AU2014229871B2

AU2014229871B2 - Magnetothermal actuator

Info

Publication number: AU2014229871B2
Application number: AU2014229871A
Authority: AU
Inventors: Guillaume LACOMBE; Dominique Werner
Original assignee: Hager Electro SAS
Current assignee: Hager Electro SAS
Priority date: 2013-03-12
Filing date: 2014-03-07
Publication date: 2017-09-07
Anticipated expiration: 2034-03-07
Also published as: WO2014140461A1; CN105453213B; AU2014229871A1; FR3003394A1; FR3003394B1; EP2973635A1; CN105453213A; EP2973635B1

Abstract

A magnetothermal actuator comprising: - a magnetic actuator consisting of a coil (5) placed in series in an electric line, surrounding a fixed core (1) and a mobile core (4) and driving the mobile core (4) between two positions representing two states of the actuator, inactive and active states respectively, said mobile core (4) being returned to the position corresponding to the inactive state of the actuator by means of first return means (3); - a thermal actuator comprising a deformable component (10) made from a thermosensitive material capable of changing from an initial shape to an end shape representing two states of the actuator, inactive and active states respectively, under the effect of heat generated around same; the magnetic actuator and the thermal actuator being collinear along an axis of revolution (X). The magnetothermal actuator is characterised in that the thermal actuator comprises a heating part (11) made from a thermally conductive material placed in series with said coil (5), said heating part (11) cooperating thermally with said deformable component (10), being capable of generating heat around the latter.

Description

2

Magnetothermal actuator

This invention relates to a magnetothermal actuator in general, more particularly intended for an electrical device notably of the circuit breaker type, and designed to ensure protection by opening at least one electric line in the event of a fault causing a rise, either rapid, of the current, for example further to a short-circuit, or slow in the event of an overcharge in the circuit. The invention also relates to the electrical devices that are equipped with such a magnetothermal actuator.

The opening of a line in the event of the appearance of a malfunction such as mentioned above results from the existence in such devices of a fixed contact and a mobile contact capable of being separated - in this hypothesis - by the action of the magnetothermal actuator on a mechanical triggering lock. These two contacts are arranged between two connection terminals, which allow the device to be inserted in series in the line concerned.

The two types of malfunction are dealt with respectively by a magnetic part and a thermal part of the actuator, whose reaction times are very different and correspond in practise to the fault that appears on the Sine. A sudden and significant rise of the current, which generally stems from a short circuit on the line to be protected, must therefore give rise to a rapid opening of the contacts in order to avoid damaging the devices connected to the circuit. An overcharge, reflecting a demand for current on the line corresponding to too high a charge, mobilises the thermal triggering system instead. The latter often takes the form of a bimetal strip, which deforms under the action of the excessive heating resulting from the current overcharge, and makes a mechanical lock trigger, causing the contacts to open.

Magnetic triggering is generally provided by a coil connected in series in the circuit, and which cooperates with a magnetic circuit with a fixed yoke and a mobile part channelling the magnetic field produced by the coil, the mobile unit playing the role, directly or via a striker, of a component triggering the mechanical lock. 3

As a replacement for a thermal bimetal strip, it has been proposed, notably in document EP 0353816, to insert in such magnetothermal actuators a system based on the existence of a deformable component made from a thermosensitive material cooperating thermally with the coil, which has no effect on the magnetothermal actuator when the temperature of said component is below a certain threshold.

This component consists of a spring made from a shape memory alloy. By definition, a shape memory alloy can undergo an apparently plastic deformation of a few percent in a certain temperature range and fully recover its initial / original shape through reheating: this is the shape memory effect.

This shape memory spring can slacken to return to its original shape when its inner temperature exceeds a threshold thanks to the heat generated by the coil, and is capable of deforming again under the action of a compression force when its inner temperature drops back below said threshold.

The coil, through which the electric current passes, consequently finds its inner temperature increasing and radiating heat around itself during a slow current overcharge. It therefore indirectly heats the deformable component. It thus plays an essential role both for magnetic triggering and thermal triggering of the actuator.

