JP3241034U - power resistor - Google Patents

Abstract

An object of the present invention is to provide a power resistor that exhibits excellent insulating properties while suppressing peeling of an insulating layer provided on the surface thereof, and that can be manufactured with high productivity.
A resistor substrate (2) and an insulating layer (3) having a thickness of 30 to 200 μm provided on at least part of the surface of the resistor substrate (2), wherein the insulating layer contains zero silicon dioxide. An electric power resistor 1 comprising an alumina cement concretion of 5% by mass or less, wherein the alumina cement concretion is an alumina cement aqueous solution baked at 120 ° C to 250 ° C, and an electric power It is preferred that the resistor for power has a hollow disc shape or that the resistor for power is a resistor for _SF6 gas atmosphere.
[Selection drawing] Fig. 1

Description

The present invention relates to power resistors.

Conventionally, various resistors have been used for current control of circuit breakers, etc., for various controls associated with starting and regenerating electric motors, and for grounding when an abnormality occurs in a power transmission system. , which uses a ceramic resistor as a power resistor.

For example, a carbon particle-dispersed ceramic resistor described in Patent Document 1 (Japanese Patent Application Laid-Open No. 58-139401) has been proposed as a power resistor constituting a resistor used in a high-voltage circuit breaker.
The power resistor is produced by mixing aluminum oxide powder, which is an insulating component, with carbon powder, which is a conductive component, and further mixing clay, which is a binder, and baking the mixture. is said to have a resistivity of
It is said that the carbon particle dispersion type ceramic resistor described above can exhibit an arbitrary resistivity by adjusting the amount of carbon powder added.

As such a carbon particle-dispersed ceramic resistor, one containing aluminosilicate as a main component and carbon as a conductive material is also known, and this resistor has a higher withstand voltage than other resistors. known to have sex.

JP-A-58-139401

By the way, when disconnecting or connecting a high-voltage power system at a substation, power plant, power receiving equipment, etc., if the circuit connection point (switch) is turned off while the high voltage is applied, an arc is generated and the electrical is cut off. It is known that it cannot be done, and in order to load the above-mentioned high voltage, a power resistor that constitutes a resistor has been required to have excellent voltage resistance and insulation.

Therefore, the present inventors came up with the idea of forming an insulating layer on the outer surface of a resistor, which is a base material, to provide a power resistor with excellent insulation.
As the constituent material of the insulating layer, it is preferable to use a material that is excellent in voltage resistance and heat resistance and has a coefficient of thermal expansion comparable to that of the constituent material of the resistor as a base material.
For this reason, it has been considered to employ an insulating layer containing silicon dioxide (SiO ₂ ) (generally contained in a ceramic resistor serving as a base) as a resistor serving as a base.

However, as a result of studies by the inventors of the present invention, when an insulating layer containing silicon dioxide is used, the voltage resistance of the insulating layer decreases according to the content of silicon dioxide in the insulating layer. It turned out to be.

In addition, when used in an environment where the high voltage is applied, generally, the resistor is placed in a tank containing a gas such as SF ₆ (sulfur hexafluoride) gas, which has high insulating properties, at a constant pressure. Gas insulated switchgear (GIS) is coming into use.

In this case, if a resistor having an insulating layer containing silicon dioxide is used as a resistor for electric power, as shown in the chemical formula below, SF4, which is a discharge decomposition product of _SF6 gas, and _SF4 in the insulating layer It was found that the insulating layer deteriorated and peeled off due to reaction with silicon dioxide (SiO ₂ ).
SF ₆ →SF ₄ +F ₂ (discharge decomposition of SF ₆ gas)
SiO ₂ +SF ₄ →SiO ₄ +SO ₂

On the other hand, when a material obtained by baking a material containing aluminum oxide and aluminum phosphate as main components, for example, is used as the insulating layer provided on the surface of the power resistor, the insulating layer is sufficiently solidified to suppress peeling. Although the baking temperature must be 300° C. or higher, if the baking temperature is 300° C. or higher, the resistance value of the power resistor may change (for unknown reasons). It has been found that the yield of the resulting power resistors is low.
Since the baking at 300° C. or higher also causes an increase in energy cost, a method for easily forming an insulating layer at a low temperature of less than 300° C. has been desired.

Under such circumstances, the present invention is a power resistor that can exhibit excellent voltage resistance and insulation while suppressing peeling of the insulating layer provided on the surface, and can be manufactured under high productivity. It is intended to provide

As a result of extensive studies by the inventors of the present invention, it has been found that a resistor base material and an insulating layer having a thickness of 30 to 200 μm provided on at least a part of the surface of the resistor base material, and the insulating layer is , found that the above object can be achieved by a power resistor made of agglomerate of alumina cement having a silicon dioxide content of 0.5% by mass or less, and based on this finding, the present invention was completed. It is a thing.

