JPH06314591A - Polyphase ac multipole arc discharge device - Google Patents

Abstract

PURPOSE:To provide an arc and a plasma at high efficiency by providing the same number of discharge electrodes as the number of phases of polyphase a.c., and disposing the discharge electrodes with their end portions forming a regular polygon, and applying the polyphase a.c. in order of phase, thereby causing a planar arc discharge. CONSTITUTION:In a six-phase current six-pole arc discharge device, a six-phase AC output device S and bar-shaped discharge electrodes T1-T6 are connected to each other in predetermined order. The six-phase AC output device S outputs six monophase alternating currents A1-A6 of 60 deg. phase difference to each other in sequence, and the discharge electrodes T1-T6 are disposed with their respective ends at the vertexes of a regular hexagon using an insulating electric holder H. Three monophase alternating currents of 120 deg. phase are applied to every other electrode T1-T6 and monophase alternating currents of opposite phases are applied to each pair of opposite electrodes. The applied voltage for unit distance between electrodes can be held constant among all the electrodes and the total of fifteen planar arc discharges are continuously caused while being rotated at high speed, whereby a high-efficiency discharge can be achieved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an arc discharge device capable of generating a surface arc which is surprisingly highly efficient.

[0002]

2. Description of the Related Art Arc discharge is a kind of gas discharge phenomenon characterized by low voltage and large current. It generates extremely high heat and intense light, and is therefore widely used in various fields as a heat source or a light source. . And in order to efficiently use the high energy associated with discharge in each field, many improvements have been positively made, for example, by providing a cooling nozzle around the discharge electrode and injecting argon gas or the like from there. There is.

However, all of the conventional arc discharge devices use a single-phase AC or DC power supply as their power source, and the discharge phenomenon itself which generates high energy is linear between the pair of electrodes. However, there was a limit to improving these energy use efficiency.

[0004]

SUMMARY OF THE INVENTION Therefore, according to the present invention, arc discharge can be generated with extremely high efficiency by causing the discharge itself, which emits high energy, to have a planar shape instead of the conventional linear shape. It is a technical object to provide a multi-phase AC multi-electrode arc discharge device.

The present applicant has already developed a 6-phase AC 6-electrode arc discharge device constructed by devising the connection order of the 6-phase AC power source and the 6 electrodes arranged at each vertex of the regular hexagon, and applied for a patent. (Japanese Patent Application No. 4-228984). This device
By applying a voltage corresponding to the distance between the electrodes to each electrode, it is possible to generate a plurality of arc discharges between the six electrodes in a planar manner while rotating at high speed without interruption. The applicant of the present application continued to carry out experimental research on this discharge phenomenon, and as a result, this planar discharge that generated surprisingly high energy was observed in the number of phases other than 6-phase AC, that is, in n-phase AC-n electrode device. We have succeeded in solving the above-mentioned technical problems by finding out that the above-mentioned technical problems can also occur, and utilizing the laws of nature that act there.

[0006]

[Means adopted for solving the problem] At least 7
In an arc discharge device in which a multi-phase alternating current of four or more phases or a four-phase alternating current or a five-phase alternating current is applied to discharge electrodes provided in the same number as the number of phases, the discharge electrodes have a regular polygonal shape. The means for arranging and applying the multi-phase alternating current to the discharge electrode in the order of their phases is adopted.

Further, in an arc discharge device in which a three-phase alternating current is applied to three discharge electrodes, the discharge electrodes are arranged so that their tips form an equilateral triangle, and near the center of the equilateral triangle. By adopting the technical means of providing the ground electrode, the above problems have been solved.

[0008]

EXAMPLES First, 6-phase AC-6, which was the starting point of the present invention
An arc discharge device using this electrode will be described with reference to FIGS. 1 is a schematic perspective view illustrating the configuration of a 6-phase AC 6-electrode arc discharge device, FIG. 2 is an explanatory view of a discharge path of a planar arc discharge generated by the device, and FIG. A vector diagram of phase alternating current, and FIG. 4 is an explanatory diagram of a distance between electrodes in the same apparatus.

