JPH0696909A - Transformer - Google Patents

Abstract

PURPOSE:To reduce the size of a transformer by providing a neutral grounding resistor using a ceramic liner resistor composed mainly of zinc oxide. CONSTITUTION:This transformer is provided with a neutral grounding resistor using a ceramic linear resistor 5 composed mainly of zinc oxide. In addition, another neutral grounding resistor using the same ceramic linear resistor 5 composed mainly of zinc oxide is incorporated in an insulating gas atmosphere. In addition, a third neutral grounding resistor using the same ceramic linear resistor 5 composed mainly of zinc oxide is installed to the outside of the transformer. The resistor is composed of 70-99.7mol% zinc oxide, 0.1-10mol% magnesium oxide, and 0.1-20mol% of at least one oxide selected from among Al2O3, Y2O2, Ga2O3, La2O3, and In2O3. Therefore a small-sized transformer can be obtained by using a linear resistor having a large switching surge resistance, small voltage nonlinear coefficient, and positive, small, and excellent temperature coefficient of resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a new power transmission and transformation device, and more particularly to a power transmission and transformation device suitable for absorbing switching surges such as circuit breakers.

[0002]

2. Description of the Related Art Conventionally, as a circuit breaker resistor, an aluminum oxide-clay-carbon composition has been known, which has a resistance value of about 400 Ωcm and a circuit breaker withstand switching surge resistance of 500 Joules / cm ³ (hereinafter , J / cm ³ ), a temperature coefficient of resistance of −9 × 10 ³ / ° C. (20 to 250 ° C.) and a maximum operating temperature of 200 ° C.

Recently, there has been a strong demand for downsizing and weight saving of a linear resistor for a circuit breaker along with an increase in transmission voltage. Therefore, as a resistor, (1) increase a switching surge withstand capability. (2) The temperature rises when a switching surge is injected, but the resistance value does not fluctuate even when exposed to high temperatures.
(3) The temperature coefficient of resistance is positive. (4) Materials such as that voltage-current characteristics change linearly are required. The linearity of the voltage-current characteristic here is approximately represented by I (current) = K (constant) × V (voltage) α, and α is desired to be 1.3 or less.

Conventionally, a carbon powder-dispersed ceramic resistor used as a resistor of a circuit breaker is sintered in an inert gas atmosphere to prevent carbon combustion, and the resistance value is a mixed amount of carbon powder. Controlled. This resistor (1) changes its resistance value due to the oxidation of carbon when exposed to a temperature of 400 ° C or higher. (2) The temperature coefficient of resistance is negative and it is -9 × 10 ~ ² / ° C (2
Since it is large (0 to 250 ° C.), the resistance decreases when the temperature rises, and when the voltage is constant, there is a drawback that the temperature suddenly increases and more heat is generated, causing a runaway state.

Therefore, as a resistor, a ceramic resistor using zinc oxide, which is an oxide type which does not cause combustion, as a basic component is known in JP-A-55-57219. The present inventors have found that the conventional oxide resistor mainly composed of zinc oxide does not sufficiently satisfy the required characteristics described above, and arrived at the present invention.

[0006]

The object of the present invention is to have a resistance of 40 to 4000 Ωcm, good linearity of voltage-current characteristics, and large circuit breaker surge withstand capability.
There is little fluctuation in resistance even when exposed to high temperatures of 00 ° C or higher,
Temperature coefficient of resistance is to provide an oxide resistor having a range of + 4 × 10 ~ ³ / ℃ from -1 × 10 ~ ³ / ℃.

[0007]

The present invention comprises zinc oxide as a main component, magnesium oxide of 0.1 to 10 mol%, and at least one of aluminum oxide, gallium oxide, lanthanum oxide and indium oxide in an amount of 0.1 to 0.1 mol%. 20 mol% and the oxide resistor.

Further, the present invention comprises zinc oxide as a main component, magnesium oxide of 0.1 to 10 mol% and at least one of aluminum oxide, gallium oxide, lanthanum oxide and indium oxide of 0.1 to 20 mol%. , 1 to 2 mol% of silicon oxide.

In particular, the molar ratio of zinc oxide is 70 to 92%,
Magnesium oxide 3-10% and aluminum oxide 5-5
Preference is given to oxide resistors having 15%, or oxide resistors having 68-90% zinc oxide, 3-10% magnesium oxide, 5-15% aluminum oxide and 1-2% silicon oxide in molar ratios.

[0010]

[Function] Zinc oxide crystal grains and 100Ω to 4 ×
A composite sintered body with crystal grains showing an electric resistance value of 10 ¹³ Ω,
A grain boundary layer having a lower electric resistance than the zinc oxide grains exists between the zinc oxide grains. This sintered body may be plate-shaped, column-shaped, or cylindrical, and electrodes are formed on both end surfaces. The electrodes are formed on the entire surface with some edges remaining, and a metal such as Al is formed into a film by thermal spraying or the like.

