JPH0141005B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention provides a method for when an excessive current flows through a current-carrying body.
The present invention relates to an electrical device that prevents the adverse effects of temperature rise on the surrounding area.

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 system, as shown in Figure 1, arresters A ₁ , A ₂ , A ₃ and snubber circuits S ₁ , S ₂ , S ₃ are connected in parallel to each thyristor element T ₁ , T ₂ , T ₃ . There is.
In this case, even if an overvoltage such as a lightning impulse is applied from the outside to each thyristor element T ₁ , T ₂ , T ₃ , the arresters A ₁ , A ₂ , A ₃ and the snubber circuit S ₁ , which are connected in parallel, Voltage limited by S ₂ and S ₃
Since only V _M is applied, each thyristor element T ₁ ,
T ₂ and T ₃ are protected.

However, when a conduction command is issued to each thyristor element T ₁ , T ₂ , T ₃ , if only thyristor element 1 fails to conduct due to a failure in the ignition circuit, all but thyristor element T ₁ and the other thyristor elements conducts,
A load current determined by external circuit conditions is forced to flow through the arrester A ₁ connected in parallel with the thyristor element T ₁ , and the terminal voltage thereof becomes a value determined by the voltage-current characteristics of the arrester A ₁ .

Usually, arresters do not have the ability to carry an excessive current such as the load current for a long period of time, so they overheat and have an adverse thermal effect on the surrounding area. Furthermore, if the arrester overheats and mechanically breaks down, flying debris may damage the surrounding area, so as shown in Figure 2, if an excessive current flows through the arrester,
Arresters configured to electrically connect both ends of the arrester have been proposed.

That is, in FIG. 2, a low melting point metal 3 such as solder is connected to an overvoltage limiting element 1 such as a zinc oxide type arrester.
The overvoltage limiting element 1 and the low melting point metal 3 are electrically connected in series between a pair of electrodes 5 and 6, and the spring 6 is pressed against one electrode 5, and the other electrode 6 is connected by a shunt 9. The opposing current-carrying parts 5a and 6a are arranged below the low-melting metal 3 so that the molten low-melting metal 3 electrically connects the two through-carrying parts 5a and 6a.

In the above configuration, when an excessive current flows through the overvoltage limiting element 1, the electrode 5→overvoltage limiting element 1→
It passes through a circuit of low melting point metal 3 → shunt 9 → electrode 6. As a result, the temperature of the overvoltage limiting element 1 rises, so that the low melting point metal 3 melts and both current-carrying parts 5
It falls between electrodes 5 and 6a, and both electrodes 5 and 6 are electrically connected. Therefore, the current flowing through the overvoltage limiting element 1 flows through the low melting point metal 3 that has fallen between the two current-carrying parts 5a and 6a, so that overheating of the overvoltage limiting element 1 can be suppressed.

However, if a part of the overvoltage limiting element electrically breaks down and excessive current concentrates there, the low melting point metal in the vicinity will instantly melt and fall.
Since the amount of melting of the low-melting point metal differs depending on the location where the current is concentrated, there is a drawback that the connection between the two current-carrying parts is unstable.

This invention was made in order to solve the above-mentioned drawbacks, and the overvoltage limiting element is housed in an insulating cylinder, so that when the overvoltage limiting element breaks down, foreign matter does not enter the current-carrying part, and the low-melting point metal melts and the current-carrying part does not melt. To provide an electrical device in which molten metal flows into a current-carrying part when the current-carrying part is connected, reducing contact resistance of the current-carrying part, and providing stable electrical connection of the current-carrying part.

The figures will be explained below. In Figure 3,
Reference numeral 1 denotes a current-carrying body made of an overvoltage limiting element such as a zinc oxide element, which is housed in an insulating cylinder 7, and one electrode of which is in electrical contact with the first electrode 5. A heat transfer plate 2 is closely attached to the other side of the current-carrying body 1, and is made of a material having good heat transfer and electrical conductivity. 3 is a low melting point metal such as solder that is closely adhered to the heat exchanger plate 2, 5a
1 is a first current-carrying portion of the first electrode 5, and 10 is a movable electrode having a second current-carrying portion 10a facing the first current-carrying portion 5a with a predetermined spacing therebetween. In addition, both current-carrying parts 5a and 10a, when the low melting point metal 3 is melted,
They are brought into contact by the pressure of the spring 8, and are electrically stably connected with low contact resistance due to the low melting point metal 3 flowing into the contact surface. 9 is a movable electrode 10 and an electrode plate 11
This is a shunt that electrically connects the two. 11 is the first
The first electrode plate 11a electrically connects the electrode and external electrical components, and the second electrode plate 11a electrically connects the movable electrode 10 and external electrical components via the shunt 9. Note that each current-carrying body is arranged between the first electrode plate 11 and the second electrode plate 11a.
Reference numeral 7a designates an insulating tube that accommodates each current-carrying body, and 12 and 13 designates a support and a nut for assembling the current-carrying body and the insulator.

Next, the operation will be explained. In Figure 3,
Even if an excessive current locally flows through the current-carrying body 1, the heat exchanger plate 2 is gradually heated. Therefore, the low melting point metal 3 melts almost simultaneously and the movable electrode 3
is moved in the direction of the current carrying body 1 by the pressure of the spring 9,
Both current-carrying parts 5a and 10a are in contact with each other. At this time, the molten low-melting point metal 3 flows into the connection surface between the two current-carrying parts 5a and 10a. As a result, both current-carrying parts 5
Low contact resistance between a and 10a ensures electrically stable current carrying capacity.

In the above example, the current-carrying body is an overvoltage limiting element such as a zinc oxide arrester, but the same effect can be expected if the current-carrying body is one that would cause excessive current to flow during an accident and cause overheating. be done.

According to this invention, the current-carrying body, which generates heat and is likely to break down, is housed in the heat exchanger plate and the insulator, so that when it breaks down, it does not mix into the contact surface as foreign matter, and low-melting point metals flow into the contact surface. , low contact resistance, electrical stability, and sufficient current carrying capacity can be ensured.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a power conversion device, FIG. 2 is a cross-sectional view of a conventional electric device, and FIG. 3 is a cross-sectional view of an embodiment of the present invention. In the figure, 1 is a current carrying body, 2 is a heat exchanger plate, 3 is a low melting point metal, 5 is a first electrode, and 10 is a movable electrode. Note that the same reference numerals in each figure indicate the same or equivalent parts.

Claims (1)

[Claims] 1 A current-carrying body and a low-melting point metal are placed in close contact with each other and electrically connected in series between a pair of electrodes having respective conducting portions facing each other at a predetermined interval, and the low-melting point metal is melted. Particularly, in the structure configured to short-circuit the two electrodes, the low melting point metal is disposed between one of the electrodes and the current carrying body, and one of the electrodes is directed toward the other electrode. An electric device characterized in that it is pressed by a spring and is moved from a predetermined position when the low-melting point metal melts, so that the current-carrying parts of the electrodes can come into contact with each other.