That is, the present invention
(1) having a resistor base material and an insulating layer having a thickness of 30 to 200 μm provided on at least part of the surface of the resistor base material;
A power resistor, wherein the insulating layer is made of a precipitate of alumina cement having a silicon dioxide content of 0.5% by mass or less;
(2) The power resistor according to (1) above, wherein the aggregate of alumina cement is an alumina cement aqueous solution baked at 120° C. to 250° C.
(3) The power resistor according to (1) above, wherein the power resistor has a hollow disk shape;
(4) A power resistor according to any one of (1) to (3) above, wherein the power resistor is a resistor for SF ₆ gas atmosphere.

According to the present invention, it is possible to provide a power resistor that can exhibit excellent voltage resistance and insulation while suppressing peeling of the insulating layer provided on the surface, and that can be manufactured under high productivity. can.

BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic which shows one form example of the resistor for electric power which concerns on this invention. It is a figure for demonstrating the measuring method of the thickness of an insulating layer in the resistor for electric power which concerns on this invention. It is a schematic sectional drawing which shows the example of the usage form of the resistor for electric power which concerns on this invention. 1 is a schematic diagram showing an example of a method of manufacturing a power resistor according to the present invention; FIG. It is a figure which shows the microscope photograph when the partial cross section of the resistor for electric power obtained in the Example of this application is observed with a scanning electron microscope.

The power resistor according to the present invention is
Having a resistor base material and an insulating layer having a thickness of 30 to 200 μm provided on at least part of the surface of the resistor base material,
The insulating layer is characterized by being made of agglomerate of alumina cement having a silicon dioxide content of 0.5% by mass or less.

A power resistor according to the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic diagram showing one embodiment of a power resistor according to the present invention.
A power resistor 1 illustrated in FIG. 1 has an insulating layer 3 on the outer peripheral surface and the inner peripheral surface of a resistor base material 2 having a substantially hollow disk shape (donut shape or washer shape).

The power resistor illustrated in FIG. 1 has a generally hollow disk shape, but the power resistor of the present invention may have any shape other than the above shape depending on the shape of the resistor to be arranged. can be taken.

In the power resistor according to the present invention, the resistor substrate is preferably made of a ceramic resistor, and more preferably made of a carbon particle-dispersed ceramic resistor.
Examples of carbon particle dispersed ceramic resistors include those containing aluminum oxide as a main component and conductive components such as carbon and clay as binders, and those containing aluminosilicate as a main component and conductive components such as carbon and clay. and the like.
In the present application documents, "containing as a main component" means containing 50 to 73% by mass.

In the power resistor according to the present invention, the resistor base has a shape corresponding to the power resistor, and can take various forms such as a substantially hollow disc shape, depending on the shape of the power resistor. can.

In the power resistor according to the present invention, when the resistor base material has a hollow disk shape as shown in FIG. good.

A power resistor according to the present invention has an insulating layer on at least part of the surface of a resistor substrate.
In the power resistor according to the present invention, the insulating layer may be provided in part or all of the portion where the insulating property of the surface of the resistor substrate is desired to be improved.
For example, as described above, in the power resistor 1 having the form shown in FIG. 1, the insulating layer 3 is provided on the outer peripheral surface and the inner peripheral surface of the resistor base material 2 having a substantially hollow disk shape.

In the power resistor according to the present invention, the thickness of the insulating layer is 30-200 μm, preferably 40-180 μm, more preferably 50-150 μm.
In the power resistor according to the present invention, the thickness of the insulating layer is determined by observing the cross section of the power resistor with a scanning electron microscope (S-3400N manufactured by Hitachi High-Tech Co., Ltd.) with a microscope magnified 200 times. It means the arithmetic mean value of the thickness of the insulating layer at arbitrary 10 locations in the photograph.

FIG. 2 is a diagram for explaining a method of measuring the thickness of the insulating layer in the power resistor according to the present invention.
As shown in FIG. 2, in the power resistor 1 according to the present invention, when the cross section is observed with a scanning electron microscope, the resistor base 2 and the insulating layer 3 are observed. The thickness of the insulating layer 3 can be obtained by measuring the thickness of the insulating layer 3 at arbitrary 10 points in the enlarged micrograph and calculating the arithmetic mean value.