A grain boundary layer having the same electric resistance value as that of the zinc oxide crystal grain may exist between the crystal grains. The crystal grains of oxides excluding zinc oxide compounds and zinc oxide are 100Ω to 4 ×
It is desirable that the resistance is higher than that of zinc oxide in the range of 10 ¹³ Ω. The zinc oxide compound and oxides other than zinc oxide are of the following chemical formulas. That is, the basic component MgO,
In order to further improve the linearity of the voltage-current characteristics, ZnY ₃
O ₄ , ZnGa ₃ O ₄ , ZnLa ₃ O ₄ , ZnAl ₂ O ₄ , Z
nIn ₂ O ₃ , MgAl ₂ O ₄ , MgY ₂ O ₄ , MgGa
₃ O ₄ , MgLa ₃ O ₄ , MgIn ₃ O ₄ , Al ₂ O ₃ , Y
It is to contain at least one selected from ₂ O ₃ , Ga ₂ O ₃ , La ₂ O ₃ and In ₂ O ₃ . In order to form these compounds, a metal or metalloid element such as aluminum (Al), yttrium (Y), gallium (Ga), lanthanum (La) and indium (In) is added to the main components ZnO and MgO. That is. The use of bismuth (Bi) is not desirable. This is because when Bi is used, a high resistance layer is easily formed in the crystal grain boundary phase.

The raw materials for the sintered body are zinc oxide (ZnO) and magnesium oxide (MgO) as basic components, and as auxiliary components, three metals other than ZnO and MgO, and aluminum oxide (Al) which is a semi-metal oxide. ₂ O ₃ ), yttrium oxide (Y ₂ O ₃ ), gallium oxide (Ga ₂ O ₃ ), lanthanum oxide (La ₂ O ₃ ) and indium oxide (In ₂ O ₃ ).

As a method for producing a sintered body, for example, the above oxide raw material powders are thoroughly mixed, water and an appropriate binder such as polyvinyl alcohol are added thereto, and the mixture is granulated and molded using a metal. The molded body is 1200-1000 in the air using an electric furnace.
It is fired at a temperature of 1600 ° C. Both ends of the fired sinter are polished and adjusted, and electrodes are formed by electrospraying or baking. The obtained resistor may be provided with a high resistance ceramic layer or a glass layer on the side surface of the resistor to prevent creeping discharge during use. Although the obtained resistor exhibits a substantially linear characteristic, when it exhibits a non-linear characteristic, it is effective to apply a high voltage to break the high resistance portion (particularly the grain boundary layer).

As a result of various studies made by the present inventors on reducing the size and weight of the resistor, (1) the resistor used has a resistance value of 4
0 to 4000 Ωcm and withstand switching surge of 400 J /
cm ³ or more, non-linear coefficient of voltage-current characteristics, α is 1.3 or less, and temperature coefficient of resistance is -1 × 10 to ³ / ° C to + 4 × 10 to ³
The change in resistance value should be within ± 10% even after exposure to high temperature of / ° C (20 to 500 ° C) and 500 ° C or higher.
(2) The switching surge withstand capability of the resistor is such that various types of crystal grains having different resistance values are generated in the resistor and is affected by the specific gravity of the resistor, (3) The voltage-current of the obtained resistor. Regarding the characteristics, it was found that the linearity is improved by adding a trivalent metal / semi-metal oxide. Fig. 1 is a schematic diagram of the microstructure of the obtained resistor, Fig. 2 is the relationship between the specific gravity (g / cm ³ ) of the resistor and the switching surge resistance (J / cm ³ ), and Fig. 3 is the obtained resistor. It is a diagram showing the voltage-current characteristics of. It is conceivable that the raw material used for the resistor should be one that is easy to sinter, reacts with each other to generate new crystal grains with different electrical resistances, and has a large specific gravity of the obtained sintered body. Therefore, a resistor containing zinc oxide or magnesium oxide as a basic component and added with aluminum oxide, yttrium oxide, gallium oxide, lanthanum oxide, indium oxide, or the like, which improves the linearity of the voltage-current characteristics of the oxide resistor obtained therefrom. I examined the characteristics of the body. As a result, (1) The switching surge resistance is 800 J / cm ^3, which is about 1.6 times that of the conventional product. (2) The temperature coefficient of resistance is determined by the basic component, zinc oxide (Zn
O) is improved by changing the content of magnesium oxide (MgO) from negative to positive, and (3) the linearity of the resistance value and the voltage-current characteristic is based on the basic components ZnO and MgO and aluminum oxide (Al ₂ O ₃ , yttrium oxide (Y ₂ O ₃ ), gallium oxide (Ga ₂ O ₃ ), lanthanum oxide (La ₂ O ₃ ),
It has been discovered that the addition is improved by adding isidium oxide (In ₂ O ₃ ).

As a desirable composition of the resistor of the present invention, as a basic composition, 70 to 99.7 mol% of zinc oxide, 0.1 to 10 mol% of magnesium oxide, Al ₂ O ₃ , Y ₂ O ₂ and Ga _{2 are used.}
It is to add at least one of oxides of O ₃ , La ₂ O ₃ and In ₂ O _{3 in} an amount of 0.1 to 20 mol%. The temperature coefficient of resistance of MgO changes greatly from negative to positive by changing the content, and at least -1 is more than the above composition range.
It becomes from × 10 to ³ Ω / ° C to more than + 4 × 10 to ² / ° C. On the other hand, if the content of MgO is more than the above range, the switching surge resistance becomes less than 400 J / cm ³ , which is not preferable as a resistor for circuit breaker. In addition, Al ₂ O ₃ , which is a sub-component,
In the case of _{Y 2 O 3, Ga 2 O} 3, La 2 O 3, In 2 O 3 is the resistance value larger than the composition range is higher than 400Omucm, and switching surge withstand capability is lowered cutoff It becomes unsuitable as a dexterous resistor. However, Al ₂ O ₃ , Y ₂ O ₃ , G
_{a 2 O 3, La 2 O} 3, addition of In ₂ O ₃ can be controlled resistance value, and the voltage - linearity of current characteristics are improved. The cause is considered as follows. That is, Al as a subcomponent
₂ O ₃ , Ga ₂ O ₃ , In ₂ O ₃ , and La ₂ O ₃ are (1) mainly reacted with ZnO and MgO which are basic components to form ZnAl ₂ O ₄ and Zn
Y ₃ O ₄ , ZnGaO ₄ , ZnLa ₃ O ₄ , ZnIn ₃ O ₄ ,
MgAl ₃ O ₄ , MgY ₃ O ₄ , MgGa ₂ O ₄ , MgLa ₃
Crystal grains of O ₄ and MgIn ₃ O ₄ are generated, and the electric resistance of the generated crystal grains is 500Ω to 4 × 10 ¹³ Ω and the basic composition Z
It is higher than the crystal grains ZnO and MgO generated from the nO-MgO system, and (2) A in the generated ZnO crystal grains.
It is considered that this is caused by the diffusion of l, Y, Ga, La, and In and increasing the carrier purity of ZnO crystal grains.

