Abstract: A direct current smelting electric furnace includes a rectifying control circuit, a rectifying power supply device, a short network device, a multi-load layout device including multiple electrodes, and an electric furnace body. The rectifying power supply device includes at least two double-circuit direct current power supply packs. Four output terminals of each double-circuit direct current power supply pack are connected to three electrodes in the multi-load layout device by the short network device to constitute two current circuits by an electric furnace weld pool load. Each electrode in the multi-load layout device is connected to homo-polar output terminals of a three-phase negative semi-cycle rectifying output circuit and a three-phase positive semi-cycle rectifying output circuit, separately. The rectifying power supply device-includes multiple output current circuits.

Abstract: In a method for operating an arc furnace (2) with at least one electrode (3a, 3b, 3c), a solid material fed to the arc furnace (1) is melted by an arc (1) formed by the at least one electrode (3a, 3b, 3c). A measurement (MM) for the mass of one part of the solid material arranged on a boundary (2) of the arc furnace (1) is determined, and using the determined measurement (MM), a process variable of the arc furnace (1) is controlled and/or regulated. A method which can reduce the risk of electrode damage caused by metal scraps falling into the treated area is provided.

Abstract: A power supply arrangement for supplying a square-wave current (I2) to a load connected to an output of the power supply arrangement, in particular a power supply arrangement in an arc furnace for generating an arc, including a transformer (TU) with at least two primary-site taps (1U1, 1U2) which form an input of the power supply arrangement, and with several secondary-side taps (2U1, 2U2, 2U3, 2UN), a bridge circuit (BU) with several first half bridges (11, 12, 13) which include converter valves (V11, V12, V13, V14, V15, V16) and which each have a first terminal (A11, A12, A13) of the bridge circuit, with a bridge section with a choke (L1), and with a second half bridge (20) which has converter valves (V17, V18) and a second terminal (A20) of the bridge circuit (BU), wherein each first terminal (A11, A12, A13) is connected to one of the secondary-side taps (2U1, 2U2, 2U3) of the transformer (TU), wherein the second terminal (A20) is connected to the output.

Abstract: A roof system for an electric arc furnace includes a skew removably attached to the electric arc furnace, a lining of refractory material affixed to the skew, and a delta composed of a refractory material. The delta has at least one aperture capable of receiving an electrode. The delta fits onto and is supported by the refractory lining that is affixed to the skew.

Abstract: A method for treating spheroidal graphite iron includes the step: pouring molten spheroidal graphite iron into a pouring electrical furnace (1); covering the molten spheroidal graphite iron (5) with alkali slag (6) which is melted at high temperature and rich in alkali earth metal ion, rare earth metal ion, or mixture of them; connecting the molten spheroidal graphite iron (5) with the negative pole of the direct current source by one pole (7); connecting the alkali slag (6) with the positive pole of the direct current source by another pole (4), treating the molten spheroidal graphite iron (5) with the alkali slag (6) which is used as electrolyte. The method can prevent the spheroidized fading velocity of the spheroidal graphite iron. The pouring electrical furnace can be used for treating the molten spheroidal graphite iron.

Abstract: Method for heating a fluid, in particular a fluid which is not electrical conductive, where a rotor body (10) which is arranged in a chamber for absorption of the fluid, is rotated with a generally vertical shaft (11). A voltage is applied to a rod shaped electrode (16) which is arranged centrally in a rotor chamber (12) and to an electrode at the bottom (13) of the rotor chamber, for creation of a flame arc, so that a flow of the fluid passing the flame arc is created. The length (L) of the flame arc is held generally stable, preferably constant by controlling the position of the rod shaped electrode (16). The fluid is made enter the rotor chamber (12) so that it is kept outside the flame arc, and that the fluid is provided to flow through the rotor chamber (12).

Abstract: The present invention is based on a novel electric induction furnace design that enables the removal of zinc-containing filter dust (FD) originating from the production of steel (alloy or non-alloy) and the production of cast iron with galvanized steel scrap, using a novel process based on the carbothermal reduction of the metal oxides present in the FD, performed at the temperature at which the materials are melted inside the electric induction furnace. The electric induction furnace of the invention incorporates an electric arc or plasma beam generator to melt all the inorganic non-metallic material. The incorporation of this generator also enables the use of large volumes of molten slag.

