JPH0534070A - Power supply switching device in one-power supply, two-furnace body dc electric furnace - Google Patents

Abstract

PURPOSE:To switch a power supply efficiently with a simple and small-sized constitution by a method wherein means, providing a switch consisting of a predetermined electrode and a device holding the electrode and connecting it electrically and the like, are contrived in a power supply switching device for applying electric current through a plurality of electric furnaces alternately with a single power supply. CONSTITUTION:Normally, an electrode 8 is penetrated through a cooling device 12 and the lower end thereof is fixed by the fixed side electrode clamping device 7 of a fixed side electrode holder 6. Upon power feed, a movable side electrode holder 9 is descended by an electrode holder elevating device 11 and the upper end of the electrode 8 is fixed by a movable electrode clamping device 10. Upon intercepting the power supply, the electrode 8 is separated from the movable side electrode holder 9 and, thereafter, the movable side electrode holder 9 is ascended. Then, a thyristor is controlled by a switch and one switching device between respective power supply switching devices 33a, 33b in a plurality of furnaces is controlled so as to be in exciting condition while the other one between the power supply switching devices 33a, 33b is controlled so as to be in power shut-off condition respectively, alternately and selectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct current electric furnace for metal melting and refining, and more particularly to a single electric power source / two furnace body type direct current electric furnace.

[0002]

2. Description of the Related Art Generally, an AC three-phase type arc furnace has been used as an electric furnace for metal melting and refining represented by steelmaking, but in recent years, a DC arc furnace has been developed and is in operation. In this DC arc furnace, only one graphite electrode is required for the cathode, so the electrode unit consumption can be greatly improved, and the electrical efficiency and molten steel agitation are good, and the heat dissipation loss is small, so the power unit consumption is improved. Since there are no hot spots, the furnace unit refractory unit consumption can be improved, the flicker level can be significantly improved, and noise is small.

Unlike a three-phase AC arc furnace, a DC arc furnace is one in which an anode is installed on the furnace bottom and an arc is generated with a graphite electrode of the cathode, so the furnace bottom side electrode is air-cooled or water-cooled. However, it has reached the end of its life in a short period of time and must be replaced. Further, since a power transformer requires an A / D conversion facility in addition to a transformer for a furnace, the DC arc furnace has generally adopted a one-power-one-furnace method although the electric room is large. Therefore, in the case of an electric furnace with one power source and one furnace body, production stoppage occurs due to replacement of the bottom electrode. On the other hand, if a plurality of furnace bodies are used as measures against this, a space for arranging an electric chamber for each arc furnace is taken, A large installation area is required as a whole.

[0004]

In the conventional electric furnace with one power source and one furnace body, when the electric power is cut off, a circuit breaker is installed in front of the transformer in the three-phase AC electric furnace and an AC in the DC electric furnace.・ In the DC converter (generally using a thyristor), the method of breaking each is used. In the case of a DC electric furnace with one power source and two furnace bodies devised to solve the above problems, a cathode composed of a graphite electrode alternately supplies electricity by alternately using the two furnace bodies in one set of devices. However, since the anode is installed in the furnace bottom of each furnace body in a fixed state as a furnace bottom electrode, the two furnace bodies are always in a charged state on the anode side during energization.

In order to solve this problem, a power source switching device is installed at any position between the DC converter and the bottom electrode of the secondary conductor that is branched into two furnace bodies after the DC converter. However, the current passing through the power switching device is 100,000 amps or more, and the conventional circuit breaker requires a very large capacity device, or multiple circuit breakers must be installed. There were challenges.

The present invention has been made in order to solve these problems, and an object of the present invention is to make full use of the advantages of a DC arc furnace while efficiently operating a DC arc in a relatively small installation area. To provide a power supply switching device for switching the anode side power supply of each furnace body with a simple configuration and by using one or two switching devices in a one-power-two-body DC electric furnace that can be well implemented. ..

