JPS60258905A - Electric device - 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] [Technical Field of the Invention] The present invention relates to an electrical device, and particularly to an electrical device equipped with an overvoltage limiting element such as an arrester, which is designed to prevent the damage of the overvoltage limiting element from damaging the surrounding area. The invention relates to electrical equipment.

[Prior art]

Generally, in a high voltage power converter using a thyristor, the number of elements connected in series is determined in consideration of the normal operating voltage. Sporadically applied lightning impulses, switching surges, etc. are limited to a predetermined voltage by arresters.

In the conventional type, as shown in Fig. 1, each thyristor element 'I', 'r, T, K, arrester A, A,
, A.

and snubber circuits S, , S, , S, are connected in parallel.

In this case, even if an overvoltage such as a lightning impulse is applied from the outside to each thyristor element T, TJ, T,
Since only a limited voltage vM is applied by the arresters A, , A, , Aj and the snubber circuits S, , S, , S, connected in parallel, each thyristor cord T, ,
T,, Tj are protected.

However, when a conduction command is issued to each thyristor element T, T, T, if only the thyrisk element T does not conduct due to a failure in the ignition circuit, the other thyristors except for thyristor element T7 A load current determined by external circuit conditions is forced to flow through the arrester A, which is conductive and connected in parallel with the thyristor element T7, and its terminal voltage is a value determined by the voltage-current characteristics of the arrester A7. becomes.

Typically, the overvoltage limiting element will eventually fail because the arrester does not have the ability to carry excessive currents such as the load current for long periods of time.

At that time, the flying fragments may damage surrounding components, and continuous arcing may have an adverse effect on the power converter, which may destroy the overvoltage limiting element or immediately disconnect both ends of the arrester. A structure configured to short-circuit I was proposed.

7 There is.

That is, an arrester (electrical device) configured like this
As shown in FIG. 2, a low melting point metal such as solder is brought into contact with an overvoltage limiting element such as a zinc oxide type arrester, and a pair of electrodes 3. The overvoltage limiting element l and the low melting point metal are electrically connected in series between the springs! is pressed against one electrode J, connected to the other electrode y through a shunt 6, and both electrodes 3. The current-carrying portion J is placed below the low-melting point metal so that the current-carrying portions Ja and lIa of the
a, 4ta are arranged facing each other. 7 is electrode 3.4I
It is an insulating container that holds.

In the electrical device configured in this manner, when an excessive current flows through the overvoltage limiting element l, it passes through the circuit of electrode 3 -> overvoltage limiting element/ -> low melting point metal -> shunt 6 -> electrode DA. As a result, when the overvoltage limiting element l breaks down,
Arc heat causes the low melting point metal to melt and cause both current-carrying parts to melt.
? It falls between a and lIa, and both electrodes 3 and da are electrically connected.

Therefore, the current flowing through the overvoltage limiting element/ is t
Since it flows through the low melting point metal that has fallen between the IT part, 7a and 4'a, it is possible to eliminate the negative impact on the surrounding area caused by (3) destruction of the overvoltage limiting element 1.

However, if the amount of melted low melting point metal is small or if the contact with the electrode is poor, the short circuit formed by the low melting point metal will have a considerably high resistance value.
Therefore, the short circuit generates heat due to the load current that subsequently flows continuously.

According to our experience, it has been confirmed that the temperature rise in the short circuit sometimes reaches close to the melting point of the low melting point metal. Considering the normal surge handling of the voltage limiting element, the melting point of the low melting point metal cannot be set too low, so the temperature rise value of the short circuit is generally close to the maximum of /30°C.

It is clear that such a temperature rise has an adverse effect on the thyristor, overvoltage limiting element, snubber circuit components, etc. within the power converter.

In conventional electric devices such as those described above, in order to form a short-circuit path with a low resistance value, first of all it is necessary to instantaneously melt a large amount of a low-melting point alloy, but when the load current is small, This is difficult.

(da) In other words, in the process of temperature rise due to the load current of the overvoltage limiting element, the moment a short circuit is formed by the molten metal, even if it is only a small amount, the temperature rise of the element stops, and from then on, the temperature of the element stops rising. This is because the metal stops melting. Second, in order to reduce the contact resistance between the low-melting point metal and the electrode, it is necessary for the molten metal to become familiar with the electrode. Generally worse in different cases.

[Summary of the invention]

The present invention was made in view of the above-mentioned drawbacks of conventional electrical devices, and an object of the present invention is to provide an electrical device that can prevent damage to the surrounding area due to destruction of the overvoltage limiting element. By providing an electrode in which a liquid conductor is wrapped in a low-melting metal film with K and 5 properties at both ends, and pressing the electrode tightly against the overvoltage limiting element using a spring so as to face it, the resistance value can be maintained even when the load current is small. The present invention provides an electrical device that forms an extremely small short circuit.

