Auxiliary unit for switch or circuit breaker

Abstract

An auxiliary unit 400 for use with a switching device or circuit breaker comprises a mechanism 402 configured to rotate between first and second positions, a permanent magnet 404 coupled to and rotatable with the mechanism, a ferromagnet 406 arranged adjacent to the permanent magnet, and a conductor 408 wound at least partly around the ferromagnet. In the first and second positions, a respective first and second pole of the permanent magnet is proximal to the ferromagnet. When rotated, the permanent magnet reverses a magnetic field of the ferromagnet and thereby generates a coil in the conductor. A control unit 410 produces an output signal in response to the generated current. The ferromagnet may be a Wiegand wire. The current generated in the conductor may be produced by the Wiegand effect. The control unit may comprise a communication module 412 for communicating the output signal to a receiving device, a power storage 414 for storing energy from the generated current, and a converter 416. The auxiliary unit may comprise a means for fixing to a side of a circuit breaker such that the mechanism and an indicator switch 440 rotates with an operating handle of the circuit breaker.

Description

Field This relates to an auxiliary unit, for use with a switching device (switch) or circuit breaker, to indicate and communicate the status of the switching device or circuit breaker. Optionally the circuit breaker is a miniature circuit breaker, or MCB. Background A circuit breaker is used to break an electrical circuit, and so prevent circuits from drawing too much current. This can may prevent damage to equipment and mitigate the risk of fire. Electrically isolating circuits is also advantageous for ensuring safety during maintenance. Therefore, it is important to know the status of a circuit breaker. In particular, it would be advantageous to be able to monitor the behaviour and status of a circuit breaker over its life-cycle. An auxiliary unit fixed to a circuit breaker can allow a user to remotely access and monitor the status of a circuit breaker. However, since part of the operation of a circuit breaker is to break an electrical circuit, the auxiliary unit itself requires a power source external to the circuit breaker in order to function. Including an external power source may pose an additional extra safety risk and also may require a more involved and complicated installation. Therefore, it would be desirable to provide an auxiliary unit which does not require an external power source, and instead is self-powered. Summary Described herein is an auxiliary unit for use with a switching device or circuit breaker, and a system comprising one or more auxiliary units, each of which is coupled to a respective one of one or more circuit breakers. A method for operating the auxiliary unit is also disclosed. An auxiliary unit for use with a switching device or circuit breaker is disclosed. The auxiliary unit comprises a mechanism, which is configured to rotate between a first position and a second position. The auxiliary unit further comprises a permanent magnet, which is coupled to the mechanism and configured to rotate with the mechanism. The auxiliary unit also comprises a ferromagnet, which is arranged adjacent (or proximal) to the permanent magnet. A first pole of the permanent magnet is proximal to the ferromagnet when the mechanism is in the first position, and a second pole of the permanent magnet is proximal to the ferromagnet when the mechanism is in the second position. The auxiliary unit further comprises a conductor, which is wound around at least part of the ferromagnet. The rotation of the permanent magnet is configured to reverse a magnetic field of the ferromagnet and thereby generate a current in the conductor. The auxiliary unit also comprises a means for producing an output signal in response to the generated current. The permanent magnet, ferromagnet and conductor of the auxiliary unit form an energy harvesting mechanism which acts to harvest energy using a magnetisation reversal effect, such that no external power is necessary. Due to space requirements, including an external power source in an auxiliary unit may be difficult, since it may require including an alternating current (AC) to direct current (DC) converter along with contacts with an AC line. Self-powering an auxiliary unit may allow for a reduction in the size of the auxiliary unit. Additionally, an auxiliary unit without an external power source may be easier to install, since there may be less internal and external wiring required, and can be easily retrofit. The auxiliary unit described herein may therefore be cheaper to manufacture and install. In some implementations, the means for producing an output signal comprises a communication module, which is configured to communicate the output signal to a receiving device. The communication module can be powered by the generated current. Optionally, the communication module comprises a wireless communication module, which is configured to communicate the output signal to receiving device which is remote from the auxiliary unit. Optionally, the auxiliary unit may comprise a receiving device and the communication module may be configured to communicate the output signal to the receiving device. Optionally, the receiving device comprised by the auxiliary unit may include a counter and / or internal memory. Optionally, the output signal is an indicator of the change in status of a circuit breaker. The auxiliary unit may allow the status of a circuit breaker to be available