GB2593941A

GB2593941A - Disconnect device with integrated fuse

Info

Publication number: GB2593941A
Application number: GB2008307.7A
Authority: GB
Inventors: Mujawar Asad; Burkett Roger; Sabale Varsha; Stevens Alistair
Original assignee: Eaton Intelligent Power Ltd
Current assignee: Eaton Intelligent Power Ltd
Priority date: 2020-04-08
Filing date: 2020-06-02
Publication date: 2021-10-13
Also published as: GB202008307D0

Abstract

A pyrotechnic electrical disconnect device comprises a conductor with two sections 102a, 102b separated by a breakable section 102c, defining a first current conduction path (110, fig. 3A), and a moveable body 106 (optionally a piston) that severs the breakable section, thus opening the first current conduction path. The piston carries a fuse 104 so that as the piston moves to break the conductor the fuse electrically and physically contacts the conductor forming a second current conduction path (112, fig. 3A) parallel to the first conduction path before the piston severs the conductor and opens the first path. Contact may be made via electrical contacts 108a, 108b, integral to the conductor. The fuse may be selected to fail above a predetermined current, breaking the second current conduction path. A pyrotechnic actuator 114 may actuate the piston. Fuse-fatigue and unintended activation of the breaker are avoided as the fuse is only electrically connected once the circuit-breaker is triggered, rather than being connected during normal operation.

Description

Disconnect device with integrated fuse

Field

This relates to opening, or interrupting, a current conduction path. In particular, this relates to a device for opening a current conduction path, the device comprising a fusible body (such as a fuse), and a method of operating the device.

Background

Current conduction paths can be opened by breaking a continuous conductor which iv defines the current conduction path. One approach is to use an electrical interrupter device comprising an actuator, in some examples a pyrotechnic based actuator, to break the continuous conductor.

It is desirable to provide an improved apparatus for opening a current conduction path. Such an improved apparatus is particularly desirable in high current and/or high voltage applications, for example batteries for electric vehicles or electrical overload mechanisms for industrial processes, which require reliable and rapid opening of a current conduction path.

Summary

In a first aspect, an electrical disconnect device is provided as defined in appended independent apparatus claim:I, with optional features defined in the dependent claims appended thereto. In a second aspect, a method of operating the device of the first aspect is provided, as defined in the appended independent method claim.

Previous arrangements with an integrated fuse have used a fixed fuse which is configured to carry at least a portion of the total system current during normal operation of the device. However, the constant current load through the fuse can fatigue the fuse (particularly in high current situations such as in electric vehicles), which can lead to erroneous tripping of the device as a result of fuse fatigue.

In the following specitcation. an electrical disconnect device for opening a current conduction path is described. The device is arranged to make an electrical conduction path through a fusible body before breaking a parallel electrical conduction path through a conductor.

The device described herein comprises: a conductor, a fusible body (such as a fuse), and a moveable body (or moveable member) configured to carry the fusible body. The conductor comprises first and second portions and a breakable portion arranged between the first and second portions; a first current conduction path is defined along the conductor, through or Via the first and second portions and the breakable portion. The moveable body is configured to sever the breakable portion of the conductor to open the first current conduction path. The moveable body is configured to carry the fusible body such that, before the breakable portion of the conductor is severed, the fusible body is brought into electrical contact with at least one of the first and second Iv portions of the conductor to define a second current conduction path through the fusible body, the second current conduction path connected, or arranged, in parallel with the first conduction path (i.e. the two paths are electrically parallel).

The moveable body is configured to move from a first position to a second position and then to a third. position (for example, in response to automatic actuation of the device or in response to manual input). In the -first (initial) position of the movable body (also referred to as the first position of the device), the first current conduction path is defined through the conductor and no current conduction path is defined through the fusible body, or fuse. The fuse is electrically isolated from at least one of the first and second conductor portions. In this first position, before triggering of the device, the device is in a normal operational mode and current is able to flow along the first current conduction path, defined through the breakable portion, when the device is connected to an external circuit.

After triggering of the device, the moveable body is configured to move towards the third (final) position, via the second position. In the second, intermediate, position of the device, the first current conduction path is still defined through the conductor. The fusible body is electrically connected to both the first and second conductor portions and the second current conduction path is defined through or via the (electrically conducting) fusible body. Current flows through both, parallel, conduction paths in this second position, but the current is insufficient to blow or melt the fusible body (i.e. the current is below a predetermined threshold or below the rating of the fusible body or fuse).

In the third (final) position of the device, the (insulating) moveable body has severed the breakable portion of the conductor to open the first current conduction path through the conductor; all the current flows along the second current conduction path, through the fusible body. Once the current through the fusible body reaches the predetermined threshold (i.e, the current is at or above the rating of the Fusible body or fuse), the fusible body melts or breaks and the second current conduction path opens. At that stage, no current flows through the device and the external circuit to Which it is connected is interrupted.

Optionally, the fusible body is configured to break above a current threshold in order to open the second current conduction path and stop current flow through the device. The iv current threshold for the fuse can be determined by the specific application of the device. In some applications, operation of device can be in response to a collision or other external event. In these examples, the fusible body may be rated at or just below the normal system current in order that, once the first current conduction path is opened, the second current conduction path will be opened almost immediately afterward. This arrangement can improve safety in a collision, for example when the device is deployed in a vehicle. In other examples, the fusible body maybe configured to break at a current above the normal system current, for example in response to an overcurrent condition. The predetermined current threshold can be set depending on the requirements of the particular device application, and an appropriate fusible body chosen.

By making the electrical connection through a fusible body (such as a fuse) before breaking the parallel connection through the conductor, arcing at the conductor can be reduced or eliminated; any fault current or overcurrent through the device is cleared at the fuse and any arcing can be contained within the fuse (for example, within a housing surrounding a fusible portion of the fuse). This containment protects other components of the device, and can facilitate provision of a smaller and cheaper device, since the housing of the device need not be as large or robust as for devices where arcing occurs at the conductor. This approach can therefore provide advantages over other devices which make a connection through a moveable fuse only after the main current caning conductor is broken (for example in arrangements where a fuse bridges the separation point of the severed conductor, or where a moveable body forces broken ends of the conductor into electrical contact with a fuse), since in such devices arcing occurs at the broken conductor before the fuse can make electrical contact-with the severed conductor. -4 -

The moveable body is configured to bring the fusible body into electrical contact with the first and/or the second conductor portions during operation of the device. Optionally the fusible body protrudes beyond the moveable body to make electrical contact with the first and/or second conductor portions. This arrangement may facilitate reliable and repeatable contact with conductor portion(s). Alternatively, the fusible body maybe entirely enclosed by the moveable body, is the moveable body arranged to allow the electrical contact between the fusible body and the first and/or second conductor portions. This arrangement may allow for provision of a smaller device. Optionally, the fusible body comprises two connection contacts configured to ro electrically connect to the first and second conductor portions, respectively. These connection contacts may protrude beyond the moveable body. Optionally the connection contacts are disposed at either end of the fusible body, optionally at either end of a fusible portion which is enclosed within the moveable body and/or within a housing surrounding the fusible portion. This arrangement may facilitate containment /5 of any arcing upon opening of the second current conduction path. Optionally, the fusible body is a fuse.