The disadvantage in connection with this type of configuration resides in the high temperature lag of the coil. In fact the latter takes time to heat and the deformable component therefore takes time to return to its original shape, thereupon resulting in a late triggering of the thermal actuator compared with the desired triggering performance according to the thermal protection curve. Furthermore, due to the proximity of the elements constituting the magnetic actuator and the thermal actuator, the coil not only heats the deformable component but also the magnetic subassembly present in its vicinity. The heating space is much too large, and the efficiency of the operation is consequently low.

In the same way, the coil takes time to cool and the deformable component therefore takes time to cool and to return to its compressed position, thereupon 2014229871 18 Aug 2017 4 preventing any resetting of the product in good time.

To this cooling temperature lag is added the hysteresis effect of the shape memory spring, which takes slightly longer to return to its compressed position than to reach its original deployed position. 5 Finally, for the coil to be able to generate sufficient heat around itself to the abovementioned effect, the dimensioning of the coil must be materialised accordingly, that is to say, the number of turns making it up must be greater compared with an actuator traditionally assigned to the simple magnetic function; as for the section of the turns, this is imposed, therefore not variable. The coil dimensioned in this way is on one hand relatively voluminous in io a device desired to be compact, and on the other, creates an increased need for material constituting the coil compared with a traditional product.

Object of the invention

It is an object of the invention to overcome or at least ameliorate one or more of the above disadvantages, or at least to provide a useful alternative. is Summary

The present invention provides a magnetothermal actuator comprising: a magnetic actuator consisting of a coil placed in series in an electric line, surrounding a fixed core and a mobile core and driving the mobile core between two positions representing two states of the actuator, inactive and active states 20 respectively, said mobile core being returned to the position corresponding to the inactive state of the actuator by means of first return means; a thermal actuator comprising a deformable component made from a thermosensitive material capable of changing from an initial shape to an end shape representing two states of the actuator, inactive and active states 25 respectively, under the effect of heat generated around same; the magnetic actuator and the thermal actuator being colinear along an axis of rotation, wherein the thermal actuator comprises a heating part made from a thermally conductive material placed in series with said coil, said heating part cooperating thermally with the so deformable component, being capable of generating heat around the latter; further wherein the heating part consists of a part having a flat shape, of the washer type, 2014229871 18 Aug 2017 5 centred in relation to the axis of rotation, extending radially inside the actuator and offering a heat transmission surface having a central part in direct contact with the deformable component.

The magnetothermal actuator of a preferred embodiment proposes a solution in which the thermal function, although relying on the same principle based on a deformable component 5 made from a thermosensitive material, allows a noticeable improvement of the triggering and resetting performance of the thermal actuator.

To that effect, the magnetothermal actuator consists of a coil placed in series in an electric line, surrounding a fixed core and a mobile core and driving the mobile core between two positions representing two states of the actuator, inactive and active states respectively. This io mobile core is returned to the position corresponding to the inactive state of the actuator by means of first return means. It furthermore consists of a thermal actuator comprising a deformable component made from a thermosensitive material capable of changing from an initial shape to an end shape representing two states of the actuator, inactive and active states respectively, under the effect of heat generated around same. Finally, the configuration is such is that the magnetic actuator and the thermal actuator are colinear along an axis of rotation/revolution (X).

In fact, the magnetothermal actuator of the preferred embodiment is characterised principally in that it comprises a heating part made from a thermally conductive material placed in series with said coil, said heating part cooperating thermally with the deformable component, 20 being capable of generating heat around the latter.

It is therefore no longer the coil that heats the deformable component, but a heating part that fulfils this function. As for the coil, it is solely dedicated to the functioning of the magnetic subassembly of the actuator, which remains traditional.

The heating part is placed in series with the coil, therefore with the same electric current 25 passing through it. It therefore heats when short circuit currents pass through it, likewise in the event of overcharges.