A particularly desirable composition of the resistor of the present invention is Zn
O75-92.7 mol%, MgO0.1-10 mol%
And Al ₂ O ₃ 0.2 to 20 mol%, Ga ₂ O ₃ 0.2 to 1
0 mol%, In ₂ O ₃ 0.02 to 5 mol%, La ₂ O ₃ 0.02.
It is to add at least 1 type of 1-10 mol%.

If SiO ₂ is further added to the composition of Al ₂ O ₃ added to the basic components ZnO and MgO, the following effects are obtained. SiO ₂ is not electrically conductive by itself,
In addition, even if it reacts with other elements, it does not produce a conductive substance and exhibits insulating properties. Further, since SiO ₂ reacts with other components to enhance the sinterability, it has the effect of improving the sintered density of the resistor and the mechanical strength. From these things, SiO ₂
First, the resistance value of the resistor can be easily controlled and the resistance value can be increased. Further, the mechanical strength is improved, the electric strength is improved, and the surge resistance can be increased. Therefore, adding SiO ₂ is an effective means for downsizing the resistor.

[0018]

【Example】

(Example 1) Al ₂ O ₃ 510 g (10 mol%), Ga ₂ O ₃ 47 g as auxiliary components to basic components ZnO 3420 g (84 mol%) and MgO 101 g (5 mol%).
(0.5 mol%) and In ₂ O ₃ 369 g (0.5 mol%)
Are accurately weighed and wet mixed in a ball mill for 15 hours. The mixed powder is dried and then granulated by adding 5% by weight of a 5% polyvinyl alcohol / alcohol aqueous solution to the dry raw material powder.
The granulated powder is 35 mmφ at a molding pressure of 450 kg / cm ² using a mold.
Mold to × 20mm. Molded product in air at 1350 ° C, 3
It was held for a time and baked. The rate of temperature increase / decrease at this time is 70
C / h. The electric resistance of the crystal grains generated in the obtained sintered body is about 10 to 50Ω ZnO crystal, about 70 to
100Ω ZnAl ₂ O ₄ crystal, about 400Ω MgO crystal,
About 700 to 4 × 10 ¹³ Ω ZnGa ₂ O ₄ , ZnLa ₂ O ₄ , Z
nY ₂ O ₄ , ZnIn ₂ O ₃ , MgAl ₂ O ₄ , MgY ₂ O ₄ , MgGa
₂ O ₄ , MgLa ₂ O ₄ , MgIn ₂ O ₃ , Al ₂ O ₃ , Ga ₂ O ₃ , L
It was _{a 2 O 3, In 2 O} 3.

Separately, a low melting point crystallized glass AS made by Asahi Glass
F-1400 glass (ZnO—SiO ₂ —B ₂ O ₃ system) powder was suspended in ethyl cellulose and butyl carbitol solution, and the thickness was 50 to 300 μm on the side surface of the sintered body.
It was applied with a brush so that it would be m. 750 this in the atmosphere
The glass was baked by heat treatment at 30 ° C. for 30 minutes. Both ends of the glass-coated sintered body are about 0.5 mm with a lap master.
Each was polished and washed with trichlorethylene. An Al electrode was formed on the washed sintered body by thermal spraying to form a resistor. Switching surge resistance of the crystal of the present invention and a conventional product (carbon dispersed ceramic resistor), temperature coefficient of resistance, 500 in air
Table 1 compares the rate of change in resistance value after the heat treatment at ℃ and the non-linear coefficient α of the voltage-current characteristics.

[0020]

[Table 1]

It can be seen that the product of the present invention has an extremely large switching surge resistance and a small voltage non-linearity coefficient α, which is superior to the conventional product. The temperature coefficient of resistance of the present invention is positive and 10
The AC resistance at 0 μs is 20 A or more, and β in the VI characteristic is 0.9 to 1.0.

The electric resistance of the crystal grains was measured by mirror-polishing the sintered body, analyzing with a scanning electron microscope, forming fine electrodes on the surface of each crystal grain, and measuring the current and voltage.

An example of the cross-sectional structure of the oxide resistor of the present invention is shown in FIGS. In FIG. 4, 1 is a sintered body, 2 is an electrode, and 3 is a film of crystallized glass or a ceramic material. Here, the reason why the crystallized glass or ceramic material film is provided on the side surface of the sintered body is to prevent creeping discharge during use.