Optionally, the moveable body is configured to bring the fusible body into electrical contact with both the first and second conductor portions substantially simultaneously.

This arrangement can provide for a simpler device, since a symmetrical arrangement with rigid electrical / connection contacts may be used. Optionally the fusible body is in electrical contact with one of the first and second conductor portions during normal operation of the device, and the moveable body is configured to bring the fusible body into electrical contact with the other of the first and second conductor portions. This arrangement may allow flexible contacts to be used. in both examples, the fusible body is electrically isolated from one of the first and second conductor portions during normal operation of the device so that no current flows through the fusible body and there is no fuse fatigue.

Optionally, the device further comprises first and second electrical contacts, the first and second electrical contacts electrically connected to the first and second portions of the conductor, respectively. in such arrangements, the fusible body is brought into physical and electrical contact with the first and/or second electrical contacts by the moveable body, as appropriate, and the second current conduction path is defined through the first and second electrical contacts and the fusible body. Optionally, the first and second electrical contacts are formed integral to the conductor. This can -5 -provide a good electrical contact between the components and a more robust device. In other examples the first and second electrical contacts are joined or coupled to the conductor; this approach may allow the device to be manufactured more cheaply, since simpler conductor geometries can be used.

Optionally, the first and second electrical contacts are configured to receive the fusible body. This can provide improved electrical contact between the components. Optionally, at least one of the first and second electrical contacts comprise a retaining member configured to retain the fusible body, optionally each contact comprises a /0 retaining member. Optionally, the retaining member is a spring clip or comprises a resilient member arranged to retain the fusible body. The use of retaining member(s) can provide an orientation independent device, since it allows both the fusible body and the moveable body to be retained in the final, third, position after operation of the device. Optionally, in the third (final) position the moveable body is configured to be is disposed between the first and second portions of the conductor, after severing of the breakable portion. This can improve the isolation of the first and second conductor portions and prevent reopening of the first current conduction path via the breakable portion.

Optionally, the moveable body comprises a piston configured to apply a force to shear the conductor in the breakable portion in order to open the current conduction path. By concentrating force from the moveable body (such as a piston) on the breakable portion, improved severing of the breakable portion can be provided. Optionally, the breakable portion of the conductor comprises a hole through the conductor and at least one shearable portion arranged between the hole and a side of the conductor. In this arrangement, an end of the piston can be configured to contact the at least one sheara lite portion. The mechanical weakness introduced by the hole can facilitate easier shearing of the breakable portion. Moreover, by reducing the surface area of the breakable portion the pressure applied for a given force is increased; this can again facilitate easier shearing of the breakable portion, as well as allowing for the use of smaller and cheaper actuators. A smaller and cheaper device may therefore be provided.

Optionally, the device further comprises an actuator configured to actuate the moveable body. Optionally, the actuator is a pyrotechnic charge configured, upon ignition, to release gas into an ignition chamber in order to exert a force on the moveable body.

Such explosive charges deliver large forces in a short space of time, which can provide a device with a quick response time. Optionally the ignition chamber is at least partially defined by the moveable body; this can provide more effective and efficient transfer of force and may decrease the time required to sever the conductor. A quicker and more reliable device may therefore be provided.

Disclosed herein is a method of operating an electrical disconnect device, the method comprising moving a moveable body from an initial position towards a final position, wherein in the first position a first current conduction path is defined along a Iv conductor, the conductor comprising first and second portions and a breakable portion arranged between the first and second portions. The method further comprises electrically connecting (optionally electrically connecting respective connection contacts of) a fusible body carried by the moveable body to at least one of the first and second portions of the conductor and defining a second current conduction path is through the fusible body, the second current conduction path connected in parallel to the first conduction path, The second conduction path is defined when the moveable body is in an intermediate position between the initial and final positions. After defining the second current conduction path, the method comprises severing, with the moveable body, the breakable portion of the conductor to open the first current conduction path.

Optionally, the method further comprises severing the fusible body to open the second current conduction path and stop current flow through the device. This allows current flow through the device to be stopped and one or more electrical components of the circuit to which the device is electrically connected to be isolated, for example in response to a collision or fault. Optionally, the method further comprises, after severing the breakable portion, disposing, in the final position, the moveable body between the first and second portions of the conductor. This can allow the provision of a safer and more robust device by reducing the risk of the first conduction path reopening, In some examples, the method comprises actuating an actuator to move the moveable body. Optionally, the actuator comprises a pyrotechnic actuator. In such an arrangement, actuating: the actuator comprises igniting the pyrotechnic actuator to release gas into an ignition chamber, and the method comprises exerting pressure on the moveable body in dependence on the released gas (to move the moveable body).

Optionally, the moveable body comprises a void wnich at:cast partially defines the ignition chamber.

A system is provided comprising a device as described above and a controller arranged to provide a signal to the actuator to actuate the actuator. Such a system may be used in any suitable application where an electrical interrupter (or automatic circuit breaker, where an activation trigger is provided) is required, such as for overload in industrial applications, for example.

/0 A vehicle is provided comprising a device as described above. Optionally, the vehicle may further comprise a controller arranged to provide a signal to the actuator to ignite the actuator. Optionally, the vehicle is an electric vehicle. The device may be used, for example, to break a circuit in a battery of the vehicle in case of an accident. This may improve safety.

It will be understood that any of the features described above with eference to the device of the -first aspect may be provided in any suitable combination. Moreover, any such features may be combined with any features of the method of the second aspect, or vice-versa, as appropriate.

