: A method and apparatus for regulating an arc discharge furnace having a lining, a plurality of electrodes disposed above a bath of conductive material, an adjustable transformer for applying to each electrode a voltage which causes an arc current proportional to the applied transformer voltage to flow between the electrode and the bath, a device for varying the voltage applied by the transformer to each electrode, and a device for varying the vertical spacing between each electrode and the bath. Desired values for a maximum of two of the following parameters are selected: the voltage of the arc current produced by one electrode; the arc current produced by the one electrode; the power of the arc produced by the one electrode; a parameter which is proportional to the wear caused to the furnace lining by the arc produced by the one electrode; and a correcting variable for the voltage applied to the one electrode by the transformer.

Abstract: Operation control system for an electrothermal furnace having one or more electrode and a transformer unit for each electrode for supplying heating current to its associated electrode. The or each transformer unit includes a main transformer having a primary winding for receiving current from a mains and two secondary windings, and an additional transformer connected to derive an adjustable voltage from one of the second secondary windings. The adjustable voltage and the voltage across the other secondary winding of the main transformer are combined to supply the heating current to the electrode. The control system includes a switch and a current control unit connected in the transformer unit for giving the additional voltage a selected polarity relative to the voltage across the other secondary winding of the main transformer and for controlling the magnitude of the additional voltage.

Abstract: A crucible furnace including a furnace vessel in which a graphite electrode and a metal contact electrode are vertically and horizontally movable.

Abstract: An arc furnace electrode control includes phase angle measuring devices connected respectively for producing a phase angle signal functionally related to the phase angle between the primary electrode voltage and current. A bias circuit is coupled to the primary of each phase for producing a bias signal functionally related to the reactive volt amperes delivered to the electrodes. Null detectors are coupled to each phase angle measuring device for receiving one of the phase angle signals and to the bias circuit for receiving the bias signal for producing a control signal for each phase related to the difference between the respective phase angle signal and the bias signal. A control is coupled to each null detector and is responsive to each control signal for individually positioning the respective electrodes in relation to the furnace so as to achieve preselected phase angles.

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: The electrode of an electric arc melting furnace is adjusted in height by a hydraulic cylinder having an operating chamber which is connected via a servo valve to a hydraulic pressure source or, respectively, to a reservoir. The servo valve is actuated by a control signal which is produced by a comparison of the actual value of the electric arc current and a predetermined desired current value. Additionally, the pressure in the operating chamber of the cylinder is measured and supplied to the control circuit as a feedback value. An important advantage deriving from the present invention is the ability to provide a control of the electrode motion by virtue of the measured pressure even before the electric arc is ignited and to steadily hydraulically support the electrode under any condition of operation. Accordingly, uncontrolled motions of the electrode are prevented which motions might result in an increased danger of breakage, in overcurrents or short-circuits.

Abstract: During vacuum consumable arc remelting the electrode gap between a consumable electrode and a pool of molten metal is difficult to control. The present invention monitors drop shorts by detecting a decrease in the voltage between the consumable electrode and molten pool. The drop shorts and their associated voltage reductions occur as repetitive pulses which are closely correlated to the electrode gap. Thus, the method and apparatus of the present invention controls electrode gap based upon drop shorts detected from the monitored anode-cathode voltage. The number of drop shorts are accumulated, and each time the number of drop shorts reach a predetermined number, the average period between drop shorts is calculated from this predetermined number and the time in which this number is accumulated. This average drop short period is used in a drop short period electrode gap model which determines the actual electrode gap from the drop short.

Abstract: An electric arc furnace comprising at least one pair of electrodes extending through the roof of the furnace for the creation of electric arcs between each of the electrodes and the charge to be melted, and a source for applying direct current to each of said pairs of electrodes, respectively of different polarities. Preferably the furnace contains also an electric probe extending through the bottom of the furnace to determine the potential of the molten charge and means for adjusting the vertical position of each electrode for maintaining the potential difference between each electrode and the molten charge at a predetermined value.

