GB2595313A - Disconnect device with magnetic switch - Google Patents

Abstract

An electrical interrupter 100 comprises a conductor defining a current conduction path, a pyrotechnic actuator 116 which when activated breaks the conductor at a breakable region 104a, and a magnetic switch 102. The magnetic switch comprises a first magnetic circuit having a fixed portion 110 and a movable plate 112 for confining a first magnetic flux, and a means for varying the first flux. When the first flux is at or above a threshold, the movable plate is magnetically coupled to the fixed portion; when the first flux falls below the threshold, the plate moves away to apply a force to activate the actuator. The first flux may be generated by a permanent magnet 108 and may be varied by an electromagnet. The conductor may comprise a switching region 104b; the electromagnet comprises a second magnetic circuit arranged around this switching region which confines a second magnetic flux (124, figure 4A) generated by the flow of current. The second flux may oppose the first flux such that an increase in the second flux due to an overcurrent in the conductor reduces the first flux to below the threshold to open the switch.

Description

Disconnect device with magnetic switch

Field

This relates to opening, or interrupting, a current conduction path. in particular, this relates to a device comprising a magnetic switch for opening a current conduction path, and a method of operating the device to open said current conduction path.

Background

Current conduction paths can be opened by breaking a continuous conductor which io 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.

Such devices are typically controlled via a central control unit, which senses a fault condition (such as an overcurrent or collision) and provides a command to the actuator in order to disconnect the circuit. This approach can lead to a slower response time whilst signals are processed by the control unit, and the electrical health of the actuator may need to be routinely monitored to ensure the device operates properly when such signals are provided to it.

Ills 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

The following specification relates to an electrical interrupter or disconneetor device, which device allows for disconnection or interruption of an electrical circuit in response o to an overcurrent or collision condition, 'without requiring (or relying on) a signal from a central control unit. Rather than using magnetics to connect a circuit to electrically activate an actuator, for example, the magnetic switch is used to control a mechanical activation of an actuator (i.e. to activate an actuator byway of a mechanical force).

In a first aspect, an electrical disconnect device is provided as defined in appended ndependent apparatus claim 1, 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.

Described herein is an electrical interrupter device, comprising: a conductor comprising a breakable region and defining a current conduction path through the breakable region; an actuator configured to, upon activation, break the conductor in the breakable region to open the current conduction path; and a magnetic switch arranged to apply a force to activate the actuator. By using a mechanically operated, or activated, actuator, a device with more reliable operation may be provided. By removing Iv electrical ignition or activation elements, the use of a mechanically activated actuator also removes the need to routinely check the electrical health of the actuator, which can reduce maintenance costs. Any suitable method of breaking the breakable region of the conductor can be used to open the current conduction path.

/5 As described herein, the magnetic switch comprises: a first magnetic circuit arranged to confine a first magnetic flux, the first magnetic circuit comprising a fixed portion and a moveable plate, and means for varying the first magnetic flux. When the magnetic -flux (through the moveable plate) is at or above a predetermined threshold, the moveable plate is magnetically coupled to the fixed portion (i.e. the moveable plate is held in contact, whether direct or indirect, with the fixed portion of the magnetic circuit by magnetic attraction). When the magnetic flux (through the moveable plate) falls below the predetermined threshold, the moveable plate moves away from the fixed portion to apply the force. The use of a magnetic switch can enable provision of a device which is responsive to mechanical inputs, such as those experienced in a collision, without requiring receipt of electrical signals before any operation occurs. By providing a device which operates responsive to variation of the first magnetic flux, a self-sensing interrupter device can also be provided, as described herein in more detail. A quicker, more responsive, interrupter device may therefore be provided.

in some examples, the magnetic switch comprises a permanent magnet, wherein (at least a portion of) the first magnetic flux is generated by the permanent magnet. Optionally, the permanent magnet is fixed, and is configured to generate a fixed portion of the first magnetic flux. In other examples, the permanent magnet is moveable, and movement of the permanent magnet is configured to vary the first magnetic flux. When the permanent magnet is fixed, the means for varying the first magnetic flux can comprise one or more further magnetic components. Optionally-the means for varying the first magnetic flux comprises an electromagnet, the electromagnet configured to contribute a variable portion of the first magnetic flux. In particular, the electromagnet(s) can be configured to vary the first magnetic flux to reduce the magnetic flux through the moveable plate below the predetermined threshold, to thereby reduce the magnetic attraction between the moveable plate and the fixed portion and open the magnetic switch.

As discussed herein, the magnetic flux through the moveable plate is considered to be the first magnetic flux (as produced in the absence of any flux generated by the means Iv for varying the magnetic flux, optionally as produced by the fixed permanent magnet), plus any contribution to the first magnetic flux from said means for varying the magnetic flux (which contribution may increase or decrease the first magnetic flux). In other words, it is the resulting, or net, magnetic flux through the magnetic plate which is compared to the predetermined threshold and determines whether the magnetic switch opens or not. For example, the fixed portion of the first magnetic flux generated by the permanent magnet can be decreased by the variable contributions from the electromagnet(s) such that the total first magnetic flux (or net magnetic flux) through the moveable plate is below the predetermined threshold.

In some exarnpl es, the conductor further comprises a switching region, and the electromagnet (the varying means of the magnetic switch) comprises a second magnetic circuit arranged around the switching region of the conductor, the second magnetic circuit arranged to confine a second magnetic flux generated in response to the current flowing through or along the current conduction path (defined through the switching region as well as the breakable region). In particular, part of the fixed portion of the first magnetic circuit forms part of the second magnetic circuit such that the first and second magnetic fluxes at least partially overlap to reduce the first magnetic flux through the moveable plate. In other words, the current flowing through the conductor is used to form an electromagnetic control the opening of the magnetic switch. A self-sensing device may therefore be provided, which can reduce response time of the device.

