FR2840449A1 - AUTOMATIC RESETTING DEVICE FOR MODULAR PROTECTION DEVICE TO BE CONTROLLED - Google Patents

Abstract

The present invention relates to an automatic reset and remote control device for modular protective equipment to be controlled, having a general shape corresponding to a modular apparatus (2), to which it must be coupled. Device characterized in that it essentially consists of a mechanical means (1 ') for arming and opening which can be connected to the modular apparatus to be controlled (2) by means of a disengageable device (3) and by an electromagnetic means (4) for controlling the mechanical means (1 ') for arming and opening. The invention is more particularly applicable in the field of electrical installations, in particular the protection of the various circuits against overloads. such as short circuits and direct or indirect contacts, by means of electrical safety equipment such as circuit breakers, earth leakage circuit breakers or earth leakage switches, and in particular remote control devices for such equipment.

Description

D E S C R I P T I O N

  The present invention relates to the field of electrical installations, in particular the protection of different circuits against overloads such as short circuits and direct or indirect contacts, by means of electrical safety devices such as circuit breakers, differential circuit breakers. or differential switches, and in particular devices for remote control of such devices, and for their object an automatic reset and remote control device for

  modular protection equipment.

  For some of these circuits, switching off after a fault can cause significant inconvenience for the user, for example in the case of a circuit supplying a freezing, heating, protective equipment fire or when a control device is located in an unsupervised room, for example in a

industrial installation.

  The triggering of a protective device did not always originate from a frank and permanent fault. Indeed, such a trip can come from transient faults which disappear of themselves, for example from an ounce of current or transient voltage due to a lightning strike on the current transmission line, a condensation generating o humidity significant likely to cause earthly

disappears after drying, etc ...

  In such cases, there are automatic reset devices performing one or more successive reclosing attempts at increasingly long time intervals. Such devices are mainly used in urban installations of the candelabra type,

  public shelters, illuminated signs, etc ...

  The design of these electrical safety devices involves electronics for the differential function. In addition, these devices are often fitted with simple contact means which only tolerate relatively small nominal currents and have

  limited short circuit performance.

  There is therefore the problem of repetition of the re-

  switching on or off of these devices and of the overload on the contact means. Indeed, in the event of the persistence of a defect, it is advantageous to be able to avoid an excessive number of rearmaments and

  So limit these, ah to preserve the continuity of contacts.

  To this end, it has been proposed, by French patent application No. 00 15029, an automatic reset device for modular protective equipment to be controlled, which has a general shape corresponding to a modular apparatus to which it must be coupled and which is provided, on the one hand, with fixing and indexing means on the modular apparatus to be controlled, on the other hand, means for actuating a control handle or the like of said apparatus oa to control and, finally, means of viewing the state of

  operation of the device and faults detected by it.

  This device allows, of course, to be able to remotely control a very wide range of products from the current nominal admissible and performance point of view, by juxtaposition to a modular product designed to protect conventional electrical installations in the domestic as well as in the industrial field. , but is only suitable for all-or-nothing operation, that is to say an engagement or re-engagement or a reset of a modular protective device or the like or to a trigger or an opening of the

o contacts of such equipment.

  The purpose of the present invention is to overcome the drawbacks of the devices known to date by proposing an automatic reset and remote control device for modular protective equipment making it possible, on the one hand, to control a very wide range of products from the point of view permissible nominal currents and performance and, on the other hand,

  not to disturb the functioning of the associated product.

  To this end, the automatic rearmament and remote control device for modular protection apparatus to be controlled, which has a general shape correspond to a modular apparatus, where it must be coupled. is characterized in that it is essentially constituted by a mechanical arming and opening means which can be connected to the modular apparatus to be controlled by means of a disengageable device and by an electromagnetic means for controlling the

  mechanical means of arming and opening.

