EP2926355B1 - Actuator with a thermomagnetic shunt, especially for triggering a circuit breaker - Google Patents

Description

TECHNICAL AREA

The invention relates to the triggering of electrical protection equipment such as circuit breakers, particularly in the field of low voltage. More generally, the invention relates to an electromagnetic actuator that can be used as a single trigger of a switchgear.

STATE OF THE ART

A circuit breaker makes it possible to protect an electric line by cutting the current in the event of a fault, in particular on short circuit, when the intensity exceeds a high threshold, or in case of overload, when the intensity remains in values close to the rated current but over a long period.

To fulfill both safety criteria, in the usual way and as illustrated in figure 1 , most low voltage modular circuit breakers 1 are equipped with two types of trip unit connected to the line to be protected: an electromagnetic actuator 2 separates contacts 4, 6 in the event of a short circuit, a bimetallic thermal trip unit 8 reacts to overloads : see for example FR 2 682 533 . According to the circuit breaker range, the electromagnetic actuator 2 can take various forms, in particular with a plunger core as presented in connection with the figure 1 or pallet as described in FR 2,772,981 . An actuator can also be of bistable type as in the patent application EP1792326 .

The presence of two distinct elements 2, 8 allows a separate setting of the trip parameters on both types of faults. This bimetallic design / actuator, however, requires sufficient volume in the case of the circuit breaker 1, and involves a large number of parts to assemble.

It is sometimes envisaged to overcome one of the two elements, with for example a magneto-hydraulic actuator (or " dashpot " according to the English terminology) described in US 2,690,528 , or a bimetallic system with sudden turning (called bimetallic bimetal, as described in EP 1 001 444 ). In addition to the disadvantages inherent in their design (difficulty of adjustment, respectively limitation of breaking capacity), these solutions, however, retain two principles of operation coupled to one another.

SUMMARY OF THE INVENTION

Among other advantages, the invention aims to overcome the drawbacks of existing circuit breaker trip units, in particular by proposing a new type of electromagnetic actuator to ensure tripping over short circuit and overload.

In one of its aspects, the invention thus relates to an electromagnetic actuator that allows the mobilization of a contact which is secured to it both when the current exceeds a nominal value over a long period, than when the current exceeds a threshold punctually.

The invention relates in particular to an electromagnetic actuator in which a magnetic shunt device is set up at the coil, in series with respect to the path of the magnetic flux, said shunt device comprising a magnetothermic (or magnetocaloric) material, that is to say a material whose magnetization increases with the temperature above a first temperature greater than or equal to 330 K, and in particular has a peak whose maximum is greater than 40 emu / g, with rapid increase in magnetization between 350 and 420 K under a magnetic field of 0.2 to 2 T. The magnetocaloric material is in particular an alloy of nickel and manganese, preferably of the NiCoMnX type, with X selected from aluminum, indium, antimony or tin.

The actuator as such is conventional, with a magnetic circuit comprising a fixed magnetic carcass, a coil capable of being connected to an electrical circuit at its ends, and a magnetic element movable relative to the carcass as a function of the intensity of the current flowing in the coil. In particular, the movable magnetic element may be a plunger which moves within the coil, the core and the coil being housed in the carcass; alternatively, the movable magnetic element may be of the pallet type, with a U-shaped casing of which at least one of the branches is surrounded by the coil, and the pallet moving relative to the branches of the U to close it.

The shunt device may extend along the axis of the coil, especially indoors for a plunger actuator; preferably in the form of a cylinder, it can be composed entirely of the magnetocaloric material or its effects can be dimensioned by adapting the rate of magnetocaloric material within it. The dimensions of the cylinder are also adapted to the desired force for the shunt device relative to the current flowing in the coil.

The electromagnetic actuator may be implemented in a switchgear, such as a molded case modular circuit breaker, wherein one of the switchgear contacts is coupled to the actuator movable member to open or close. the line according to the current flowing in the coil. In particular, the actuator can form a device for tripping such a switchgear device, the coil then being coupled to the line that the breaking device is made to protect and the movable element can be coupled to a moving contact. of the apparatus, for example rigidly.

BRIEF DESCRIPTION OF THE FIGURES

• La figure 1, déjà décrite, illustre un disjoncteur basse tension à boîtier moulé dans lequel l'actionneur selon l'invention peut être mis en place.
• La figure 2 montre les caractéristiques du matériau qui peut être utilisé dans le shunt d'un actionneur selon l'invention.
• La figure 3 représente un actionneur selon un mode de réalisation de l'invention, avec illustration des forces d'induction magnétique selon le courant y circulant.
• La figure 4 montre un autre mode de réalisation d'un disjoncteur selon l'invention.

Other advantages and features will emerge more clearly from the following description of particular embodiments of the invention, given by way of illustration and in no way limiting, represented in the appended figures.