In some examples, the conductor and magnetic circuits can be configured such that the second magnetic flux is configured to increase in dependence on an increase in current along the current conduction path, wherein the increase in the second magnetic flux is configured to cause a related decrease in the first magnetic flux. The device can -4 -therefore operate independently by opening the magnetic switch in response to an overcurrent conduction (i.e. without waiting for one or more external signals to open the switch), which can reduce response time of the device in such a fault conduction, In some examples, an air gap can be provided in the second magnetic circuit. Optionally, the air gap is provided separate from the fixed portion of the first magnetic circuit (which forms part of the second magnetic circuit). 'This air gap increases the reluctance of the path through the second magnetic circuit, *Erich acts to reduce the second magnetic flux generated for a given current along, or through, the current iv conduction path. The size of the air gap can be adjusted to change the current at which the first magnetic flux will be reduced below the predetermined threshold, i.e. to change the current at which the magnetic switch opens. The air gap can thus facilitate fine tuning of the overcurrent condition, allowing use of the magnetic switch principles described herein for different current ratings and applications. ;Optionally, the moveable plate is arranged to apply the force in a first direction, wherein the breakable region is offset from the switching region in the first direction. In other words, a substantially C shaped conductor can be provided, which can facilitate the provision of a more compact device. ;In some examples, the electromagnet (the varying means of the magnetic switch) additionally or alternatively comprises a coil arranged around a portion of the first magnetic circuit, the coil configured to generate a third magnetic flux within the first magnetic circuit which overlaps the first magnetic flux. A direction of the first magnetic flux is opposite a direction of the third magnetic flux in order that the third magnetic flux reduces the first magnetic flux through the moveable plate. In this way, the magnetic switch can be controlled from a central control unit; signals from the control unit can apply a current to the coil, or can cause a current to be applied to the coil. The magnetic switch can therefore be opened in response to a fault condition other than an overcurrent or collision through receipt of external signals. A more robust device may therefore be provided. ;The moveable plate can move away from the fixed portion toward the actuator under the influence of gravity, or can be pushed and/or pulled away from the fixed portion by one or more biasing members, as appropriate. In some examples, a first portion of the moveable plate is magnetically coupled to (i.e. held in place through magnetic -5 -tion with) the fixed portion, and a second portion of the moveable plate is rotatably coupled to the fixed portion. For example, the second portion can be configured as a hinge, or in any other suitable arrangement. When the first magnetic flux falls below a predetermined threshold, the moveable plate can rotate around the second portion, and the first portion of the plate can fall away to apply the force. A more controlled and repeatable motion of the moveable plate may therefore be provided. ;In some examples, the magnetic switch comprises a biasing member coupled to a third Iv portion of the moveable plate, the second portion arranged between the first portion and the third portion. The biasing member is configured to urge the moveable plate to rotate around the second portion to move the first portion of the moveable plate away from the fixed portion to apply the force. The biasing member can be a resiliently deformable member, optionally a spring. The resiliently deformable member may be is arranged in tension, configured to pull the third portion in a second direction to urge the first portion in the first, opposite, direction. The resiliently deformable member may be arranged in compression, configured to push the third portion in the second direction to urge the first portion in the first, opposite, direction. Any other suitable arrangement may be provided, as appropriate. The use of one or more biasing members can facilitate provision of an orientation independent device. ;The biasing member can be configured to urge the moveable plate to rotate around the second portion when the first magnetic flux is below the predetermined threshold. In other words, the biasing member is configured to apply a biasing force to the moveable plate (in the first direction) which is less than a magnetic force (in the second direction) magnetically coupling the moveable plate to -the fixed portion when the magnetic flux through the moveable plate is at or above a predetermined threshold. When the (net) magnetic -flux through the moveable plate decreases below the predetermined threshold, the biasing force is greater than the magnetic force, and the magnetic switch opens. In some examples, the biasing force can be gravity only. There is thus an interplay between the biasing force and the magnetic force (which is dependent on the net flux through the moveable plate); manipulation of the magnetic force with one or more electromagnets (or other varying means) can control opening of the magnetic switch. The principles of the magnetic switch described herein can thus be applied to any current rating or application, by adjusting the biasing force (and so the predetermined threshold), and/or by adjusting the variation of the first magnetic flux. ;The magnetic force can also be overcome by the moment of inertia produced in the moveable plate by one or more impulse or impact forces, such as those experienced in a collision. An independently operated device may therefore be provided; since no external trigger signal is required, the device can respond more quickly to collisions. A quicker and more responsive device may therefore be provided. ;In some examples, the actuator(configured to be) directly activated with die force applied by moveable plate. In other examples, the actuator comprises a piezoelectric iv component, wherein the moveable plate is configured to apply the force to the piezoelectric component in order to generate, by the piezoelectric component, an electrical signal to activate the actuator. Optionally, the actuator is a pyrotechnic actuator. ;is In the specification, there is provided a method of opening a current conduction defined along a conductor having a breakable region. The method comprises: generating a first magnetic flux; confining a first magnetic flux within a first magnetic circuit comprising a moveable plate and a fixed portion; magnetically coupling the moveable plate