AU2012220430A1

AU2012220430A1 - Magnetothermal actuator

Info

Publication number: AU2012220430A1
Application number: AU2012220430A
Authority: AU
Inventors: Patrice Joyeux; Guillaume LACOMBE; Dominique Werner
Original assignee: Hager Electro SAS
Current assignee: Hager Electro SAS
Priority date: 2011-02-25
Filing date: 2012-02-21
Publication date: 2013-10-17
Anticipated expiration: 2032-02-21
Also published as: WO2012114037A1; EP2678877A1; AU2012220430B2; FR2972076B1; FR2972076A1; EP2678877B1; CN103493167A; CN103493167B

Abstract

The invention relates to a magnetothermal actuator, comprising: a magnetic actuator consisting of a coil (1) arranged in series in an electric line, surrounding a mobile core (2), and suitable for driving the latter between two positions constituting two states of the actuator, i.e. an operative state and an inoperative state, respectively; a first means (4) for returning the mobile core (2) to a position corresponding to the inoperative state of the actuator; and a thermal actuator consisting of a permanent magnet (10) magnetically engaging with a component (8) made of a heat-sensitive material having a low Curie temperature, with a view to maintaining the magnetothermal actuator in the inoperative state when the temperature of said component (8) is below the Curie temperature. Said actuator is characterised in that the component made of heat-sensitive material (8) is attached to a part (7, 15), the temperature of which increases if the current is raised, a second return means (9) being inserted between the permanent magnet (10) and said component (8), one of the latter being secured to a stationary portion and the other one being secured to a portion that is mobile relative to the coil (1) with a view to separating said permanent magnet and said component from one another when the temperature of the heat-sensitive component (8) exceeds the Curie temperature, said second return means (9) moving the permanent magnet and the component from a first relative position corresponding to the inoperative state of the actuator to a second relative position corresponding to the operative state thereof.

