WO2014140461A1

WO2014140461A1 - Magnetothermal actuator

Info

Publication number: WO2014140461A1
Application number: PCT/FR2014/050526
Authority: WO
Inventors: Guillaume LACOMBE; Dominique Werner
Original assignee: Hager-Electro Sas
Priority date: 2013-03-12
Filing date: 2014-03-07
Publication date: 2014-09-18
Also published as: FR3003394B1; FR3003394A1; CN105453213B; AU2014229871B2; EP2973635B1; EP2973635A1; CN105453213A; AU2014229871A1

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

Magnetothermic actuator

The present invention relates to a magnetothermic actuator in general, more particularly intended for an electrical appliance, in particular of the circuit-breaker type, and designed to provide protection by opening at least one electric line in the event of a fault resulting in a rapid rise of the current , for example following a short circuit, or slow in case of overload in the circuit. The invention also relates to electrical apparatus which is provided with such a magnetothermal actuator.

The opening of a line in case of occurrence of a failure as mentioned above results from the existence, in such devices, of a fixed contact and a movable contact that can be separated - in this case. hypothesis - by the action of the magnetothermal actuator on a mechanical trigger lock. These two contacts are arranged between two connection terminals which allow to insert the device in series in the line concerned.

Both types of failure are respectively supported by a magnetic part and a thermal part of the actuator whose reaction times are very different and correspond in practice to the defect that appears on the line. Thus, a sharp and significant rise in current, which usually comes from a short circuit on the line to be protected, must cause a rapid opening of the contacts to avoid damaging the devices connected to the circuit. An overload, reflecting a current demand on the line corresponding to a load that is too high, rather mobilizes the thermal trip system. The latter often takes the form of a bimetallic strip that deforms under the action of excessive heating resulting from the current overload, and triggers a mechanical lock causing the opening of the contacts.

The magnetic tripping is generally ensured by a coil connected in series in the circuit, and which cooperates with a magnetic circuit with fixed yoke and moving part channeling the magnetic field produced by the coil, the movable member playing the role, directly or via a firing pin, trigger element of the mechanical lock.

In replacement of a thermal bimetallic strip, it has been proposed in particular in document EP 0353816 to insert in such magnetothermal actuators a system based on the existence of a deformable component made of heat-sensitive material cooperating thermally with the coil, which does not has no effect on the magnetothermal actuator when the temperature of said component is below a certain threshold.

This component consists of a spring composed of 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 by reheating: this is the shape memory effect.

This shape memory spring can relax to return to its original shape when its internal temperature exceeds a threshold due to the heat generated by the coil, and is able to deform again under the action of a compression force when its internal temperature falls below this threshold.

The coil, which is traversed by the electric current, therefore sees its internal temperature rise and emit heat around it during a slow current overload. It thus indirectly heats the deformable component. It plays an essential role for both the magnetic tripping and the thermal tripping of the actuator.

The disadvantage associated with this type of configuration lies in the large thermal inertia of the coil. Indeed, the latter takes time to heat, and the deformable component thus takes time to regain its original shape, resulting in a late release of the thermal actuator compared to the desired tripping performance according to the thermal protection curve. In addition, because of the proximity of the components of the magnetic actuator and the thermal actuator, the coil not only heats the deformable component, but also the subassembly magnetic present in its vicinity. The volume of heating is much too important, and the yield of the operation therefore low.

In the same way, the coil takes a long time to cool, and the deformable component thus takes time to cool down and return to its compressed position, thus preventing a resetting of the product in due time.

To this thermal cooling inertia is added the hysteresis effect of the shape memory spring which takes slightly longer to return to its compressed position than to come to its original deployed position.

Finally, so that the coil can generate enough heat around it to the aforementioned effect, the dimensioning of the coil must be carried out accordingly, that is to say that the number of turns that constitutes it must be increased compared to an actuator traditionally devolved to the simple magnetic function, the section of turns being imposed, so invariable. The thus dimensioned coil is on the one hand relatively bulky, in an apparatus that is desired compact, and on the other hand generates an increased need for material constituting the coil compared to a traditional product.

