JPS5928596Y2 - electrical equipment - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an electrical device that prevents an adverse effect on the surrounding area due to a temperature rise 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 the arrester.

As shown in FIG. 1, the conventional type has each thyristor element T, T2. Arrester A l, A2 at T3. A
3 and snubber circuit S1. S2. S3 are connected in parallel.

In this case, each thyristor element T1. T2. Even when an overvoltage such as a lightning impulse is applied from the outside to T3, the arresters A, A2, . A3 and snubber circuit S1. S2. S3 applies a limited voltage VML to each thyristor element TI.

T2. T3 is protected.

However, each thyristor Tl, T2 . When a conduction command is issued to T3, if only thyristor element T1 does not conduct due to a failure in the ignition circuit, the other thyristors except thyristor element T1 become conductive, and the arrester A1 connected in parallel with thyristor element T1 becomes conductive. The load current determined by the external circuit conditions is forced to flow, and the terminal voltage is the arrester A0.
The value is determined by the voltage-current characteristics of

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.

If it overheats and mechanically breaks down, the surrounding area may be damaged by flying fragments. Therefore, as shown in Figure 2, if an excessive current flows through the arrester, connect both ends of the arrester electrically. A configuration is proposed.

That is, in FIG. 2, a low melting point metal 3 such as solder is brought into contact with an overvoltage limiting element 1 such as a zinc oxide type arrester,
Overvoltage limiting element 1 and low melting point metal 3 between a pair of electrodes 4 and 5
are electrically connected in series, one electrode 4 is pressed by a spring 7 through a plate 9, and the other electrode 5 is connected to a shunt 2.
and connect both current-carrying parts 4a, 5a with molten low-melting point metal 3.
Both current-carrying parts 4a facing each other so that they are electrically connected to each other,
5a is arranged below the low melting point metal 3.

In the above configuration, when excessive current flows through the overvoltage limiting element 1, electrode 4 → overvoltage limiting element 1 → low melting point metal 3 →
Passes through the circuit of shunt 2 → electrode 5.

This causes the temperature of the overvoltage limiting element 1 to rise, so
The low melting point metal 3 melts and falls between the two current-carrying parts 4a, 5a, and the two electrodes 4, 5 are electrically connected.

Therefore, the current flowing through the overvoltage limiting element 1 flows between the two current-carrying parts 4 a and 5 a via the fallen low melting point metal 3, so that overheating of the overvoltage limiting element 1 can be suppressed.

However, even if the molten low-melting point metal 3 falls onto both current-carrying parts, since both current-carrying parts are metal surfaces, there is a drawback that the low-melting-point metal is difficult to adhere to.

In addition, the arc running on the surface of the overvoltage limiting element causes a film to adhere to the surfaces of both current-carrying parts that makes it difficult for current to flow, and there is a drawback that it takes a long time for the low-melting point metal to stick tightly and short-circuit.

The present invention provides an electric device in which a through-hole is provided in the overvoltage limiting element, and the low melting point metal is surrounded by the electrode and the overvoltage limiting element, thereby allowing a large amount of the low melting point metal to be transferred between the two electrodes.

The figures will be explained below.

In FIG. 3, reference numeral 1 denotes a current-carrying body made of an overvoltage limiting element such as a zinc oxide element, and has a through hole 1a.

2 is a shunt, 3 is a low melting point metal such as solder that is in close contact with the overvoltage limiting element 1, and 4 is a first shunt that is in close contact with the other end of the current carrying body 1.
, and 5 is the second electrode.

Reference numeral 6 denotes an insulating cylinder in which the current-carrying body 1 is housed and both electrodes 4 and 5 are held.

A spring 7 presses the current-carrying body 1 against the first electrode 4.

8 is a conductive guide that surrounds the low melting point metal 3, and surrounds the low melting point metal 3 in cooperation with the current carrying body 1.

Next, the operation will be explained.

In FIG. 3, when an excessive current flows through the current carrying body 1, the low melting point metal 3 is overheated and melted, and enters the through hole 1a of the weekly holiday 1, thereby electrically connecting the electrodes 4 and 5. , ensuring current carrying capacity between both electrodes 4 and 5.

According to this invention, by providing a conductive guide that surrounds the low-melting point metal, the low-melting point metal melted by overheating always enters the through hole of the current carrying body and can short-circuit both electrodes of the overvoltage limiting element.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a power conversion device, FIG. 2 is a sectional view showing a conventional electric device, and FIG. 3 is a sectional view showing an embodiment of the present invention. 1 is a current carrying body, 1a is a through hole, 1 is an overvoltage limiting element, 2 is a shunt, 3 is a low melting point metal, 4 and 5 are electrodes, and 8 is a guide. Note that the same reference numerals in each figure indicate the same or equivalent parts.

Claims (1)

[Scope of utility model registration request] A low melting point metal is brought into close contact with both ends of the current carrying body, electrodes are connected to each of the low melting point metals, and the two electrodes are short-circuited by the molten low melting point metal, in which the current carrying body is connected between both ends. The conductive guide has a through hole passing through the conductive body and is in close contact with the current carrying body and connected to each of the electrodes, and the current carrying body cooperates with the conductive guide to surround the low melting point metal. An electrical device featuring: