Electrical fuse with a fusing element

Abstract

Relates to an electric fuse, which includes a fuse element (2) that extends through a ceramic electrical insulating cylindrical housing (1). The housing is sealed and enclosed at each end by a conductive cap (3), and the fuse element (2) is electrically connected to the conductive cap. Thus, through simple and low-cost measures, it can be ensured that such a fuse can also be applied to a circuit with the same overall dimensions as a circuit protected by a common existing fuse at a voltage higher than the nominal voltage. However, in the case of an electrical overload, this fuse can still interrupt the circuit extending through it, thereby also avoiding mechanical damage or even destruction of the ceramic insulating housing (1), which would otherwise cause the generated electric arc to potentially expand from inside the housing (1) to the outside of the fuse.

Description

[0001] The present invention belongs to electricity, namely basic electrical components, and particularly to protective components in which an electric current flows through a part of fusible material and the interruption of the current due to an electrical overload is achieved by the fusing of this material. In particular, the present invention relates to the structural details of high-voltage fuses and thus belongs to the class H01H085 / 042 according to the International Patent Classification.

[0002] The present invention is based on the problem of how to improve an electrical fuse which generally includes a fusing element that extends through a ceramic electrical insulating cylindrical housing sealed and closed at each end by conductive caps, the fusing element being electrically connected to the conductive caps so that such a fuse can be applied to a circuit at a voltage higher than the nominal voltage, which can be protected by a common existing fuse with the same overall dimensions, but in the case of an electrical overload, this improved fuse should still be able to interrupt the circuit extending through it, thereby also avoiding mechanical damage or even destruction of the ceramic insulating housing, which could otherwise cause the resulting electric arc to expand from the inside of the housing to the outside of the fuse.

[0003] The electrical fuse with a fusing element according to the present invention is generally used in the field of high-voltage circuit protection, and in particular has recently been used in the DC circuits of photovoltaic power plants or similar high-voltage systems, where the voltage typically reaches about 1500 V and the current value is about 25 A or even 30 A sometimes. The applicable fuse is embedded in a suitable carrier and usually has to be replaceable, so the size of the fuse also has to be predefined in advance. The limitation of the size also results in the following condition, that is, which type of fuse should be used under a certain nominal voltage and current. However, this depends not only on the material, resistance and the area of its cross-section, but also on the process of fusing the fusing element. When interrupting the fusing element, the fusing element is heated to its fusing temperature, at which at least a part of the fusing element melts and is interrupted. Gas is also generated during this process, so the pressure inside the fuse may also increase significantly. Especially in DC circuits, it usually happens that an arc starts to burn between the two parts after the interruption of the fusing element, which may further complicate the situation. If the fuse housing is cracked or even broken, the situation will become extremely critical, and the arc may enter the surrounding environment freely, which will trigger a huge fire. Although the inside of the housing is usually filled with fireproof granular material, once the housing is broken, the fireproof granular material will spread out and be lost, so it will no longer help to extinguish the arc. The electrically insulating fuse housing is usually made of ceramic, and ceramic is fragile and may be immediately broken due to the sufficient increase in pressure inside the fuse. However, there is also a known fuse that finally eliminates the above situation by using a housing composed of a composite material or a hard plastic electrical insulating material. Another problem may occur in this case, which is related to the overheating and carbonization of this material at least on the inner surface of the fuse housing due to the burning of the arc. This carbonized surface of the material, which is initially non-conductive, gradually becomes conductive, which means that although the fusing element is interrupted, the fuse can still conduct current, and the overloaded circuit cannot be interrupted despite the presence of the fuse.

[0004] CN203398066U discloses an electrical fuse, which includes a cylindrical tubular housing made of an electrical insulating material, and the housing is sealed and closed at each of its ends with caps made of a conductive material and used to integrate the fuse into a disposable circuit. The uninterrupted fusing element is inserted through a channel inside the fuse between the said caps, and each end of the fusing element is electrically connected to the respective cap. Such a fusing element is a wire or strip made of a conductive material with a predetermined resistance and fusing temperature. In addition, the fusing element has a weak area, which is precisely manufactured and in this area the component should fuse within a relatively small area and under definite conditions. Therefore, after the fusing element fuses, the distance between the two remaining parts is relatively small, which may cause an arc to form and burn between them. To prevent the formation and extension of the arc when the fusing element is interrupted, the fusing element is surrounded by granular fireproof material (such as silica sand) inside the said housing.