(Example 2) ZnO of 65 to 9 as a basic component was added.
9.95 mol%, changing MgO to 0.05 to 20 mol%,
And Al ₂ O ₃ , Y ₂ O ₃ , La ₂ O ₃ and In ₂ as auxiliary components
One type selected from O ₃ and Ga ₂ O ₃ is 0.1 to 30 each
The amount was changed to mol% and the blended amount was accurately weighed. The weighed raw material powder was 1300 to 160 in the air as in Example 1.
The temperature was maintained at 0 ° C. for 3 hours for firing. The density of each of the obtained sintered bodies was 95 to 98% of the theoretical density. Both ends of the fired sintered body were polished by a lap master by about 0.5 mm and ultrasonically cleaned with trichloroethyl. The cleaned sintered body was used as a resistor by forming an Al sprayed electrode. Table 2 shows the resistance value, the switching surge resistance, the resistance temperature coefficient, and the voltage non-linearity coefficient α of the obtained resistor.

[0025]

[Table 2]

From Table 2, composition numbers 10 to 12, composition numbers 16 to 18, composition numbers 21 to 23, composition numbers 27 to 2
9, composition number 32-36, i.e. basic components 80-92.
9 mol% of ZnO contains 5 to 15 mol% of MgO, and further contains Al ₂ O ₃ as an accessory component of 5 to 15 mol% and Y ₂ O.
₃ to 0.5 to 5 mol%, La ₂ O ₃ to 0.3 to 1 mol%,
The characteristics of the resistor containing one or more components selected from Ga ₂ O ₃ of 0.5 to 5 mol% and In ₂ O ₃ of 0.1 to 5 mol% have a resistivity of 110 to 3500 Ωcm and a switching surge resistance. Is 500
~ 780 J / cm ³ , temperature coefficient of resistance -5 × 10 ~ ⁴ Ω / ° C
Below, 4.3 × 10 ⁴ Ω / ° C. or higher and the voltage non-linearity coefficient α of 1.02 to 1.3, which proves to be excellent as a circuit breaker resistor.

Further, it can be seen from Table 2 that the switching surge resistance can be improved by adding MgO to ZnO which is a basic component. However, MgO in the too is contained 20 ^{mol% (No.7) 300J / cm 3} , the conventional 500 J / cm ³
Will be lower than. Further, the temperature coefficient of resistance changes from negative to positive by changing the content of MgO, and if the addition amount of MgO is selected, it is −1 × 10 ³ / ° C. or less, + 4 × 10 ³
It can be seen that it can be reduced to less than / ° C. Further, the resistance value is 43 to 500 even if the content of MgO as a basic component is increased.
It does not show a large change at about Ωcm, but it is a secondary component of Al.
_It can be seen that 91-5 × 10 ⁷ Ωcm is remarkably changed depending on the added amounts of ₂ O ₃ , Y ₂ O ₃ , La ₂ O ₃ , Ga ₂ O ₃ and In ₂ O ₃ . Furthermore, the voltage nonlinear coefficient is Al _{2 which} is a sub-component.
_{O 3, Y 2 O 3,} La 2 O 3, Ga 2 O 3, In 2 O 3 by selecting the optimum amount of such can be significantly improved and 1.02 to 1.2, but the subcomponent Al ₂ O ₃ , Y ₂ O ₃ ,
It can be seen that if the amount of La ₂ O ₃ , Ga ₂ O ₃ and In ₂ O ₃ added is increased too much, the switching surge withstand capability will decrease.

From these facts, a particularly desirable composition for a resistor for a circuit breaker has a basic component of ZnO of 5 to 15
Al ₂ O ₃ as an accessory component to the mixture containing mol%
5 to 15 mol%, Y ₂ O ₃ 0.5 to 5 mol%, La ₂
O ₃ and 0.3 to 1 mol%, the Ga ₂ O ₃ 0.5 5 mol%, the In ₂ O ₃ it is preferable to add 0.1 to 5 mol%.

Example 3 According to the composition of components shown in Table 3,
A resistor was obtained in the same manner as in Example 1. The characteristics of the obtained resistor are shown in Table 3. As can be seen from the table, the resistor of this example has a resistance value of 5 to 9 × 10 ² Ω · cm, an opening / closing surge resistance of 600 to 850 J / cm ³ , and a resistance temperature coefficient of 4 × 10 ⁴ to ⁴ .
1 × 10 to ³ Ω / ℃, voltage non-linearity coefficient is 1.05 to 1.20
It is a resistor of (3 × 10 ^{3 to} 80 A / cm ² ).

Therefore, the resistor of this embodiment having such characteristics is very effective in miniaturization.

[0031]

[Table 3]

(Embodiment 4) FIGS. 6 and 7 show application examples in which the oxide resistor of the present invention is used for a GCB input resistance and for SF ₆ gas-insulated neutral point grounding (NGR), respectively. is there. The resistor 5 used in FIGS. 6 and 7 has the cylindrical shape shown in FIG.

[0033]

As described above, according to the present invention, the switching surge resistance is extremely large, the voltage nonlinearity coefficient of the voltage-current characteristic is small, the temperature coefficient of resistance is positive and small, and the resistance after heat treatment at 500 ° C. There is an effect that an excellent oxide resistor having a small temperature change can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a cross-sectional structure of an oxide resistor according to an example of the present invention.

FIG. 2 shows the relationship between the specific gravity of the oxide resistor and the switching surge withstand capability of the blocking surface.

FIG. 3 is a voltage-current characteristic of an oxide resistor.

FIG. 4 is a cross-sectional view of an oxide resistor according to an example of the present invention.

FIG. 5 is a sectional view of an oxide resistor according to an example of the present invention.

FIG. 6 is a configuration diagram of a GCB closing resistor.

