JPH1036168A - Production of ceramic linear resistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a ceramic linear resistor aiming at a highly withstanding property by blending specific four components and burning the mixture, and a breaker stably functioning up to a high temperature by using the highly withstanding ceramic linear resistor. SOLUTION: This ceramic linear resistor is obtained by blending 68-90mol% Zn based on ZnO, 5-20mol% Al based on Al2 O3 , 3-10mol% Mg based on MgO and >=1mol% at least one of ZnAl2 O4 and MgAl2 O4 , and sintering the mixture. A resistor element 1 obtained by inserting an insulating rod 2 into an insulating tube 3, is housed in a resistor unit 4 of a breaker shown in the figure, and a bushing 10 for protecting an electric circuit is installed therein. By air from an air tank 9, a piston 7 for opening and closing operations is actuated, main contact points 6a, 6b for turning on electricity are opened for applying the electricity to the resistor unit 4 connected in parallel, and rear resisting contact points 5a, 5b are opened to complete a breaking function. A turning on function is to close the resistor contacting points 5a, 5b by the piston 7 for the opening and closing operations, turn on the electricity to the resistor unit 4 and close the main contacting points 6a, 6b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a ceramic linear resistor suitable for a breaking / closing resistance of a UHV power transmission circuit breaker.

[0002]

2. Description of the Related Art Characteristics desired for a linear resistor used in a UHV power transmission circuit breaker or the like are that the voltage-current characteristics are ohmic, that the resistivity is several hundred to 1,000 Ωcm, and that the temperature coefficient of resistance is zero. Or, it is positive and has a large energy resistance. As a resistor having the above characteristics at a practical level, for example, Japanese Patent Application Laid-Open No.
No. 4206, C-Al ₂ O ₃ -based resistor, and JP-A 63-55904, ZnO-Al ₂ O ₃ -M
gO-based resistors and the like. The resistance value of the C-Al ₂ O ₃ -based resistor is adjusted by the amount of carbon dispersed as conductive particles in the oxide insulating system and the degree of contact. Also, ZnO-Al
_{A 2} O ₃ —MgO-based resistor basically includes ZnO crystal grains and ZnO
It consists of spinel crystal grains of Al ₂ O ₄ and MgAl ₂ O ₄ , and its resistance value is adjusted by the volume ratio of these crystal grains and the characteristics of the grain boundaries.

[0003]

The C-Al ₂ O ₃ -based resistor has a small temperature coefficient of resistance, but has a risk of causing thermal runaway when energized, and has a small heat capacity and a low energy resistance. . Z developed to solve this point
The nO—Al ₂ O ₃ —MgO-based resistor includes ZnO, Al
With ₂ O _3, MgO as a raw material, mixing, molding, are produced through calcination, this method may not be uniform mixing of raw materials, and material diffusion during sintering or not sufficient,
Solid solution reaction of raw material powder Al ₂ O ₃ into ZnO and ZnAl ₂ O ₄
However, it is not completely consumed by the synthesis reaction of MgAl ₂ O ₄ , and remains in the sintered body as a small amount but unreacted. Since this Al ₂ O ₃ is insulative and minute, a high-resistance portion is locally formed at the grain boundary to make the current distribution non-uniform at the time of energization, thereby lowering the energy resistance. An object of the present invention is to improve the resistance of a ceramic linear resistor. It is another object of the present invention to provide a circuit breaker that operates stably up to a high temperature by using a ceramic linear resistor having a high resistance.