Description

1 Magnetothermal actuator The present invention relates to a magnetothermal actuator in general, more particularly designed for an electrical device, in particular of the circuit 5 breaker type, and designed to cut at least one electric line in case of defect causing either a rapid increase in the current, for example following a short circuit, or a slow increase in case of overloading the circuit. The invention also relates to electrical devices provided with such a magnetothermal actuator. 10 The opening of a line in the case of the appearance of a defect as mentioned above results from the existence, in such devices, of a stationary contact and a mobile contact that can be separated, in this scenario, by the action of the magnetothermal actuator on a mechanical activating lock. These two contacts are positioned between two connection terminals that 15 make it possible to insert the device serially in the concerned line. The two types of defect are respectively handled by a magnetic part and a thermal part of the actuator, the reaction times of which are very different and in practice correspond to the defect that appears on the line. Thus, a sudden and significant increase in the current, which generally 20 comes from a short circuit on the line to be protected, must cause rapid opening of the contacts to avoid damaging the devices connected to the circuit. An overload, reflecting a demand for current on the line corresponding to an excessive load, rather mobilizes the thermal activation system. The latter often takes the form of a bimetal strip that deforms under the action of 25 the excessive heating resulting from the current overload, and activates a mechanical lock causing opening of the contacts. The mechanical activation is generally done by a coil connected serially in the circuit, and which cooperates with a magnetic circuit with a stationary yoke and moving part channeling the magnetic field produced by 30 the coil, the moving member playing the role, directly or through a striker, of an element for activating the mechanical lock. To replace a thermal bimetal strip, it has been proposed to insert, into such magnetothermal actuators, a second magnetic system based on the existence of a permanent magnet magnetically cooperating with a 2 component made from a heat-sensitive material with a low Curie point, in order to keep the magnetothermal actuator in the inoperative state when the temperature of the component is below the Curie point. At ambient temperature, this component and the magnet are in fact 5 secured by the force exerted by the magnet. During a slow current overload, the temperature rises in the product, and in particular in the component made from the heat-sensitive material. If the temperature exceeds the Curie point of the material making up the component, the magnetic field exerted by the magnet no longer has an attractive effect on said component. It is then 10 possible to design a magnetic device in which an element moves and directly or indirectly actuates an activator of a lock, resulting in fine in separating the mobile contact from the stationary contact. Devices already exist based on this principle, like that which is disclosed in German patent DE 30 28 900. In that case, the magnetic 15 actuator is traditionally made up of a coil placed in series in the electric line, and surrounding a mobile core, the magnetic induction produced by the coil being able to drive said core between two positions embodying two states of the actuator, i.e., operative and inoperative states, respectively, return means for returning the mobile core to the position corresponding to the inoperative 20 state being provided. In the configuration disclosed in the German patent, the permanent magnet is in the axis of the mobile core, and separated therefrom by the heat-sensitive component with a low Curie point. When the Curie point is exceeded, the magnetic field exerted by the magnet no longer has an effect on the component in question, and said core is again free and can be 25 driven by the magnetic field produced by the coil. In such a design, the magnetic field generated by the coil is the origin of the movement of the mobile core, and consequently the mechanical lock making it possible to activate the circuit breaker mechanism. In this scenario, the force generated by the magnetic field due to the 30 coil must be sufficient to move the mobile coil during a simple current overload. It is therefore necessary for the coil to be sized accordingly, i.e., for the number of turns making it up to be increased relative to a traditional actuator allotted a simple magnetic function, which does not drive the mobile 3 core at these relatively low current values, but only when there is a significant increase in the current, for example following a short circuit. This configuration, which involves the same type of operation for both types of defects that the product is designed to detect, does not make it 5 possible to optimize the sizing of the actuator. To produce a sufficient force to overcome the attractive effect of the permanent magnet, it is necessary to oversize the coil by increasing the number of its turns, which creates an increased need for component material of the coil relative to traditional product. 10 This problem is resolved in the thermal actuator according to the invention, which proposes a solution in which the magnetic and thermal functions, although based on the same principle using a component made from heat-sensitive material with a low Curie point, make it possible to decorrelate the detection of the two types of defect. 15 To that end, the magnetothermal actuator according to the invention, traditionally including: - a magnetic actuator consisting of a coil arranged in series in an electric line, surrounding a mobile core, and suitable for driving the latter between two positions constituting two states of the actuator, 20 i.e., an operative state and an inoperative state, the first means for returning the mobile core to a position corresponding to the inoperative state of the actuator, and - a thermal actuator consisting of a permanent magnet magnetically engaging with a component made of a heat-sensitive material 25 having a low Curie temperature, so as to keep the magnetothermal actuator in the inoperative state when the temperature of said component is below the Curie temperature, is primarily characterized in that the component made of heat-sensitive material is attached to a part, the temperature of which increases if the 30 current is raised, a second return means being inserted between the permanent magnet and said component, one of the latter being secured to a stationary portion and the other one being secured to a portion that is mobile relative to the coil so as to separate said permanent magnet and said component from one another when the temperature of the heat-sensitive 4 component exceeds the Curie temperature, said second return means moving the permanent magnet and the component from a first relative position corresponding to the inoperative state of the actuator to a second relative position corresponding to the operative state thereof. 5 There is therefore a mobile part of the thermal actuator whereof the movement, aiming to actuate the activator, no longer uses magnetic energy, but mechanical energy coming from the second return means. According to the first possibility, said part of the thermal actuator whereof the temperature varies as a function of the intensity of the current is 10 heat-conducting, and positioned relative to the coil so as to be heated by the latter. Alternatively, this part may be provided to be conductive, with a high resistivity, and connected to the coil in series. It is then heated by Joule effect. In the first case, the part is assumed to communicate its heat to the 15 component made from heat-sensitive material so that the latter reaches its Curie point and must draw its heat from an element whereof the temperature necessarily increases in case of defect in the line: the coil, the composition and spatial configuration of which allow the transmission and collection of heat in a confined space, is put to use in that case. 20 Preferably, the actuator includes an actuating means that must be driven by the mobile core and the mobile part of the thermal actuator. According to a relatively traditional possibility in this type of device, said actuating means may be made up of a mobile striker that then strikes the activator of the mechanical lock, causing the contacts to open. 25 According to one possibility, the heat-sensitive component with a low Curie point may be made up of an alloy of iron and nickel. The striker may, according to one preferred configuration, be driven by the mobile core, which moves along the axis of the coil against a compression spring resting on a stationary core of the magnetic actuator 30 through which the striker passes, which next successively crosses the stationary part and the mobile part of the thermal actuator, between which a spring is interposed aiming to separate said parts, the striker including, near its free end, a bearing flange on the face of said distal mobile part of the mobile core.

