Canadian Patents Database / Patent 2391385 Summary

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(12) Patent: (11) CA 2391385
(54) English Title: METHOD AND APPARATUS TO FACILITATE RESTRIKING IN AN ARC-FURNACE
(54) French Title: PROCEDE ET DISPOSITIF FACILITANT LE REDRESSAGE DANS UN FOUR A ARC
(51) International Patent Classification (IPC):
  • H05H 1/48 (2006.01)
  • H05H 1/36 (2006.01)
(72) Inventors (Country):
  • BEAUREGARD, FRANCOIS (Canada)
  • FRANCOEUR, BRUNO (Canada)
(73) Owners (Country):
  • HYDRO-QUEBEC (Canada)
(71) Applicants (Country):
  • CENTRE D'INNOVATION SUR LE TRANSPORT D'ENERGIE DU QUEBEC (Canada)
(74) Agent: NORTON ROSE FULBRIGHT CANADA LLP/S.E.N.C.R.L., S.R.L.
(45) Issued: 2009-06-09
(86) PCT Filing Date: 2000-11-16
(87) PCT Publication Date: 2001-05-25
Examination requested: 2005-10-13
(30) Availability of licence: N/A
(30) Language of filing: English

(30) Application Priority Data:
Application No. Country Date
PCT/CA99/01091 Canada 1999-11-16
60/166,406 United States of America 1999-11-19

English Abstract




To re-ignite efficiently an arc-furnace arc extending between an electrode and
a material to be melt, a second energy
supply is provided to maintain a plasma link between the electrode and the
melting material when the arc-furnace arc is interrupted.
The electrode is supplied by a large current power supply including a large
current conductor having a self inductance and being
connected to the electrode. The second energy supply is an electrical power
supply wherein a high frequency bypass impedance is
provided in a supply path to the large current conductor at a distance from a
capacitive circuit to allow a high frequency resonant
circuit to be formed by the conductor section between the capacitive circuit
and the bypass impedance without adversely affecting
the large current power supply of the arc furnace. The capacitive circuit
comprises an HF power supply injected in resonance with
the resonant circuit to build an oscillating voltage and use the oscillating
voltage to inject an HF current between the electrode and
the melting metal in order to maintain the plasma link.





French Abstract

Selon l'invention, afin de rallumer de manière efficace un arc de four à arc s'étendant entre une électrode et un matériau à fondre, une seconde alimentation en courant est pourvue afin de conserver une liaison plasma entre l'électrode et le matériau en fusion au moment où l'arc du four à arc est interrompu. L'électrode est pourvue par une alimentation en courant importante comprenant un conducteur de courant important possédant un coefficient d'auto-induction et étant relié à l'électrode. La seconde alimentation en courant est une alimentation en courant électrique, une impédance de dérivation haute fréquence étant pourvue dans une voie d'alimentation au conducteur de courant important à une certaine distance du circuit capacitif afin de permettre la formation d'un circuit résonnant haute fréquence par la section du conducteur située entre le circuit capacitif et l'impédance de dérivation, sans que cela n'entrave l'alimentation en courant importante du four à arc. Le circuit capacitif comprend une alimentation en courant HF injectée en résonance avec le circuit résonnant afin de construire une tension oscillante et d'utiliser celle-ci pour injecter du courant HF entre l'électrode et le métal en fusion de façon à conserver la liaison plasma.


Note: Claims are shown in the official language in which they were submitted.




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CLAIMS


1. An apparatus to facilitate re-striking of an electrical arc in an arc-
furnace having a large geometry current conductor with a high-current
power supply connected to one end of said large geometry current
conductor and an electrode connected to the other end of said large
geometry current conductor to produce said electrical arc for melting
metal, the apparatus further comprising a quasi-continuous electrical
energy supply adapted to maintain a plasma link between the end of
said electrode and said melting metal,

wherein said quasi-continuous electrical energy supply is HF AC and
wherein said HF AC electrical energy supply includes a resonant circuit
utilizing a major section of an inductor formed by the self inductance of
said large geometry current conductor; and an HF power source
operating near or at the resonant frequency of said resonant circuit and
connected to said large geometry current conductor on the electrode
side.


