EP0348316A1 - Device with an electric, annular, insulated coil - Google Patents

Abstract

The device according to the invention comprises a toric magnetic circuit (20) with rectangular cross-section, covered with an insulator, and on which is wound an internal electrical winding (26). Upper (56) and lower (57) toric caps are applied onto the upper face and the lower face of the internal electrical winding (26), and are covered with an external electrical winding (48). A space (62, 63) separates the respective edges of the upper cap (56) and of the lower cap (57), encouraging thermal exchanges. The invention improves the thermal performance of toric transformers. <IMAGE>

Description

The present invention relates to electrical devices intended for the transmission of electrical energy, and more particularly to devices with electrical coils wound on a toroidal magnetic circuit, that is to say of closed annular shape, and provided with electrical isolation means. .

Electric transformers are known, for example, generally called toroidal transformers, the magnetic core of which has a closed annular shape. The primary and secondary windings of such a transformer are generally wound on top of each other. We know that such a transformer is, at equal power, less bulky and lighter than a conventional magnetic circuit transformer with two or three columns.

Such a toroidal transformer is however more difficult to produce, and in particular more difficult to wind, since the magnetic circuit is already closed during the winding and the electric winding wire must pass as many times through the central chimney of the magnetic circuit as '' there are turns to form the winding. This winding is all the more difficult when the intended use of the device requires the provision of effective electrical insulation: electrical insulators occupy a significant volume which, in current solutions, significantly reduces the dimensions of the central chimney when several electrical windings must be superimposed.

An important problem which the present invention aims to solve is the thermal heating appearing in the windings and in particular the transformers with toroidal circuit. At equal power, this temperature rise is relatively greater than in transformers with a conventional magnetic circuit with three columns, because in these conventional transformers, the heat exchange surfaces between the interior and the exterior are significantly greater. In the case of a toroidal transformer, the internal electrical winding is totally trapped by the layers of electrical insulation and by the external electrical winding, so that the heat exchanges are considerably slowed down.

The invention therefore provides particularly advantageous embodiments, in which the means of electrical insulation have a shape and a structure favoring the thermal transfer from the internal electrical winding towards outside, and notably increasing the natural cooling of the windings. Consequently, such a structure makes it possible to reduce the cross section of the conductors, hence a significant gain on the weight of copper, a very expensive material.

Another important object of the invention is to considerably reduce the number of parts necessary to ensure the electrical insulation of the windings. This results in a reduction in the cost of raw materials, and above all a reduction in the cost of the labor required for assembly.

According to another object of the invention, the new structure is relatively inexpensive, because the magnetic circuit is composed of elements whose shapes are simple and easy to produce, and whose assembly is particularly rapid and requires only a little workforce. The structure is also particularly well suited to allow very extensive automation of the assembly.

In particular, the insulation between two successive electrical windings can be ensured according to the invention by adapting only two insulating parts of appropriate shapes which fit directly onto the internal winding, and positioning themselves.

The invention also allows the winding of toroidal transformers with a flat wire of large section. Due to the rectangular cross-section of the magnetic circuit, the turns are arranged radially. They are therefore contiguous in the bore of the torus and spread over the outer periphery, by difference in the developed lengths of the outside and inside diameters of the torus. After having wound a first layer of contiguous turns in the bore of the torus, the next layer tends to be superimposed on the previous one in the bore, but to be inserted between the turns of the first layer on the external periphery. In an intermediate zone, the external turns come to bear on the internal turns at a point on their edge, so that the contact taking place on a very small surface constitutes a support zone at very high pressure liable to damage the electrical isolation. The invention provides means for avoiding this effect of concentrating the tensile force on two occasional support at each turn, without however having to use additional layers of electrical insulation.

Another object of the invention is to reduce the average length of the turns constituting the electrical windings of the transformer, without harming the electrical insulation or the section of the magnetic circuit.