Abstract: A furnace for melting metals includes a crucible, a direct current arc source and an induction coil powered by alternating current. The furnace is particularly useful for melting charges of highly reactive metals such as titanium, zirconium and their alloys without contaminating these charges. The direct current arc source melts generally from the inside out while the water-cooled induction coil serves to cool the crucible and form a skull along the crucible sidewall which protects the crucible from interacting with the molten metal. The induction coil is thus used for cooling as well as heating and stirring the melt, and helps control the thickness of the skull.

Abstract: The described methods and systems may be applied to electric arc furnace installations. In this context, the method and system provide an electrode position controller coupled to the feed rate controller so as to predictively anticipate the introduction of new source material and lower the electrodes so as to prevent arc extinguishment while variable reactors are controlled to maintain predetermined power set-points. The electrode position controller may be used in place of, or in addition to, the variable reactance control system to take corrective action to address power and/or current changes or unbalances.

Abstract: A method and system for stabilizing energy consumption in multiple loads, or in single multi-phase loads. The method and system also compensates for unbalance in multi-phase loads. A central controller monitors variable reactances in the loads and identifies situations of power and/or current fluctuation and/or unbalance. It determines appropriate corrective action by the other loads/phases to compensate for the power and/or current change or unbalance due to the problematic load, and it issues control signals instructing variable reactor controllers associated with the other loads to adjust accordingly. The method and system may by applied to electric arc furnace installations. In this context, the method and system provide an electrode position controller coupled to the feed rate controller so as to predictively anticipate the introduction of new source material and lower the electrodes so as to prevent arc extinguishment while the variable reactors maintain predetermined power set-points.

Abstract: A batch process for an electric arc furnace (1) to manufacture steel (10) includes the steps of providing an empty furnace having a bottom (14) and sides (16) and electrodes (2, 3); adding molten metal to the empty furnace; adding other necessary ingredients through charge openings (26); applying current to provide an arc (4) and supplying oxygen through an oxygen lance (6) to react and melt the contents of the furnace and form a top slag (9) and bottom molten metal/steel (10); and stopping the reaction and pouring out all the slag through a slag tap (5) and molten metal tap (32) to provide an empty furnace for the next batch run.

Abstract: An electrode assembly comprising concentric tubular electrodes is provided for high temperature processing of materials. The electrode assembly is connected with a power supply that includes switching means for alternatively operating the electrode assembly in a transferred mode of operation, in a non-transferred mode of operation, or according to a controlled sequence of non-transferred and transferred modes of operation. The power supply system includes variable inductors, such as leakage-coupled reactors, for controlling the electrical power supplied to the electrodes for producing a DC arc. The electrode assembly can be incorporated into an arc furnace for processing waste material in the furnace. The electrode assembly is also suitable for use in the practice of in-situ vitrification and remediation of contaminated soil.

Abstract: A direct-current arc furnace for producing steel has a smelting vessel with electrodes, tapping openings for the molten mass and slag, and a device for a direct removal of exhaust gases. The smelting vessel is extended upwardly by a central shaft for introducing melt-down material into the vessel. The extension of the central shaft forms a melt-down material column. A shaft suction device is provided as an extension of the shaft for removal of the exhaust gases during the smelting process. Adjacent to the shaft openings are provided in the upper part of the smelting vessel for receiving a vessel suction device for dust and/or gases resulting during the charging process of the melt-down material. The shaft suction device and the vessel suction device are connected to a common device and switching elements are provided for actuating only one suction device and/or adjusting a combination of the exhaust gas flows dependent on the charging and smelting process.

Abstract: An electrode assembly comprising concentric tubular electrodes is provided for high temperature processing of materials. The electrode assembly is connected with a power supply that includes switching means for alternatively operating the electrode assembly in a transferred mode of operation, in a non-transferred mode of operation, or according to a controlled sequence of non-transferred and transferred modes of operation. The power supply system includes variable inductors, such as leakage-coupled reactors, for controlling the electrical power supplied to the electrodes for producing a DC arc. The electrode assembly can be incorporated into an arc furnace for processing waste material in the furnace. The electrode assembly is also suitable for use in the practice of in-situ vitrification and remediation of contaminated soil.