The coil, relieved of its role of heating the thermal subassembly, can then be dimensioned normally for the magnetic subassembly it belongs to. Physically, the number of turns is reduced, effectively resulting in a reduction of its space requirement inside the actuator, and a financial 30 gain in terms of manufacturing.

According to a possible configuration, the heating part consists of a part having a flat shape, of the washer type, centred in relation to axis (X), extending radially inside the actuator and offering a heat transmission surface whose central part is in direct contact with the 2014229871 18 Aug 2017 6 deformable component.

The fact that direct contact exists between the heating part and the deformable component enables the latter to absorb the calories in a more efficient manner, by direct heat transmission. This type of direct heating enables the deformable component to heat up much more quickly 5 than if it had to draw its calories from the outside environment, in an indirect manner.

Furthermore, the shape of the heating part as a washer, therefore having a relatively slight thickness, and its alignment along axis (X) enables it to be easily integrated into the actuator with a reduced space requirement.

This heating part being solely designed in a thermally conductive material, such as steel, io brass or copper, it is easy to manufacture and its cost is low compared with that of an oversized coil such as described in the prior art.

Advantageously, the thermal actuator comprises means of distributing and concentrating the heat around the deformable component (10) so as to avoid the dispersal of calories inside the actuator, and therefore useless heating of the magnetic subassembly, is More precisely, said means of distributing and concentrating the heat around the deformable component consist of a sleeve of axis (X) made from a thermally conductive material surrounding the deformable component over its entire length, and comprising, at a first open extremity, a flange extending radially, whose outer surface is mounted on the heat transmission surface of the heating part. 20 This sleeve, whose flange is in direct contact with the heating part, therefore enables the creation of a "thermal cylinder", inside which the deformable component can rapidly heat and cool, according to the current passing through the heating part.

In the event of an overcharge on the line, the sleeve distributes the heat all around the deformable component, whereas the heating part acts via the portion of the deformable 25 component in contact with the central part of the heat transmission surface. The association of the sleeve and the heating part therefore enables optimum channelling of the calories and their correct guidance inside the actuator for efficient heating of the deformable component.

The temperature lag of the heating part and that of the sleeve are lower than that of the coil, given that these elements are distinctly less voluminous than the coil, and designed in 30 materials capable of rapidly keeping up with temperature variations.

Advantageously, the magnetothermal actuator according to the preferred embodiment includes first thermal insulation means between the magnetic actuator and the thermal actuator. These insulation means enable the prevention of any transmission of heat towards the magnetic 2014229871 18 Aug 2017 7 subassembly, so as not to damage the components in the long term, and to limit the volume of the area subjected to temperature variations inside the actuator. The smaller the volume, the lower the temperature lag and the more improved the efficiency of the process.

According to one possibility, said first thermal insulation means consist of a fillet of air s separating the magnetic actuator from the thermal actuator. In practice, this fillet of air separates said sleeve from the mobile core, the sleeve being partially inserted in a housing of the mobile core, the sleeve and the mobile core being colinear along axis (X).

According to the preferred embodiment, the deformable component consists of a shape memory spring of central axis (X) capable, when it returns by heating to its original deployed io shape, of driving a first striker, colinear to the mobile core, towards a position corresponding to the active state of the actuator, the memory shape spring and the first striker both being positioned inside said sleeve, an opening being provided in the wall of the second extremity of the sleeve in order to allow the first striker to pass, said first striker and the mobile core being capable of driving in translation a second striker towards a position corresponding to the active is state of the actuator. The memory shape spring and the first striker are returned to the position corresponding to the inactive state of the actuator by second return means located inside said sleeve. The shape memory spring therefore ends up in compressed position under the effect of the second return means.

Preferably, the magnetothermal actuator includes second thermal insulation means 20 between the coil and the thermal actuator, means which consist of a part, of a cylindrical shape, of axis (X) made from an insulating material of a plastic type, and separating the coil from all the other components of the magnetothermal actuator. The advantage of these second thermal Insulating means is to prevent the coil from heating the other components of the actuator. Since the line current passes through the coil, in fact, this latter also heats in the event of an 25 overcharge. As the coil henceforth no longer plays any part in thermal triggering, the heat it can generate must not influence thermal triggering. It is consequently preferable to insulate it against all the other components of the actuator.

