JP3486064B2 - Power resistor and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power resistor suitable for absorbing an excessive amount of electric energy, and more particularly, to a power resistor used at a high temperature in an atmosphere containing oxygen, for example, for ground fault current suppression. The present invention relates to a power resistor preferable for a neutral grounding resistor and the like and a method for manufacturing the same.

[0002]

2. Description of the Related Art At present, various electric power resistors are used for controlling currents such as circuit breakers, various controls for starting and regenerating electric motors, and for grounding when an abnormality occurs in a power transmission system. . These resistors are composed of metal resistors, ceramic resistors, and composites of these.

For example, a closing resistor is connected to a high voltage circuit breaker in parallel with a breaking contact in order to absorb a switching surge generated at the time of switching and increase a breaking capacity. As a conventional resistor of a resistor used for these purposes, a carbon particle-dispersed ceramic resistor as described, for example, in JP-A-58-139401 is used. This resistor is made by mixing aluminum oxide powder, which is an insulating component, and carbon powder, which is a conductive component, and baking it with clay that is a binder, and is 100 to 2500 Ω · c.
It has a resistivity of m.

In addition to the carbon particle dispersed type ceramic resistor, the neutral point grounding resistor used for suppressing the ground fault current is, for example, as described in JP-A-7-161505. A linear resistor having zinc oxide as a main component and aluminum oxide and magnesium oxide as a subcomponent is used.

Among them, the carbon particle-dispersed ceramic resistor has an advantage that a resistor having an arbitrary resistivity can be obtained by adjusting the amount of carbon powder added.
However, since the porosity is as high as 10 to 30% and the denseness is poor, there are the following problems. First, since the heat capacity per volume is as small as about 2 J / cm ³ · K, the amount of energy that can be absorbed is small. As a result, the absorption of electric energy causes a remarkable temperature rise. Second,
When a high voltage is applied, a discharge occurs between the carbon powders, and in a remarkable case, a through discharge occurs. Third, since the porosity is high, the mechanical strength is low (4 point bending average strength is 20
(MPa), voicing due to the internal resistance distribution of the resistor causes thermal shock breakdown due to the heat generation distribution. Furthermore, in the atmosphere, 3
If the temperature is higher than 00 ° C., the carbon particles inside the sintered body whose resistance value is controlled are oxidized through the open pores, the resistance value increases, and the function as a resistor is lost. Due to the above problems, a resistor for electric power is disclosed in Japanese Patent Laid-Open No. 58-1394.
The conventional resistor described in Japanese Patent Publication No. 01 has many problems.

The resistor containing zinc oxide as a main component is
There are often non-linearities in the current-voltage characteristics. Therefore, when used with a large current, there is a problem that the resistance value becomes small and the resistor does not function sufficiently. Further, although the mechanical strength is larger than that of the carbon particle-dispersed ceramic resistor, the four-point bending average strength thereof is as small as about 100 MPa and the thermal shock resistance is poor.

In order to solve such a problem, the present inventors have proposed a new power resistor (Japanese Patent Laid-Open No. 8-4570).
2). This is because the porosity of 1 is obtained by using aluminum oxide powder having a small average particle diameter of 0.2 μm as the raw material powder.
A dense sintered body of 0% or less is obtained. as a result,
The heat capacity per volume is 1.5 times as high as that of the resistor described in JP-A-58-139401 and the mechanical strength is 300 MPa or more. The current-voltage characteristics are shown.

[0008]

However, JP-A-8-4
The resistor described in Japanese Patent No. 5702 is also disclosed in JP-A-58-1.
As with the resistor described in Japanese Patent No. 39401, carbon particles in the sintered body conduct electricity. The internal carbon particles are not oxidized because they are not open pores, but there is a problem that when the temperature in the air becomes high, they are oxidized from the surface of the sintered body and the resistance becomes high. Therefore, the amount of energy that can be absorbed is limited by the oxidation resistance temperature.

An object of the present invention is to provide a resistor having a stable resistance value even in an oxidizing atmosphere at high temperature.