remotely, which remote availability can be facilitated by way of the energy harvesting mechanism described herein. Additionally or alternatively, the status information may be stored within the auxiliary unit for later retrieval and / or use (i.e. in memory). This may allow for better prognostic maintenance and also allow a user to more easily and rapidly be informed of a change in the status of a circuit breaker. In some implementations, the means for producing an output signal comprises a converter, which is configured to convert the current from alternating current to direct current. The converter can be any AC to DC converter. Optionally, the converter may comprise a rectifier. In some implementations, the means for producing an output comprises an energy storage means or means of power storage, which is configured to capture energy from the generated current (i.e. store energy from the generated current). In other words, the energy / power storage means is configured to store energy harvested by the energy harvesting mechanism of the auxiliary unit. Optionally, the means of power storage comprises a capacitor, and / or a super-capacitor, and / or a battery. In some implementations, the means for power storage may be configured to provide power to the communication module. By providing energy storage means, the harvested energy can be stored within the auxiliary unit, further improving the capacity of the auxiliary unit to provide status information of the circuit breaker over an extended period of time. In some implementations, the width of the auxiliary unit may be at most 9mm. The auxiliary unit can thus be configured to fit within standard circuit breaker racks or arrays, and so may be more easily retrofit. In some implementations, the conductor which is wound around at least part of the ferromagnet is a copper coil. In some implementations, the ferromagnet may be a Wiegand wire. A Wiegand wire is a low-carbon ferromagnetic alloy of cobalt, iron, and vanadium. This low-carbon ferromagnetic alloy is known as a Vicalloy. Optionally, the current generated in the conductor may be produced by the Wiegand effect. By way of this specific arrangement of the energy harvesting mechanism, a more efficient energy harvesting mechanism may be provided, which also operates to produce a discernible current pulse, thereby facilitating easier generation of an output signal indicative of a movement or change in position of the mechanism. In some specific implementations, the circuit breaker is a low voltage circuit breaker. Optionally, the circuit breaker is a miniature circuit breaker, MCB. In other examples, the circuit breaker is an ROD, RCCB, RCBO or any other type of circuit breaker or current breaker. Also disclosed herein is a method of operating an auxiliary unit for use with a circuit breaker. The method comprises rotating the mechanism of the auxiliary unit between the first and second position. The method further comprises causing the permanent magnet to rotate with the mechanism, such that the second pole of the permanent magnet is proximal to the ferromagnet. The method further comprises causing the magnetic field of the ferromagnet to reverse, in response to the rotation of the permanent magnet. The method further comprises generating a current in the conductor, in response to reversing the magnetic field of the ferromagnet. The method further comprises producing an output signal in response to the generated current. Described herein is a system comprising a circuit breaker and an auxiliary unit, wherein the auxiliary unit is coupled to the circuit breaker. Optionally the auxiliary unit is coupled to the circuit breaker such that the first position of the mechanism of the auxiliary unit is configured to correspond to the circuit breaker being in one of an open or closed position, and wherein the second position of the mechanism of the auxiliary unit is configured to correspond to the circuit breaker being in the other of the open or closed position. Optionally, the auxiliary unit is coupled to an actuator or actuation switch of the circuit breaker. In some implementations, the auxiliary unit comprises an indicator switch configured to indicate the position of the mechanism. The indicator switch can be part of, or coupled to, the mechanism. The indicator switch can be coupled to the actuator / actuation switch of the circuit breaker. Actuation of the indicator switch is configured to rotate the mechanism between the first position and the second position. Optionally, the auxiliary unit comprises a means for fixing to the circuit breaker (in some examples, fixing to a housing of the circuit breaker). In this way, the auxiliary unit can be fixed to a side of circuit breaker, for example. Also described herein is a system comprising one or more circuit breakers and one or more auxiliary units. Each of the one or more auxiliary units is coupled to a respective one of the one or more circuit breakers. In some implementations, each of the one or more auxiliary comprises a means for fixing to the respective one of the one or more circuits breakers. In some implementations, the coupling of each of the one or more auxiliary units to the respective one of the one or more circuit breakers is configured such that the first position of the mechanism of the auxiliary unit is configured to correspond to the respective circuit breaker being in one of an open or closed position, and wherein the second position of the mechanism of the auxiliary unit is configured to correspond to the respective circuit breaker being in the other of the open or closed position. In