These problems are solved in the magnetothermic actuator of the invention, which proposes a solution in which the thermal function, although based on the same principle based on a deformable component of heat-sensitive material, makes it possible to substantially improve the performance of triggering and resetting the thermal actuator.

For this purpose, the magnetothermal actuator of the invention conventionally comprises a magnetic actuator consisting of a coil placed in series in an electrical line, surrounding a fixed core and a movable core and driving the movable core between two positions respectively embodying two states. inactive and active actuator. This mobile core is recalled in position corresponding to the inactive state of the actuator by means of first return means. It furthermore comprises a thermal actuator comprising a deformable component made of thermosensitive material able to pass from a shape initial to a final form materializing two states respectively inactive and active actuator under the effect of heat generated around him. Finally, the configuration is such that the magnetic actuator and the thermal actuator are collinear along an axis of revolution (X).

In fact, the magnetothermal actuator of the invention is characterized principally in that it comprises a heating element made of thermally conductive material placed in series with said coil, said heating element cooperating thermally with the deformable component being able to generate heat around him.

It is no longer the coil that heats the deformable component, but a heating element that fulfills this function. The coil itself is dedicated solely to the operation of the magnetic subassembly of the actuator, which remains traditional.

The heating element is placed in series with the coil, thus crossed by the same electric current. It heats up when it is covered by short circuit currents, as well as overloads.

The coil, discharged from its role of heating the thermal subassembly, can then be dimensioned normally for the magnetic subassembly to which it belongs. Specifically, the number of turns is reduced, resulting in a decrease in its size within the actuator, and an economic gain in terms of manufacturing.

According to one possible configuration, the heating part consists of a plane-like part, of the washer type, centered with respect to the axis (X), extending radially within the actuator and offering a transmission surface of heat whose central portion is directly in contact with the deformable component.

The fact that there is a direct contact between the heating element and the deformable component allows the latter to absorb the calories more efficiently, by direct heat transmission. This type of direct heating allows the deformable component to heat much faster than if it were to draw its calories in the external environment, indirectly.

Furthermore, the shape of the washer-shaped heating element, therefore of relatively small thickness, and its alignment on the axis (X), makes it possible to integrate it easily within the actuator with a small space requirement.

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

Advantageously, the thermal actuator comprises means of distribution and concentration of heat around the deformable component (10) so as to avoid the dispersion of calories within the actuator, and therefore the unnecessary heating of the magnetic subassembly .

More precisely, said means for distributing and concentrating heat around the deformable component consist of an axis sleeve (X) of thermally conductive material surrounding the deformable component over its entire length, and comprising, at a first open end, a radially extending flange whose outer surface is contiguous to the heat transfer surface of the heating element.

This sleeve, whose collar is in direct contact with the heating part, thus creates a "thermal cylinder" within which the deformable component can quickly heat and cool, depending on the current flowing through the heating part.

During an overload on the line, the sleeve distributes the heat all around the deformable component, while the heating element acts via the portion of the deformable component in contact with the central portion of the heat transmission surface. The combination of the sleeve and the heating part thus optimally channels the calories, and guides them correctly within the actuator, for efficient heating of the deformable component. The thermal inertia of the heating element and that of the sleeve are lower than that of the coil, since these elements are much less bulky than the coil, and designed in materials able to quickly follow temperature variations.

Advantageously, the magnetothermal actuator according to the invention comprises first thermal insulation means between the magnetic actuator and the thermal actuator. These isolation means make it possible to prevent any heat transmission to the magnetic subassembly, so as not to damage the components in the long term, and to limit the volume of the zone undergoing thermal variations within the actuator. . The smaller the volume, the lower the thermal inertia and the improved process efficiency.

According to one possibility, said first thermal insulation means consist of an air gap separating the magnetic actuator from the thermal actuator. This air gap in practice separates said sleeve from the movable core, the sleeve being partly inserted into a housing of the movable core, the sleeve and the movable core being collinear with axis (X).

