JPS589566B2 - Atsuyoku Atsouchi - Google Patents

Description

[Detailed description of the invention] The present invention relates to a varistor type voltage surge protection device.

More specifically, the present invention relates to a multi-terminal polycrystalline varisque device for providing protection against transient voltages in multiphase electrical circuits.

This invention is related to the invention described in US Pat. No. 3,693,053, issued September 19, 1972.

The basic polycrystalline varistor device currently manufactured consists of a sintered ceramic disk containing zinc oxide as the main component and a number of minor components selected from the group consisting of other metal oxides as well as halides. .

Electrodes are applied to each of the opposing main surfaces of the sintered disk, and a conductive wire is attached to each electrode to form a two-terminal varistor device.

It is common to encapsulate this device in a plastic material.

The aforementioned U.S. patent describes a multi-terminal metal oxide varisk multiphase transient voltage suppression device in which a plurality of protrusions are provided on a sintered body made of polycrystalline balisk material, and an electrode is applied to the main surface of each protrusion. Are listed.

A feature of this invention is that it can be manufactured inexpensively and efficiently using production equipment currently used for manufacturing two-terminal varistor devices as a multi-terminal polycrystalline varistor device that suppresses voltage surges in a multi-phase electric circuit. It is an object of the present invention to provide a varistor device having a substantially disk shape so that it is possible to do so.

Another object of the invention is that all the electrical conductors coming out of it are mounted in the same plane (this makes this type of multi-terminal varistor device easy and efficient to install in electrical equipment). The goal is to provide the following.

Another object of the invention is that it is of simple and compact form so that electrical equipment can be easily and efficiently installed, yet encapsulated to prevent unwanted electrical contact. An object of the present invention is to provide a terminal varistor device.

Briefly, in one embodiment of the present invention, a disk of polycrystalline balrisk material having a pair of opposing major surfaces is provided with a plurality of grooves on one major surface, and a plurality of grooves between the grooves. Limited land.

A plurality of electrodes are placed on the land, and a conductive wire is provided to connect the electrodes to an electric circuit.

An electrode is provided on the opposite side of the disk, i.e. on the non-grooved side, so that when a voltage exceeding the balisk voltage of the device appears between the lines connected to any two conductors of the device, this electrode It acts to conduct current. The novel features of this invention are:
While particularly pointed out in the claims, the invention, as well as other objects and advantages, will be better understood from the following description.

FIG. 1 is a plan view of a four-terminal varistor device according to a first embodiment of the present invention, which is composed of a disc 10 made of polycrystalline varistor material.

From the surface of the disk 10, a portion of its thickness t is broken into a groove 11.
12 is growing.

The grooves 11, 12 may be formed by cutting the finished sintered disk, or they may be formed by pressing the disk 10 using a ram with a cross-shaped projection.

When the shape is simple, the polycrystalline varistor has excellent uniformity of characteristics as a varistor, so a cutting knife is preferable for large-sized, high-power devices.

In the case of a small device, it is economical and preferable to form the grooves 11 and 12 in the disk by pressing, from the point of view of mass production.

Even in the case of small, low-power devices, it may be economically advantageous to form the grooves 11, 12 by cutting operations when only small quantities are produced.

In this case, a portion of the disk pressed in a production operation for making two-terminal balisk devices can be taken and grooved to form relatively small quantities of multi-terminal devices.

Lands 13, 14, 15, 16 are formed between the grooves 11.12.

Electrodes 17, 18 are provided on lands 13, 14, 15, and 16, respectively.
, 19, 20 apply.

This electrode can be provided by applying a conductive material to the top surface of the land, for example by painting, plating, sputtering or printing.

Conductive wires 21, 22, 23, and 24 are attached to each electrode, respectively.

This is advantageously mounted by soldering. Groove 11.
12 extends over the surface E of the disc 10 of the varistor, and the electrodes 17,
18, 19, and 20 are electrically isolated.