some implementations, the system is configured such that each of the one or more auxiliary units comprises an indicator switch configured to indicate the position of the mechanism and wherein actuation of the indicator switch is configured to rotate the mechanism between the first position and the second position. Optionally, the indicator switch may be coupled to an actuation switch of the circuit breaker and configured to move in tandem with the actuation switch. Also described herein is an auxiliary unit for use with a switching device or circuit breaker is disclosed. The auxiliary unit comprises an actuating mechanism to make or break a contact within the auxiliary unit, which actuating mechanism is configured to rotate between a first position and a second position. The auxiliary unit further comprises a permanent magnet, which is coupled to the actuating mechanism and configured to rotate with the actuating mechanism. The auxiliary unit also comprises a ferromagnet, which is arranged adjacent (or proximal) to the permanent magnet. A first pole of the permanent magnet is proximal to the ferromagnet when the mechanism is in the first position, and a second pole of the permanent magnet is proximal to the ferromagnet when the mechanism is in the second position. The auxiliary unit further comprises a conductor, which is wound around at least part of the ferromagnet. The rotation of the permanent magnet is configured to reverse a magnetic field of the ferromagnet and thereby generate a current in the conductor. The auxiliary unit also comprises a control unit configured to produce an output signal in response to the generated current. The magnetisation reversal effect described herein may generate a stronger and more consistent energy pulse than other forms of energy harvesting using electromagnetic induction. The voltage induced by a changing magnetic field is proportional to the rate of change of the magnetic field. Therefore, in energy harvesting mechanisms which rely on rotating and / or translating a permanent magnet within or with respect to a conductor coil wound around the permanent magnet, the induced voltage will depend strongly on the available rate of rotation or translation of the permanent magnet. The energy available for harvest will therefore vary accordingly. Moreover, the available energy is limited by the available speed / rate of rotation of the permanent magnet; in cases where the permanent magnet is rotated manually, the energy available for harvest may therefore be fairly small. In contrast, the Wiegand effect provides a rapid reversal in magnetization and the use of a Wiegand wire can increase the output voltage of by several orders of magnitude as compared to a similar coil with a non-Wiegand wire. List of Figures The detailed description is with reference to the following Figures. Figure 1A, and IB: Schematic of an example auxiliary unit showing a mechanism and permanent magnet arranged in a first position (Figure 1A) and arranged in a second position (Figure IB). Figure IC, and ID: A perspective view of an example auxiliary unit (Figure IC), and a front-on, schematic, view of a system comprising an example auxiliary unit and a circuit breaker. Figure 2A, 2B, and 2C: Schematic of another example auxiliary unit, with optional additional components. Figure 3A, 3B, 3C, 3D, 3E, and 3F: Schematic illustration of the Wiegand effect. Figure 4: A side-on, cross section, view of an example implementation of an auxiliary unit. Figure 5: Illustration of an example method of operating an auxiliary unit. Detailed Description With reference to Figures 1A and IB, an auxiliary unit 100 for use with a switching device or circuit breaker is described. The circuit breaker is optionally a low voltage circuit breaker, for example for residential or domestic applications, such as a miniature circuit breaker, MCB. However, the principles described herein are applicable to any type of circuit breaker, including but not limited to an RCD, RCCB, RCBO, or any suitable switching device or switch. Figure 1A shows a schematic example of an example auxiliary unit, in which a mechanism 102 is in a first position, and is configured to rotate between the first position and a second position. Figure IB depicts the schematic example of the example auxiliary unit, in which the mechanism 102 is in the second position. Any suitable mechanism can be used. In some examples, the mechanism can be simple switch, such as a toggle switch. The mechanism can also be called herein an "actuating mechanism", and in some examples the mechanism can be configured to make or break a contact within the auxiliary unit, with the permanent magnet being disposed around or coupled to the actuating mechanism. A permanent magnet 104 is coupled to the mechanism 102. The coupling is such that the permanent magnet 104 is configured to rotate with the mechanism 102. A ferromagnet 106 is arranged adjacent to the permanent magnet 104. In some examples, the ferromagnet may be a Wiegand wire. This will be discussed below in more detail with reference to Figure 3. In this example, the permanent magnet is configured such that when the mechanism 102 is in the first position, as shown in Figure 1A, the south pole (S) of the permanent magnet is proximal to the ferromagnet 106. Due to the rotation of the mechanism 102 between the first position, as shown in Figure 1A, and the second position, as shown in Figure IB, the permanent magnet 104 rotates. Figure IB illustrates that when the mechanism is in the second position, the north pole (N) of the permanent magnet is proximal to the ferromagnet. In