JP3857098B2 - Arc current controller for arc furnace - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an arc current control device for an arc furnace used for producing a single crystal material.
[0002]
[Prior art]
For example, in order to manufacture a magnetic material, the chocolate ski method is used as one method for growing a single crystal material from a polycrystalline material.
[0003]
In this method, for example, as shown in FIG. 1, a polycrystalline material 9 is placed on a base plate 5 made of a water-cooled hollow conductor, and the whole is placed in a bowl-shaped cylindrical chamber 3.
[0004]
Then, the inside of the chamber 3 is filled with an inert gas, and the tips of the plurality of electrodes 8 and 8 inserted obliquely downward from the upper side of the chamber are brought close to the upper surface of the polycrystalline material. An arc is generated between them.
[0005]
The reason why the plurality of electrodes 8 are provided in the chamber 3 as described above is to increase the heat generation amount by increasing the number of arcs and to increase the yield of the single crystal material per unit time.
[0006]
Since high heat is generated by this arc discharge, the upper surface of the polycrystalline material 9 is melted by the arc heat, and a melt is locally formed.
[0007]
On the other hand, a pulling shaft 12 that can be moved up and down is disposed at the center of the upper surface of the chamber. A seed crystal 15 is attached to the tip of the pulling shaft 12 and is brought into contact with the melt.
[0008]
Thereafter, when the pulling shaft 12 is slowly raised while rotating, the single crystal material 16 grows from the seed crystal 15 and is pulled up.
[0009]
While monitoring the diameter of the single crystal material and the state of the melt, the pulling speed of the pulling shaft is changed to control the diameter so that it is always constant, and thus the single crystal material is manufactured from the polycrystalline material.
[0010]
Stabilization of the arc generated between each electrode and the material in the melting process of the polycrystalline material by the arc heat described above is one of the most important issues in stabilizing the quality of the formed single crystal material. .
[0011]
Therefore, the holder 7 holding each electrode 8 is always cooled by cooling water, and the holder 7 can be moved up and down, and the tip of the electrode and the polycrystalline material are made so that the arc current is constant. Control the distance between the surfaces.
[0012]
This type of arc furnace that has been used in the past has a structure in which power is supplied in parallel to a plurality of electrodes by a single DC power supply for a furnace, and the control of the arc current for each electrode is exclusively for that electrode. This configuration is performed only by controlling the distance between the tip and the material.
[0013]
[Problems to be solved by the invention]
However, the arc furnace having the above-described structure has different electric resistances caused by different arrangements of the electrodes 8 in the chamber 3, different cooling effects due to the inert gas, or different cooling effects for each holder 7. The arc current for each electrode changes slightly.
[0014]
Therefore, in a conventional arc furnace that supplies power to multiple electrodes in parallel by a single DC power supply for a furnace, a stable arc necessary to form a higher quality single crystal is generated for each electrode. It is difficult to do.
[0015]
This is because the distance between each electrode and the polycrystalline material must be adjusted from electrode to electrode and mechanically to adjust the arc current.
[0016]
Accordingly, the present invention provides an arc current control device that can easily adjust the arc current at each electrode to an optimum value in an arc furnace that uses a plurality of electrodes, and aims to eliminate the above-described disadvantages. Yes.
[0017]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is an arc furnace that uses a plurality of electrodes and connects each electrode to an independent DC power source for furnaces to supply power, and is assigned to each DC power source for each furnace. A common variable resistor connected in parallel to each individual adder circuit adjusts the arc current of each DC power supply for each furnace simultaneously and in common, and by an individual variable resistor connected to each adder circuit, The arc current of each DC power supply for each furnace can be adjusted individually.
[0018]
【Example】
Hereinafter, the present invention will be described based on embodiments shown in the drawings.
In FIG. 1, reference numeral 1 denotes the entire arc furnace, and a hollow cylindrical chamber 3 is hermetically installed on the upper surface of a base frame 2 of the arc furnace 1.
[0019]
A main shaft 4 with a base plate 5 attached to the upper end is disposed at the center of the chamber 3. The main shaft 4 and the base plate 5 integral with the main shaft 4 are moved up and down and rotated in the base frame 2. The mechanism 6 can move up and down and rotate around a vertical axis.
[0020]
Further, four holders 7 are disposed on the outer peripheral portion of the upper wall of the chamber 3 so as to be obliquely downward, and an electrode 8 made of a heat-resistant conductor such as tungsten is concentric with the holder at the tip of each holder 7. It is attached to.
[0021]
On the other hand, the polycrystalline material 9 is placed at the center of the upper surface of the base plate 5, and the tips of the four electrodes are close to the polycrystalline material 9.
[0022]
A positive terminal of a furnace DC power source 22 (see FIG. 2) to be described later is connected to the shaft 4 via the brush 10 and further connected to the polycrystalline material 9 via the base plate 5.
[0023]
Further, the negative terminal of the furnace DC power supply 22 is connected to the electrode 8 through the holder 7.
[0024]
Therefore, when electric power is supplied from the DC power supply 22 for the furnace, an arc 11 is generated between the electrode 8 and the polycrystalline material 9 and becomes high temperature, and the upper surface of the polycrystalline material 9 is locally melted to melt the melt. Is generated.