In the resistor using the aluminum oxide-based sintered body having carbon as a conductive phase, as described above, when the temperature in the oxidizing atmosphere becomes high, the carbon in the sintered body is oxidized and disappears, resulting in a resistance value. It will change. In the case of a dense sintered body, oxygen cannot pass through pores in order to reach the inside of the sintered body, so that the inside of the sintered body and the grain boundaries must be diffused. Therefore, as compared with the porous carbon particle-dispersed ceramic, although it has excellent oxidation resistance, it is also oxidized from the upper and lower end surfaces and side surfaces on which the electrodes are formed,
It will increase the resistance. In particular, when the resistance of the sintered body is increased by oxidation from the upper and lower surfaces, a resistance-increased portion is generated in the series direction with respect to the energization direction, so that the resistance value of the resistor body is significantly increased.

[0011]

Therefore, in the present invention, the oxidation resistance is improved by shielding the sintered body from the oxidizing atmosphere. That is, the side shield can be prevented by covering with a dense glass material such as borosilicate glass, which has excellent heat resistance and insulation properties. In order to shield the electrode surface, a method having conductivity and excellent airtightness is required. FIG. 3 shows a photograph of a cross section of an electrode formed by the conventional thermal spraying method. As you can see from the figure,
Poor shielding due to its porous nature. Therefore, as a result of examining various electrode forming methods, the present inventors have found that a method of joining a metal plate and a sintered body using an active metal brazing material is extremely excellent. In order to investigate the airtightness, a metal plate 6 was bonded to a cylindrical sintered body 5 using an active metal brazing material as shown in FIG. When the inside was evacuated, the pressure could be evacuated to 10 ^-4 Pa or less, and thus it was confirmed that the gas-tightness was sufficient, and it was confirmed that it was effective for the oxidation resistance property from the electrode surface.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram showing a power resistor according to an embodiment of the present invention. The resistor 1 is a disc-shaped sintered body 2 mainly containing aluminum oxide and containing a carbon component,
A pair of electrodes 3 formed on both end surfaces (only the upper surface is shown)
Is equipped with. Further, an insulating layer 4 is formed on the side surface of the resistor.

The sintered body 2 has a composition containing aluminum oxide and carbon, and comprises a first region having a small amount of carbon or no carbon, and a second region having a larger amount of carbon than the first region. . The first region is substantially insulative and the second region is electrically conductive. The second regions of the sintered body 2 are connected to each other by a three-dimensional network structure and are arranged so as to be connected to the electrodes 3. The resistance value of the sintered body 5 is controlled by the connection state and the resistivity of the second region.

The second region has a form in which electrically conductive carbon is present at the grain boundaries of the insulating aluminum oxide particles, and further, the plurality of second regions are mutually connected by carbon. In the second region, the resistivity can be controlled by the carbon content. In the case of obtaining a sintered body having a relatively high resistivity, it becomes possible by increasing the resistivity of the second region and appropriately increasing the second region. Since the number of connections in the second region is not reduced, the adverse effect on the uniformity inside the sintered body due to the sintering atmosphere, temperature distribution, etc. during manufacturing can be relatively reduced, and the manufacturing yield can be improved.

In the present invention, the carbon average particle is 1 μm.
The reason for setting m or less is that if 1 μm is exceeded, a dense sintered body cannot be obtained.
The reason why the content is set to wt% is that if it is less than 0.05 wt%, sufficient conductivity cannot be obtained, and if it exceeds 3 wt%, a dense sintered body cannot be obtained. Furthermore, the porosity of the insulator layer is 1
The reason for setting the content to 0% or less is that if it exceeds 10%, the sintered body is exposed to an oxidizing atmosphere through the insulating layer, and the sintered body is oxidized from the side surface to have high resistance.

Furthermore, 0.01 to 20% by weight of titanium is used.
The reason is that if it is less than 0.01% by weight, sufficient bonding strength cannot be obtained, and if it exceeds 20% by weight, a fragile compound layer is formed in the bonding layer, and again sufficient bonding strength is obtained. Because there is no.

