FR2772980A1 - MAGNETO-THERMAL TRIPPING DEVICE AND CIRCUIT BREAKER EQUIPPED WITH THIS DEVICE - Google Patents

Abstract

As the heater elements and bimetallic strip are separate, the switch can be adapted to the circuit breaker caliber. The unit can be separated into two parts.

Description

MAGNETO-THERMAL TRIGGER DEVICE AND

  CIRCUIT BREAKER EQUIPPED WITH THIS DEVICE.

  The present invention relates to a magnetothermal tripping device in particular for a circuit breaker, comprising a magnetic trip device capable of causing tripping of the circuit breaker mechanism during a sudden rise in current following a short circuit, and a thermal trip device comprising a suitable bimetallic strip cause tripping of the circuit breaker mechanism in the event of a

  current overload resulting in a slow rise in current.

  A device of the kind previously mentioned described in document DE 3,637,275 is known. This document describes a trip device comprising magnetic trip means and thermal trip means. The first include a coil supported by a good heat conducting sheath closed at one of its ends, and inside which are mounted on the one hand, a so-called fixed core, fixed inside the sheath, and a said mobile core, mounted sliding inside the sheath with interposition between the two cores, of a spring. A striker is slidably mounted inside the fixed core and has one end bearing on the movable core, and another end capable of cooperating with the tripping mechanism of the circuit breaker. Thus, during a sudden rise in the current through the coil, in the event of a short circuit, the magnetic field generated by the coil causes a displacement of the mobile core and consequently of the striker,

  which triggers the mechanism.

  The thermal triggering means comprise a bimetallic strip supported between one of the enlarged ends of the aforementioned sheath and a capsule, said bimetallic strip being traversed by the aforementioned striker and cooperating with a ring belonging to the striker.

  so as to drive said striker during a current overload.

  However, in this solution, the temperature rise of the blistering bimetallic strip is done by the coil which must first heat the sheath made of alurhinium and the fixed steel core, which in turn will transmit their heat to the blistering bimetallic strip, from o it results in a significant reaction time of the bimetallic strip. In addition, in this embodiment, the two electromagnetic and thermal devices being dependent, they can hardly

to be separated.

  The present invention solves these problems and proposes a magneto-thermal tripping device of simple design, having a short reaction time, including

  the size can be easily adapted and which allows a separation of the two parts.

  To this end, the subject of the present invention is a device of the aforementioned type, this device being characterized in that the thermal trip device comprises a means of heating the bimetallic strip traversed by the current to be monitored and capable of transmitting any rise in temperature to the bimetallic strip corresponding to an increase in current through the heating means, said heating means being independent of the magnetic trip device so as to be able to be adapted to the rating

and / or the standard of the device.

  According to a particular embodiment, the bimetallic strip is directly in contact with the means

of heating.

  According to a particular characteristic, the shape of the heating means is adapted to

that of the bimetallic strip.

  According to a particular embodiment, the bimetallic strip being in the form of a concave disc, the aforementioned heating means is also in the form of a concave disc. i 5 According to a particular characteristic, this heating means is produced in a

  electrically conductive material with high electrical resistivity.

  According to another characteristic, the shape of the heating means as well as its

  thickness are adapted, depending on the size and / or standard of the device.

  According to another characteristic, the aforementioned heating means comprises a cutout and the shape of this cutout and / or the thickness of the heating means are determined so as to confer on said driver an impedance adapted to the different ratings.

and standards.

  Thus, we see that the material in which the driver will be made as well as its formatting, can be determined so as to give the heating means an impedance adapted to the different calibers and standards of the device. In addition, the driver being independent, the two triggers namely magnetic and thermal

  can be placed away from each other.

  The present invention also relates to a device comprising the characteristics

  previously mentioned taken alone or in combination.

  But other advantages and characteristics of the invention will appear better in the

  detailed description which follows and refers to the attached drawings given only to

  by way of example and in which: - Figures 1 and 2 are two views in axial section along respectively two perpendicular planes, of the magneto-thermal actuator of the invention in the rest position; - Figure 3 is an exploded perspective view of said device; - Figures 4 and 5 are two views similar to Figs. 1 and 2, in the device's magnetic release position; - Figures 6 and 7 are two views similar to Figs. 1 and 2 in the device's thermal release position; - Figures 8, 9 and 10 illustrate in perspective, respectively, three embodiments

  different from a so-called bimetal heater element according to the invention.

