JPH05267013A - Power resistor - Google Patents

Abstract

PURPOSE:To reduce the change due to surge absorption in the resistance value of zinc oxide particles as a sintered body having a particular amount of titanium solid solution. CONSTITUTION:A sintered oxide body mainly comprising zinc oxide is made as a resistance body for electric power where zinc oxide particles have 0.005 to 0.1mol% solid solution of titanium when converted to titanium oxide. The title power resistor 1 for electric power is formed to a disk shape or the like by using a mixture of zinc oxide powder and a predetermined amount of titanium oxide powder, and this moldings is baked at 1200 to 1500 deg.C in the atmosphere. The temperature rising rate during baking is 50 to 200 deg.C/hr and the temperature falling rate of 200 to 300 deg.C/hr to the predetermined temperature during falling. And quick cooling is performed after the predetermined temperature. Both the main surfaces of a sintered body 2 obtained are polished, flame- coated and baked to form an electrode 3. Consequently, a power resistor having a low resistance temperature coefficient and a small resistance changing rate by surge absorption can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power resistor suitable for absorbing an excessive surge.

[0002]

2. Description of the Related Art Currently, various electric power resistors are used for controlling currents such as circuit breakers, various controls associated with starting and regeneration of electric motors, and grounding when an abnormality occurs in a power transmission system. There is. These resistors are composed of metal resistors, ceramic resistors, and various composites.

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

This carbon particle dispersed type ceramic resistor is
Although there is an advantage that the resistivity can be changed by adjusting the amount of dispersed carbon powder, the porosity is as high as 10 to 30% and the denseness is inferior, so that the following problems occur. That is,
First, the heat capacity per volume is 2 J / cm ³ -Since it is as small as K, the discharge withstand capability is small. As a result, the temperature rise due to heat generation due to the absorption of surge is remarkable. Secondly, when the switching surge is absorbed, a discharge occurs between the carbon powders, resulting in a through discharge. Thirdly, when exposed to a high temperature, the carbon particles controlling the resistance value are oxidized and the resistance value fluctuates greatly. Fourth, the temperature coefficient of resistance is negative. Therefore, when used as a resistor for a closing resistor, when the temperature of the resistor rises due to absorption of the switching surge, the resistivity of the resistor becomes small and thermal runaway occurs, and the switching surge cannot be completely absorbed. Due to the above problems, as a resistor of the high voltage circuit breaker,
The conventional resistor disclosed in JP-A-58-139401 has many problems.

Further, with the recent miniaturization of circuit breakers due to technological development, miniaturization of closing resistors for absorbing switching surges is required. In order to miniaturize the closing resistor, the heat capacity per unit volume of the resistor used is indispensable.
2 J / cm ³ of conventional resistor ・ With a heat capacity of K, it is difficult to make the closing resistor smaller.

[0006] For such a problem, for example, the heat capacity per unit volume is about 2.8 like zinc oxide ceramics.
J / cm ³ -The problem can be solved by using a ceramic resistor having a large K and a positive temperature coefficient of resistance.

[0007] Zinc oxide ceramics usually have a negative temperature coefficient of resistance, but it is known that the temperature coefficient of resistance becomes positive when an oxide of some kind is added. For example, by adding titanium oxide (TiO ₂ ) and nickel oxide (NiO) to zinc oxide, the resistivity and temperature coefficient of resistance have been widely adjusted (Solid-St
ate Electronics Pergamon Press 6, 111 (1963), US
P-2892988, USP-2933586).

However, the above resistor has the following problems. That is, by absorbing the switching surge,
The resistor instantly raises the temperature by 100 ° C. or more (approximately 0.01 seconds). By repeating this heating / cooling cycle, the resistivity of the resistor changes. For example, in the above resistor, the resistivity increases by 1 to 2% in one heating / cooling cycle. Therefore, if the heating / cooling cycle is repeated 100 times, the resistivity becomes 3 to 7 times the original resistivity.

Under these circumstances, although zinc oxide ceramics are known for their electrical properties such as resistivity and temperature change of resistivity, and thermal properties such as heat capacity, they are resistors for surge absorption. However, it has a problem and has not been used yet.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned conventional problems, and has a large heat capacity, a small change in resistance value due to surge absorption, and a low temperature coefficient for electric power having a positive resistance temperature coefficient. It is intended to provide an antibody.