[0025]
On the other hand, a pulling device 13 is installed on the upper surface of the base frame 2 so that the pulling shaft 12 is moved up and down, and the seed crystal 15 is held by the chuck 14 at the lower end of the pulling shaft 12. ing.
[0026]
When the pulling shaft 12 is lowered to bring the seed crystal 15 into contact with the melt and then gradually lifted while rotating the shaft 12, the single crystal material 16 grows from the seed crystal and is pulled up. An ingot of crystalline material is formed.
[0027]
Although not shown, each member constituting the chamber 3, the shaft 4, the base plate 5, the holder 7, etc. has a double-walled jacket structure and is cooled by a coolant such as water. Since this structure is the same as that of a general arc furnace, further detailed description is omitted.
[0028]
Further, the inside of the chamber 3 is filled with an inert gas such as argon to form an inert zero atmosphere, and this point is also the same as that of a general single crystal manufacturing apparatus, and thus further detailed description is omitted.
[0029]
Next, an arc current control device that is the gist of the present invention, that is, a system for supplying electric power to the electrode 8 will be described.
[0030]
In FIG. 2, the electric power supplied from the primary power source 20 passes through the circuit breaker 21 and is supplied to furnace DC power sources (hereinafter referred to as DC power sources) 22a, 22b corresponding to the four electrodes 8a, 8b, 8c, 8d. , 22c and 22d.
[0031]
The positive terminal of each DC power supply is connected to the shaft 4 via the brush 10.
In addition, a common variable resistor 24 and independent variable resistors 25a, 25b, 25c, and 25d are connected to the control terminals of each DC power supply for the furnace via addition circuits 23a, 23b, 23c, and 23d, respectively. Yes.
[0032]
Therefore, the resistance value of the common variable resistor 24 and the respective resistance values of the variable resistors 25a, 25b, 25c, and 25d are added to the control terminals of the DC power supplies 22a, 22b, 22c, and 22d. It is connected.
[0033]
On the other hand, as described above, the negative terminal of each DC power source is connected to each electrode, and the positive terminal is connected to the polycrystalline material 9, and an arc is generated between the electrode and the polycrystalline material. As described above, the polycrystalline material is melted by arc heat.
[0034]
When a voltage is applied between the electrode 8 and the polycrystalline material 9 to generate an arc by generating an arc, the arc current is maintained in a stable state in order to generate the melt in a stable and good state. It is one of the important issues.
[0035]
The arc current also changes depending on the distance between the electrode 8 and the surface of the polycrystalline material 9, but particularly changes significantly depending on the arc voltage applied between them, so that the arc voltage is kept constant in an arc furnace. It is important to maintain.
[0036]
On the other hand, the arc voltage applied to each electrode is also caused by a difference in electrical resistance value of each wiring due to a difference in arrangement of each electrode, a difference in cooling effect by an inert gas, or a difference in cooling effect for each holder. Different.
[0037]
Therefore, in the present invention, the above-described difference in electric resistance for each electrode is adjusted by operating the individual variable resistors 25a, 25b, 25c, and 25d, and on the other hand, it is common to increase or decrease the arc current all at once. The variable resistor 24 is adjusted by operating, and the resistance value is added by the adder circuits 23a, 23b, 23c, and 23d to adjust the arc voltage.
[0038]
In this type of conventional arc furnace, since four electrodes are connected to one DC power supply for a furnace, it is difficult to adjust the arc current for each electrode. For example, the adjustment is easy for each electrode. Once adjusted, the arc current can be increased or decreased by adjusting the common variable resistor 24, for example, when four electrodes are evenly consumed. It becomes.
[0039]
【The invention's effect】
As is clear from the above description, according to the present invention, each electrode is connected to a DC power supply for a furnace, and each electrode is connected via an adder circuit by one common variable resistor and individual variable resistors. Since the arc current of each electrode is controlled, the arc for each electrode can be maintained in the best stable state and the operation can be simplified.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of an arc furnace according to the present invention.
FIG. 2 is a block circuit diagram of an arc current control device according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Arc furnace 2 Base frame 3 Chamber 4 Shaft 5 Base plate 7 Holder 8 Electrode 8a Electrode 8b Electrode 8c Electrode 8d Electrode 9 Polycrystalline material 10 Brush 11 Arc 12 Pulling shaft 15 Seed crystal 16 Single crystal material 22 DC power source 22a for furnace DC power source 22b Furnace DC power source 22c Furnace DC power source 22d Furnace DC power source 23a Adder circuit 23b Adder circuit 23c Adder circuit 23d Adder circuit 24 Common variable resistor 25a Individual variable resistor 25b Individual variable resistor 25c Individual Variable resistor 25d Individual variable resistor

Claims (1)

An arc furnace that uses a plurality of electrodes and supplies power by connecting an independent DC power supply for each electrode to each electrode, and is connected in parallel to individual adder circuits assigned to each DC power supply for each furnace A common variable resistor adjusts the arc current of each furnace DC power supply simultaneously and in common, and an individual variable resistor connected to each adder circuit individually adjusts the arc current of each furnace DC power supply. An arc current control device for an arc furnace, characterized by being able to do so.

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