WO2024223084A1

WO2024223084A1 - Automatic recloser device

Info

Publication number: WO2024223084A1
Application number: PCT/EP2024/025153
Authority: WO
Inventors: Amara SAIKUMAR; Vishakha Vilas HARLAPUR
Original assignee: Eaton Intelligent Power Limited
Priority date: 2023-04-26
Filing date: 2024-04-19
Publication date: 2024-10-31

Abstract

An automatic recloser device, and a method for operating the device, is provided for use with a residual current device, wherein the residual current device comprises a switch which can be opened or closed by rotation of a first knob of the residual current device. The automatic recloser device comprises a housing at least partially enclosing a piezoelectric motor and a mechanical linkage arranged between the piezoelectric motor and the first knob. The mechanical linkage is coupled to the piezoelectric motor and comprises a first rigid member configured to engage with the first knob. The piezoelectric motor is configured to apply a force in a first linear direction to move the mechanical linkage and the movement of the mechanical linkage causes a rotation of the first knob in a first rotational direction, thereby closing the switch.

Description

Automatic Recloser Device

Field

[0001] The present invention relates to a device having an auto-close or automatic recloser function (automatic recloser device) suitable for use with a residual current device.

Background

[0002] A residual current device (RCD) is a protection device which continuously monitors current through a circuit it protects to detect any leaking current (e.g., a current leak to the earth wire). It also protects against current shorts, as well as electric electrocution or shock caused by direct contact. Residual current devices include residual current circuit breakers (RCCBs, which provide leakage current protection) and residual current circuit breakers with overload protection (RCBOs, which also provides overload protection).

[0003] Current leakage protection is achieved by monitoring the current flow in the line and neutral. RCCBs operate by measuring the difference (e.g., using a differential current transformer) between the current flowing through the live conductor in one direction and that returning through the neutral (N) conductor or wire in the opposite direction. In a normal circuit, the current flow via the current line equals the return flow in the neutral. However, this return flow may not be equal to the line’s current flow in the event of any abnormalities or faults. In other words, an imbalance in the current flows indicates a fault. In such an event of fault detection, an RCCB will automatically stop electricity flowing through the circuit by opening a switch within the circuit, i.e., by opening electrical contacts within the circuit. Hence the condition of the electrical contacts of the RCCB is crucial to the effectiveness and safety of the device.

The IEC 61008-1 product standard mandates the need for periodic testing of RCCBs to ensure human safety.

[0004] Some RCDs (including RCCBs and RCBOs) have an automatic mechanism for carrying out testing of the RCD by automatically activating a tripping mechanism and causing contact movement that opens the switch without the need for manual operation.

[0005] For devices with such an automatic testing function, it is desirable to be able to automatically close the switch after testing in response to a remote signal (e.g., when automatically testing the RCD, or for remote operation of the switch). [0006] DE102005024270B3 describes remote actuation of a circuit breaker device.

EP1487003B1 describes an automatic reset device for untimely tripping of a circuit breaker device. It is desirable to provide other auto-close or automatic recloser devices suitable for use with RCDs, which can be remotely activated or actuated.

Summary

[0007] An automatic recloser device for use with a residual current device, and a method for operating the automatic recloser device, is provided, wherein the residual current device comprises a switch which can be opened or closed by rotation of a first knob of the residual current device.

[0008] In a first aspect of the present disclosure, a device is provided in the appended independent apparatus claim, with optional features defined in the dependent claims appended thereto. In a second aspect, a method is provided of operating the device of the first aspect as defined in the appended independent method claim. Any features of the first aspect may be implemented as part of the method of the second aspect.

[0009] The device provided in the first aspect is an automatic recloser device for use with a residual current device, the residual current device comprising a switch which can be opened or closed by rotation of a first knob of the residual current device. The automatic recloser device comprises a housing at least partially enclosing a piezoelectric motor and a mechanical linkage, which is arranged between the piezoelectric motor and the first knob (of the residual current device). The mechanical linkage is coupled to the piezoelectric motor and comprises a first rigid member configured to engage with the first knob. The piezoelectric motor is configured to apply a force in a first linear direction to move the mechanical linkage; the movement of the mechanical linkage causes a rotation of the first knob in a first rotational direction, thereby closing the switch.

[0010] In this way, an automatic recloser device that is reliable, simple, and easy to construct and assemble maybe provided. The use of piezoelectric motors also provides many advantages. Piezoelectric motors have a very good power to size ratio. This can allow the automatic recloser device to be compact enough to meet design requirements (including retrofitting to existing RCDs). Moreover, piezoelectric motors have high holding torque at zero input power and allow for rapid start and stop. Therefore, rapid closing of the switch can be provided byway of the piezoelectric motor, facilitating rapid completion of the circuit in response to a tripping event, for example, after an auto-testing operation. [oon] In particular, this advantage of piezoelectric motors may be contrasted with thermal actuators, which are relatively slow. Furthermore, piezoelectric motors do not produce magnetic fields and are unaffected by external magnetic fields. This means that the operation of the piezoelectric motor can be unhindered by possible electromagnetic fields produced in the environment of the automatic recloser device and also can ensure that the operation of the piezoelectric device does not interfere with the operation of other electrical devices in the environment of the piezoelectric motor. In particular, this constitutes an advantage of piezoelectric motors as compared to, for example, induction motors in the context of high-current environments. In addition, piezoelectric motors operate at ultrasonic frequencies. Therefore, the operation of a piezoelectric motor does not produce much sound that is perceptible to the human ear. This can help to ensure lower noise pollution in the environment of the operation of the automatic recloser device.

[0012] The mechanical linkage is configured such that the application of the force in the first linear direction on it by the piezoelectric motor causes it to move in such a manner as to cause a rotation of the first knob in a first rotational direction, thereby closing the switch. In this way, the mechanical linkage solves the problem of how one may transfer linear motion created by the piezoelectric motor into the rotational motion required to close the switch. In some examples, given space constraints, the piezoelectric motor cannot supply enough force to operate the first knob. In such examples and more generally, the mechanical linkage may be designed to confer a mechanical advantage. The automatic recloser device disclosed herein provides a simple, reliable, and efficient mechanism to facilitate the remote closing of a switch of a residual current device. [0013] The mechanical linkage is configured to engage with the first knob via a first rigid member. In some examples, the first rigid member engages with the first knob within the housing of the automatic recloser device. In other examples the first rigid member protrudes from the housing to engage with the first knob. Optionally, the first rigid member can comprise a second knob that is configured to engage with the first knob.

[0014] In such examples, the second knob is configured such that when the piezoelectric motor applies the force in the first linear direction, the second knob rotates in the first rotational direction and engages with the first knob to cause the rotation of the first knob in the first rotational direction. The axis of rotation of the first knob and the second knob may be substantially parallel. In some examples, the two axes may coincide, so that the rotation axes of the first knob and the second knob are coaxial. Conversely, when the piezoelectric motor applies a force in a second linear direction opposite the first linear direction, the second knob is configured to rotate in a second rotational direction opposite the first rotational direction but does not engage with the first knob. Therefore, the first knob does not rotate in the second rotational direction in response to the rotation of the second knob in the second rotational direction. In this way, automatic reclosing of the RCD can be facilitated, without otherwise affecting operation of the RCD.

[0015] Examples in which the mechanical linkage engages with the first knob via a second knob protruding from the housing of the automatic recloser device can allow for the first knob to be accessible to a user or operator. Such a configuration may allow for manual actuation of the first knob, and thereby manual operation of the switch.

[0016] In some examples, the first knob can be manually actuated in the second rotational direction by a user, thereby opening the switch. Such a manual operation of the switch may be required, for example, for maintenance purposes. Optionally, the first knob can be manually actuated in the first rotational direction by the user, thereby closing the switch. For example, the second knob may comprise one or more apertures, recesses or cut-outs configured to allow access to the first knob by the user. In such examples, the manual actuation of the first knob to close the switch is independent of rotation of the second knob. [0017] In general, allowing for manual means of operating the switch to open and/or close it provides greater flexibility to the user and maybe necessary in certain contexts, such as for maintenance purposes or as a backstop.

[0018] The piezoelectric motor may comprise a motor shaft and the piezoelectric motor may be configured to apply the force to move the mechanical linkage via the movement of the motor shaft. Such a configuration can allow for a simple and efficient mechanism for transferring force from the piezoelectric motor to the mechanical linkage. Alternatively, the piezoelectric motor may comprise a plate, or any other appropriately shaped part, whose movement applies the force to move the mechanical linkage. [0019] The mechanical linkage may comprise a lever mechanism. For example, the first knob may be rotated by a lever action. A lever mechanism can provide for a simple and reliable mechanism for gaining a mechanical advantage.