The structure of the electrode portion of the present invention is shown in FIG. The electrode 3 is composed of an electrode plate 7 and a bonding layer 8 formed by melting and solidifying an active metal brazing material, and the electrode plate 7 and the sintered body 2 are bonded by the bonding layer 8.

As the material of the insulating layer 4, there are an organic material and an inorganic material, but the inorganic material is preferable from the viewpoint of heat resistance. Further, it is preferable that the coefficient of thermal expansion is similar to that of the sintered body 2. If there is a large difference between the two, a crack occurs at the contact interface between the insulating layer and the sintered body, and the insulating layer peels off. Further, in order to obtain a sufficient shielding effect, it is necessary to form a dense layer having a porosity of 10% or less. Due to the above restrictions, the insulating layer 4 contains a glass material such as borosilicate glass or lead glass, aluminum oxide, and / or an inorganic coating material containing silicon oxide as a main component, such as aluminum oxide and aluminum phosphate as main components. The coating material is optimal.

The above material is applied with a brush to form a film by a method such as spray coating or dip coating, and then heat-treated at a temperature suitable for the material to form a side insulating layer. The thickness of the side surface insulating layer depends on the shape of the resistor and the current and voltage used, but when used as a power resistor, it is preferably 100 μm or more.

The metal used for the electrode plate 8 has a coefficient of thermal expansion close to that of the sintered body 2 and does not easily form an oxide film even when exposed to a high temperature oxidizing atmosphere, such as nickel and nickel as main components. And a Kovar alloy are preferable.

As the active metal brazing material for forming the bonding layer 8, one having a composition of 60 to 80% by weight of silver, 20 to 40% by weight of copper, and 0.05 to 10% by weight of titanium is used. It is preferable. In order to strengthen the bonding strength, it is more preferable that the composition of titanium is 0.5 to 4% by weight. As the brazing material, it is convenient to use an alloy foil having the above composition in advance, but the powder may be made into a paste using a suitable solvent, and may be applied or spray coated with a brush . By placing a metal plate on the brazing material and heat-treating it in vacuum, the metal plate 7 and the sintered body 2 are brought into close contact with each other and joined.

The boundary between the insulating layer 4 and the electrode 3 is shown in FIG.
In addition to contacting as shown in, as shown in Figure 6,
The electrode 3 may be on the insulating layer 4, or the insulating layer 4 may be on the electrode 3 as shown in FIG. 7 . However, if there is a gap between the two, the sintered body 2 is oxidized from this portion, which is not preferable.

In addition, the resistor of the present invention is used as a gas circuit breaker (GC
When applied to a closing resistor for B), it is as shown in FIG. 8, and when the resistor of the present invention is applied to a transformer gas-insulated neutral point grounding resistor (NGR), it is as shown in FIG. . 8 and 9, 9 is a circuit breaker, 10 is an arc extinguishing chamber,
Reference numeral 11 is a main contact, 12 is an insulating operation rod, 13 is a closing resistance unit, 14 is a closing resistance contact, 15 is a bushing,
16 is a tank, 17 is a ground wire, and 18 is a connection terminal.

[0025]

【Example】

(Example 1) The power resistor of the present invention was manufactured as follows.

5 wt% of paraffin as a solid component was added as a molding binder to aluminum oxide powder having an average particle size of 0.2 μm in a solid content of 5 wt% to form a slurry using xylene as a solvent, followed by drying to obtain a first granulated powder. In addition, starting from the same aluminum oxide powder as that used for the first granulated powder, 3 w of carbon powder having an average particle size of 50 nm is used.
t%, ethanol was used as a solvent, and the mixture was mixed using an alumina pot and an alumina ball and crushed. After drying, 5% by weight of Palatine as a solid component was added as a binder for molding to prepare the first mixture. The second granulated powder was obtained in the same manner as the granulated powder, and the first granulated powder was V at a ratio of 75 wt% and the second granulated powder was at a ratio of 25 wt%.
The mixture was mixed by a mold mixer to obtain a mixed granulated powder.