• The figure 1 , already described, illustrates a low-voltage circuit breaker with a molded case in which the actuator according to the invention can be put in place.
• The figure 2 shows the characteristics of the material that can be used in the shunt of an actuator according to the invention.
• The figure 3 represents an actuator according to one embodiment of the invention, with illustration of the magnetic induction forces according to the current flowing therethrough.
• The figure 4 shows another embodiment of a circuit breaker according to the invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

The action of the bimetallic strip in a tripping system is replaced according to the invention by a saturable magnetic shunt system, which is integrated with a conventional electromagnetic actuator, which retains its role of triggering on a short circuit. The shunt associated with the actuator thus takes overload tripping function.

For this purpose, the material of the shunt is chosen for its magnetothermic or magnetocaloric properties. More specifically, as illustrated in figure 2 the material is such that its degree of magnetization M has a peak as a function of temperature. In particular, at low temperature, the material is little, if any, magnetic. When the temperature increases, beyond a first temperature T ₀ , the magnetization M of the material increases rapidly, reaching a maximum at a second temperature T ₁ , beyond which the magnetization decreases until it vanishes for the Curie temperature Tc of the material. These different temperatures T ₀ , T ₁ , Tc themselves depend on the applied magnetic field H (see the variations obtained for a field of 0.2 T and a field of 7 T in figure 2 ).

For use according to the invention, the first temperature T ₀ is chosen to be greater than 330 K, preferably close to 350 K. This choice is made possible by the use of materials of the NiCoMnX family, with X ∈ {Al, In , Sb, Sn}, preferably aluminum or tin: for these materials, the transition is well marked with a temperature T ₁ close to T ₀ (difference of 10 to 30 K) and a high magnetization, of the order of 70 emu / g. In particular, for Ni ₄₀ Co ₁₀ Mn ₃₃ Al ₁₇ , T ₀ = 347 K, Mmax = 90 emu / g.

The actuator according to the invention thus comprises a shunt associated with the coil. In particular, as illustrated in figures 3 , an actuator 10 according to the invention comprises a magnetic circuit with a fixed magnetic housing 12 housing a longitudinal coil 14 within which can move a magnetic plunger core 16. The coil 14 is connected to a power supply line and, as a function of the current flowing therein, induces a magnetic field B in the magnetic circuit which moves the core 16 along the axis of the coil 14.

A device 18 comprising the magnetocaloric material is placed around the coil 14, within the carcass 12, to form a magnetic shunt in the magnetic circuit. The shunt device 18 preferably forms a cylinder housed in the carcass 12. The shunt can be provided by the device 18 in its entirety, then composed in its entirety of magnetothermic material; preferably, the shunt device 18 is thus formed of stacked washers, or even juxtaposed bars or cut sheets. Alternatively, the shunt device 18 may comprise a support which is associated, or in which is integrated, a part of magnetocaloric material, which allows a simplified form such as a cylinder; the shunt device 18 may also form a part of the carcass 12 to which are associated, for example inserted in grooves or contiguous, elements of suitable material.

As illustrated in figure 3A when the current I passing through the coil 14 is less than or equal to the nominal current I _nom , the temperature of the assembly 10 remains low, close to the ambient temperature. The temperature of the shunt device 18 remains lower than the first temperature T ₀ : the shunt is in its non-magnetic state and the reluctance of the magnetic circuit is strong, similar to that of the same actuator without shunt device. The force of the field B induced on the magnetic core 16 remains low and below the trigger threshold: the core 16 remains in its rest position.

When the current I exceeds an overload value I _s , a rise in temperature occurs within the coil 14. As a result of this rise, the temperature at the shunt device 18 increases to be at least transiently, in the range of magnetization, between T ₀ and T ₁ : the magnetothermic material goes into its magnetic state. As illustrated in figure 3B , the shunt device 18 then channels the induced flux B and the reluctance of the circuit decreases. The force on the mobile core 16 increases progressively, to become greater than the trigger threshold: the mobile core 16 moves, and it can unlock the mechanism of the circuit breaker 1 to open the line in which it is placed.

Advantageously, a direct thermal contact is provided between the shunt 18 and the coil 14. In fact, the shunt in magnetocaloric material sees its magnetic state depend on the temperature and the magnetic field to which it is subjected, values which, in turn, depend on the value of the current I flowing in the coil 14. The dimensioning of the system 10 makes it possible to position the corresponding value of the overcurrent current I _s to locate the induced temperature in the range [T ₀ , T ₁ ] of non-magnetic phase transition / Magnetic material, and size the field induced by the shunt to allow the displacement of the core 16 and therefore the tripping of a circuit breaker 1 associated with the actuator 10. In particular, it is possible to choose the amount of material of the shunt, in particular via the length and the section, or even the composition, of the device 18, as well as the length and the section of the turns of the winding 14.

It should be noted that if the current I exceeds the value of the short-circuit current I _cc , it causes a magnetic saturation of the entire circuit, regardless of the state of the magnetothermic material of the shunt 18: sufficient flow B pass in all cases by the mobile core 16 to cause its movement and therefore the tripping of the circuit breaker 1 ( figure 3C ).

The shunt device 18 therefore has little influence on the operation of the actuator 10 in the event of a short circuit. In addition, since it is positioned in the leakage flux of the winding 14, the shunt 18 has little influence on the attraction force of the mobile core 16 at rated current I _nom . The actuator 10 can therefore maintain the current dimensions and design according to the cut-off and operating parameters required for its short-circuit cut-off functions, even if the characteristics of the tripping system according to the invention can allow optimization.