Brief Description of the Drawings

The following description is with reference to the following Figures: Figures IA to 11) show a schematic cross section illustrating different positions of a device in accordance with a first example of the first aspect; Figures 2A to 2D show a schematic cross section illustrating different positions of a device in accordance with a second example of the first aspect; Figure 3A illustrates an example first current conduction path within the device, and Figure 3B illustrates example second current conduction paths within the device of the first and second examples (the external circuit to which the device is connected to cause current to flow is nut illustrated); Figure 4 illustrates a cross section of an interior of a device in accordance with the first example of Figure 1: in Figure 4A the device is in the first, initial, position, and in Figure 4B the device is in the third, final, position; Figure,5 illustrates different perspective views of the conductor and fusible body of a device in accordance with the first example of Figure 1, wherein the device is in the first, initial, position and current can flow through the device via the conductor; -8 -Figures 6A and 6P, illustrate a vehicle comprising the device of the first aspect; and Figure 7 illustrates a method in accordance with the second aspect.

Detailed Description

A device for opening a current conduction path and isolating an electrical component, the device comprising an integrated moveable fuse, is described generally with reference to Figures r. to 3, and various examples, options or alternatives discussed. In particular, Figure 1 illustrates a device with fixed and/or rigid (optional) electrical Iv contacts, and Figure 2 illustrates an alternative device with at least one flexible (optional) electrical contact. Other example arrangements not illustrated herein may also be used to provide a device configured to make an electrical connection through a fusible body before breaking a parallel electrical connection through a conductor. A specific example of such a device is then described with reference to Figures 4 and 5.

In all examples, a device 100 comprises a conductor 102, a fusible body104 and a moveable body 106 configured to carry the fusible body 104.

With reference to Figures 1, 2 and 3, conductor 102 comprises a first portion una, a second portion Kgrb, and a breakable portion 102C arranged between the first and second portions ioga, 102b. Here the breakable portion 102C is connecting the first and second conductor portions, but there may be other conductor portions, and/or other material such as a weld or electrical adhesive, between these different portions of conductor 102 as appropriate.

Fusible body 104 optionally comprises connection contacts 104a, 104b disposed at either end of the fusible body. A housing 104d may be arranged around a portionio4c of the fusible body (defined by dashed lines in Figures Tr and 2), and the connection contacts io4a, 104b can be arranged external to the housing 104{1 and at either end of the fusible portion 104c. in other examples, the fusible body may be a single electrically conducting wire which can be electrically connected at either end to the first and second conductor portions 102a, 10213. Optionally, the fusible body is configured as a fuse.

The moveable body ro6 is arranged to retain the fusible body 104. Optionally, the moveable body is provided with a recess in which the fusible body 104 is disposed. The -9 -fusible body may be retained by a press fit or clip fit arrangement. Optionally, the fusible body is coupled to the moveable body lob. Any suitable arrangement or configuration can be used for the moveable body to hold or retain the fusible body so that movement of the moveable body causes corresponding movement of the fusible body 104. In this way, the moveable body is said to carry the fusible body 104. In these examples, the fusible body is carried by the moveable body such that a portion of the fusible body protrudes from either side of the moveable body.

Figures /A and 2A illustrate device 100 in a first, initial, position (before triggering of xv the device 100). In this first position, a first current conduction path 110 is defined along the conductor 102, such that current travels through the first and second portions 102a, 102b and through the breakable portion 102C between (and optionally connecting) the first and second portions. The components defining this first current conduction path 110 are illustrated schematically in Figure 3A. The device is in a first, is initial, position and the (closed) first current conduction path no is defined through the device such that current can flow around a circuit to which the device is connected via conductor 102.

In the first position of device 100, the fusible body is electrically isolated from at least one of the first and second conductor portions and no current flows through the fusible body 104. In the example of Figure IA, the moveable body is in the first position and is arranged to retain or hold the fusible body such that the fusible body is electrically and physically isolated from the conductor 102. In the example of Figure 2A, in the first position the fusible body is held by the moveable body such that the fusible body is electrically connected to one of the first and second portions 102a, 102b (here to the first portion 102a), but not to the other of the first and second conductor portions (i.e. the fusible body 104 is not connected to the second portion 102b). Any suitable arrangement may be used such that, during normal operation of device 100, no current flows through the fusible body. The fusible body is thus not fatigued and nuisance tripping of device 100 Cart be reduced.

When device 100 is triggered, for example by a collision or other triggering signal, an actuator (not shown) is arranged to cause the moveable body lob to move (in direction 128) towards the conductor 102 and into a second, intermediate, position shown in Figures rB and 2B. The actuation could also be manual, for example by means of a lever. Movement of the moveable bodyro6 causes corresponding movement of the -10 -fusible body it carries (i.e. the fuse is considered to be moveable). in particular, movement of the moveable body in direction 128 brings the fusible body 104 into electrical contact with one or both of the first and second portions of the conductor 102 (optionally via the connection contacts 104a, 104b of fusible body) to define a second current conduction path 112 through the fusible body 104 (see Figure 313, which illustrates the device components through which the current conduction path is formed for each of the first and second examples of device 100 described herein -the first example of Figure 1 is shown in the upper figure and the second example of Figure 2 is shown in the lower figure).

This second conduction path 112 is electrically parallel to the first current conduction path 110 (both conduction paths are defined through the first and second conductor portions 102a, 102b, but take different paths between these two conductor portions, as shown in Figures 3A and 3B). In particular, the first conduction path is defined is through breakable portion 102C, and the second conduction path is defined through fusible body 104 (and optionally through electrical contacts 108a, 108b). The external circuit to which the device is connected in order for current to flow is not shown here. Since current flows through both conduction paths 110, 112 at the same time, the amount of current through each path is determined by the resistance of the respective paths. The sum of the current through the two parallel paths is equal to the total system current.

In the example of Figure 1B, the fusible body is brought into electrical and physical contact with bath the first and second conductor portions 102a, 102b by the movement of the moveable body ion. in the example of Figure 2B, the fusible body is already in electrical contact with the first portionto2a of the conductor in the first position (Figure 2A) and is brought into contact with the second portion 102b by the movement of the moveable body 106 (Figure 2B). Any suitable arrangement may be used such that, once in the second position, the fusible body is in electrical contact with both the first and second conductor portions 102a, 102b to define the second current conduction path 112.