[0004]

SUMMARY OF THE INVENTION The object of the present invention is to provide Zn
In terms of O and 68 to 90 mol%, 5 to 20 mol% in terms of Al to Al ₂ O _3, in terms of Mg to MgO 3 to 10
It is achieved by mixing and sintering at least 1 mol% of at least one of ZnAl ₂ O ₄ and MgAl ₂ O ₄ . The purpose is to convert Zn to ZnO of 68 to
This is achieved by mixing and sintering 90 mol%, Al in terms of Al ₂ O ₃ , 5 to 20 mol%, and at least one of ZnAl ₂ O ₄ and MgAl ₂ O ₄ at 1 mol% or more. The purpose is to convert Zn to ZnO of 68 to 80.
Mol%, ZnAl ₂ O ₄ and MgAl ₂ O ₄ each 1 mol%
This is achieved by mixing and sintering. The object is to convert Zn to ZnO by 68 to 80 mol%, ZnA
l ₂ O ₄ and MgAl ₂ O ₄ are each 1 mol% or more, and Si is S
by mixing 0.1 to 5 mol% in terms of iO ₂ is achieved by sintering. The object is to convert Zn to ZnO by 68 to 80 mol%, ZnAl ₂ O ₄ and MgAl
₂ O ₄ is 1 mol% or more, and Si is converted to SiO ₂ .
1 to 5 mol%, 1 to 10 mol% in terms of Ca converted to CaO
And sintering. The object is to convert Zn to ZnO by 68 to 80 mol%, ZnA
l ₂ O ₄ and MgAl ₂ O ₄ are each 1 mol% or more, and Si is S
in terms of the iO ₂ and 0.1 to 5 mol%, CaO, SrO,
It is achieved by mixing and sintering 0.5 to 10 mol% of one or more of BaO. It is desirable to manufacture a circuit breaker using the ceramic linear resistor according to the above manufacturing method. According to the above configuration, by using ZnAl ₂ O ₄ and MgAl ₂ O ₄ which are reaction products from the beginning as raw materials, the highly insulating Al ₂ O ₃ remaining in the sintered body is used.
Can be reduced, the current distribution at the time of energization becomes uniform, and the energy resistance is improved. Here, the reason why the composition range of each component is limited will be described. Zn is 68 in terms of ZnO
If it is less than mol%, the temperature coefficient of resistance is small, and if it exceeds 90 mol%, the resistivity becomes too low. If Al is less than 5 mol% in terms of Al ₂ O ₃ , the linearity of the voltage-current characteristics will be poor, and if it exceeds 20 mol%, the resistivity will be too large.
If the total amount of ZnAl ₂ O ₄ and MgAl ₂ O ₄ is less than 1 mol%, the effect of improving the energy resistance cannot be seen. If Mg is less than 3 mol% in terms of MgO, the temperature coefficient of resistance becomes negative and there is a risk of causing thermal runaway. If it exceeds 10 mol%, the resistivity and the temperature coefficient of resistance become too large. Si
If it is less than 0.1 mol% in terms of SiO ₂ , the effect as a sintering aid does not appear, and if it exceeds 5 mol%, the linearity of the voltage-current characteristics deteriorates. With respect to CaO, SrO, and BaO, if it is less than 0.5 mol%, the effect of suppressing the decrease in resistivity under a high electric field is not seen. Also, Zn as a raw material
ZnO-A obtained by using at least one of Al ₂ O ₄ and MgAl ₂ O _{4 in} a total amount of 1 mol% or more
With l ₂ O ₃ -MgO based resistor in closing resistor portion of the gas circuit breaker can provide a large temperature rise may not cause destruction of the resistor reliable circuit breaker.

[0005]

Embodiments of the present invention will be described below. The ceramic linear resistor according to the embodiment of the present invention can be manufactured by a general sintering method. That is,
After mixing a predetermined amount of oxide powder, the mixture is thoroughly mixed and dried using a ball mill or the like. An appropriate binder such as polyvinyl alcohol is added to the mixed powder, granulated, and molded by a mold. The molded body is 1000 to 14 in the atmosphere in an electric furnace.
Firing at 00 ° C, polishing the upper and lower end surfaces of the obtained sintered body,
An electrode is formed by spraying Al, Au, Pt, Pd, or the like.
Here, the shape of the resistor may be a disk shape,
As described in JP-A-63-55904, a structure in which a through-hole is provided at the center may be used.

Hereinafter, the present invention will be described with reference to specific examples. << Example 1 >> ZnO, Al ₂ O ₃ , Mg as starting materials
O, ZnAl ₂ O _4, and MgAl ₂ O ₄ powders were weighed in predetermined amounts to have the compositions shown in Table 1.