other words, the polarity of the permanent magnet has changed due to rotation of the magnet 104. In the examples depicted in Figures 1A and IB, the proximity of one pole (N or S) of the permanent magnet 104 to the ferromagnet 106 in the first and second positions is an example for demonstration purposes only. For instance, in some other examples, when the mechanism is in the first position the north pole (N) of the permanent magnet is proximal to the ferromagnet, and when the mechanism is in the second position the south pole (S) of the permanent magnet is proximal to the ferromagnet. The auxiliary unit further comprises a conductor 108, which is wound around at least part of the ferromagnet 106. In some examples, the conductor 106 may be a copper coil. The rotation of the permanent magnet 104, in response to the mechanism 102 rotating between the first position (Figure 1A) and the second position (Figure IB), is configured to reverse the direction of the magnetic field of the ferromagnet 106. Reversing the direction of the magnetic field of the ferromagnet 106 thereby induces / generates a current (I) in the conductor 108. The magnetisation reversal effect which is used to generate the current (I) in the conductor 108 is discussed in more detail below with reference to Figure 3. This magnetisation reversal effect allows the auxiliary unit to be self-powered. Without the requirement of an external power source, there may be less internal and external wiring required. The auxiliary unit may therefore be cheaper to manufacture and install, and can be more easily retrofit to existing circuit breakers. Moreover, the arrangement of Figure 1 provides efficient energy harvesting in a compact footprint. The auxiliary unit further comprises a means for producing 110 an output signal 120a and / or 120b, where the output signal is generated in response to the generated current (I). For example, the current pulse generated by reversal of the magnetic field can trigger one or more signals to be output. The output signal(s) 120a, 120b indicate that the mechanism 102 has moved or changed state, or that the permanent magnet 104 has otherwise rotated. The means 110 for producing the output signal can be implemented as any suitable controller or control unit 110. In some examples, the means 110 comprise logic gates or a logic gate circuit configured to produce the signal in response to the generated current. A housing 148 is arranged around the components of the auxiliary unit. In other words, the components of the auxiliary unit are at least partially disposed within the housing 148. With further reference to Figure IC and ID, the auxiliary unit is configured to be, in use, coupled to a circuit breaker 150. In particular, the auxiliary unit is configured to be coupled to an actuator or actuation switch of the circuit breaker (not shown). In some implementations, the auxiliary unit comprises an indicator switch 140 configured to indicate the position of the mechanism 102. The indicator switch 140 can be coupled to or otherwise part of the mechanism 102. Actuation of the indicator switch is configured to rotate the mechanism between the first position and the second position. The indicator switch 140 can be coupled to the actuator or actuation switch of the circuit breaker 160 via coupling 132 (i.e. the circuit breaker can be positioned to the right of Figure IC, on the same side as coupling 132). The coupling 132 is configured such that the first position of the mechanism of the auxiliary unit is configured to correspond to the circuit breaker being in one of an open or closed position, and the second position of the mechanism of the auxiliary unit is configured to correspond to the circuit breaker being in the other of the open or closed position. In this way, the auxiliary unit mirrors the state or condition of the circuit breaker, and rotation of the mechanism 102 is indicative of actuation of the circuit breaker 160. The generated output signal can thus indicate a change in state of the circuit breaker. A width (w) of the housing 148 of the example auxiliary unit 100, as illustrated in Figure IC, is at most 9mm. This arrangement can allow the auxiliary unit to be retrofit to existing circuit breaker racks or arrangements, since it is within the standard footprint for auxiliary devices. In some examples the output signal 120a and 120b may be configured to indicate a change in a status of a circuit breaker (such as circuit breaker 160) with which the auxiliary unit 100 is configured to be used (and to which the auxiliary unit may be coupled). For example, each current pulse can indicate rotation of the permanent magnet (and thus rotation of an actuation switch of the associated circuit breaker to which the mechanism of the auxiliary unit is coupled). This allows a user to be informed of a change in the status of a circuit breaker more easily and rapidly, and therefore facilitates better prognostic maintenance. In some examples, the output signal 120a is configured to be communicated to a receiving device 124, which is remote to the auxiliary unit. The output signal 120a can be communicated by a communication module (optionally a wireless communication module), which can be powered by the generated current. The receiving device 124 may be any suitable computing device configured to receive output signal 120a. This can allow a user to determine information about the circuit breaker when remote from the auxiliary unit. In some examples, the auxiliary unit may comprise a receiving device 122 and the output signal 120b is configured to be communicated to the receiving