In some example arrangements, the fusible body 104 can he connected to the respective portions of the conductor 102 via electrical contacts:108a, 1o8b, as shown in Figures 1 and 2. In some arrangements, the electrical contacts 108 can be electrically coupled to the conductor 102 when the device is in the first position (as shown), but in other arrangements the connection contacts may be electrically coupled to the. fusible body 104 rather than the conductor 102 (for example, they maybe coupled to the connection contacts 104a, 104b, or provided in place of the connection contacts 10.4a, 104b), or one electrical contact may be coupled to the fusible body and the other may be coupled to the conductor (for example), In other example arrangements, fusible body 104 and/or conductor 102 may be shaped so as to facilitate direct electrical contact between the components in the second position (i.e. there are no electrical contacts 108). For example, in an alternative arrangement to Figure 1 the fusible body may be arranged in a Ll-shape so as to contact the conductor directly when the device is in the second ni -position. Any suitable arrangement may be provided to facilitate the making of an electrical conduction path through the fusible body to4 before breaking a parallel electrical conduction path through conductor 102, as described herein.

In the example of Figure 2, where the fusible body is already in electrical contact with is the first portion ito2a of the conductor in the first position (here via first electrical contact 108a), at least one component is flexible to accommodate movement of the moveable body 106 from the -first position to the second position whilst maintaining electrical connection between the first conductor portion 102a and the fusible body 104. For example, one or more of contacts 1042 and/or 108a may be flexible; optionally, the contacts may be provided as a flexible shunt or wire. The electrical connection on the other side of the fusible body, between fusible body 104 and the second conduction portion 1.02b may be flexible or may be rigid. For example, electrical con tact108b may be a rigid connection having any suitable shape or configuration. Similarly, the electrical contacts 108 illustrated in the example of Figure 11E3 may be flexible or rigid, as appropriate. Any suitable arrangement maybe provided to facilitate the provision of two, parallel, conduction paths 110 and 112 through the conductor 102 and fusible body 104, respectively.

In some examples, fusible body 104 can comprise a fuse having a fusible portion 104c and connection contacts -104a, -.1.04b arranged either side of the fusible portion 104c and optionally protruding from the moveable body. Fusible portion 104c can be a thin metal wire or strip configured to melt when an overrurrent flows through it, or any other suitable material configured to melt or break in response to a current above a predetermined threshold (for example a fuse rating). Fusible portion 104c is here disposed within and enclosed by a fuse housing 104d, which housing can contain any broken components of the fuse and/or any electrical arcing caused by breaking of the fusible portion 104c, as is discussed below in more detail. Additionally or alternatively, the moveable body can be configured to at least partially enclose the fusible portion of fu si bl e body 104 to contain any arcing.

With reference to Figures -IC and 2C, which illustrate an intermediate position between the second and third positions, it can be seen that the moveable body continues to move in direction 128. In this intermediate position, the moveable body has contacted the breakable portion 102c of the conductor 102 and begun to sever the breakable portion in order to open the first current path 110 through the conductor 102. In this Iv intermediate position of the moveable body 106, current is still flowing along conduction path 110, since the conductor 102 is not entirely severed at (or in) the breakable portion. Current also still flows through the second current conduction path 112 defined through the fusible body 104. Both, parallel, conduction paths are thus maintained.

Breakable portion 102C can be integral with the rest of the conductor 102, or may be mechanically coupled to the conductor 102, in any suitable manner, to provide the necessary electrical connection to define the current path 110. Where the breakable portion is coupled to the first and second portions (which coupling is both mechanical and electrical such that the breakable portion remains in electrical contact with the rest of conductor 102 during normal operation of the device to define the current conduction path H0), the coupling may optionally be by way of electrically conductive adhesive, welding, brazing, press-fit, interference fit, soldering, or the like. When breakable portion is integral to the conductor 102, severing of the breakable portion is understood to comprise a mechanical breaking (shearing, cuffing, splitting, etc.) of the conductor body. However, when breakable portion is coupled to the first and second portions, severing is understood to encompass breaking of the joint between the breakable portion and the rest of the conductor to sever (i.e. separate) the breakable portion from the rest of the conductor 102 and open the current conduction path.

During operation / actuation of the device, the moveable body continues to move towards the third, final, position (which position is shown in Figures 1D and 2D). in this final position, the breakable portion 102C of conductor 102 is completely severed and no current flows through the conductor 102. For example, the conductor 102 may be broken or sheared at the breakable portion, or the breakable portion 102C is otherwise severed from the conductor (for example, breakable portion 102C may be an insert which is pushed out of place by the moveable body 106 and separated from the rest of the conductor) such that the first and second portions 102a, 102h are physically and electrically separated from one another and no current flows through conduction path no. In the example shown in Figures ID and 2D, at least part of the breakable portion 102C is physically separated from the rest of the conductor. In other arrangements, a single break maybe made at the breakable portion, and the ends of the conductor proximate the break may be pushed away from each other by the moveably body. The physical Iv separation of the conductor portions 102a, 102b may be improved by configuring the moveable body 106 to sit between the conductor portions after severing of the breakable portion 102C, as illustrated. The moveable body may be retained in this position, This prevents the broken or separated parts of the breakable portion 102c from moving back into electrical contact with each other or with the rest of conductor rc, 102, and may facilitate provision of an orientation independent device 100. Tri such arrangements, moveable body 106 is formed of an insulating material in order to electrically and physically isolate the broken and/or separated components and prevent the two conductor portions 102a, 102b coming back into electrical contact with one another via the breakable portion 102e.

As discussed above, in the third position, shown in Figures ID and 211), the current path 110 has been opened, but current will still flow (temporarily) through current path 112 defined through the fusible body 104. However, since in the third position the total system current flows through the fusible body 104, in an overcurrent or fault condition the fusible body will melt or break and open the second current conduction path 112. In particular, the fusible body 104 is configured to break above a current threshold in order to open the second current conduction path 112 and stop all current flow through the device too. ft will be understood that the time for which current flows when the device is in the third position depends on the size and shape of fusible body 104, and the size of the current -flowing through device too, The device 100 can thus be tailored to particular current ratings by selecting an appropriate conductor geometry and an appropriate fusible body (for example by selecting an appropriately rated fuse).

It will be understood that, in other examples, more than one breakable portion 120c may be provided between the first and second conductor portions to2a, 102b. Moreover, the breakable portion(s) of conductor 102 may be arranged and severed in -14 -any suitable manner in order to open the first current conduction path no whilst maintaining an electrical connection between the first and second conductor portions 102a, 102b via the fusible body um (and optionally via the electrical contacts m8 and the connection contacts 1.04a, 1041) arranged at either end of the Fts131e body y 104, as appropriate).