FIG. 7 is a configuration diagram of SF ₆ gas insulation neutral point grounding (NGR).

[Explanation of symbols]

1, 5 ... Oxide resistor, 2 ... Electrode, 3 ... Glass, etc., 4 ...
Inside the cylinder, 6 ... Bushing, 7 ... Tank, 8 ... Condenser, 8 ... Blocking part, 10 ... Oil dashpot, 11 ... Piston for opening / closing operation, 12 ... Air tank.

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] May 8, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction content]

[Document name] Statement

[Title of Invention] Transformer

[Claims]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel power transmission and transformation device, and more particularly to a transformer having a resistor having excellent linearity in a required area.

[0002]

2. Description of the Related Art Conventionally, as a circuit breaker resistor, an aluminum oxide-clay-carbon composition has been known, which has a resistance value of about 400 Ωcm and a circuit breaker withstand switching surge resistance of 500 Joules / cm ³ (hereinafter , J / cm ³ ), a temperature coefficient of resistance of −9 × 10 ⁻³ / ° C. (20 to 250 ° C.), and a maximum operating temperature of 200 ° C.

Recently, there has been a strong demand for downsizing and weight saving of a linear resistor for a circuit breaker along with an increase in transmission voltage. Therefore, as a resistor, (1) increase a switching surge withstand capability. (2) The temperature rises when a switching surge is injected, but the resistance value does not fluctuate even when exposed to high temperatures.
(3) The temperature coefficient of resistance is positive. (4) Materials such as that voltage-current characteristics change linearly are required. The linearity of the voltage-current characteristic here is approximately represented by I (current) = K (constant) × V (voltage) α, and α is desired to be 1.3 or less.

Conventionally, a carbon powder-dispersed ceramic resistor used as a resistor of a circuit breaker is sintered in an inert gas atmosphere to prevent carbon combustion, and the resistance value is a mixed amount of carbon powder. Controlled. This resistor (1) changes its resistance value due to the oxidation of carbon when exposed to a temperature of 400 ° C or higher, and (2) the negative temperature coefficient of resistance is -9 × 10 ^-2 / ° C (2
Since it is large (0 to 250 ° C.), the resistance decreases when the temperature rises, and when the voltage is constant, there is a drawback that the temperature suddenly increases and more heat is generated, causing a runaway state. Further, the above resistor has a problem in its characteristics not only in the circuit breaker but also in the transformer.

Therefore, as a resistor, a ceramic resistor using zinc oxide, which is an oxide type which does not cause combustion, as a basic component is known in JP-A-55-57219. The present inventors have found that the conventional oxide resistor mainly composed of zinc oxide does not sufficiently satisfy the required characteristics described above, and arrived at the present invention.

[0006]

The object of the present invention is to have a resistance of 40 to 4000 Ωcm, good linearity of voltage-current characteristics, and large circuit breaker surge withstand capability.
There is little fluctuation in resistance even when exposed to high temperatures of 00 ° C or higher,
An object of the present invention is to provide a smaller transformer than the conventional one, which includes a linear resistor having a temperature coefficient of resistance in the range of -1 × 10 ^-3 / ° C to + 4 × 10 ^-3 / ° C.

[0007]

DISCLOSURE OF THE INVENTION The present invention is a transformer having a neutral grounding resistor using a ceramic linear resistor containing zinc oxide as a main component. Alternatively, a neutral point grounding resistor using a ceramic linear resistor mainly composed of zinc oxide may be incorporated in an insulating gas atmosphere, and further,
It may be a transformer in which a neutral grounding resistor using a ceramic linear resistor containing zinc oxide as a main component is installed outside.

[0008]

[Function] Zinc oxide crystal grains and 100Ω to 4 ×
A composite sintered body with crystal grains showing an electric resistance value of 10 ¹³ Ω,
A grain boundary layer having a lower electric resistance than the zinc oxide grains exists between the zinc oxide grains. This sintered body may be plate-shaped, column-shaped, or cylindrical, and electrodes are formed on both end surfaces. The electrodes are formed on the entire surface with some edges remaining, and a metal such as Al is formed into a film by thermal spraying or the like.

A grain boundary layer having the same electric resistance value as the crystal grains of zinc oxide may exist between the crystal grains. The crystal grains of oxides excluding zinc oxide compounds and zinc oxide are 100Ω to 4 ×
It is desirable that the resistance is higher than that of zinc oxide in the range of 10 ¹³ Ω. The zinc oxide compound and oxides other than zinc oxide are of the following chemical formulas. That is, the basic component MgO,
In order to further improve the linearity of the voltage-current characteristics, ZnY ₃
O ₄ , ZnGa ₃ O ₄ , ZnLa ₃ O ₄ , ZnAl ₂ O ₄ , Z
nIn ₂ O ₃ , MgAl ₂ O ₄ , MgY ₂ O ₄ , MgGa
₃ O ₄ , MgLa ₃ O ₄ , MgIn ₃ O ₄ , Al ₂ O ₃ , Y
It is to contain at least one selected from ₂ O ₃ , Ga ₂ O ₃ , La ₂ O ₃ and In ₂ O ₃ . In order to form these compounds, a metal or metalloid element such as aluminum (Al), yttrium (Y), gallium (Ga), lanthanum (La) and indium (In) is added to the main components ZnO and MgO. That is. The use of bismuth (Bi) is not desirable. This is because when Bi is used, a high resistance layer is easily formed in the crystal grain boundary phase.