According to the invention, the deformable component consists of a central axis shape memory spring (X) capable of driving, when it regains its original deployed form by heating, a first collinear striker with the movable core, towards a corresponding position. in the active state of the actuator, the shape memory spring and the first striker being both positioned inside said sleeve, an orifice being provided in the wall of the second end of the sleeve to pass the first striker , said first striker and the movable core being able to drive in translation a second striker to a position corresponding to the active state of the actuator. The shape memory spring and the first striker are returned to the position corresponding to the inactive state of the actuator by means of second return means located inside said sleeve. The shape memory spring is thus found in a compressed position under the effect of the second return means. Preferably, the magnetothermal actuator of the invention comprises second heat-insulating means between the coil and the thermal actuator which consist of a piece of cylindrical shape with axis (X) made of insulating material of the plastic type, and separating the coil from all other components of the magnetothermal actuator. The advantage of these second thermal insulation means is to prevent the coil from heating the other components of the actuator. Since the current of the line passes through the coil, it also heats up in case of overload. Since the coil no longer plays any role in thermal tripping, the heat it can generate must not influence the thermal tripping. Therefore, it is best to isolate it from all other components of the actuator.

More specifically, this insulating piece comprises a cylindrical jacket around which is wound the coil and inside which are positioned the fixed and movable cores, the first return means, the second striker, and the part of the sleeve of the thermal actuator surrounding the first striker and the second return means. This shirt thus corresponds to a conventional framework of a magnetic subassembly. A plug closes said jacket at its proximal end of the heating element and separates the heating assembly, namely the heating element, the collar of the sleeve, the deformable component and the portion of the sleeve surrounding the deformable component, at the of the coil and other components of the magnetic actuator, an orifice being provided in the plug to allow the portion of the sleeve surrounding the first striker to pass.

Optionally, the trigger temperature threshold of the thermal actuator may be adjusted by adjustment means which may for example act on the length of the housing in which the second return means are located, so as to modify the prestressing they exert on the shape memory spring. The present invention also relates to a circuit breaker type electrical protection device comprising a magnetothermic tripping system.

The invention will now be described in more detail, with reference to the appended figures, for which:

- Figure 1 is a schematic sectional view of a magnetothermal actuator configuration according to the invention, wherein the component of heat-sensitive material is a shape memory spring;

FIG. 2 is an exploded view of this magnetothermic actuator configuration.

In FIGS. 1 and 2, the magnetic actuator consists of a coil (5), a movable core (4), a fixed core (1) and first return means constituted by a spring ( 3). A striker (2), which will be called "second striker" to comply with the first part of the description, driven by the movable core (4), allows if necessary to act on a trigger of a mechanical lock . The operation of the magnetic actuator is traditional: during a significant increase in current, due for example to a short-circuit, the magnetic field produced by the coil (5) causes the displacement of the mobile core (4) against the spring (3), driving the striker (2). Said movable core (4) moves in the direction of the fixed core (1) which also serves as a stop during its translational movement. A jacket (6a) around which is wound the coil (5) surrounds and guides the movable core (2) which slides therein.

The thermal actuator is located in the extension of the magnetic actuator, and is essentially composed of a heating part (1 1) traversed by the current, a deformable component (10) heat-sensitive material capable of being heated by the heating part (1 1), second return means in the form of a second spring (8), another striker (9), which will be called "first striker" to comply with the first one part of the description, and a sleeve (7) surrounding the deformable component (10), the second spring (8) and the first striker (9). In the configuration of the invention, these elements have for example a circular symmetry around an axis (X) which is also the axis of the coil (5) and / or displacement of the second striker (2).

The deformable component consists of a shape memory spring (10), which, when cold, ie at ambient temperature, is compressed by the second return spring (8), and, when it is hot, returns to its original shape by deploying axially against the second spring (8) of return.

The first striker (9) has an end shoulder (15) on which rest the shape memory spring (10) on one side and the spring (8) of return on the other inner face.

The general operation is as follows: when the power line undergoes a slow rise of the current, for example following an overload, the magnetic field produced by the coil (5) is not sufficient to move the mobile core (4) to meet spring means (3). On the other hand, the heating element (1 1), directly heated by passage of the current, increases the temperature of the shape memory spring (10). The return spring (8) is provided so that beyond a certain temperature threshold, the pressure force exerted on the flange of the first striker (9) by the shape memory spring (10) is greater than the return force of the spring (8).