to the fixed portion when the first magnetic flux is at or above a predetermined threshold; reducing the first magnetic flux through the moveable plate to below the predetermined threshold; applying, with the moveable plate (which moves away from the fixed portion in response to reducing the first magnetic flux through the moveable plate), a force to activate an actuator; activating the actuator with the applied force; and breaking the conductor in the breakable region to open the current conduction path. ;Optionally, generating the first magnetic flux comprises generating the first magnetic flux with a permanent magnet. Optionally, reducing the first magnetic flux (i.e. reducing the net flux through the moveable plate) comprises reducing the first magnetic flux using an electromagnet. ;In some examples, reducing the first magnetic flux using an electromagnet comprises: arranging a second magnetic circuit around a switching region of the conductor; and confining a second magnetic flux within the second magnetic circuit, the second magnetic flux generated in response to current flow throtigh the current conduction path. Part of the -fixed portion of the first magnetic circuit forms part of the second magnetic circuit such that the first and second magnetic fluxes at least partially overlap to reduce the net magnetic flux through the moveable plate. ;Additionally or alternatively, reducing the first magnetic flux using an electromagnet comprises: arranging a coil around part of the first magnetic circuit; applying a current to the coil; and confining a third magnetic flux within the first magnetic circuit, the third magnetic flux generated in response to the applied current, wherein a direction of the first magnetic flux is opposite a direction of the third magnetic flux in the moveable A system is provided comprising a device as described above and a controller arranged to provide a signal to an 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 Is applications, for example. ;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 coil (to generate the third magnetic flux). 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 ease of an accident. ;This may improve safety. ;It will be understood that any of the features described above with reference 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: Figure IA illustrates a perspective view of a device in accordance with an example of the first aspect; Figure J.B illustrates a side view of the device of Figure iA; and Figure ik; illustrates a front view of the device of Figure 1.13; Figure 2 illustrates an example magnetic switch of the first aspect in a first (closed) position (Figure 2A) and a second (open) position (Figure 2B); -8 -Figure 3A illustrates a cross-sectional view of an interior of the device of Figure PC, and Figure 3B illustrates a dose up of the magnetic switch within the dashed box of Figure 3A; Figure 4 shows variations in the magnetic fluxes through a magnetic switch as described herein: Figure 4A shows a schematic illustration of first and second magnetic fluxes during normal operation of an example implementation of the device of the first aspect, and Figure 4B shows a schematic illustration of the net or resultant flux in the normal operation of Figure 4A; Figure 4C shows schematic illustration of first and second magnetic fluxes during an overcurrent condition of the device of the first aspect, Iv and Figure 4D shows a schematic illustration of the net or resultant flux in the over current condition of Figure 4C; Figure 5 illustrates example operation of an example of the device of the first aspect: Figure 5A illustrates interplay of the first and second magnetic fluxes; Figure 5B illustrates interplay of the first and third magnetic fluxes; and Figure 5C illustrates /5 opening of the magnetic switch when the (net) magnetic flux through a moveable plate of the switch is below a threshold value; Figures 6A and 6B illustrate a vehicle comprising the device of the first aspect; and Figure 7 illustrates a method in accordance with the second aspect. ;Detailed Description ;With reference to Figure 1 (Figure -IA and Figureth) and Figure 2, a magnetic switch 102 of an electrical interrupter device 100 (such as an isolator, disconnector or other form of electrical interrupter) for opening a current conduction path is described. Device 100 comprises a conductor 104 defining a current conduction path, an actuator (not shown) configured to break the conductor, and magnetic switch 102, which is configured to activate the actuator. ;The conductor comprises a breakable region 104a and a switching region 10413 (located at the portion of conductor 104 within the respective dashed boxes cif Figure 2B) through which conductor regions the current conduction path is defined; the breakable regiontoa is configured to be broken in any suitable manner to open the current conduction path. Conductor la" is electrically coupled to an external electrical circuit such that in normal operation of the device (when the current conduction path is closed), current is able to flow through the device 100 via the conductor 104 (i.e. along the current conduction path). -9 - ;Conductor 104 is in this example shaped substantially Eke a C. such that the breakable region 104a is offset from the switching region 104b along a first direction 152. This can help to make the device too more compact, and can in some arrangements alloy,' for more efficient force transfer. ;As can be seen in Figure 1, device 100 of this example comprises a housing 150, the housing arranged to enclose at least the breakable region:104a and the switching region 104b (and optionally at least a portion of the rest of conductor 104). The conductor 104 Iv is further provided with two connection contacts -talc, which connection contacts are provided outside of housing 150 for connection of device too to one or more external electrical circuits. Connection contacts to4c may be provided with any suitable size and shape, depending on the application of device 100. ;is The magnetic switch 102 comprises a first (closed) magnetic circuit configured to confine a first magnetic flux 106 (the flux is illustrated by the dotted lines in Figure 2, the arrows indicate the direction of the flow of flux). A magnetic circuit is made up of one or more closed loop paths containing a magnetic flux, such as first magnetic flux 106. The flux is usually generated by permanent magnets or electromagnets, and is confined to the path by the use of magnetic cores (typically consisting of ferTornagnetic materials like iron, although there may be air gaps or other materials in the path). In the examples described herein, a fixed portion of the first magnetic flux (i.e. the magnetic flux too illustrated in Figure 2A) is generated by a fixed permanent magnet 108, which generates magnetic flux from N to S (North pole to