Under normal steady-state operating conditions, the resistance of the varistor material is extremely high, on the order of several thousand megohms, and the disc 1 between the electrodes is
At zero, almost no current flows.

However, if this varistor voltage is exceeded due to a transient condition,
The varistor material has a very small resistance of less than 1 ohm, and transient energy is split through the varistor material, protecting the circuitry to which it is connected.

The varistor voltage of the device is a function of the composition of the varistor material as well as the distance between the electrodes.

The grooves 11.12 serve to ensure that the varistor current passes within the bulk of the disk 10 and not through the surface between the electrodes.

Figure 2 is a side view of the multi-terminal polycrystalline varistor shown in Figure 1.
The disk 10, the lands 15 and 16 sandwiching the groove 11, and the electrodes 19 and 20 provided thereon are shown in the same manner as in FIG.

FIG. 2 further shows the electrode 25 disposed on the opposite side of the disk 10, ie, on the non-grooved side, and illustrates the effect of the groove 11 in preventing surface conductive paths between the electrodes 19, 20. There is.

Since the varistor voltage of a varistor is a function of the distance between the electrodes, and no current flows through a varistor in parallel with a varistor with a lower varistor voltage, the dimensions of the groove 11 are:
The surface conduction path between electrodes 19, 20 is chosen to be longer than the conduction path through the bulk of the varistor, so that the varistor voltage is higher.

For example, in the varistor device of the present invention used in a three-phase four-wire electric circuit, the sum of the lengths of surfaces 11a, 1lb and 11c is equal to or greater than 2.3 times the thickness of disk 10. are selected as such.

For this reason, when a voltage spike exceeding the varistor voltage of the device occurs between electrodes 19 and 20,
through the thickness of the disk 10 to reach the electrodes 25, which are again connected to the disk 10.
The conductive path through the thickness to the electrode 20 is created in preference to the conductive path between the electrodes 19, 20 across the surface of the device.

FIG. 2 shows in cross-section the multiterminal polycrystalline varistor device of the present invention encapsulated in a plastic material 26.

Electrical leads 21-24 are threaded through the encapsulating material 26 so that they can be connected to the electrical circuit to be protected.

Encapsulation material 26 provides the usual mechanical protection for the device of the invention and prevents accidental electrical contact from being made to electrode 25.

Therefore, by using the encapsulating material 26, the multi-terminal polycrystalline varistor device of the present invention can be installed in an electrical device without having to take care to avoid electrical contact with the electrodes 25. ;Easy installation.

The function of the electrodes 25 in the multi-terminal polycrystalline varistor device of this invention is to set the varistor voltage of the device, which is taken as twice the thickness of the disk, and to ensure that the conductive path of the varistor is connected to the electrodes. 17, 18, 19, 20 to ensure that the bulk passage is defined by the areas 17, 18, 19, 20.

[Brief explanation of drawings]

FIG. 1 is a plan view of a multi-terminal polycrystalline varistor device according to an embodiment of the present invention, and FIG. 2 is a side view of the multi-terminal polycrystalline varistor device of FIG. 1, showing the encapsulating material in cross section. be. Explanation of main symbols, 10: Varistor material disc, 11, 1
2: Groove, 13, 14, 15. 16: Land, 17, 18
, 19, 20: electrode, 21, 22, 23. 24: conducting wire,
25: Electrode on the second surface.

Claims (1)

[Claims] 1 a disk of polycrystalline varistor material having a pair of opposing surfaces, a plurality of grooves extending from a first side of the disk over a portion of the thickness of the disk; A multiphase transient voltage suppression device 2 comprising a plurality of electrodes arranged on a first surface, means for connecting to a plurality of electrode circuits, and an electrode arranged on a second surface. In the described multiphase transient voltage suppression device, each groove has two edges on said first surface and at least one surface between said edges, and said groove has at least one surface between said edges; A multiphase transient voltage suppression device whose shortest distance is greater than the thickness of the disk.