CN107004545B

CN107004545B - Magneto-thermal trigger

Info

Publication number: CN107004545B
Application number: CN201580046728.0A
Authority: CN
Inventors: F.德克特; T.路克斯
Original assignee: Hager Electro SAS
Current assignee: Hager Electro SAS
Priority date: 2014-06-30
Filing date: 2015-06-23
Publication date: 2020-01-14
Anticipated expiration: 2035-06-23
Also published as: JP6693890B2; EP3161850A1; CN107004545A; FR3023057B1; FR3023057A1; WO2016001524A1; EP3161850B1; JP2017520889A

Abstract

The invention relates to a magneto-thermal trigger for an electrical breaking device of the circuit breaker type, comprising: -a magnetic actuator comprising a solenoid (10), said solenoid (10) being placed in series in an electric circuit, surrounding a fixed core and a movable core and driving the latter in the event of a short circuit between two positions respectively representing the two states of non-operation and operation of the actuator; -a thermal actuator comprising a deformable bimetallic strip (21) made of a heat-sensitive material capable of transforming from an initial shape to a final shape under the action of the heat generated in the thermally controlled actuator in the event of an overload, said initial and final shapes representing the two states of non-operation and operation of the actuator, respectively; and further comprises means for increasing the impedance of the circuit. The trigger is characterized in that the means for increasing the circuit impedance comprise a yoke member (1) connected in series with the current path of the trigger between the solenoid (10) and the bimetal (21).

Description

Magneto-thermal trigger

Technical Field

The present invention relates generally to a magnetocaloric trigger, more particularly for electrical apparatuses, in particular of the circuit breaker type, and designed to ensure protection by opening at least one electrical line in the event of a fault that causes an increase in current, for example a rapid increase in current following a short circuit, a slow increase in current in the event of an overload in the circuit.

The invention also relates to an electrical apparatus provided with such a magnetocaloric trigger.

Background

Conventionally, as known from document FR 2943455, a magneto-thermal trigger comprises a magnetic circuit having a movable blade (palette) which pivots with respect to a fixed frame member forming the remainder of the magnetic circuit, said frame member having a U-shaped cross-section and surrounding a thermal bimetallic strip electrically connected to the terminals of the device, a return means maintaining the blade in an open position with respect to the frame member in the absence of a short-circuit current. In the event of a short circuit, the current is sufficient so that the induced magnetic force in the magnetic circuit causes the moving blade to move against the reset means, which allows the locking of the triggering device and thus the opening of the main contacts of the triggering device.

This conventional arrangement works well when the short circuit currents involved are large enough (hundreds or thousands of amperes) to make the magnetocaloric flip-flop operate.

In the case of circuit breakers that must operate at weak short circuit currents (on the order of tens or hundreds of amperes), magnetocaloric triggers conventionally comprise a solenoid, the number of spirals of which can be varied to increase/decrease the length of the solenoid according to the short circuit current it must withstand, and to allow the amperage per turn (lemberd' amp res/sight) to be easily adjusted according to the rated current.

A magnetocaloric trigger of this type comprises a fixed core/movable core that is translationally movable in a magnetic carriage, the movable core being magnetically actuated under the action of a solenoid traversed by a short-circuit current, said movable core driving a mechanical device capable of actuating a trigger lever to trigger the mechanical locking of the circuit breaker. Traditionally, the thermal trigger is still a bimetallic strip.

In order to withstand large thermal stresses when extreme short circuits or service currents are high (in the order of thousands of amperes), resistances are usually added in series in the current path, which allow to increase the overall resistance of the circuit breaker and to limit the current passing through the circuit breaker in case of short circuits. However, these resistors take up space and their integration in current compact devices is problematic.

Another solution of the prior art consists in combining the impedance of the magnetocaloric trigger with the impedance of other components of the circuit breaker that contribute to increasing the impedance, such as the breaking chamber with fixed and movable contacts. The total impedance of the circuit breaker thus allows limiting the short-circuit current, but does not allow magnetocaloric triggering at weak short-circuit currents.

Disclosure of Invention

The object of the present invention is to design a magnetocaloric flip-flop that ensures its magnetocaloric flip-flop function in such a device: the device has to be triggered at weak short-circuit currents, has a sufficient impedance to withstand extreme short-circuits or service currents, and is miniaturized to be able to be integrated into the latest generation of compact devices.