To achieve these and other objects, the toric device according to the present invention comprises a closed annular main magnetic circuit and means for electrically isolating the external surface of the magnetic circuit, the assembly having an annular shape with a substantially rectangular section. and being limited by a substantially planar crown-shaped upper surface, by a substantially planar crown-shaped lower surface, by a cylindrical inner surface and by a cylindrical outer surface. An interior electrical winding is wound on the insulation of the main magnetic circuit, an intermediate electrical isolation surrounds the interior electrical winding, and an exterior electrical winding is wound around the intermediate electrical insulation. According to the invention,
the intermediate electrical isolation means comprise first and second opposite rigid insulating elements applied respectively directly against two opposite surfaces of the interior electrical winding,
- the rigid insulating elements protrude slightly on either side of the opposite surfaces against which they are applied, defining four protruding contours,
the protruding contours of the first insulating element are separated from the respective opposite protruding contours of the second insulating element by a space devoid of solid electrical insulator,
- the external electrical winding turns comprise two parts bearing against the external faces of the rigid insulating elements, and two parts stretched between the respective contours facing each other of the rigid insulating elements, the tensioned winding parts electrical exterior being separated and isolated from the interior electrical winding by the space devoid of solid electrical insulation, which promotes the transfer of heat energy.

In one embodiment, the electrical isolation means include an electrically insulating upper toric cap and an electrically insulating lower toric cap; each toric cap is limited by a circular external contour of diameter only a little greater than the external diameter of the ring formed by the internal electrical winding, and being limited by a circular internal contour of diameter only a little less than the internal diameter of l ring formed by the internal electrical winding; the respective contours of the upper cap and the lower cap opposite one another are separated by a space promoting the transfer of heat energy. This embodiment significantly increases the transfer of heat energy from the interior winding to the outside, and provides a significant gain in space in the central bore of the circuit.

The outer faces of the cap edges advantageously have a rounded cross section. This arrangement significantly reduces the length of copper necessary for the realization of the electrical winding, and improves the regularity of winding.

Optionally, the caps themselves ensure the maintenance of electrostatic screens, and / or the maintenance of auxiliary magnetic cores such as magnetic leakage circuits.

Rigid insulating elements can be used to isolate two separate electrical windings from each other, for example the primary and secondary of a transformer. They can also be used to isolate one from the other of the successive layers of the same electrical winding.

• - la figure 1 représente une vue générale de côté d'un transformateur selon la présente invention ;
• - la figure 2 représente une vue de dessus du transformateur de la figure 1 ;
• - la figure 3 est une vue de dessus en coupe selon le plan A-A de la figure 1 dans un premier mode de réalisation ;
• - la figure 4 est une demi-vue de côté en coupe selon le plan C-C et à plus grande échelle de la figure 3 ; - la figure 5 illustre les inconvénients d'un bobinage de fil de gros diamètre sur un circuit à section rectangulaire ;
• - la figure 6 illustre l'avantage de bobinage d'un fil de gros diamètre sur un circuit dont les coins sont arrondis ;
• - la figure 7 illustre les inconvénients de bobinage d'un conducteur électrique plat à section rectangulaire sur un circuit magnétique torique ;
• - la figure 8 illustre, à grande échelle, l'imbrication des spires selon la présente invention ;
• - la figure 9 est une vue en bout d'axe des enroulements électriques de transformateur torique à conducteur électrique plat de section importan­te ; et
• - la figure 10 est une demie-vue de côté en coupe selon le plan C-C de la figure 3, dans un second mode de réalisation.

Other objects, characteristics and advantages of the present invention will emerge from the following description of particular embodiments, given in relation to the attached figures, among which:

• - Figure 1 shows a general side view of a transformer according to the present invention;
• - Figure 2 shows a top view of the transformer of Figure 1;
• - Figure 3 is a top view in section along the plane AA of Figure 1 in a first embodiment;
• - Figure 4 is a half side view in section along the plane CC and on a larger scale of Figure 3; - Figure 5 illustrates the disadvantages of a large diameter wire winding on a rectangular section circuit;
• - Figure 6 illustrates the advantage of winding a large diameter wire on a circuit whose corners are rounded;
• - Figure 7 illustrates the disadvantages of winding a flat electrical conductor with rectangular section on a toroidal magnetic circuit;
• - Figure 8 illustrates, on a large scale, the nesting of the turns according to the present invention;
• - Figure 9 is an end-of-axis view of the electrical windings of toroidal transformer with flat electrical conductor of large section; and
• - Figure 10 is a half side view in section along the plane CC of Figure 3, in a second embodiment.