  The invention will be better understood, thanks to the description below

  after, which relates to a preferred embodiment, given as - 3 of nonlimiting example, and explains with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a perspective view of the device according to the invention during arming, the casing being in the open position; Figure 2 is a perspective view of the device in combination with a modular apparatus to be controlled; Figures 3 and 4 are partial views in side elevation of the mechanism, on a larger scale, showing the mechanical means of arming and opening and electromagnetic control o respectively in the arming position and in the opening position; Figure 5 is a perspective view, on a larger scale, of said mechanical arming and opening and electromagnetic control devices; Figure 6 is an exploded perspective view of the device; Figures 7a to 7h and 8a to 8g respectively show partial views in side elevation representing the kinematics of arming and opening of the mechanical iteration of arming and opening, and Figure 9 is an electrical diagram of '' a diet of

  the electromagnet constitute the electromagnetic control means 4.

  o Figures 1 and 2 of the accompanying drawings show an automatic rearmament and remote control device 1 for modular protective equipment to be controlled, which has a general shape

  correspond to a modular device 2 to which it must be coupled.

  Such a device is in particular intended to be mounted on a mounting rail

  an electrical panel or cabinet.

  In accordance with the invention, this automatic rearmament and remote control device is essentially constituted by a mechanical means 1 'of arming and opening which can be connected to the modular apparatus to be controlled 2 by means of a device o disengageable 3 and by electromagnetic means 4 for controlling the means

  1 'arming and opening mechanism.

  The mechanical means 1 'for arming and opening is an assembly constituted, as shown in FIGS. 1 and 3 to 6 of the accompanying drawings, by a control handle 5 pivotally mounted in the housing 6 of the device and protruding by its lever 5 'outside said casing 6, by a connecting rod or maneuvering hook 7 articulated on the joystick 5, by an actuating finger 8 also articulated on the joystick 5 and by a fork - 4 9 for driving the joystick 5. This joystick 5 has a central pivoting mounting part in the housing 6 of the device by means of pivots 10 of the latter and is provided, on the side opposite the lever 5 ′ with respect to the axis 10, of two bearings 11 and 12, offset radially and respectively from articulation of the maneuvering finger 8 and of the rod or

  operating hook 7 (Figures 3 and 4).

  The fork 9 for driving the lever 5 is advantageously in the form of an independent lever comprising two arms substantially aligned on either side of a pivoting mounting axis 9 ′ in which the housing 6 of the device, l 'one of the arms cooperating at its end with the connecting rod or maneuvering hook 7 by means of drive projections 29, in order to achieve an engagement, and the opposite arm co operating by s is exkemite with the electromagnetic means of control 4. This fork 9 is provided, moreover, substantially in its central part, with a drive cam 13 intended to actuate the finger.

  mancouvre 8 to make an opening (Figures 4, 7 and 8).

  The connecting rod or maneuvering hook 7 is mounted with the possibility of pivoting, at one of its ends, in the articulation bearing 12 of the control lever S by means of an axis o 14, the opposite end being constituted by two elements each provided with an internal retaining spout 15, determining a central recess of the rod and allowing ['insertion of the corresponding end of the fork 9, one of the elements being provided with an external guide pin 16 intended to cooperate with a guide 17 provided in the housing 6 of the device and: 5 extending at least partially around the central part of the lever (Figures 1 and 3 to 8). Thus, during an engagement or rearmament movement, the end of the fork 9 can engage in the retaining bees 15 and turn on the rod or hook 7 in the direction of a

  lever pivot drive 5.

  o Furthermore, the connecting rod or maneuvering hook 7 is provided, at its mounting end in the bearing 12 of the lever 5, with a cam 7 'intended to cooperate with the operating finger 8 during an operation of armament or rearmament. Such a cam 7 'allows, by pressing against the finger 8, to partially pivot the latter around its axis in the bearing 11 to avoid its engagement with the fork 9, on the cam

  drive 13, during an arming or recovery operation

  engagement. - 5 The maneuvering finger 8 is guided at one end in the bearing 11 corresponding to the lever 5 via a connecting pin and present at its opposite end, on the one hand, a support part 18 intended to cooperate with the drive cam 13 of the fork 9 drive the handle 5 and, on the other hand, a guide element 19 in the form of a rib intended to cooperate with a guide 20 provided in the housing 6 of the device (Figures 1, 3, 4 and 6). This maneuvering finger 8, as well as the maneuvering rod or hook 7, is loaded, in ouke, by a double-acting return spring, not shown, constituted by two elements of spiral spring connected together and acting by their ends free respectively on the connecting rod or maneuvering hook 7 and on the operating finger 8 to push them clockwise in the direction of the central mounting part of the lever S and tend to retract the hook 7 in the direction of the guide 17 and to be pressed the finger 8 on the cam 7 'of the hook 7. Thus, the rod or hook s of mancouvre 7 and the operating finger 8 are automatically released respectively from the field of action of the drive fork 9 and of the electromagnetic means 4 control, so that these two elements wind firmly subject to their only function and that a risk of hooking of the first is avoided during the opening phase, while the second is o maintained in hooking with the cam ment entered ^ 13 of the fork 9 during said opening phase, the spring opposing the force determined in the arming or opening phase to avoid, in cooperation with the guide, that the finger collides with the electromagnetic means 4 In addition, the guide 20 guarantees that the finger 8 does not collide with the

medium 4.