South pole) but any other suitable source could be used to generate at least a portion of the first magnetic flux. ;Magnetic flux always forms a closed loop, but the amount of flux in each part of the path or loop depends on the reluctance of the materials forming the magnetic circuit; reluctance is akin to resistance in an electrical circuit, and magnetic flux is correspondingly higher in low reluctance materials. The amount of magnetic flux within a circuit, and the particular path, can therefore be manipulated by varying the structure of the circuit. For example, air has a high reluctance, while easily magnetized materials such as soft iron have a low reluctance. Areas of higher magnetic flux exert a larger attractive force on other magnetic materials than do areas of lower flux. In other -10 -words, the amount of magnetic attraction between two magnetic components can be adjusted by varying the magnetic flux through said components. ;In the examples described herein, the first magnetic circuit of device 100 (arranged to confine the first magnetic flux 106) comprises a fixed portion no and a moveable plate 112. The fixed portion no is here made of three different components -noa, nob, noc (see Figure 313). In the example of Figure 2A, the magnetic flux generated by magnet 108 is sufficient to magnetically couple the moveable plate 112 to the fixed portion 110 of the circuit. In other words, the flux 106 through the moveable plate is i() sufficient to cause sufficient magnetic attraction between the moveable plate 112 and the fixed portions no of the circuit to hold the moveable plate in contact with the rest of the magnetic circuit. The magnetic force pulls the moveable plate 112 in a second direction /54 opposite to first direction 152 and prevents the moveable plate 112 falling or dropping away from the fixed portion in direction 152. ;The magnetic switch 102 further comprises means for varying the first magnetic flux too (not shown here), which means can be considered to contribute a variable portion to the first magnetic flux 106. Said means could be a moveable permanent magnet (such as magnet 108, when the magnet is not fixed), or any other combination of one or more electromagnet(s), as appropriate. The varying means can cause a reduction in the magnetic flux flowing through the moveable plate 112 by reducing the first magnetic flux to6 generated by the magnet. This reduction can be by any suitable means, and some examples will be described below in more detail. When the net magnetic flux through moveable plate 112 is at or above a predetermined threshold, the moveable plate is magnetically coupled to the fixed portion (as in Figure 2A), but when the magnetic flux through the moveable plate 112 is below the predetermined threshold, the moveable plate moves away from the fixed portion no in direction 152 to apply a force to activate the actuator. Moveable plate 112 can be formed of a high permeability material, to increase the magnetic response of the plate to applied magnetic fields. ;The threshold can be predetermined (or selected) based on the balance between the magnetic force (in the second direction 154) acting to magnetically attract the moveable plate 112 to the fixed portion 110, and a biasing or urging force acting on the moveable plate to urge it to move in the first direction 152. When these forces are balanced, or the magnetic force is greater than the biasing force, the magnetic switch is closed (Figure aA). When the first magnetic flux lo6 is decreased below a threshold at which the forces balance, then the biasing or urging force is greater than the magnetic force and the moveable plate moves in direction 152. The biasing force can be gravity (acting in direction 152), or a combination of gravity and a force from one or more biasing members, or the force from biasing member(s) only (depending on the device orientation). ;In this example, a first portion 112a of the moveable plate is magnetically coupled to the fixed portion 110, and a second portion 1121) of the moveable plate is rotatably coupled (for example by a hinge °joint) to the fixed portion 110. A biasing member 114 (here a xv spring under tension, arranged to apply a biasing force in direction 154) is coupled to a third portion 112C of the moveable plate, the second portion arranged between the first portion and the third portion. When the magnetic flux -ma is below the predetermined threshold for the device 100 (different device configurations can have different selected or predetermined thresholds), biasing member 114 can urge the moveable plate 112 to /5 rotate around the joint or hinge at second portion 112b (by pulling upwards on the third portion 112C in direction 154) to cause the first portion 112a to move away from the fixed portion 110 of the magnetic circuit (in direction 152). The magnetic switch 102 is thus opened, as shown in Figure 2B, and the moveable plate can apply a force in direction 152 to activate the actuator (not shown), It will be understood that any other suitable biasing member arTangement can be used, or no biasing member may be used. ;The means for varying the flux to open the. sitch as in Figure 2B can be any suitable electromagnet, or movement of the permanent magnet 108. Additionally or alternatively, the moment of inertia from an impact force can be sufficient to overcome the magnetic attraction between the fixed portion 110 and the moveable plate 112. An initial movement of the moveable force in response to such an impact introduces an air gap into the first magnetic circuit. This region of high reluctance (low permeability) reduces the flux -106 in the first magnetic circuit (as illustrated by the smaller arrows in Figure 2B as compared to Figure i2A), which effect causes the moveable plate 112 to move further away from the fixed portion, thus further increasing the reluctance in the circuit. Thus, during a collision, crash or impact, the device 100 can independently sense the event and disconnect the circuit to Which the device is connected without waiting for a command from a central control unit. This can help to reduce the response time of the device. ;Specific implementations of the magnetic switch described with reference to Figure 2 will now be described below with reference to Figures 3 to 5. ;Figure 3 illustrates device 100 including magnetic switch 102, conductor 104 and an actuator 116. In some examples, the actuator 116 is (configured to be) directly activated with the force applied by moveable plate 112 when the switch 102 opens. In other examples, the actuator comprises a piezoelectric component 120, wherein the moveable Plate 112 is configured to apply the force to the piezoelectric component 120 in order to generate, by the piezoelectric component, an electrical discharge or electrical signal to iv activate the actuator 116 (the mechanical force applied to the