Electric device and fuse system

Abstract

The invention concerns fuse system and an electric device (1) comprising an electric element (3,5), an electrical conductor (7) which is held in a constant distance to the electric element (3,5) by a holding element (2), and which is electrically connected to the electric element (3,5) by a link element (6, 10), wherein at least a part of the link element (6, 10) is configured to melt into a molten material when the electric element (3,5) overheats, whereby the electrical conductor (7) and the electric element (3,5) are electrically disconnected by a void gap since the distance between the electrical conductor (7) and the electric element (3,5) is held constant.

Description

[0001] Description

[0002] Electric device and fuse system

[0003] The present invention relates to an electric device , a fuse system comprising the device , and the process of triggering the fuse system .

[0004] Standard thermally protected varistors often contain a metal oxide varistor (MOV) material and a thermal disconnection system .

[0005] The varistor is the voltage dependent component , which overheats in the case of signi ficant electrical surge events in a main circuit .

[0006] The thermal disconnection system is a is a thermally triggered system which serves to ensure that the main circuit opens in case of overheating of the varistor due to surge events .

[0007] A typical thermal disconnection system has a solder j oint . When the MOV is overheated, the solder j oint melts . In order to avoid re-connecting or arcing events between the opened j oints additional mechanical systems like arcing sheets are needed .

[0008] Thus , designs and assemblies of state-of-the-art thermal protective varistors are highly complex and costly as disclosed, e . g . , in the published documents US 6636403 B2 and US 20200135368 Al . It is a task of the present invention to provide an improved or simpli fied device and fuse system .

[0009] The invention particularly provides fuse system and an electric device comprising an electric element , an electrical conductor which is held in a constant distance to the electric element by a holding element , and which is electrically connected to the electric element by a link element , wherein at least a part of the link element is configured to melt into a molten material when the electric element overheats , whereby the electrical conductor and the electric element are electrically disconnected by a void gap since the distance between the electrical conductor and the electric element is held constant .

[0010] The holding element is preferably an insulating housing which connects the electric element and the electrical conductor mechanically . Instead of the insulating housing, in all of the following embodiments also a di f ferent holding element may be used .

[0011] The link element preferably comprises a link wire and a solder j oint , wherein the link wire is guided through the insulating housing and is attached to the electric element by the solder j oint . Instead of the link wire and the solder j oint other link elements may be used in the following embodiments of the invention .

[0012] Further embodiments are also described in the attached claims .

[0013] The electric element may comprise a body and a terminal . The body may comprise or may be a varistor. The varistor may comprise or may consist of a metal oxide varistor (MOV) material such as, e.g., ZnO.

[0014] The body may have any suitable shape, e.g., a plate shape, a cylindrical or a cuboid shape.

[0015] The terminal may be an electrode or another kind of metallization on a surface of the body. The terminal comprises an electrically conducting material. The terminal may comprise a metal or a metal alloy. Preferably, a second terminal may be applied on another surface of the body. The two terminals may be applied on two opposing surfaces of the body in order to apply an electric voltage to the body.

[0016] The electric device does further comprise an electrical conductor, which is mechanically connected to the terminal by an insulating housing element. The electric conductor may be an electrically conducting metal wire, e.g., a copper wire, or something similar, e.g., a leaf spring.

[0017] Additionally, the electric device may be electrically connected to the terminal by a link wire. The wire link may be guided through the insulating housing element and may be attached to the terminal by a solder joint.

[0018] The solder joint may be applied by a reflow soldering or a dip soldering process.

[0019] The insulating housing may be, e.g., a molten part or a 3D- printed part. The solder j oint between the link wire and the terminal is configured to get loose when the electric element heats up, since the fusible j oint comprises or consist of a low temperature melting metal , e . g . , a solder material such as soldering tin .

[0020] At least a part comprising at least portions of the link wire and of the solder j oint is configured to melt into a molten material when the electric element overheats whereby the electrical conductor and the terminal are electrically disconnected .

[0021] In other words , when the body of the electrical element , e . g . , a varistor body and the adj acent terminals overheat , the said part melts , and the electrical connection which is part of a main circuit for operating the varistor is interrupted .

[0022] According to an embodiment , the insulating housing is configured to accommodate the molten part of the solder j oint and the link wire and is further configured to provide an insulating gap between the terminal and the electrical conductor when the part of the solder j oint and the link wire is molten .

[0023] The insulating housing has thus the advantage of guaranteeing a speci fied distance or gap between the terminal and the electrical conductor preventing short-circuits or arcing incidents and ensuring a safe disconnection .

[0024] According to an embodiment , the electric device further comprises a curved metal electrode attached to the terminal , wherein the solder j oint is accommodated in a cavity between the curved metal electrode and the terminal, wherein the curved metal electrode is configured to conduct heat from the terminal to the solder joint.

[0025] This has the advantage that the solder joint melts more fastly in case of overheating events since it is heated up from different sides.

[0026] According to an embodiment, at least one of an inner or an outer surface of the curved metal electrode is provided with a button matrix or recess matrix which is configured to capture the molten solder.

[0027] This has the advantage, that the molten solder material is prevented from spreading in the insulating housing.

[0028] According to an embodiment, the curved metal electrode is coated with tin.

[0029] By the tin coating, the molten solder material is again prevented from spreading in the insulating housing since the molten material, e.g., the molten tin may stick or adhere to the tin coating.

[0030] According to an embodiment, the curved metal electrode is provided with bulges for fixation on the terminal, which has the advantage of simplifying and stabilizing the assembly.

[0031] According to an embodiment, the curved metal electrode is provided with a through hole for inserting the link wire, which has the advantage of simplifying the assembly. According to an embodiment , the curved metal electrode has a shape configured for auto-assembly, which has the advantage of simpli fying the assembly . The skilled person can assemble the curved metal electrode on the terminal without further instructions .

[0032] According to an embodiment , the curved metal electrode comprises a branch for external electrical contacting protruding from the insulating housing and configured for use as an indicator pin .

[0033] The indicator pin is a terminal end of an indicator circuit , which is configured to indicate electrical contact between the electrical conductor and the terminal , wherein the indicator circuit is configured to stay closed when the electrical conductor and the terminal are disconnected . The indicator circuit has to be galvanically isolated from the main circuit .

[0034] According to an embodiment , the insulating housing has a hollow cylindrical , cuboid or prism shape with an open side facing the terminal and a side cover on the side facing away from the terminal .

[0035] Thus , the insulating housing can advantageously be placed over the terminal or the terminal and the metal electrode and can also accommodate the solder j oint and the link wire .

[0036] According to an embodiment , the side cover of the insulating housing is provided with a through hole for inserting the link wire , which allows easy assembling and automatic assembling . According to an embodiment, the link wire comprises or consist of a fusible metal material, e.g., of the same material as the solder joint or another low melting material.

[0037] However, preferably the solder joint is heated up more quickly due to its position adjacent to the terminal and the metal electrode. Thus, the solder joint may melt at first.

[0038] The link wire may also comprise or consist of a material with a higher melting temperature than the solder joint and may thus melt at a later point in time.

[0039] According to an embodiment, the link wire has a nail shape with a nail head configured to be contacted with the electrical conductor and with a nail shaft configured to be contacted with the solder joint.

[0040] According to an embodiment, the insulating housing and the link wire have a shape configured for auto-assembly.

[0041] E.g., the insulating housing may provide a through hole for inserting the nail-shaped link wire, which has preferably a length for directly contacting the solder joint after insertion .

[0042] According to an embodiment, the part of the link wire and the solder joint configured to melt comprises the whole solder joint and optionally an adjacent portion of the link wire or no portion of the link wire.

[0043] According to an embodiment, the part of the link wire and the solder joint configured to melt comprises a low temperature melting metal material. According to an embodiment , the electric conductor and the link wire are connected by solder which may comprise the same solder material as the solder j oint .

[0044] The invention further provides an electrical fuse system comprising the electric device according to anyone of the embodiments as described before .

[0045] In particular, the electrical fuse system is configured as described before , wherein the part of the link wire and the solder j oint is configured to melt when the electric element heats up, wherein the insulating housing is configured to collect and accommodate the solidi fied molten material , and wherein the insulating housing is further configured to provide an insulating gap between the terminal and the electric conductor after the part of the link wire and the solder j oint is molten .

[0046] The invention further relates to the process of triggering the electrical fuse system .

[0047] In particular, when the electrical element overheats , the terminal and the optional metal electrode heat up . Thus , the part of the link wire and the solder j oint which is configured to melt when the electric element heats up, melts . Since the solder j oint is preferably located and arranged between the terminal and the metal electrode , the solder j oint melts very quickly . Also , an adj acent portion or the whole adj acent link wire may melt . Thus , the electrical connection between the terminal and the electrical conductor is permanently interrupted . The insulating housing is configured to collect and accommodate the solidi fied molten material , e . g . , by adhering of the molten material to the buttons or recesses of a button matrix or recess matrix or a tin coating on the surface of the metal electrode . The molten material may also fill the recesses or holes of the recess and button matrix .

[0048] A recess or button matrix is a regular or irregular pattern of recesses , holes or buttons and proj ections on the surface of the metal electrode or alternatively or additionally also on an inner surface of the insulating housing .

[0049] Besides , the molten material may also be collected and may solidi fy at the bottom or in a special tub, trough or tank inside the insulating housing .

[0050] The insulating housing is dimensioned accordingly to provide and guarantee an insulating gap between the terminal and the electric conductor after the part of the link wire and the solder j oint is molten and also after the molten material is solidi fied again .

[0051] The further configurations may be according to anyone of the embodiments as speci fied above .

[0052] In the following, the invention is exemplarily described by figures . The invention is not limited by the examples . The details of the examples may be combined di f ferently than described below and in any suitable way . Detailed embodiments of the examples below may be combined with embodiments of the above-described electrical device or fuse system .

[0053] The figures show : Figure 1 : Perspective view of a first embodiment of an electric device . The figure shows the device with an insulating housing applied on a terminal and contacting electrical conductors .

[0054] Figure 2 : Cross-sectional view through the device of the first embodiment . The figure shows the element with a body and terminals , and a metal electrode applied on the first terminal . A solder j oint accommodated between the terminal and the metal electrode connects the terminal with the nailshaped link wire , which is also connected by a solder to the electrical conductor . The nail-shaped link wire is inserted into a through hole of the insulating housing .

[0055] Figure 3 : Perspective view of the first embodiment of the electric device . The insulating housing is shown in transparent for means of better illustration . The figure shows the device in an operating state .

[0056] Figure 4 : Perspective view of the first embodiment of the electric device . The insulating housing is shown in transparent for means of better illustration . The figure shows the device in a state when the fuse is triggered and the solder j oint and a part of the shaft of the link wire is molten .

[0057] Figure 5 : Perspective view of a first embodiment of the metal electrode . The electrode has a rectangular outline and a curved body with a through hole .

[0058] Figure 6 : Perspective view of a second embodiment of the metal electrode . The electrode has a circular outline and a curved body with a through hole and a pattern of bulges for contacting and fixation on the terminal .

[0059] Figure 7 : Perspective view of a third embodiment of the metal electrode . The electrode has a circular outline and a curved body with a through hole and a pattern of recesses or buttons on an outer surface for adhering and absorbing of molten material .

[0060] Figure 8 : Perspective view of a fourth embodiment of the metal electrode . The electrode has a circular outline and a curved body with a through hole and a pattern of bulges for contacting and fixation on the terminal .

[0061] Figure 9 : Perspective view of a first embodiment of the insulating housing . The housing has a cuboid outline and a cylindrical recess around a through hole in the side cover .

[0062] Figure 10 : Perspective view of a second embodiment of the insulating housing . The housing has a cylindrical outline and a cylindrical recess around a through hole in the side cover .

[0063] Figure 11 : Perspective view of the third embodiment of the insulating housing . The housing has a cylindrical outline and a cylindrical recess around a through hole in the side cover . The room inside the insulating housing is an empty void . The side cover covers only one head side of the housing; the opposite side is uncovered .

[0064] Figure 12 : Perspective view of an alternative embodiment of the link wire which has the shape of a shaft (nail without head) . Figure 13 : Perspective view of a first embodiment of the whole device which is encapsulated in a mold . The electrical element has a circular, cylindrical shape . Only two electrical conductors are protruding .

[0065] Figure 14 : Perspective view of a second embodiment of the whole device which is encapsulated in a mold . The electrical element has a cuboid shape . Only two electrical conductors are protruding .

[0066] Figure 15 : Perspective view of the first embodiment of the whole device ( the encapsulation is not shown for better illustration) . The first terminal is additionally contacted by an indicator pin, also protruding from the device .

[0067] In particular, figure 1 is directed to a first embodiment of an electric device 1 , which may be a thermally protected varistor . The figure shows the device 1 with an insulating housing 2 applied on a first terminal 3 . On the opposite side of the housing, a second terminal 4 is provided . The terminals allow electrical contacting of the body 5 , which may be a metal oxide varistor .

[0068] The varistor has a round circular, cylindrical shape . However, the shape may be di f ferent as shown later on .

[0069] On the surface of the insulating housing which consists of an insulating material such as a polymer or a ceramic, the nailhead of a nail shaped link wire 6 is provided . The nail shaped link wire connects the first terminal 3 and the first electrical conductor 7 electrically . The first and second electrical conductors 7 and 8 serve for external contacting . Figure 2 shows a cross-sectional view through the device 1 of the first embodiment . The figure shows the element with the body 5 and terminals 3 , 4 , and a metal electrode 9 applied on the first terminal 3 . The metal electrode in the example has also a round, circular shape with a curving but may also be shaped di f ferently as shown later on .

[0070] A solder j oint 10 accommodated between the first terminal 3 and the metal electrode 9 connects the first terminal 3 with the nail-shaped link wire 6 . On the other end of the link wire 6 , the link wire 6 is also connected by a solder to the first electrical conductor 7 for external contacting in a high voltage main circuit or operating circuit .

[0071] The nail-shaped link wire 6 is inserted into a through hole of the insulating housing 2 . The nail-shape has the advantage of providing a large surface for contacting with the electrical conductor 7 and guarantees an easy and accurate manual or automatic assembling .

[0072] Figure 3 shows again the perspective view of the first embodiment of the electric device 1 . The insulating housing 2 is now shown in transparent for means of better illustration . The figure shows the device in an operating state , when the main circuit is closed, and an electrical current flow is allowed .

[0073] Figure 4 shows the device 1 in a state when the fuse is triggered and the solder j oint 10 and a part of the shaft of the link wire 6 are molten . The molten material in the example solidi fies on an outer surface of the metal electrode 9 facing the side cover of the insulating housing 2 . Adhering and absorption of the molten material may be improved by providing a recess and button matrix on a surface of the metal electrode or by a solder material-like coating, e . g . , a tin coating .

[0074] Figures 5 to 8 show di f ferent embodiments of the metal electrode 9 . The metal electrode 9 consists of an electrically conductive or highly conductive material .

[0075] As shown in the figures , the electrode has a planar shape with a step or curving 9A for forming a void configured for accommodating the solder j oint between the electrode and the terminal .

[0076] The electrode may have a circular or rectangular or di f ferently shaped outline . The curving or bulge or protrusion, which are meant as synonyms in the present text , of the metal electrode is centrally positioned and provides a through hole in a center position .

[0077] The curving or bulge or protrusion 9A has , e . g . , a circular shape .

[0078] The surface of the metal electrode 9 which faces the terminal may be provided with a pattern of bulges 9B for better electrical contacting and a firm mechanical fixation on the terminal 3 . A di f ferent type of bulge pattern is shown in figure 8 .

[0079] Figure 7 shows an embodiment of the electrode 5 , wherein the surface facing away from the terminal 3 and facing towards the insulating housing is provided with a pattern 9C or matrix, which is a synonym, of recesses or buttons for better adhering and absorbing of the molten material .

[0080] Figures 9 to 11 show embodiments of the insulating housing 2 , which is configured as a hood-shaped cover for covering at least the electrode 5 .

[0081] The housing 2 has , e . g . , a cuboid, prismatic, or cylindrical outline shape and comprises a hollow void, and a cylindrical recess 2A around a through hole 2B in the side cover 11 , suitable for accommodating the head of a nail-shaped link wire 6 . This configuration also facilitates auto-assembling of the components .

[0082] A side cover 11 covers only one head side or cover side of the housing 2 the opposite side is uncovered . The housing 2 is arranged by its uncovered side on the surface of the terminal 3 .

[0083] Figure 12 shows an alternative embodiment of the link wire 6 which has the shape of a shaft (nail without head) instead of a nail with a nail head .

[0084] Figures 13 to 15 show embodiments of the whole device 1 which is encapsulated in a mold 12 or casting 12 of insulating polymer or plastic or ceramic material . The electrical element has a circular, cylindrical shape or a rectangular, cuboid shape . In figures 13 and 14 , only the two electrical conductors 7 and 8 are protruding for external connection in the main circuit .

[0085] In figure 15 an optional external conductor, an indicator pin 13 , is provided, which contacts directly the first terminal 3 . Thus , the electrical connection to the terminal 3 and the body 5 remains when the solder j oint 10 melts .

[0086] The indicator pin 10 is a terminal end of an indicator circuit , which is configured to indicate electrical contact between the electrical conductor 7 and the terminal 3 , wherein the indicator circuit is particularly configured to stay closed when the electrical conductor 5 and the terminal 3 are disconnected . The indicator circuit has to be galvanically isolated from the main circuit .