More precisely, this insulating part includes a cylindrical casing around which the coil is wound, and inside which are positioned the fixed and mobile cores, the first return means, the so second striker, together with the part of the thermal actuator sleeve surrounding the first striker and the second return means. This casing therefore corresponds to a classic frame of a magnetic subassembly. A cap closes said casing at its extremity close to the heating part and separates the heating assembly, namely the heating part, the flange of the sleeve, the deformable 2014229871 18 Aug 2017 8 component and the part of the sleeve surrounding the deformable component, both from the coil and from the other components of the magnetic actuator, an opening being provided inside the cap to enable the part of the sleeve surrounding the first striker to pass.

Optionally, the temperature threshold for triggering the thermal actuator can be adjusted s by control means, which can, for example, act on the length of the housing in which are situated the second return means, so as to change the pretensioning they exert on the shape memory spring.

This preferred embodiment furthermore relates to an electrical line protection device of the circuit breaker type comprising a magnetothermal triggering system. io Brief description of the drawings

The invention will now be described in more detail with reference to the attached figures, for which: - Figure 1 is a diagrammatic sectional view of a magnetothermal actuator configuration according to the invention, wherein the component made from a thermosensitive is material is a shape memory spring; - Figure 2 is an exploded view of this magnetothermal actuator configuration.

In Figures 1 and 2, the magnetic actuator consists of a coil (5), a mobile core (4), a fixed core (1) and first return means comprising a spring (3). A striker (2), which will be called "second striker" in order to conform to the first part of the description, driven by mobile 20 core (4), enables action if necessary on the trigger of a mechanical lock. The functioning of the magnetic actuator is traditional: in the event of a significant rise of current, due for example to a short-circuit, the magnetic field produced by coil (5) causes mobile core (4) to move in opposition 9 to spring (3), driving striker (2). Said mobile core (4) moves in the direction of fixed core (1), which furthermore serves it as a stop during its translation movement. A casing (6a), around which coil (5) is wound, surrounds and guides mobile core (2)1, which slides therein.

The thermal actuator is located in the prolongation of the magnetic actuator, and is composed essentially of a heating part (11) carrying the current, a deformable component (10) made from a thermosensitive material capable of being heated by heating part (11), second return means in the shape of a second spring (8), another striker (9), which will be called “first striker” in order to conform to the first part of the description, and a sleeve (7) surrounding deformable component (10), second spring (8) and first striker (9). In the configuration of the invention, these elements present, for example, a circular symmetry around an axis (X), which is also the axis of coil (5) and/or that of the movement of second striker (2).

The deformable component consists of a shape memory spring (10), which when cold, that is to say at ambient temperature, is compressed by second return spring (8), and when hot, returns to its original shape by deploying itself axially in opposition to second return spring (8).

First striker (9) presents an extremity collar (15) on which shape memory 1 The mobile core is reference 4, the second striker is reference 2. Both items move inside the casing. I have not corrected this anomaly, as ! do not know what the author intended to say. 10 spring (10) on one side and return spring (8) on the other inner side are supported.

The general functioning is as follows: when the electric line experiences a slow rise of the current, further for example to an overcharge, the magnetic field produced by coil (5) is not sufficient to move mobile core (4} in opposition to spring means (3). On the other hand, heating part (11), heated directly by passing current, increases the temperature of shape memory spring (10). Return spring (8) is designed so that, beyond a certain temperature threshold, the pressure force exerted on the flange of first striker (9) by shape memory spring (10) is greater than the return force of spring (8).

Therefore, when the temperature in deformable component (10) reaches said temperature threshold, said component (10) deforms, that is to say, spring (10) slackens and returns to its original shape, and drives first striker (9) in the direction of arrow F, which in turn drives second striker (2) in this same direction, which actuates, in the hypothesis of an electrical device with a mechanical lock, a trigger that is part of said iock, causing the contacts to open.