[0007]

[Table 1]

These were made into a slurry by mixing zirconia with a cobblestone and using a pure water as a dispersion medium in a ball mill for 15 hours, and then drying the slurry. To the obtained mixed powder, polyvinyl alcohol of 3 wt% concentration of 6 wt% based on the powder was added and kneaded, and the mixture was passed through a 32 mesh sieve to obtain granulated powder. The granulated powder has an outer diameter of 99 at a pressure of 4.5 MPa using a mold.
It was molded into a structure in which a hole was provided in the center of mmφ-inner diameter 40 mmφ × thickness 23 mm, and calcined at 1250 ° C. in the atmosphere for 2 hours. After polishing and washing and drying the upper and lower end surfaces of the obtained sintered body, an Al electrode was formed by thermal spraying to obtain a ceramic linear resistor. In the conventional manufacturing method, in order to efficiently perform a synthesis reaction of ZnAl ₂ O ₄ and MgAl ₂ O ₄ , a small amount of ZnO and other additive components are calcined, and then mixed with the remaining ZnO and calcined. However, in the production method of the present invention, ZnAl ₂ , which is a reaction product from the beginning as a raw material powder, is used.
Since O ₄ and MgAl ₂ O ₄ are used, the calcining step can be omitted, and the manufacturing steps can be shortened and the cost can be reduced. Note that ZnAl ₂ O ₄ and Mg
Although Al ₂ O ₄ is generated, it is difficult to uniformly mix the calcined powder and the rest of ZnO, so it is better to use ZnAl ₂ O ₄ and MgAl ₂ O ₄ which are reaction products from the beginning as a raw material powder. A resistor having high energy resistance can be obtained. Table 1 shows the resistivity and energy tolerance of ceramic linear resistors having different compositions. Energy tolerance is amplitude 4
It was obtained as an implantation energy until a breakthrough occurred when an AC voltage having a kV cycle of 20 ms was applied. Conventional example No.1
And Examples of the present invention Nos. ₃ to 5 show that Al ₂ O ₃ is ZnAl
It can be seen that by replacing with ₂ O ₄ , the energy resistance can be improved without significantly affecting the resistivity. The energy resistance is improved as the amount of Al ₂ O ₃ in the raw material powder is reduced. However, if the amount of ZnAl ₂ O ₄ is less than 1 mol% as in Reference Example No. 2, the effect of improving the energy resistance is not seen. In addition, comparing the conventional example No. 1 and the present invention examples Nos. 7 to 9, it is possible to improve the energy resistance without significantly affecting the resistivity by replacing Al ₂ O ₃ with MgAl ₂ O _4. We can see that we can do it. Also in this case, the energy withstand capability is the same as that of Al ₂ O ₃ in the raw material powder.
The better you reduce, the better. However, like No.6, M
If the amount of gAl ₂ O ₄ is less than 1 mol%, the effect of improving the energy resistance cannot be seen. Further, it can be seen from Examples 11 to 16 of the present invention that when both ZnAl ₂ O ₄ and MgAl ₂ O ₄ are used as the raw materials, the effect of improving the energy withstand capacity is further remarkable.

FIG. 1 is an organization diagram schematically showing a cross section of a ceramic linear resistor according to a manufacturing method of an embodiment of the present invention. If Al ₂ O ₃ does not remain in the sintered body as shown in this figure, the current distribution during energization becomes uniform. However, as in Invention Example No. 16, the spinel crystal phase (ZnAl ₂ O ₄ and M
When gAl ₂ O ₄ ) occupies a large volume ratio, the resistivity increases, so that the energy resistance decreases. When the spinel crystal phase exceeds a certain amount as in No. 17, (ZnAl ₂ O ₄ and MgAl ₂ O ₄ are replaced with ZnO, Al ₂
If Al ₂ O ₃ exceeds 20 mol% when converted to O ₃ or MgO), the resistivity is too large, and the energy resistance is undesirably deteriorated. Also, as in No10, ZnA
If the total amount of l ₂ O ₄ and MgAl ₂ O ₄ is less than 1 mol%, the effect of improving the energy resistance cannot be seen. << Example 2 >> A sample was prepared by adding SiO ₂ to a composition close to No. 15 of Example 1 and evaluated. Table 2 shows the composition and characteristics.