[Embodiments of the invention]

Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

As shown in FIG. 3, electrodes are provided at both ends of an overvoltage limiting element l such as a zinc oxide element, and the electrodes are tightly pressed against the overvoltage limiting element l by a spring 5.

6 is a shunt that constitutes an energization path. These internal parts are housed in an insulating container, and g is a metal lid attached to both sides of the container. The electrode is composed of a film of a low melting point metal having a pentate property, and this film is usually manufactured by press working or the like. Specific examples of this low melting point metal include SK-alloy (manufactured by Sumitomo Metal Mining). There is mercury and liquid inside the low melting point metal film of the electrode.
A liquid conductive medium lθ such as a low melting point alloy that liquefies at about 20°C is sealed. Between the electrode D on the side closer to the spring j and the spring 5, there is a plug 1V-)/ which plays the role of preventing deformation of the electrode by applying spring pressure evenly to the electrode D.
/ Ka, wa, work. □2. Contact parts that protrude from each other towards the electrodes facing each other? It has a.

Next, the operation will be explained.

In the state shown in FIG. 3, if an excessive current exceeding a predetermined value flows through the overvoltage limiting element/, the overvoltage limiting element// will be destroyed and an arc will occur. The arc melts the low melting point metal film of the electrode t and forms a short circuit between the contact portions qa at the lower part of the electrodes. At the same time, the liquid conductive medium 10 sealed inside the electrode flows out from the fused portion of the low melting point metal film due to the pressure on the left side of the spring and accumulates between the contact portions 9a, forming a short circuit path with extremely low resistance. Finally, the electrode plate deforms as shown in FIG. 9 due to the splashing pressure by releasing the internal liquid conductive medium.

Here, the amount of contraction of the electrode is determined in advance by the liquid conductive medium 1
If the opposing electrodes are set to come into contact with each other at the contact portion 9a when zero is emitted, the short circuit can be made more complete. In another embodiment, when the electrodes form a short circuit by contacting the contact portions 9a, the liquid conductive medium 10 may be replaced by another fluid medium, such as air or a conductive compound (7). It is possible.

[Effects of the Invention] As described above, according to the present invention, the short circuit is triggered by the arc energy at the time of destruction of the overvoltage limiting element.
Since it is formed by extruding a liquid conductive medium or a fluid medium using splash pressure, a short circuit with an extremely small resistance value can be formed even if the amount of melting of the low melting point metal film is small. Therefore, there is an effect that the overvoltage limiting element will not explode and scatter and cause any damage to the surrounding area due to destruction.

[Brief explanation of drawings]

FIG. 1 is a wiring diagram showing the configuration of a power conversion device, FIG. 2 is a sectional view showing a conventional electrical device, FIG. 3 is a sectional view showing an embodiment of the electrical device according to the present invention, and FIG. FIG. 4 is a cross-sectional view showing the state of the short-circuiting device of FIG. 3 at the end of its operation; l...Overvoltage limiting element, c...Low melting point metal, 3゜l...
Electrode, S... Spring, 6... Shunt, 7... Insulating container, G... Metal lid, ? ...electrode, (za) 9a...contact part, lθ...liquid S electric medium, /l...plate. Note that the same reference numerals in each figure indicate the same or corresponding parts. Procedural amendment “Spontaneous” 952/1980 Mr. Commissioner of the Patent Office 1, Indication of the case Showa j? Patent application No. 1 Jt: It No. 2, Name of the invention Electrical device 3, Name of the person making the amendment Representative Kata Yuhito Section 4, Name of the agent Format ■ Examination content of the amendment l) Specification No.! "Experimental results" in the row of the page number is "Experimental results"
I am corrected. f) In the same paragraph, in lines 9 and 10 of the page, ``Therefore, overvoltage... has an effect'' is corrected to ``Therefore, the heat generated in the short circuit due to the load current has an adverse effect on surrounding components, etc.''.

Claims (1)

[Claims] (1) An electrical device comprising an overvoltage limiting element and a pair of electrodes connected to both ends of the overvoltage limiting element, in which an electrical short circuit is formed between the two electrodes when the overvoltage limiting element is destroyed, An electrical device characterized in that the electrode is formed of a flexible, low-melting metal film containing a liquid conductive medium, and includes springs that press the electrode into contact with both ends of the overvoltage limiting element. (v) The electrode is formed of a flexible, low-melting metal film that encloses a fluid medium, and is deformed by splash pressure when the fluid medium is released from the melting hole of the electrode due to arc heat when the overvoltage limiting element breaks. 2. The electrical device according to claim 1, further comprising contact portions that contact each other to form a short circuit.