The device according to the present invention, shown in Figures 1 and 2, has a generally annular external shape. The body 1 of the device is a ring of axis I-I and of substantially rectangular section. The body is integral with a fixing and transport assembly 2 comprising a first end element 3 and a second end element 4 applied respectively to the first flank 5 of the body 1 and to the second flank 6 of the body 1. The end elements 3 and 4 are connected by a central connecting column 7, surmounted by a carrying loop 8.

In the embodiment shown in FIG. 2, the end elements, such as the first element 3, comprise three divergent branches in a star. Thus, the first end element 3 comprises the branches 9, 10 and 11. The branches meet in the center, in the axis II of the device, and are integral with the central connecting column 7. The central connecting column 7 crosses the central chimney 12 of the body 1. A support plate 13, integral with the first end element 3, supports the electrical connection terminals of the device. The divergent branches have their internal faces shaped to match the shape of the first flank 5 or of the second flank 6 of the body 1, in the vicinity of the central chimney 12 of the body 1, thus ensuring a lateral connection between the body 1 and the assembly of fixing and transport 2.

Figures 3 and 4 illustrate the internal constitution of the body 1 of a transformer according to a first embodiment of the invention. For clarity of the drawings, the sheets of the magnetic circuit have been partially represented; the same applies to the conductors constituting the transformer windings, conductors which are shown in cross section in FIG. 3 and in longitudinal section in FIG. 4.

In the embodiment shown in these figures, the transformer comprises a main magnetic circuit 20 in the form of a closed circular ring, of rectangular section. The magnetic circuit consists, in known manner, of a circular sheet winding.

The magnetic circuit 20 is electrically isolated over its entire surface. According to this embodiment, the means for electrically isolating the magnetic circuit comprise: an insulating upper toroidal cap 50 of the magnetic circuit, defining an upper surface in the form of a substantially planar crown, and covering the upper face of the magnetic circuit 20; a lower insulating cap 51 of the magnetic circuit, defining a lower surface in the form of a substantially flat crown, covering the lower face of the magnetic circuit 20. The caps cover part of the outer and inner lateral faces of the magnetic circuit. The caps 50 and 51 are connected by an outer cylindrical electrical insulator 52 and an inner cylindrical electrical insulator 53, respectively forming an outer cylindrical surface and an inner cylindrical surface. The upper 50 and lower 51 caps for magnetic circuit isolation have, on their external faces, a rounded outer edge 54, and a rounded inner edge 55.

The advantage of the rounded edges 54 and 55 is explained in relation to FIG. 5: when the electrical conductor is wound on the toroidal magnetic circuit, and more particularly when the electrical conductor has a relatively large section, it is not possible to bend the conductor at right angles to the passage of each edge. Thus, in FIG. 5, when the magnetic circuit has sharp edges, the electrical conductor, wound around the magnetic circuit 20 in the direction of the arrow 156, forms rounded corners, the beginning of each curve starting at the passage of the corner of magnetic circuit, the end of each curve ending away from the circuit magnetic, thus defining at each corner a clearance such as clearance 157. With a conductor whose thickness is approximately 2 mm, such clearance can exceed 3 mm. As a result, the electrical winding occupies a much larger section than the section of the magnetic circuit, and this section is offset from the section of the magnetic circuit, as shown in Figure 5. In addition to the loss caused by the increase resulting in volume, winding difficulties ensue, and the winding generally lacks regularity.

On the contrary, by providing rounded edges such as edges 54 and 55, the electrical conductor follows the shape of the edge perfectly on each pass, and is thus correctly applied to the insulation, each of its branches being parallel to the corresponding side of the magnetic circuit. One might think that the fact of providing rounded edges 54 and 55 would tend to increase the apparent section of the assembly formed by the magnetic circuit and its external insulator. In reality, and surprisingly, it can be seen that this arrangement tends, on the contrary, to reduce the length of the turn of the conductor surrounding the magnetic circuit, and this results in a saving of copper forming this conductor.