Abstract: The invention pertains to a process and to a device for supplying current to an electric-arc melting unit for melting and heating metal, especially steel, with a three-phase a.c. source, which sends the current via devices for producing direct current or alternating current to at least one electrode projecting into the vessel of the melting unit. The three-phase a.c. source (91) is followed by at least two power supply modules (41, 4n), connected in parallel, where each power supply module (41; 4n) has an uncontrolled three-phase bridge (51, 5n), a direct-current intermediate circuit (61, 6n), and a transistor unit (71, 7n) connected in series, and where, downline from the power supply modules (41, 4n) in the current flow direction, a common current-carrying line (31) leads to at least one electrode (21) of the melting unit (11) and away from at least one other electrode (22, 24).

Abstract: An electrode assembly comprising concentric tubular electrodes is provided for high temperature processing of materials. The electrode assembly is connected with a power supply that includes switching means for alternatively operating the electrode assembly in a transferred mode of operation, in a non-transferred mode of operation, or according to a controlled sequence of non-transferred and transferred modes of operation. The power supply system includes variable inductors, such as leakage-coupled reactors, for controlling the electrical power supplied to the electrodes for producing a DC arc. The electrode assembly can be incorporated into an arc furnace for processing waste material in the furnace. The electrode assembly is also suitable for use in the practice of in-situ vitrification and remediation of contaminated soil.

Abstract: The present invention pertains to a direct current electric arc furnace for melting or heating raw materials or molten material. The furnace comprises a refractory lined vessel for holding raw or molten metal material. The furnace also comprises a first top electrode and at least a second top electrode. Each of the top electrodes enters the vessel above the raw or molten material and has a position in the vessel. The furnace comprises at least one bottom electrode mounted in the bottom of the vessel and in electrical contact with the raw or molten material in the vessel. Additionally, the furnace comprises an electrical power supply mechanism with conductors to electrically connect to the top electrodes and the bottom electrode in order to input electrical energy into the material through the top and bottom electrodes in the form of arcs which deflect toward each other and define a hot area.

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: Method for recognition of noble metals otherwise not recognizable in base material clusters includes using an electric arc furnace in which base material clusters are disintegrated to free atoms or are alloyed with other components of the base materials, and are able to be recovered by conventional recovery techniques once they are recognized. The base material includes the products of smelting processes, pellets of compacted raw material, like anode mud or waste material, and the base materials are melted utilizing the heat from a dc electric arc furnace.

Abstract: Method for the electromagnetic stirring of the liquid metal (14) in direct current electric arc furnaces which include a hearth (35) defined by a floor (13) and by side walls (15), a central cathode (11) cooperating with anodes (12) arranged on the floor (13) of the furnace and fed by a main current (I.sub.0), wherein there is an electromagnetic system generating a magnetic field inside the liquid metal (14) whose vertical (B.sub.z) and radial (B.sub.r) components interact respectively with the radial (J.sub.r) and vertical (J.sub.z) components of the overall current present in the liquid metal (14). The method and device use a first electromagnetic system including at least a first winding (19) through which a current (I.sub.1) flows and operating from inside the floor (13) and the walls (15) of the hearth (35), and a second electromagnetic system generating a secondary induced current (I.sub.3), between adjacent anodes (12), which circulates through the liquid metal (14).

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: A direct current electric arc furnace for melting or heating raw material or molten material. The furnace includes a refractory lined vessel for holding raw or molten material in its interior. The furnace includes at least a first top electrode. The first top electrode enters the vessel interior above the raw or molten material. The furnace includes at least a first bottom electrode mounted in the bottom of the vessel and in electrical contact with the raw or molten material in the vessel. The furnace also includes an electrical power supply mechanism which electrically connects to the top electrode and the bottom electrode in order to input electrical energy into the material through the top and bottom electrodes in the form of an arc. The bottom electrode has an opposite electrical polarity to the electrical polarity of the top electrode. The furnace includes a mechanism for stirring the molten material in the vessel and guiding the arc in the vessel.

Abstract: A plant for producing metal includes a electricity supply system and a direct-current electric arc furnace connected thereto, where in order to make do with an electricity supply system possessing a relatively small short-circuit capacity, the direct-current electric arc furnace has at least two electrodes and the electricity supply system has a system short-circuit capacity S.sub.k which is at least equal to ##EQU1## wherein S.sub.i is the nominal power per electrode and i represents an index for the electrodes that varies from 1 up to the maximum number of electrodes in the direct-current electric arc furnace.

