US3361862A - System for supplying power to an electric arc metallurgical furnace - Google Patents

System for supplying power to an electric arc metallurgical furnace Download PDF

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Publication number
US3361862A
US3361862A US375139A US37513964A US3361862A US 3361862 A US3361862 A US 3361862A US 375139 A US375139 A US 375139A US 37513964 A US37513964 A US 37513964A US 3361862 A US3361862 A US 3361862A
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US
United States
Prior art keywords
nozzle
electrode
arc
furnace
electric arc
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US375139A
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English (en)
Inventor
William R Sturrock
Allen J Baker
Henry W Mcrobbie
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Union Carbide Corp
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Union Carbide Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Union Carbide Corp filed Critical Union Carbide Corp
Priority to US375139A priority Critical patent/US3361862A/en
Priority to GB23008/65A priority patent/GB1113448A/en
Priority to SE7605/65A priority patent/SE317755B/xx
Priority to FR20336A priority patent/FR1445772A/fr
Priority to NL656507585A priority patent/NL139037B/nl
Application granted granted Critical
Publication of US3361862A publication Critical patent/US3361862A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H1/00—Generating plasma; Handling plasma
    • H05H1/24—Generating plasma
    • H05H1/26—Plasma torches
    • H05H1/32—Plasma torches using an arc
    • H05H1/34—Details, e.g. electrodes, nozzles
    • H05H1/36—Circuit arrangements
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B7/00—Heating by electric discharge
    • H05B7/005—Electrical diagrams