Thus, when the temperature in the deformable component (10) reaches said temperature threshold, said component (10) deforms, that is to say that the spring (10) relaxes and returns to its original shape, and causes the first striker (9) in the direction of arrow F which in turn drives the second striker (2) in the same direction, which actuates, in the event of an electrical apparatus with mechanical lock, a trigger forming part of said lock, causing the opening of the contacts.

There is therefore a moving part of the thermal actuator, namely the first striker (9), the movement of which, to actuate the trigger, does not fall within more than one magnetic energy but a mechanical energy from the shape memory spring (10).

The heating part (1 1) is conductive, high resistivity, and is connected in series with the coil (5). It is heated by the Joule effect, its temperature being proportional to the intensity of the current passing through it. It is made of a material of the steel, brass, or copper type depending on the gauge of the protective device in which the actuator is placed. It takes the form of a washer which extends radially within the actuator, and which has a heat transmission surface facing the shape memory spring (10).

More specifically, the central portion (14) of this heat transmission surface is contiguous to and directly heats a first end of the shape memory spring (10). When the latter unfolds to regain its original shape, it is supported on this central portion (14) to push the second striker (9) in the direction (F). The peripheral portion of this heat transmission surface is contiguous to and directly heats an end flange (13) of the sleeve (7) also developing radially within the actuator. This flange (13) constitutes a large contact area with the heating part (1 1) for efficient transmission of the heat energy from one to the other. This collar (13) then diffuses heat through the cylindrical portion of the sleeve (7) which surrounds both the shape memory spring (10), the first striker (9), and the return spring (8). The sleeve (7) is in fact made of a material that carries heat, of the aluminum type, and forms an envelope housing the various elements of the thermal actuator so as to distribute and to concentrate the heat around the shape memory spring. (10).

The cylindrical portion of the sleeve (7), surrounding the first striker (9) and the return spring (8), is positioned in a housing of the movable core (4). The first striker (9) moves along the axis (X) against the return spring (8) resting on a closed end (17) of the sleeve (7) opposite to the one where the collar (13) is. The free end (16) of the first striker

(9), opposite to that comprising the shoulder (15), passes successively through the closed end (17) of the sleeve (7) via an orifice and the movable core (4) in the direction (F), until striking the second striker (2) and cause a thermal trip. The second striker (2) is activated either by moving the movable core (4) for a magnetic trigger, or by moving the first striker (9) for a thermal trip.

So that the heat generated by the sleeve remains channeled at the thermal subassembly and is insulated from the magnetic subassembly, an air gap (12) is provided between the cylindrical portion of the sleeve (7) and the wall interior of the mobile core housing (4). Thus, the calories are not dissipated throughout the actuator.

In addition, a piece (6) of insulating plastic is integrated in the actuator so as to isolate the coil (5) from the other components of the actuator. This piece (6) consists of said cylindrical jacket (6a), as described above, around which is wound the coil (5), and a plug (6b) closing the jacket (6a) at its end proximal to the heating element (1 1). This plug (6b) thus isolates the heating assembly (namely the heating part (1 1), the flange (13) of the sleeve (7), the shape memory spring (10), the part of the sleeve (7). ) surrounding the shape memory spring

(10)) components of the magnetic subassembly.

This thermomagnetic actuator thus has two levels of insulation, to optimize the reactivity of the thermal subassembly, and thus reduce its general thermal inertia.

Optionally, the trigger temperature threshold of the thermal actuator can be adjusted by adjustment means which act for example over the length of the housing in which the return spring (8), delimited between the closed end (17), is located. ) of the sleeve (7) and the shoulder (15) of the first striker (9). To vary this length, it is possible to have a second shoulder on the striker (9) whose longitudinal position would be adjustable, and on which rest the return spring (8), the first shoulder (15) no longer serving than in support of the shape memory spring (10).

The longitudinal position of this second shoulder (15) makes it possible to compress more or less the return spring (8) so as to vary the prestressing it exerts on the shape memory spring (10) when the magnetothermal actuator is resting.

The proposed configuration is of course not exhaustive of the invention, which also encompasses all variants, for example shape and choice of materials, which immediately follow from the proposed configuration.