A partial wrapping can join the insulators 50, 51, 52 and 53 around the magnetic circuit. The sub-assembly thus formed is easy to handle, and then receives, by winding, in a known manner, the first internal electrical winding 26. In the embodiment shown, the internal winding 26 consists of a suitable number of turns of flat electrical conductor with rectangular section. There is shown a three-layer winding, a first layer 260 formed of radial turns which are contiguous in the central chimney 12 of the circuit, and which are spaced from one another on the lateral external peripheral face of the circuit; this first layer 260 is covered by a second layer 261, shown partially in Figure 9, formed of radial turns also contiguous in the central chimney 12, itself surmounted by a third layer 262 of the same structure, which covers it.

An upper toric cap 56 is fitted against the upper flank 28 of the inner electrical winding 26, and a lower toric cap 57 is fitted against the lower flank 30 of the inner electrical winding 26. The upper toric caps 56 and lower 57 are made of an electrically insulating material having a certain flexibility. Preferably, the upper 56 and lower 57 caps are identical. They respectively have circular external protruding contours 58 and 59 of diameter only a little greater than the external diameter of the ring formed by the internal electrical winding 26. The caps 56 and 57 are limited by an internal contour protruding respectively 60 and 61 , circular in diameter only a little less than the inside diameter of the ring formed by the inside electric winding 26. The projecting outside contours 58 and 59 of the two caps 56 and 57 are separated from each other by a space 62 promoting the transfer of heat energy from the inner winding 26 to the outside. Likewise, the protruding interior contours 60 and 61 are separated from each other by a space 63 favoring the passage of heat energy from the interior winding 26 towards the central chimney 12.

The upper 56 and lower 57 caps are shaped to be applied with little play on the inner winding 26. After their installation, they can be held in position by any means, for example by a few turns of ribbon divided in two or three zones on the periphery of the circuit.

Each cap 56 or 57 comprises an inner rim 64 partially covering the inner cylindrical face of the inner electrical winding 26, and an outer rim 65 partially covering the outer lateral cylindrical face of the inner electrical winding 26. These edges ensure the fitting caps 56 and 57 on the inside winding, and their thickness defines the thickness of the air gap separating the inside electric winding 26 from the outside electric winding or the magnetic shunt.

In the embodiment of FIG. 4, the external contours 58 and 59 of the two caps 56 and 57 have a particular shape: thus, the external contour 58 of the cap 56 comprises an annular groove 66, and the external contour 59 of the cap 57 comprises an annular groove 67, the grooves 66 and 67 facing each other as shown in the figure.

An auxiliary magnetic core 42, consisting of a stack of magnetic sheets, of rectangular shape, curved, has an edge upper 68 engaged in the groove 66 and a lower edge 69 engaged in the groove 67. When winding the outer winding, over the caps 56 and 57, the walls of the grooves 66 and 67 tend to tighten and pinch the edges of the magnetic core 42. This results in very tight retention of the sheets, avoiding noise and vibration, and facilitating their mounting. Despite the tightening, it remains possible to slide one of the sheets forming the magnetic core 42, for subsequent adjustment of the transformer. In this embodiment, the magnetic core 42 has an open profile, in the form of an annular sector with a single air gap 47.

The external electrical winding 48, formed by radial turns, covers the intermediate electrical isolation assembly thus formed. The caps 56 and 57 form the support for the exterior electrical winding 48. By virtue of the existence of the protruding contours 58, 59, 60 and 61 against which they are supported, the internal turns of the exterior electrical winding 48 each have two opposite parts 90 and 92 bearing against the external faces of the caps 56 and 57, and two opposite parts 91 and 93 stretched between the respective protruding contours opposite one another of the caps 56 and 57. The parts tensioned 91 and 93 of turns are separated and isolated from the internal electrical winding 26 by the space 62 or 63 devoid of solid electrical insulation, which promotes the transfer of heat energy.