The raw materials for the sintered body are zinc oxide (ZnO) and magnesium oxide (MgO) as the basic components, and as auxiliary components, three metals other than ZnO and MgO, and aluminum oxide (Al) which is a semi-metal oxide. ₂ O ₃ ), yttrium oxide (Y ₂ O ₃ ), gallium oxide (Ga ₂ O ₃ ), lanthanum oxide (La ₂ O ₃ ) and indium oxide (In ₂ O ₃ ).

As a method for producing a sintered body, for example, the above oxide raw material powders are thoroughly mixed, water and an appropriate binder such as polyvinyl alcohol are added thereto, and the mixture is granulated and molded using a metal. The molded body is 1200-1000 in the air using an electric furnace.
It is fired at a temperature of 1600 ° C. Both ends of the fired sinter are polished and adjusted, and electrodes are formed by electrospraying or baking. The obtained resistor may be provided with a high resistance ceramic layer or a glass layer on the side surface of the resistor to prevent creeping discharge during use. Although the obtained resistor exhibits a substantially linear characteristic, when it exhibits a non-linear characteristic, it is effective to apply a high voltage to break the high resistance portion (particularly the grain boundary layer).

As a result of various studies made by the present inventors on reducing the size and weight of the resistor, (1) the resistor used has a resistance value of 4
0 to 4000 Ωcm and withstand switching surge of 400 J /
cm ³ or more, non-linear coefficient of voltage-current characteristics, α is 1.3 or less, and temperature coefficient of resistance is -1 × 10 ^-3 / ° C to + 4 × 10 ^-3
The change in resistance value should be within ± 10% even after exposure to high temperature of / ° C (20 to 500 ° C) and 500 ° C or higher.
(2) The switching surge withstand capability of the resistor is such that various types of crystal grains having different resistance values are generated in the resistor and is affected by the specific gravity of the resistor, (3) The voltage-current of the obtained resistor. Regarding the characteristics, it was found that the linearity is improved by adding a trivalent metal / semi-metal oxide. Fig. 1 is a schematic diagram of the microstructure of the obtained resistor, Fig. 2 is the relationship between the specific gravity (g / cm ³ ) of the resistor and the switching surge resistance (J / cm ³ ), and Fig. 3 is the obtained resistor. It is a diagram showing the voltage-current characteristics of. It is conceivable that the raw material used for the resistor should be one that is easy to sinter, reacts with each other to generate new crystal grains with different electrical resistances, and has a large specific gravity of the obtained sintered body. Therefore, a resistor containing zinc oxide or magnesium oxide as a basic component and added with aluminum oxide, yttrium oxide, gallium oxide, lanthanum oxide, indium oxide, or the like, which improves the linearity of the voltage-current characteristics of the oxide resistor obtained therefrom. I examined the characteristics of the body. As a result, (1) The switching surge resistance is 800 J / cm ^3, which is about 1.6 times that of the conventional product. (2) The temperature coefficient of resistance is determined by the basic component, zinc oxide (Zn
O) is improved by changing the content of magnesium oxide (MgO) from negative to positive, and (3) the linearity of the resistance value and the voltage-current characteristic is based on the basic components ZnO and MgO and aluminum oxide (Al ₂ O ₃ , yttrium oxide (Y ₂ O ₃ ), gallium oxide (Ga ₂ O ₃ ), lanthanum oxide (La ₂ O ₃ ),
It has been discovered that the addition is improved by adding isidium oxide (In ₂ O ₃ ).

As a desirable composition of the resistor of the present invention, as a basic composition, 70 to 99.7 mol% of zinc oxide, 0.1 to 10 mol% of magnesium oxide, Al ₂ O ₃ , Y ₂ O ₂ and Ga _{2 are used.}
It is to add at least one of oxides of O ₃ , La ₂ O ₃ and In ₂ O _{3 in} an amount of 0.1 to 20 mol%. The temperature coefficient of resistance of MgO changes greatly from negative to positive by changing the content, and at least -1 is more than the above composition range.
It becomes from × 10 ^-3 Ω / ° C to more than + 4 × 10 ^-2 / ° C. On the other hand, if the content of MgO is more than the above range, the switching surge resistance becomes less than 400 J / cm ³ , which is not preferable as a resistor for circuit breaker. In addition, Al ₂ O ₃ , which is a sub-component,
In the case of _{Y 2 O 3, Ga 2 O} 3, La 2 O 3, In 2 O 3 is the resistance value larger than the composition range is higher than 400Omucm, and switching surge withstand capability is lowered cutoff It becomes unsuitable as a dexterous resistor. However, Al ₂ O ₃ , Y ₂ O ₃ , G
_{a 2 O 3, La 2 O} 3, addition of In ₂ O ₃ can be controlled resistance value, and the voltage - linearity of current characteristics are improved. The cause is considered as follows. That is, Al as a subcomponent
₂ O ₃ , Ga ₂ O ₃ , In ₂ O ₃ , and La ₂ O ₃ are (1) mainly reacted with ZnO and MgO which are basic components to form ZnAl ₂ O ₄ and Zn
Y ₃ O ₄ , ZnGaO ₄ , ZnLa ₃ O ₄ , ZnIn ₃ O ₄ ,
MgAl ₃ O ₄ , MgY ₃ O ₄ , MgGa ₂ O ₄ , MgLa ₃
Crystal grains of O ₄ and MgIn ₃ O ₄ are generated, and the electric resistance of the generated crystal grains is 500Ω to 4 × 10 ¹³ Ω and the basic composition Z
It is higher than the crystal grains ZnO and MgO generated from the nO-MgO system, and (2) A in the generated ZnO crystal grains.
It is considered that this is caused by the diffusion of l, Y, Ga, La, and In and increasing the carrier purity of ZnO crystal grains.

