JP2676955B2 - Load switch with fuse - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a fuse with which a tripping mechanism of a load switch is mechanically tripped by fusing action of a fuse to open an electrode of the switch. Regarding load switch.

[Conventional technology]

As a load switch used for a distribution transformer or the like, a load switch with a fuse in which a power switch such as a current limiting fuse is combined with the load switch has been conventionally known, and the fuse has a blowout indicating pin. The same applicant used a device configured to mechanically trip the trip mechanism of the load switch by the action of the fusing indicator pin protruding from the fuse body when the fuse blows due to a fault current. It has already been proposed as Japanese Patent Publication No. 63-40346.

In this case, the fuse normally avoids unnecessary fusing due to inrush current of the load, etc., and in order to cut off the current by blowing when the fault current is applied, the rated current of the fuse is usually about 2 to 3 times the load current. It has been selected.

[Problems to be solved by the invention]

By the way, depending on the power circuit, not only the fault current,
In many cases, overload protection is required even when an overload current of about twice the normal load flows. However, in the above-described load switching with a fuse, the fuse does not blow at an overload current of about twice the normal load (the minimum blowing current of the fuse is about twice the rated current). Therefore, in the past, the current situation is to equip the load switch with an additional device that electrically trips the trip mechanism of the load switch by combining a current transformer and an overcurrent relay separately from the fuse. Is. However, additionally installing a current transformer and an overcurrent relay for overload protection causes a large increase in the cost of the load switch.

The present invention has been made in view of the above points, and by improving a connecting component between a blowout indicating pin of a fuse and a trip mechanism of a load switch, an additional device such as a current transformer or an overcurrent relay can be provided. An object of the present invention is to provide a load switch with a fuse capable of performing overload protection without needing it.

[Means for solving the problem]

In order to solve the above-mentioned problems, in a load switch with a fuse of the present invention, a V-shaped swing interposed for transmitting a force between the blow-off indicating pin of the fuse and the operation rod of the tripping mechanism. The lever is made of shape memory alloy,
One end of this rocking lever is placed in thermal contact with the end surface of the fuse cap, and when an overload current lower than the fuse blowing current is applied, the deformation force of the rocking lever itself due to the shape memory effect causes the load switch The trip mechanism shall be configured to trip.

[Action]

In the above structure, the V-shaped swing lever having the center as the swing fulcrum is made of a bidirectional shape memory alloy,
The shape is memorized in advance so that when it is heated from room temperature to high temperature, the lever itself is deformed by the transformation due to the shape memory effect so as to open its V-shaped angle, and when it is lowered to room temperature, it returns to the original shape again. Also, the transformation start temperature to the high temperature side is set in correspondence with the rising temperature accompanying the energization of the overload current.

As a result, the temperature of the fuse rises when the overload current is applied, and when the heat is transferred to the rocking lever through the cap of the fuse, the rocking lever itself deforms in the direction of opening the V-shape, and the deformation force opens and closes. Trip the trip mechanism of the vessel. When the temperature drops to room temperature after the current is cut off, the rocking lever returns to its original shape. On the other hand, if the fuse blows due to a fault current, the swing lever swings by the protruding action of the blown indicator pin, similar to the conventional load switch with a fuse, causing the trip mechanism of the switch to trip and the electrode to open. Open the contact. That is, without additionally equipping an electrical trip device such as a current transformer or an overcurrent protection relay,
The overload protection function can be given to the load switch by the deformation operation of the swing lever itself made of shape memory alloy.

〔Example〕

FIG. 1 is a configuration diagram of an embodiment of the present invention, and FIG. 2 is an operation explanatory diagram of a shape memory effect with respect to a swing lever in FIG.

First, the overall structure of a load switch with a fuse is described in FIG. In the figure, 1 is a switch base plate, 2 is a support insulator, 3 and 4 are terminal fittings provided on each insulator 2, 5 is a fixed electrode connected to one terminal fitting 3, 6 is one end of the other insulator 2
A fuse holder which is hinged to the fuse holder, 7 is a fuse with a built-in blowout indication pin mounted on the fuse holder 6, 8 and 9 are contacts that are joined to both end caps 7a of the fuse 7, and 10 is a contact with the contact 9 and is fixed as described above. A movable electrode that contacts the electrode 5 and an arc extinguishing chamber 11. On the other hand, the switch tripping mechanism for opening the movable electrode 10 includes a closing operation lever 12 of the switch, one end of which is hinged to the base plate 1, and the fuse holder 6 through the crank of the lever 12 shaft. A drive arm 13 that is connected to the drive arm 13, a spring 14 that projects the drive arm 13 to the left and urges it, a latch mechanism 15 that locks and locks the closing operation lever 12 in the closing position, and an insulator that releases the latch mechanism 15. Made operation rod 16, and the blowout indicating pin 7b and the operation rod 16 mounted on the tip of the fuse holder 6 and incorporated in the fuse 7.
It is composed of an assembly of a V-shaped swing lever 17 and the like interposed between and.