The external faces of the contours 58, 59, 60 and 61 of the caps 56 and 57 advantageously have a rounded cross section, as shown in FIG. 4, or FIG. 6. Thanks to this rounded section, the mean outer winding turn 48 has a reduced length, and the winding is more regular. The outer face of the caps 56 and 57 also has a special feature which makes it possible to solve the problems linked to the winding of a flat electrical conductor of large section on a toric core. The problem encountered is illustrated in FIGS. 7 and 8. By the fact that the turns of a first layer 70 are contiguous in the zone 71 opposite the central chimney 12 of the circuit, the same turns are discarded in the outer zone 72. When an upper layer of turns is wound above the lower layer 70, for example when the conductor 73 is positioned, this conductor overlaps two conductors of the lower layer 70 in the vicinity of the zone 71, but tends to be inserted between two conductors of the lower layer 70 in the vicinity of the external zone 72. The transition from the overlap to the insertion takes place in an intermediate zone , in which the conductor 73 is folded and comes to bear at two lateral points 74 and 75 on each of the conductors of the lower layer 70. These punctual lateral supports are the seat of significant pressure, producing damage to the conductor insulators .

Conventional solutions consist in multiplying the layers of insulating tape between layers of electrical winding. This results in an increase in volume, and above all a harmful thermal insulation preventing the cooling of the internal turns.

To avoid this drawback, the caps 56 and 57 comprise, on their outer flat faces, shims 75, regularly distributed in a circle in an intermediate zone between the inner contour and the outer contour of the caps. The spacers 75 have a height substantially equal to the thickness of the flat conductor, and are separated from each other by a space 76 of width greater than the width of the flat conductor forming the winding. Thus, to form the outer winding 48, a first winding layer 77 is formed by conductor turns each engaged between two successive shims. A second winding layer 78 is constituted by turns of conductor each passing over the upper face of a block, as shown in FIG. 9. Thus, as seen in FIG. 8, the block 75 avoids point contact lateral between the conductors of the lower layer 70 and the conductor 73 of the upper layer.

The caps 56 and 57 ensure the mechanical retention of the magnetic core 42. As shown in FIG. 9, the caps 56 and 57 can also ensure the maintenance of the electrostatic screens 37 and 49, arranged between the primary winding and the secondary winding of the transformer.

The annular grooves 66 and 67 ensuring the maintenance of the magnetic core 42 can be interrupted on a part of their periphery, allowing the manipulation of the sheets of the magnetic circuit 42 for their displacement by peripheral sliding. The sheets are accessible in the area of the air gap 47, an area which is not entirely covered by the external electrical circuit 48. In reality, the external electrical circuit 48 covers the entire toroid, with the exception of part of the air gap 47.

One can take advantage of the presence of caps 56 and 57 to provide, in their upper or lower surfaces, chimneys for the passage of conductors to maintain and ensure the passage of the ends of the inner windings.

In the embodiment shown in FIGS. 4 to 9, only the caps 56 and 57 are provided with shims 75. Surprisingly, it has been observed that the presence of these shims 75 considerably improves the regularity of arrangement of the turns of the external winding 48. This results in a significant improvement in the reproducibility of the electrical characteristics of the transformer thus obtained, so that it becomes almost useless to adjust these electrical characteristics, after assembly, by manipulation of the sheets of the magnetic core 42.

One can also consider using caps comprising shims 75 either between the primary winding and the secondary winding of the transformer, but between successive layers of winding, thus providing the same advantages. Wedges 75 could also be used on the magnetic circuit caps 50 and 51. The shims 75 can also be advantageously used with electrical conductors of round section.

The caps 56 and 57 between electrical windings can advantageously be pierced with lights distributed over their surfaces. Such lights, such as lights 79 and 80, formed on the portions of surfaces parallel to the conductors and which have no mechanical holding effect on these conductors, promote heat exchanges from the inside winding to the outside. , without disturbing the electrical insulation and the positioning of the conductors.

Figure 10 shows another embodiment of the device according to the present invention. In this embodiment, which relates to a toroidal transformer, but which can relate to any device comprising electrical windings wound around a toric magnetic core, the device comprises substantially the same components as in the embodiment of the figure 4, namely: a toroidal magnetic circuit 20, with insulators 50, 51, 52 and 53, the outer section of which has a rectangular shape with rounded corners; an internal electrical winding 26 is wound around the isolated magnetic circuit; rigid insulating elements are applied against two opposite surfaces of the internal electrical winding 26; an external electrical winding 48 is wound around the rigid insulating elements.