A particularly desirable composition of the resistor of the present invention is Zn
O75-92.7 mol%, MgO0.1-10 mol%
And Al ₂ O ₃ 0.2 to 20 mol%, Ga ₂ O ₃ 0.2 to 1
0 mol%, In ₂ O ₃ 0.02 to 5 mol%, La ₂ O ₃ 0.02.
It is to add at least 1 type of 1-10 mol%.

The following effects can be obtained by further adding SiO ₂ to the composition obtained by adding Al ₂ O ₃ to the basic components ZnO and MgO. SiO ₂ is not electrically conductive by itself,
In addition, even if it reacts with other elements, it does not produce a conductive substance and exhibits insulating properties. Further, since SiO ₂ reacts with other components to enhance the sinterability, it has the effect of improving the sintered density of the resistor and the mechanical strength. From these things, SiO ₂
First, the resistance value of the resistor can be easily controlled and the resistance value can be increased. Further, the mechanical strength is improved, the electric strength is improved, and the surge resistance can be increased. Therefore, adding SiO ₂ is an effective means for downsizing the resistor.

[0016]

EXAMPLES Example 1 With respect to the basic components ZnO 3420 g (84 mol%) and MgO 101 g (5 mol%), Al ₂ O ₃ 510 g (10 mol%) and Ga ₂ O ₃ 47 g) as secondary components.
5 mol%) and 369 g of In ₂ O ₃ (0.5 mol%) are accurately weighed and wet mixed in a ball mill for 15 hours. The mixed powder is dried and then granulated by adding 5% by weight of a 5% polyvinyl alcohol / alcohol aqueous solution to the dry raw material powder. The granulated powder is 35 mmφ × 20 mm at a molding pressure of 450 kg / cm ² using a mold.
To mold. The molded body was baked at 1350 ° C. for 3 hours in the atmosphere. The rate of temperature increase / decrease at this time is 70 ° C./h. The electric resistance of the crystal grains generated in the obtained sintered body is about 10 to 50Ω ZnO crystal, and about 70 to 100Ω.
ZnAl ₂ O ₄ crystal, about 400Ω MgO crystal, about 700
~ 4 × 10 ¹³ Ω ZnGa ₂ O ₄ , ZnLa ₂ O ₄ , ZnY
₂ O ₄ , ZnIn ₂ O ₃ , MgAl ₂ O ₄ , MgY ₂ O ₄ , MgGa ₂ O
₄ , MgLa ₂ O ₄ , MgIn ₂ O ₃ , Al ₂ O ₃ , Ga ₂ O ₃ , La ₂
It was O ₃ and In ₂ O ₃ .

Separately, a low melting point crystallized glass AS made by Asahi Glass
F-1400 glass (ZnO—SiO ₂ —B ₂ O ₃ system) powder was suspended in ethyl cellulose and butyl carbitol solution, and the thickness was 50 to 300 μm on the side surface of the sintered body.
It was applied with a brush so that it would be m. 750 this in the atmosphere
The glass was baked by heat treatment at 30 ° C. for 30 minutes. Both ends of the glass-coated sintered body are about 0.5 mm with a lap master.
Each was polished and washed with trichlorethylene. An Al electrode was formed on the washed sintered body by thermal spraying to form a resistor. Switching surge resistance of the crystal of the present invention and a conventional product (carbon dispersed ceramic resistor), temperature coefficient of resistance, 500 in air
Table 1 compares the rate of change in resistance value after the heat treatment at ℃ and the non-linear coefficient α of the voltage-current characteristics.

[0018]

[Table 1]

It can be seen that the product of the present invention has an extremely large switching surge resistance and a small voltage non-linearity coefficient α, which is superior to the conventional product. The temperature coefficient of resistance of the present invention is positive and 10
The AC resistance at 0 μs is 20 A or more, and β in the VI characteristic is 0.9 to 1.0.

The electrical resistance of the crystal grains was measured by subjecting the sintered body to mirror polishing, analyzing with a scanning electron microscope, forming fine electrodes on the surface of each crystal grain, and measuring the current and voltage.

An example of the cross-sectional structure of the oxide resistor of the present invention is shown in FIGS. In FIG. 4, 1 is a sintered body, 2 is an electrode, and 3 is a film of crystallized glass or a ceramic material. Here, the reason why the crystallized glass or ceramic material film is provided on the side surface of the sintered body is to prevent creeping discharge during use.

(Example 2) ZnO of 65 to 9 as a basic component was added.
9.95 mol%, changing MgO to 0.05 to 20 mol%,
And Al ₂ O ₃ , Y ₂ O ₃ , La ₂ O ₃ and In ₂ as auxiliary components
One type selected from O ₃ and Ga ₂ O ₃ is 0.1 to 30 each
The amount was changed to mol% and the blended amount was accurately weighed. The weighed raw material powder was 1300 to 160 in the air as in Example 1.
The temperature was maintained at 0 ° C. for 3 hours for firing. The density of each of the obtained sintered bodies was 95 to 98% of the theoretical density. Both ends of the fired sintered body were polished by a lap master by about 0.5 mm and ultrasonically cleaned with trichloroethyl. The cleaned sintered body was used as a resistor by forming an Al sprayed electrode. Table 2 shows the resistance value, the switching surge resistance, the resistance temperature coefficient, and the voltage non-linearity coefficient α of the obtained resistor.