[0011]

The present invention provides (Zn
In a sintered body containing O) as a main component, zinc oxide particles convert titanium into titanium oxide (TiO ₂ ) in an amount of 0.005 to
It is a low antibody for electric power which is characterized by forming a solid solution of 0.1 mol%.

The low power antibody of the present invention can be produced, for example, as follows. A predetermined amount of titanium oxide powder is added to the zinc oxide powder, a predetermined amount of water and a binder are added, and ZrO ₂ balls are used as a grinding medium, and grinding and mixing are performed for a predetermined time in a ball mill. After the obtained mixture is dried, it is granulated and molded into a disk shape or the like with a mold. The formed body is fired in the atmosphere at a temperature of 1200 to 1500 ° C. for a predetermined time in an electric furnace. The temperature rising rate during firing is 50 to 200
℃ / hour, the temperature drop is 20 ~ 300 ℃ / hour to a predetermined temperature,
From the predetermined temperature, rapid cooling (cooling in the furnace) was performed. Both main surfaces of the obtained sintered body are polished and electrodes are formed by means such as thermal spraying or baking to obtain a resistor having a linear current-voltage characteristic. The side surface of the element can be formed by baking or thermal spraying a resin or inorganic high resistance layer, if necessary. The characteristics of this power resistor were evaluated as follows. The specific resistance is a value at room temperature, and the temperature coefficient of resistance is represented by a change rate per 1 ° C. between changes in the resistance value at room temperature and the resistance value at 100 ° C. In addition, the resistance change rate is a rate of change in resistance value after applying a shock wave corresponding to 200 J / cc 20 times to a sample with a diameter of 20 mφ manufactured under the same conditions as a percentage of the initial value. To investigate the relationship between device characteristics and low antibody, the structure and composition distribution of low antibody were investigated. When the constituent phases of the obtained sintered body were examined by XRD, Zn ₂ TiO ₄ phase was found in addition to the zinc oxide phase as the main phase. According to SEM observation with EDX, in the structure of the above-mentioned sintered body, particles containing zinc as a main component and particles containing titanium and zinc as constituent components were observed at the grain boundaries. Therefore, the obtained sintered body is composed of particles containing zinc oxide as the main component and spinel particles containing titanium oxide and zinc oxide as the components. It is considered that the conductivity of the low antibody largely depends on the zinc oxide particles and their grain boundaries, and it is considered that changes in the composition of the zinc oxide particles when the manufacturing conditions are changed are closely related to the device characteristics. Zinc oxide particle components were separated and extracted from the low antibody, which is a complex of zinc oxide particles and spinel particles, using the method of selective etching with acid, and the composition was determined by chemical analysis. If the amount of titanium oxide dissolved in the zinc oxide particles is 0.005 mol% or more, the temperature coefficient of resistance becomes positive, and if it is 0.1 mol% or less, the resistance change rate is small, which is sufficient for low antibody performance. Got a relationship that is.
Therefore, the crystalline body is obtained by blending and mixing the raw materials so that the above predetermined ratio is obtained, then molding this powder, firing the molded body, and quenching from a predetermined temperature. When the amount of titanium oxide solid-dissolved in the particles is in the range of 0.005 mol% to 0.1 mol%, the one having desired characteristics is obtained. The firing temperature is 1300 ° C to 1
The temperature is preferably 500 ° C., and the rate of temperature decrease after the maximum temperature is maintained is preferably 20 ° C./hour to 300 ° C./hour. The quenching start temperature is preferably 1200 to 900 ° C. When the firing temperature is high, the cooling rate is small, and the rapid cooling start temperature is preferably low. Conversely, when the firing temperature is low, the cooling rate is large,
It is preferable to increase the quenching start temperature. By selecting such a cooling pattern, the amount of titanium oxide dissolved in the zinc oxide particles can be controlled to a predetermined amount. Note that these process conditions need to be adjusted depending on the overall composition of the sintered body.

The low antibody according to the present invention has a pair of electrodes formed on both end faces of a sintered body made of the above zinc oxide-based ceramic. This electrode is preferably made of aluminum or nickel. This electrode is formed on both end surfaces of the sintered body by thermal spraying or sputtering. In addition, this resistor preferably has an insulating phase made of insulating glass or glass ceramic in order to prevent creeping discharge on the side surface.