In this second embodiment, the rigid insulating elements comprise a first rigid insulating element in the form of an inner cylindrical sleeve 166, a second rigid insulating element in the form of an outer cylindrical sleeve 167, the two sleeves 166 and 167 being produced of an electrically insulating material. Each cylindrical sleeve has a height only slightly greater than the axial height of the ring formed by the internal electrical winding 26, so that the lower and upper edges of the sleeves slightly protrude below and above the winding electric interior 26, as shown in the figure. The respective upper edges 158 and 160 of the outer cylindrical sleeve 167 and the inner cylindrical sleeve 166 are separated by a space 163 promoting the transfer of heat energy from the inner electrical winding 26 to the outside; similarly, the respective lower edges 159 and 161 of the outer cylindrical sleeve 167 and the inner cylindrical sleeve 166 are separated by a space 162 promoting the transfer of heat energy from the inner electrical winding 26 to the outside.

As in the previous embodiment, the inner 166 and outer 167 sleeves can be provided with lights such as the lights 179 and 180, promoting the transfer of heat energy.

The outer face of the edges 158, 159, 160 and 161 of the cylindrical sleeves have a rounded cross section, improving the winding of the conductors, as in the previous embodiments.

In the figure, it can be seen that the edges 158, 159, 160 and 161 of the cylindrical sleeves follow the rounded shape of the edges of the internal electrical winding 26. Such a rounded shape can be produced in several ways, so as to allow the insertion of the sleeves around the internal electrical winding 26. For example, sleeves provided with a longitudinal slot can be provided, allowing their spacing or narrowing; or provision may be made to form, for example by thermoforming, the rounded parts after the sleeve has been arranged on the electrical winding, or provision may be made for sleeves in two parts, a first part engaging from the top of the internal electrical winding 26, and a second part engaging from below.

This second embodiment is also compatible with the provision of shims 75 avoiding the overlapping of the conductors of successive turns. Thus, the spacers 75 are provided on the upper edge 158 and on the lower edge 159 of the outer cylindrical sleeve 167, as shown in the figure.

It will be understood that, in the embodiments which have been shown in FIGS. 3 to 10, the rigid insulating elements such as the upper toric cap 56, the lower toric cap 57, the external cylindrical sleeve 167 and the internal cylindrical sleeve 166, are disposed between an internal electrical winding 26 and an external electrical winding 48 forming two electrically separated windings of a transformer.

The same insulation technique can however be used advantageously between two successive layers of conductors of the same electrical winding, allowing on the one hand to electrically insulate the successive layers, allowing on the other hand the transfer of heat energy to the exterior, finally allowing, for certain applications, to facilitate winding by guiding the conductors.

The present invention is not limited to the embodiments which have been explicitly described, but it includes the various variants and generalizations thereof contained in the field of claims below.

Claims (12)