There is therefore a mobile part of the thermal actuator, namely first striker (9) , whose movement, aiming to actuate the trigger, is no longer a matter of magnetic energy, but of mechanical energy from shape memory spring (10).

Heating part (11) is provided conductive, with high specific resistance, and is connected in series with coil (5). It is therefore heated by Joule effect, its temperature being proportional to the intensity of the current passing through it. It is manufactured in a material such as steel, brass or copper according to the calibre of the protection device in which the actuator is placed, it takes the shape of a washer, which extends radially inside the actuator and which presents a heat transmission surface oriented towards shape memory spring (10).

More precisely, the central part (14) of this heat transmission surface is mounted on and directly heats a first extremity of shape memory spring (10). When the latter deploys to return to its original shape, it comes to bear upon this central part (14) in order to push second striker (9)2 along direction (F). The 2 The second striker is reference 2. It is the first striker (9) that is pushed along direction (F). 11 peripheral part of this heat transmission surface is mounted on and directly heats an extremity flange (13) of sleeve (7), also developing radially inside the actuator. This fiange (13) comprises a large contact surface with heating part (11), enabling efficient transmission of the calorific energy from one to the other. This flange (13) then diffuses the heat through the cylindrical part of sleeve (7), which at the same time surrounds shape memory spring (10), first striker (9) and return spring (8). Sleeve (7) is in fact made from a material that conducts heat, such as aluminium, and forms a wrapper accommodating the different elements of the thermal actuator so as to distribute and concentrate the heat around shape memory spring (10).

The cylindrical part of sleeve (7), surrounding first striker (9) and return spring (8) is positioned in a receptacle of mobile core (4). First striker (9) moves along axis (X) in opposition to return spring (8) resting on a closed extremity (17) of sleeve (7) opposite that where flange (13) is situated. The free extremity (16) of first striker (9) opposite that including collar (15), successively passes through closed extremity (17) of sleeve (7), via an opening, and mobile core (4) in direction (F), until it strikes second striker (2) and causes thermal triggering. Second striker (2) is therefore activated, either by the movement of mobile core (4) for magnetic triggering, or by the movement of first striker (9) for thermal triggering.

So that the heat generated by the sleeve remains channelled at the thermal subassembly, and is insulated relative to the magnetic subassembly, a fillet of air (12) is provided between the cylindrical part of sleeve (7) and the inner wall of the receptacle of mobile core (4). The calories are therefore not dispersed throughout the actuator.

Furthermore, a part (6) made from insulating plastic is built into the actuator so as to insulate coil (5) from the other components of the actuator.

This part (6) consists of said cylindrical casing (6a), as described above, around which coil (5) is wound, and a cap (6b) closing casing (6a) at its extremity close to heating part (11). This cap (6b) therefore insulates the heating assembly

Direction F is not shown on the diagrams. ! have not corrected the error. 12 (namely heating part (11), flange (13) of sleeve (7), shape memory spring (10), the part of sleeve (7) surrounding shape memory spring (10)) from the components of the magnetic subassembly.

This thermomagnetic3 actuator therefore presents two levels of insulation, enabling the reactivity of the thermal subassembly to be optimised, and therefore its general temperature lag to be reduced.

As an option, the threshold temperature for triggering the thermal actuator can be adjusted by control means, which act, for example, on the length of the receptacle in which is situated return spring (8), delimited between closed extremity (17) of sleeve (7) and collar (15) of first striker (9). in order to vary this length, it is possible to place a second collar on striker (9), whose longitudinal position would be adjustable, and on which return spring (8) would be supported, first collar (15) henceforth only serving as a support for shape memory spring (10).

The longitudinal position of this second collar (15) enables return spring (8) to be compressed more or less so as to vary the pretensioning it exerts on shape memory spring (10) when the magnetothermal actuator is at rest.