5 In this case, the striker acts in a direction going from the magnetic actuator toward the thermal actuator. The inverse may also be implemented, with an alternative configuration as mentioned below. In this case, the striker is driven by the mobile part of the thermal 5 actuator, which moves under the effect of a spring interposed between the mobile and stationary parts of the thermal actuator along the axis of the coil against a compression spring resting on a stationary core of the magnetic actuator through which the striker passes after having passed through the mobile core, the striker then including a bearing flange on the radial wall of 10 the mobile core and proximal wall of the stationary core. In both of these scenarios, the stationary part of the thermal actuator may be made up of the conductive part connected to the coil, the heat sensitive component alongside said part and an enclosure made from an insulating material made up of a first sleeve guiding the translation of the 15 mobile part of the thermal actuator, secured to a second sleeve coaxial to the first, around which the coil is wound, and guiding the translation of the mobile core of the magnetic actuator. Still in these two possible scenarios, one alternative may consist of said stationary part being made up of the heat-sensitive components 20 alongside said conductive part and an enclosure made from a thermal conductive material made up of a first sleeve guiding the translation of the mobile part of the thermal actuator, secured to a second sleeve coaxial to the first, around which the coil is wound, and guiding the translation of the mobile core of the magnetic actuator. 25 These configurations eliminate the limitations of the prior art insofar as the thermal part is spatially separated from the magnetic actuator strictly speaking, resulting in the possibility of decorrelating the two functions. The mobile part may in turn be made up of the magnet secured to a paddle made from a ferromagnetic material, with a cylindrical shape capable 30 of guiding its movement in the first sleeve and forming a magnetic circuit with the heat-sensitive component, the latter and/or the conductive part being fixed to a radial wall separating the two coaxial sleeves. Alternatively, it may be made up of the magnet secured to a paddle made from a ferromagnetic material, with a cylindrical shape capable of 6 guiding its movement in the first sleeve and forming a magnetic circuit with the heat-sensitive component, the latter and/or the conductive part being fixed to a radial wall closing the first sleeve at its end opposite a radial wall separating the two coaxial sleeves. 5 As previously indicated, the invention does not relate only to the magnetothermal actuator, but also a magnetothermal activation system for an electrical device of the line protection circuit breaker type, including an actuator whereof the coil is placed in series in said line, characterized in that the actuating means is provided to activate a mechanical lock for opening the 10 line in case of overvoltage or short-circuit. It also relates to a line protection electrical device of the circuit breaker type including a magnetothermal activation system. The invention will now be described in more detail, in reference to the appended figures, in which: 15 - figure 1 is a diagrammatic cross-sectional view of a first magnetothermal actuator configuration according to the invention, in which the component made from a heat-sensitive material with a low Curie point is electrically connected to the coil - figure 2 shows a cross-sectional view of an alternative of figure 1 20 inverting the mobile and stationary parts of the thermal actuator; - figure 3 shows a cross-sectional view of a magnetothermal actuator according to the invention in which the component made from a heat-sensitive material with a low Curie point is heated by the coil; and 25 - figure 4 is a cross-sectional view of one alternative of the configuration of figure 3, reversing the mobile and stationary parts of the thermal actuator. The elements, components and parts shared by the different configurations covered by the figures bear the same references. Thus, in 30 figure 1, the magnetic actuator is made up of a coil (1), a mobile core (2), a stationary core (3) and first return means made up of a spring (4). A striker (5) driven by the mobile core (2) may if applicable act on an activator of a mechanical lock. The operation of the magnetic actuator is traditional: upon a significant increase in the current I, for example due to a short-circuit, the 7 magnetic field produced by the coil (1) causes the mobile core (2) to move against the spring (4), driving the striker (5). Said mobile core (2) moves in the