device 122. In some examples, the receiving device 122 may include a counter and / or internal memory. This can allow a user to retrieve information about the circuit breaker from the auxiliary unit at a later point in time, for example in situations where there is no wireless connectivity. With reference to Figures 2A, 2B, and 2C, example auxiliary units 200 in which the means for producing 210 an output signal 220 comprises optional additional components are described. These auxiliary units are examples of auxiliary unit 100; like reference numerals refer to like features. In the example of Figure 2A, the means for producing 210 an output signal 220 comprises communication module 212. The communication module is powered by the generated / induced current (I). The communication module 212 is configured to provide the output signal 220a, 220b to one or more receiving devices 222, 224. In some implementations, the communication module may comprise a wireless communication module, in which the output signal 220a is communicated to a receiving device 224, which may be remote to the auxiliary unit 100. In other words, the communication module is configured for wireless communication with a remote device 224. Any suitable wireless communication protocol can be used to communicate between the remote device 224 and the communication module 212, including but not limited to, any cellular connection (e.g. 2G, 3G, 4G, 5G), a Wi-Fi connection, a Bluetooth connection, a Bluetooth Low Energy BLE connection, a Zigbee connection, or the like. The disclosure is not limited to these specific protocols, and it will be understood that communication using any future wireless communication protocols is also envisaged herein. By providing a wireless communication module 212 in this way, a user can remotely obtain information about a status change of a circuit breaker associated with the auxiliary unit. For example, the remote device may be provided with an application, web browser portal, or other suitable program for communicating with the communication module 110 of the auxiliary unit 100. Additionally or alternatively, the auxiliary unit 200 may comprise a receiving device 222, which may be implemented in the form of internal memory or storage and / or a counter mechanism. This can allow a user to retrieve information about the circuit breaker from the auxiliary unit at a later point in time, for example in situations where there is no wireless connectivity. In the example of Figure 2B, the means for producing 210 an output signal 220 may comprise energy storage means or a means for power storage 214. The means for energy / power storage 214 may be configured to store at least part of the generated / induced current and use that stored energy to power the communication module 212. Optionally, the power storage means 214 comprises a capacitor and / or a supercapacitor, which can provide short term energy storage. Optionally, the storage means comprises a battery, which can provide long term energy storage. In the example of Figure 2C, the means for producing 210 an output signal 220 may comprise a converter 216. The converter 216 is configured to convert the current from alternating current (AC) to direct current (DC). The converter can be any AC to DC converter. Optionally, the converter may be a rectifier. By providing an independent energy harvesting mechanism within the auxiliary unit, which is not directly connected to an external power supply, sufficient power can be provided to the communication module 212 to facilitate monitoring of a status of an associated circuit breaker 160. This can facilitate remotely monitoring the status of the circuit breaker, and so may result in better prognostic maintenance of the breaker. Additionally, a user may more easily and rapidly be informed of a change in the status of a circuit breaker. With reference to Figure 3 the magnetisation reversal effect which generates the current, and example implementations of the ferromagnet 302, are described. Ferromagnet 302 is a specific example of ferromagnet 106 described above. A conductor 304 is would around the ferromagnet. Conductor 304 is an example of conductor 108 described above. In Figure 3A, the ferromagnet 302 comprises a Wiegand wire. A Wiegand wire is a low-carbon ferromagnetic alloy of cobalt, iron, and vanadium. This low-carbon ferromagnetic alloy is known as a Vicalloy. The wire is fully annealed, such that it is magnetic but retains only a very small residual field in the absence of an external magnetic field. The wire is further subject to a series of twisting and untwisting operations. This process cold-works the outside shell 302a of the wire while retaining a soft core 302b within the wire. The wire is then aged. The outside shell 302a has a much larger magnetic coercivity than the inner core 302b, and so the outer shell 302a will retain an external magnetic field even in the absence of the external magnetic field. The magnetisation reversal effect which can generate the current (I) in the conductor 304, which is wound around at least part of the ferromagnet 302, works in the following way. This magnetisation reversal effect may be known as the Wiegand effect. In Figure 3A, the Wiegand wire 302 is shown as retaining a magnetic field 306. In Figure 3B, an external magnetic field 308 is applied to the Wiegand wire 302, where the direction of the applied external magnetic field is in the opposite direction to the retained magnetic field of the Wiegand wire. The external magnetic field 308 is applied by permanent magnet 104. Initially, the magnetic field of the inner