2. An apparatus as claimed in claim 1, wherein said HF AC electrical
energy supply comprises a resonant capacitor connected to said large
geometry current conductor on the electrode side, further wherein said
resonant capacitor forms said resonant circuit with said self inductance.

3. An apparatus as claimed in claim 1, further comprising an HF
bypass-impedance connected in a supply path to said large geometry
current conductor at a distance from said resonant capacitor.


4. An apparatus as claimed in any one of claims 1 to 3, wherein said
quasi-continuous electrical energy supply is of sufficient strength to
initiate said plasma link between the end of said electrode and said
melting metal.


5. An apparatus as claimed in any one of claims 1 to 4, wherein said




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quasi-continuous electrical energy supply has a sufficient strength to
maintain said plasma link of a length greater than the maximum length
of said electrical arc.


6. An apparatus according to any one of claims 1 to 3, wherein the
frequency of said HF AC supply is located at about 100 kHz.


7. An apparatus according to any one of claims 1 to 3, further
comprising a ferromagnetic member surrounding said large geometry
current conductor, wherein the ferromagnetic material exhibits a high
permeability for magnetic field generated by a current in said large
geometry current conductor below a maximum resonant current of said
resonant circuit, and goes rapidly into saturation for said current in said
large geometry current conductor being higher than said maximum
resonant current and below a current of said electrical arc.


8. An apparatus according to any one of claims 2, 3 and 7, wherein said
resonant capacitor comprises an HF capacitor; an LF blocking
capacitor; and an LF bypass inductor to separate the HF voltage and an
LF voltage.


9. An apparatus according to claim 3, wherein said HF bypass-
impedance also bypasses the insulation between said high-current
power supply and its conductive enclosure thereof.


10. An apparatus according to claims 3 and 9, wherein said HF bypass-
impedance is essentially provided by a capacitor.


11. An apparatus according to anyone of claims 1 to 10, wherein said
HF power source includes a controller capable of tracking said resonant
frequency and adjusting the frequency of said HF power source.


12. An apparatus according to claim 11, wherein said controller cuts-out
an integral number half cycles from said HF power source in order to




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limit the resonant voltage appearing at said electrode.


13. An apparatus according to claim 11, wherein said controller begins
said tracking when an extinction of said electrical arc is detected.


14. An apparatus according to claim 11, wherein said tracking is
performed all the time that said power supply is on.


15. An apparatus according to claim 11, wherein said HF power source
operates at a standby frequency when the resonant voltage or current
of said resonant circuit is below a threshold.


16. An apparatus according to any one of claims 1 to 15, further
comprising a shielded HF supply cable, wherein said HF power source
is located at a safe distance from the harsh environment of said arc-
fumace and is connected to said large conductor beside said resonant
capacitor via said HF supply cable.


17. An apparatus according to claim 16 wherein said HF supply cable
comprises a coaxial cable.


18. An apparatus according to claim 17 wherein said coaxial cable
comprises: a core supporting member, a first conductor layer
surrounding said supporting member; a second conductor layer
surrounding said first conductor layer and separated from said first
conductor layer by a dielectric layer; and an outer protective jacket.


19. An apparatus according to claim 18, wherein said core supporting
member incorporates at least one channel to allow a cooling fluid to
flow there through.


20. An apparatus according to anyone of claims 16, 17, 18, 19 wherein
said HF supply cable comprises a snubber circuit at one end to
attenuate cable reflections.





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21. An apparatus according to claim 20 wherein said snubber circuit
comprises a resistor, an HF bypass capacitor and an LF bypass
inductor.


22. An apparatus according to anyone of claims 1 to 21, comprising a
sliding contact for delivering the quasi-continuous electrical energy of
said quasi-continuous electrical energy supply.


23. The apparatus as claimed in any one of claims 1 to 22, wherein said
high-current power supply is an AC power supply.


24. A method for melting metal in an arc-furnace using an electrical arc,
the method comprising the steps of: feeding a high current, from a high-
current power supply, using a large geometry current conductor and an
electrode, to said electrical arc, between said electrode and said
melting metal of said arc furnace; injecting quasi-continuous electrical
energy at the end of said electrode; maintaining a plasma link with said
injected quasi-continuous electrical energy, between said electrode and
said melting metal at each extinction of said electrical arc for a duration
long enough to allow the voltage of said high current power supply to
regain a value that will reestablish said electrical arc;

wherein said step of injecting quasi-continuous electrical energy at the
end of said electrode is accomplished using a resonant circuit
comprising a major section of an inductor formed by the self inductance
of said large geometry current conductor, and an HF power source
operating near or at the resonant frequency of said resonant circuit and
connected to said large geometry current conductor on the electrode
side.