In the absence of the second current conduction path 112 described above, the severing (shearing, breaking, separating, cutting, etc.) of current carrying conductor 102 described herein would lead to the formation of an electrical arc between the respective r0 ends of the conductor 102 (for example, between ends of first and second conductor portions /02a, /0213 and the ends of the breakable portion 102C, or between respective ends of the breakable portion) as the first current pathi to opens. An electrical arc can be formed between the ends of a conductor whenever conductors physically separate from one another. Linear displacement of the breakable p onion 102C away from the rest of conductor 102 in some example arrangements would facilitate a reduction in this electric arc (or arc discharge) by rapidly stretching the arc, thereby increasing the arc resistance. An increased arc resistance causes a corresponding increase in arc voltage and a decrease in arc current. The speed of such displacement, which occurs due to the dynamic nature of the force applied by the moveable body, could also act to increase the physical separation of the respective conductor portions quicker than with previous linear approaches, leading to more effective interruption of the electrical arc. However, particularly for high voltage applications, it can be difficult to break the arc in air alone.

By making a parallel electrical connection through a fuse or other fusible body before breaking a main (first) current conduction path through the device, the current flow through the first current conduction path is reduced before any breaking of the conductor begins. Any arcing during breaking of the conductor 102 can therefore be reduced or eliminated, and any subsequent arcing during breaking of the second current conduction path can be contained within the fuse (for example within a housing enclosing the fusible portion of the fuse and/or within the moveable body). The thermodynamic and structural stresses experienced by other components of device 100 (such as the housing, any connections or fastening, and/or other electrical components within the device) can therefore be reduced, so the need for additional structural and/or mechanical strength in these components can be reduced or removed. Smaller and cheaper devices may therefore be provided. By reducing or eliminating the arcing during breaking of the Conductor 102, the need for linear displacement of the breakabl portion to lengthen the arc can also be reduced or eliminated; again, a smaller device may therefore be provided.

Moreover, with the arrangement described herein there is no electrical current through the fusible body during normal operation of the device 100 (i.e. when the device is in the first, initial, position). The fuse is thus not fatigued during normal operation of the device, which can reduce or prevent fuse failure or nuisance tripping of the fuse. The device described herein can also be employed in high voltage and/or high current Iv applications Such as in electric vehicles (where voltages can be 80c) V to 1000 V, for example), using existing, commercially available, fuses. A wide range of current and voltage requirements can therefore be met without changing the underlying device operation, simply by providing conductors and fusible bodies of a suitable size and shape for a given current application.

A specific arrangement of the first example of device 100 (described above with reference to Figure 1) is now described with reference to Figures 4 and 5. Figure 4A and Figures 5A and 5B illustrate the device 100 in the first, initial position, where the moveable body is configured to retain the fusible body in a position in which it is electrically and physically isolated from at least one of the first and second conductor portions such that no current flows through said fusible body. In this first position, a first conduction path no is defined along the main conductor. Figure 48 illustrates the device in the third, final, position after the moveable body has been actuated, or moved, M direction 128 and the first conduction path through the conductor has been opened by the moveable body.

As can be seen in Figure 4A, with reference to Figure 5, device Two of this example comprises a housing 116, the housing arranged to enclose the first and second conductor portions 102a, 1021) and the breakable portion 102C (and optionally at least a portion of the rest of conductor 102). The conductor 102 is further provided with connection contacts 102d, 102e, which connection contacts are provided outside of housing no for connection of device 100 to one or more external electrical circuits, Connection contacts 102d, 102e may be provided with any suitable size and shape, depending on the application of device 100.

In this group of examples, the moveable bodyro6 is configured to retain the fusible body 104 such that a central, fusible, portion is enclosed by the moveable body but connection contacts 104a, 104b at either end of the fusible portion protrude beyond the moveable body. The moveable body may be con figu red to contain any arcing from melting or breaking of the fusible portion, or an additional housing may be provided to surround and enclose the central, fusible, portion (such as housing 104d described above).

In the example illustrated with respect to Figure 4, it can be seen that in the first w -position (Figure 4A) the moveable body is not in contact with the conductor 102, and the protruding parts of the fusible body are also electrically and physically isolated from the conductor 102. The fusible body can be pushed into a slot of recess in the moveable dimensioned to receive the fusible body, optionally with a press fit arrangement. The moveable body can thus enclose a central portion of the fusible body and retain the is fusible body such that the fusible body is carried by the moveable body as it moves, whilst facilitating electrical contact of the protruding portions (optionally contacts 104a, 104b) of the fusible body with the conductor 102 during operation of the device.

In this particular example, first 108a and second 1.08b electrical contacts are electrically connected to the first and second portions of the conductor, respectively, and extend in a direction opposite to direction 128, towards the fusible body. The electrical contacts 108 are positioned at either side of the moveable body and aligned with the protruding parts of the fusible body 104 (here the protruding connection contacts 104a, 104b). The fusible body 104 is brought into physical and electrical contact with the first and second electrical contacts by the movement of the moveable body 106 in direction 128 such that, in the second and third positions of the moveable body, a second current conduction path 112 is defined through the first -102a and second 102b conductor portions, the first to8a and second 108b electrical contacts and the fusible body 104 (see Figure 4.8, which illustrates the third position of the device).

The first and second electrical contacts 108 can be formed integral with the conductor 102; this can facilitate good electrical contact between components and a more robust device than if the electrical contacts were mechanically joined to the conductor 102. However, the first and second electrical contacts 108 can in sonic examples be formed independently of the conductor 102 and then coupled or joined, for example by welding, brazing, soldering, electrical adhesive, or the like; this arrangement can provide a device which is quicker and cheaper to manufacture, since less complex conductor geometries are required to be manufactured. In this example, the electrical componentsto8 are provided as rigid components (optionally with a resiliently deformable element, as discussed below), but it will be understood that in some examples they may be flexible components (for example, as described above with reference to electrical contact 108a of Figure 2).