Abstract: A method of controlling the depth of immersion of an oxygen lance in a molten bath within an electric arc furnace where noise emitted from the furnace during lancing in an acoustic spectrum ranging between 1 kHz and 15 kHz defined by a plurality of selected frequency bands is monitored. The position of the lance with respect to the bath surface is controlled by reference to the amplitudes of the output signals emitted from each of the selected frequency bands. There is a distinct change in the relationship of particular bands to provide a "lance out" signal which is directed to a control for a lance drive mechanism. Apparatus for practicing the method includes a microphone, a filter unit, a microprocessor and a lance drive responsive to signals from the microprocessor.

Abstract: In accordance with the method, the arc supplying current is modulated if necessary for generating an acoustical signal. The acoustical signal generated by the arc is detected and its amplitude which, in practice, is a direct function of the actual length of the arc, is compared to a reference amplitude corresponding to the desired length of the electrical arc, in order to determine the algebraic value of their difference. This algebraic value is used for monitoring at least one element of the machine between which the arc forms, and moving this element proportionally to the so-determined algebraic value in order to increase or reduce the actual length of the arc and to bring this length back to the desired length.

Abstract: A snubber device for preventing the uncontrolled fall of a column supporting an electrode and crosshead structure in an electric arc furnace upon failure of the hoisting mechanism or cable. Clamp plates containing serrated surfaces are positioned on either side of the electrode column and are joined by a number of parallel link arms to form a pantograph-like structure. A linkage is attached to the cable deadend which causes the plates to move in vertical relationship to each other, thereby causing a horizontal displacement of the plates and clamping the column between them to prevent downward movement. The column snubber is provided with a number of flanged rollers which ride on the outer surface of the column to permit rolling movement between the snubber and column. When the clamp plates are clamping the column, the rollers move out of contact with the outer surface. The column snubber automatically adjusts for wear in the electrode column assembly.

Abstract: A method of lowering graphite electrodes which are supported vertically displaceable electrode holders and extend through the cover of an electric arc furnace is disclosed. In accordance with the disclosed method, the furnace cover is completely laterally swung away from the furnace vessel and then the free lengths of the electrodes below the electrode clamps are adjusted to a position insuring a stable electric arc.

Abstract: An electrode support mechanism for use in electric arc melting or smelting furnaces wherein a pair of horizontal, superimposed arms are each provided with clamping devices at their outer end for supporting a vertically disposed electrode depending into an arc furnace. The arms are each supported on a vertical support post; the upper arm is fixed to the post and the lower arm which normally carries the electrode is movable relative to the post to adjust the electrode to maintain a constant arc at the furnace. The movable arm is moved vertically by a jack screw carried by the upper arm and depending into contact with the lower arm. The clamping devices at the ends of the arms are spring-biased toward contact with the electrode, and a linking mechanism is provided to alternately release the arm clamping mechanisms from the electrode under the control of a cam-operated actuating system.

Abstract: An electro-slag remelting furnace having consumable electrodes and a mold for receiving a melt formed from the electrode material; at least one drive motor and at least one spindle and an associated stationary spindle nut for vertical movement of the electrode; at least one guide column, which is provided for vertically guiding the consumable electrodes and which extends parallel with the spindle and relative to which the spindle is rotatable mounted at its two ends; and at least one clamping device for the consumable electrodes.

Abstract: An electrode positioning control for electric arc furnaces includes a first circuit for producing an electric error signal functionally related in magnitude and sense to the electrical parameters in the electrode. The error signal is used to control the firing angle of an electronic switching device coupled between an electrode positioning motor and its power source. In addition, a signal generator is coupled to the motor for providing a velocity feedback signal functionally related to motor speed and direction for further modulating the firing angle.

Abstract: An electronic safety device for the electrodes of an electric steel-making furnace in which the position of the electrodes is controlled by a position-regulating device. The safety device is adapted to detect when an electrode has been brought to a stop and automatically raise the electrode if it has not been stopped in response to an order to stop from the position-regulating device.

Abstract: An impedance controller is used for controlling electrode-to-bath spacing in an arc furnace. Measured quantities proportional to the electrode voltage and the electrode current are determined and an actual impedance value is formed from the measured values by means of a divider. The actual impedance value is compared with a predeterminable desired impedance value to derive a control signal. If in the event of a short circuit, the actual impedance value reaches a predetermined lower limit, a switching element sets into the controller a signal causing full drive, so that the electrodes are raised at maximum velocity. If the sum of the two measurement quantities becomes zero, the output of the controller is cut off.