JPH0734406B2 - Voltage nonlinear resistor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage non-linear resistor used in a lightning arrester, and more particularly to electrodes of the voltage non-linear resistor.

[0002]

2. Description of the Related Art Conventionally, a resistor containing zinc oxide as a main component and a small amount of additives such as silicon oxide, antimony oxide, nickel oxide, chromium oxide, manganese oxide, etc. exhibits excellent voltage nonlinearity. It is widely known and is used for lightning arresters, etc., due to its properties.

In these voltage nonlinear resistors, it is necessary to provide electrodes on both end faces of a disk-shaped resistor when actually used, and as electrodes used in conventional voltage nonlinear resistors,
Aluminum, silver, etc. are well known. In particular, aluminum sprayed electrodes are often used because they are low in cost and suitable for mass production.

[0004]

However, in the above-mentioned aluminum sprayed electrode, a part of aluminum is oxidized during spraying, which obstructs the micro contact between the electrode and the resistor, and the electrical characteristics, especially the discharge withstand capability. There was a problem that got worse.

The object of the present invention is to solve the above problems,
By improving the electrodes, it is intended to provide a voltage non-linear resistor having high electrical characteristics, particularly high discharge withstand capability.

[0006]

The voltage non-linear resistor of the present invention is a voltage non-linear resistor mainly comprising zinc oxide having an aluminum sprayed electrode, wherein the Al ₂ O ₃ content in the aluminum sprayed electrode is Is 10 wt% or less.

[0007]

In the above-mentioned structure, the present invention sets the Al ₂ O ₃ content in the aluminum sprayed electrode to 10 wt% or less, in other words, the allowable amount of Al ₂ O _{3 into} the electrode is 10 wt%.
It has been found that by setting the content to be not more than%, it is possible to obtain a voltage non-linear resistor having high electrical characteristics, particularly high discharge resistance, and improved electrode adhesion strength. Here, the reason why the Al ₂ O ₃ content in the aluminum sprayed electrode is limited to 10 wt% or less is that, as will be apparent from the examples described later, when it exceeds 10 wt%, the lightning surge discharge withstand capability extremely deteriorates. Is.

[0008]

EXAMPLE To obtain a voltage nonlinear resistor containing zinc oxide as a main component, first, a zinc oxide raw material adjusted to a predetermined particle size and bismuth oxide, cobalt oxide, manganese oxide, antimony oxide adjusted to a predetermined particle size, A predetermined amount of an additive consisting of chromium oxide, preferably amorphous silicon oxide, nickel oxide, boron oxide, silver oxide is 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. Alternatively, the additive may be calcined at 800 to 1000 ° C. and then pulverized to have a predetermined particle size, and the zinc oxide raw material may be mixed. At this time, a predetermined amount of binder (for example, polyvinyl alcohol aqueous solution) is added to these raw material powders.
And a dispersant and the like. Also preferably, an aluminum nitrate aqueous solution is added.

Next, it is preferable to carry out degassing under reduced pressure at a vacuum degree of 200 mmHg or less, and the water content of the mixed slurry is preferably about 30 to 40 wt%. Then, the obtained mixed sludge is supplied to a spray dryer to have an average particle size of 50 to 150 μm, preferably 80 to 120 μm,
Moisture content 0.5-2.0wt%, more preferably 0.7-1.5wt
Granulate% granulated powder. 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.

Next, the molded body is heated / cooled at a temperature of 10 to 100 ° C.
/ hr at a temperature of 400 to 700 ° C to remove organic components by scattering to obtain a defatted body. Next, the degreased body is heated to 800 ~ at a heating rate of 50 ~ 70 ° C / hr.
Baking is performed at 1000 ° C for a holding time of 1 to 5 hours to obtain a calcined body.
Next, a high resistance layer is formed on the side surface of the calcined body. In this example, a mixture paste for insulation coating having a predetermined amount of bismuth oxide, antimony oxide, zinc oxide, silicon oxide, etc., added with ethyl cellulose, butyl carbitol, n-butyl acetate, etc. as an organic binder to a thickness of 30 to 300 μm. Apply to the side of the calcined body.

Next, this is heated / cooled at a rate of 20 to 100 ° C./hr,
Maximum holding temperature 1000 to 1300 ℃, preferably 1050 to 1250 ℃, 3
Main firing is performed under the condition of ~ 7 hours. It is preferable that the temperature lowering rate during the main firing is 200 ° C./hr or less. Further, it is more preferable to set the cooling rate between the maximum temperature and 800 ° C to 30 to 70 ° C / hr.

Then, a glass paste obtained by adding ethyl cellulose, butyl carbitol, n-butyl acetate or the like as an organic binder to glass powder is applied to the high resistance layer on the side surface at a ratio of 50 to
Coat to a thickness of 300 μm and raise and lower the temperature in air at a rate of 50 to 200.
The glass layer is preferably formed by heat treatment under the conditions of 400 ° C./hr and 400 to 800 ° C. holding time of 0.5 to 4 hours.

After that, both end faces of the obtained voltage non-linear resistor are polished with a diamond grindstone or the like. Next, after cleaning the polished surface, electrodes are sprayed on the polished both end surfaces with aluminum to obtain a voltage non-linear resistor. At this time, in the present invention, since the Al ₂ O ₃ content in the obtained aluminum sprayed electrode is 10 wt% or less, for example, the atmosphere around the spraying nozzle of the spraying apparatus, oxygen partial pressure compared to normal air It is necessary to have a lowered atmosphere or an inert atmosphere.

The results of actually measuring various characteristics of voltage nonlinear resistors within and outside the range of the present invention will be described below. Example 1 With respect to the voltage non-linear resistor element body having the same composition and the same electric characteristics produced by the above-described manufacturing method, the oxygen partial pressure in the vicinity of the spray nozzle at the time of spraying was controlled, and the results are shown in Table 1 below. As shown, a disk having a diameter of 50 mm and a thickness of 20 mm of Sample Nos. 1 to 4 of the present invention whose Al ₂ O ₃ content in the aluminum spray electrode is within the range of the present invention and Sample No. 1 of Comparative Example outside the scope of the present invention A voltage-shaped non-linear resistor was prepared.

With respect to the obtained voltage non-linear resistor, lightning surge discharge withstand capability was measured. The results are shown in Table 1. In Table 1, the lightning surge discharge withstand capability was obtained by converting the light withstand capability after applying a lightning surge current with a current waveform of 4/10 μs twice at 5 minute intervals to an energy value (clear value).

[0016]

[Table 1]

From the results shown in Table 1, the samples No. 1 to 4 of the present invention having an Al ₂ O ₃ content of 10 wt% or less in the aluminum spray electrode.
Indicates that the lightning surge discharge withstand capability is better than that of the comparative sample No. 1 having an Al ₂ O ₃ content outside the range of the present invention.

[0018]

As is apparent from the above description, according to the present invention, the Al ₂ O ₃ content in the aluminum sprayed electrode is 10% or less.
By setting the content to be wt% or less, it is possible to obtain a voltage non-linear resistor having high electrical characteristics, particularly high discharge withstand capability, and improved electrode adhesion strength.

Claims (1)

[Claims] 1. A voltage non-linear resistor having a zinc oxide as a main component and having an aluminum sprayed electrode, characterized in that the Al ₂ O ₃ content in the aluminum sprayed electrode is 10 wt% or less. Resistor.