The magnetocaloric flip-flop according to the invention comprises, in a conventional manner:

-a magnetic actuator comprising a solenoid placed in series in an electric circuit, said solenoid surrounding a fixed core and a movable core and driving the movable core in the event of a short circuit between two positions respectively representing two states of non-operation and operation of the actuator;

a thermal actuator comprising a deformable bimetallic strip made of a heat-sensitive material, which is capable of transforming from an initial shape to a final shape under the action of the heat generated in the thermally controlled actuator in the event of an overload, said initial and final shapes representing the two non-operating and operating states of the actuator, respectively.

The magnetocaloric trigger further comprises means for increasing the impedance of the circuit, said means comprising a magnetic frame member connected in series with the current path of the trigger between the solenoid and the bimetal.

The main idea of the invention is to increase the impedance of the trigger by means of a single component, by adjusting the dimensions of this single component, its position within the trigger, its arrangement with the other components of the trigger, and finally by adjusting its material.

The frame member is a component conventionally used in a magneto-thermal trigger having a movable blade. Such a shelf is reused in the magnetic trigger of the invention, which in this case does not operate with a movable blade, but with a movable core. The shelf is a metal part that can take many shapes and therefore can be easily integrated into the trigger, as opposed to an additional resistor, which is furthermore in the current path and requires additional space.

In this case, the frame member surrounds the solenoid by forming a ring around the frame member and is connected to the solenoid at an upper portion and to the bimetal at a lower portion. The shape of the shelf member is thus arranged to best conform to the external shape of the solenoid and thereby occupy the least available space within the device.

The fact that the shelf element is connected at both its ends to the current path means that the current passes completely through the shelf element. However, the longer the path that the current will travel in the circuit, the weaker the short circuit current will be due to the increase in the impedance of the circuit. The selected rack architecture thus allows for maximizing the length of the current path while minimizing the overall volume.

The impedance of the trigger can also be increased by selecting a very high resistivity material for the shelf member. For example, stainless steel is used to achieve a large resistance and steel is used to achieve a small resistance, but the use of other materials is also possible.

According to one possible configuration, the upper portion of the frame piece comprises an upper face beyond which a tongue for connection to the solenoid projects. The lower part of the frame piece comprises a tab for connection to the bimetal, which is positioned below the lower face of the frame piece at a distance therefrom and is oriented perpendicularly thereto, and which is connected to an extension of the side face of the frame piece.

More precisely, the frame element forms a ring having a rectangular outline with four faces, said extension for attachment of the tab of one of the lateral faces being positioned at a first corner of the ring, said tongue exceeding the frame element at a second corner of the ring opposite to the first corner. The tongue and the tab are thus arranged on the frame part in such a way as to be furthest away from each other, so that the path to be traversed by the current in the frame part is maximized. The current arriving through the tongue is divided into the two branches of the ring and meets at the tab.

Preferably, the tabs of the frame member are provided with openings for fixing to the bimetallic strip and form an L-shape with said extensions of the side faces of the frame member. This shape allows the bimetal to be oriented such that its direction of deflection is perpendicular to the trigger lever.

According to the present invention, a current path in the trigger sequentially passes through an input terminal of the trigger, the solenoid, the frame member, the bimetal, the braided part (une stress), and an output terminal of the trigger. The braid is connected either directly to the bimetal or via an intermediate support, which may also be selected from a very high resistivity material to increase the resistance. The use of a flexible braid allows the bi-metallic strip to deflect to actuate the trigger lever.

More specifically, the input terminal is connected to a first end of the solenoid, a second end of the solenoid is connected to a tongue of the frame member, the tab of the frame member is connected to a foot of the bimetal, and the braid connects a head of the bimetal to the output terminal.

The invention also relates to an electrical apparatus for protecting a line, of the circuit breaker type, comprising a magnetocaloric trigger as described above.

The volume of the magnetocaloric trigger with the O-ring, the solenoid and the core according to the invention is equivalent to a conventional magnetocaloric trigger with a U-shaped yoke associated with the movable blade for higher short-circuit currents. This means that the same circuit breaker may, depending on choice, comprise a trigger for weak short-circuit currents according to the invention or a conventional trigger for high short-circuit currents.