[0087] Reference signs

[0088] 1 device

[0089] 2 insulating housing

[0090] 2A recess

[0091] 2B through hole

[0092] 3 first terminal

[0093] 4 second terminal

[0094] 5 body

[0095] 6 link wire

[0096] 7 electrical conductor

[0097] 8 electrical conductor

[0098] 9 metal electrode

[0099] 9A curving

[0100] 9B bulges

[0101] 9C recess matrix

[0102] 10 solder j oint

[0103] 11 side cover

[0104] 12 mold

[0105] 13 indicator pin

Claims

Claims (we claim)1. An electric device (1) comprising: an electric element (3,5) , an electrical conductor (7) which is held in a constant distance to the electric element (3,5) by a holding element (2) , and which is electrically connected to the electric element (3,5) by a link element (6, 10) , wherein at least a part of the link element (6, 10) is configured to melt into a molten material when the electric element (3,5) overheats, whereby the electrical conductor (7) and the electric element (3,5) are electrically disconnected by a void gap since the distance between the electrical conductor (7) and the electric element (3,5) is held constant.

2. The electric device (1) according to claim 1, wherein the holding element (2) is an insulating housing (2) which connects the electric element (3,5) and the electrical conductor (7) mechanically.

3. The electric device (1) according to claim 2, wherein the link element (6, 10) comprises a link wire (6) and a solder joint (10) , wherein the link wire (6) is guided through the insulating housing (2) and is attached to the electric element (3,5) by the solder joint (10) .

4. The electric device (1) according to claim 3, further comprising a curved metal electrode (9) attached to the electric element (3,5) , wherein the solder joint (10) is accommodated in a cavity between the curved metal electrode (9) and the electric element (3,5) , wherein the curved metalelectrode (9) is configured to conduct heat from the electric element (3,5) to the solder joint (10) .

5. The electric device (1) according to claim 4, wherein at least one of an inner or an outer surface of the curved metal electrode (9) is provided with a button matrix or recess matrix (9C) which is configured to capture the molten solder.

6. The electric device (1) according to anyone of claims 4 and 5, wherein the curved metal electrode (9) is coated with tin .

7. The electric device (1) according to anyone of claims 4 to6, wherein the curved metal electrode (9) is provided with bulges (9B) for fixation on the terminal (3) .

8. The electric device (1) according to anyone of claims 4 to7, wherein the curved metal electrode (9) is provided with a through hole for inserting the link wire (6) .

9. The electric device (1) according to anyone of claims 4 to8, wherein the curved metal electrode (9) has a shape configured for auto-assembly.

10. The electric device (1) according to anyone of claims 4 to 9, wherein the curved metal electrode (9) comprises a branch for external electrical contacting protruding from the insulating housing (2) and configured for use as an indicator pin ( 13 ) .

11. The electric device (1) according to anyone of claims 3 to 10, wherein the link wire (6) or the link element (6, 10) is completely covered by the insulating housing (2) .

12. The electric device (1) according to anyone of claims 3 to 11, wherein the link wire (6) comprises or consist of a fusible metal material.

13. The electric device (1) according to anyone of claims 3 to 12, wherein the link wire (6) has a nail shape with a nail head configured to be contacted with the electrical conductor (7) and with a nail shaft configured to be contacted with the solder joint (10) .

14. The electric device (1) according to anyone of claims 3 to 13, wherein the insulating housing (2) and the link wire (6) have a shape configured for auto-assembly.

15. The electric device (1) according to anyone of claims 3 to 14, wherein the part of the link wire (6) and the solder joint (10) configured to melt comprises the whole solder joint (10) and optionally an adjacent portion of the link wire ( ) .

16. The electric device (1) according to claim 15, wherein the part of the link wire (6) and the solder joint (10) configured to melt comprises a low temperature melting metal material .

17. The electric device (1) according to anyone of claims 3 to 16, wherein the electric conductor and the link wire (6) are connected by solder.

18. The electric device (1) according to anyone of claims 2 to 17, wherein the insulating housing (2) is configured to accommodate the molten material and is further configured toprovide an insulating void gap between the electric element(3,5) and the electrical conductor (7) which is free from the molten material when the part of the link element (6,10) is molten .

19. The electric device (1) according to anyone of claims 2 to 18, wherein the insulating housing (2) has a hollow cylindrical, cuboid or prism shape with an open side facing the electric element (3,5) and a side cover on the side facing away from the electric element (3,5) .

20. The electric device (1) according to claim 19, wherein the side cover of the insulating housing (2) is provided with a through hole (2B) for inserting the link element (6,10) .

21. Electrical fuse system comprising the electric device (1) according to one of the claims 2 to 20.

22. Electrical fuse system according to claim 21, wherein the part of the link element (6,10) is configured to melt when the electric element heats up, wherein the insulating housing (2) is configured to collect and accommodate the solidified molten material, wherein the insulating housing (2) is further configured to provide an insulating gap between the electric element (3,5) and the electric conductor after the part of the link element(6,10) is molten.

23. Process of triggering the electrical fuse system according to claim 21 or 22.

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