A low antibody for a circuit breaker according to one embodiment of the present invention is shown in FIG. Low antibodies are mainly zinc oxide,
It is provided with a hollow cylindrical sintered body containing a titanium component, and a pair of electrodes (only the upper surface is shown) formed on both end surfaces thereof. Further, an insulating layer is formed on the side surface of the resistor.

[0015]

Embodiments of the present invention will be described below with reference to FIG.

As shown in FIG. 1, this low antibody has a hollow cylindrical sintered body made of zinc oxide containing titanium oxide. Aluminum electrodes are formed on both end surfaces of this sintered body. Further, an insulating layer made of borosilicate glass is formed on the side surface of this sintered body. This low-power antibody was manufactured as follows.

Zinc oxide (ZnO) powder, titanium oxide
(TiO₂) The powder is weighed in the ratio shown in Table 1, pure water solvent
Medium, using resin ball mill and zirconia grinding medium
And wet-mixed for 24 hours. After removing the pure water,
Add a predetermined amount of PVA aqueous solution as a der
It was made into a granulated powder through. This granulated powder is pressed at a molding pressure of 500 kg /
cm² Outer diameter 148mmφ, inner diameter 48mm
A hollow cylindrical molded body having a φ and a height of 32 mm was prepared. This molding
Place the body in a container made of aluminum oxide and place it in air 12
After holding at a temperature of 00 to 1400 ° C for 2 hours, the temperature decrease rate is 20
The temperature is lowered to a predetermined temperature at ~ 300 ° C / hour (Table 1), and
After that, rapid cooling was performed by cooling in the furnace. Side of this sintered body
Then, after applying borosilicate glass powder, bake,
An insulating phase was formed. After that, grind both end faces of this sintered body
Processed, outer diameter 127 mmφ, inner diameter 41 mmφ, height 25.
The size is 4 mm, and the aluminum electrode is melted on the end face after cleaning.
It was formed by injection to obtain low antibody. Zinc oxide particles in sintered body
The child components are separated by the selective etching method shown below.
Extracted and subjected to chemical analysis. The sintered body is crushed and powdered
Sample. 5% acetic acid and 5 milk per 1 g sample
Add 50 ml of the acid mixture and sonicate for 90 minutes.
The ZnO particles were dissolved while applying the voltage. Filter lysate
Filter and then quantify titanium by ICP emission spectroscopy.
It was. The production conditions, analysis results and characteristics of these low antibodies
The relationship is also shown in Table 1. As a low antibody input, resistance
Rate is 1.5 × 10-10^Four Ω ・ cm, temperature coefficient of resistance is absolute
The value is preferably 0.5% or less, and the sign is preferably positive. Also surge
The resistance change rate due to absorption is suitably 10% or less. Table 1
The amount of titanium oxide dissolved in the zinc oxide particles is 0.00
If it is 5 mol% or more, the temperature coefficient of resistance becomes a positive value.
Resistance value against repeated surge application at 0.1 mol% or less
We obtained a relationship with little change and sufficient as a low antibody. Implementation
The peripheral composition of the example was prepared in the same manner as in the example, and two kinds of resistance were prepared.
An antibody was obtained. The relationship between the component ratio and characteristics of the low antibody of these comparative examples
Table 1 shows the members.

When the amount of titanium oxide dissolved in the zinc oxide particles is less than the range of the present invention, the temperature coefficient of resistance is negative and the absolute value is large. On the other hand, if it exceeds 0.1 mol%, the rate of change in resistance exceeds 10%, so that it is also unsuitable as a low antibody input for electric power.

[0019]

[Table 1]

[0020]

As described above, according to the present invention, it is possible to provide a low antibody for electric power which has a good controllability of resistance value, a small temperature coefficient of resistance and a small resistance change rate due to surge absorption.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

[Explanation of symbols]

 1 ... Low antibody for electric power 2 ... Sintered body 3 ... Electrode 4 ... Insulating layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Fumio Ueno 1 Komukai Toshiba Town, Kawasaki City, Kanagawa Prefecture Toshiba Research Institute Co., Ltd.

Claims (1)

[Claims] 1. In an oxide sintered body containing zinc oxide (ZnO) as a main component, zinc oxide particles form 0.005 to 0.1 mol% solid solution of titanium in terms of titanium oxide (TiO ₂ ). A power resistor characterized by the above.