JPS587603Y2 - surge absorber - Google Patents

Description

[Detailed explanation of the idea] This invention relates to a surge absorber.

Ceramic varistors, such as varistors made mainly of zinc oxide, have better voltage-current characteristics than ever before, so they are connected in parallel with equipment to power lines and signal lines to protect equipment from lightning surge voltages. It is used extremely often.

FIG. 1 shows the voltage-current characteristics of this zinc oxide type varistor.

In the figure, A is a voltage-current characteristic curve, and a and b are voltages corresponding to the Zener voltage of a Zener diode, which are voltages at which electrical contact suddenly begins to flow, and are generally called varistor voltages.

Usually, the varistor voltage is set to a value higher than the peaks and waves of the circuit voltage, and the zinc oxide type varistor operates as an insulator with respect to the circuit voltage.

However, when a surge voltage that far exceeds the normal voltage enters, the zinc oxide varistor immediately exhibits a low resistance value, bypassing the surge current caused by the surge voltage, and increasing the voltage across the zinc oxide varistor. This is to suppress the

For this purpose, a surge absorber having the structure shown in FIG. 2 has been widely used.

In Fig. 2, 1 is a zinc oxide type varistor element with a disk shape, 2 and 3 are silver electrodes baked on both sides of the zinc oxide type varistor element 1, and 4 and 5 are electrodes 2 and 3, respectively. This is a soldered lead terminal.

Now, when a large surge current or a large surge current with a high wavefront severity flows into this surge absorber, the current flowing in the zinc oxide type varistor element 1 will be affected by the zinc oxide type varistor element 1 due to the skin effect, as shown in Figure 3. The current density at the circumferential portion of the element 1 (simply indicated by a broken line) becomes high, and conversely, the current density at the center of the zinc oxide type varistor element 1 becomes low.

When the current flows non-uniformly in this way, the surge resistance of the entire zinc oxide type varistor element 1 is determined by the surge resistance in the circumferential portion, and the greater the skin effect, the lower the surge resistance.

Furthermore, this phenomenon not only reduces the surge resistance that the zinc oxide type varistor originally has, but also increases the limiting voltage due to the increased current density on the circumference, impairing its characteristics as a surge absorber.

Therefore, surge absorbers have been proposed that aim to reduce such skin effects and improve surge absorption characteristics.

As shown in FIG. 4, this surge absorber includes a ring-shaped varistor 6, a first terminal 8 planted on an upper electrode 7 of the ring-shaped varistor 6, and a lower electrode 9 of the ring-shaped varistor 6.
A second terminal 11 projects upward through the ring hole 10.
It consists of.

In this case, the second terminal 11 is constructed such that the flat plate portion 11a that contacts the lower electrode 9 has appropriate mechanical strength.

In this surge absorber, the surge current flows from the first terminal 8 to the top electrode 7 to the ring-shaped varistor 6 to the bottom electrode 9 to the second terminal 11 as shown by arrow B, and from the first terminal 8 to the bottom electrode 9. The current flowing through the ring-shaped varistor 6 and the current flowing through the second terminal 11 are in substantially opposite directions, and the changes in the magnetic fields within the ring-shaped varistor 6 produced by each of them interfere with each other.

However, in this proposed example, since the first terminal 8 is formed only at one location in the circumferential direction of the upper surface electrode 7, the surge current flowing through the ring-shaped varistor 6 does not flow uniformly, and the skin effect is not reduced much. I can't.

Therefore, an object of this invention is to provide a surge absorber that can sufficiently reduce the skin effect and improve surge absorption characteristics.

An embodiment of this invention is shown in FIG.

That is, this surge absorber includes a ring-shaped varistor 6, a collar 8a is fixed to the upper surface electrode 7 of the non-long-type varistor 6 coaxially with the ring hole 10 of the ring-shaped varistor 6, and the collar 8a is attached to the inner peripheral edge of the collar 8a. A flat plate part 11a is fixed to the first terminal 8 with the pipe part 8b integrally planted thereon and the lower electrode 9 of the ring-shaped varistor 6, and a rod-shaped part 11b is planted in the center position of the upper surface of the flat plate part 11a. Shiko rod-shaped part 11a
and a second terminal 11 that penetrates the ring hole 10 and the pipe portion 8b and is exposed to the outside.

As a result of this configuration, the surge current flows uniformly through the ring-shaped varistor 6, and this current and the current flowing through the rod-shaped portion 11b almost completely cancel each other out, and the skin effect can be sufficiently reduced and the original surge resistance of the varistor can be reduced. characteristics and limiting voltage characteristics are obtained.

As a result, a larger surge withstand capacity can be obtained even with a varistor of the same size.

As described above, the surge absorber of this invention can reduce the skin effect and produce the following effects.

(1) Surge resistance is improved.

(2) The current density is reduced and the limiting voltage is lowered.

[Brief explanation of drawings]

Figure 1 is a varistor voltage-current characteristic diagram, Figure 2 is a side view of a conventional surge absorber, Figure 3 is an explanatory diagram to explain the shortcomings of the surge absorber in Figure 2, and Figure 4 is a proposal. FIG. 5 is a side sectional view of an embodiment of the invention. 6...Ring type varistor, 7...-1
Surface electrode, 8...First terminal, 8a...Brim part, 8b...Pipe part, 9...Bottom electrode, 10...・Ring hole, 11... Second terminal, 11 a... Flat plate part, 11 b...
...rod-shaped part.

Claims (1)

[Scope of utility model registration request] a ring-shaped varistor, a first terminal having a flange fixed to the upper electrode of the ring-shaped varistor coaxially with the ring hole of the ring-shaped varistor, and a pipe part integrally planted on the inner peripheral edge of the flange; A flat plate part is fixed to the lower electrode of the ring-shaped varistor, and a rod-shaped part is implanted at the center of the upper surface of the flat plate part, and this rod-shaped part penetrates the ring hole and the pipe part and is exposed to the outside as a second terminal. Surge absorber with.