core 302b, which has a much weaker magnetic coercivity than the outer shell 302a, reverses in direction and so aligns with the direction of the applied external magnetic field 308 from magnet 104. In Figure 3C, the strength of the applied external magnetic field 308 has increased in the same direction (because the rotation of the permanent magnet 104 from the first position to the second position is complete). The direction of the magnetic field of the outer shell 302a, which has a much larger magnetic coercivity than inner core 302b, reverses. Therefore, in response to the applied magnetic field 308, the magnetic field direction of both the inner core 302b and the outer shell 302a reverses rapidly, and so the magnetic field direction of the Wiegand wire 302 reverses rapidly. This rapid reversal in magnetic field direction generates a current (I) in the conductor 304. One or both of the pulses shown in Figure 3 can be used to produce the output signal 120. Figure 3D illustrates the Wiegand wire 302 when the external magnetic field is no longer applied (not applicable in this auxiliary unit, since the permanent magnet is arranged adjacent or proximal to the ferromagnet). The Wiegand wire 302 retains the reversed magnetic field in the absence of an external magnetic field. Figures 3E and 3F demonstrate the same magnetisation reversal effect used to generate a current in the conductor 304, with the external magnetic field applied 308 instead in the opposite direction to Figures 3B and 3C, and so in the opposite direction to the retained magnetic field 306 of the Wiegand wire 302 (i.e. due to another rotation of the permanent magnet from the second position to the first position). Since the rate of change of a magnetic field is proportional to the induced voltage, the rapid reversal of the magnetic field direction of the Wiegand wire 302 generates a large current in the conductor 108, 304. Moreover, since the response of the Wiegand wire is regular and repeatable, the generated current may be highly consistent over the course of repeated operation. This magnetisation reversal effect may generate a stronger and more consistent current than other methods of electromagnetic induction. For example, when rotating and / or translating a permanent magnet with respect to a conductor coil which is wound around the permanent magnet, the induced voltage will depend strongly on the rate of rotation or translation of the permanent magnet; therefore, any energy available for harvest will vary strongly also and be very sensitive to variations in the movement of the permanent magnet. In contrast, the present approach is more robust and repeatable, as well as able to generate a larger current, allowing for more efficient energy harvesting. Figure 4 depicts an example implementation of the auxiliary unit 400, showing a side view cross section of the unit 400; an outline of housing 448 of the auxiliary unit is shown, with the components of the auxiliary unit overlaid on the housing for the purpose of illustration. The unit 400 is rotated 90 degrees in comparison to the view shown in Figure IC (i.e. is shown with the front of the unit facing the top of the page). The example auxiliary unit 400 is for use with a switching unit or circuit breaker 160, and is an example of auxiliary unit 100 (where like reference numerals refer to like features). The circuit breaker may optionally be: a low voltage circuit breaker, such as an MCB, or it may be any other type of circuit breaker, such as an RCD, RCCB, or RCBO, or other suitable device. The example auxiliary unit 400 comprises a mechanism 402. The mechanism 402 is configured to rotate between a first and second position. In the example shown in Figure 4, the mechanism 402 is in the first position. The auxiliary unit 400 further comprises an indicator switch 440. The indicator switch is configured to indicate the position of the mechanism 402. The indicator switch 440 is further coupled or functionally configured such that actuation of the indicator switch rotates the mechanism between the first and second position. Therefore, a user may manually operate the example auxiliary unit and rotate the mechanism 402 between the first and second position. The auxiliary unit 400 further comprises a permanent magnet 404 having two poles, N and S. The permanent magnet 404 is coupled to the mechanism 402, and so when the mechanism 402 is rotated between the first and second position, the permanent magnet rotates with the mechanism. Adjacent and proximal to the permanent magnet 404, the example auxiliary unit 400 further comprises a ferromagnet 406. The permanent magnet 404 is configured such that when the mechanism 402 is in first position the south pole (S) of the permanent magnet 404 is proximal to the ferromagnet 406, and when the mechanism 402 is in the second position, the north pole (N) of the permanent magnet 404 is proximal to the ferromagnet 406. This arrangement of the north and south pole of the permanent magnet 404 is an example implementation of the auxiliary unit 400, and therefore the relative arrangement of the poles may be modified in other examples of the auxiliary unit. Moreover, the specific shape of the permanent magnet 404 may vary. In the example auxiliary unit 400, a conductor 408 is wound around at least part of the ferromagnet 406. In this specific example auxiliary unit 400, the conductor 408 is a copper coil and the ferromagnet 406 is a Wiegand wire. Rotation of the permanent magnet 404 is configured to reverse a magnetic field of the ferromagnet 406 and thereby generate a current in the conductor 408. In other