  1 0 In FIGS. 1 to 7, there is seen a magneto-thermal trip device D intended for use in a low voltage electric circuit breaker (not shown) in order to protect an electrical circuit against overloads or short circuits. This circuit breaker mainly comprises, in a manner known per se, a pair of respectively fixed and movable separable contacts, a mechanism for controlling the opening and closing of the circuit breaker actuated by a lever, an electromagnetic trip device E intended to trip the mechanism of the circuit breaker and thus cause the opening of the contacts when a short-circuit current appears and a thermal trip device

  T able to trigger the mechanism when a current overload occurs.

  According to the embodiment illustrated in the figures and in particular in Figure 3, the electromagnetic trip device E comprises a flange 1 on which is fixed a fixed core 2, a plastic sheath 3 force-fitted around the fixed core 2, a coil 4 mounted around sheath 3 and having one end 4a welded to the flange 1, a U-shaped carcass covering the coil 4, said carcass 5 comprising in its base an orifice 6 intended to allow the introduction and the sliding of a movable core 7 , said carcass 5 also comprising around this orifice 6 an annular recess 8 intended to receive one 3b of the ends of the aforementioned sheath 3, and being welded to the flange 1 by the free end 5a of one of its two wings . This movable core 7 is secured by its end 7a located inside the sheath 3, at one of the ends 9a of a striker 9 mounted sliding inside the fixed core 2, and whose opposite end 9b is intended to cooperate with a percussion lever 10 (fig. 1 and 2) capable of triggering the mechanics and striking the movable contact. The fixed core 2 has a recess 13 (fig. 1) adapted to receive, via one 12b of these ends, a spring 12 mounted around the striker 9 and the other end 12a of which rests on the movable core 7. It will be noted that this striker 9 is crimped in an orifice 7b of the movable core 7 in order to avoid parasitic play. This spring 12 is intended to return the movable core 7 to the rest position as illustrated in FIGS. 1 and 2. The assembly comprising the sheath 3, the coil 4 and the two cores 2 and 7 is mounted inside a carcass 5 comprising at one of these ends an orifice 6 for the passage of the movable core 7 and closed at its opposite end by a flange 1, said flange 1 being electrically connected on the one hand to the coil 4 and on the other hand to the heating means

16 of the coil.

  The thermal part T of the magneto-thermal trip device comprises a so-called upper capsule 14 comprising a recess 14a adapted to receive a bimetallic strip 15 known as a blister consisting of a disc convex towards the side opposite the capsule in the rest position, a so-called heater element 16 comprising a disc, one of the faces 16a of which (fig. 3) has a convex shape corresponding to the convex shape of the bimetallic strip 15, said driver 16 also comprising a radial slot 17 whose function will be explained later, as well as two legs 18.19 s 'extending substantially perpendicular to the plane of the aforementioned disc in two opposite directions. The thermal trip device further comprises a so-called lower capsule 20 in the form of a plate, said capsule being intended to be fixed to the heating element 16 by one of these faces and comprising a central orifice 20a in which the stud 2a associated with the core fixed 2 is force fitted to secure the thermal part to the magnetic part. It can be seen in particular in FIGS. 1 and 2 that the bimetallic strip as well as the heating means are trapped between the lower capsule 20 supporting the heating means 16 and the upper capsule 14 comprising the recess 14a, said recess 14a comprising a flange circumferential 14b, said bimetallic strip 15 being immobilized between this rim 14b and the circumferential edge 16b of the heating means 16. As can be seen more particularly in FIG. 2, the face 16a of the heating element 16, which is intended to be in contact with the bimetallic strip 15 is adapted to that of the bimetallic strip 15 so that the total surface of the bimetallic strip is in contact with the heating element in the rest position of the trigger. In a manner known per se, the disc constituting the bimetallic strip 15 is made of a material sensitive to the temperature of such

  so that the shape of the bimetallic strip changes due to a change in temperature.

  So when the temperature reaches a so-called trigger temperature, the

disc curvature is reversed.

  It can also be seen that orifices 17, 15a are provided respectively in the heating element 16, the bimetallic strip 15 and the upper capsule 14 and are intended to allow the

  passage of the striker 9 and allow it to slide through these elements.