In the power resistor according to the present invention, the thickness of the insulating layer is within the above range, so that excellent insulation can be easily achieved while suitably suppressing peeling from the resistor substrate due to deterioration of the insulating layer. can be demonstrated in

In the power resistor according to the present invention, the insulating layer is made of agglomerates of alumina cement having a silicon dioxide content of 0.5% by mass or less (0.0 to 0.5% by mass).

In the present application, alumina cement means calcium aluminate-based cement containing 30% by weight or more of Al ₂ O ₃ and 50% by weight or less of CaO.

In the power resistor according to the present invention, an insulating layer made of a precipitate of high-purity alumina cement having a silicon dioxide content of 0.5% by mass or less is formed on the surface of the resistor base material. The content of silicon dioxide in the alumina cement is reduced to 0.5% by mass or less, thereby suppressing the deterioration of the withstand voltage of the insulating layer and discharging _SF6 gas It is possible to easily exhibit excellent insulating properties while suppressing deterioration of the insulating layer due to reaction with decomposition products.

In the power resistor according to the present invention, the insulating layer is made of the aluminous cement precipitate, and a specific method of forming the insulating layer on the surface of the resistor substrate will be described later.

In the power resistor according to the present invention, the alumina cement, which is a constituent material of the insulating layer, hydrates and coagulates in the presence of water. An insulating layer can be easily formed by applying it to a portion and drying it.

In the power resistor according to the present invention, the insulating layer may be a dry product at room temperature of an aqueous alumina cement solution applied to the surface of the resistor base material, or an alumina coating applied to the surface of the resistor base material. It may be a baked product of cement aqueous solution at 120°C to 250°C.

In the power resistor according to the present invention, the insulating layer is preferably made of an alumina cement aqueous solution applied to the surface of the resistor substrate and baked at 120 ° C. to 250 ° C., and the insulating layer is baked with the cement aqueous solution. It is possible to provide a power resistor having a stable resistance value and excellent withstand voltage characteristics.

The power resistor according to the present invention is particularly suitable for use as a resistor for _SF6 gas atmosphere.
_SF6 gas atmosphere resistors include resistors for resistors used in _SF6 gas atmospheres, such as gas-insulated neutral-point resistors and resistance injection type gas cut-off resistors used in _SF6 gas atmospheres, respectively. and resistors used in gas disconnectors of the type gas disconnector or the like.

Next, a method of manufacturing a power resistor according to the present invention will be described.
In the power resistor according to the present invention, an aqueous solution of alumina cement having a silicon dioxide content of 0.5% by mass or less is applied to at least a part of the surface of the resistor base material, and then the alumina cement is set. can be produced by forming an insulating layer by

Examples of the resistor base material include those described in the above description, and examples of the alumina cement include those described in the above description.

When alumina cement comes into contact with water, it initiates a hydration reaction and hardens to form a hardened product.
Therefore, by applying an aqueous solution of alumina cement to a desired position on the surface of the resistor base material, a hydration reaction is initiated at room temperature, and the alumina cement is condensed into a hardened material, thereby forming a hardened product. An insulating layer can be formed at a desired position.

The aqueous alumina cement solution may be an aqueous solution containing only alumina cement in water, but since it is a cellulose-based aqueous solution containing cellulose fibers together with alumina cement in water, the fluidity is improved and it can be easily applied. be able to.

Examples of the method of applying the alumina cement aqueous solution to the surface of the resistor substrate include brush coating and spray coating.
The amount of the aqueous alumina cement solution applied to the surface of the resistor substrate may be appropriately determined so as to correspond to the thickness of the insulating layer to be obtained.

As described above, when the alumina cement comes into contact with water, it initiates a hydration reaction at room temperature and condenses into a hardened material. After applying the aqueous solution of alumina cement, the alumina cement may be hydrated and condensed at room temperature to form an insulating layer. After that, the insulating layer may be formed by baking the applied alumina cement aqueous solution at 120°C to 250°C.

The insulating layer of the power resistor according to the present invention is an alumina cement aqueous solution applied to the surface of the power resistor and baked at 120 ° C to 250 ° C, so that it has a constant resistance value. It is possible to manufacture a power resistor with high productivity (a decrease in yield can be suppressed), and to manufacture a power resistor having excellent withstand voltage characteristics under high productivity while achieving energy saving.

FIG. 3 is a schematic cross-sectional view showing an example of application to a gas insulated switchgear (GIS) installed in a power plant or the like, as an example of usage of the power resistor according to the present invention.
In FIG. 3, in a tank T constituting a gas insulated switchgear G, a resistor storing a plurality of power resistors 1 according to the present invention in a stacked state is placed in a breaker portion B, and the tank T The inside is sealed with SF ₆ (sulfur hexafluoride) gas at a constant pressure.
By using the power resistor according to the present invention as the power resistor 1, even when a high voltage is applied to the gas insulated switch G, the surface of the power resistor 1 according to the present invention It is possible to exhibit excellent voltage resistance and insulation while suppressing peeling of the insulating layer provided in the.