Drawings

The invention will now be described in more detail with reference to the accompanying drawings, in which:

FIG. 1 is a cross-sectional view of a magnetocaloric trigger according to the invention;

FIG. 2 is a perspective view of a magneto-thermal trigger according to the present invention;

FIG. 3 shows a magnetic frame piece;

FIG. 4 shows more precisely the arrangement between the frame member and the solenoid by way of a cross-sectional view;

FIG. 5 shows the path that the current travels within the magnetocaloric flip-flop;

fig. 6 and 7 show the integration of the magnetocaloric trigger in a device of the circuit breaker type.

Detailed Description

The magnetocaloric trigger shown in fig. 1 and 2 comprises a thermal actuator comprising a bimetallic strip 21 responsive to an increase in temperature, and a magnetic actuator comprising, in a conventional manner, a solenoid 10 surrounding a fixed core 13 and a movable core 14. The movable core 14 is guided so as to translate in a sleeve 15 made of insulating material, positioned in normal operating conditions against the fixed core 13, driven away from the fixed core 13 by the magnetic field generated by the solenoid 10 in the event of a short circuit.

In this conventional magnetocaloric trigger, a magnetic frame part 1 is added, which magnetic frame part 1 at least partially surrounds a solenoid 10. The magnetic frame member 1 is shown in more detail in fig. 3. The main part of the frame element 1 forms a ring whose outer shape is of rectangular outer shape with four

faces

5, 4, 9, 8. The tongue 2 extends from the upper face 4 of the frame member 1 at a corner 37, while the tab 3 extends below the lower face 8 of the frame member 1. The tab 3 is connected to the loop of the frame member 1 via an extension 6 of the side 5 of the frame member 1 extending at another corner 36 diametrically opposite the corner 37 of the loop. The tab 3 thus extends perpendicularly to both the extension 6 and the lower face 8 of the frame member, and is spaced from the lower face 8. The tab comprises two openings 7 which allow the tab to be secured to a part of the trigger, here a bimetal 21.

The magnet frame member 1 and the solenoid 10 are shown together in fig. 4. The solenoid 10 has a preferably rectangular shape to minimize its depth dimension, leaving sufficient room for the bimetal 21 to be located just behind.

Specifically, the frame member 1 is a member added to increase the length of the current path. In particular, this current path is shown in fig. 5. The thick arrows show the paths of the currents in the magnetocaloric flip-flop. In practice, current enters the trigger via the input terminal 19, one of the branches 20 of which 19 is welded to the first end 11 of the solenoid 10. The current then enters the solenoid 10, passes completely through the solenoid, to its second end 12, which is then welded to the tongue 2 of the frame member 1. The current then enters the frame element 1 via the tongue 2 and is then distributed evenly in the loop of the frame element 1 until it reaches the extension 6 of the side 5 and then finally enters the tab 3. Spacing the tabs 3 from the loop of the frame member 1 allows for a further increase in the current path, since current must also flow in the extensions 6 before reaching the tabs 3.

The tab 3 is fixed to the foot 22 of the bimetal 21 by two rivets 24. The current thus flows from the tab 3 of the frame element 1 to the bimetal 21 and then from the foot 22 of the bimetal through the whole bimetal 21 to its head 23, on which head 23 a support element 25 is fixed, to which support element 25 the

braided parts

26, 27 are welded. The output terminal 28 of the magneto-thermal trigger is welded to one of these braided

parts

26, 27. The current thus reaching the head portion 23 of the bimetal 21 flows into the output terminal 28 via the braided portion 26.

This particular configuration of the magnetocaloric flip-flop allows to significantly increase the path that has to be traversed by the current. This increase is allowed by the addition of the holder member 1 and by the particular arrangement of the bimetal 21 within the trigger. In fact, the current flows from the foot 22 of the bimetal 21 up to the head 23 of the bimetal 21, which increases the length.

The magnetocaloric trigger according to the invention thus allows to significantly increase the impedance within the device in which it can be placed. Here, as shown in fig. 6 and 7, the device may be, for example, a circuit breaker. In fact, the magnetic frame element 1, due to its particular shape and its positioning within the magnetocaloric trigger, occupies only a very small space for the magnetic frame element 1. The magnetic carriage member surrounds the solenoid and intelligently fills the empty space between the solenoid and the other components of the trigger.