[0020] In some examples, the mechanical linkage comprises a scotch yoke mechanism. The scotch yoke mechanism comprises a sliding yoke having a slot, and a pin configured to engage with the slot of the sliding yoke. The first rigid member comprises the pin. In other examples, the scotch yoke mechanism comprises a sliding yoke having a pin, the pin configured to engage with a slot of (or formed in) the first rigid member. A scotch yoke mechanism is a simple and efficient mechanism for exchanging linear and rotary motions. The scotch yoke mechanism achieves this conversion between linear and rotary motions using a simple design that requires a few parts, which makes it cheap to construct, easy to assemble, and reliable. A scotch yoke mechanism can require fewer parts and less maintenance than other mechanisms, such as a gear system. Moreover, a scotch yoke mechanism may be faster at transmitting force than a gear system.

[0021] In examples comprising a scotch yoke mechanism, the sliding yoke may be rigidly coupled to the piezoelectric motor, and the pin may be configured to engage with the slot of the sliding yoke to rotate the first rigid member in response to the linear movement of the sliding yoke. Such examples provide a simple and reliable means of closing the switch by rotating the first knob.

[0022] In some such examples, the device may further comprise a resilient member, such as a spring. The resilient member may be coupled at one end to the sliding yoke and may be fixedly coupled at the other end to the housing. The resilient member may be configured to bias the sliding yoke to move in the first linear direction. The resilient member maybe resilient through form and/or material.

[0023] Optionally, the resilient member is a spring. Optionally, the spring is a tension or extension spring. A resilient object such as a spring is a simple to construct or source component that is cheap, durable, and relatively maintenance-free. In addition, use of a resilient member allows for the loading of forces that can allow for accelerating the operation of the automatic recloser device in closing the switch.

[0024] In other example automatic recloser devices, the mechanical linkage has a first end and a second end and may comprise a plurality of rigid members extending between the first end and the second end. The first rigid member (of the plurality of rigid members) may be arranged at the second end, and the plurality of rigid members may be pivotably coupled to one another in sequence.

[0025] Such linkage mechanisms are simple to design and construct. Moreover, they may provide efficient means of gaining mechanical advantage, can be faster at transmitting force, and can require fewer parts and less maintenance than a gear system.

[0026] Some automatic recloser devices described herein may comprise a transverse rigid member that may be arranged between and coupled to the mechanical linkage and the piezoelectric motor. The transverse rigid member may be arranged to offset the mechanical linkage from the piezoelectric motor in a direction perpendicular to the first linear direction. This may allow for a more compact design, in which the offset mechanical linkage and the piezoelectric motor can partially overlap (and so need not be placed one after the other in the first linear direction).

[0027] In some examples, the piezoelectric motor may be pivotably coupled to the first end of the mechanical linkage so as to form a slider-crank four bar linkage.

Additionally, or alternatively, the mechanical linkage may form a Grashof s four bar linkage at the second end, and the first rigid member may be configured to rotate in response to the force from the piezoelectric motor that is transmitted using the Grashof s four bar linkage. In some other examples, the piezoelectric motor (may be pivotably coupled to the first end of the mechanical linkage so as to form a slider-crank four bar linkage, and the mechanical linkage forms a five bar linkage at the second end; the first rigid member is configured to rotate in response to the force from the piezoelectric motor using the five bar linkage. In yet further examples, the mechanical linkage may form a five bar linkage, wherein the piezoelectric motor may be pivotably coupled to the first end of the mechanical linkage, and wherein the first rigid member may be configured to rotate in response to the force from the piezoelectric motor that is transmitted using the five bar linkage. Such configurations can provide efficient, durable, resilient, and simple force transfer mechanisms.

[0028] In some examples, the first end of the mechanical linkage may comprise a slot. An engagement pin coupled to the piezoelectric motor may be configured to pivotably and slidably engage with the slot to drive the mechanical linkage. For example, the pin may engage with the slot to drive a five bar linkage. Such a configuration can help to provide greater design flexibility. For example, the position and length of the slot may be adjusted to provide greater mechanical advantage. [0029] In some examples, the automatic recloser device further comprises a resilient member, wherein the resilient member is coupled at one end to the mechanical linkage and fixedly coupled at the other end to the housing. The resilient member is configured to bias the mechanical linkage so as to bias the rotation of the first knob in the first rotational direction. The resilient member can be coupled between any link of the mechanical linkage and the housing. More than one resilient member may be provided. For example, the resilient member can be coupled between the first rigid member and the housing and/ or between any one rigid member (of the other plurality of rigid members) and the housing. In other examples, the resilient member can be coupled between the first rigid member and the housing and/or between the sliding yoke mechanism. [0030] Also disclosed herein is a method of using the automatic recloser device of the first aspect. The method comprises: activating the piezoelectric motor to apply the force in the first linear direction, thereby causing the mechanical linkage to move; and rotating the first knob in the first rotational direction response to the movement of the mechanical linkage, thereby closing the switch.

[0031] Also disclosed herein is a system comprising a residual current device with a switch, wherein the switch can be opened or closed by rotation of a first knob, and an automatic recloser device of the first aspect. Brief description of the figures

[0032] Figure 1 illustrates, schematically, a front view of an example automatic recloser device.

[0033] Figures 2A-E relate to a first example automatic recloser device with the mechanical linkage comprising a scotch yoke mechanism and a spring. Figures 2A and 2B illustrate the first example automatic recloser device in two different configurations. Figure 2C provides a front view of the first example automatic recloser device. Figures 2D and 2E show the modelled torque as a function of the angle of rotation for different starting angles.

[0034] Figures 3A-G relate to a second example automatic recloser device wherein the mechanical linkage comprises a plurality of rigid members that are pivotably coupled to one another in sequence. The mechanical linkage is pivotably coupled to the piezoelectric motor at one end to form a slider-crank four bar linkage and the mechanical linkage forms a Grashof s four bar linkage at the other end. Figures 3A and 3B illustrate the second example automatic recloser device in two different configurations. Figure 3C provides a schematic illustration of a part of the mechanical linkage of the second example automatic recloser device. Figures 3D and 3E illustrate a front view of the second example automatic recloser device, while Figure 3F illustrates a side view of the second example automatic recloser device. Figure 3G shows the modelled torque as a function of the angle of rotation. [0035] Figures 4A-G relate to a third example automatic recloser device wherein the mechanical linkage comprises a plurality of rigid members that are pivotably coupled to one another in sequence and the mechanical linkage forms a five bar linkage. The mechanical linkage is pivotably coupled to the piezoelectric motor at one end and the first rigid member is pivotably coupled at the other end of the mechanical linkage so as to rotate in response to the force from the piezoelectric motor using the five bar linkage. Figures 4A and 4B illustrate the third example automatic recloser device in two different configurations. Figure 4C provides a schematic illustration of a part of the mechanical linkage of the third example automatic recloser device. Figures 4D and 4E illustrate a front view of the third example automatic recloser device, while Figure 4F illustrates a side view of the third example automatic recloser device. Figure 4G shows the modelled torque as a function of the angle of rotation.

[0036] Figures 5A-F illustrate, from different perspectives and in different configurations or states, an example system comprising a residual current device and an automatic recloser device as disclosed herein. Detailed description

[0037] The present disclosure provides an automatic recloser device for use with a residual current device, allowing for the remote closing of a switch of the residual current device. The switch of the residual current device (RCD) can be opened or closed by rotation of a first knob. The automatic recloser device is configured to engage with the first knob to actuate the switch of the RCD.

[0038] The first knob may also be called the residual current device knob, or simply the “RCD knob” and is a projecting or protruding part of the residual current device for controlling or actuating the switch of the residual current device. The first knob can be operated/actuated manually. [0039] Figure 5B illustrates an example residual current device 500 with a first knob 502 that may be used for opening or closing the switch of the residual current device 500. Also illustrated is an automatic recloser device too comprising a first rigid member, the first rigid member here comprising a second knob 108 that protrudes from the housing of the automatic recloser device too and is configured to engage with the first knob 502.

[0040] Figure 1 illustrates an example automatic recloser device too for use with a residual current device 500. The automatic recloser device too comprises a housing 110 at least partially enclosing a piezoelectric motor 102 and a mechanical linkage 104 arranged between the piezoelectric motor 102 and the first knob 502 of the residual current device 500.