Abstract: Cooling system for electrodes (11) in D.C. electric arc furnaces, the electrodes (11) comprising a part (11a) subjected to the hot environment of the furnace, this part being made of graphite in the case of a cathode and of copper in the case of an anode, the part (11a) being associated with a metallic part (11b) by means of a joint (13) which includes inside itself a hollow (14), comprising at least in correspondence with the metallic part (11b) a cooling circuit (20) with at least a delivery channel (15), a return channel (16) and a heat exchanger (18), the circuit (20) using liquid metal as a cooling fluid, there also being included means for the forced circulation of the cooling fluid consisting of a hydromagnetic pump (17).

Abstract: An improved return path for electric current through a conductive hearth of a direct current arc furnace is provided by pressing a ring of water cooled copper blocks into the periphery of a sidewall of the hearth of the furnace, the hearth having zones of conductive refractory providing an electrical path between the contents of the furnace of the copper blocks. The hearth is compressed by a tensioned peripheral band which may also support the blocks. The peripheral water cooled copper blocks may be divided into multiple groups, each group connected to one pole of a direct current power supply, the opposite pole of which is connected to a suspended electrode, permitting control of arc deflection.

Abstract: A d.c. arc furnace for metallurgical purposes includes two or more electrodes arranged on the furnace vessel and projecting into the furnace vessel. To avoid actions of forces departing from the magnetic fields derived form the currents conducted to the electrodes and effecting deflections of the electric arcs, the electric supply means provided for each of the electrodes are each arranged in the immediate vicinity of the electrode to be supplied, the electric supply means of one electrode being arranged so as to be spacially separated from the electric supply means of the remaining electrodes, viewed in the peripheral direction of the furnace vessel.

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 metallurgical vessel heated by direct current, particularly for the production of ferroalloys, including a metallic jacket lined with refractory material and a bottom electrode. A bottom electrode (22) is located within the interior of the vessel and arranged below a refractory side wall (12) of the metallurgical vessel (10). Bottom electrode (22) is constructed from electrically conducting refractory material. The periphery of the electrically conducting bottom (22) is surrounded by metallic plates (25), each of which is connected to current rods (31) which extend through a metallic jacket (11) and out from the vessel. Plates (25) and current rods (31) are separated from the metallic jacket (11) by electrical insulation (32). The electrode device in the bottom of the vessel ensures electrical contact over as large an area as possible.

Abstract: The furnace vessel for a DC arc furnace has a thermostable wall which preferably consists, in the region situated above the slag line (S), of a plurality of water-cooled wall segments (1) made from steel. These wall segments are fastened to a support structure (13-18). At least one of the wall segments (3) consists of nonmagnetic steel or copper and is preferably arranged on the side of the furnace vessel (5) opposite the power supply device (7). In this way, the influence of the high-current lines which extend below or beside the furnace vessel and cause a deflection of the arc can be compensated.The effect of this nonmagnetic wall segment can be partially or virtually entirely cancelled by a trimming plate (19) which is detachably fastened from the outside to the nonmagnetic wall segment (3), in order in this way to achieve optimum trimming of the deflection of the arc.

Abstract: A method and a d.c. arc furnace for thermal treatment of an ash, wherein reducing conditions are established within a closed and sealed furnace, the ash is supplied via a channel arranged in an electrode which extends towards a metal melt in a furnace shell and provides an arc extending toward the metal melt, the ash being fed from the open free end of the electrode through the arc, any slag and/or the metal melt, whereby the ash is rapidly heated under reducing conditions to a temperature of 1350.degree. C. to 1750.degree. C.

Abstract: An apparatus and method for controlling an electroslag remelting furnace, imposing a periodic fluctuation on electrode drive speed and thereby generating a predictable voltage swing signal. The fluctuation is preferably done by imposition of a sine, square, or sawtooth wave on the drive dc offset signal.

Abstract: The electrode gap of a VAR is monitored by determining the skewness of a distribution of gap voltage measurements. A decrease in skewness indicates an increase in gap and may be used to control the gap.