direction of the stationary core (3), which also serves as an abutment during its translational movement. A sleeve (6) surrounds and guides the 5 mobile core (2), which slides therein. The thermal actuator is situated in the extension of the magnetic actuator, and is essentially made up of a part (7) traveled by the current I, the component (8) made from a heat-sensitive material with a low Curie point, second return means in the form of a second spring (9), a permanent magnet 10 (10) and a paddle forming a magnetic yoke (11) for the magnetic circuit of the permanent magnet (10). In the configuration according to the invention, these elements for example have a circular symmetry around an axis that is also the axis of the coil (1) and/or of movement of the striker (5). The latter, using central orifices, passes through all of the elements making up thermal 15 actuator. These elements are positioned in an enclosure (12) made from a material that does not have any particular thermomagnetic properties, for example plastic, and which is secured to and/or a single piece with the sleeve (6). The striker (5) also has a flange (13) cooperating with the paddle (11) that drives it in the direction of the arrow F when the thermal actuator is 20 activated. The operation is as follows: when the electric line undergoes a slow increase in the current for example occurring following an overload, the magnetic field produced by the coil is not sufficient to move the mobile core (2) against the spring means (4). However, the part (7), directly heated by 25 passage of the current in the configuration of figure 1, increases the temperature of the heat-sensitive component (8) toward which the paddle (11) is attracted due to the magnetic field generated by the permanent magnet (10). The second return means (9) are provided so that at ambient temperature, the magnetic force generated by the permanent magnet (10) is 30 greater than the return force of the spring (9). When the temperature reaches the Curie point in the heat-sensitive material (8), said component (8) becomes demagnetized, causing the magnetic circuit it forms with the paddle (11) to open, under the effect of the spring (9). The paddle moves in the direction of the arrow F, and drives the 8 striker (5), which, in the scenario of an electrical device with a mechanical lock, actuates an activator that is part of said lock. In figure 2, the part (7) heated by direct passage of the current I is no longer near the coil (1), but at the end of the distal thermal actuator of said 5 coil (1). In that case, when the component (8) reaches the Curie temperature, the spring (9) pushes the paddle (11) toward the coil (1), and it is therefore necessary for the striker (5) to go in that direction, with a movement in the direction of the arrow F'. The mobile core (2) must consequently move in the same direction, and be situated near the thermal actuator, contrary to the 10 configuration shown in figure 1. The flange (13) of the striker (5) is then situated in a recess (14) of the mobile core (2), so as to be driven by the mobile core (2) when the abrupt and significant increase of the current I generates a magnetic field in the coil capable of moving said mobile core (2) against the spring (4). 15 Figure 3 illustrates a configuration in which the conductive part (7) traveled by the current is eliminated. In that scenario, the heating of the coil (1) is indirect, and only the latter is traveled by the current 1. The sleeve (6') extended by a second sleeve (12') forming the enclosure housing the different elements of the thermal actuator is now formed from a material that 20 conveys heat, and it is primarily the thicker base (15) of said enclosure that heats the component (8) made from a heat-sensitive material with a low Curie point. As in the previous configurations, the contact surface between these elements, developing radially, constitutes the largest possible contact surface so as to transmit the heat energy from one to the other. With the 25 exception of the existence of the part (7) and the change of material for the sleeve/enclosure (6), the configuration and the operation of the alternative proposed in figure 3 are identical to those of the configuration of figure 1. These are the same modifications that differentiate between the configuration of figure 4 and that of figure 2: there is no longer a part (7), and 30 the enclosure (6', 12') is now made from a material chosen for its ability to convey heat. The configurations proposed in figures 1 to 4 are of course not exhaustive with respect to the invention, which also encompasses 9 alternatives, for example in terms of shape and choice of materials, which follow directly from the proposed configurations.