[0041] The piezoelectric motor 102 can optionally be controlled by a piezoelectric driver (not shown). A piezoelectric driver is an amplifier type power supply selected for the stable driving of each piezo element of the piezoelectric motor 102. Operation of a piezoelectric motor 102, or piezo / PZ motor, is based on the change in shape of a piezoelectric material when an electric field is applied, as a consequence of the converse piezoelectric effect. An electrical circuit makes acoustic or ultrasonic vibrations in a piezoelectric material (for example, zirconate titanate, lithium niobate or other singlecrystal materials), which can produce linear or rotary motion depending on the mechanism. Any suitable piezo motor design or mechanism may be used. Piezoelectric motors typically use a cyclic stepping motion, which allows the oscillation of the crystals to produce a large displacement motion (as opposed to most other piezoelectric actuators where the range of motion is limited by the static strain that may be induced in the piezoelectric element).

[0042] With reference to Figure 1, the mechanical linkage 104 is coupled to the piezoelectric motor 102 and comprises a first rigid member 106 configured to engage with the first knob 502. In some examples, such as that illustrated in Figure 1, the first rigid member 106 comprises a second knob 108 (or an automatic recloser device knob or simply an “ARD knob”) that protrudes from the housing 110 to engage with the first knob 502. In other examples, the first knob maybe arranged within the housing 110, and the first rigid member may engage with the first knob within the housing. [0043] The piezoelectric motor 102 is configured to apply a force F in a linear direction (114a or 114b) to move the mechanical linkage 104. In turn, the movement of the mechanical linkage 104 causes a rotation of the first knob 502 in a rotational direction (116a or 116b). In the following description (unless otherwise stated), movement in a first linear direction 114a causes rotation in a first rotational direction 116a, thereby closing the switch. However, it will be understood that, depending on the arrangement of the linkage and/ or the switch movement in linear direction 114a may instead be configured to cause rotation in the opposite rotational direction 116b (or similarly, movement in linear direction 114b causes rotation in direction 116a).

[0044] In some examples comprising a second knob 108, the rotation of the first knob 502 in the first rotational direction 116a may be caused by a rotation of the second knob 108 in the first rotational direction around an axis 118.

[0045] The piezoelectric motor 102 may comprise a movable motor shaft 112. The term “shaft” (or “pole” or “rod”) used herein refers to a rigid object long in relation to its width. The cross-section of a shaft maybe circular or polygonal. Alternatively, the cross-section of a shaft may be any appropriate shape.

[0046] In the example illustrated in Figure 1, the piezoelectric motor 102 is configured to apply the force F to move the mechanical linkage 104 via the movement of a motor shaft 112 in a linear direction 114a or 114b. Alternatively, the piezoelectric motor 102 may apply the force F to move the mechanical linkage 104 via the movement of any part of the piezoelectric motor 102, such as, for example, a plate, a block, or any other appropriately shaped part designed for the function of applying a force to move the mechanical linkage 104.

[0047] The term “mechanical linkage” used herein refers to any mechanical structure that achieves the result whereby in response to a linear force F exerted by the piezoelectric motor 102 in a linear direction (114a or 114b), the mechanical linkage 104 moves so as to cause a rotation of the first knob 502 in a rotational direction (116a or 116b). Put another way, with reference to Figure 1, the mechanical linkage 104 is any mechanical structure that converts a force F output by the piezoelectric motor 102 in a first linear direction 114a into an appropriate force on the first knob 502 so as to move it in the first rotational direction (116a), thereby closing the switch. An appropriate force on the first knob 502 is any force that is capable of rotating the first knob 502 so as to close the switch. In some examples the mechanical linkage 104 is designed to confer a mechanical advantage (for example, byway of a lever mechanism); that is the force applied on the first knob 502 is greater than the force F exerted by the piezoelectric motor 102 to move the mechanical linkage 104. This can allow for a smaller PZ motor (which is anyway more compact than other motors, such as for example an induction motor), and thus the design of a more compact automatic recloser device too. Therefore, when combined with a PZ motor, the mechanical advantage provided by the mechanical linkage 104 maybe particularly advantageous. [0048] As will become apparent below, there are many possible mechanical structures or configurations that achieve the technical effect of converting a force F output by the piezoelectric motor 102 in a linear direction 114a or 114b into an appropriate force on the first knob 502 so as to move it in the first rotational direction (116a or 116b). The mechanical linkage 104 may consist of a number of different components that are arranged and coupled to one another and coupled to the piezoelectric motor 102 in a number of different ways. Moreover, the mechanical linkage 104 maybe configured to engage with the first knob 502 via the first rigid member 106 in number of ways.

[0049] For example, the mechanical linkage 104 may be configured such that a force F applied by the piezoelectric motor 102 on the mechanical linkage 104 in a linear direction 114a causes a rotation of the first knob 502 in the first rotational direction (116a). Alternatively, as discussed above, the mechanical linkage 104 maybe configured such that a force F applied by the piezoelectric motor 102 on the mechanical linkage 104 in a linear direction 114b causes a rotation of the first knob 502 in the first rotational direction (116a). In the following examples, the first linear direction is direction 114a, and the first rotational direction is direction 116a; the second linear direction is direction 114b, opposite direction 114a, and the second rotational direction is direction 116b, opposite direction 116a.

[0050] The mechanical linkage 104, or a subset of the components that constitute it, may be formed from a polymer. Polymers are cost-effective, abundant, durable, lightweight and safe materials to work with. They have design flexibility and economies of scale. Optionally, the polymer is a plastic. Alternatively, mechanical linkage 104 or a subset of the components that possibly constitute it maybe constructed from metal, or any other material, depending on design requirements.

[0051] The mechanical linkage 104, or a subset of the components that constitute it, may be manufactured using an injection moulding process. The advantages of injection moulding include its compatibility with a wide range of materials, its efficiency, repeatability, reliability and importantly the fact that it allows for complex geometries with high tolerances. In other examples, the components maybe manufactured using an additive manufacture process (such as 3D printing), compression moulding, vacuum casting, carving or any other suitable method. The method of manufacture may be chosen based on design requirements.

[0052] Figures 5A and 5B show an example system 600 comprising an example automatic recloser device too and a residual current device 500 from two different perspectives. With reference to Figure 5B, the example automatic recloser device too may be positioned in front of (or on a front of) the residual current device 500. Figure

5A illustrates the same configuration as in Figure 5B, but from a perspective corresponding to a view of the system from behind the residual current device 500.

The residual current device 500 comprises a first knob 502 that is coupled to a switch of the residual current device 500. The first knob 502 maybe used to open or close the switch. In the arrangement of Figures 5A, 5B, the switch is closed and the device too is in a default position.

[0053] The mechanical linkage 104, at least partially enclosed within the housing 110 of the automatic recloser device too, comprises a first rigid member 106 configured to engage with the first knob 502. In some examples, the mechanical linkage 104 is fully enclosed within the housing 110 of the automatic recloser device too. In such examples (not shown in the Figures), the first knob 502 of the residual current device 500 maybe configured to penetrate the housing 110 of the automatic recloser device too.

[0054] In alternative examples, such as the automatic recloser device too depicted in Figures 5A and 5B, the first rigid member 106 may comprise a second knob 108 that protrudes from the housing 110 of the automatic recloser device too and is configured to engage with the first knob 502. As shown, the second knob comprises an engagement portion 506 which is configured to “catch” the first knob 502 in one rotational direction, but not in the opposite rotational direction. Here, the engagement portion 506 protrudes from the body of the second knob 108 to catch or engage with the first knob. In some examples, the second knob 108 may be integrally formed within the mechanical linkage 104, so that it maybe more appropriate to view the second knob 108 as an extension of the mechanical linkage 104.

[0055] In examples where the mechanical linkage 104 engages with the first knob 502 exterior to the housing 110 via a second knob 108, the first knob 502 may remain accessible to a user or operator. For example, a user may manually actuate the first knob 502 in a second rotational direction 116b to open the switch. The user may also manually actuate the first knob 502 in the first rotational direction to close the switch independent of the functioning of the automatic recloser device too. The engagement portion 506 may comprise on or more openings, apertures or cut-outs (not shown) to facilitate access to the first knob by a user. Alternatively, the automatic recloser device too may be designed, for example with safety or security considerations in mind, not to allow the user to close the switch manually. For example, in the example shown the engagement portion 506 prevents access to the first knob when the switch is open; in other words, the first knob 502 maybe hidden by the second knob 108 when the switch is open, thus preventing manual access to it.

[0056] The actuation (rotation) of the first knob 502 by a user or operator is caused by an application of a force on the first knob 502 by the user or operator. For example, the force applied may be in a rotational direction that corresponds with the desired direction of rotation of the first knob 502. [0057] With reference to Figure 1 and Figures 5A-F, an example use of the automatic recloser device too together with a residual current device 500 is described in more detail.

[0058] In normal operation, the switch of the residual current device 500 is closed and the circuit is complete, allowing electricity to flow. Such a state, which we denote Sc, of the residual current device 500 is depicted in Figures 5A and 5B. Similarly, when not in operation, the automatic recloser device too is in a neutral or default state, which we denote A_o, as depicted in Figures 5A and 5B. As illustrated schematically in Figures 5A and 5B, when the residual current device 500 (or equivalently all the components of the residual current device 500, including the switch and the first knob 502) are in state Sc and the automatic recloser device too (or equivalently all the components of the automatic recloser device too, including the piezoelectric motor 102 and the mechanical linkage 104) are in state A_o, the first knob 502 and the second knob 108 are decoupled.

[0059] When a current fault event occurs, e.g. arising from a testing procedure or from the designed safety operation of the residual current device 500, the event causes the switch to trip (i.e. , to open), thereby breaking the circuit. Alternatively, the opening of the switch may be caused by the manual actuation of the first knob 502 by a user. When the switch is opened, the residual current device 500 transitions into a state So, as illustrated in Figures 5C and 5D. In this state, the first knob 502 is in a position in which it is configured to be engaged by the second knob 108. Note that the automatic recloser device too remains in state A_o. The opening of the switch is decoupled from the operation of the device too.

[0060] In the configuration illustrated schematically in Figures 5C and 5D, the first knob 502 and the second knob 108 are in direct physical contact. Alternatively, the first knob 502 and the second knob 108 may be spaced apart, such that the second knob 108 moves a threshold distance before engaging the first knob. Furthermore, when the residual current device 500 is in state So and the automatic recloser device too is in state o, the first knob 502 maybe hidden from the user by the second knob 108 (as shown), preventing access to the user in order to actuate the first knob 502.

The system may be so designed for safety or security reasons. Alternatively, the design of the second knob 108 and/ or the position the first knob 502 in state So may be such as to allow the user to access the first knob 502 and actuate it. In such example systems, the user may, for example, reclose the switch of the residual current device 500 manually independent of the operation of the automatic recloser device too. That is, the use may return the residual current device 500 to the state Sc while the automatic recloser device too remains in state A_o.

[0061] Continuing from the configuration in which the residual current device 500 is in open state So and the automatic recloser device too is in default state A_o, the residual current device 500 may be remotely restored to the state Sc, that is the switch maybe reclosed, using the automatic recloser device too. [0062] In order to actuate or rotate the first knob 502 to close the switch remotely, the automatic recloser device too may be remotely operated to transition the automatic recloser device too from the state A_o to a state AL With reference Figure 1, the piezoelectric motor 102 is activated, for example in response to a signal from a microprocessor or other controller (e.g. a control module) of the device too, to apply a force F in a first linear direction 114a to move the mechanical linkage 104. The activation can be triggered by a remote signal received wirelessly or over a wired connection, for example from a remote operator, or by an automatic signal from the RCD. The movement of the mechanical linkage 104 in direction 114a then causes a rotation of the first knob 502 in a first rotational direction 116a, thereby closing the switch. [0063] In the example system 600 depicted in Figures 5C and 5D, the movement of the mechanical linkage 104 comprises the rotation of the second knob 108 in the first rotational direction 116a about an axis of rotation (e.g. axis 118 of Figure 1). The rotation of the second knob 108 in the first rotational direction then causes the rotation of the first knob 502 in the first rotational direction 116a. The axis of rotation of the first knob 502 may also correspond to axis 118, i.e., the first knob 502 and the second knob 108 may be coaxial. Alternatively, the axis of rotation of the first knob 502 and the axis of rotation of the second knob 108 may be parallel or substantially parallel. [0064] The second knob 108 may cause the first knob 502 to rotate by catching or latching on to it by means of engagement portion 506. Portion 506 can comprise a protrusion or lip that is configured to engage with or otherwise catch the first knob 502 when the second knob 108 comes into contact the first knob 502 during the rotational motion in first direction 116a.

[0065] When the first knob 502 rotates to reach a position in which the switch closes, the system 600 transitions to a configuration as depicted in Figures 5E and 5F. Therefore, Figures 5E and 5F depict a configuration in which the residual current device 500 is in state Sc and the automatic recloser device too is in an active state A_t. [0066] Now that the residual current device 500 is once more in state Sc and the switch has reclosed, the automatic recloser device too may be configured to return to the state o so that it is ready to reclose the switch again on a future occasion. [0067] In order to transition the state of the automatic recloser device too from state i to state A_o, the piezoelectric motor 102, may be activated to apply a force F on the mechanical linkage 104 in a second linear direction 114b opposite the first linear direction. The mechanical linkage 104 moves in response to the application of force by the piezoelectric motor 102 and in doing so returns to its original state prior to the application of force by the piezoelectric motor 102 in the first linear direction. As the mechanical linkage 104 moves in response to the application of force by the piezoelectric motor 102 in the second linear direction, the mechanical linkage 104 does not engage with the first knob 502. That is the first knob 502 does not move or rotate in the second rotational direction, and instead remains in a position corresponding to that in which the switch is closed. In other words, the residual current device 500 remains in the state Sc- [oo68] In examples in which the first rigid member 106 comprises second knob 108, such as that depicted in Figures 1 and 5A-F, the second knob 108 rotates in a second rotational direction 116b opposite the first rotational direction in response to the application of the force by the piezoelectric motor 102 in the second linear direction 114b. Moreover, as it does so, the second knob 108 does not engage the first knob 502, i.e., it does not cause the first knob 502 to move or rotate in the second rotational direction. The first and second knobs are decoupled or disengaged.

[0069] Once the automatic recloser device too transitions to the state A_o, the system 600 returns to the state depicted in Figures 5A and 5B. In this state the residual current device 500 is in state Sc, that is the switch is closed, and the automatic recloser device too is in default state A_o.

[0070] The skilled person will appreciate that the automatic recloser device too depicted in Figure 1 is solely schematic and intended to illustrate the essential components of an automatic recloser device too as disclosed herein, as well as some optional features. A working device too may contain further components or may relinquish some of the optional features depicted in Figure 1, such as the second knob 108 or the motor shaft 112.

[0071] Moreover, the skilled person will appreciate that the system 600 comprising an example automatic recloser device too and a residual current device 500 as depicted in Figures 5A-F is solely intended to illustrate one such example system. The automatic recloser device too may be configured in any one of a number of ways when in use with a residual current device 500, depending on design requirements and/or restrictions that exist in situ.

[0072] Figures 2A-E relate to an example automatic recloser device too with the mechanical linkage 104 comprising a scotch yoke mechanism and a resilient member, such as a spring.

[0073] Figures 2A and 2B illustrate the example automatic recloser device too in two different configurations that correspond to the two different states A_o and ₂, respectively. The state A_o of Figure 2A may be described as the default or “neutral” state in which the automatic recloser device too has not been activated.

[0074] A scotch yoke mechanism is a mechanical mechanism for converting a linear motion into a rotational motion, and vice versa. In this example, the scotch yoke mechanism comprises a sliding yoke 204 and the first rigid member 106, which is configured to rotate about the rotational axis 118. The sliding yoke 204 comprises a slot 206 (sometimes called a “slider”), while the first rigid member 106 comprises a pin

210 that is configured to engage with the slot 206 of the sliding yoke 204. As the sliding yoke 204 moves in a linear direction (114a, 114b), the pin 210, which is configured to engage with the slot 206 of the sliding yoke 204, moves along (up or down) the slot 206, thereby causing the first rigid member 106 to rotate around axis 118. In other examples (not illustrated), the scotch yoke mechanism comprises a sliding yoke having a pin. The pin is configured to engage with a slot of the first rigid member (i.e., a slot formed in the first rigid member).

[0075] In the example illustrated in Figures 2A and 2B, the piezoelectric motor 102 comprises motor shaft 112 and the sliding yoke 204 is directly (and rigidly) coupled to the piezoelectric motor 102 via the motor shaft 112. In other examples, the sliding yoke 204 may be coupled to the piezoelectric motor 102 via an alternative, intermediate, arrangement. The shape of the first rigid member 106 is not limited to that depicted in Figures 2A and 2B. In order for the scotch yoke mechanism to work, the first rigid member 106 need only comprise a pin 210, configured to engage with the slot 206 of the sliding yoke 204. As such, the first rigid member 106 may take any appropriate shape. Similarly, the skilled person will appreciate that the shape of the sliding yoke 204 and the motor shaft 112 need not be limited to that depicted in Figures 2A and 2B and that many alternative shapes and arrangements are capable of fulfilling the function of applying a linear force by the piezoelectric motor 102 on the scotch yoke mechanism and, in doing so, engaging with the first knob 502 to cause its rotation in a first rotational direction.

[0076] In Figure 2A, which corresponds to the configuration of device too prior to the operation of the automatic recloser mechanism too, the motor shaft 112 is configured to move in a first linear direction 114a upon the activation of the piezoelectric motor 102. When the piezoelectric motor 102 is activated, the motor shaft 112 moves in the first linear direction 114a and in doing so exerts a force F on the sliding yoke 204. In response to the force F, the sliding yoke 204 moves in the first linear direction 114a, and in doing so causes the pin 210 to move down the slot 206. As the pin 210 moves down the slot 206, the first rigid member 106 rotates in a first rotational direction 116a, which in turn causes the first knob 502 to rotate in the first rotational direction 116a, thereby closing the switch. The first knob 502 may be caused to rotate in the rotational direction 116a by the rotation of second knob 108 in the rotational direction 116a about the axis 118, as discussed above. The second knob 108 may be integrally formed within the first rigid member 106. Once these series of actions are completed, and the switch is closed, the configuration of the automatic recloser device too corresponds to that illustrated in Figure 2B; equivalently, the automatic recloser device too is said to be in active state A_t. [0077] At this stage, the automatic recloser device too may be configured to return to its original default position, or state A_o, by performing the reverse operations to that described with respect to closing the switch by transitioning into state A_t. In particular, operations that change the configuration of the automatic recloser device too from that illustrated in Figure 2B to that illustrated in Figure 2A are performed. For example, the piezoelectric motor 102 may be activated, causing the motor shaft 112 to move in second linear direction 114b, which corresponds to the opposite of direction 114a. The movement of the motor shaft 112 along the linear direction 114b exerts a force F on the sliding yoke 204, thereby causing it to move in the second linear direction 114b. The movement of the sliding yoke 204 then causes the pin 210 to move up the slot 206, and in doing so causes the first rigid member 106 to rotate in second rotational direction 116b, which corresponds to the opposite of direction 116a. The first rigid member 106 is configured to rotate such that the configuration of the automatic recloser device too returns to that illustrated in Figure 2A. [0078] In some examples, such as that illustrated in Figures 2A and 2B, the automatic recloser device too further comprises a resilient member 202. Resilient member 202 is optionally a spring. The resilient member 202 maybe coupled at one end to the sliding yoke 204 and fixedly coupled at the other end to the housing 110. The resilient member 202 maybe configured to bias the sliding yoke 204 to move in a particular linear direction. For example, the resilient member 202 may be configured to bias the sliding yoke 204 to move in a linear direction 114a or 114b. The particular direction of the biasing may be chosen according to the design of the piezoelectric motor 102 or other functional needs.

[0079] In this example and with reference to Figure 2A, the resilient member 202 is an extension or tension spring which is configured to bias the sliding yoke 204 in the first linear direction 114a. Therefore, in the configuration depicted in Figure 2A, the resilient member 202 maybe in a substantially “loaded” state, while in the configuration depicted in Figure 2B, the resilient member 202 maybe in a substantially “unloaded” or “neutral” state. As a consequence, the resilient member 202 biases or urges the sliding yoke in the first linear direction 114a. In other examples, the resilient member 202 can be a torsion spring, or any other member which is resilient by form and/or function to bias or urge the sliding yoke. The resilient member 202 can help to overcome any inertia in the PZ motor, and can result in a faster and smoother closing of the switch. In some examples, the presence of a loaded resilient member 202 may also help to confer the necessary mechanical advantage needed to rotate the first knob 502.

For example, without the resilient member 202, the piezoelectric motor 102 may not be able to generate sufficient force required to drive the mechanical linkage 104 and cause the first knob 502 to rotate.

[0080] In an example automatic recloser device too in which the mechanical linkage 104 is combined with a resilient member 202, the resilient member 202 may be loaded as the automatic recloser device too transitions from state A to state A_o. In this step, since the device too is decoupled from the first knob, the automatic recloser device too need not operate as quickly as when it is remotely activated to close the switch. Moreover, no torque needs to be exerted on the first knob during this reverse operation, so the PZ motor can be configured to reload the resilient member without e.g. requiring a larger motor to be used in combination with said resilient member 202. [0081] An example mechanical linkage 104 comprising a scotch yoke mechanism and a preloaded spring, similar to the example illustrated in Figure 2A, may confer a mechanical advantage, thereby increasing the force applied to the first knob as compared to the force output by the piezoelectric motor 102. In other examples (not shown), the resilient member 202 can instead be coupled at one end to the first rigid member and fixedly coupled at the other end to the housing 110, wherein the resilient member 202 is configured to bias the first rigid member to rotate in the first rotational direction. The resilient member can be an extension/tensions spring, a torsion spring, or any other suitable member. In other examples, two resilient members may be used in combination, one between the sliding yoke and the housing, and one between the first rigid member and the housing. This arrangement can further improve mechanical advantage.

[0082] In some examples, the automatic recloser device too may comprise a control module 214. In such examples, the control module 214 is connected to an electronic component of the piezoelectric motor 102 and may comprise an electronic printed circuit board with various electronic components that may be used for communication and control purposes. For example, the piezoelectric motor 102 may be activated or deactivated in response to signals received from, or via, the control module 214. In addition, the control module 214 may facilitate remote communication and operation of the automatic recloser device too. Wireless communication between the automatic recloser device too and a remote user may be facilitated using short-range radio technology (such as Bluetooth), wireless networks (such as WI-FI or mobile networks, e.g., 3G, 4G, or 5G), or any other appropriate means, such as satellite communication. In some other examples, the means for communication with and/or control of the automatic recloser device too may be instead integrated into the piezoelectric motor 102. The PZ motor 102 may therefore be directly actuated. [0083] Figure 2C provides a front view of the example automatic recloser device too when in a default configuration corresponding to that depicted in Figure 2A. In this example, as well as other examples such as those illustrated in Figures 3A and 4A, the mechanism by which the first knob 502 is rotated in order to close the switch may be viewed as comprising a lever mechanism, or, more precisely, a class 2 lever mechanism.

[0084] In general, in a lever mechanism, the torque generated about the “pivot” or “fulcrum” is given by the component of the force orthogonal to the direction of the lever multiplied by the length of the lever. Therefore, the equation of torque transmission is: [0085] T = F L sin e,

[0086] where F is the force applied, L is the length of the lever, and e is the angle between the axis created by the lever and the direction in which the force is applied. [0087] Applying these general principles of a lever mechanism to the example depicted in Figure 2C, the “effort” is provided at the position of the pin 210 and the “fulcrum” is situated at the position of the axis 118 of rotation of the first rigid member

106. In this example, F is the force applied in the first linear direction 114a, L is the length of the virtual lever (which corresponds to the line between the position of the pin 210 and the axis 118), and e is the angle between the axis created by the lever 218 and the axis 216 corresponding to the linear direction 114a. [0088] The mechanical linkage 104 may be configured such that the total force applied at the pin 210 may be greater than the force F applied by the piezoelectric motor 102. In some examples, as discussed above, the mechanical linkage 104 is further combined with a resilient member 202, such as an extension or tension spring. In such a device too, the torque generated about the fulcrum is greater; in particular, with reference to the general equation for the torque generated:

[0089] T = (F + f) L sin e,

[0090] where/is the restoring force from the preloaded spring. The preloaded spring force is given by Hooke’s law:

[0091] f = k • x, [0092] where k is the spring rate or “spring constant” and x is the total displacement of the sliding yoke 204 (which displacement causes a corresponding, relaxing, displacement of the spring).

[0093] Another way in which one may increase the “effort”, or the total force applied at the position of the pin 210, is to modify the design of the sliding yoke 204. For example, the sliding yoke 204 may itself comprise a linkage mechanism that confers a mechanical advantage, thereby increasing the force applied by the piezoelectric motor 102.

