Industrial electric heating furnaces – Arc furnace device – Power supply system
Patent
1997-06-02
1998-12-01
Hoang, Tu B.
Industrial electric heating furnaces
Arc furnace device
Power supply system
373108, H05B 711
Patent
active
058449337
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a d.c. arc furnace for metallurgical purposes comprising two or more electrodes arranged on the furnace vessel and projecting into the furnace vessel.
A d.c. arc furnace of this type is known, for instance, from U.S. Pat. No. 3,949,151. That furnace comprises three electrodes arranged in a radially symmetrical manner, viewed in the ground section of the furnace, wherein the electric supply means for feeding said electrodes are arranged to be concentrated on one side of the furnace. Each of the electrodes is supplied with current by a separate rectifier, the high current lines being conducted around the furnace to the respective electrodes to be fed, departing from the rectifier stations arranged on one side of the furnace.
The high current lines are surrounded by strong electric fields inducing electric-arc deflections of the electric arcs burning between the electrode tips and the metal melt. This results not only in a strongly non-uniform consumption of the electrodes, but also in a strongly thermal overload exerted on the brickwork of the furnace vessel. To avoid such phenomena, six anodes are provided in the bottom of the d.c. arc furnace according to U.S. Pat. No. 3,949,151, which anodes are connected with the electrodes projecting from top into the furnace via a separate switch mechanism. That known electrode arrangement and its special circuit is expensive in terms of construction and circuitry and, i.a., causes the furnace to function like an a.c. furnace.
SUMMARY OF THE INVENTION
The invention aims at avoiding these disadvantages and difficulties and has as its object to avoid, in a d.c. arc furnace of the initially defined kind comprising several electrodes, electric arc deflections brought about by the action of forces of the magnetic fields derived from the currents conducted to the electrodes. The electric arcs are to burn uniformly throughout the total period of operation of a furnace and in a direction that can be exactly predetermined in order to avoid thermal asymmetry within the d.c. arc furnace and hence elevated wear of the brickwork of the furnace vessel.
In accordance with the invention, this object is achieved in that 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 spatially separated from the electric supply means of the remaining electrodes, viewed in the peripheral direction of the furnace vessel.
The arrangement of the electric supply means, such as rectifier throttles, etc., each in the immediate vicinity of the respective electrode minimizes the unilateral asymmetrical mutual influence of the electrodes the more so as in that case the high current lines directly lead to the supply means by a short way.
According to a preferred embodiment, the high current line conducted to one electrode--viewed in the ground section of the d.c. arc furnace--is arranged so as to extend in an approximately radial direction relative to the vertical central axis of the furnace as far as to a rectifier station associated with this electrode.
Preferably, the electrodes and the high current lines are arranged in an approximately radially symmetrical manner. Thereby, unilateral forces of the magnetic fields acting asymmetrically on the electric arcs of the electrodes may be completely avoided.
Suitably, each electrode is associated with a separate rectifier station, which--viewed in the ground section of the d.c. arc furnace--is each arranged in a region in the radial extension of the electrode.
To realize savings with the electric supply means, each electrode, according to a preferred embodiment, is associated with a separate rectifier station, at least two rectifier stations each being connected to a common transformer station.
In the following, the invention will be explained in more detail by way of an exemplary embodiment represented in the drawing, the drawing schematically illustra
REFERENCES:
patent: 3949151 (1976-04-01), Kerton
patent: 5204873 (1993-04-01), Hiroshi
patent: 5590152 (1996-12-01), Nakajima et al.
Stahl und Eisen, vol. 114, No. 5, 16 May 1994 pp. 37-41, 133, XP 000448184.
Kohle S `Gegenuberstellung von Gleichstrom- und Drehstrom- Lichtbogenofen Comparison of Direct-Current and Three-Phase A.C. Arc Furnaces`.
Aigner Bernhard
Berger Harald
Mittag Peter
Hoang Tu B.
Voest-Alpine Industrien-lagenbau GmbH
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