Of course, the proposed configuration is not exhaustive of the invention, which equally encompasses all the variants, for example of shape and choice of materials, which stem directly from the proposed configuration. J This is a direct translation of the French, where the word has been changed from the usual “magnetotherm ique".

Claims

CLAIMS:

1. A magnetothermal actuator comprising: - a magnetic actuator consisting of a coil placed in series in an electric line, surrounding a fixed core and a mobile core and driving the mobile core between two positions representing two states of the actuator, inactive and active states respectively, said mobile core being returned to the position corresponding to the inactive state of the actuator by means of first return means; a thermal actuator comprising a deformable component made from a thermosensitive material capable of changing from an initial shape to an end shape representing two states of the actuator, inactive and active states respectively, under the effect of heat generated around same; the magnetic actuator and the thermal actuator being colinear along an axis of rotation, wherein the thermal actuator comprises a heating part made from a thermally conductive material placed in series with said coil, said heating part cooperating thermally with the deformable component, being capable of generating heat around the latter; further wherein the heating part consists of a part having a flat shape, of the washer type, centred in relation to the axis of rotation, extending radially inside the actuator and offering a heat transmission surface having a central part in direct contact with the deformable component.
2. The magnetothermal actuator according to claim 1, wherein the thermal actuator comprises means of distributing and concentrating heat around the deformable component.
3. The magnetothermal actuator according to claim 2, wherein said means of distributing and concentrating heat around the deformable component consists of a sleeve extending along the axis of rotation and made from a thermally conductive material surrounding the deformable component over its entire length, and comprising, at a first open extremity, a flange extending radially, whose outer surface is mounted on the heat transmission surface of the heating part.
4. The magnetothermal actuator according to claim 3, wherein the temperature lag of the heating part and that of the sleeve is lower than that of the coil.
5. The magnetothermal actuator according to any one of the preceding claims, further comprising first thermal insulation means located between the magnetic actuator and the thermal actuator.
6. The magnetothermal actuator according to claim 5, wherein said first thermal insulation means consists of a fillet of air separating the magnetic actuator from the thermal actuator.
7. The magnetothermal actuator according to claim 6, wherein said fillet of air separates said sleeve from the mobile core, the sleeve being partially inserted in a receptacle of the mobile core, the sleeve and the mobile core being co-linear along the axis of rotation.
8. The magnetothermal actuator according to any one of the preceding claims, wherein the deformable component consists of a shape memory spring extending along the axis of rotation, capable, when it returns by heating to its original deployed shape, of driving a first striker, colinear to the mobile core, towards a position corresponding to the active state of the actuator, the memory shape spring and the first striker both being positioned inside said sleeve, an opening being provided in the wall of a second extremity of the sleeve in order to allow the first striker to pass, said first striker and the mobile core being capable of driving in translation a second striker in opposition to the first return means towards a position corresponding to the active state of the actuator.
9. The magnetothermal actuator according to claim 8, wherein the memory shape spring and the first striker are returned to the position corresponding to the inactive state of the actuator by a second return means located inside said sleeve.
10. The magnetothermal actuator according to any one of the preceding claims, including a second thermal insulation means located between the coil and the thermal actuator.
11. The magnetothermal actuator according to the claim 10, wherein said second thermal insulation means consist of a part, of a cylindrical shape, extending along the axis of rotation and made from an insulating material of a plastic type, and separating the coil from all the other components of the magnetothermal actuator.
12. The magnetothermal actuator according to claim 11, wherein said insulating part includes: a cylindrical casing around which the coil is wound, and inside which are positioned the fixed core and the mobile core, first return means, second striker, together with the part of thermal actuator sleeve surrounding first striker and second return means; a cap closing said casing at its extremity close to heating part and separating the heating assembly, namely heating part, flange of sleeve, deformable component and the part of the sleeve surrounding deformable component, both from coil and from the other components of the magnetic actuator, an opening being provided inside the cap to enable the part of the sleeve surrounding first striker to pass.
13. An electrical line protection device, of a circuit breaker type, comprising a magnetothermal actuator according to any one of the preceding claims.