words, the magnetisation reversal effect generates a current in the conductor 408. More specifically, the rotation of the mechanism 402 between the first and second position causes the permanent magnet 404 to rotate in turn. The rotation of the permanent magnet 404 is configured to reverse the direction of the magnetic field of the ferromagnet 106, and thereby generate a current in the conductor 408. The example auxiliary unit 400 is configured to use a magnetisation reversal effect to harvest energy, such that the auxiliary unit 400 self-powered and no external power source is required. The example auxiliary unit 400 may therefore require less internal and external wiring, and so may be easier to install, more easily retrofit, and cheaper to manufacture. The example auxiliary unit 400 further comprises a means for producing 410 an output signal based on, or in response to, the current generated in the conductor 408. Since the current is generated in response to rotation of the permanent magnet, the auxiliary unit 400 can be configured such that the output signal indicates a change in the position of the mechanism 402 (and associated indicator switch 440). The means for producing an output signal 410 in this example comprises a wireless communication module 412 which is configured to generate an output signal based on a current generated in the conductor. The communication module 412 can also be configured to communicate the output signal to a receiving device which is remote from the example auxiliary unit 400. The means for producing an output signal 410 further comprises a means of power storage 414. The means of power storage 414 may comprise at least one of: a capacitor, a super-capacitor, and a battery. The means of power storage 414 is configured to provide power to the wireless communication module 412. The means for producing an output signal 410 further comprises a converter 416, which is configured to convert AC to DC (e.g. an AC to DC converter). The converter 416 may comprise a rectifier. The means 410 for producing an output signal can comprise a printed circuit board PCB comprising any one of the components 412, 414, 416. For example, the communication module 412, converter 416 and / or storage means 414 can all be assembled on a PCB as a printed circuit board assembly. In other examples, the means 410 for producing an output signal can comprise or be implemented within any suitable controller or control unit. The example auxiliary unit 400 is configured for use with a switch or circuit breaker, and can be coupled to the switch or circuit breaker (such as to circuit breaker 160 in Figure ID). In some examples, the example auxiliary unit 400 may further comprise a means for fixing to the circuit breaker, optionally to a housing of the circuit breaker. For example, housing 448 may be configured for fixing to the circuit breaker / switch with one or more fixing means. The indicator switch 440 of the example auxiliary unit 400 may be further coupled to an actuation switch of the circuit breaker and configured to move in tandem with the actuation switch. Therefore, the indicator switch 440 and mechanism 402 are configured such that the first position corresponds to the circuit breaker being in one of an open or closed position, and the second position is configured to correspond to the circuit breaker being in the other of the open or closed position. The actuation switch can part of a linear actuator or part of a rotational actuator, as required by the application. Any suitable type of actuator can be used (electric, hydraulic, pneumatic, magnetic, thermal, piezoelectric, etc.), as required by the application of the circuit breaker, the size or type of circuit breaker, etc. In other examples, the actuation switch of the circuit breaker may be a manual actuation switch. By providing an energy harvesting mechanism within the example auxiliary unit 400 as described above, which is not directly connected to the power supply to the circuit breaker, or to any other external power supply, sufficient power can be provided to the wireless communication module 412 to provide remote indication of the status of the circuit breaker. This information may update a user more efficiently of problems with a circuit breaker. The information may additionally or alternatively be stored for later use, and allow for better planned and prognostic maintenance. With reference to Figure 5, an example method 500 for using or operating the auxiliary unit 100 is described. At operation 502, the method comprises rotating the mechanism 102 of the auxiliary unit 100 between the first and second positions (for example from the first position to the second position). At operation 504, the method further comprises causing the permanent magnet 104 to rotate with the mechanism 102, such that the second pole of the permanent magnet is proximal to the ferromagnet 106. At operation 506, the method further comprises causing the magnetic field of the ferromagnet 106 to reverse, in response to the rotation of the permanent magnet 104. At operation 508, the method further comprises generating a current (I) in the conductor 108, in response to reversing the magnetic field of the ferromagnet 106. At operation 510, the method further comprises producing an output signal 120 in response to the generated current (I). It will be understood that method 500 may be repeated, after producing an output signal 120, returning to operation 502 and rotating the mechanism in the other direction (i.e. from the second position to the first position), as indicated by the dashed line in Figure 5.