25. A method as claimed in claim 24, wherein said plasma link has a
length greater than a maximum length of said electrical arc.





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26. A method as claimed in claim 24, further comprising the step of:
initiating said plasma link between said electrode and said melting
metal without making a mechanical contact between said electrode and
said melting metal.


27. A method as claimed in claims 24 to 25, further comprising the
steps of: positioning said electrode to increase the voltage of said
electrical arc to provide higher power in said electrical arc, said
electrical arc being less stable during operating conditions; wherein said
maintaining is carried out without altering the distance between said
electrode and said melting metal.



A single figure which represents the drawing illustrating the invention.

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Admin Status

Title Date
(86) PCT Filing Date 2000-11-16
(87) PCT Publication Date 2001-05-25
(85) National Entry 2002-05-13
Examination Requested 2005-10-13
(45) Issued 2009-06-09

Maintenance Fee

Description Date Amount
Last Payment 2017-10-19 $450.00
Next Payment if small entity fee 2018-11-16 $225.00
Next Payment if standard fee 2018-11-16 $450.00

Note : If the full payment has not been received on or before the date indicated, a further fee may be required which may be one of the following

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Payment History

Fee Type Anniversary Year Due Date Amount Paid Paid Date
Registration of Documents $100.00 2002-05-13
Filing $300.00 2002-05-13
Maintenance Fee - Application - New Act 2 2002-11-18 $100.00 2002-05-13
Maintenance Fee - Application - New Act 3 2003-11-17 $100.00 2003-10-23
Maintenance Fee - Application - New Act 4 2004-11-16 $100.00 2004-10-22
Registration of Documents $100.00 2005-04-18
Request for Examination $800.00 2005-10-13
Maintenance Fee - Application - New Act 5 2005-11-16 $200.00 2005-11-02
Maintenance Fee - Application - New Act 6 2006-11-16 $200.00 2006-10-27
Maintenance Fee - Application - New Act 7 2007-11-16 $200.00 2007-10-24
Maintenance Fee - Application - New Act 8 2008-11-17 $200.00 2008-10-28
Final $300.00 2009-03-20
Maintenance Fee - Patent - New Act 9 2009-11-16 $200.00 2009-10-27
Maintenance Fee - Patent - New Act 10 2010-11-16 $250.00 2010-10-25
Maintenance Fee - Patent - New Act 11 2011-11-16 $250.00 2011-10-28
Maintenance Fee - Patent - New Act 12 2012-11-16 $250.00 2012-10-29
Maintenance Fee - Patent - New Act 13 2013-11-18 $250.00 2013-10-24
Maintenance Fee - Patent - New Act 14 2014-11-17 $250.00 2014-10-27
Maintenance Fee - Patent - New Act 15 2015-11-16 $450.00 2015-10-28
Maintenance Fee - Patent - New Act 16 2016-11-16 $450.00 2016-10-20
Maintenance Fee - Patent - New Act 17 2017-11-16 $450.00 2017-10-19

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Representative Drawing 2002-05-13 1 10
Representative Drawing 2002-10-17 1 6
Representative Drawing 2008-12-01 1 6
Description 2002-05-13 33 1,470
Abstract 2002-05-13 2 74
Claims 2002-05-13 5 207
Drawings 2002-05-13 15 349
Cover Page 2002-10-18 1 47
Claims 2007-10-16 5 162
Claims 2008-09-25 5 185
Cover Page 2009-05-13 1 47
PCT 2002-05-13 15 517
Prosecution-Amendment 2007-04-17 3 84
Prosecution-Amendment 2005-10-13 1 36
Prosecution-Amendment 2007-10-16 8 247
Prosecution-Amendment 2008-03-26 2 56
Prosecution-Amendment 2008-09-25 8 306
Correspondence 2009-03-20 2 57