As shown in FIG. 1, the 6-phase AC 6-electrode arc discharge device is a 6-phase AC output device designated by the symbol S and a symbol T.
_The rod-shaped discharge electrodes indicated by _{1 to} T ₆ are connected in a predetermined connection order. The 6-phase AC output device S includes six single-phase ACs A _{1 to} A ₆ having a phase difference of 60 ° (the phase sequence is A ₆ → A ₅ → A ₄ → A ₃ → A ₂ → A ₁ → A). ₆ ), and the six discharge electrodes T _{1 to} T ₆ are held by the insulating electrode holder designated by the symbol H in a state in which the tips thereof are closely arranged near the respective vertex positions of the regular hexagon. ing.

Then, among the single-phase ACs A _{1 to} A ₆ output from the output terminals of the 6-phase AC output device S, three single-phase ACs having a phase difference of 120 ° are discharged to the discharge electrodes T _{1 to} T. Every other ₆ is applied, and single-phase alternating currents having opposite phases are connected to the electrodes facing each other. When this connection method is adopted and the discharge is started, as shown in FIG. 2, a total of 15 arc discharges are aligned without interruption in the area surrounded by the discharge electrodes T _{1 to} T ₆ and the discharge order is followed. It was generated in a plane while rotating at high speed, and surprisingly highly efficient discharge was obtained. In addition,
FIG. 2 shows the discharge path at each instant when the phase advances by 30 °, and the thick arrows in the figure indicate that the maximum voltage value is applied between the electrodes and the discharge current flows in the direction of the arrow. The thin arrows indicate that a voltage is applied between the electrodes, but a discharge current flows in the direction of the arrow when a voltage is applied.

In a 6-phase AC 6-electrode arc discharge device,
The reason why such planar discharge is possible is that the applied voltage per unit distance between the electrodes can be made constant between all the electrodes. Since a correspondingly higher voltage is applied between the electrodes with a large distance, not only the discharge between adjacent electrodes with a short distance, but also the arc discharge with another electrode with a large distance, as in the conventional device. It can happen. This will be described in detail with reference to FIGS. 3 and 4.

FIG. 3 is an AC vector diagram showing the magnitude and phase relationship of the AC voltage. The 6-phase AC output device S (see FIG.
When the six alternating currents A _{1 to} A ₆ output from the reference line) are represented by thick line vectors E _{1 to} E ₆ in the figure, the voltage applied between the electrodes is equal to the thick line vector E _{1 to} E ₆ . Each can be represented by a vector difference. In the figure, by using thin line vectors V _{12 to} V ₁₆ , the discharge electrode T ₁ and the other electrodes T ₂ to
It represents the inter-electrode voltage applied between T ₆ and the electrode.

Here, when the magnitudes of the thick line vectors E _{1 to} E ₆ are E, the thin line vector V ₁₂ representing the voltage between the electrodes T _{1 and} T ₂ is the thick line vector E ₁ and the thick line vector E ₂ . Therefore, the magnitude thereof is E, and similarly, the magnitude of the vector V ₁₃ representing the voltage between the electrodes T _{1 and} T ₃ is √3E and the voltage between the electrodes T _{1 and} T _4. The magnitude of the vector V ₁₄ is 2E, the magnitude of the vector V ₁₅ representing the voltage between the electrodes T _{1 and} T ₅ is √3E, and the magnitude of the electrode T ₁ −
The magnitude of the vector V ₁₆ representing the voltage between T ₆ is 1E
become.

On the other hand, looking at the distance between the discharge electrode T ₁ and the other electrodes T _{2 to} T ₆ , when the distance between the center of the regular hexagon and each vertex is L, as shown in FIG. Electrode T
The distance between ₁ and the electrode T ₂ is L, and similarly the electrode T ₁ −
Distance between T ₃ ; √3L, distance between electrodes T _{1 and} T ₄ ; 2
L, distance between discharges T ₁ -T ₅ ; √3L, electrodes T ₁ -T ₆
Distance between them: 1L.

As can be seen from this relationship, in the 6-phase AC 6-electrode arc discharge device, the discharge electrode T ₁ -the other electrode T
And between the inter-electrode application voltage V ₁₂ ~V ₁₆ and the electrode distance is to correspond beautifully in between ₂ through T _6. Specifically, for example, the electrode T ₁ − whose distance is √3 times the distance between the electrodes T ₁ −T ₂ −
Between T _3, √3 times the voltage between the electrodes T ₁ -T ₂ is applied, the distance is doubled to become electrodes T ₁ -T between electrodes T ₁ -T ₂
The voltage twice between the electrodes T _{1 and} T ₂ is applied between the _four . This relationship is defined by the discharge electrode T ₁ -the other electrodes T _{2 to} T _{2.
The same} can be seen not only between the electrodes ₆ but also between the discharge electrode T ₂ and the other electrodes T _{3 to} T ₆ . As a result, the discharge electrodes T _{1 to} T
_{6 As a} whole, highly efficient planar discharge is generated.