[0094] The location of the pin 210 in relation to the axis of rotation 118 may also be tuned to optimise the torque generated when the piezoelectric motor 102 is activated. With reference to the equation for the torque, given above, this corresponds to tuning the values of L and e. In particular, greater lengths L and greater angles e lead to higher torques. One or more design requirements, such as the need for compactness to facilitate retrofitting to RCDs, may place upper bounds on the values of L and e.

[0095] To illustrate this further, Figures 2D and 2E show example modelled torques as a function of the angle of rotation for different starting angles e (i.e. , for arrangements or mechanisms with different angles e between the linear direction and the lever). The starting angle e in the example of Figure 2D is greater than the starting angle e in the example of Figure 2E. Thus, it can be seen that the torque curve as a function of the angle of rotation may be modified by tuning the starting angle e. [0096] In summary, the scotch yoke mechanism, with the possible addition of a resilient member 202, provides the skilled person with design flexibility to tune a number of different variables within design constraints in order to find optimal configurations for a specific application or use case. The skilled person will appreciate that the design constraints and the optimal configurations will vary depending on the particular setting or environment in which the automatic recloser device too is to be used.

[0097] Figures 3A-G relate to an example automatic recloser device too wherein the mechanical linkage 104 comprises a plurality of rigid members. A resilient member (not shown) may also be provided, coupled between one of the plurality of rigid members and the housing, to improve mechanical advantage. The resilient member can be configured to bias the mechanical linkage in any suitable direction so as to bias the first knob to rotate. The mechanical linkage has a first end and a second end, and the plurality of rigid members extend between the first end and the second end, and are pivotably coupled to one another in sequence. In this example, the first rigid member 106 (which is one of the plurality of rigid members and is arranged at the second end of the linkage) rotates in response to the activation of the piezoelectric motor 102 to apply a force in a linear direction using a double four bar linkage. The double four bar linkage comprises (in combination with the shaft of the PZ motor) a slider-crank four bar linkage at one end (i.e. at the first end, proximate the piezoelectric motor 102) and a Grashof s four bar linkage at the other, second, end (to rotate the first rigid member

106). [0098] Figure 3A illustrates an example automatic recloser device too in a state in which the automatic recloser device is neutral, i.e., in state A_o. In the example depicted in Figure 3A, the mechanical linkage 310 comprises a plurality of rigid members (106, 312, 316, 318) that are pivotably coupled to one another. [0099] Contrary to the arrangements described above, in this example the first linear direction is direction 114b. In order to transition the automatic recloser device too to state i, as shown in Figure B, the piezoelectric motor 102 is configured to apply a force F in first linear direction 114b. The piezoelectric motor 102 may comprise a motor shaft 112 through which it applies the force F to the mechanical linkage 104. Alternatively, the piezoelectric motor 102 may apply the force F to the mechanical linkage 104 using another moving part, such as a plate.

[0100] In some examples, a transverse rigid member 302 (also termed a connecting pin) may be arranged between and coupled to the mechanical linkage 104 and the piezoelectric motor 102. The transverse rigid member 302 may be arranged to offset the mechanical linkage 104 from the piezoelectric motor 102 in a direction perpendicular to the linear direction 114b. The connecting pin 302 can be arranged at any suitable point in the mechanical linkage 104 ,310 so as to offset the first rigid member 106 of the mechanical linkage from the PZ motor 102 in a direction perpendicular to the first linear direction. The connecting pin can be disposed at the first or second end of the mechanical linkage, or can be arranged between two of the plurality of rigid members so as to couple said two members in an offset manner. [0101] Figure 3A illustrates an example first rigid member 106 of the plurality of rigid members. The first rigid member is provided with a particular shape that further comprises a second knob 108, as discussed above. The shape of the first rigid member 106 and/or whether it comprises a second knob 108 is a matter of design choice, depending on space requirements and limitations.

[0102] Figure 3C provides a schematic illustration of an example linkage 310. The piezoelectric motor 102 is pivotably coupled to the rigid member 312 at a pivot point 320a. The coupling between the piezoelectric motor 102 and the rigid member 312 may be through any one of a number of optional components such as a motor shaft 112 and/or a transverse rigid member 302.

[0103] In this example, the rigid member 312 is in turn pivotably coupled to a rigid member 318 at a pivot point 320b. A pivot point coupling may also be called herein a “revolute joint”. The pivot points 32oa-d are not fixed in position and are free to move in space, subject to the constraints of the linkage. The rigid member 318 includes a fixed pivot point 322a. The fixed pivot point may be configured to be fixedly coupled to the housing no so that its position remains fixed in space. However, the rigid member 318 is configured to be able to pivot, or rotate, about the fixed pivot point 322a. For convenience, one may view the rigid member 318 as comprising two portions, 318a and 318b, either side of the fixed pivot point 322a. [0104] The linkage comprising the piezoelectric motor 102, or a movable part thereof (such as a motor shaft 112), the rigid member 312, and the portion 318a of the rigid member 318 forms a slider-crank four bar linkage. In other words, the PZ motor 102 is provided in combination with the linkage to form a slider-crank four bar linkage. [0105] A slider-crank four bar linkage is a four bar linkage that transforms a linear movement of a slider to the rotational movement of a crank. In the example illustrated in Figure 3C, the analogy of the slider may be equated with the piezoelectric motor 102, or a movable part thereof (such as a motor shaft 112), while the analogy of the crank maybe equated with portion 318a.

[0106] As the portion 318a rotates about the fixed pivot point 322a in response to the driving force applied by the piezoelectric motor 102, the portion 318b also rotates in the same direction as the portion 318a. The portion 318b is pivotably coupled to a rigid member 316 at pivot point 320c, and the rigid member 316 is in turn pivotably coupled to the first rigid member 106.

[0107] The rotation of the portion 318b in response to the application of the force by the piezoelectric motor 102 causes a chain of movements in the sequence of linkages depicted in Figure 3C, which ultimately causes the first rigid member 106 to rotate about a fixed pivot point 322b, this fixed pivot point 322b corresponding to the axis of rotation 118.

[0108] The linkage comprising portion 318b, rigid member 316 and the first rigid member 106 may form a Grashof s four bar linkage. In other words, the mechanical linkage 104, 310 forms a Grashof s four bar linkage at the second end, wherein the first rigid member 106 is configured to rotate in response to the force from the piezoelectric motor 102 using the Grashof s four bar linkage. In other arrangements (not shown), the linkage can instead be arranged so as to form a five bar linkage. In other words, the Grashof s four bar linkage shown in Figure 3C can be replaced with a five bar linkage, such that the first rigid member 106 is configured to rotate in response to the force from the piezoelectric motor 102 using the five bar linkage.

[0109] In the terminology of four bar linkage, the rigid portion 318b can be called the “input link”, the first rigid member 106 can be called the “output link”, while the virtual link 330 between the fixed pivot points 322a and 322b can be called the “ground link”, the “fixed link” or the “frame”. In some examples, the quadrilateral formed by the “links” 318b, 316, 106, and 330 forms a plane. A Grashof s four bar linkage is a four bar linkage that satisfies the Grashof condition. The Grashof condition is that the sum of the shortest and longest links in the planar quadrilateral linkage is less than or equal to the sum of the remaining two links. If the Grashof condition is satisfied, the shortest link can rotate fully with respect to a neighbouring link. In some examples, portion 318b may be the shortest link. Of course, it will be understood that the shortest link, such as portion 318b, may not be able to fully rotate in practice, given its coupling to other rigid members (such as portion 318a).

[0110] As the first rigid member 106 rotates, it causes the first knob 502 to rotate in the first rotational direction.

[0111] Thus, to summarise with reference to Figure 1A, the application of a force F by the piezoelectric motor 102 in a first linear direction 114b causes the mechanical linkage 310 to move, which in turn causes the first rigid member 106 to rotate in a first rotational direction 116a. The rotation of the first rigid member 106 causes the first knob 502 to also rotate in the rotational direction 116a, thereby closing the switch. At this point, the automatic recloser device too transitions to the configuration depicted in Figure 3B, corresponding to the state A_t.

[0112] Note that (as mentioned above), while in the example automatic recloser device too of Figure 2A a linear force in linear direction 114a is required to rotate the first rigid member 106 (and consequently the first knob 502) in rotational direction

116a, in the example automatic recloser device too of Figure 3A a force in the opposite linear direction to 114a, namely direction 114b, is required to rotate the first rigid member 106 (and consequently the first knob 502) in the rotational direction 116a.