Claims

1. A magnetothermal actuator including: - a magnetic actuator consisting of a coil (1) arranged in series in an 5 electric line, surrounding a mobile core (2), and suitable for driving the latter between two positions constituting two states of the actuator, i.e., an operative state and an inoperative state, first means (4) for returning the mobile core (2) to a position corresponding to the inoperative state of the actuator, and 10 - a thermal actuator consisting of a permanent magnet (10) magnetically engaging with a component made of a heat-sensitive material (8) having a low Curie temperature, so as to keep the magnetothermal actuator in the inoperative state when the temperature of said component (8) is below the Curie temperature, 15 characterized in that the component (8) made of heat-sensitive material is attached to a part (7, 15), the temperature of which increases if the current is raised, a second return means (9) being inserted between the permanent magnet (10) and said component (8), one of the latter being secured to a stationary portion and the other one being secured to a 20 portion that is mobile relative to the coil (1) so as to separate said permanent magnet and said component from one another when the temperature of the heat-sensitive component (8) exceeds the Curie temperature, said second return means (9) moving the permanent magnet and the component from a first relative position corresponding to 25 the inoperative state of the actuator to a second relative position corresponding to the operative state thereof.

2. The magnetothermal actuator according to the preceding claim, characterized in that the part (15) of the thermal actuator is heat 30 conducting, and positioned relative to the coil (1) so as to be heated by the latter. 11

3. The magnetothermal actuator according to claim 1, characterized in that the part (7) of the thermal actuator is conductive, with a high resistivity, and connected to the coil (1) in series. 5

4. The magnetothermal actuator according to one of the preceding claims, characterized in that it includes an actuating means driven by the mobile core (2) and the mobile part of the thermal actuator.

5. The magnetothermal actuator according to any one of the preceding 10 claims, characterized in that the actuating means is made up of a striker (5).

6. The magnetothermal actuator according to one of the preceding claims, characterized in that the heat-sensitive component (8) with a low Curie 15 point is made up of an alloy of iron and nickel.

7. The magnetothermal actuator according to one of claims 5 and 6, characterized in that the striker (5) is driven by the mobile core (2), which moves along the axis of the coil (1) against a compression spring (4) 20 resting on a stationary core (3) of the magnetic actuator through which the striker (5) passes, which next successively crosses the stationary part and the mobile part of the thermal actuator, between which a spring (9) is interposed aiming to separate said parts, the striker (5) including, near its free end, a bearing flange (13) on the face of said distal mobile part of the 25 mobile core (2).

8. The magnetothermal actuator according to one of claims 5 and 6, characterized in that the striker (5) is driven by the mobile part of the thermal actuator, which moves under the effect of a spring (9) interposed 30 between the mobile and stationary parts of the thermal actuator along the axis of the coil (1) against a compression spring (4) resting on a stationary core (3) of the magnetic actuator through which the striker (5) passes after having passed through the mobile core (2), the striker (5) then 12 including a bearing flange (13) on the radial wall of the mobile core (2) and proximal wall of the stationary core (3).

9. The magnetothermal actuator according to one of claims 7 and 8, characterized in that the stationary part of the thermal actuator is made up 5 of the conductive part (7) connected to the coil (1), the heat-sensitive component (8) alongside said part (7) and an enclosure made from an insulating material made up of a first sleeve (12) guiding the translation of the mobile part of the thermal actuator, secured to a second sleeve (6) coaxial to the first, around which the coil (1) is wound, and guiding the 10 translation of the mobile core (2) of the magnetic actuator.

10.The magnetothermal actuator according to one of claims 7 and 8, characterized in that the stationary part of the thermal actuator is made up of the heat-sensitive component (8) alongside said conductive part (15) 15 and an enclosure made from a thermal conductive material made up of a first sleeve (12') guiding the translation of the mobile part of the thermal actuator, secured to a second sleeve (6') coaxial to the first, around which the coil (1) is wound, and guiding the translation of the mobile core (2) of the magnetic actuator. 20

11. The magnetothermal actuator according to one of claims 9 and 10, characterized in that the mobile part is made up of the magnet (10) secured to a paddle (11) made from a ferromagnetic material, with a cylindrical shape capable of guiding its movement in the first sleeve (12, 25 12') and forming a magnetic circuit with the heat-sensitive component (8), the latter and/or the conductive part (7) being fixed to a radial wall separating the two coaxial sleeves (12, 12'; 6, 6').

12.The magnetothermal actuator according to one of claims 9 and 10, 30 characterized in that the mobile part is made up of the magnet (10) secured to a paddle (11) made from a ferromagnetic material, with a cylindrical shape capable of guiding its movement in the first sleeve (12, 12') and forming a magnetic circuit with the heat-sensitive component (8), the latter and/or the conductive part (7) being fixed to a radial wall closing 13 the first sleeve (12, 12') at its end opposite a radial wall separating the two coaxial sleeves (12, 12'; 6, 6').

13.A magnetothermal activation system for an electrical device of the line protection circuit breaker type, including an actuator according to the 5 preceding claims whereof the coil (1) is placed in series in said line, characterized in that the actuating means is provided to activate a mechanical lock for opening the line in case of overvoltage or short circuit. 10

14.A line protection electrical device of the circuit breaker type including a magnetothermal activation system according to the preceding claim.