piezoelectric component generates an electrical current within the component 120, which current be supplied to the actuator 116 to activate it). ;As described herein, the actuator 116 is configured to apply a force to conductor 104 in order to break the conductor in the breakable region 104a of the conductor. Any suitable actuator maybe used. Optionally, the actuator nfi is a pyrotechnic charge or actuator configured to release gas into an ignition chamber i8 in order to exert a force on a moveable body or piston (which force is transferred; by the moveable body, to the breakable region 1.042 of the conductor 1041. In these examples, the ignition chamber 118 can be at least partially defined by the piston. The explosive charge provided by a pyrotechnic actuator can exert a large force on the piston, 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. ;The first magnetic circuit is made up of components noa, nob, Hoc and 112, as described above. However, in the example of Figure 3B, a second magnetic circuit is also provided. In particular, the means for varying the first magnetic flux comprises an electromagnet, comprising a second magnetic circuit arranged around the switching region 104b of the conductor. As a DC current flows along the conduction path (from an external circuit to winch the device is connected by connection contacts 104c). a second magnetic flux 124 generated in response to the current conduction path is confined within the second magnetic circuit. ;Component nob of the fixed portion of the first magnetic circuit forms part of the second magnetic circuit, such that the first and second magnetic circuits are coupled. ;Due to this coupling, the first and second magnetic fluxes at least partially overlap within the first and second circuits, which overlap can act to increase or decrease the first magnetic flux 106 through the moveable plate, depending on the current strength and/or direction. The interplay of these two generated fluxes is described further with reference to Figure 4, which schematically illustrates the magnitude and direction of the first and second magnetic fluxes in one example arrangement; in this example, DC current flow through the switching region 1.04b is orientated out of the page (see the dot in Figure 313). ;The rest of the second magnetic circuit, as illustrated in Figure 313, comprises xv components t22a and 122b and an air gap 126. The air gap 126 reduces the magnetic flux generated by the applied current by introducing a low permeability region within the circuit. Since the properties of the air gap 126 influence the magnitude of the second magnetic flux generated around conductor region 104b, variable sized air gaps can be used to adjust the current at which the magnetic switch 102 is activated. An end user may therefore specify one or more physical requirements of the first and second magnetic circuits in order to achieve the overcurrent sensing limit required for a particular application, Figure..01 illustrates example first and second magnetic flux paths through the device of Figure 313 during normal operation of device too, i.e. when the current through the conductor 104 is at an expected, normal, level. These fluxes are shown for illustrative purposes, without considering their interaction. The first magnetic flux -J.06, generated by a permanent fixed magnet (not shown), is represented by the dashed lines. The second magnetic flux 124, generated by the current through the conductor 104, is represented by the solid lines. The direction of the flux path is indicated by the arrows, and the strength of the flux is illustrated by the thickness of the lines. The air gap 126 is defined such that, when the rated current flows in conductor 104, the second magnetic flux 124 does not significantly reduce the first magnetic flu x106, The first magnetic flux remains sufficiently high through the moveable plate 112 that the moveable plate is magnetically coupled to the fixed portion no and the switch 102 is closed. ;It can be seen that the fluxes can take different, parallel, paths when the first and second magnetic circuits overlap (or are otherwise coupled). The amount of flux along each path is dependent on the magnetic reluctance of the paths (analogous to electrical resistance and current in an electrical circuit). Magnetic reluctance depends on the geometry and composition of the components of the magnetic circuit(s), and the -14 -components can be designed such that the path through components ima, imc, 112 can have a magnetic reluctance higher (optionally, in some examples, 600% to 700% higher) than that through -nob, and the path through component nob can have a reluctance lower than that through components n2a,112b and the air gap 126 (air has a high reluctance). ;Consequently, in normal operation, the majority of flux 106 (generated by permanent magnet 108) is confined to the first magnetic circuit (components noa, nob, noc and 112), with only a small proportion travelling through the part of the second magnetic iv circuit (components 112a, 112b, 126) which is coupled to the first magnetic circuit by component nob (because more flux will take the lower reluctance path nob than takes the higher reluctance path n2a, 112b, 126). Similarly, the majority of second magnetic flux 124 is confined to the second magnetic circuit, with only a small proportion travelling through the first magnetic circuit (more flux will take the lower reluctance is path nob than takes the higher reluctance path noa, noc, 112). In this regard, the magnetic circuits can be considered as analogous to electrical circuits, where the reluctance is the resistance of each branch and the -flux is the current in each branch. ;The net flux 1.60a in each part of the first and second magnetic circuits during normal operation is illustrated in Figure 413; the net or resultant flux 160a is the sum of the first and second magnetic fluxes of Figure 4A, and where the fluxes oppose each other, the resultant flux in that component is reduced (rather than increased, as it is when the fluxes are in the same direction). The direction of the resultant flux is indicated by the direction of the arrows in Figure 413. It can be seen that, during normal operation of the device 100, the magnetic flux is dominated in the first magnetic circuit by the contribution from the permanent magnet -108, and the magnetic flux in the second magnetic circuit is dominated by the contribution from the current flowing along or through the conductor 104. ;Figure 4C illustrates example first and second magnetic flux paths through the device of Figure 3B during an overcurrent or short circuit of device 100. As the current increases in the conductor 104, for example due to such a short circuit or other overcurrent condition, the generated second magnetic flux 124 correspondingly increases as compared to the normal operation, as