  As seen in Figures 8 to 10, the driver 16 may include a cutout 17 (opening) whose size is determined according to the size of the circuit breaker. Indeed, the shape of the driver 16, its dimensions as well as the material in which it is made, can be determined so as to give it an impedance adapted to the different sizes and standards of the devices. Thus, in FIG. 8, the driver 16 has an elongated opening 17 extending substantially from the center to the outside diameter of the disc and having a width corresponding substantially to the spacing of two legs 18,19. In fact, the resistance of the driver 16 is proportional to the length of the current path between the two ranges 18,19 and to the resistance of the material, but is inversely proportional to the width 1 of the track. In fig. 9, the disc has an opening 17 extending radially from the outer edge of the disc over half of its radius, and this over a circumferential length corresponding substantially to half of the previous one. In Figure 10, no opening is provided except that intended for the passage of the striker. Thus, the value of the resistance of the first driver shown in Figure 8, is lower than that of the second driver shown in Figure 9, which

  is less than that of the driver illustrated in FIG. 10.

  The bimetallic strip 15 and the striker 9 cooperate respectively with two perpendicular arms l00b, 10a belonging to a return lever 10 controlling the tripping bar of the circuit breaker, the arm 10b cooperating with the bimetallic strip 15 passing through

the upper capsule 14.

  The operation of the triggering device of the invention will be described below.

with reference to the figures.

  In FIGS. 1 and 2, the device of the invention is in the rest position corresponding to normal operation of the device during which the current (I in FIG. 3) flows through the coil 4, then through the flange 1, then reaches the driver 16 via one 18 of its tracks 18,19, and joins the other 19 of the driver's tracks by circulating around the cutout 17, after which the current reaches the contact

  mobile, in electrical contact with the fixed contact (not shown).

  We will first describe the operation of the device during a trip

  of magnetic origin with reference to Figures 1,2,4 and 5.

  In the case of a sudden rise in current following a short circuit, a magnetic field is generated by the coil 4. When the value of the current exceeds a predetermined threshold, a magnetic threshold is reached, which causes the displacement of the

  movable core 7 towards the fixed core 2 as illustrated in FIGS. 4 and 5.

  The core-striker assembly then strikes the deflection lever 10, which firstly, after a certain displacement movement of the lever act on the trigger bar to control the triggering of the mechanism and secondly, after a stroke additional movement of the lever, act on the movable contact to cause the abrupt opening of the contacts. Thus, according to the invention, the striker fulfills two functions, because on the one hand it acts on the triggering mechanism and on the other hand, it exerts a percussion on the movable contact, for it

  give a large opening force on short circuit.

  We will now describe the operation of the device during a trip.

of thermal origin.

  In the case of a slow rise in the current following a current overload, the so-called driver element 16 through which this current flows will rise in temperature and transmit this rise to the blistering bimetallic strip 15 located in contact with it. Because the current flows directly into the part 16 which is in contact with the bimetallic strip, the reaction time of this bimetallic strip is considerably reduced. When the bimetallic strip has reached its turning temperature, it turns instantly, as illustrated in FIGS. 6 and 7, that is to say it passes from a position in which it is curved in the direction of the coil 4 in a position in which it is curved towards the lever

reference 10.

  During this reversal, the bimetallic strip 15 directly strikes the return lever 10 which will act on the tripping bar of the circuit breaker and cause tripping

of the mechanism.

  It will be noted that the bimetallic strip 15 being encapsulated with the heating part 16, this assembly becomes less dependent on the surrounding heating sources generated by the

  coil 14, the fixed contact and the movable contact.

  Note that the driver 16 will be made of a special electrically conductive alloy having a high resistivity such as stainless steel, while the lower and upper capsules will advantageously be made of plastic. The scabbard

  insulation can be made of plastic.

  It will also be noted that the heating means will not necessarily be in direct contact with the bimetallic strip, but that an air film or the like may be interposed

  between the bimetallic strip and the heating means.