[0007]

According to the present invention, two electric furnaces of the type in which a DC arc is formed between a graphite electrode on the cathode side and a furnace bottom electrode on the anode side are alternately energized by one power source. In the power supply switching device, an electrode made of graphite or other conductive material capable of passing a current of 100,000 amperes or more between the respective anodes and the power supply, and an electrical element by holding the electrode. A switch constituted by an electrode gripping device connected to the electrode gripping device is incorporated, and electrode cooling means for cooling the electrode is provided between the electrode gripping devices.

[0008]

In the current switching device of the present invention, when the electrode holding device holds the electrode made of graphite or other conductive material in the switch part, the furnace bottom electrode is connected to the power source and the electrode holding device is released from the holding device. As a result, the furnace bottom electrode and the power supply are cut off.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an overall configuration diagram of a DC electric furnace for metal melting and refining using a power supply switching device of the present invention, and FIG. 2 is a schematic configuration diagram of the power supply circuit of FIG. In the figure, 1a and 1b are 2
It is a furnace body of the base electric furnace (the furnace body 1b is not shown in FIG. 1), and is installed in the abutment equipment 2 that constitutes the working floor. At the bottom of these furnace bodies 1a and 1b, furnace bottom electrodes 3 are attached to the respective furnace bodies as anodes.

The furnace bottom electrode 3 may be an arbitrary steel pin or the like, and is cooled by a water cooling or air cooling device (not shown). Reference numeral 4 denotes an electric room, which includes a control measurement panel 29, a furnace transformer 30, a thyristor 31, a DC reactor 32, power source switching devices 33a and 33b, a water-cooling flexible cable 34, a water-cooling conductor 35, and the like.

On the side wall of the front furnace body, the cathode side terminal 3 is connected to the cathode side of the thyristor 31 by a water-cooled conductor.
6, power supply switching device 3 arranged for each furnace body 1a, 1b
3a and 33b, and power source switching devices 33a and 33b are provided with an anode-side terminal 37 connected to an end terminal by a water-cooling flexible cable 34.

The cathode side terminal 36 is connected to a furnace body side terminal 42, a secondary conductor 43, an electrode holder 44 and a graphite electrode 45 via a water cooling flexible cable 41. Also, each of the two anode side terminals 37 is
It is connected to the furnace bottom electrode 3 via a water cooling flexible cable 46, a furnace body side terminal 47, and a water cooling conductor (not shown).

FIGS. 3 and 4 are enlarged views of the power supply switching device of FIG. The power supply switching devices 33a and 33b include a switch 5 having fixed and movable electrode holders 6 and 9 on both terminals, an electrode 8, and electrode tightening devices 7 and 10.
It is composed of an electrode holder lifting device 11 and the like. The fixed-side electrode holder 6 includes a fixed-side electrode tightening device 7, which is connected to a water-cooling conductor 35 connected to the DC reactor 32, and the movable-side electrode holder 9 includes a movable-side electrode tightening device 10, which is water-cooled to an anode terminal 37. It is connected to the terminal 13 of the cable 34. The movable electrode holder 9 is moved up and down by the electrode holder lifting device 11. Further, a cooling device 12 for the electrode 8 is provided between the electrode holders of the switch 5. Further, 14 is an electrode elevating device that elevates and lowers the electrode 8 when the electrode 8 is replaced, and 15 and 16 are discharge preventing devices and discharge preventing device driving devices that are optionally provided.

The joints between the electrode holders 6 and 9 and the electrodes 8 are made of a conductive metal such as copper, and the drive unit and the conductors are electrically insulated by an insulator 17.