In this group of examples, the fusible body 104 is configured as a fuse, the fuse comprising the two protruding connection contacts 104a, 104b arranged at either end r() of a fusible portion 104c. A housingia4d is also provided to enclose the fusible portion ro4c of the fuse, which portion can itself be surrounded, or at least partially enclosed by, the moveable body. The connection contacts of the fuse 104 are configured to make physical and electrical contact with the upstanding first and second electrical contacts 108a, 108b when the device is in the second position to define the second current is conduction path 112. In order to facilitate suitable protection from overload or fault currents when the device is activated, the fusible portion is optionally configured to break above a current threshold in order to open the second current conduction path and stop current flow through the device. For example, above the predetermined current threshold (which can be determined based on the application of the device KO, the heat generated by the current flow can melt or break the fusible portion in order to electrically separate the first and second electrical contacts 108a, 108b and break the second current conduction path 112. The housingio4d of the fuse and/or the moveable body is configured to contain any arcing due to breaking or melting of the fusible portion 104c when the second current conduction path 112 is opened. A safer and more robust device may therefore be provided.

In this group of examples, the first and second electrical contactsio8a, 108b are shaped or configured to receive the fusible body. In particular, the electrical contacts w8 can each be configured to receive the connection contactsioqa, 104b of the fuse (or connection contacts of any other fusible body 104 being used). This receiving (for example by providing electrical contacts 108 having surfaces which mate with the connection contacts to4a, :limb) can improve the electrical contact between the components. In the examples described herein, the fuse 104 is generally cylindrical and the electrical contacts i08 comprise a circular portion with a corresponding diameter to receive the generally cylindrical fuse, but it will be understood that any other geometry may be used. -18 -

Optionally, the first and second electrical contacts i,o8 each comprise a retaining member configured to retain the fusible body 104 once the fusible body has been forced into contact with the electrical contacts 108 by movement of the moveable body too. In this example, the electrical contacts have a closed base portion and an open top portion through which the fusible body can be pushed to bring the fusible body into contact with the closed base portion of the contact 108. For example, the electrical contacts 108 can be configured as a spring clip, optionally a Terry clip or fuse clip. The use of such a clip, or any other resilient member configured to retain the fusible body, can Iv facilitate the provision of an orientation independent device, since gravity alone will be insufficient to remove the retained fuse from the electrical contacts 108a, 1.08b and break the second current conduction path 112. The example arrangement of the electrical contacts described herein will be understood to apply equally to the electrical contactro8b described with reference to Figure 2, in examples where that component /5 is provided as a rigid, rather than flexible, contact. The use of a retaining member to retain the fusible body can also act to retain the moveable body in the third, final, position after actuation of the device by preventing further displacement of the moveable body in direction 128.

As described herein, the device 100 comprises an actuator 114 configured to actuate the moveable body from the first position to the third position. The actuator applies a force to the moveable body 106, which force is transferred, by the moveable body, to the conductor 102 in order to sever the breakable portion 102C of the conductor. Any suitable actuator may be used. Optionally, the actuator is a pyrotechnic charge configured to release gas into an ignition chamber 122 in order to exert a force on the moveable body 106. in these examples, the ignition chamber 122 can be at least partially defined by the moveable body lob. The explosive charge provided by a pyrotechnic actuator can exert a large force on the moveable body, and thus on the conductor, over a short period of time; this can facilitate quicker opening of the conduction path and so provide a device 100 with a rapid response to an overcurrent or fault condition.

When actuator 114 is a pyTotechnic actuator, the actuating force is provided by, upon ignition of the pyrotechnic actuator, the release of gas. In particular, the pyrotechnic actuator 114 comprises connector pins 114a and an igniter 114b. The ignition of the charge, or actuation of the actuator, can be in response to a signal indicating a fault or -19 -overcurrent. The connector pins 114a activate a charge inside the igniters 114b upon receipt of such an ignition signal. The ignition of the charge, and the subsequent operation of device 100, can also be in response to a collision or other external event triggering an initiation signal. In these examples, the fuse or fusible body 104 may be rated at, or just below, the normal system current, in order that once the first current conduction path is opened the second current conduction path will be opened almost immediately. This arrangement can improve safety in a collision when the device is deployed in a vehicle, for example.

Iv In this group of examples, the moveable body comprises a piston configured to apply a force to shear the breakable portion 102C of the conductor to open the first current conduction path no. The piston can be configured to contact, directly or indirectly, the conductor 102 in order to apply a force to a surface of the conductor 102 to cause the breakable portion 102C of the conductor to sever (break and/or separate). Optionally, the ignition chamber 122 is at least partially defined by the piston; by directly actuating the piston in response to a fault condition, quicker and more effective severing (breaking and/or separating) of the conductor may he provided. In this way, quicker opening of the current conduction paths, and thus isolation of electrical components, may be provided, Optionally, the conductor 102 is configured to be mechanically weaker in the breakable portion 102C of the conductor than in the first and second conductor portions 102a, to2b; this arrangement can facilitate quicker and easier severing of the conduction path 110. In some examples, the conductor 102 has a reduced width 124 (defined across the conductor 102, i.e. between two sides of the conductor and in a direction generally perpendicular to the direction in which the first current conduction path is defined) and/or a reduced thickness 126 (defined through the conductor 102 in a direction generally perpendicular to the direction in which the first current conduction path is defined) in the breakable portion as compared to a width and/or thickness in the first and second conductor portions 102a, 102b. For example, grooves or perforations may be formed in the breakable region.

In some examples, the conductor 102 has a generally uniform thickness along its length (length being defined along the conductor 102 in the direction in which the first current conduction path is defined) but has a reduced width in the breakable portion 102C. For example, one or more notches may be cut out of the sides of the conductor in the -20 -breakable region 1.02c to reduce the width of the conductor 102. Notches in a top or bottom conductor surface could also be used to reduce the conductor thickness. Additionally and/or alternatively, the breakable portion 102C of the conductor 102 may comprises a hole 118 through the conductor (here the hole 118 extends through the entire thickness of the conductor, i.e. extends fully through the conductor, but in some examples the hole may extend only partially through the conductor). Providing a hole 118 and/or notches on the side(s) and/or surface(s) of the conductor in this manner may facilitate easier severing of the current conduction path no, since the conductor is mechanically weaker in the breakable portion /02C than in the surrounding first and Iv second conductor portions to2a,102b.

In the particular example of the device 100 described with reference to Figures 4 and 5, a hole n8 is provided which extends fully though the conductor. In this example, the hole n8 is aligned with a longitudinal axis of the conductor 102, and shearable portions /5 120 are arranged between the hole n8 and respective sides of the conductor (i.e. there are two shearable portions 120 across the width of conductor 102, one either side of the hole 118). It will be understood that, depending on the size, position and geometry of the hole 118, one or more shearable portions may be arranged. or provided in the breakable portion; for example, if the hole 118 extends to a side of the conductor 102, then only one shearable. portion may be provided between the hole and the other side of the conductor 102. There may be one or more holes and/or one or more shearable portions provided in the breakable portion 102C, as appropriate. In this particular example, the shearable portions are bounded at either end by notches in the surface of the conductor proximate the moveable body 106, as can be seen in Figure 5A, but any other arrangement may be used to facilitate improved shearing of the conductor 102.

