JPH0254502A - Nonlinear-to-voltage resistor - Google Patents

Abstract

PURPOSE:To assure satisfactory characteristics of the title resistor against multiple lightning with a reduced temperature change of voltage-current characteristics by allowing the title resistor to include at least beta and delta type crystal phases of a given ratio in a crystal phase of bismuth oxide in the resistor. CONSTITUTION:The title nonlinear-to-voltage resistor includes zinc oxide as the chief ingredient and a metal oxide such as bismuth oxide, antimony oxide, and silicon oxide, etc., as the additive. The crystal phase of bismuth oxide includes at least betaand delta two types of crystal phases and satisfies the following relationship with the assumption of the amounts of the beta and delta type crystal phases to be beta and delta: 60<=beta/beta+deltaX100<=90. The delta phase mainly serves to reduce a V1mA changing rate after application of lightning surge and also serves to improve surge resistance. The betaphase mainly serves to reduce a changing rate of V-I characteristics with respect to temperature, which is further improved under its coexistence with the delta phase. However, only the beta phase deteriorates the lifetime of the resistor, unadvantageously. Additionally, the gamma phase, although improving the lifetime, badly affects the aforementioned characteristic and so may preferably be less than 0.5wt.% in contents to the utmost.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a voltage nonlinear resistor containing zinc oxide as a main component.

(Prior Art) Conventionally, zinc oxide is the main component, and Bi, O, Sb, 0.
.

5in2. Co20. It is widely known that resistors containing small amounts of additives such as , MnO□, etc. exhibit excellent voltage nonlinearity, and are used in lightning arresters and the like by taking advantage of this property.

In particular, when used as a lightning arrester, even if an excessive current flows due to a lightning strike, the current is grounded by a voltage nonlinear resistor that is normally an insulator and becomes a conductor when a voltage higher than the specified voltage is applied. , accidents caused by lightning can be prevented.

(Problem to be Solved by the Invention) In addition to the zinc oxide crystal phase, the voltage nonlinear resistor includes α-type, β-type, γ-type, and δ-type bismuth layers and pyrochlore phases as grain boundary layers. However, depending on the quantity ratio, the rate of change in VISA after applying a surge may become large, or the rate of change of V-1 characteristics with respect to temperature may become large, and in either case, the characteristics against multiple lightning may deteriorate. was there. Furthermore, when the rate of change in VlaA is large as described above, there is a problem that there is a risk of thermal runaway in a gapless arrester, and that it becomes impossible to interrupt a follow-up current in a surge arrester with a gap.

An object of the present invention is to solve the above-mentioned problems and provide a voltage nonlinear resistor that exhibits good characteristics even against multiple lightning strikes.

(Means for Solving the Problems) The voltage nonlinear resistor of the present invention contains zinc oxide as a main component,
In voltage nonlinear resistors containing metal oxides such as bismuth oxide, antimony oxide, and silicon oxide as additive components,
It is characterized in that the crystal phase of bismuth oxide contains at least two types of crystal phases, β-type and δ-type, and satisfies the following relationship, where the amounts of β-type and δ-type crystals are β and δ. be.

(Function) In the above-mentioned configuration, the voltage nonlinear resistor in which the crystal phase of bismuth oxide in the resistor includes at least a predetermined ratio of β-type and δ-type crystal phases, as will be clear from the examples described later, is provided. This is based on the discovery that the rate of change in VISA after application of a surge is small, and the rate of change in V-1 characteristics with respect to temperature is small.

As a result, it is possible to obtain a voltage nonlinear resistor that has good surge resistance and good C resistance against multiple lightning strikes, and also has a good lifespan without thermal runaway.

Here, to explain the effects of each phase, the δ phase mainly has the effect of reducing the rate of change in Vl+aA after application of a lightning surge, and also has the effect of improving surge resistance. The β phase mainly has the effect of reducing the rate of change of the V-1 characteristic with respect to temperature, and its coexistence with the δ phase can further improve the effect. However, using only the β phase is not preferable because the life will deteriorate. In addition, although the T phase has a good lifespan, it has a negative effect on the other above characteristics, so at most Q, 5 wt.
% or less. Moreover, it is preferable not to contain a pyrochlore phase.

Furthermore, during the manufacturing process, glass frit is added at 0.01~0°Q.
Add 3wt%. Further, it is preferable to add silicon oxide in an amorphous form because it stabilizes the grain boundary layer.

The relationship between β and δ is 70≦β/(β+δ)×100≦
A value of 80 is preferable because the effects of the present invention become even more pronounced.

(Example) To obtain a voltage nonlinear resistor whose main component is zinc oxide,
First, zinc oxide raw material adjusted to a predetermined particle size, bismuth oxide, cobalt oxide, manganese oxide, adjusted to a predetermined particle size,
A predetermined amount of additives such as antimony oxide, chromium oxide, preferably amorphous silicon oxide, nickel oxide, borium oxide, silver oxide, etc. are mixed. In this case, silver nitrate or boric acid may be used instead of silver oxide or boron oxide. Preferably, bismuth borosilicate glass containing silver is used. At this time, a predetermined amount of polyvinyl alcohol aqueous solution or the like is added to these raw material powders.

Preferably, a predetermined amount of aluminum nitrate solution is added as a source of aluminum oxide. This mixing operation preferably uses an emulsifying machine.