According to the present invention, it is possible to provide a power resistor that can exhibit excellent voltage resistance and insulation while suppressing peeling of the insulating layer provided on the surface, and that can be manufactured under high productivity. can.

EXAMPLES The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to the following examples.

<Preparation of resistor base material>
70% by mass of aluminum oxide raw material and 30% by mass of clayey raw material are mixed, and 3% by mass of carbon powder is further added to 100% by mass of the resulting mixture and kneaded. , a hollow disk shape (washer-type shape) having an outer diameter of φ150 mm, an inner diameter of φ35 mm, and a thickness of 25 mm was formed, followed by firing to form the resistor base material 2 .
Next, as shown in FIG. 4B, an electrode film is applied to both the upper and lower planes P, P of the obtained resistor base material by metallikon (thermal spraying) using brass, and the electrode film has a resistance value of 10Ω. A resistor base material was produced.

<Preparation of coating liquid A>
Alumina cement (Denka High Alumina Cement Super manufactured by Denka Co., Ltd., a grade with a silicon dioxide content of 0.1% by mass or less) is 40% by mass, methyl cellulose binder aqueous solution (0.75% by mass of methyl cellulose fiber) % containing) was 60% by mass, and the coating liquid A was prepared by mixing both in a container for 5 minutes.

<Preparation of coating liquid B>
A coating solution B was prepared by mixing 60% by mass of aluminum oxide, 15% by mass of aluminum phosphate, and 25% by mass of water in a vessel for 5 minutes.

<Preparation of coating liquid C>
Denka Alumina Cement No. 1 (manufactured by Denka Co., Ltd., a grade alumina cement with a silicon dioxide content of 4.2% by mass) is 40% by mass, and an aqueous methyl cellulose binder solution (methyl cellulose fiber is 0.75% by mass). A coating solution C was prepared by mixing in a mortar for 5 minutes so that the content of the coating solution was 60% by mass.

(Example 1)
As shown in FIG. 4C, the coating liquid A prepared by the above method was applied to the outer peripheral surface and the inner peripheral surface of the electrode film-attached resistor substrate having a hollow disk shape (washer shape) produced by the above method. On the other hand, the insulating layer was applied by brushing so that the resulting insulating layer had a thickness of about 30 μm to 60 μm, and then allowed to stand at room temperature for 16 hours to condense and harden, thereby forming a coating film.
Next, as shown in FIG. 4(d), the resistor base material having the coating films formed on the outer and inner peripheral surfaces is placed in a heating furnace O and baked at 120° C. in an air atmosphere. , the intended power resistor 1 was obtained.

FIG. 5 is a micrograph (magnified 200 times) of a cross section near the outer periphery of the power resistor 1 obtained in Example 1 observed with a scanning electron microscope. A resistor substrate 2 and an insulating layer 3 are observed on the outer peripheral portion of the resistor 1 .

(Example 2)
In Example 1, except that the coating liquid A was applied by brushing to the outer peripheral surface and the inner peripheral surface of the resistor substrate with the electrode film so that the thickness of the resulting insulating layer was about 170 μm to 190 μm. obtained a power resistor 1 in the same manner as in Example 1.

(Example 3)
A power resistor 1 was obtained in the same manner as in Example 1, except that the baking temperature was changed from 120°C to 250°C.

(Comparative example 1)
A power resistor 1 was obtained in the same manner as in Example 1 except that the coating liquid B was used in place of the coating liquid A and the baking temperature was changed from 120°C to 300°C. .

(Comparative example 2)
In Example 1, the coating liquid A was applied by brushing to the outer peripheral surface and the inner peripheral surface of the resistor substrate so that the thickness of the resulting insulating layer was about 10 μm to 20 μm. A power resistor 1 was obtained in the same manner as in Example 1.

(Comparative Example 3)
In Example 1, except that the coating liquid A was applied by brushing to the outer peripheral surface and the inner peripheral surface of the resistor base material so that the thickness of the resulting insulating layer was about 240 μm to 280 μm. A power resistor 1 was obtained in the same manner as in Example 1.

(Comparative Example 4)
In Example 1, the coating liquid C was used instead of the coating liquid A, and the outer and inner peripheral surfaces of the resistor substrate were brushed so that the resulting insulating layer had a thickness of about 30 μm to 60 μm. A power resistor 1 was obtained in the same manner as in Example 1 except that the coating was applied by coating.