Thus, an actuator 10 according to the invention set up in a switchgear device, in particular a molded and / or modular molded 1-BT circuit breaker as illustrated in FIG. figure 1 , allows to perform both protection functions by a single component, exclusively magnetic and without the need to heat a bimetallic strip. Volume is released by the absence of bimetallic, volume that becomes available within the housing for new features. The overall heat dissipation of the apparatus 1, 10 is also restricted, which increases its reliability and energy efficiency. Finally, the disappearance of the thermal adjustment allows a reduction in industrial costs, as the reduction in the number of parts to assemble.

Although the invention has been described with reference to an electromagnetic actuator 10 with a moving plunger 16, it is not limited thereto: other elements may be concerned by the introduction of such a magnetothermal shunt, in order to substitute the magnetic and thermal triggers of existing circuit breakers. In particular, the use of a saturable magnetic shunt system, the role of which is to channel a greater or lesser part of the flux as a function of the current flowing in the product, can be adapted for an electromagnetic pallet actuator, in particular for use in a switchgear.

• une carcasse magnétique fixe 22 sensiblement en U ;
• une bobine 24 reliée à la ligne de courant par ses extrémités et encadrant une branche au moins du U magnétique 22 :
• une palette 26 mobile relativement à la carcasse 22 en fonction du courant circulant dans la bobine 24, entre une position de repos dans laquelle un entrefer existe entre le U 22 et la palette 26, et une position de coupure dans laquelle la palette 26 referme ledit U 22 ;
• un dispositif de shunt 28 en matériau magnétothermique mis en place au sein de la bobine 24, plus généralement le long de l'axe du bobinage 24.

Thus, as illustrated in figure 4 , the switching device 1 'comprises two movable contacts 4, 6 relatively to one another, at least one of the two contacts being associated with the moving part of an electromagnetic actuator 20 whose magnetic circuit comprises:

• a fixed magnetic carcass 22 substantially U;
• a coil 24 connected to the current line by its ends and flanking at least one branch of the magnetic U-22:
• a pallet 26 movable relative to the carcass 22 as a function of the current flowing in the coil 24, between a rest position in which an air gap exists between the U 22 and the paddle 26, and a breaking position in which the paddle 26 closes said U 22;
• a shunt device 28 made of magnetothermic material placed in the coil 24, more generally along the axis of the coil 24.

Here again, the heating of the shunt 28 is achieved by thermal contact with the coil 24 traversed by the current and / or by the Joule effect by circulating all or part of the current in the active material. The two functions of the circuit breaker 1 'are thus provided by a single triggering and actuating device 20, in a more efficient manner from the technical, economic, environmental and industrial point of view.

Claims (9)

1. Electromagnetic actuator (10, 20) comprising a magnetic circuit with a fixed magnetic frame (12, 22), a coil (14, 24) capable of being connected to an electrical circuit at its ends, and a magnetic element (16, 26) movable with respect to the frame (12, 22) according to the intensity of the current flowing in the coil (14, 24), comprising a shunt device (18, 28) extending along the axis of the coil (14, 24),
   characterized in that said shunt device (18, 28) comprising a magnetocaloric material for which the magnetization increases with temperature above a first temperature (T₀) greater than or equal to 330 K and reaches a maximum at a second temperature (T₁) of less than 420 K, said magnetization maximum being greater than 40 emu/g.
2. Actuator according to Claim 1, wherein the magnetocaloric material is an alloy of nickel and manganese.
3. Actuator according to Claim 2, wherein the magnetocaloric material is of the NiCoMnX type, where X ∈ {Al, In, Sb, Sn}.
4. Actuator according to one of Claims 1 to 3, wherein the movable magnetic element is a solenoid plunger (16) housed in the coil (14) within which it moves, the plunger/coil assembly (14, 16) being housed in the frame (12).
5. Actuator according to one of Claims 1 to 4, wherein the shunt device (18, 28) forms a cylinder around the coil (14, 24).
6. Actuator according to one of Claims 1 to 5, wherein the magnetic element is an armature (26), the frame (22) forming a U-shape, at least one of the branches of which is surrounded by the coil (24), the armature (26) moving with respect to the frame (22) in order to close said U-shape.
7. Cut-off unit (1, 1') comprising a pair of contacts (4, 6) movable with respect to one another and an actuator (10, 20) according to one of Claims 1 to 6, at least one of the contacts being coupled to the movable element (16, 26) of said actuator (10, 20).
8. Circuit breaker tripping device comprising an actuator (10, 20) according to one of Claims 1 to 6, the movable element (16, 26) and the coil (14, 24) of said actuator (10, 20) being suitable for being coupled to a current-carrying line to be protected.
9. Modular circuit breaker (1) comprising a casing housing a tripping device according to Claim 8 and a pair of contacts movable with respect to one another, a first contact (4) being coupled to the movable element (16, 26) of the actuator (10, 20).

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