can be seen from Figure 4C (the width of the lines is greater than in Figure 4A to illustrate the greater flux strength). The first magnetic -flux 106 generated by the permanent magnet 108 does not change (the width of tbe lines is the same as in Figure 4A), since magnet 108 is here a fixed permanent magnet. In Figure 4C, the different fluxes 104,124 are shown in an overcurrent condition for illustrative purposes, without considering their interaction. ;In practice, the increase in the second magnetic flux 124 can reduce the net magnetic flux in the circuit components where the respective flux paths are in opposite directions, such that in some components the net flux is less than during the normal operation of Figure 4B. This red-I:ail/II in the net flux 160b through the magnetic circuits during an overcurrent condition can be seen with reference to Figure 4D, which Iv shows the net flux resulting from the interaction of the fluxes of Figure 4C; whilst the direction of the net flux 160b through components noa, noc and 112 remains the same as the net flux 160a in Figure 4B, the magnitude of the net flux thob in the overcurrent condition of Figure 4C is reduced due to the opposition from the second magnetic flux 124. ;This "opposition" can be understood by considering the magneto five forces (NIMF) applied to the components of the First and second magnetic circuits. When an MAIF is applied to an iron core of the components of the magnetic circuit(s), dipoles of the elements within the core will align parallel with the direction of the force, allowing the flux to pass through the component. A higher MTVIF will align more dipoles with the direction of the flux. Therefore, as the current through the conductor 104 increases, increasing the MAW generated by the passing of the current through the conductor, more of the dipoles in the cores of the magnetic circuits will align towards the second magnetic flux from the conductor. However, the MAL IF of the permanent magnet 108 does not change. If the current through the conductor continues to increase, and so increase the strength of the conductor electromagnet, fewer and fewer dipoles remain to be aligned by the MMI1 of the permanent magnet to allow the first magnetic flux too to pass through the cores of the circuits. Therefore, less of the flux generated by the permanent magnet can pass through the magnetic circuits; it is opposed by the electromagnet. In components where the direction of the MMF of the permanent a id electromagnets align, the flux from the permanent magnet may pass without opposition, and the net flux may even be increased. ;Once the DC current through conductor 104 reaches a predetermined value indicative of an overcurrent condition, the magnitude of the generated second magnetic flux is sufficient to oppose the first magnetic flux enough to reduce the magnitude of the net magnetic flux such that the magnetic attraction between components in the first magnetic circuit is affected. In particular, once the (net) magnetic flux through the moveable plate (the portion of first magnetic flux generated by the permanent magnet to8, decreased by any variable contribution from the second magnetic flux generated by the electromagnet) is less than the predetermined threshold, the force from any biasing member 114 can cause the moveable plate to move or fall away from the fixed portion noa to which it was previously magnetically coupled (held in contact with due to the magnetic attraction between the components). Thus, during an overeat-rent condition, the device 100 can independently sense the o\Tercurrent and disconnect the r() circuit to which the device is connected without waiting for a command from a central control unit. This can help to reduce the response time of the device. ;The proportions of each of the first and second magnetic fluxes in each path (nob, 122a, 122h, 12(i) and (no, 112) is inversely' proportional to the reluctance of the paths, and these relative proportions can be altered or adjusted by changing the size of air gap 126, or by changing the size, shape, or material of the relevant components within each path. In some examples, reluctance of 1101) maybe higher than either of the other paths, and only a small proportion of the first and second magnetic fluxes lob, 124 may flow through component nob. However, the directions of the different fluxes is otherwise the same as illustrated, so the magnetic switch 102 will operate as described, but with the opening of the switch occurring at a different predetermined threshold than the example of Figure 4. ;Figure 5A illustrates a further example of the principle paths of the first and second magnetic fluxes through the first and second magnetic circuits in normal operation of the device (the secondary parallel paths are not illustrated here) when the conductor 104 is used as an electromagnet to vary the first magnetic flux ro6. In another example> which can be used in addition to or instead of the above arrangement, the means to vary the first magnetic flux lob further comprises an electromagnet in the form of a coil 128 disposed around part of the first magnetic circuit (here around component uoc, see Figure 5B), The coil is configured to generate a third magnetic flux 130 confined within the first magnetic circuit and overlapping with the first magnetic flux, wherein a direction of the first magnetic flux is opposite a direction of the third magnetic flux in the moveable plate. It will be understood that, when the second magnetic circuit is coupled to the first magnetic circuit (as in Figure -the third magnetic flux will also follow secondary parallel paths in proportion to the relative reluctance, as described above with reference to Figure 4, but only the principle paths are considered here. ;The overlapping, opposing, third magnetic flux i30 can reduce the first magnetic jinx, ig the net flux density through the moveable plate 102 and causing magnetic switch 102 to open. The coil 130 is configured to generate the third magnetic flux in response to an applied current, and in this way, can be used as an external trigger to open the switch 102 and activate the actuator 116. In particular, signals from a central control unit can supply or apply a DC voltage or current to the coil 128, or can xv otherwise cause a current to be applied to the coil to generate the third magnetic flux 130. The magnetic switch can therefore be opened in response to a fault condition other than an overcurrent or collision, through receipt of external signals from a central control unit. With such additional external control, a more robust device may be provided. ;With reference to Figure 5C, the position of the moveable plate 112 after opening of the switch 102 can be seen (i.e. the switch 102 is shown in an open position). This opening of the switch can be achieved by any suitable means of