Table 1 shows the production conditions (silicon dioxide content in alumina cement, baking temperature) in each of the above examples and comparative examples.

<Thickness of insulating layer>
The thickness of the insulating layer of the power resistor obtained in each example and comparative example was determined by the method described above.

<Evaluation of peelability of insulating layer>
Table 1 shows the results of measuring the thickness of the insulating layer of the power resistors obtained in each of the above examples and comparative examples and visually confirming the presence or absence of peeling (including cracks) of the insulating layer. .

<Evaluation of withstand voltage of insulating layer>
In the power resistors obtained in the above examples and comparative examples, a lightning impulse voltage generator (type: vertical type) manufactured by Toko Kizai Co., Ltd. was used, and the wave front length (T1) was 1.2 μs and the wave tail length was 1.2 μs. (T2) applied a voltage impulse of 50 .mu.s to carry out a withstand voltage test of the insulating layer.
The generated voltage was gradually increased from 5.0 kV/cm to a maximum of 9.0 kV/cm.
When the generated voltage is less than 9.0 kV/cm and the breakdown or flashover of the resistor occurs (a phenomenon in which the insulating layer cannot withstand the voltage and discharges along the outer surface of the resistor), the generated voltage is reduced to the insulating layer. The maximum withstand voltage was set to 9.0 kV/cm when the breakdown or flashover of the resistor did not occur up to a generated voltage of 9.0 kV/cm.
Table 1 shows the maximum withstand voltage and the presence or absence of flashover.
In the power resistor obtained in Comparative Example 3, peeling of the insulating layer was observed during the withstand voltage evaluation, so the evaluation was interrupted.

<Yield evaluation>
100 power resistors were manufactured by the methods described in the above examples and comparative examples.
In each power resistor obtained, the resistance standard value of 10 ± 0.5 Ω is deviated, or the insulation layer peels (including cracks) when the insulation peeling evaluation is performed by the above method. The number of rejected products was defined as the total number of rejected products. Next, the number of acceptable products in each example and comparative example was obtained from the following formula, and then each yield (%) was calculated.
Number of acceptable products = 100 - Number of rejected products Yield (%) = (Number of accepted products/100) x 100
Table 1 shows the results.
Note that the yield of the power resistor obtained in Comparative Example 3 was not evaluated (because it is clear that the yield is almost 0%).

From Table 1, in Examples 1 to 3, a resistor base and an insulating layer having a thickness of 30 to 200 μm provided on at least a part of the surface of the resistor base, and the insulation Since the layer is made of agglomerate of alumina cement having a silicon dioxide content of 0.5% by mass or less, the insulation layer provided on the surface is suppressed from peeling, while the maximum withstand voltage is high and flashover does not occur. , a power resistor capable of exhibiting excellent voltage resistance and insulation can be manufactured with high productivity.

On the other hand, from Table 1, in Comparative Example 1, a mixture of aluminum oxide and aluminum phosphate was used instead of alumina cement as the material for forming the insulating layer. In addition, the yield at the time of baking is low, and only power resistors with low productivity can be obtained.

Further, from Table 1, the power resistors obtained in Comparative Examples 2 and 3 have the thickness of the insulating layer provided on the surface of the resistor base material outside the predetermined range. (Comparative Example 2), the insulation layer peeled off (Comparative Example 3).

Furthermore, from Table 1, since the power resistor obtained in Comparative Example 4 uses alumina cement containing a predetermined amount or more of silicon dioxide as a material for forming the insulating layer, a withstand voltage evaluation was performed. Occasionally, flashover occurs and the maximum withstand voltage is found to be low.

According to the present invention, it is possible to provide a power resistor that can exhibit excellent voltage resistance and insulation while suppressing peeling of the insulating layer provided on the surface, and that can be manufactured under high productivity. can.

1 power resistor 2 resistor base 3 insulating layer

Claims (4)

Having a resistor base material and an insulating layer having a thickness of 30 to 200 μm provided on at least part of the surface of the resistor base material,
A power resistor, wherein the insulating layer is made of a precipitate of alumina cement having a silicon dioxide content of 0.5% by mass or less. 2. A power resistor according to claim 1, wherein said alumina cement condensate is an alumina cement aqueous solution baked at 120.degree. C. to 250.degree. 2. The power resistor of claim 1, wherein said power resistor has a hollow disk shape. The power resistor according to any one of claims 1 to 3, wherein the power resistor is a resistor for SF ₆ gas atmosphere.

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