[0005] In this case, each conductive cap is pressed against the outer surface of the fuse cap at each respective end of the fuse housing. Thus, the conductive cap is fixed only by the friction between the outer surface of the fuse cap and the inner surface of the conductive cap to prevent its removal, and the conductive cap is placed on the fuse cap. Therefore, this method is only applicable to such a circuit: any electrical overload in the circuit will not develop to such an extent that the pressure increases due to the interruption of the fusing element or the burning of the internal arc in the fuse to cause the housing to rupture or explode, or will not cause any of the above-mentioned caps to be removable from the housing. That is to say, in this case, the damage to the fuse due to explosion or due to the burning arc may pose a great danger to the surroundings of the fuse.

[0006] Presumably taking into account all the risks mentioned above, another electric fuse is proposed in CN204289315U. The electric fuse includes a cylindrical tubular housing made of an electrically insulating material, and a fusing element extends through the housing. The housing is electrically connected to each respective cap through each of its ends. However, in this case, the caps are screwed onto each corresponding end of the fuse housing. Therefore, by tightening the said caps instead of simply pressing the caps onto the fuse housing, it is obvious that the connection between the caps and the outer surface of the fuse housing can withstand a greater increase in pressure inside the fuse. As a result, when the pressure inside the fuse is increased, the caps will still be attached to the housing, but the generated gas will still be squeezed inside the fuse housing and cannot be gradually released. If the pressure is high enough, it will cause the explosion of the fuse housing, etc.

[0007] Taking into account all the situations discussed, the fuses of the prior art are strictly limited by the allowed nominal voltage and current values within their respective predetermined sizes, and thus cannot be further adjusted to be applied to circuits with higher technical performance in terms of fuse capabilities.

[0008] The present invention relates to an electric fuse having a fusing element. Such a fuse includes a cylindrical tubular housing made of an electrically insulating material, and the fusing element is inserted through the housing. The fusing element is made of a conductive material having a predetermined resistance and a predetermined fusing temperature. Wherein, at each end region of the said housing, the housing is closed and sealed by a box-shaped cap protruding axially away from the housing. One end region of the box-shaped cap is closed. The box-shaped cap is made of a conductive material and is electrically connected to the fusing element. And wherein, the inside of the housing is filled with an appropriate amount of granular fireproof and electrically insulating material, and the material surrounds the fusing element.

[0009] According to the present invention, at each end region of the fuse housing, i.e., between the housing and the cover, a separating barrier made of a conductive and plastically deformable material is inserted. On the side of the separating barrier facing the interior of the fuse housing, a layer made of an elastic electrical insulating material is provided, and this layer is non-removably connected to the separating barrier such that at each end of the fuse, the fuse element is electrically connected to the respective conductive cover through the conductive separating barrier and extends through the electrical insulating layer formed by the elastic material, so that there is at least one bend or kink in the region within the layer, through which the fuse element is anchored in the layer and fixed against being pulled out.

[0010] In a preferred embodiment of the present invention, the elastic electrical insulating layer is made of silicone resin, which can resist elevated temperatures at least for a certain period of time. Meanwhile, the region of the fuse element outside the layer and inside the fuse housing is surrounded by a granular material, which is silica sand.

[0011] The present invention will be disclosed in more detail based on the embodiments presented in the drawings, in which:

[0012] Figure 1 A high-voltage fuse according to the present invention is shown, which is schematically presented as a partial cross-section along its diameter longitudinal plane during normal use; and

[0013] Figure 2 shows Figure 1 A view of the high-voltage fuse after the fuse element is interrupted due to an electrical overload, also presented as a partial cross-section along its diameter longitudinal plane.

[0014] Figure 1 Only one of the two end regions of the electrical fuse is shown, in which the fuse includes a cylindrical tubular housing 1 made of an electrical insulating material, and a fuse element 2 is inserted through the housing. The fuse element 2 is made of a conductive material having a predetermined resistance and a predetermined fusing temperature. Although only part of the housing 1 is shown in Figures 1 to 2 At each end region 11 of the housing, the housing is closed and sealed by a box-shaped cover 3 protruding axially away from the housing 1. One end region of the box-shaped cover 3 is closed, and the box-shaped cover is made of a conductive material. The cover 3 formed in this way, together with the shape of the disclosed housing 1, jointly forms the overall concept of the high-voltage fuse in terms of shape and size, which is well-known to those skilled in the art and widely used in daily practice. As a result, the fuse can be integrated into various disposable circuits by means of the cover 3.

[0015] The fuse element 2 is inserted through a passage within the housing 1 and is electrically connected to each of the covers 3. The interior of the housing 1 is filled with an appropriate amount of granular fireproof and electrically insulating material 10, which surrounds the fuse element 2 and which, in the illustrated embodiment, is silica sand.