The shearable portions 120 are regions or areas of the breakable portion 102C of the conductor 102 which are configured to be sheared by the moveable body to sever the first current conduction path no. In some examples the moveable body too is configured to directly contact the conductor' at the at least one shearable portion as the moveable body moves in direction 128, in order to apply a suitable force to shear the shearable portion. When the moveable body 106 comprises a piston, an end to6a of the piston can be configured to contact the shearable portion(s) 120. This direct contact can provide for more efficient transfer of force from the moveable body to the breakable portion 102c, and can thus facilitate more effective shearing or breaking of the conductor 102 to open the first current conduction path no. As the moveable body moves in direction 128, the fusible body comes into initial contact with the electrical contacts /o8 to establish the second current conduction path 112. The moveable body continues to move until it contacts the conductor io2. The sustained downward force (from an actuator or manual actuation) applies a pressure to the breakable portion 1021i of the conductor, which pressure is increased through the use of a piston arranged to contact the shearable portions 120, as shown in Figure 5. The shearabie portions 120 of the breakable portion are eventually sheared away from the rest of Conductor 102 due to the applied pressure. The moveable body continues in to direction 128 towards the third position, pushing the separated shearable portions 102C away from the conductor and into cavity or base 130 of the housing no, as seen in Figure 48.

In this third, final, position, the insulating moveable body is disposed between the first and second conductor portions 1o2a, to2b to electrically isolate said portions after the breakable (optionally shearable) portion has fallen into the base cavity 130 of the housing n6. The upstanding electrical contacts ro8 stop further movement of the moveable body in direction 128 and act to retain the fuse, and thus the moveable body, in the third position (preventing movement in direction 128, and in a direction opposite to 128 due to the use of retaining member(s).

A further advantage of the arrangement described with reference to Figures 4 and 5 is that the shearable portions 120 facilitate breaking of the conductor in multiple places (i.e, at ends of each shearable portion 120); multiple arc columns can therefore be created. Although the arc is already reduced by the use of the second, parallel, conduction path, this arrangement can distribute any remaining electrical arc across each column, which further reduces the severity of each individual arc column and increases the rate of suppression of any arc which is formed. As such, a more effective interruption of the electrical arc can be provided. A safer and more robust electrical interrupter may therefore be provided, even for very high current and/or voltage applications (such as electric vehicles).

It will be understood that in some example arrangements not illustrated in the drawings, the breakable portion may be configured to break at a single point, for example across the width of the conductor, The regions of the breakable portion proximate the break can be configured to be pushed in direction 128 by the moving moveable body, away from the Fusible body 104 and the optional electrical contacts 108, in order to physically separate the broken ends and open the first current conduction path 110, The (insulating) moveable body can be arranged Lobe disposed between the broken ends of the breakable portion to prevent the ends coming back into contact with one another and closing the current conduction path. The ends can be retained in this position by the insulating moveable body106, which is itself retained in the third position by the retention of the fusible body 104 by the retaining members formed by the electrical contacts 108. A safer device may therefore be provided.

(0 With reference to Figure 6, example uses of electrical interrupter -to0 (of the first and/or second example described above, or of any other device 100 configured to make an electrical conduction path through a fusible body-before breaking a parallel electrical conduction path through a conductor) are described. In the example of Figure 6A, device too is incorporated within a powertrain 620. In particular, powertrain 620 can is be a powertrain for a vehicle 600; in regard to a vehicle (e.g, a motor vehicle, a ship or boat, or a plane, etc.), a powertrain encompasses the main components that generate power and deliver it to the road surface, water, or air. This includes the engine, transmission, drive shafts, and the drive wheels (or other drive mechanism, such as a propeller). In an electric or hybrid vehicle, the powertrain 620 also includes battery 630 and an electric motor, for example. Device 100 may be connected, -Oa the connection contacts und, 102e of the conductor /02, to an electrical circuit 650 within vehicle 600, which electrical circuit may optionally include the battery 630. Alternatively, in the example of Figure 6B, device 600 is employed for another use within vehicle 600, which may be an electrical vehicle.

In both Figure 6A and 6B, an ignition signal may be provided to connector pins 114a of the pyrotechnic actuator 11,4 from a remote controller, or a remote power distribution unit, 610 within the vehicle 600. Such an ignition signal may be issued in response to an external event. For example, when the device 100 is connected to a battery 630 installed in the vehicle 600, an ignition signal maybe sent to the pyrotechnic actuator 114. in response to a collision of the vehicle; activation of the charge inside the igniter 114 can cause the breakable portion 102c to be severed (broken and/or separated) from the first and second conductor portions 102a, 102b in order to open the electrical circuit 650 and prevent the flow of current through the battery 630. Such art arrangement can improve safety in the event of a collision. Alternatively, device too and remote controller oto can form a system which can be deployed in any other -23 -application where breaking of a circuit is required, such as in response to an overcurrent condition.

With reference to Figure 7, a method 700 for opening a current conduction path using an electrical interrupter too (for example, the device.100 of the first aspect) is described.

At step 710, the rethod comprises moving a moveable body 106 from a first, initial, position towards a third, final, position (in a direction 128), the moveable body carrying Iv a fusible body 104 with it as it moves in direction t28. Optionally, the moveable body is configured to move in response to an actuating force from an actuator. Actuating an actuator optionally occurs in response to a collision or other external event triggering an initiation or ignition signal. Actuating the actuator optionally comprises igniting a pyrotechnic actuator, which ignition can be in response to a collision or other external event triggering an initiation signal, which signal is received by the pyrotechnic actuator. Any other trigger can be used for actuating the actuator, depending on the application of the device 100. It will be understood that, in some examples, moving the moveable body is in response to a manual actuation.

As the moveable body moves, at step 720, the fusible body carried by the moveable body is electrically connected to at least one of first and second portions of a conductor 102, the conductor defining a first current conduction path 110 in normal operation of device 100. The electrical connection to the first and/or second conductor portions 102a, 102b may occur simultaneously, or one after another', depending on the arrangement of the device 100. At step 730, the moveable body is in a second (intermediate) position and the method further comprises defining a second current conduction path through the fusible body (as a result of the electrical connection at step 720), the second current conduction path connected in parallel to the first conduction path. In examples where the fusible body is only connected to one of the first and second portions of the conductor 102, the fusible body is already electrically connected to the other of the first and second portions of the conductor 102 in order to define the current conduction path at step 730.