Next, the energization / interruption operation of the power source of the electric furnace of this construction will be described. Usually, the electrode 8 penetrates the cooling device 12, and the lower end thereof is fixed by the fixed side electrode tightening device 7 of the fixed side electrode holder 6. 9 may be lowered to a predetermined position, and the upper end of the electrode 8 may be clamped and fixed by the movable side electrode clamping device 10. On the other hand, in order to cut off the electricity, first, the movable side electrode tightening device 10 is released, and the movable side electrode holder 9 and the electrode 8 are cut off. Next, the movable-side electrode holder 9 is raised by the electrode holder lifting device 11 and stopped at a predetermined position. Stop position is electrode 8
Between the movable electrode holder 9 and the movable side electrode holder 9, a distance is maintained to prevent discharge, or a position where the discharge prevention device driving device 16 can install the discharge prevention device 15 at a predetermined position.

All of the above operations can be carried out by installing an operating device in the electric furnace operating room that can be automatically interlocked.

According to the electric furnace of this structure, the power is turned off in the thyristor 31 by the operation switch in the electric furnace operation chamber to make it in the non-energized state, and the one of the furnaces 1a (the one through which electricity has been supplied until now) is The power supply switching device 33a is turned off, and in parallel with this, the other furnace 1b
Power source switching device 33 for the furnace from which electricity will be passed
Energize b. After confirming this state, by turning on the power inside the thyristor 31 by the operation switch in the electric furnace operating room, even if the other furnace 1b is in the energized state, one furnace 1a is not charged, and Other work such as charging can be performed with confidence.

FIG. 5 shows details of the graphite electrode used as the electrode 8 in the above embodiment. Electrode lifting device 1 at the upper end
4 is provided with a threaded portion 21 for attachment / detachment, the cross-sectional area S of the electrode is set to be large enough to allow a necessary current (100,000 amperes or more) to flow, and the length L is sufficient to prevent discharge between the holders when energized. Length. Further, instead of the graphite electrode, a copper or aluminum electrode may be used.

On the cathode side of the electric furnace, one graphite electrode 45 may be alternately used for each electric furnace 1a, 1b, or each furnace may be provided with a graphite electrode 45. The power supply switching device may be provided on the bottom electrode side.

[0020]

When the power supply switching device of the present invention is used, the power supply to the anode side bottom electrode can be cut off with a relatively simple device, and one or two power supply switching devices can be used. 1 power source 2 furnace body It becomes possible to operate efficiently by taking advantage of the features of the DC electric furnace.

In particular, when a graphite electrode is used as the electrode of the power supply switching device, the contact surface with the metal part of the electrode gripping device is familiar and the maintenance of the metal side is easy and long-term use is possible. Become. Further, since the graphite electrode is cooled as much as possible without arc discharge, it can be used with almost no damage, and can be used as a cathode of an electric furnace after being used in a power source switching device. Furthermore, there is an effect that the electrodes can be easily replaced.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a DC electric furnace for metal melting and refining using a power supply switching device of the present invention.

FIG. 2 is a schematic configuration diagram of the power supply circuit of FIG.

FIG. 3 is an enlarged view of a power supply switching device section.

FIG. 4 is an enlarged view of a power supply switching device section.

FIG. 5 is a partial cross-sectional view of an electrode used in the power supply switching device.

[Explanation of symbols]

 1a, 1b Electric furnace 3 Bottom electrode 4 Electric chamber 5 Switch 6 Fixed side electrode holder 8 Electrode 9 Movable side electrode holder 11 Electrode holder lifting device 12 Cooling device 33a, 33b Power supply switching device

Claims (1)

Claim: What is claimed is: 1. A power supply switch for alternately energizing two electric furnaces of a type in which a DC arc is formed between a graphite electrode on the cathode side and a furnace bottom electrode on the anode side with one power source. In the apparatus, an electrode made of graphite or other conductive material capable of passing a current of 100,000 amperes or more and an electrode are held between the bottom electrode of each of the electric furnaces and the power source. A power supply in a two-body DC electric furnace, characterized in that a switch constituted by an electrode gripping device electrically connected to each other is incorporated, and electrode cooling means for cooling the electrode is provided between the electrode gripping devices. Switching device.