  The electromagnetic means 4 is constituted by an electro-

  magnet fixed by its carcass in the housing 6 and whose movable core 4 'is provided with a means 4 "intended to cooperate with the corresponding end of the drive fork 9. Preferably, the means 4 "of the core 4 'is presented in the form of a circumferential groove cooperating with nipples

  9 "provided on the corresponding arm of the drive fork 9.

  Furthermore, the part of the fork 9 carries the pins 9 "delimits between its branches an internal wall with a toric surface. Thus, the fork 9 ensures, by pressing on the core 4 ', in the deployed position

  extreme of this, a guide to said core 4 '.

  The prediction of the pins 9 "allows an axial distribution of the forces transmitted by the core 4 'of the electromagnet, so that, in - 6 combination with the support produced by the fork 9, the risk of bending

is reduced.

  Preferably, the nipples 9 "are diamond-shaped. I1 in

  results that they present an increased mechanical resistance.

  s The disengageable device 3 is in the form of a guide slide on the lever of the lever 5 protruding out of the housing 6 and cooperating in an identical manner with the handle of the modular apparatus to be controlled 2 (FIG. 2). This slide can be moved to the right or to the left relative to the housing 6 and the control lever 5 in

  o depending on the position of the modular equipment to be controlled 2.

  According to a characteristic of the invention, the slide forming the disengageable device 3 is further provided, on the one hand, with a transverse median recess 3 'and, on the other hand, on either side of this recess 3 'and close to it, stops 3 "intended to cooperate with lunules s end 6'. The obviously 3 'is intended to allow the establishment of a locking means in the intermediate position such as a padlock or the like and the 3 "wind stops provided for stopping the slide in

  translation and avoid disassembly, so as to make it captive.

  Furthermore, the slide forming the disengageable device 3 is o advantageously provided, on its internal surface cooperating with the external surface of the lever of the control lever 5, at least one heart point, preferably several of these points, s '' strongly pressing on the corresponding surface of the lever. Such curs points make it possible to lock the device 3 in a given position of drive connection of a

s switchgear to order.

  In the central position of the device 3 on the control handle 5, the device according to the invention is uncoupled from the apparatus to be controlled 2 and can be padlocked in this position by using a padlock cooperating with the obviously 3 'and a hole

  o correspond to the lever of the joystick 5.

  In accordance with another characteristic of the invention, the slide forming the disengageable means 3 is provided, in addition, at each end with an index 3 "'intended to cooperate with a corresponding notch 6" of the lunulas 6' for blocking in rotation of the

  s control lever 5 in intermediate position.

  The device according to the invention is maintained in mechanical coupling with the apparatus to be controlled 2 by at least one, and preferably by trotting coupling clips 21 cooperating, through steps 22, with corresponding housings provided respectively on at least one side of the equipment to be connected. Such a coupling clip 21 is advantageously in the form of an elastically deformable bar under pressure. Thus, such a bar can have a slightly domed shape and two end pastes 22 cooperating with the corresponding housings and ['application by pressure allowing a snap of the pastes, while another pressure on the central part of the bar allows '' make a slight translation to the right or to the left in order to extract one of the steps, then the

clip release.

  According to another characteristic of the invention, the control handle 5 is provided under its part carry the bearings 11 and 12 with a tongue 23 (Figures 1 and 3 to 6) for positioning intended to cooperate with s position sensors ( not shown), these sensors being arranged in alignment with said tongue 23 respectively in the positions

of arming and opening.

  This tab 23 thus makes it possible to know at all times the exact position of the lever 5, tent in its extreme positions, in which the corresponding detectors are actuated, than in its position

  intermediate, in which none of the detectors is activated.

  Such an intermediate position corresponds either to a lockout position, or to a position in which the contacts of the switchgear control unit 2 are stuck. Thus, the user can instantly detect either an intervention on the protected circuit or a

  anomaly on a protective device connected to the control device.

  The operation of the automatic reset device for modular protective equipment to be controlled, in accordance with the invention will be described below with reference to FIGS. 7 and 8 of the drawings.

annexes.

  To bring the handle of a control device 2 from its operating position (ON) to an open position (OFF), the core 4 ′ of the electromagnetic means 4, which is. in a rest position, taken out of the armature in said means 4, under the combined effect of gravity and a load by spring (not shown), is drawn into said armature (FIG. 4) and swivels the fork 9 ( Figures 7a and 7b) by means of the pins

9 "cooperating with throat 4".

  - 8 During the rotation of the fork 9 around its axis, during the rekaction of the core 4 ', the entrainment cam 13 comes into contact with the bearing part 18 of the pressure finger 8 and exerts on the latter a thrust transmitting a rotational movement to the control lever S (FIG. 7c). During the entire approach movement, the operating finger 8 is applied against the fork arm 9 opposite to that cooperating with the core 4 ′ of the electromagnet through its

spiral return spring.

  When the fork 9, during its pivoting, arrives at the extreme point of maximum displacement of the finger 8 and therefore of rotation of the lever S. the latter crosses its point of stability, which corresponds to that of the control lever of the control apparatus, and is driven by the handle of the control apparatus in pivoting in its open position (figure 7d). The control of the electromagnet forming the electromagnetic means 4 being a pulse control, the core 4 'automatically returns to its starting position under the effect of gravity and the load of a return spring not shown. In this movement, the fork 9 passes with its arm opposite the core 4 ′ of the electromagnet between the elements provided with internal retaining bees 1S o and the central recess of the rod or hook 7, its projection projections 29 then bypassing the interior retaining bees 15 by passing over the latter and crossing the central recess correspond together

  with its support arm (figures 7e at 7h).

  During this movement back to the starting position of the core 4 ′ and of the fork 9, this behind causes a slight pivoting of the hook or link 7 around its bearing 12 on the lever S. without however acting on the position of this behind, the return spring of the hook or link 7 bringing the latter against said lever S. at the end of the race Figures 7g and 7h). o The re-engagement or arming, that is to say the passage from an OFF position of the lever S to an ON position, is also carried out by delivery of a withdrawal pulse from the core 4 'in [' armature of the electromagnet forming the electromagnetic control means 4

(Figures 4 and 8).

  The fork 9 then engages by its drive projections 29 in the interior retaining bees 1S of the hook or link 7 (fgure 8a), so that the latter is started by the fork 9 and causes a corresponding rotation of the lever. 5 in the opposite direction to that of the fork 9 (FIGS. 8b to 8e). During this rotation of the lever 5 and of the fork 9, the finger 8 tends to approach the cam 13 of the fork 3 and to come into contact with this behind. To avoid such contact, which would prevent the operation of the device in the arming direction, the cam 7 ′ of the hook or link 7 presses against the corresponding edge of the finger 8 and partially separates it from the handle 5. In the same movement, the end of the support part 18 is shifted out of contact with the cam 13

  (Figure 8d) to rest externally on this behind.

  o When the fork 9, during its pivoting, arrives at the point of stability of the handle of the associated apparatus, the handle 5

  why its course until the arrival in position.

  On arrival at the end of the race, the core 4 'automatically returns to its starting position, as explained above and

  shown in Figures 8e to 8g and 7a.

  In the engagement and opening positions, the lever 5 can perfectly be actuated independently of the electromagnetic control means 4, so that the operation of the associated equipment to be controlled 1 is in no way disturbed, the fork 9

o being in this case disengaged.

  The position sensors (not shown), which are intended to cooperate with the positioning tab 23 of the control handle 5, make it possible not only to detect the arming and opening positions, but also, by default, a intermediate position of the lever 5, no sensor detecting the position of the tongue 23, or a power cut, the two sensors delivering the

  same presence signal, which is necessarily to be considered erroneous.

  In accordance with another characteristic of the invention, to avoid arming spleens, the electromagnet forming the so electromagnetic means 4 is advantageously provided with a stepped supply 24 at several levels (FIG. 9). Such a supply makes it possible to successively subject the electromagnet, which is a very fast actuator, to low, medium and high power, so that its

  acceleration, which is generally important, can be modulated.