varying the first magnetic flux. The first portion 112a of the moveable plate has here contacted the piezoelectric component 120 with a force to generate an electrical signal and activate the actuator 1.16 (though the actuator n6 may otherwise be mechanically activated or operated). The arrangement of Figure 5C, with the hinged moveable plate, can allow a high force, high velocity movement of the first portion 112a of the moveable plate; this can facilitate rapid activation of the actuator, and thus can provide a device with a quicker response time. The exact force which is applied by the movable plate 112 (and the speed at which it moves) can be calculated by considering the moment generated by the biasing force from the biasing membertm; said force can be adjusted as appropriate by altering the biasing force and/or the position of the hinge/joint of the moveable member relative to the biasing member and the first portion 112a. In this way, the magnetic switch 102 described herein can be implemented in any suitable device, for use in a range of applications and different current ratings, as is required. ;With reference to Figure 6, example uses of electrical interrupter 100 (the example device described above, or any other device wo configured to use a magnetic switch as described herein) are described. In the example of Figure 6A, device 100 is incorporated within a powertrain 620. In particular, power-train 620 can 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, via the connection contacts 104c of the conductor 104, 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 Iv an electrical vehicle. ;During charging of such an electric vehicle incorporating device 100, the direction of current flow through conductor 104 is reversed; this acts to increase the net flux through the components of the first magnetic circuit, increasing the magnetic attraction between the moveable plate 112 and the fixed portion no; this can help to prevent release or activation of the device during a charging activity. ;In both Figure 6A and 613, a signal may be provided to coil 128 from a remote controller, or a remote power distribution unit, 610 within the vehicle 600. Such a signal may be issued in response to an external event. For example, when the device is connected to a battery 630 installed in the vehicle 600, an ignition signal may be sent to the coil 128 in response to a collision of the vehicle; the third magnetic flux generated by the coil electromagnet can cause opening of the switch 102 and thus activation of the actuator i16, which can in turn break the breakable region of the conductor in order to open the electrical circuit 650 and prevent the flow of current through the battery 630. Such an arrangement can improve safety in the event of a collision. Alternatively, device 100 and remote controller 610 can form a system which can be deployed in any other application where breaking of a circuit is required, such as in response to an overcurrent condition (in which scenario device um.) can operate independently of a signal from control 610, due to the optional second magnetic flux generated by the electromagnet formed from current through the switching region 104b of the conductor). ;With reference to Figure 7, a method 700 for opening a current conduction Kith along a conductor having a breakable region, using an electrical interrupter100 having a magnetic switch (for example, the device 100 of the first aspect) is described. ;At step 710, the method comprises generating a first magnetic flux 106; optionally, generating the first magnetic flux comprises generating the first magnetic flux with a permanent magnetic. In some examples, the permanent magnet is a fixed magnet contributing a fixed amount to the generated first magnetic flux. ;At step 720, the first magnetic flux is confined within a first magnetic circuit comprising a moveable plate and a fixed portion. The first magnetic flux through the moveable plate is at this stage at or above a predetermined threshold such that, at step f0 730, the moveable plate is magnetically coupled to the fixed portion (or held in place by magnetic attraction between the components). ;At step 740, the first magnetic flux is reduced (or weakened) by means configured to vary the first magnetic flux. Optionally, the mea ns may be one or more Is dectromagnetics, or a moveable permanent magnet. In the event of an overcurrent or fault condition, or a crash, the first magnetic flux through the moveable plate is varied such that it is reduced to below the predetermined threshold. ;Optionally, reducing the first magnetic flux comprises reducing the first magnetic flux using an electromagnet. Optionally, this comprises arranging a second magnetic circuit around a switching region of the conductor; and confining a second magnetic flux within the second magnetic circuit, the second magnetic flux generated in response to current flow through the current conduction path, wherein part of the fixed portion of the first magnetic circuit forms part of the second magnetic circuit such that the first and second magnetic fluxes at least partially overlap to reduce the net magnetic flux through the moveable plate. Additional or alternatively, reducing the first magnetic flux using an electromagnet comprises: arranging a coil around part of the first magnetic circuit; applying a current to the coil; and confining a third magnetic flux within the first magnetic circuit, the third magnetic flux generated in response to the applied current, wherein a direction of the first magnetic flux is opposite a direction of the third magnetic flux in the moveable plate. ;After the first magnetic flux is reduced to below the threshold, by whatever means is appropriate, a biasing force arranged to oppose a magnetic force between the fixed portion and moveable plate of the first magnetic circuit is greater than the magnetic force. At step 750, this greater biasing force causes the moveable plate to move away -20 -from the fixed portion; in other words, at step 750 the method comprises moving, in response to reducing the first magnetic flux through the moveable plate (to below the predetermined threshold), the moveable plate away from the fixed portion. ;At step 760, the method comprises applying, with the moveable plate, a force to activate an actuator. At step 770, the method comprises activating the actuator with the applied force and breaking the conductor (with the actuator) in the breakable region to open the current conduction path. Optionally, activating the actuator comprises releasing a high-pressure gas upon actuation of a pyrotechnic actuator. This released gas exerts a iv -pressure (either directly or indirectly) on the conductor 104 in the breakable region 104a. ;It is noted herein that while the above describes various exam*.s 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 (23)