Claims

1. An auxiliary unit (100, 200) for use with a switching device or circuit breaker, comprising:a mechanism (102, 202) configured to rotate between a first position and a second position;a permanent magnet (104, 204) coupled to the mechanism and configured to rotate with the mechanism;a ferromagnet (106, 206), wherein the ferromagnet is arranged adjacent to the permanent magnet, and wherein a first pole of the permanent magnet is proximal to the ferromagnet when the mechanism is in the first position, and wherein a second pole of the permanent magnet is proximal to the ferromagnet when the mechanism is in the second position; anda conductor (108, 208) wound around at least part of the ferromagnet, wherein the rotation of the permanent magnet is configured to reverse a magnetic field of the ferromagnet and thereby generate a current in the conductor;means (110, 210) for producing an output signal (120, 220) in response to the generated current.

2. The auxiliary unit (100, 200) of claim 1, wherein the means (110, 210) for producing an output signal (120, 220) comprises a communication module (212), wherein the communication module is configured to communicate the output signal to a receiving device (122, 124, 222, 224).

3. The auxiliary unit (100, 200) of claim 2, wherein the communication module (212) comprises a wireless communication module, and wherein the wireless communication module is configured to communicate the output signal (120a, 220a) to the receiving device (124, 224), where the receiving device is remote from the auxiliary unit.

4. The auxiliary unit (100, 200) of any preceding claim, where the means (110, 210) for producing an output comprises a means of power storage (214), wherein the means of power storage is configured to store energy from the generated current.

5. The auxiliary (100, 200) unit of claim 4, wherein the means of power storage (214) comprises one or more of: a capacitor, a super-capacitor and a battery.

6. The auxiliary unit (100, 200) of any preceding claim, wherein the means (110, 210) for producing an output signal comprises a converter (216), wherein the converter is configured to convert the current from alternating current to direct current.

7. The auxiliary unit (100, 200) of any preceding claim, wherein the ferromagnet (106, 206) is a Wiegand wire (302).

8. The auxiliary unit (100, 200) of claim 7, wherein the current generated in the conductor is produced by the Wiegand effect.

9. The auxiliary unit (100, 200) of any preceding claim, wherein the conductor (108, 208) is a copper coil.

10. The auxiliary unit (100, 200) of any preceding claim, wherein the width of the auxiliary unit is at most 9mm.

11. A system comprising: a circuit breaker; and the auxiliary unit (100, 200) of any one of the preceding claims, wherein the auxiliary unit is coupled to the circuit breaker.

12. The system of claim 11, wherein the auxiliary unit (100, 200) comprises a means for fixing to a side of the circuit breaker.

13. The system of any one of claims 11 or 12, wherein the auxiliary unit is coupled to the circuit breaker such that the first position of the mechanism (102, 202) of the auxiliary unit is configured to correspond to the circuit breaker being in one of an open or closed position, and wherein the second position of the mechanism of the auxiliary unit is configured to correspond to the circuit breaker being in the other of the open or closed position.

14. The system of any one of claims 11 to 13, wherein the auxiliary unit (100, 200) comprises an indicator switch (440) configured to indicate the position of the mechanism (102, 202) and wherein actuation of the indicator switch is configured to rotate the mechanism between the first position and the second position.

15. A method of operating the auxiliary unit (100, 200) of any of claims 1 to 10, comprising:rotating the mechanism (102, 202) from the first position to the second position;5 causing the permanent magnet (104, 204) to rotate with the mechanism, suchthat the second pole of the permanent magnet is proximal to the ferromagnet (106, 206);causing, in response to the rotation of the permanent magnet, the magnetic field of the ferromagnet to reverse;io generating, in response to reversing the magnetic field of the ferromagnet, thecurrent in the conductor (108, 208); andproducing an output signal (120, 220) in response to the generated current.19

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