JPH0141006B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrical device that prevents an adverse effect on the surrounding area due to a rise in temperature when an excessive current flows through an overvoltage limiting element.

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 T ₁ , T ₂ ,
T ₃ is protected.

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

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 9 such as solder is brought into contact with a current carrying body 2 consisting of an overvoltage limiting element such as a zinc oxide type arrester, and a pair of electrodes 12,1
The current-carrying body 2 and the low-melting point metal 9 are electrically connected in series between 3, pressed against one electrode 12 by a spring 14, and connected to the other electrode 13 by a shunt 15. Both current-carrying parts 12 facing each other are connected so that both current-carrying parts 12a and 13a are electrically connected.
a, 13a are arranged below the low melting point metal 9.

In the above configuration, when an excessive current flows through the current-carrying body 2, the electrode 12 → the current-carrying body 2 → the low melting point metal 9 →
It passes through the shunt 15→electrode 13 circuit. As a result, the temperature of the current-carrying body 2 increases, so that the low-melting point metal 9 melts and falls between the current-carrying parts 12a and 13a, thereby electrically connecting the electrodes 12 and 13.
Therefore, the current flowing through the current-carrying body 2 flows through the low-melting point metal 9 that has fallen between the current-carrying parts 12a and 13a, so that overheating of the current-carrying body 2 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, but the area where the current is concentrated will Therefore, since the amount of melting of the low-melting point metal is different, there is a drawback that the connection between the two current-carrying parts is unstable.

This invention was made to solve the above-mentioned drawbacks, and by arranging a heat transfer body to which a low melting point metal is fixed in contact with a current carrying body, a large amount of the low melting point metal can be melted. Provide electrical equipment.

The figures will be explained below. In Figure 3,
1 is an insulating cylinder; 2 is a current-carrying body consisting of an overvoltage limiting element such as a zinc oxide element disposed in the insulating cylinder 1;
3 and 4 are first heat transfer plates that are in contact with each end of the current carrying body 2; 5 and 6 are second heat transfer plates that are arranged at a predetermined distance from the first heat transfer plates 3 and 4; It is a board. In addition,
3 and 5 constitute a first heat transfer body 7, and 4 and 6 constitute a second heat transfer body 8, respectively. 9 is each heat exchanger plate 3 to 6
Low melting point metal such as solder fixed with 10,1
1 is a conductive plate in contact with a low melting point metal 9;
Reference numeral 12 denotes a first electrode fixed to one end of the insulating tube 1 and in contact with the plate 10, and has a first current-carrying portion 12a. A second electrode 13 is fixed to the other end of the insulating cylinder 1, and has a second current-carrying part 13a facing the first current-carrying part 12a. 14 is a spring that presses the current-carrying body 2 against the first electrode 12 via the heat transfer bodies 7, 8 and plates 10, 11;
This is a shunt connected to the electrode 13 of.

In the above configuration, when an excessive current flows through the current carrying body 2 and the temperature rises, the low melting point metal 9 is averaged and heated via the first heat exchanger plates 3, 4 and the second heat exchanger plates 5, 6. Ru. Therefore, a large amount of low melting point metal 9
melt and fall almost simultaneously. For this reason,
Since the low melting point metal 9 melts and falls almost simultaneously, the space between the current carrying parts 12a and 13a is filled with a large amount of the low melting point metal 9, so that a sufficient current carrying capacity can be ensured.

FIG. 4 shows another embodiment of the invention. In the figure, a current carrying body 2 is placed between both electrodes 12 and 13.
The heat transfer body 8 disposed between the current carrying body 2 and the electrode 13 is integrated with the electrode 13 through a plurality of heat transfer paths 8a with good heat conduction. A low melting point metal 9 is fixed to a portion surrounded by the heat transfer body 8 and the electrode 13. As a result, the heat generated in the current-carrying body 2 is quickly transferred to the low-melting point metal 9 over a wide range via the heat transfer path 8a, so that a large amount of the low-melting point metal is melted.

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, by bringing the heat transfer body to which the low melting point metal is fixed into contact with the current carrying body, the low melting point metal is heated evenly as a whole, so that a large amount of the low melting point metal melts almost simultaneously. Thus, sufficient current carrying capacity between both electrodes 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, FIG. 3 is a cross-sectional view of one embodiment of the present invention, and FIG. FIG. In the figure, 2 is a current carrying body;
7 and 8 are heat transfer bodies, and 3 is a low melting point metal. Note that the same reference numerals in each figure indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] 1 A pair of electrodes are connected to both ends of a current carrying body, and a low melting point metal is melted by a temperature rise when a current of a predetermined value or more flows through the current carrying body, and the low melting point metal is melted. An electrical device for electrically connecting the two electrodes, characterized in that a heat transfer body to which the low melting point metal is fixed and is in contact with at least one of the electrodes is brought into contact with the current carrying body. 2. The electrical device according to claim 1, wherein the heat transfer body is composed of heat transfer plates arranged alternately with low melting point metals. 3. The electrical device according to claim 1, wherein the heat transfer body has a fin-like structure having a heat transfer path integrated with the electrode.