[0113] Starting from the configuration depicted in Figure 3B (state A , in order to return the state of the automatic recloser device too to the configuration depicted in

Figure 3A, i.e. to state A_o, the piezoelectric motor 102 maybe activated to apply a force F in second linear direction 114a opposite the first linear direction 114b. Since the piezoelectric motor 102 is pivotably coupled to the mechanical linkage 310, optionally through a motor shaft 112 and/or a transverse rigid member 302, the application of the force F causes the mechanical linkage 310 to move in an analogous way to that described in detail with reference to Figure 3C above. The movement of the mechanical linkage 310 causes the first rigid member 106 to rotate in second rotational direction 116b opposite the first rotational direction 116a without engaging with the first knob 502. At this point, the automatic recloser device too transitions back to the configuration depicted in Figure 3A. [0114] With reference to Figures 3A and 3B, the automatic recloser device too may optionally further comprise a control module 214 and/ or a second knob 108 as have been described above. In the example device too illustrated in Figures 3A and 3B, the second knob 108 is integrally formed within or as part of the first rigid member 106. [0115] Figures 3D and 3E illustrate alternate front views of the example automatic recloser device too, and correspond to the configurations depicted in Figures 3A and 3B, respectively.

[0116] Figure 3F illustrates a side view of the example automatic recloser device.

With reference to Figure 3F, the mechanical linkage 310 maybe designed to be compact. The width may be reduced as compared to existing devices. In some specific examples, the mechanical linkage 310 may require as little as 6mm, optionally as little as 5.9mm in the width direction (i.e. in the direction in which the axis of rotation 118 lies). Together with the piezoelectric motor 102, as well as other possible components, such as a control module 214, an example automatic recloser device too may be designed with a width of 40mm, optionally 36mm or less. Note, with reference to

Figure 5B, that the length and height of the automatic recloser device too may generally match that of the residual current device 500 to facilitate retrofitting. A compact device too may therefore be provided.

[0117] The linkage 310 provides a mechanical advantage, thereby increasing the force applied to the first knob as compared to the force output by the piezoelectric motor 102. Figure 3G shows an example modelled torque exerted on the first rigid member 106 as a function of the angle of rotation for an example automatic recloser device too as is depicted in Figure 3A. Thus it will be understood that the mechanical linkage of an automatic recloser device too may be designed to generate the required torque necessary to facilitate an auto-close function for the device too. As such, a device can be provided which operates rapidly and reliably.

[0118] The mechanical advantage gained in using the design of the mechanical linkage 310, as depicted in Figure 3C, maybe the same in transitioning from state A_o to i as in transitioning from state A₂ to A_o. Thus, the example automatic recloser device too of Figures 3A and 3B may operate with the same speed in returning to the state A_o as in reclosing the switch.

[0119] The skilled person will appreciate that the linkage mechanism depicted schematically in Figure 3A-C can allow for design flexibility. For example, the number of rigid members, the lengths of each of the rigid members, and/or the position of the fixed pivot points may each be tuned to satisfy desired design requirements and/ or design limitations. [0120] Figures 4A-G relate to another example automatic recloser device too wherein the mechanical linkage 104 comprises a plurality of rigid members that extend between a first end and a second end and are pivotably coupled to one another in sequence. A resilient member (not shown) may also be provided, coupled between one of the plurality of rigid members and the housing, to improve mechanical advantage.

The resilient member can be configured to bias the mechanical linkage in any suitable direction so as to bias the first knob to rotate. In this example the mechanical linkage 104 forms a five bar linkage. The mechanical linkage 104 is pivotably coupled to the piezoelectric motor 102 at one, first, end and the first rigid member 106 is configured to rotate at the other, second, end in response to a force from the piezoelectric motor 102 using the five bar linkage.

[0121] Figure 4A illustrates an example automatic recloser device too in the neutral state A_o. Figure 4B shows the device too in the active state AL Figures 4D and 4E illustrate a front view of the example automatic recloser device too, and correspond to the configurations depicted in Figures 4A and 4B, respectively.

[0122] In the event of a tripping or opening event, the automatic recloser device too is configured to remotely reclose the switch as follows: the piezoelectric motor 102 applies a force F in first linear direction 114a. The piezoelectric motor 102 may comprise a motor shaft 112 through which it applies the force F to the mechanical linkage 410. Alternatively, the piezoelectric motor 102 may apply the force F to the mechanical linkage 410 using another moving part, such as plate.

[0123] In some examples, a transverse rigid member 302 (also termed a connecting pin) may be arranged between and coupled to the mechanical linkage 410 and the piezoelectric motor 102. The transverse rigid member 302 may be arranged to offset the mechanical linkage 410 from the piezoelectric motor 102 in a direction perpendicular to the linear direction 114a. The connecting pin 302 can be arranged at any suitable point in the mechanical linkage 104, 410 so as to offset the first rigid member 106 of the mechanical linkage from the PZ motor 102 in a direction perpendicular to the first linear direction. The connecting pin can be disposed at the first or second end of the mechanical linkage, or can be arranged between two of the plurality of rigid members so as to couple said two members in an offset manner.

[0124] In the example depicted in Figure 4A, and with reference to Figure 4C, the mechanical linkage 410 comprises a plurality of rigid members (106, 412, 416, 418) that are pivotably coupled to one another in sequence. The plurality of rigid members of the mechanical linkage 410 may comprise a rigid member with a slot. An engagement pin 440 coupled to the piezoelectric motor 102 may be configured to pivotably and slidably engage with the slot.

[0125] Figure 4C provides a schematic illustration of an example of such a mechanical linkage 410. The mechanical linkage 410 here comprises rigid member 412 with a slot 414. An engagement pin 440 coupled to the piezoelectric motor 102 may be configured to pivotably and slidably engage with the slot 414. The engagement pin 440 maybe directly coupled to a moving part of the piezoelectric motor 102. For example, the engagement pin 440 may constitute a protrusion of a motor shaft 112.

Alternatively, if the automatic recloser device too comprises a transverse rigid member 302, the transverse rigid member 302 may comprise the engagement pin 440.

[0126] The rigid member 412 may further comprise a fixed pivot point 422a. The fixed pivot point 422a may be rigidly coupled to the housing 110. Given the presence of a fixed pivot point 422a, for illustrative purposes, the rigid member 412 can be considered as comprising two portions 412a and 412b, as is schematically depicted in Figure 4C.

[0127] In some examples, as the piezoelectric motor 102 applies a force F in a linear direction, the engagement pin 440 to which the piezoelectric motor 102 is coupled moves along the slot 414. More precisely, the rigid member 412 moves up or down relative to the pin, such that the slot slides along the pin. This causes the portion 412a to rotate about the fixed pivot point 422a, and in so doing causes the portion 412b to also rotate about the fixed pivot point 422a in the same direction. The portion 412b may be pivotably coupled to a rigid member 416 at a pivot point 420a. A pivot point coupling may also be called a “revolute joint”. The pivot points 42oa-b are not fixed in position and are free to move in space. Similarly, the rigid member 416 maybe pivotably coupled to a rigid member 418 at a pivot point 420b.

[0128] The rigid member 418 is rigidly coupled to the first rigid member 106 of the plurality of rigid members. As the portion 412b moves in response to the force applied by the piezoelectric motor 102, it causes the rigid member 416 and 418 to move in turn; as a result, the first rigid member 106 is caused to rotate about a fixed pivot point 422b corresponding to the axis of rotation 118.

[0129] The analogy with five bar linkage may be made clear by identifying the five “links” that are connected together to form a closed chain, as is the case in five bar linkage mechanisms, as corresponding to the piezoelectric motor 102 (or a movable part thereof, such as motor shaft 112), 412, 416, 418, and virtual link 430. [0130] With reference to Figure 4A, the automatic recloser device too is configured so that in response to a force F applied by the piezoelectric motor 102 in first linear direction 114a, the mechanical linkage 410 moves, in the manner described above with reference to Figure 4C, and the movement of the mechanical linkage 410 causes a corresponding rotation of the first rigid member 106 in the first rotational direction 116a. The first rigid member 106 is configured to engage with the first knob 502. Thus, in this example, the rotation of the first rigid member 106 in the first rotational direction 116a causes the first knob 502 to rotate in the first rotational direction 116a, thereby closing the switch. At this point the automatic recloser device too has transitioned into a state corresponding to the configuration depicted in Figure 4B, i.e., state i . [0131] Starting from the configuration depicted in Figure 4B, in order to return the state of the automatic recloser device too to the configuration depicted in Figure 4A (i.e., transition from state d, back to state Ao), the piezoelectric motor 102 maybe activated to apply a force F in the second linear direction 114b. Since the piezoelectric motor 102 is pivotably coupled to the linkage 410, optionally through a motor shaft 112, a transverse rigid member 302, and/or an engagement pin 440, the application of the force F causes the linkage 410 to move in an analogous way to that described in detail with reference to Figure 4C above. The movement of the linkage 410 causes the first rigid member 106 to rotate in the second rotational direction 116b without engaging with the first knob 502. At this point, the automatic recloser device too transitions back to the configuration depicted in Figure 4A i.e., state A_o.