Claims (16)

  1- 1. Magneto-thermal trip device in particular for a circuit breaker, comprising a magnetic trip device capable of causing a trip of the circuit breaker mechanism during an abrupt rise in current following for example a short circuit, and a thermal trip device comprising a bimetallic strip capable of causing tripping of the circuit breaker mechanism in the event of an overload resulting in a slow rise in current, characterized in that the thermal trip device comprises means for heating (16) of the bimetallic strip (15) traversed by the current to be monitored and suitable transmitting to the bimetallic strip (15) any rise in temperature corresponding to a rise in current through the heating means (16), said heating means (16) being independent of the magnetic trigger so as to be able to be adapted to the size and / or to the device standard. 2. Device according to claim 1, characterized in that the bimetallic strip (15) is directly in contact with the heating means (16) or separated from the means of   heating (16) via an air film.   3. Device according to claim 1 or 2, characterized in that the shape of the bimetallic strip   (15) is adapted to that of the heating means (16).   4. Device according to claim 3, characterized in that the bimetallic strip (15) being in the form of a concave disc, the aforementioned heating means (16) is substantially in the form of a concave disc comprising two contact pads (18.19).   5. Device according to any one of the preceding claims, characterized in that   that said heating means (16) is made of a conductive material of   electricity with high electrical resistivity.   6. Device according to claim 5, characterized in that the heating means   (16) is adapted in shape and thickness to the size and / or standard of the device.   7. Device according to any one of the preceding claims, characterized in that   that the aforementioned heating means (16) comprises a cutout (17) and in that the shape of the cutout (17) and / or the thickness of said heating element (16) are determined so as to confer on said heating means (16) impedance   adapted to the different calibers and standards of the device. ?   8. Device according to any one of the preceding claims, characterized in that   that the magnetic trip device comprising a striker (9) capable of causing the triggering of the mechanism during a rapid rise in current, the heating element (16) as well as the bimetallic strip (15) respectively comprise two opposite orifices (17, 15a) allowing passage of the striker (9), said striker (9) being able to cooperate with a lever (10) or the like controlling the triggering of the mechanism.   9. Device according to any one of claims 1 to 8, characterized in that in   in the event of an overload, the bimetallic strip (15) acts directly on a return lever (10)   commanding the circuit breaker trip bar.   10. Device according to any one of the preceding claims, characterized in   that the bimetallic strip (15) and the heating means (16) are trapped between a lower capsule (20) supporting the heating means (16) and an upper capsule (14) comprising a recess (14a), said recess comprising a circumferential rim (14b), said bimetallic strip (15) being immobilized between this rim   circumferential (14b) and the circumferential edge (16b) of the heating means (16>).   11. Device according to any one of the preceding claims, characterized in   what it comprises a coil (4) crossed by the current to be monitored and supported by a sheath (3), a fixed core (2) fixed inside the sheath (3), a movable core (7) mounted to slide inside the sheath (3) and secured to one end of a striker (9), said striker (9) being slidably mounted through the fixed core (2) and being liable to be driven in translation by the movable core (7) under the effect of a variation of the magnetic field created by the coil, said   coil being electrically connected to said heating means (16).   12. Device according to claim 11, characterized in that the assembly comprising the coil (4), the sheath (3) and the two cores (2,7) is mounted inside a carcass (5) comprising at one of its ends an orifice (6) for the passage of the movable core (7) and closed at its opposite end by a flange (1), said flange (1) being electrically connected on the one hand to the coil (4 ), on the other hand by means of heating (16) of the coil (4).   13. Device according to any one of the preceding claims, characterized in   that the heating means (16) comprises two legs (18,19) extending substantially perpendicular to the plane of the heating means (16) in opposite directions, said legs being electrically connected respectively to the flange (1) and in movable contact.   14. Device according to any one of claims 10 to 13, characterized in that   that the bimetallic strip (15) and the striker (9) cooperate respectively with two substantially perpendicular arms (10a, 10b) belonging to a return lever (10) controlling the tripping of the circuit breaker, the arm (10b) cooperating with the   bimetallic strip (15) passing through the upper capsule (14).   15. Device according to any one of the preceding claims, characterized in   that in the event of current overload, the bimetallic strip reverses causing a percussion on the return lever whereas in the event of a short circuit, the striker (9) strikes the return lever (10), which in a first time triggers the mechanism and then acts on the moving contact to transmit it   a large opening force on short circuit.   16. Circuit breaker equipped with a magnetic trip device according to one   any of claims 1 to 15.