JPS5832248Y2 - surge absorber - Google Patents

Description

[Detailed description of the invention] The present invention relates to the electrode shape of a surge absorber, and more specifically, the current flowing through the center of the varistor element is restricted, and the temperature distribution within the varistor element is uniformed by limiting heat generation in the center. This provides a surge absorber that is resistant to surge currents or continuously flowing low currents.

Conventionally, a varistor element has a structure as shown in Figure 1.
1 is a cylindrical (or disc-shaped) sintered body made of metal oxide such as zinc oxide, and 2 is a circular electrode formed on opposing end surfaces of this sintered body 1.

These elements are stacked and housed in an insulating case 3 as shown in FIG.

By the way, when a surge current flows through this varistor element, it generates heat due to the energy, and then gradually discharges and returns to its original temperature, but the degree of return varies greatly depending on each part of the element body.

That is, the surface portion A of the varistor element in FIG. 1 has good heat dissipation and is cooled relatively quickly, but the center portion B is slow.

For example, when a surge current with a certain interval continuously flows through the varistor element, the temperature of the center part B becomes higher and higher than that of the surface part A.

On the other hand, since the varistor element has large voltage nonlinearity and negative temperature characteristics, the rising voltage (operating voltage) at the central portion B decreases as the temperature rises, and the circuit voltage to which this varistor element is applied decreases. The leakage current suddenly flows into the center portion B, and the temperature of the center portion B increases, eventually leading to destruction.

Further, at this time, the above-mentioned phenomenon becomes more noticeable when heat is generated not only due to the surge current but also due to the application of a sustained overvoltage higher than the rated value to the varistor element.

Further, in the case of a large varistor element, it is difficult to achieve uniform characteristics up to the center of the element, and when fired, the characteristics of the center may differ from those of other parts.

This is because the rising voltage per unit length is low and the characteristics are not of good quality, which has a negative effect on the characteristics as a varistor, causing surge current to concentrate, and as a result, the surge resistance does not increase considering the shape. There was a problem.

The present invention is intended to solve these conventional drawbacks, and an embodiment of the present invention will be described below with reference to FIGS. 3 and 4, with the same numbers assigned to the same parts as above.

As shown in FIG. 4, the varistor element 1' is housed in an insulating case 3 by pressure contact with a spring (not shown) via a metal annular electrode plate 4 as shown in FIG. 3. As shown in FIG.

In the surge absorber configured in this way, current caused by surge current and persistent overvoltage easily flows through the surface portion A of the element, and the current flowing through the central portion B is controlled, thereby reducing the local temperature of the central portion B. temperature rise is avoided and a more uniform temperature distribution is obtained.

This improves the resistance to surge currents as well as sustained currents.

Furthermore, even in the case of a large varistor element, by controlling the current flowing through the center, the influence of the recessive characteristics of the center can be reduced, and the surge resistance characteristics are improved.

FIG. 5 shows another embodiment of the present invention.

That is, an electrode plate 5 which is pot-shaped and has a through hole at its bottom is pressed against seven varistor elements by a spring 6.
As a result, the pressure contact portion to the element is annular, and the same effect as in the first embodiment can be obtained.

As detailed above, according to the present invention, the temperature distribution inside the element becomes more uniform, which improves the strength against surge currents and sustained currents. It becomes possible to reduce the influence of recessive characteristics in the parts, and it is possible to easily obtain a surge absorber with improved surge resistance.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a varistor element, Fig. 2 is a sectional view of a main part of a conventional surge absorber, Fig. 3 is a perspective view showing an example of an electrode constituting the surge absorber of the present invention, and Fig. 4 is a sectional view of a varistor element. A sectional view of a main part showing one embodiment of the surge absorber of the present invention, and FIG. 5 is a sectional view of a main part of another embodiment. 1'... Varistor element, 2... Electrode,
3... Insulating case, 4, 5... Metal electrode plate.

Claims (1)

[Scope of utility model registration request] In a surge absorber in which a metal electrode plate is pressed into contact with a varistor element having electrode portions on opposing planes of a disk or cylindrical sintered body and housed in an insulating case, the metal electrode plate is annular. Alternatively, a surge absorber characterized in that the pressure contact portion to the element is annular.