With such a structure, at the closing position of the switch shown by the solid line, an energizing circuit is formed between the terminal fittings 3 and 4 through the fixed electrode 5, the movable electrode 10, and the fuse 7 in series. Here, when the fuse 7 is blown by the fault current, the blow-off indicating pin 7b protruding outward from the end face of the cap pushes the swing lever 17. Therefore, the swing lever 17 swings clockwise around the swing fulcrum, and the operating rod 16 of the switch trip mechanism abutting on the other end of the lever is pushed rightward to release the latch mechanism 15. To do. As a result, the closing operation lever 12 becomes free, the drive arm 13 projects leftward by the bias of the spring 14, the fuse holder 6 rotates from the solid line position to the chain line position, and the movable electrode 10 is separated from the movable electrode 5. To open the contact. If the fuse 7 is replaced with a new one and the closing operation lever 12 is pulled back, the fuse holder 6 returns to the closing position and the fixed electrode 5 and the movable electrode 10 are closed, and at the same time the latch mechanism 15 is closed. Hangs on the locking pin,
The trip mechanism is locked in the loading position.

On the other hand, according to the present invention, the swing lever 17 is a lever made of a bidirectional shape memory alloy, and one end of the V-shaped lever is in heat transfer contact with the end surface of the cap 7a of the fuse 7. It is deployed to fit. Here, the rocking lever 17 made of a shape memory alloy maintains the shape of a solid line at room temperature (30 to 40 ° C.) as shown in FIG.
The shape is memorized in advance so that the lever itself is deformed into the shape of the chain line with the V-shaped angle widened by the transformation by the shape memory effect of being heated to (° C.).

Therefore, when the switch is closed, an overload current equal to or lower than the fault current (about 2 to 3 times the normal load current) is applied to heat the fuse 7, and the heat is transferred to the swing lever 17 through the fuse cap 7a. When heated, the rocking lever itself transforms to the high temperature side by the shape memory effect described above and deforms to the shape shown by the chain line in FIG. 2, and the deforming force causes the operating rod 16 of the switch trip mechanism to move to the right. Push out. As a result, the tripping mechanism trips as in the case of the fusing operation of the fuse 7, and the fixed electrode 5 and the movable electrode 10 of the switch are opened to cut off the overload current. When the temperature drops to room temperature after the current is cut off, the rocking lever 17 transforms to the low temperature side by the shape memory effect and returns to the shape shown by the solid line in FIG.

〔The invention's effect〕

Since the load switch with fuse according to the present invention is configured as described above, it has the following effects.

That is, a rocking lever made of a shape memory alloy is formed by placing one end in heat transfer contact with the fuse side cap so as to connect between the blowout indicating pin of the fuse and the operating rod of the switch trip mechanism. In addition, since the switch trip mechanism is mechanically tripped due to the deformation of the rocking lever itself caused by the overload current application and heating, the electrical configuration using the current transformer, overcurrent protection relay, etc. An overload protection function can be provided without additionally equipping a special trip device, and the cost can be significantly reduced as compared with the conventional load switch.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a load switch with a fuse according to an embodiment of the present invention, and FIG. 2 is an operation explanatory diagram of shape memory for a swing lever in FIG. In the figure, 5: fixed electrode, 7: fuse, 7a: fuse cap, 7b: fusing indicator pin, 10: movable electrode, 16: operation rod of tripping mechanism, 17: swing lever.

Claims (1)

(57) [Claims] 1. A load switch is combined with a fuse with a built-in blowout indication pin, and the tripping mechanism of the load breaker is mechanically tripped by the protruding action of the blowout indication pin when the fuse is blown to open the switch electrode. A load switch configured to be polarized, wherein a V-shaped rocking lever for transmitting a force is interposed between the blowout indicating pin of the fuse and the operation rod of the tripping mechanism. It is made of shape memory alloy, and one end of this rocking lever is placed in heat transfer contact with the end surface of the fuse cap.When an overload current lower than the fuse blowing current is applied, the rocking lever itself is shaped by the shape memory effect. A load switch with a fuse characterized in that the trip mechanism of the load switch is tripped by a deforming force.