Claims

1. Magnetothermic actuator comprising:

- A magnetic actuator consisting of a coil (5) placed in series in an electrical line, surrounding a fixed core (1) and a movable core (4) and driving the movable core (4) between two positions embodying two states respectively inactive and active actuator, said movable core (4) being biased in 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 of thermosensitive material capable of passing from an initial form to a final form embodying two respectively inactive and active states of the actuator under the effect of a heat generated around it;

the magnetic actuator and the thermal actuator being collinear along an axis of revolution (X),

characterized in that the thermal actuator comprises a heating element (1 1) made of thermally conductive material placed in series with said coil (5), said heating element (1 1) cooperating thermally with the deformable component (10) while being suitable to generate heat around him.

2. Magnetothermic actuator according to the preceding claim, characterized in that the heating element (1 1) consists of a flat-shaped part of the washer type, centered with respect to the axis (X), extending radially to in the actuator and providing a heat transmission surface whose central portion (14) is directly in contact with the deformable component (10).

Magnetothermic actuator according to one of the preceding claims, characterized in that the thermal actuator comprises heat distribution and concentration means around the deformable component (10).

4. Magnetothermic actuator according to the preceding claim, characterized in that said heat distribution and concentration means around the deformable component (10) consist of a sleeve (7) of axis (X) of thermally conductive material surrounding the deformable component ( 10) along its entire length, and having, at a first open end, a radially extending flange (13) whose outer surface is contiguous with the heat transfer surface of the heating element (1 1). .

5. Magnetothermic actuator according to the preceding claim, characterized in that the thermal inertia of the heating part (1 1) and the sleeve (7) is less than that of the coil (5).

6. Magnetothermic actuator according to one of the preceding claims, characterized in that it comprises first thermal insulation means between the magnetic actuator and the thermal actuator.

7. Magnetothermic actuator according to the preceding claim, characterized in that said first thermal insulation means consist of an air gap (12) separating the magnetic actuator from the thermal actuator.

8. Magnetothermic actuator according to the preceding claim, characterized in that said air gap (12) separates said sleeve (7) from the movable core (4), the sleeve (7) being partly inserted into a housing of the movable core ( 4), the sleeve (7) and the movable core (4) being collinear with axis (X).

Magnetothermic actuator according to one of the preceding claims, characterized in that the deformable component (10) consists of a shape memory spring of central axis (X) capable of driving when it regains its original shape by heating. deployed, a first striker (9) colinear to the movable core (4), to a position corresponding to the active state of the actuator, the shape memory spring and the first striker (9) being both positioned inside said sleeve (7), an orifice being provided in the wall of the second end of the sleeve (7) for passing the first striker (9), said first striker (9) and the movable core (4) being able to drive in translation a second striker (2) against the first means of reminders (3) to a position corresponding to the active state of the actuator.

10. Magnetothermic actuator according to the preceding claim, characterized in that the shape memory spring (10) and the first striker (9) are biased to the position corresponding to the inactive state of the actuator by means of second return means (8) located inside said sleeve (7).

1 1. Magnetothermic actuator according to one of the preceding claims, characterized in that it comprises second thermal insulation means between the coil (5) and the thermal actuator.

12. Magnetothermic actuator according to the preceding claim, characterized in that said second thermal insulation means consist of a piece (6) of cylindrical shape axis (X) of plastic type insulating material, and separating the coil (5). ) of all other components of the magnetothermal actuator.

Magnetothermic actuator according to the preceding claim, characterized in that said insulating part (6) comprises:

- a cylindrical jacket (6a) around which is wound the coil (5) and within which are positioned the fixed cores (1) and movable (4), the first return means (3), the second striker (2), as well as the portion of the sleeve (7) of the thermal actuator surrounding the first striker (9) and the second return means (8);

- a plug (6b) closing said jacket (6a) at its proximal end of the heating part (1 1) and separating the heating assembly, namely the heating part (1 1), the flange (13) of the sleeve (7), the deformable component (10) and the part of the sleeve (7) surrounding the deformable component (10), both of the coil (5) and the other components of the magnetic actuator , an orifice being provided in the plug to allow the portion of the sleeve (7) surrounding the first striker to pass

(9).

14. Circuit breaker type electrical protection device comprising a magnetothermic actuator according to one of the preceding claims.