1 - Device with isolated toroidal electric winding, comprising:
- a closed annular main magnetic circuit (20),
- means for isolating the magnetic circuit, defining an annular assembly with a substantially rectangular section limited by an upper surface (50) in the form of a substantially planar crown, by a lower surface (51) in the form of a substantially planar crown, by a surface cylindrical interior (53) and by a cylindrical exterior surface (52),
- at least one internal electrical winding (26) wound on the means for isolating the magnetic circuit,
- intermediate electrical isolation means surrounding the interior electrical winding,
- an external electrical winding (48) wound around the intermediate electrical insulation,
characterized in that:
- the intermediate electrical isolation means comprise a first (56, 166) and a second (57, 167) opposite rigid insulating element applied respectively directly against two opposite surfaces (28, 30; 29, 31) of the interior electrical winding (26),
- the rigid insulating elements slightly protrude on either side of the opposite surfaces against which they are applied, defining four protruding contours (58, 59, 60, 61; 158, 159, 160, 161),
- the protruding contours (58, 60; 158, 160) of the first insulating element (56, 166) are separated from the respective opposite protruding contours (59, 61; 159, 161) of the second insulating element (57, 167) by a space (62, 63; 162, 163) devoid of solid electrical insulation,
- the internal turns of the external electrical winding (48) comprise two opposite parts (90, 92; 191, 193) bearing against the external faces of the rigid insulating elements, and two opposite parts (91, 93; 190, 192) stretched between the respective protruding contours facing each other of the rigid insulating elements, the tensioned parts (91, 93; 190, 192) of the external electric winding being separated and isolated from the internal electric winding (26) by the space (62, 63; 162, 163) devoid of solid electrical insulation, which promotes the transfer of heat energy. 2 - Device according to claim 1, characterized in that:
- The first rigid insulating element is an electrically insulating upper toric cap (56) bearing against the upper flank (28) of the internal electrical winding (26), and the second rigid insulating element is an electrically insulating lower toric cap (57) insulating bearing against the lower side (30) of the internal electrical winding (26),
- each toric cap (56, 57) is limited by a circular external protruding contour (58, 59) of diameter only slightly greater than the external diameter of the ring formed by the internal electrical winding (26), and is limited by a circular internal protruding contour (60, 61) of diameter only a little less than the internal diameter of the ring formed by the internal electrical winding (26),
- The respective protruding contours of the upper cap (56) and the lower cap (57) facing each other are separated by a space (62, 63) promoting the transfer of heat energy. 3 - Device according to claim 2, characterized in that each cap (56, 57) comprises an inner rim (64) and / or outer (65) partially covering the corresponding lateral cylindrical face of the inner electrical winding (26). 4 - Device according to one of claims 2 or 3, characterized in that:
- The caps (56, 57) comprise, on their external flat faces, shims (75) distributed regularly in a circle in an intermediate zone between the outer contour (58) and the inner contour (60), the shims (75) having a height substantially equal to the thickness of the conductor forming the winding, the shims being separated from each other by a space (76) of width greater than the width of the conductor,
- A first winding layer (77) consists of conductor turns each engaged between two successive shims, a second winding layer (78) consists of conductor turns each passing over the upper face of a shim . 5 - Device according to any one of claims 2 to 5, characterized in that:
- the outer contour (58, 59) of each of the caps (56, 57) comprises an annular groove (66, 67) facing the annular groove of the other cap,
- A magnetic core (42), comprising a stack of curved sheets, is held by the caps (56, 57), the edges (68, 69) of the sheets being pinched respectively in the upper cup groove (66) and in the lower cap groove (67). 6 - Device according to claim 5, characterized in that the annular grooves (66, 67) are open over a portion of their periphery, allowing the manipulation of the sheets of the magnetic core (42) by peripheral sliding. 7 - Device according to any one of claims 2 to 6, characterized in that the caps hold, by their outline, electrostatic screens (37, 49) between inner winding (26) and outer winding (48). 8 - Device according to claim 1, characterized in that:
the first rigid insulating element is an electrically insulating inner cylindrical sleeve (166), and the second rigid insulating element is an electrically insulating outer cylindrical sleeve (167),
- each cylindrical sleeve has a height only slightly greater than the axial height of the ring formed by the internal electrical winding (26), so that the lower and upper edges of the sleeves slightly protrude above and below the internal electrical winding,
- The respective protruding edges (158, 160, 159, 161) of the inner cylindrical sleeve and the outer cylindrical sleeve are separated by a space (162, 163) promoting the transfer of heat energy. 9 - Device according to any one of claims 1 to 8, characterized in that the rigid insulating elements are provided with lights (79, 80; 179, 180) promoting the transfer of heat energy. 10 - Device according to any one of claims 1 to 9, characterized in that rigid insulating elements are arranged between an inner electrical winding (26) and an outer electrical winding (48) electrically isolated from each other for form a transformer with primary winding and secondary winding. 11 - Device according to any one of claims 1 to 10, characterized in that it comprises rigid insulating elements arranged between successive layers of the same electrical winding. 12 - Device according to any one of claims 1 to 11, characterized in that the external faces of the contours of rigid insulating elements have a rounded cross section.

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