In particular, in the event of a short circuit in the line, the magnetic actuator will drive the movable core 14 in translation. The movable core 14 in turn actuates a movable handle 16 (see fig. 1 and 2) rotating about an axis 17 of a bearing 18 fixed to the upper face 4 of the frame member 1. The handle 16 drives the rotation of a triggering lever 29 (visible in particular in fig. 6), which triggering lever 29 actuates a lock that allows the circuit breaker to be opened in the event of a short circuit.

Likewise, in the event of an overload, the bimetallic strip 21 actuates the same trigger lever via a calibrated screw 30 (also visible in fig. 6). In this case, the head 23 of the bimetal will tend to deflect until bearing against the screw 30.

Fig. 7 thus shows a circuit breaker provided with a magnetocaloric trigger according to the invention. In the case shown in the figure, the fixed contacts 32 and the movable contacts 33 are enclosed in the breaking chamber 31. Current flows through the contacts 32, 33 and the bridge 35 to the connection 34 fixed to the input terminal 19 of the magnetocaloric trigger.

The configurations shown in the above figures are only non-limiting possible examples of the invention, which on the contrary comprises form and design variants that can be realized by a person skilled in the art.

Claims

1. A magneto-thermal trigger for an electrical breaking device of the circuit breaker type, comprising:

magnetic actuator comprising a solenoid (10) placed in series in an electric circuit, said solenoid (10) surrounding a fixed core (13) and a movable core (14) and driving said movable core (14) in the event of a short circuit between two positions respectively representing two states of non-operation and operation of said actuator;

a thermal actuator comprising a deformable bimetallic strip (21) made of a heat-sensitive material, the bimetallic strip (21) being capable of transforming from an initial shape to a final shape under the effect of the heat generated in the thermal actuator in the event of an overload, the initial shape and the final shape respectively representing two states of non-operation and operation of the actuator;

and further comprising means for increasing the impedance of the circuit,

characterized in that said means for increasing the impedance of said circuit comprises a magnetic frame member (1) connected in series with the current path of said trigger between said solenoid (10) and said bimetal (21),

the frame member (1) surrounds the solenoid (10) by forming a closed loop around the solenoid (10) and is connected at an upper portion to the solenoid (10) and at a lower portion to the bimetal (21).

2. Magnetocaloric trigger for an electrical breaking apparatus of the circuit breaker type according to claim 1, characterized in that said upper portion of said magnetic frame element (1) comprises an upper face (4) beyond which upper face (4) a tongue (2) for connection to said solenoid (10) is present.

3. Magnetocaloric trigger for an electrical breaking apparatus of the circuit breaker type according to claim 2, characterized in that said lower portion of said magnetic frame member (1) comprises a tab (3) for connection to said bimetallic strip (21), said tab (3) being positioned at a distance from the lower face (8) of said magnetic frame member (1) below said lower face (8) and oriented perpendicularly to said lower face (8), and said tab (3) being connected to an extension (6) of a side face (5) of said magnetic frame member (1).

4. Magnetocaloric trigger for an electrical breaking apparatus of the circuit breaker type according to claim 3, characterized in that said magnetic frame member (1) forms a ring with a rectangular profile having four faces (5, 4, 9, 8), said extension (6) of one of the side faces for connecting said tab (3) being positioned at a first corner (36) of said ring, said tongue (2) exceeding said frame member (1) at a second corner (37) of said ring opposite said first corner (36).

5. Magnetocaloric trigger for an electrical breaking apparatus of the circuit breaker type according to claim 4, characterized in that said tab (3) of said frame member (1) is provided with an opening (7) for fixing to said bimetallic strip (21) and forms an L-shape with said prolongation (6) of the side (5) of said frame member (1).

6. Magnetocaloric trigger for an electrical breaking device of the circuit breaker type according to claim 5, characterized in that the current path inside the trigger passes successively through the input terminal (19) of the trigger, the solenoid (10), the frame (1), the bimetal (21), the braid (26) and the output terminal (28) of the trigger.

7. Magnetocaloric trigger for an electrical breaking device of the circuit breaker type according to claim 6, characterized in that said input terminal (19) is connected to a first end (11) of said solenoid (10), a second end (12) of said solenoid (10) is connected to said tongue (2) of said frame (1), said tab (3) of said frame (1) is connected to a foot (22) of said bimetal (21), said braid (26) connects a head (23) of said bimetal (21) to said output terminal (28).

8. An electrical apparatus for protecting a line of the circuit breaker type comprising a magneto-thermal trigger as claimed in any one of claims 1 to 7.