[0023]

[Table 2]

From Table 2, composition numbers 10 to 12, composition numbers 16 to 18, composition numbers 21 to 23, composition numbers 27 to 2
9, composition number 32-36, i.e. basic components 80-92.
9 mol% of ZnO contains 5 to 15 mol% of MgO, and further contains Al ₂ O ₃ as an accessory component of 5 to 15 mol% and Y ₂ O.
₃ to 0.5 to 5 mol%, La ₂ O ₃ to 0.3 to 1 mol%,
The characteristics of the resistor containing one or more components selected from Ga ₂ O ₃ of 0.5 to 5 mol% and In ₂ O ₃ of 0.1 to 5 mol% have a resistivity of 110 to 3500 Ωcm and a switching surge resistance. Is 500
~ 780 J / cm ³ , temperature coefficient of resistance -5 × 10 ^-4 Ω / ° C
Below, 4.3 × 10 ⁻⁴ Ω / ° C. or more and the voltage non-linearity coefficient α are 1.02 to 1.3, which shows that the circuit breaker is excellent as a resistor.

Further, it can be seen from Table 2 that the switching surge resistance can be improved by adding MgO to the basic component ZnO. However, MgO in the too is contained 20 ^{mol% (No.7) 300J / cm 3} , the conventional 500 J / cm ³
Will be lower than. Further, the temperature coefficient of resistance changes from negative to positive by changing the content of MgO, and if the addition amount of MgO is selected, it is -1 × 10 ^-3 / ° C or less, + 4 × 10 ^-3.
It can be seen that it can be reduced to less than / ° C. Further, the resistance value is 43 to 500 even if the content of MgO as a basic component is increased.
It does not show a large change at about Ωcm, but it is a secondary component of Al.
_It can be seen that 91-5 × 10 ⁷ Ωcm is remarkably changed depending on the added amounts of ₂ O ₃ , Y ₂ O ₃ , La ₂ O ₃ , Ga ₂ O ₃ and In ₂ O ₃ . Furthermore, the voltage nonlinear coefficient is Al _{2 which} is a sub-component.
_{O 3, Y 2 O 3,} La 2 O 3, Ga 2 O 3, In 2 O 3 by selecting the optimum amount of such can be significantly improved and 1.02 to 1.2, but the subcomponent Al ₂ O ₃ , Y ₂ O ₃ ,
It can be seen that if the amount of La ₂ O ₃ , Ga ₂ O ₃ and In ₂ O ₃ added is increased too much, the switching surge withstand capability will decrease.

From these facts, a particularly desirable composition for a resistor for a circuit breaker has a basic component of ZnO of 5 to 15
Al ₂ O ₃ as an accessory component to the mixture containing mol%
5 to 15 mol%, Y ₂ O ₃ 0.5 to 5 mol%, La ₂
O ₃ and 0.3 to 1 mol%, the Ga ₂ O ₃ 0.5 5 mol%, the In ₂ O ₃ it is preferable to add 0.1 to 5 mol%.

(Example 3) According to the composition of components shown in Table 3,
A resistor was obtained in the same manner as in Example 1. The characteristics of the obtained resistor are shown in Table 3. As can be seen from the table, the resistor of this example has a resistance value of 5 to 9 × 10 ² Ω · cm, a switching surge resistance of 600 to 850 J / cm ³ , and a resistance temperature coefficient of 4 × 10 ⁻⁴ to.
1 × 10 ^-3 Ω / ℃, voltage non-linearity coefficient is 1.05 to 1.20
It is a resistor of (3 × 10 ^{−3 to} 80 A / cm ² ).

Therefore, the resistor of this embodiment having such characteristics is very effective in miniaturization.

[0029]

[Table 3]

(Embodiment 4) FIGS. 6 and 7 show application examples in which the linear resistor of the present invention is used for a GCB input resistance and for SF ₆ gas insulated neutral point grounding (NGR), respectively. . The resistor 5 used in FIGS. 6 and 7 has the cylindrical shape shown in FIG.

[0031]

As described above, according to the present invention, the switching surge resistance is extremely large, the voltage nonlinearity coefficient of the voltage-current characteristic is small, the temperature coefficient of resistance is positive and small, and the resistance after heat treatment at 500 ° C. By adopting an excellent linear resistor that changes little with temperature, it is possible to obtain a smaller transformer than before.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a cross-sectional structure of a linear resistor according to an example of the present invention.

FIG. 2 shows the relationship between the specific gravity of the linear resistor and the switching surge resistance of the breaking surface.

FIG. 3 is a voltage-current characteristic of a linear resistor.

FIG. 4 is a sectional view of a linear resistor according to an embodiment of the present invention.

FIG. 5 is a sectional view of a linear resistor according to an embodiment of the present invention.

FIG. 6 is a configuration diagram of a GCB closing resistor.

FIG. 7 is a configuration diagram of SF ₆ gas insulation neutral point grounding (NGR).

[Explanation of reference numerals] 1,5 ... Linear resistor, 2 ... Electrode, 3 ... Glass, etc., 4 ... Cylindrical interior, 6 ... Bushing, 7 ... Tank, 8 ... Capacitor, 8 ... Breaker, 10 ... Oil dashpot, 11 ... Piston for opening / closing operation, 12 ... Air tank.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shingo Shirakawa 1-1-1 Kokubun-cho, Hitachi-shi, Ibaraki Hitachi Kokubun factory

Claims (1)

[Claims] 1. A power transmission and transformation device comprising a resistor in which a linear resistor is enclosed in an insulating medium.