The applicant of the present invention has found that the proportional relationship between the voltage applied between the electrodes and the distance between the electrodes is not limited to arc discharge by 6-phase AC-6 electrodes, but also 3-phase, 5-phase, 12-phase, etc. It was found that even if other multi-phase alternating current is adopted, it can be maintained as long as the connection order described below is observed.

That is, it suffices to connect each phase of the n-phase alternating current to the n discharge electrodes whose tips are closely arranged at the apexes of the regular n-sided polygon in the order of their phases in the clockwise or counterclockwise order. is there. Then, as in the case of the above-mentioned 6-phase AC 6-electrode arc discharge, when the discharge voltage applied between all the n discharge electrodes is an n-phase AC represented by an AC vector diagram, the vector This is because it is expressed by a difference, and these vector differences correspond proportionally to the side length and the diagonal line length of the regular n-sided polygon.

That is, as shown in FIG. 3, when the six-phase alternating current is expressed by an alternating current vector diagram, thick line vectors E _{1 to} E
₆ forms a regular hexagon (shown by a dotted line in FIG. 3), and discharge voltage (fine line vectors V _{12 to} V ₁₆ ) to be applied between the electrodes.
Etc.) correspond to the sides and diagonals of this regular hexagon. Therefore, if the discharge electrodes T _{1 to} T ₆ are arranged at the respective vertex positions of the regular hexagon and a 6-phase alternating current is sequentially applied to the discharge electrodes T _{1 to} T ₆ , a regular hexagon formed by the vector (see FIG. 3).
(See FIG. 4) and the discharge electrodes T _{1 to} T ₆ form a regular hexagon (see FIG. 4).
Therefore, the proportional relationship between the inter-electrode applied voltage and the inter-electrode distance is maintained among all the electrodes.

Therefore, also in the arc discharge device using the multi-phase AC-multi-electrode, the discharge electrodes are arranged at the apex positions of the regular polygon so as to correspond to the regular polygon formed by the vector,
Similar to the above-mentioned 6-phase AC 6-electrode arc discharge device, highly efficient planar arc discharge can be generated by simply connecting the multi-phase AC in order of their phases.

The first and second embodiments according to the present invention will be described below with reference to FIGS.
FIG. 5 is a partial perspective view for explaining the structure of the discharge electrodes of the 12-phase AC 12-electrode arc discharge device of the first embodiment, and FIG. 6 is a voltage vector diagram of the AC voltage applied between the electrodes of the device, FIG. 7 is a composite vector diagram of alternating current applied between each electrode of the device,
8 and 9 are views for explaining the discharge path of the arc discharge generated by the same device, FIG. 10 is a partial perspective view for explaining the structure of the discharge electrode of the three-phase AC four-electrode arc discharge device of the second embodiment, and FIG. It is a synthetic | combination vector figure of the alternating current applied between each electrode of the arc discharge by 3 phase alternating current 3 electrode.

[First Embodiment] The first embodiment is a 12-phase AC-
It is an arc discharge device with 12 electrodes. As shown in FIG. 5, the rod-shaped discharge electrodes T _{1 to} T ₁₂ are supported by an insulating electrode holder H so that the tip portions thereof are arranged near the apex positions of the regular dodecagon. This discharge electrode T ₁ ~
₁₂ single-phase alternating currents A _{1 to} A ₁₂ output from a 12-phase alternating current power supply (not shown) to T ₁₂ (phase order is A ₁₂ → A ₁₁ → ... → A ₁ → A
₁₂ ) are applied in the order of their phases in the clockwise direction (or may be in the counterclockwise direction) toward the drawing.