[0132] The automatic recloser device too may optionally further comprise a control module 214, as discussed above. The device too may additionally or alternatively further comprise a second knob 108 (not shown). In other examples, there maybe no second knob and the first rigid member 106 maybe configured to engage the first knob in any other suitable manner.

[0133] Figure 4F illustrates a side view of the example automatic recloser device too. With reference to Figure 4F, the mechanical linkage 410 may be designed to be compact. The width maybe reduced as compared to existing devices. In some specific examples, the mechanical linkage 410 may require as little as 5mm, optionally 4mm in the width direction. Together with the piezoelectric motor 102, as well as other possible components, such as a control module 214, an example automatic recloser device too may be designed with a width of 40mm, optionally 35mm or less. With reference to Figure 5B, note that the length and height of the automatic recloser device too may generally match that of the residual current device 500, which can facilitate retrofitting of the device too to RCDs. A compact device too may therefore be provided. [0134] The linkage 410 provides a mechanical advantage, thereby increasing the force applied to the first knob as compared to the force output by the piezoelectric motor 102. Figure 4G shows an example modelled torque exerted on the first rigid member 106 as a function of the angle of rotation for an example automatic recloser device too as depicted in Figure 4A. It will be understood that the mechanical linkage of an automatic recloser device too may be designed to generate the required torque necessary to facilitate an auto-close function for the device too. As such, a compact, rapid and reliable automatic recloser device too can be provided.

[0135] The mechanical advantage gained in using the design of the mechanical linkage 410, as depicted in Figure 4C, is the same in transitioning from state A_o to A as in transitioning from state A to A_o. Thus, the example automatic recloser device too of Figures 4A and 4B may operate with the same speed in returning to the state A_o as in reclosing the switch.

[0136] The skilled person will appreciate that the linkage mechanism 410 depicted schematically in Figure 4A-C can allow for design flexibility. For example, the number of rigid members, the lengths of each of the rigid members, and/or the position of the fixed pivot points may each be tuned to satisfy desired design requirements and/or design limitations.

[0137] It should be appreciated that the foregoing embodiments are not to be construed as limiting and that other variations, modifications and equivalents will be evident to those skilled in the art and are intended to be encompassed by the claims unless expressly excluded by the claim language.

[0138] Moreover, the disclosure of the present application should be understood to include any novel features or any novel combination of features either explicitly or implicitly disclosed herein or in any generalisation thereof. Claims may be formulated to cover any such features and/ or combination of such features derived therefrom.

Claims

1. An automatic recloser device (too) for use with a residual current device (500), the residual current device (500) comprising a switch which can be opened or closed by rotation of a first knob (502) of the residual current device (500), the automatic recloser device (too) comprising a housing (110) at least partially enclosing: a piezoelectric motor (102); and a mechanical linkage (104) arranged between the piezoelectric motor (102) and the first knob (502), the mechanical linkage (104) coupled to the piezoelectric motor (102) and comprising a first rigid member (106) configured to engage with the first knob (502); wherein the piezoelectric motor (102) is configured to apply a force in a first linear direction (114a, 114b) to move the mechanical linkage (104); and wherein the movement of the mechanical linkage (104) causes a rotation of the first knob (502) in a first rotational direction (116a), thereby closing the switch.

2. The device of claim 1, wherein the first rigid member (106) comprises a second knob (108) that protrudes from the housing (110) to engage with the first knob (502), wherein the second knob (108) is configured such that: when the piezoelectric motor (102) applies the force in the first linear direction (114a), the second knob (108) rotates in the first rotational direction (116a) and engages with the first knob (502) to cause the rotation of the first knob (502) in the first rotational direction (116a), and when the piezoelectric motor (102) applies a force in a second linear direction (114b, 114a) opposite the first linear direction (114a), the second knob (108) rotates in a second rotational direction (116b) opposite the first rotational direction (116a) and does not engage with the first knob (502).

3. The device of claim 2, wherein the first knob (502) can be manually actuated in the second rotational direction (116b) by a user, thereby opening the switch.

4. The device of claim 2 or claim 3, wherein the first knob (502) can be manually actuated in the first rotational direction (116a) by the user, thereby closing the switch, wherein the manual actuation is independent of rotation of the second knob (108).

5. The device of any of the preceding claims, wherein the piezoelectric motor (102) comprises a motor shaft (112), and wherein the piezoelectric motor (102) is configured to apply the force to move the mechanical linkage (104) via the movement of the motor shaft (112).

6. The device of any of the preceding claims, wherein the mechanical linkage (104) comprises a lever mechanism.

7. The device of claim 6, wherein the mechanical linkage (104) comprises a scotch yoke mechanism comprising: a sliding yoke (204), a slot (206), and a pin (210) configured to engage with the slot (206), wherein one of the first rigid member (106) or the sliding yoke (204) comprises the pin (210), and wherein the other of the first rigid member (106) or the sliding yoke (204) comprises the slot.

8. The device of claim 7, wherein the sliding yoke (204) is rigidly coupled to the piezoelectric motor (102), and wherein the pin (210) is configured to engage with the slot (206) of the sliding yoke (204) to rotate the first rigid member (106) in response to the linear movement of the sliding yoke (204).

9. The device of claim 6, wherein the mechanical linkage (104, 310) has a first end and a second end and comprises a plurality of rigid members (106, 312, 316, 318, 412416, 418) extending between the first end and the second end, wherein the first rigid member (106) is arranged at the second end and wherein the plurality of rigid members (106, 312, 316, 318, 412416, 418) are pivotably coupled to one another in sequence.

10. The device of claim 9, wherein a transverse rigid member (302) is arranged between and coupled to the mechanical linkage (104, 310) and the piezoelectric motor (102), the transverse rigid member (302) arranged to offset the mechanical linkage (104) from the piezoelectric motor (102) in a direction perpendicular to the first linear direction (114a).

11. The device of claim 9 or claim 10, wherein the piezoelectric motor (102) is pivotably coupled to the first end of the mechanical linkage (104, 310) so as to form a slider-crank four bar linkage, wherein the mechanical linkage (104, 310) forms a Grashof s four bar linkage at the second end, and wherein the first rigid member (106) is configured to rotate in response to the force from the piezoelectric motor (102) using the Grashof s four bar linkage.

12. The device of claim 9 or claim 10, wherein the mechanical linkage (104, 410) forms a five bar linkage, wherein the piezoelectric motor (102) is pivotably coupled to the first end of the mechanical linkage (104, 410), and wherein the first rigid member (106) is configured to rotate in response to the force from the piezoelectric motor (102) using the five bar linkage.

13. The device of claim 12, wherein the first end of the mechanical linkage (104, 410) comprises a slot (414), and wherein an engagement pin (440) coupled to the piezoelectric motor (102) is configured to pivotably and slidably engage with the slot (414) to drive the five bar linkage.

14. The device of any preceding claim, further comprising a resilient member (202), wherein the resilient member (202) is coupled at one end to the mechanical linkage and fixedly coupled at the other end to the housing (110), wherein the resilient member (202) is configured to bias the mechanical linkage so as to bias the rotation of the first knob in the first rotational direction.

15. A method of using the device of any one of the claims 1-14, comprising: activating the piezoelectric motor (102) to apply the force in the first linear direction (114a), thereby causing the mechanical linkage (104) to move; and rotating the first knob (502) in the first rotational direction (116a) in response to the movement of the mechanical linkage (104), thereby closing the switch.

16. A system (600) comprising: a residual current device (500) with a switch, wherein the switch can be opened or closed by rotation of a first knob (502) of the residual current device (500); and an automatic recloser device (too) of any one of the claims 1-14.