Abstract: The invention relates to a procedure for continuous supply of heat into electrically conductive bulk goods by exploiting the electrical resistance thereof in an oven chamber with an inlet opening and a drawing-off apparatus for continuous throughput of bulk goods, wherein during the throughput of material, electrical energy in the material is conducted, and to an apparatus for continuous supply of heat into electrically conductive bulk goods by exploitation of the electrical resistance thereof, in an oven chamber (1) with an inlet opening (15) and a continuous drawing-off apparatus (9) for the bulk goods, and with at least one pair of electrodes (14, 16, 19) arranged one above the other, via which the electrical energy in the material is conducted during the continuous throughput of material.

Abstract: A cooled bottom electrode for a direct-current electric furnace includes one or more steel bars incorporated in a refractory hearth of the furnace and having at least its upper end in contact with the bath of molten metal within the furnace, at least a first upper liquid part and at least a second lower solid part being defined along the steel bar and being divided by a separation zone, the lower solid part being associated with cooling elements. The cooling elements are copper cooling means elements introduced in cooperation with the solid part of the steel bar and being inserted at least therewithin and extending at least partly within the bar and towards the inside of the furnace. The copper cooling elements cooperate with a cooling-water system positioned below the bar and in cooperation therewith.

Abstract: The information on the state of switchgears (2.1;2.2) appearing on call circuits in the form of analog low-voltage signals is conveyed in parallel to a circuit block (4). The information is digitalized at given points in time in the form of binary values "0" or "1" and is transmitted in series to a microprocessor (1). Preferably the circuit block (4) comprises at least one shift register in cascade connection. Call circuits are coupled to the circuit block solely via a high-impedance resistor (3.1;3.2). The circuit block (4) is supplied by a voltage supply circuit (5) so that when one of the switchgears (2.1;2.2) is in the open state, a current flows alternately via one of the protection diodes (D1S.1,D2S.1;DIS.2,D2S.2) of the circuit block (4), and does not do so when one of the switchgears (2.1;2.2) is in the closed state. To ascertain whether a voltage (U.sub.1,U2) at the input (4.1;4.2) of the circuit block (4) is D.C. or A.C.

Abstract: When operating, DC arc furnaces generate undesired reactive load fluctuations which are compensated without special compensation reactance by a reactive power controller. As compensation reactance, use is made of inductors, which are always present and via which the arc furnace is fed by rectifiers. A current controller is connected to the rectifiers via a first summer. On the input side, the first summer is further operationally connected to the output of the reactive power controller and, as the case may be, to an AC--AC converter which supplies a signal proportional to the power supply voltage (U.sub.xN). In addition, it is possible to provide an inverter which is connected in parallel with the arc furnace on the DC side and which is operationally connected on the AC side to a feeding AC power supply network (N) via a stabilization transformer or via auxiliary windings of a furnace transformer, and to the output of the reactive power controller on the control side.

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: Two upper electrodes 16 and 17 are horizontally spaced apart from each other with a predetermined distance and vertically extend through a furnace roof 3 of a furnace shell 2. Upper conductors 20 and 21 are connected to the upper electrodes 16 and 17 and extend in a direction away from the upper electrodes 17 and 16, respectively. Two lower conductors 22 and 23 are connected to a lower electrode 1 and extend in directions along which the upper conductors 20 and 21, respectively. Power source circuits 24 and 25 are arranged between extension ends of the upper and lower conductors 20 and 22 and 21 and 23, respectively. Arcs 12a and 12b generated between the upper electrodes 16 and 17 and the lower electrode 1 are directed to a center of the furnace shell 2.

Abstract: A direct current electric furnace for melting ferrous raw material, such a scrap iron, comprising a vessel (1) closed by a detachable cover (13), at least one consumable electrode (5) which passes through at least one opening (16) in the cover (13), at least one stationary electrode (5) positioned in the bottom (2) of the vessel (1), and comprising at least one source of direct current, the vessel being defined by a bottom (2) in the shape of a basin (21) and by a lateral wall (12). The height (H1) and the cross-section (S1) of the basin (21) are determined by the conditions of use, such that the basin (1) (21) can contain a prescribed quantity of molten metal, the height (H2) of the lateral wall (12) of the vessel (1) being such that the vessel (1) can accommodate a sufficient charge of scrap iron (7) to produce, in a single melting operation, the prescribed quantity of a molten metal.