The voltages of the single-phase alternating currents A _{1 to} A ₁₂ applied from the 12-phase AC power source to the discharge electrodes T _{1 to} T ₁₂ are the electrodes T ₁ ;
Let sin θ be the electrode T ₂ ; sin (θ + 2π / 12),
Electrode T ₃ ; sin (θ + 4π / 12), electrode T ₄ ; sin (θ +
6π / 12), electrode T ₅ ; sin (θ + 8π / 12), electrode T ₆ ;
sin (θ + 10π / 12), electrode T ₇ ; sin (θ + 12π / 12),
Electrode T ₈ ; sin (θ + 14π / 12), electrode T ₉ ; sin (θ +
16π / 12), electrode T ₁₀ ; sin (θ + 18π / 12), electrode T ₁₁ ;
sin (θ + 20π / 12), electrode T ₁₂ ; sin (θ + 22π / 12),
Can be expressed as Therefore, the voltage between the electrodes T _{1 and} T ₂ ; sin θ−sin (θ + 2π / 12) = − (√3-1) / √2cos (θ + π / 12), and similarly, the voltage between the electrodes T _{1 and} T ₃ ; − cos (θ + 2π / 12), voltage between electrodes T _{1 and} T ₄ ; −√2cos (θ + 3π / 12), voltage between electrodes T _{1 and} T ₅ ; −√3cos (θ + 4π / 12), between electrodes T _{1 and} T _6. Voltage;-(√3 + 1) / √2cos (θ + 5π /
12) Electrode T ₁ -T ₇ voltage; -2cos (θ + 6π / 12) Electrode T ₁ -T ₈ voltage;-(√3 + 1) / √2cos (θ + 7π /
12) between the electrodes T ₁ -T ₉ voltage; -√3cos (θ + 8π / 12 ), the voltage between the electrodes _{T 1 -T 10; -√2cos (θ} + 9π / 12), between the electrode T ₁ -T ₁₁ voltage; -cos ( θ + 10π / 12), voltage between electrodes T _{1 and} T ₁₂ ; − (√3-1) / √2cos (θ + 11π
/ 12).

Then, the discharge electrode T ₁ and the other electrodes T _{2 to} T ₁₂
Since the discharge electrodes T _{1 to} T ₁₂ are arranged at the respective vertex positions of the regular dodecagon, the distance between the electrodes T _{1 and} T _{3 is}
When the distance between the electrodes is L, the distance between the electrodes T _{1 and} T _{2 is} (√3-1) / √2L, the distance between the electrodes T _{1 and} T _{4 is} √2L, the distance between the electrodes T _{1 and} T _{5 is} √ 3L, distance between electrodes T ₁ -T ₆ ; (√3 + 1) / √2L, distance between electrodes T ₁ -T ₇ ; 2L, distance between electrodes T ₁ -T ₈ ; (√3 + 1) / √2L, electrode T ₁ -T ₉ distance: √3L, electrode T ₁ -T ₁₀ distance: √2L, electrode T ₁ -T ₁₁ distance: L, electrode T ₁ -T ₁₂ distance: (√3-1) / √2L Becomes

As described above, also in the 12-phase AC 12-electrode arc discharge device, the applied voltage between the electrodes and the distance between the electrodes correspond excellently. Specifically, for example, the distance; (√3-1) / √2L between the electrodes T _{1 and} T ₂ is −
(√3-1) / exchange √2cos (θ + π / 12) is applied, the distance; is between the electrodes T ₁ -T ₄ of √2L, -√2cos (θ +
An alternating current of 3π / 12) is applied.

That is, since the maximum applied voltage per unit distance between the electrodes is equal among all the electrodes, not only the discharge between adjacent electrodes having a short distance but also the discharge between other electrodes is performed. It will be.

Next, from the discharge electrode T ₁ to the other electrodes T _{2 to} T ₁₂
The change with time of the discharge to is explained. FIG. 6 is a vector diagram of the applied voltage to the other electrodes T _{2 to} T ₁₂ of the discharge electrode T _{1 at} a certain moment. Other electrodes T _{2 to} T _{12 of} discharge electrode T ₁
Each discharge against changes momentarily,
These discharge changes are performed uniformly. That is, as shown in FIG. 7, each discharge is continuous so that the combined vector F obtained by combining all the discharge vectors for the other electrodes T _{2 to} T ₁₂ of the electrode T ₁ rotates in an elliptical locus. It will change to.