  This multi-level step supply 24 is constituted by control stages 27, 28 of the same type each provided with a switching element 29, 30 and a series resistor 25, 26 for limiting the supply current. of the electromagnet, the number of power levels being determined by the formula 2Nb-1, in which Nb represents the number of stages. A significant number of floors

  command will allow a finer gesti on of the electro-magnet.

  The value of the resistors 25, 26 decreases from the first stage 27 to the others 28. Thus, when the electromagnet is actuated, these two stages 27, 28 are shown in figure 9 of the annexed drawings. successively in a binary manner as follows: o First stage 27 closed and second stage 28 open = current limited by the resistance 25 - First stage 27 open and second stage 28 closed = current limited by the resistance 26 - First stage 27 closed and second stage 28 closed = current limit by 25x26 +26 Because the resistance 25 is stronger than the resistance 26, the power developed by the electromagnet is weakest when the first stage 27 is only closed and the strongest when the two floors 27,

28 firm winds.

  The first stage 27 could, for example, be used to make up for the mechanical clearances, in order to suppress shocks, while the following stages 28 will provide acceleration according to the need of the product. In fact, a product that is difficult to arm will be at the end of the travel stop and therefore subjected to an acceleration when the second pulse is delivered. The switching elements 29, 30 can be of the triac, thyristor, IGBT, transistor or relay type depending on the characteristics of the

  voltage and electromagnet uses.

  o Thanks to the invention, it is possible to produce a rearming device making it possible to control a very wide range of products from the point of view of nominal current admissible and performance. This device is perfectly juxtaposable with a modular product designed to protect conventional electrical installations in the domestic as well as in the industrial field, without requiring any particular connection or tool. - 11 In addition, the device allows maneuvers of the lock of the device to be controlled without arming rate or untimely opening,

  while ensuring a full cocking stroke.

  Of course, the invention is not limited to the embodiment described and shown in the accompanying drawings. Modifications remain possible, in particular from the point of view of the constitution of the different elements or by substitution of technical equivalents, without leaving

  provided the scope of protection of the invention.

- 12

Claims (16)