Next, deaeration is performed under reduced pressure, preferably at a vacuum level of 200 mmHg or less, to obtain a mixed slurry. Here, the water content of the mixed slurry is 30
~35wt%, and the viscosity of the mixed slurry is 100%.
It is preferable to set it to ±5ocp. Next, the obtained mixed slurry was fed to a spray dryer and the average particle size was 50 to 150 μm1.
Preferably, the diameter is 80 to 120 μm and the water content is 0.5 to 2.
Qwt%, more preferably 0.9 to 1.5 wt% granulated powder is granulated. Next, the obtained granulated powder is molded into a predetermined shape under a molding pressure of 800 to 1000 kg/cm 2 in a molding step. Then, the molded body is heated and cooled at a rate of 50
800-1000℃ at ~70℃/hr, holding time 1-5
Fired under the condition of time. In addition, before calcining, the molded body was heated to 400 to 600°C at a heating/cooling rate of 10 to 100°C/hr.
It is preferable to scatter and remove the binder for a holding time of 1 to 10 hours.

Next, an insulating coating layer is formed on the side surface of the calcined body. In the present invention, Bi, 03.5b203. ZnO.

An oxide paste prepared by adding an organic binder such as ethyl cellulose or n-butyl carbitone acetate to a predetermined amount of S10□ or the like is applied to the side surface of the calcined body to a thickness of 60 to 300 μm. Next, this is heated at a rate of 20 to 60°C/h.
r, 1000-1300°C, preferably 1100-12
Main firing is performed at 50° C. for 3 to 7 hours. A glass paste prepared by adding ethyl cellulose, butyl calpitol, n-butyl acetate, etc. as an organic binder to glass powder is applied to a thickness of 100 to 300 μm on the above-mentioned insulating coating layer, and the temperature is raised and cooled in air at a rate of 50 to 300 μm. 200℃/hr,
It is preferable to form the glass layer by heat treatment at 400-900° C. for 0.5-2 hours.

After that, both end faces of the obtained voltage nonlinear resistor are S+C,
A ji! 203. Diamond etc. #400~
Polishing is performed using water, preferably oil, as the polishing liquid with a polishing agent equivalent to 2000 ml. Next, after cleaning the polished surfaces, metallicon electrodes made of aluminum metallicon or the like are provided on both polished end surfaces by, for example, thermal spraying to obtain a voltage nonlinear resistor.

In the above-mentioned manufacturing method, at least a predetermined amount of β-B1203 crystal phase is produced in the sintered body by various combinations of the types and amounts of raw materials, main firing conditions, main firing cooling rate, heat treatment conditions after main firing, etc. and δ-Bi, the voltage nonlinear resistor of the present invention containing the 03 crystal phase can be manufactured, and a voltage nonlinear resistor with good target v4 rate of change, rate of change of V-1 characteristic with respect to temperature, etc. can be obtained. It is something that can be done.

Hereinafter, the results of actually measuring various characteristics of voltage nonlinear resistors within and outside the scope of the present invention will be described.

EXAMPLE According to the method described above, Bi2O,, Co3O4, Mn
O2゜5b20. e Cr2k each from 0.1 to 2,
0 MoJL+%, 8β(NO3)3・9H,00,0
01-0.01 mol%, bismuth borosilicate glass containing silver 0.01-Q, 3 wt%, amorphous SiO□0.5
~3.0 mol%, balance ZnO from a raw material with a diameter of 47
Invention samples N011-7 and comparative samples N011-7 having crystal phases shown in Table 1 with a shape of 22.5 mm and a thickness of 22.5 mm.
3 voltage nonlinear resistors were prepared.

For the prepared resistors of the present invention and comparative examples, temperature characteristics, Vl+++A reduction rate, lightning surge resistance 1i, and switching surge resistance were measured, and the energization life pattern was determined. The results are shown in Table 1. Here, the temperature characteristics are VlmA and V at 150°C with respect to VISA and V40kA at 25°C. , was determined as the rate of change of A.

At 150°C, VlmA decreases compared to 25°C, and V,
. , increases. VIIIA reduction rate is Vl before and after applying 30kA current 10 times with a current waveform of 8720μs.
It was determined from +aA. The lightning surge resistance was indicated as "X" if the product was destroyed after repeated application of 130 kA and 150 kA current twice with a current waveform of 4710 μs, and "O" if it was not destroyed. Opening/closing surge withstand current of 800A and 100OA at 2m
Those that were destroyed after repeated application of the current waveform s for 20 times were indicated as x1. Those that were not destroyed were indicated as 0. Furthermore, the energization pattern was determined from the relationship between leakage current and time shown in FIG. In FIG. 1: A indicates the best one, B indicates a good one because it returns without runaway, and C indicates one that causes thermal runaway.

The amount of each crystal phase was determined by an internal standard method using X-ray diffraction.

From the results in Table 1, it can be seen that the resistor of the present invention, which contains at least a predetermined ratio of β phase and δ phase, has better temperature characteristics and VlaA reduction rate than the comparative example, and also has better other properties. I understand that.

Note that although the energization life pattern of the present invention is not A, there is no fear of thermal runaway. In the case of a lightning arrester with a gap, the element is always energized, so B does not pose a problem at all.

(Effects of the Invention) As is clear from the above explanation, the voltage nonlinear resistor of the present invention contains at least a predetermined ratio of β phase and δ phase, so that the change in Vl+++A due to lightning surge application is small and the voltage is small. - It is possible to obtain good characteristics against multiple lightning with small temperature changes in current characteristics, and also to obtain other characteristics such as good surge resistance and lifespan.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the energization pattern in terms of the relationship between leakage current and time.

Claims (1)

[Claims] 1. In a voltage nonlinear resistor that contains zinc oxide as a main component and metal oxides such as bismuth oxide, antimony oxide, and silicon oxide as additive components, bismuth oxide has at least two types of crystal phases: β type and δ type. including,
A voltage nonlinear resistor characterized by satisfying the following relationship: 60≦β/β+δ×100≦90, where the amount of crystals of β type and δ type is β and δ.