Then, as shown in FIG. 7, the discharge electrode T
_At the moment when the combined vector F of ₁ is directed to the midpoint between the electrodes T ₈ and T ₉ , the discharge reaches the electrodes T ₈ and T ₉ mainly from the discharge electrode T ₁ while being divided and bent. . That is, in the discharge device of this embodiment, not only the discharge on the straight line connecting the electrode T ₁ and the other electrodes T ₂ · T ₃ ... T ₁₂ but also the discharge to other spaces. Such a composite vector F also exists in the other electrodes T _{2 to} T ₁₂ , as well,
By coordinating the plurality of rotation combined vectors, uniform and stable planar arc discharge is generated between the discharge electrodes T _{1 to} T ₁₂ as a whole. The state of the planar arc between the discharge electrodes T ₁ through T ₁₂ shown in FIG.

FIG. 8 shows the discharge path at each instant when the phase advances by 15 °. The arrow in the figure indicates that the maximum voltage value is applied between the electrodes and the discharge current flows in the direction of the arrow. As is apparent from FIG. 8, even in the discharge device of this embodiment, a plurality of discharges are always generated at the same time at any moment, and the plurality of discharges are aligned and rotated. Discharge is 1 per AC cycle
Since it rotates, when a power source with a frequency of 50 or 60 Hz is used, the planar discharge formed by a plurality of aligned discharges rotates at a high speed of 50 or 60 times per second.

Further, although FIG. 8 shows only the discharge to which the maximum voltage value is applied, as shown in FIG. 9, a large number of discharges are actually generated between the other electrodes. The discharge path shown in FIG. 9 is at the instant of phase 0 ° in FIG. When the maximum voltage value is applied between the electrodes and the discharge indicated by the thick arrow occurs, a voltage, which is not the maximum value, is applied between the other electrodes as shown by the thin line, so that the discharge is performed. At the moment of FIG. 9, the electrodes T ₁ -T ₇ , the electrodes T ₂ -T ₆ , the electrodes T ₃ -T ₅ , the electrodes T ₈ -T _12, and the electrodes T ₉ -T ₁₁ are equipotential. Excluding 61 discharges, a total of 61 discharges occur in a region surrounded by the electrodes T ₁ to T ₁₂ in a substantially high density in a substantially downward direction toward the drawing.

In the multi-phase AC multi-electrode arc discharge device according to the present invention as in this embodiment, the higher the number of phases of the multi-phase AC, the higher the density of the arc discharge can be obtained. . Note that in FIG. 9, the discharge path is represented by a straight line in order to simplify the state of discharge, and the entire discharge path has a mesh shape, but the actual discharge is divided or bent as described above. Discharge electrodes T _{1 to} T
_It is made in a uniform plane between _{12 and} .

"Second Embodiment" The second embodiment is a three-phase alternating current-
It is an arc discharge device with four electrodes. As shown in FIG. 10, rod-shaped discharge electrodes T _{1 to} T ₃ are arranged so that the tip portions are arranged in the vicinity of the respective vertex positions of an equilateral triangle, and further, a rod-shaped ground electrode T ₀ is attached to the tip portion. It is provided as if it were located at the center point of an equilateral triangle. To the discharge electrodes T ₁ through T ₃ of the three single-phase AC A ₁ to A ₃ (phase sequence output from the 3-phase AC power source (not shown) A ₃ → A ₂ → A ₁
→ A ₃ ) are applied in the clockwise order toward the drawing in the order of their phases.

Here, temporarily, in the three-phase AC three-electrode arc discharge device in which the ground electrode T ₀ is not installed and only the _three electrodes T _{1 to} T ₃ are arranged near the respective vertex positions of the equilateral triangle, Consider a rotational composite vector F ₁ based on the electrode T ₁ as described in the embodiment (see FIG. 11).

Even in the case of the three-phase AC three electrodes, the rotational combined vector F ₁ changes every moment in an elliptical locus as shown in FIG. 11, so that the combined vector F ₁ is the electrodes T ₂ and T _3. angle is the moment of directing midpoint is not present, the electrode T ₂ direction as viewed from the electrode T ₁ in the discharge device, the electrode T ₁ seen from electrode T ₃ direction and, namely ∠T
₂ T ₁ T ₃ is too large at 60 ° (the maximum among other multi-phase AC multi-electrode arc discharge devices. In the case of the above-mentioned 12-phase AC 12-electrode device ∠T ₈ T ₁ T ₉ = 15 °), Although the actual discharge path is divided or bent, the discharge hardly reaches the center of the equilateral triangle formed by the electrodes T _{1 to} T ₃ . To solve this difficulty,
In this embodiment, the ground electrode T ₀ is provided near the center point of the equilateral triangle.