1. Claims An electrical interrupter device (i00), comprising: a conductor (104) defining a current conduction path, the conductor comprising a breakable region (iO4a); an actuator (116) configured to, upon activation, break the conductor in the breakable region to open the current conduction path; and a magnetic switch (102) arranged to apply a force to activate the actuator, the magnetic switch comprising: Iv a first magnetic circuit arranged to confine a first magnet' (i06), the first magnetic circuit comprising a fixed portion (110) and a moveable plate (.112), and means for varying the first magnetic flux, wherein, when the first magnetic flux through the moveable plate is at or above a predetermined threshold, the moveable plate is magnetically coupled to the fixed portion, and when the first magnetic flux through the moveable plate is below the predetermined threshold, the moveable plate moves away from the fixed portion to apply the force.
2. 2. The device of claim 1, wherein the magnetic switch comprises a permanent magnet (108), wherein at least a portion of the first magnetic flux is generated by the permanent magnet,
3. 3. The device of claim 1 or claim 2, wherein the means for varying the first magnetic flux comprises an electromagnet, the electromagnet configured to contribute a variable portion of the first magnetic flux.
4. 4. The device of claim 3, wherein the conductor further comprises a switching region (1.04a), and the electromagnet comprises a second magnetic circuit arranged around the switching region of the conductor, the second magnetic circuit arranged to confine a second magnetic flux (124) generated in response to the current conduction path, wherein part (nob) of the fixed portion of the first magnetic circuit forms part of the second magnetic circuit such that the first and second magnetic fluxes at least partially overlap to reduce the first magnetic flux through the moveable plate.
5. 5. The device of claim, wherein the second magnetic flux is configured to increase in dependence on an increase in current along the current conduction path.
6. 6. The device of claim 4 or claim 5, wherein the moveable plate is arranged to apply the force in a first direction (152), wherein the breakable region is offset from the switching region in the first direction.
7. 7. The device of any of claims 4 to 6, further comprising an air Tap (126) in the Iv second magnetic circuit.
8. 8. The device of any preceding claim, wherein the electromagnet comprises a coil (128) arranged around a portion (floc) of the first magnetic circuit, the coil configured to generate a third magnetic flUX 03W within the first magnetic circuit and overlapping the first magnetic flux, wherein a direction of the first magnetic flux is opposite a direction of the third magnetic flux in the moveable plate.
9. 9, The device of claim 8, wherei oil is configured to generate the third magnetic flux in response to an applied current.to.
10. The device of any preceding claim, wherein a first portion (112a) of the moveable plate is magnetically coupled to the fixed portion when the first magnetic flux is at or above the predetermined threshold, and wherein a second portion (n±) of the moveable plate is rotatably coupled to the fixed portion,
11. 11. The device of claim to, further comprising a biasing member (n4) coupled to a third portion (412c) of the moveable plate, the second portion arranged between the first portion and -the third portion, wherein, when the first magnetic flux through the moveable plate is below the 30 predetermined threshold, the biasing member is configured to urge the moveable plate to rotate around the second portion to move the first portion of the moveable plate away from the fixed portion to apply the force,
12. 12. The device of claim ii, wherein the biasing member is configured to apply a ing force to the moveable plate which is less than a magnetic force magnetically -23 -coupling the moveable plate to the fixed portion when the first magnetic flux through the moveable plate is at or above a predetermined threshold.
13. 13. The device of any preceding claim, wherein the actuator is configure to be directly activated with the force applied by the moveable plate.
14. 14. The device of any of claims ito 12, wherein the actuator comprises a piezoelectric component (120), and wherein the moveable plate is configured to apply the force to the piezoelectric component in order to generate, by the piezoelectric lv component, an electrical signal to activate the actuator.
15. 15, The device of any preceding claim, wherein the actuator is a pyrotechnic actuator.
16. 16. A system comprising: the device (too) of any preceding claim; and a controller (610) configured to apply the current to the coil of claim 9.
17. 17. A vehicle (600) comprising the device (too) of any one of claims 1 to 15 or the system of claim 16, optionally, wherein the vehicle is art electric vehicle.
18. 18. A method of opening a current conduction path along a conductor 4) having a breakable region (iO4.a), the method comprising: generating a first magnetic flux (i06); confining a first magnetic flux within a first magnetic circuit comprising a moveable plate (112) and a fixed portion (no); magnetically coupling the moveable plate to the fixed portion when the first magnetic flux is at or above a predetermined threshold; reducing the first magnetic flux through the moveable plate to below the predetermined threshold; moving, in response to reducing the first magnetic flux through the moveable pLate, the moveable plate away from the fixed portion; applying, with the moveable plate, a force to activate an actuator (n6); activating the actuator with the applied force; and breaking the conductor in the breakable region to open the current conduction path.
19. 19. The method of claim 18, wherein generating the first magnetic flux comprises generating the first magnetic flux with a permanent magnetic (108).
20. 20, The method of claim 18 or claim 19, therein reducing the first etic flux comprises reducing the first magnetic flux using an electromagnet.
21. 21. The method of claim 20, wherein reducing the first magnetic flux using an electromagnet comprises: It) arranging a second magnetic circuit around a switching region (l04b) of the conductor; and confining a second magnetic flux (24) within the second magnetic circuit, the second magnetic flux generated in response to current flow through the current conduction path, wherein part (nob) of the fixed portion of the first magnetic circuit forms part of the second magnetic circuit such that the first and second magnetic fluxes at least partially overlap to reduce the net magnetic flux through the moveable plate.
22. The method of any of claim 20 or claim 21, wherein reducing the first magnetic flux using an electromagnet comprises: arranging a coil (128) around part of the first magnetic circuit; applying a current to the coil; and confining a third magnetic flux (130) within the first magnetic circuit, the third magnetic flux generated in response to the applied current, wherein a direction of the first magnetic flux is opposite a direction of the third magnetic flux in the moveable plate.
23. 23. The method of any of claims 17 to 21, wherein the moveable plate moves away from the fixed portion in response to a biasing force, wherein the biasing force is less 30 than a magnetic force magnetically coupling the moveable plate to the fixed portion when the first magnetic flux is at or above a predetermined threshold.