[0010]

[Table 2]

The porosity was determined by observing the fracture surface with a scanning electron microscope and performing image processing. Regarding the linearity of the voltage-current characteristic, when logI = αlog (V / C) (I is current, V is voltage, C is a constant, and α is a non-linear coefficient),
α is desirably 1.3 or less. Then DC 10V
/ Α at 1.5 kV / cm and I / V at 1.5 kV / cm
Within 1.3, a circle was shown, and when larger than 1.3, a cross was shown. No. 18 has improved sinterability compared to Conventional Example No. 1. N
In the case of No. 19, No. 18 was fired by lowering the firing temperature to 1150 ° C., and the porosity was equivalent to that of No. 1. But N
o. Both 18 and 19 have poor energy tolerance. On the other hand, Examples Nos. 20 to 22 of the present invention show a high energy resistance of 700 J / cc or more. Even when SiO ₂ is added, the effectiveness of using ZnAl ₂ O ₄ and MgAl ₂ O ₄ as raw materials is not significant. You can check. In addition, in No. 23, the added amount of SiO ₂ exceeded 5 mol%, and although the energy resistance was high, the linearity was poor.

<< Example 3 >> The composition of No. 20 of Example 2
Samples were prepared by adding aO, SrO, and BaO and evaluated. Table 3 shows the composition and characteristics.

[0013]

[Table 3]

Regarding the linearity of the voltage-current characteristics, in order to examine the change in resistivity under a high electric field, I and V were measured at DC 10 V / cm and 5 kV / cm.
The case of 0% or less was indicated by ○, and the case of larger than 0% was indicated by ×. Invention Example No. Even in a sample to which CaO is added as in Examples 24 to 26, when ZnAl ₂ O ₄ and MgAl ₂ O ₄ are used for the raw material powder, a high energy resistance can be obtained. When the resistivity increases, the energy resistance tends to decrease, but the Zn
Conventional example No. 1 40 without using Al ₂ O ₄ and MgAl ₂ O ₄
Greater than 0J / cc. If CaO is added too much as in No. 27, the linearity will be poor. Invention Examples No. 27 to 30, 32 to
From FIG. 34, it can be seen that the use of ZnAl ₂ O ₄ and MgAl ₂ O ₄ as the raw material powder has an effect of improving the energy withstand even in the sample to which SrO and BaO are added. However, No. 31, 35
If SrO and BaO are added too much, the linearity also deteriorates. Invention Examples Nos. 36, 38, 40, and 42 are CaO, S
Although this is an example in which rO and BaO are added in combination, the effect of improving the energy resistance is seen in any combination. On the other hand, No. 37, 39, 41, and 43 are CaO, S
The sum of rO and BaO exceeds 10 mol%, and both have poor linearity.

<< Example 4 >> A sample having a composition of No. 25 of Example 3 (disc shape having a through hole of 127 mm in outer diameter-33 mm in inner diameter × 25 mm in thickness) by the method of manufacturing a ceramic linear resistor of the present invention. 1650 sheets were manufactured and stacked in 6 parallel, and 1100
It was incorporated in a kV gas circuit breaker. FIG. 2 is a longitudinal sectional view showing the entire configuration of the embodiment of the present invention. As shown in the figure, a resistor unit 4 of a circuit breaker contains a resistor element 1 according to the manufacturing method of the present invention inserted into an insulating rod 2 in an insulating cylinder 3. Reference numeral 10 denotes a bushing for protecting the electric circuit. The breaking operation of the circuit breaker is as follows: 1) Opening / closing operation piston 7 is actuated by air from air tank 9 to open main contacts 6a and 6b which are normally energized, and resistor unit 4 connected in parallel with main contacts 6a and 6b Current flows through 2) Thereafter, the resistance contacts 5a and 5b of the resistance unit 4 are opened by the opening / closing operation piston 7, and the shutoff operation is completed. On the other hand, the closing operation is as follows: 1) The resistance contacts 5a and 5b are closed by the opening / closing operation piston 7, and a current flows through the resistor unit 4. 2) The main contacts 6a and 6b are closed by the opening / closing operation piston 7, and the closing operation is completed. When the main contacts 6a and 6b are opened, an AC discharge current of several tens of milliseconds flows through the resistor unit 4 and absorbs overvoltage. The impact when the operation of the opening / closing operation piston 7 is completed is reduced by the oil dash pot 8. The circuit breaker was subjected to 10 continuous breaking and closing operations. As a result, no abnormalities were found in the resistance characteristics and the circuit breaker both during and after the test, and the energy resistance of the resistor element was high.
It was confirmed that the device operates stably even when the temperature rises.

