JPH0141007B2 - - 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 T ₁ , T ₂ , T ₃ , if only thyristor element T ₁ fails to conduct due to a failure in the ignition circuit, the other thyristor elements except thyristor element T ₁ 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 connected to an overvoltage limiting element 2 such as a zinc oxide type arrester.
The overvoltage limiting element 2 and the low melting point metal 9 are electrically connected in series between the pair of electrodes 4 and 6, and the spring 8 presses one electrode 4, and the other electrode 6 is connected to the shunt 10. Both the opposing current-carrying parts 4a, 6b are connected to the low-melting-point metal 9 so that both the current-carrying parts 4a, 6b are electrically connected by the molten low-melting-point metal 9.
It is located at the bottom of the .

In the above configuration, when excessive current flows through the overvoltage limiting element 2, the electrode 4→overvoltage limiting element 2→
It passes through a circuit of low melting point metal 9 → shunt 10 → electrode 6. As a result, the temperature of the overvoltage limiting element 2 increases, and the low melting point metal 9 melts, causing both current-carrying parts 4 to melt.
It falls between a and 6b, and both electrodes 4 and 6 are electrically connected. Therefore, the current flowing through the overvoltage limiting element 2 flows through the low melting point metal 9 that has fallen between the two current-carrying parts 4a and 6b, so that overheating of the overvoltage limiting element 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.
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 eliminate the above-mentioned drawbacks, and a pair of electrodes are brought into contact with each end of a current-carrying body such as an overvoltage limiting element, and each electrode is placed around the current-carrying body at a predetermined distance from the current-carrying body. To provide an electrical device in which a large amount of low melting point metal is melted by arranging the fixed low melting point metal.

The figures will be explained below. In Figure 3,
1 is an insulating tube, 2 is a current-carrying body made of an overvoltage limiting element such as a zinc oxide element arranged in the insulating tube 1, 3 is a first terminal metal that closes one end of the insulating tube 1, and 4 is a terminal whose one end is the first terminal metal. A first electrode that is in contact with the terminal metal 3 and whose other end is in contact with one end of the current-carrying body 2, and a first current-carrying electrode that extends in the axial direction of the insulating tube 1 at a predetermined distance from the current-carrying body 2. It has a portion 4a. 5 is a second terminal metal that closes the other end of the insulating tube 1 and has a cylindrical first sliding portion 5a that protrudes inward of the insulating tube 1 in the axial direction of the insulating tube 1; 6 protrudes from one end; A cylindrical second sliding part 6
A is a second electrode which is arranged to be slidable in the axial direction of the first sliding part 5a and the insulating cylinder 1, and whose other end is in contact with the other end of the current carrying body 2, and which is at a predetermined distance from the current carrying body 2. A second current-carrying portion 6b extending in the axial direction of the insulating cylinder 1 is opened. 7 is a contact having a plurality of contact parts arranged between both sliding parts 5a, 6a; 8 is a spring arranged between the second electrode 6 and the second terminal metal 5; 6 is pressed against the current-carrying body 2. 9
are each current-carrying part 4a, 6b of each electrode 4, 6 and current-carrying body 2
A low melting point metal is placed between the current carrying body 2 and a predetermined distance, and is fixed to each electrode 4, 6, respectively.

Next, the operation will be explained. In FIG. 3, when an excessive current flows through the current-carrying body 2, the temperature of the current-carrying body 2 rises, and heat is conducted to each electrode 4, 6. Each electrode 4,
6 conducts evenly and heats the low-melting point metal 9 evenly, so the low-melting point metal 9 melts almost simultaneously and falls between the two current-carrying parts 4a and 4b. As a result, a large amount of low-melting point metal 9 short-circuits both current-carrying parts 4a and 6b. Therefore, the current flows as follows: first terminal metal 3 → first electrode 4 → current carrying body 2 → second electrode 6 →
Since the current flows through the path from the contact 7 to the second terminal metal 5, the current in the current carrying body 2 is bypassed.

According to this invention, the heat generated in the current carrying body is transferred to the low melting point metal via the electrode in contact with the current carrying body, so that the low melting point metal is heated almost evenly and a large amount of the low melting point metal is melted. Therefore, ensure a short circuit between both current-carrying parts. Therefore, the excessive current flowing through the current-carrying body is bypassed, and an abnormal temperature rise of the current-carrying body can be prevented, thereby preventing an adverse effect on the surrounding area.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a power conversion device, FIG. 2 is a sectional view of a conventional electric device, and FIG. 3 is a sectional view showing an embodiment of the present invention. In the figure, 1 is an insulating cylinder, 2 is a current carrying body, 3 is a first terminal metal, 4 is a first electrode, 4a is a current carrying part, 5
is the second terminal metal, 5a is the first sliding part, 6 is the second
6a is a second sliding part, 6b is a second current-carrying part, 8 is a spring, and 9 is a low melting point metal. Note that the same reference numerals in each figure indicate the same or equivalent parts.

Claims (1)

[Claims] 1. An insulating cylinder, a current-carrying body housed in this insulating cylinder,
A first terminal metal that closes one end of the insulating cylinder, one end of which is in contact with the first terminal metal, the other end of which is in contact with one end of the current carrying body, and the insulating cylinder is spaced apart from the current carrying body by a predetermined distance. a first electrode having a first current-carrying portion extending in the axial direction; a cylindrical first electrode that closes the other end of the insulating cylinder and protrudes in the axial direction of the insulating cylinder; A second terminal metal having a sliding portion, a cylindrical second sliding portion protruding from one end is arranged to be slidable in the axial direction of the first sliding portion and the insulating cylinder, and the other end is a second electrode having a second current-carrying part that contacts the other end of the current-carrying body, extends in the axial direction of the insulating cylinder at a predetermined distance from the current-carrying body, and faces the first current-carrying part; a spring disposed between the second electrode and the second terminal metal and pressing the second electrode against the current carrying body; and a spring disposed between the second electrode and the second terminal metal; An electric device comprising a low melting point metal arranged at a predetermined distance from and fixed to each of the electrodes.