As the moveable body 106 continues to move in direction 128 towards the third (final position), pressure is exerted (either directly or indirectly) on a breakable portion 102C of the conductor. Optionally, the pressure is from high-pressure gas released into the ignition chamber upon actuation of a pyrotechnic actuator. This released gas exerts a pressure (either directly or indirectly) on the moveable body. The moveable body is aligned with the breakable portion 102C and is arranged to move in the direction 128 towards the breakable portion upon actuation by the actuator, i.e. during the moving at step no. Optionally, the moveable body is accelerated downwards due to the high pressure gases released by the pyrotechnic actuator, or from another form of dynamic actuation or may simply be forced continually downwards by another form of (optionally linear) actuator.

/0 At step 740, as the moveable body MOWS in direction 128, the moveable body 106 severs the breakable portion 102c of the conductor, which breakable portion is arranged between (and optionally connects) the first and second conductor portions, to open the first current conduction path no. As the moveable body moves (or is pushed / displaced) further in direction 128, at step 750 the severed breakable portion is is displaced by the moveable body 106; the moveable body is disposed between the first and second portions of the conductor, arranged in the place of the breakable portion. In some examples, the edges of the breakable portion are sheared at step 750, and the sheared breakable portion is broken away from, and thus fall away from, the main body of conductor 102 by the movement of the moveable body. In other examples, only a single break may be made in the breakable portion, and the breakable portion either side of the break may be forced in direction 128 by the moving moveable body, away from the fusible body 104.

At step 760, method 700 further comprises breaking the fusible body to open the second current conduction path 112 and stop current flow through the device 100. The fusible body 104 can be arranged to break at any predetermined current, depending on the size and shape of the fusible portion, in order to interrupt the electrical circuit.

It is noted herein that while the above describes various examples of the isolating device of the first aspect, these descriptions should not be viewed in a limiting sense.

Rather, there are several variations and modifications which may be made without departing from the scope of the present invention as defined in the appended. claims.

Claims

-25 -Claims An electrical disconnect device (i00), comprising: a conductor (102) comprising first (l02a) and second (i02b) portions and a breakable portion (102c) arranged between the first and second portions and defining a first current conduction path (no) through the breakable portion; a fusible body (104); and a moveable body (j06) for severing the breakable portion ot the conductor to open the first current conduction path, wherein the moveable body is configured to carry the fusible body such that, before the breakable portion of the conductor is severed, the fusible body is brought into electrical contact with at least one of the first and second portions of the conductor to define a second current conduction path (112) through the fusible body; the second current conduction path connected in parallel to the first conduction path.
2. The device of claim 1, wherein the moveable body is configured to bring the fusible body into electrical contact with both the first and second conductor portions.
3. The device of claim 2, further comprising: first (i08a) and second (i08b) electrical contacts, the first and second electrical contacts electrically connected to the first and second portions of the conductor, respectively, wherein the fusible body is brought into physical and electrical contact with the first and second electrical contacts and the second current conduction path is defined through the first and second electrical contacts and the fusible body.
4. The device of claim 3, wherein the first and second electrical contacts are integral to the conductor.
5. The device of claim 3 or claim 4, wherein the first and second electrical contacts are configured to receive the fusible body.
6. The device of claims. wherein the first anc seco.n.d electrical contacts each comprise a retaining member configured to retain the fusible body.
The device of claim i, wherein the fusible body is in electrical contact with one of the first and second conductor portions, and wherein the moveable body is configured to bring the fusible body into electrical contact with the other of the first and second conductor portions.
8. The device of any preceding claim, wherein the moveable body comprises a piston configured to apply a force to shear the conductor in the breakable portion in order to open the current conduction path.It) 9. The device of claim 8, wherein the breakable portion of the conductor comprises a hole (n8) through the conductor and at least one shearable portion (120) arranged between the hole and a side of the conductor, and wherein an end (106a) of the piston is configured to contact the at least one shearable portion.is in. The device of any preceding claimfurther comprising an actuator (114) configured to actuate the moveable body.11. The device of claim to, wherein the actuator is a pyrotechnic charge configured, upon ignition, to release gas into an ignition chamber (122) in order to exert a force on the moveable body.12. The device of claim 11, wherein the ignition chamber is at least partially defined by the moveable body.13. The device of any preceding claim, wherein the moveable body is configured to be disposed between the first and second portions of the conductor after severing of the breakable portion.14. The device of any preceding claim, wherein the moveable body is formed fn an insulating material.15. The device of any preceding claim, wherein the fusible body is configured to break above a current threshold in order to open the second current conduction path and stop current flow through the device.16. The device of any preceding claim, the fusible body comprising two connection contacts (l04a, 10413) configured to electrically connect to the first and second conductor portions, respectively, optionally wherein We connection contacts are disposed at either end of the fusible body.17. The device of any preceding claim, wherein the fusible body is a fuse.18. A system comprising: the device (i00) of any preceding claim; and It) a controller (61.0) arranged to control movement of the nioveahie body.139. A vehicle (600) comprising the device (i00) of any one of claims i to 17 or the system of claim 18, optionally, wherein the vehicle is an electric vehicle./5 20. A method (700) of operating an electrical disconnect device (too), comprising: moving (710) a moveable body from a first position towards a third position via an intermediate second position, wherein in the first position a first current conduction path is defined along a conductor, the conductor comprising first and second portions and a breakable portion arranged between the first and second portions; electrically connecting (720) a fusible body carried by the moveable body to at least one of the first and second portions of the conductor; defining (730) a second current conduction path through the fusible body when the moveable body is in the second position, the second current conduction path connected in parallel to the first conduction path; after defining the second current conduction path, severing (740), with the moveable body, the breakable portion of the conductor to open the first current conduction path.21. The method of claim 20, further comprising; severing (760) the fusible body to open the second inept conduction path and stop current flow through the device.22. The method of claim 20 or claim 21, further comprising: after severing the breakable portion, disposing (750), in the third position, the moveable body between the first and second portions of the conductor.23, The method of any of claims 20 tO 22, wherein electrically connecting the fusible body comprises: electrically connecting respective electrical contacts of the fusible body to the least one of the first and second portions of the conductor.