[0016] According to the invention, on each end region 11 of the fuse housing 1, i.e. between the housing 1 and the cover 3, a separating barrier 4 is inserted, which is made of a conductive and plastically deformable material, wherein on the side of the separating barrier facing the interior of the fuse housing 1 a layer 5 made of an elastic electrically insulating material is provided, which in this particular embodiment is silicone resin, and the layer 5 is non-detachably connected to the barrier 4.

[0017] At each end of the fuse, the fuse element 2 is electrically connected to the respective conductive cover 3 via the conductive separating barrier 4 and extends through the electrically insulating layer 5 formed by the elastic material. Here, in the region within the layer 5, the fuse element 2 is suitably bent or formed into a zigzag portion 21 by means of which the fuse element is anchored within the layer 5 and fixed against being pulled out.

[0018] In Figure 1 is shown the fuse during normal use, at which time the fuse element 2 is not interrupted, so that current can flow along the fuse element 2 between the two covers 3 and can pass through the two respective separating barriers 4.

[0019] Once an electrical overload occurs through the fuse due to an overcurrent passing through the cover 2, the separating barrier 4 and the fuse element 2, the fuse element 2 is heated and then overheated, such that at least a part of it melts, causing the fuse element 2 to interrupt. Since both sides of the housing 1 are closed and sealed by the covers 3 and the separating barriers 4, the increase in temperature and the generation of gas inside the housing cause an increase in pressure therein. The increase in pressure causes a certain deformation, namely that the two separating barriers 4 and the layers 5 firmly attached thereto are bent apart from each other, i.e. bent in an outward direction relative to the housing 1 itself.

[0020] Since each end of the fuse element 2 is stuck within the respective layer 5 by virtue of its bent region or bent portion, during the bending of the separating barrier 4 and the simultaneous relative separation of the layers from each other, each part of the interrupted fuse element 2 is displaced away from the other part of the fuse element 2, such that the distance between the two parts of the interrupted fuse element 2 increases, thereby reducing the probability of an arc forming therebetween.

[0021] Thanks to the concept according to the present invention, the main part of the energy released by the interruption of the fusing element 2 is used to bend the barrier 4, rather than generating excessive or even critical mechanical stresses in the contact area between each cover 3 and the housing 1 or within the walls of the housing 1. At the same time, the gap between the two parts of the interrupted fusing element 2 automatically expands, so that the expanded gap can also be easily filled with the granular electrical insulating material 10 within the housing 1, which undoubtedly also reduces the possibility of arc formation.

[0022] Those skilled in the art will undoubtedly understand that this concept of a fuse, although not changing the size of the fuse, allows the fuse to be integrated into such a circuit: where the electrical load and similar technical requirements are much higher than those of circuits where fuses known in the prior art can be applied.

Claims

1. An electric fuse having a fusing element (2), said fuse comprising a cylindrical tubular housing (1) made of an electrically insulating material, said fusing element (2) being inserted through said housing (1), said fusing element being made of a conductive material having a predetermined resistance and a predetermined fusing temperature, wherein, At each end region (11) of the housing (1), the housing (1) is closed and sealed by a box-shaped cover (3) which projects axially apart from the housing (1), one end region of the box-shaped cover (3) being closed, the box-shaped cover (3) being made of a conductive material and being electrically connected to the fuse element (2), and wherein the interior of the housing (1) is filled with an appropriate amount of granular fireproof and electrically insulating material (10) which surrounds the fuse element (2), characterized in that At each of the end regions (11) of the fuse housing (1), a separating barrier (4) is inserted between the housing (1) and the cover (3), the separating barrier (4) being made of a conductive and plastically deformable material. On the side of the separating barrier (4) facing the interior of the fuse housing (1), a layer (5) made of an elastic electrically insulating material is provided, and the layer (5) is connected to the separating barrier (4) in a non-detachable manner. Wherein, at each end of the fuse, the fuse element (2) is electrically connected to the respective conductive cover (3) through the conductive separating barrier (4) and extends through the electrically insulating layer (5) formed of an elastic material, such that there is at least one bend or kink in the region within the layer (5), and the fuse element (2) is anchored and fixed against being pulled out in the layer (5) through the bend or kink.

2. The fuse according to claim 1, characterized in that, The elastic electrically insulating layer (5) is made of silicone resin which can resist elevated temperatures at least for a specific period of time.

3. The fuse according to claim 1 or 2, characterized in that, The region of the fuse element (2) outside the layer (5) and inside the fuse housing (1) is surrounded by a granular material (10) which is silica sand.

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