Abstract: A metallurgical container of the type having a vessel having a bottom wall and an inner refractory lining includes a hearth bottom electrode extending through the bottom wall and the lining and including, in a superposed condition, a bar and a connector. The bar is flush with the surface of the refractory lining. The connector is fastened to a lower surface of the bar, is internally cooled, has a diameter smaller than the diameter of the bar, and is attached to the bar at its upper front face at a level within the thickness of the refractory lining. A ring is interlocked to the vessel wall, surrounds the connector, and has an upper face located below the bar so as to be capable of carrying the bar. In order to prevent liquid materials from penetrating by infiltration between the bar and the ring, the bar is prolonged or elongated toward the bottom wall by a skirt which surround the connector laterally. The invention is particularly applicable to direct current operated steel plant arc furnaces.

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 direct current electric arc furnace for melting metal, which furnace includes a furnace vessel having a lower vessel part lined with a refractory material and a metal upper vessel part through which a cooling agent can flow. A cover is adapted and arranged to close the furnace vessel. Electric current is fed to the furnace, by an arrangement including a main electrode extending into the furnace vessel through the cover, a bottom electrode located at the bottom of the lower vessel part, and feed lines that connect the electrodes to a direct current source. The feed lines include at least two current feeds connected to the bottom electrode, each current feed having a line segment parallel to a main axis of the main electrode and a shield for at least partially magnetically shielding the upper vessel part at an arc level from magnetic fields generated by the line segments parallel to the main axis.

Abstract: The method relates to the operation of a D.C. electric-arc furnace provided with at least one bottom electrode including an elongated metal current-supply body passing through the hearth of the furnace and surrounded by a casing made of dense refractory substance, comprising at least one shell ring whose upper end comes into contact with the molten metal in the furnace. During restarting of the furnace after shut-downs, a free expendable annular part made of refractory material, of flattened general shape, is placed on the upper end of the shell ring, which part extends it upwards and is intended to come into contact with the molten metal instead of said shell ring. The method applies in particular to D.C. electric-arc furnaces for the manufacture of steel, and is intended to reduce wear on the refractory parts surrounding the bottom electrode.

Abstract: A DC arc furnace according to the invention has a bottom electrode, which comprises a plurality of contact pins each having an end to be brought into contact with an object and to supply arc-forming current thereto, a current base electrically connected to the other end of each of the contact pins for distributing current from a power supply to the contact pins, and a cooling device for cooling the current base with the use of cooling water.

Abstract: Provided are a furnace shell with a lower electrode at a bottom of the shell, a furnace roof adapted to close an upper portion of the furnace shell, a material charge port substantially at a center of the furnace roof and two upper electrodes positioned laterally opposite to each other with respect to the material charge port and vertically extending through the furnace roof. Scrap material is continuously charged through the material charge port and arcs are directed to the scrap material at a center of the furnace shell.

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: 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: According to the present invention, there is provided a direct current electric furnace for melting metal capable of melting scraps rapidly and also capable of diminishing cold and hot spots formed on the furnace wall, wherein the direct current electric furnace is provided with a single top electrode, a plurality of furnace bottom electrodes, or a plurality of electrode units obtained by dividing a multitude of furnace bottom electrodes of a small diameter into plural units, and electric current controlling thyristor circuits for controlling each individually electric currents flowing through the plural furnace bottom electrodes or electrode units. The electric current controlling thyristor circuits may be substituted by thyristor circuits for controlling electric currents for each of plural groups obtained by dividing the above plural furnace bottom electrodes or the above many furnace bottom electrodes or the above plural electrode units into the plural groups.

Abstract: Direct-current smelting furnace with control of deflection of the electric arc, which comprises an upper electrode (13) with relative return-flow lines and a plurality of bottom electrodes (11) positioned on the hearth of the furnace (12) and arranged in two or more assemblies, each assembly having its own controlled supply line connected to its own transformer (16), there being included downstream of each transformer (16) its own thyristor rectifier assembly (17) associated with its own means to control voltage (26), current (24) and firing angle (23), at least the lines supplying the bottom conductors (32) being at least partly screened in the vicinity of the melting furnace (12)