[0016]

According to the present invention, A remaining in the sintered body
l ₂ O ₃ can be reduced, the current distribution during energization becomes uniform, and the energy resistance of the ceramic
The effect of improving 90% is obtained. Further, it is possible to provide a circuit breaker that operates stably up to a high temperature using the ceramic linear resistor manufactured by the manufacturing method of the present invention.

[Brief description of the drawings]

FIG. 1 is an organization diagram schematically showing a cross section of a ceramic linear resistor according to a manufacturing method of an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing the entire configuration of the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Resistor element 2 Insulating rod 3 Insulating cylinder 4 Resistor unit 5a Resistance contact 5b Resistance contact 6a Main contact 6b Main contact 7 Piston for opening and closing operation 8 Oil dash pot 9 Air tank 10 Bushing

Continued on the front page (72) Inventor Shigeru Tanaka 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi Research Laboratory, Hitachi, Ltd. (72) Kunihiro Maeda 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi Research Laboratory, Hitachi, Ltd.

Claims (8)

[Claims] 1. Zn is converted to ZnO at 68-90 mol%, Al is converted to Al ₂ O ₃ is 5-20 mol%, Mg is converted to MgO is 3-10 mol%, ZnAl ₂ O is used. _A method for producing a ceramic linear resistor, comprising mixing at least one of MgO ₄ and MgAl ₂ O _{4 in} an amount of 1 mol% or more and sintering the mixture. 2. Zn is 68 to 90 mol% in terms of ZnO, Al is 5 to 20 mol% in terms of Al ₂ O ₃ , ZnA
A method of manufacturing a ceramic linear resistor, comprising mixing at least one of l ₂ O ₄ and MgAl ₂ O _{4 in} an amount of 1 mol% or more and sintering the mixture. 3. Manufacture of a ceramic linear resistor characterized in that Zn is converted to ZnO in an amount of 68 to 80 mol%, and ZnAl ₂ O ₄ and MgAl ₂ O ₄ are mixed in an amount of 1 mol% or more and sintered. Method. 4. Zn is converted to ZnO at 68 to 80 mol%, ZnAl ₂ O ₄ and MgAl ₂ O ₄ are each at least 1 mol%, and Si is converted to SiO ₂ at 0.1 to 5 mol%. A method for producing a ceramic linear resistor, comprising mixing and sintering. 5. Zn is converted to ZnO at 68 to 80 mol%, ZnAl ₂ O ₄ and MgAl ₂ O ₄ are each at least 1 mol%, and Si is converted to SiO ₂ at 0.1 to 5 mol%. Ca
Is converted to CaO, and 1 to 10 mol% is mixed and sintered. 6. Zn is converted to ZnO by 68 to 80 mol%, ZnAl ₂ O ₄ and MgAl ₂ O ₄ are respectively 1 mol% or more, and Si is converted to SiO ₂ by 0.1 to 5 mol%. Ca
A method for producing a ceramic linear resistor, characterized in that at least one of O, SrO and BaO is mixed at 0.5 to 10 mol% and sintered. 7. A ceramic linear resistor manufactured by the manufacturing method according to claim 1. Description: 8. A circuit breaker comprising a ceramic linear resistor manufactured by the manufacturing method according to any one of claims 1 to 6.