JPS58225609A - Surge absorber - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a zinc oxide varistor (hereinafter referred to as a ceramic varistor) which has a large surge withstand capacity and an electrode plate that is in pressure contact with the ceramic varistor. The purpose is to measure each other.

Ceramic varistors mainly made of zinc oxide have a large lightning surge absorption capacity and excellent voltage-current characteristics, and are now being widely used in lightning arresters for power-related equipment in place of conventional SiC varistors.

This ceramic varistor usually has silver electrodes baked on both sides of the varistor element, which is shaped like a disk or cylinder.

The structure is such that electrodes are formed by notaricon, plating, plasma spraying, etc. of aluminum or the like, and an external electrode plate is pressed into contact with the electrodes for electrical connection. If the area of the electrodes attached to the element (or element area) is increased, the surge withstand capacity will also increase in proportion to this, and for devices used in power related equipment, the required surge withstand capacity is, for example, 140 KA. ,
Since it is 100 KA, many devices with an element diameter of 32 m or more are used.In surge absorbers with such a large withstand capacity, the characteristics of the ceramic varistor element as well as the structure of the external electrode connected to it are important. This is an important factor that affects its surge resistance. Normally, electrical connection to the ceramic varistor element is not made by press-contacting a metal external electrode plate as described above, but the press-contact state is important for lightning surge currents exceeding lloKA. That is, when the pressure contact with the varistor element is insufficient: 1. Arc is generated at the incomplete contact surface, and the arc gas tends to cause creeping of the ceramic varistor.

2. The electrode on the ceramic varistor element evaporates and disappears due to the above arc, and as a result, the surge current cannot be absorbed sufficiently and an even larger arc is generated.0) The electromagnetic repulsion force on the pressure welding surface increases, resulting in 1s. Condition worsens.

Deterioration phenomena such as these occur.

FIG. 1 shows a cross-sectional view of an example of a conventional ceramic varistor. In the figure, (1) is a disk-shaped ceramic varistor element, (2+, (2') are silver electrodes baked on both the front and back sides of element (1), and (3), (3') are silver type [ ij +2
1. (2') is a metal electrode plate, such as a copper plate, which is pressed into contact with a spring or the like (not shown). The problem here is the silver electrode (21, (2')) and the metal electrode plate (3), (3')
It is in a pressure-welded state. As shown in this example, the VC@ electrode and the copper plate do not closely fit each other, and sufficient planar contact cannot be expected, and even if there is an apparent planar contact, it is often actually a point contact at two or three points. FIG. 2 shows this state. L is the silver electrode (21 or metal electrode plate (3))
The pole on the surface is a gap created by a slight convexity,
Generally, this problem does not disappear even if the contact pressure is slightly increased. Such incomplete contact causes the aforementioned deterioration phenomenon, resulting in a decrease in surge resistance.

The present invention improves the pressure contact state between the electrode attached to such a varistor element and the external electrode plate that is in pressure contact with the electrode, and
This is intended to provide a large surge withstand capacity as a surge absorber.

Next, an embodiment of the present invention will be described with reference to FIGS. Fig. 4 is a sectional view of an electrode plate according to the present invention, and Fig. 4 is a sectional view of the electrode plate shown in Fig. 3 in pressure contact with an electrode (2) of a ceramic varistor element. In the present invention, the electrode (21) of the ceramic varistor element of the metal electrode plate (3)
The surface in contact with the aluminum plate is polished in advance by puff polishing with alumina or silicon carbide, and then a copper metallic layer (4) is applied to the aluminum plate. When the electrode plate has such a structure, slight irregularities on the surface of the electrode 1 (2) or the surface of the electrode plate (3) that are pressed against it are absorbed by the soft metal layer (4). , it is possible to achieve a sufficient pressure contact state and eliminate the occurrence of the above-mentioned undesirable deterioration phenomenon.

The above-mentioned aluminum or copper metal layer (4) is usually obtained by electrical spraying of the metal and has a thickness of 3.
It is about 0 to 60 μm.

In the above-described embodiments, although the electrode (21) was provided by baking silver, the same effect cannot be obtained when the electrode (2) is made by plating.

Moreover, even better characteristics can be obtained if the electrode (2) is made of aluminum metallicon.

Furthermore, in FIGS. 3 and 4, a ceramic varistor element (1
Although we have only given an example of the electrode plate (3) connected to one side of the A similar effect can be obtained.

As described above, according to the present invention, the metallicon (4) is applied to the pressure contact surface of the electrode plate (3) that is pressed against the electrode (21) of the ceramic varistor element. It is possible to create a tight pressure contact between the
Therefore, the generation of arc on the pressure contact surface is reduced, and the electrode on the ceramic varistor element is evaporated by the arc.
It has the effect of preventing the quenching from disappearing, reducing the electromagnetic repulsion between the pressure contact surfaces, and improving the surge resistance.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventional ceramic varistor, FIG. 2 is a partial sectional view for explaining its operation, and FIG. 5 is a sectional view of an electrode plate used in the surge absorber of the present invention. FIG. 4 is a sectional view of a main part of an embodiment of the present invention. (1) -- Ceramic varistor element, (211 (2
') - Electrode, (3>, (3')... Electrode plate, (
4)...Metallicon layer. Name of agent: Patent attorney Etsuji Yoshizaki

Claims (1)

[Claims] A surge absorber comprising an electrode plate provided on the surface of a ceramic varistor, and an electrode plate having a metallicon layer formed on the surface in contact with the electrode.