Definitions

  • Electric furnaces have long been used in practicing etallurgical processes.
  • At least one directionally stable transferred electric arc column is established in a furnace containing conductive charge material.
  • Power dissipation in such electric arcs is virtually constant and controllable.
  • Arc length, of a directionally stable are as a variable in determining the voltage drop across the arc, can be maintained constant or it can be smoothly varied at will to meet the particular power input requirement in a given process commensurate with maximum dissipation of heat energy in the are for a given power supply.
  • the power input can be controlled and optimized to meet the requirements of a particular process, that is the melting rate may be increased as required in a particular process by increasing the voltage drop across the are column. This is in sharp contrast to standard furnace practice wherein power input is in essence not controlled smoothly by affirmatively adjusting arc length responsive to the desired power input level but rather it is sought to suppress the erratic changes in the length of a relatively short are.
  • the directionally stable transferred DC. are column is established between a non-consumable electrode, for example tungsten, and a water-cooled bottom electrode positioned beneath the conductive charge material with the electron current path being between the non-consumable electrode through the charge material to the bottom electrode.
  • a non-consumable electrode for example tungsten
  • a water-cooled bottom electrode positioned beneath the conductive charge material with the electron current path being between the non-consumable electrode through the charge material to the bottom electrode.
  • the device having the nonconsumable electrode has a water-cooled copper nozzle provided with a central gas passage through which the current carying arc and are effluent passes on its way to the charge material.
  • the tungsten electrode carries .a major part of the current for only half cycles, it can carry a higher current than it would in ordinary DC. operation.
  • a water-cooled bottom electrode in a hot metallurgical furnace is a safety hazard. Water-cooled or not there is always a possibility of loss of melt from the furnace into the electrode pit. It is not always possible to insure electrical contact between the scrap and the bottom electrode into the melt may be undesirable from a metallurgical standpoint.
  • Another object is to provide a novel power supply circuit from a polyphase A.C. source to a plurality of directionally stable are devices in an electric arc furnace.
  • a further object is to provide such a power supply circuit from a polyphase A.C. source to a plurality of directionally stable are devices having a tungsten electrode surrounded at least at its arcing end by a cooled copper nozzle.
  • FIGURE 1 being a schematic diagram of a preferred embodiment of the invention
  • FIGURE 2 is an alternative form of the invention
  • FIGURE 3 is an illustration of a single arc device arrangement
  • FIGURE 4 is an illustration of a two are device arrangement.
  • a three phase are transformer noted generally at T is preferably delta connected on the primary side 1 to a 4-40 volt three phase line.
  • the secondary side 3 of transformer T is preferably Y connected.
  • Each phase 5, 7 and 9 respectively of the secondary Y 3 is split into two legs noted by the reference characters 11 and 13 for phase 5; 15 and 17 for phase 7; and 19 and 21 for phase 9.
  • Legs 11, 15 and 19 are each connected to a non-consumable electrode 23, 25, 27.
  • Such electrode is preferably made from 2% thoriated tungsten.
  • a rectifying element 29, 31, 33 is connected in each leg 13, 17 and 21 between nozzle 35, 37, 39 and the secondary of transformer T.
  • the secondary side of transformer T is usually Y connected.
  • the Y connection provides a higher voltage than does a delta connected secondary and also allows a center point connection to the bath, if desired or necessary.
  • a delta connected secondary is also within the scope of this invention.
  • a tungsten electrode is preferred because of its high melting point and low voltage requirements at high current densities.
  • Other materials may be selected according to their effect on the metallurgical process being performed in the furnace so long as the material is a good electron emitter.
  • a typical directionally stable arc device containing a tungsten electrode and admirably suited for practicing the present invention is described by R. M Gage in US. Patent 2,806,124 issued Sept. 10, 1957.
  • the rectifying elements 29, 31 and 33 are preferably silicon diodes. However, germanium or selenium rectifiers are also suitable for practicing the invention.
  • three torches A, B and C are placed in an appropriate electric furnace *F.
  • the arc is established between the torches A, B and C and the metallic bath shown symbolicially at M by touching the electrodes 23, 25 and 27 to the bath M.
  • pilot-arc power supply systems can be connected between each of electrodes 23, 25 and 27 and the nozzles 35, 37 and 39 whereby a pilot arc is first established therebetween prior to and as an auxiliary for starting the main arc.
  • the arc length is adjusted to a desired length depending on the process conditions necessary within the open circuit range of the power supply being utilized. The process is continued until the terminal point is reached.
  • FIGURE 2 is an alternative form of the power supply circuit of the invention.
  • parts identical with the parts illustrated in FIGURE I bear identical reference characters differing therefrom merely by a prime.
  • an additional silicon diode 4t), 42 and 44- is connected in legs 11, 15 and 19 of each phase between the non-consumable electrodes 23, 25 and 27' and the secondary 3 of transformer T.
  • the additional diode insures that electron current does not flow through the tungsten electrode on the positive half cycle when current should be flowing through the nozzle element.
  • the embodiment shown in FIGURE 2 was identical to that shown in FIGURE 1.
  • the A.C. power source could be a Y connected secondary of a 3-phase arc transformer with the center of the Y connected to the bath M.
  • the power source could be a single phase are transformer with one top connected to the work and the other to point 52.
  • a silicon diode is connected to leg 47 between the nozzle 49 and the A.C. source.
  • the other leg 51 of the single phase power is connected to a non-consumable electrode 53.
  • the arc is established by touch starting the electrode 53 to the bath M.
  • Two torches E and D may be operated from a single phase are transformer power source as shown in FIG- URE 4.
  • one tap of the secondary of the transformer shown in block form is connected to point '54 at torch D and the other tap is connected to point 56 at torch E.
  • a silicon diode 55 and 57 is connected in the circuit from nozzle h and 61 to the power source.
  • Another circuit to the power source includes tungsten electrodes 63 and 65. The are is established by touching electrodes 63 and 65 to the bath M.
  • electron current passes from the A.C. source to electrode 65 through bath M, to nozzle 59 of torch D through rectifier 55 back to the A.C. source.
  • On the reverse cycle electron current flows from the source through electrode 63 to the bath M through nozzle 61 of torch E and rectifier 57 to the source.
  • FIG- URES 3 and 4 could be further modified to include a rectifier element between the non-consumable electrodes and the power source.
  • An electric arc metallurgical furnace containing a charge of raw material electrically conductive at least in the molten state including a devlce for producing a directionally stable are having an electrode and a nozzle surrounding and radially spaced from said electrode so as to provide a passage for are gas to flow between said electrode and nozzle in combination with an electrical circuit comprising an A.C. power source, at least one rectifying element connected between said power source and said nozzle so that said nozzle will collect electrons when said nozzle is electrically positive with respect to said molten bath.
  • An electric arc furnace power system according to claim 2 wherein silicon diodes are in both legs of each phase of said three phase A.C. source between said A.C. source and said electrode and nozzle respectively.
  • An electric arc metallurgical furnace containing a molten bath of electrically conductive material including an arc torch device having a non-consumable tungsten electrode and a water-cooled copper nozzle at least partially surrounding and radially spaced from said tungsten electrode as to provide a passage for arc gas to fiow between said tungsten electrode and copper nozzle incombination with an electrical circuit comprising an A.C. power source including an arc transformer connected in circuit with said are torch, at least one rectifying element connected between said are transformer and said copper nozzle of said are torch so that said copper nozzle will collect electrons when said nozzle is electrically positive with respect to said molten bath.
  • An electric arc metallurgical furnace containing a molten bath of electrically conductive material including at least three are torch devices having a non-consumable tungsten electrode and a water-cooled copper nozzle at least partially surrounding and radially spaced from said tungsten electrode as to provide a passage for are gas to flow between said tungsten electrode and copper nozzle in combination with an electrical circuit comprising at least a three phase AC.
  • power source including an are transformer connected in circuit with said arc torch, at least one rectifying element connected between said are transformer and said copper nozzle of each of said are torches so that said copper nozzles will collect electrons when said nozzles are electrically positive with respect to said molten bath.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Discharge Heating (AREA)
  • Silicon Compounds (AREA)
  • Furnace Details (AREA)
  • Vertical, Hearth, Or Arc Furnaces (AREA)
US375139A 1964-06-15 1964-06-15 System for supplying power to an electric arc metallurgical furnace Expired - Lifetime US3361862A (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
US375139A US3361862A (en) 1964-06-15 1964-06-15 System for supplying power to an electric arc metallurgical furnace
GB23008/65A GB1113448A (en) 1964-06-15 1965-05-31 Improvements in or relating to systems for supplying electrical power to metallurgical arc fornaces
SE7605/65A SE317755B (nl) 1964-06-15 1965-06-09
FR20336A FR1445772A (fr) 1964-06-15 1965-06-10 Système d'alimentation en énergie électrique de fours électriques
NL656507585A NL139037B (nl) 1964-06-15 1965-06-14 Inrichting voor het voeden van een elektrische vlamboogoven uit een wisselstroombron.