These mixed granulated powders were used in a steel mold and a molding pressure of 500 kg / cm ² and a diameter of 12.5 c.
m to form a disc having a thickness of 3.1 cm to obtain a molded body. The boundary between the upper and lower circular surfaces and the outer peripheral surface of this molded body was chamfered by 1 mm, and then debindered by holding it in nitrogen gas at 600 ° C. for 4 hours. Next, this degreased body
Temperature rise at 200 ° C / hour in an argon gas atmosphere, 150
By holding at 0 ° C. for 1 hour, a sintered body having a diameter of 10 cm and a thickness of 2.5 cm was obtained.

Both upper and lower end surfaces of this sintered body were ground with a No. 400 grindstone. Next, Ni with a diameter of 10 cm and a thickness of 500 μm is used.
Plate, diameter 10 cm, thickness 50 μm, composition, silver 70.6% by weight, copper 27.4% by weight, titanium 2.0% by weight, Ti
-Ag-Cu alloy brazing filler metal foil, a sintered body, a brazing filler metal foil, a Ni plate are stacked in this order, a metal tungsten weight having a side of 10 cm and a weight of 500 g is placed thereon, and the weight is held at 830 ° C. for 10 minutes in a vacuum. The metal plate and the sintered body were joined together to form an electrode.

Further, a water-soluble paste composed of aluminum phosphate, alumina fine powder, and silica fine powder was brush-painted on the circumferential surface of this sintered body and dried at 150 ° C. for 1 hour to form an insulating layer on the outer surface excluding the electrode end. Then, the power resistor of Example 1 was obtained. The resistance value of this resistor was 60Ω.

As a result of measuring the resistance at the electrode portion of this resistor, it was as low as 10 ^-6 Ω or less, and there was no electrical problem. The oxidation resistance of this resistor is shown in FIG.
It was left in the air at a temperature of 1000 ° C. for 2 hours.
As a result, up to 650 ° C, no change in the resistance value was observed before the oxidation. (Example 2) A sintered body having a diameter of 10 cm and a thickness of 2.5 cm was obtained in the same manner as in Example 1, and an electrode was formed in the same manner as in Example 1. Next, borosilicate glass powder is dispersed in an organic solvent, spray-coated on the outer and inner surfaces of the sintered body, heat-treated at 300 ° C. for 1 hour and baked, and the outer surface excluding the electrode ends is sprayed. An insulating layer was formed to obtain a power resistor of Example 2. As a result of carrying out the same oxidation resistance test as in Example 1 on this resistor, the oxidation resistance temperature is the same as in Example 1 650.
It was ℃. (Example 3) Instead of the Ni plate used in Example 1, a Kovar alloy having a thickness of 0.5 mm was used as an electrode plate, and the electrodes were formed by bonding in the same manner as in Example 1, and then, as in Example 1. An insulating layer was formed on the side surface to obtain a resistor in Example 3. The oxidation resistance temperature was 650 ° C. (Comparative Example) A sintered body having a diameter of 10 cm and a thickness of 2.5 cm was obtained in the same manner as in Example 1. After grinding the upper and lower end surfaces of this sintered body, aluminum electrodes were formed by a thermal spraying method. Next, a water-soluble paste consisting of aluminum phosphate, alumina fine powder, and silica fine powder was brush-painted on the outer surface and inner surface of the sintered body, and dried at 150 ° C for 1 hour to form an insulating layer on the outer surface excluding the electrode end. Then, a resistor of Comparative Example was obtained. The resistance value of this resistor was 60Ω, which was the same as that of the resistor of Example 1.
As a result of performing an oxidation resistance test on this resistor in the same manner as in Example 1, as shown in FIG. 2, an increase in resistance was observed from 450 ° C. It became an insulator at 500 ° C or higher. (Conventional example) Outer diameter 127 mm, inner diameter 41 mm, thickness 25 m
As a result of conducting an oxidation resistance test on the carbon particle-dispersed ceramic conventional resistor having a hollow cylindrical shape of m by the same method as in Example 1, as shown in FIG. Admitted. It became an insulator at 400 ° C or higher.