In the case of the three-phase AC four-electrode arc discharge of this embodiment, since the three-phase AC having the smallest number of phases is adopted, the other multi-phase AC multi-electrodes according to the present invention are used in terms of discharge density and the like. Although it does not reach the arc discharge device, it is still possible to generate a planar arc, and it is convenient in that a commonly used three-phase AC power supply can be used.

The embodiment which is a specific example of the present invention is constructed as described above, but the present invention is not limited to the above-mentioned embodiment, and various modifications are made within the scope of the claims. It can be changed. For example, the multi-phase alternating current applied to the discharge electrode is not limited to the three-phase, six-phase, and twelve-phase alternating current, and five-phase, seven-phase, and eleven-phase alternating current may be adopted. . n
A planar arc discharge can be obtained by arranging the same number of discharge electrodes as the number of phases of the phase alternating current at each vertex position of the regular n-sided polygon, and applying the multiphase alternating current to the discharge electrodes in order. .

[0036]

As described above with reference to the embodiments, in the multi-phase AC multi-electrode arc discharge device according to the present invention, the poly-phase AC is arranged in the phase order, and the tips are arranged close to the regular polygon apex position. As long as they are connected so as to be applied to the plurality of discharge electrodes in the clockwise or counterclockwise order, a plurality of arc discharges can be generated in a plane while aligning the discharge directions and rotating at high speed without interruption. it can. Therefore, it is possible to provide an arc discharge device which generates a surprisingly highly efficient arc and plasma jet with an extremely simple structure.

In addition to high heat, the apparatus of the present invention is capable of intense ultraviolet radiation and generation of a large amount of ozone, so that not only arc welding work but also incineration and decomposition of various wastes and purification and sterilization of waste water are performed. The device of the present invention has a wide range of applications, such as being used for, for example, a planar arc lamp that emits planar light.

[Brief description of drawings]

FIG. 1 is a schematic perspective view illustrating the configuration of a 6-phase AC 6-electrode arc discharge device.

FIG. 2 is an explanatory view of a discharge path of a planar arc discharge generated by the device.

FIG. 3 is a vector diagram of 6-phase alternating current applied to the device.

FIG. 4 is an explanatory diagram of a distance between electrodes in the same device.

FIG. 5 is a partial perspective view illustrating the configuration of the discharge electrode of the 12-phase AC 12-electrode arc discharge device according to the first embodiment of the present invention.

FIG. 6 is a voltage vector diagram of an alternating current applied between electrodes of the device.

FIG. 7 is a combined vector diagram of alternating currents applied between electrodes of the device.

FIG. 8 is an explanatory view of a discharge path of arc discharge generated by the device.

FIG. 9 is an explanatory view of a discharge path of an arc discharge generated in the device.

FIG. 10 is a partial perspective view illustrating a configuration of a discharge electrode of a three-phase AC four-electrode arc discharge device according to a second embodiment of the present invention.

FIG. 11 is a composite vector diagram of alternating current applied between electrodes of arc discharge by three-phase alternating current three electrodes.

[Explanation of symbols]

T _{1 to} T ₁₂ Discharge electrode T ₀ Ground electrode S Multi-phase AC output device H Electrode holder

Claims (3)

[Claims] 1. An arc discharge device in which a multi-phase alternating current of at least 7 phases is applied to the same number of discharge electrodes as the number of phases, the discharge electrodes having a regular polygonal shape at their tips. A multi-phase AC multi-electrode arc discharge device, characterized in that the multi-phase AC is applied to the discharge electrodes in the order of their phases in a clockwise or counterclockwise order. 2. An arc discharge device in which four-phase or five-phase alternating current is applied to the same number of discharge electrodes as the number of phases, and the discharge electrodes are arranged so that their tips form a regular polygon. At the same time, the multi-phase alternating current multi-electrode arc discharge device is characterized in that the multi-phase alternating current is applied to the discharge electrodes in the order of their phases in the right or left direction. 3. An arc discharge device adapted to apply a three-phase alternating current to three discharge electrodes, wherein the discharge electrodes are arranged such that their tips form an equilateral triangle, and the center of the equilateral triangle. A multi-phase AC multi-electrode arc discharge device characterized in that a ground electrode is provided nearby.