REVENDI C ATI ON S   1. Automatic reset and remote control device for modular protective equipment to be controlled, having a general shape corresponding to a modular apparatus (2), to which it must be coupled, characterized in that it is essentially constituted by mechanical means ( 1 ') for arming and opening which can be connected to the modular equipment to be controlled (2) by means of a disengageable device (3) and by an electromagnetic means (4) for controlling the   mechanical means (1 ') of arming and opening.   2. Device according to claim 1, characterized in that the mechanical means o (1 ') of arming and opening is an assembly constituted by a control handle (5) pivotally mounted in a housing ^ 6 ) of the device and protruding by its lever (5 ′) out of said housing (6), by a connecting rod or operating hook (7) articulated on the lever (5), by an actuating finger (8) also articulated on the lever (S) and by a   handle (9) drive fork (9).   3. Device according to claim 2, characterized in that the control handle (5) has a central pivotally mounting part in the housing ^ tier (6) of the device by means of pivots (10) of the latter and is provided, on the opposite side to the lever (5 ') relative to the axis (10), o of two bearings (11 and 12), radially and respectively offset articulations of the operating finger (8) and of the connecting rod or hook maneuver (7).   4. Device according to claim 2, characterized in that the fork (9) entramement of the lever (5) is in the form of an independent lever comprising two arms substantially aligned on either side of an axis (9 ′) pivotally mounted in the housing (6) of the device, one of the arms cooperating at its end with the connecting rod or operating hook (7) by means of drive projections (29), to achieve an engagement, and the opposite arm cooperating at its end with the   o electromagnetic control means (4).   5. Device according to claim 4, characterized in that the fork (9) is provided, moreover, substantially in its central part, with a drive cam (13) intended to actuate the actuating finger ( 8) to make an opening.   - 13 6. Device according to claim 3, characterized in that the connecting rod or operating hook (7) is mounted with the possibility of pivoting, at one of its exkemites, in the articulation bearing (12) of the control handle (5) by means of an axis (14), the opposite end being constituted by two elements each provided with an internal retaining spout (15), determining a central recess of the link and allowing ['insertion of the corresponding end of the fork (9), one of the elements being provided with an external guide pin (16) intended to cooperate with a guide (17) provided in the housing (6) of the device and o extending at least partially around the central part of the handle (5). 7. Device according to claim 6, characterized in that the connecting rod or operating hook (7) is provided, at its mounting end in the bearing (12) of the lever (5), with a cam (7 ' ) intended to cooperate with the operating finger (8) during an arming or rearming operation.   8. Device according to any one of claims 3 to 5,   characterized in that the operating finger (8) is guided at one end in the bearing (11) corresponding to the handle (5) by means of an o connecting axis and present at its opposite end, with a firstly, a support part (18) intended to cooperate with the drive cam (13) of the fork (9) driving the lever (5) and, secondly, a guide element (19 ) in the form of a rib intended to cooperate with a guide   (20) provided in the housing (6) of the device.   s 9. Device according to any one of claims 3 to 6   and 8, characterized in that the operating finger (8), as well as the operating link or hook (7), is loaded, in addition, by a double-acting return spring constituted by two spiral spring elements connected between them and acting by their free end respectively on the connecting rod or hook o operating (7) and on the maneuvering finger (8) to push them clockwise towards the central mounting part and tend to retract the hook (7 ) towards the guide (17) and place the finger (8) on the cam (7 ') of the hook (7).   10. Device according to any one of claims 1 and   2, characterized in that the electromagnetic means (4) is constituted by an electromagnet fixed by its casing in the housing (6) and whose movable core - 14 (4 ') is provided with means (4 ") intended to cooperate with the end   corresponding to the drive fork (9).   11. Device according to claim 10, characterized in that the means (4 ") of the core (4 ') is in the form of a circumferential groove cooperating with pins (9") provided on the arm   correspond to the drive fork (9).   12. Device according to claim 4, characterized in that the part of the fork (9) carry the pins (9 ") delimited between its branches   an inner wall with a toric surface.   o 13. Device according to claim 11, characterized in that   the nipples (9 ") are diamond shaped.   14. Device according to any one of claims 1 and   2, characterized in that the disengageable device (3) is in the form of a guide slide on the lever of the lever (5) protruding out of the housing (6) and cooperating identically with the lever of   modular equipment to be controlled (2).   1S. Device according to claim 14, characterized in that the slide forming the disengageable device (3) is further provided, on the one hand, with a median transverse recess (3 ') and, on the other hand, and o other of this obviously (3 ') and close to it, of stops (3 ")   intended to cooperate with end lunules (6 ').   16. Device according to claim 14, characterized in that the slide forming the disengageable device (3) is provided, on its internal surface cooperating with the external surface of the lever of the control lever (5), of at least one point cur, preferably several of these   points, resting strongly on the corresponding surface of the lever.   17. Device according to claim 14, characterized in that the slide forming the disengageable means (3) is provided, in addition, at each end with an index (3 "') intended to cooperate with a corresponding notch (6 ") of the lunulas (6 ') for the purpose of blocking the rotation of the   control handle (S) in intermediate position.   18. Device according to claim l, characterized in that it is maintained in mechanical coupling with the apparatus to be controlled (2) by at least one 'and preferably by trotting coupling clips (21) cooperating, by the intermediary of steps (22), with corresponding housings provided respectively on at least one face of the equipment to be connected.   - 15 19. Device according to claim 18, characterized in that the coupling clip (21) is in the form of a bar   elastically deformable under pressure.   20. Device according to claim 2, characterized in that s the control handle (5) is provided under its part carry the bearings (11 and 12) of a tongue (23) for positioning intended to cooperate with sensors position, these sensors being arranged in alignment with said tongue (23) respectively in the arming and opening positions. o 21. Device according to claim 2, characterized in that the electromagnet forming the electromagnetic means (4) is provided with a floor power supply (24).   22. Device according to claim 21, characterized in that the multi-level stepped supply (24) is constituted by control stages (27, 28) of the same type each provided with a switching element ( 29, 30) and a series resistance (25, 26) for limiting the supply current of the electromagnet, the number of supply levels being determined by the formula 2Nb-1, in which Nb represents the number of floors.   o 23. Device according to claim 22, characterized in that the value of the resistors (25, 26) decreases from the first stage (27) to the others (28).   24. Device according to claim 22, characterized in that the switching elements (29, 30) wind of the triac, thyristor, IGBT, transistor or relay type depending on the characteristics of the voltage and