[0031]

As described above, according to the present invention, it becomes possible to improve the oxidation resistance of the resistor by shielding the sintered body from the oxidizing atmosphere with the insulating layer and the electrode. For this reason, compared to the conventional resistors, it is possible to use up to a higher temperature, so that it is possible to absorb a larger electric energy per unit volume. As a result, it was very effective in reducing the size of power equipment.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining an embodiment of the present invention.

FIG. 2 is a diagram showing oxidation resistance characteristics of three types of power resistors of Example 1 of the present invention.

FIG. 3 is a micrograph showing a cross section of an electrode formed by a thermal spraying method according to the present invention.

FIG. 4 is a view in which a metal plate is joined to the cylindrical sintered body of the present invention by using an active metal brazing material.

FIG. 5 is a configuration diagram showing an electrode portion according to the embodiment of the present invention.

FIG. 6 is a diagram showing a modified example of FIG.

FIG. 7 is a diagram showing a modification of FIG.

FIG. 8 is a view for explaining the internal structure of the circuit breaker when the resistor of the present invention is applied to a closing resistor for a gas circuit breaker (GCB).

FIG. 9 is a diagram for explaining the internal structure of the neutral point grounding resistor when the resistor of the present invention is applied to a gas-insulated neutral point grounding resistor (NGR) for a transformer.

[Explanation of symbols]

1 ... Power resistor 2 ... Sintered body 3 ... Electrode 4 ... Insulating layer 5 ... Metal plate 6 ... Sintered body 7 ... Metal plate 8 ... Bonding layer 9 ... Circuit breaker 10 ... Arc extinguishing quality 11 ... Main contact 12 ... Insulated operating rod 13 ... closing resistance unit 15 ... Bushing 16 ... Tank 17 ... Ground wire 18 ... Connection terminal

Continuation of the front page (56) Reference JP-A-8-45702 (JP, A) JP-A-8-17604 (JP, A) JP-A-6-45108 (JP, A) JP-A-5-13203 (JP , A) JP 5-13202 (JP, A) JP 57-52101 (JP, A) JP 60-76103 (JP, A) JP 58-139401 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01C 7/00 H01C 13/00 H01C 17/00

Claims (7)

(57) [Claims] 1. 0.05 to 3% by weight of carbon particles having a metal oxide as a main component and an average particle diameter of 1 μm or less as a subcomponent.
For electric power, which includes a sintered body containing the sintered body, at least one pair of electrodes formed on both end surfaces of the sintered body, and an insulating layer formed on the outer surface of the sintered body except the electrode forming surface. In the resistor, the electrode is a metal plate mainly composed of silver and copper and bonded with an active metal solder containing titanium, and the porosity of the insulating layer is 1
Or less 0%, further, the sintered body of the electrode and the external surface faces the power resistor boundary portion above is characterized in that it is covered by the <br/> insulating layer. 2. A power resistor, wherein the metal oxide according to claim 1 is aluminum oxide or a composite oxide containing aluminum. 3. The sintered body according to claim 1, wherein a first region having a low carbon content or no carbon content and a carbon content higher than the first region are connected to a pair of electrodes. A power resistor having a second region disposed in. 4. A power resistor, wherein the joint structure of the active metal brazing material according to claim 1 after solidification contains 0.01 to 20% by weight of titanium. 5. A power resistor, wherein the insulating layer according to claim 1 is made of an inorganic material containing aluminum oxide and / or silicon oxide as a main component. 6. A power resistor, wherein the insulating layer according to claim 1 is made of borosilicate glass. 7. 0.05 to 3% by weight of carbon particles having a metal oxide as a main component and an average particle diameter of 1 μm or less as a subcomponent.
For electric power, which includes a sintered body containing the sintered body, at least one pair of electrodes formed on both end surfaces of the sintered body, and an insulating layer formed on the outer surface of the sintered body except the electrode forming surface. in the resistor, the electrode is a metal plate, silver, copper as a main component, is formed by joining an active metal braze comprising titanium, pre Symbol sintered electrode and external surface surface of the boundary portion on method of manufacturing the power resistor according to claim Rukoto covered with the insulating layer.