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US375139A US3361862A (en) 1964-06-15 1964-06-15 System for supplying power to an electric arc metallurgical furnace

Publications (1)

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US3361862A true US3361862A (en) 1968-01-02

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US375139A Expired - Lifetime US3361862A (en) 1964-06-15 1964-06-15 System for supplying power to an electric arc metallurgical furnace

Country Status (5)

Country Link
US (1) US3361862A (nl)
FR (1) FR1445772A (nl)
GB (1) GB1113448A (nl)
NL (1) NL139037B (nl)
SE (1) SE317755B (nl)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3524006A (en) * 1967-10-19 1970-08-11 Qualitats Und Edelstahl Kom Ve Method and apparatus for controlling arc discharge in plasma arc furnaces
US4694464A (en) * 1986-07-30 1987-09-15 Plasma Energy Corporation Plasma arc heating apparatus and method

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2145310B (en) * 1981-03-19 1985-11-20 Loughborough Consult Ltd Generating a plurality of electric discharges, plasma torches

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2907807A (en) * 1957-03-26 1959-10-06 Gen Electric Electric circuit for cold crucible arc melting furnaces

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2907807A (en) * 1957-03-26 1959-10-06 Gen Electric Electric circuit for cold crucible arc melting furnaces

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3524006A (en) * 1967-10-19 1970-08-11 Qualitats Und Edelstahl Kom Ve Method and apparatus for controlling arc discharge in plasma arc furnaces
US4694464A (en) * 1986-07-30 1987-09-15 Plasma Energy Corporation Plasma arc heating apparatus and method

Also Published As

Publication number Publication date
SE317755B (nl) 1969-11-24
NL139037B (nl) 1973-06-15
FR1445772A (fr) 1966-07-15
GB1113448A (en) 1968-05-15
NL6507585A (nl) 1965-12-16

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