Electrically insulated multilayer coil for electrical transformer

Abstract

The solution proposed by the invention is a multilayer coil for an electrical transformer suitable for the use of insulating fluids which are less polluting than conventional insulating fluids. The coil (1) according to the invention is characterized in that the first overhang length (L1i), and / or the second overhang length (L2i), of at least one electrically insulating layer (12i) is greater than the first overhang length (L1j), and / or respectively the second overhang length (L2j), of at least one further electrically insulating layer (12j).

Description

Electrically insulated multilayer coil for electrical transformer Technical field of the invention

[0001] The present invention relates to the technical field of electrical transformers and more particularly to multilayer coils for electrical transformers. State of the art

[0002] Electrical transformers of the type described in IEC61869-1, IEC61869-3 and IEC61869-4 are known. A transformer of this type comprises a multi-layer coil (10) such as that shown in Figure [Fig.1]. The coil (10) generally comprises an electrically conductive part (101) and an electrically insulating part (102).

[0003] The electrically conductive portion (101) comprises a plurality of electrically conductive layers. Each of the electrically conductive layers comprises a conductive wire spirally wound around an axis (A0) and extending axially from a first plane orthogonal to said axis to a second plane orthogonal to said axis. The electrically conductive layers are arranged coaxially around each other.

[0004] The electrically insulating portion (102) comprises several electrically insulating layers. Each of the electrically insulating layers is arranged between two of the electrically conductive layers so as to insulate the two electrically conductive layers from each other. In practice, each of the electrically insulating layers may be in the form of several insulating sub-layers of the same length superimposed. The electrically insulating layer comprises a first and a second overhanging zone extending axially, over a first, respectively second, overhanging length in an axial direction, beyond the first, respectively second, orthogonal plane of the longest two said electrically conductive layers. These overhanging zones are arranged so as to limit the creation of electric arcs between the electrically conductive layers at the ends of the coil (10).This overhang length is identical for all layers. Also, the overhang zones prevent the conductive wire from slipping off the reel, under the effect of the mechanical tension applied by the machine during winding.

[0005] To increase the insulation between electrically conductive layers at the ends of the coil (10), the latter is arranged in a pressure chamber into which an electrically insulating fluid is injected so as to envelop the coil. These fluids can be of the oil or gas type.

[0006] However, the most efficient fluids in terms of electrical insulation are also the most polluting. For these commonly used high-performance fluids, we speak of conventional insulating fluids. This is particularly the case for sulfur hexafluoride (SF6). Thus, it is necessary to develop solutions integrating less polluting fluids, for example example oxygen, nitrogen, carbon dioxide, fluoronitrile, fluoroketone, a mixture of fluoronitrile, or fluoroketone, with oxygen or nitrogen or carbon dioxide, a mixture of sulfur hexafluoride with a significant amount of nitrogen, etc.

[0007] However, as things stand, simply by substituting one fluid for another, the degradation of the insulation is such that electric arcs occur, in particular we speak of breakdown. On this type of transformer comprising a pressurized enclosure, the appearance of electric arcs frequently leads to the destruction of the coil.

[0008] Therefore, the invention aims to provide a multilayer coil for an electrical transformer suitable for the use of insulating fluids having a dielectric strength lower than that of sulfur hexafluoride and preferably less polluting than conventional insulating fluids. Disclosure of the invention

[0009] The solution proposed by the invention is a coil for an electrical transformer comprising: - An electrically conductive part comprising a plurality of electrically conductive layers, each of said electrically conductive layers comprising a conductive wire wound spirally around an axis and extending axially from a first plane orthogonal to said axis to a second plane orthogonal to said axis, said electrically conductive layers being arranged coaxially around each other, - An electrically insulating part comprising several electrically insulating layers, each of said electrically insulating layers being arranged between two of said electrically conductive layers so as to insulate the two said electrically conductive layers from each other, said electrically insulating layer comprising a first overflow zone and a second overflow zone extending axially, over a first overflow length, respectively second overflow length, beyond the first plane, respectively the second plane, of the longest of the two said electrically conductive layers.

[0010] This coil is remarkable in that the first overhang length, and / or the second overhang length, of at least one first electrically insulating layer is greater than the first overhang length, and / or respectively the second overhang length, of at least one other electrically insulating layer.

[0011] Thus, the creation of irregularities in the overflow length of the different electrically insulating layers makes it possible to improve the insulation's capacity to prevent the occurrence of electric arcs.

[0012] According to another advantageous characteristic of the invention making it possible to improve the capacity of the insulation to prevent the appearance of electric arcs by creating significant irregularities: - the conductive wire of each electrically conductive layer has a diameter, and - the first overflow length, or the second overflow length, of the at least one first electrically insulating layer is greater than the first overhang length, or respectively second overhang length of the second electrically insulating layer by at least twenty times the diameter of said conductive wire.

[0013] According to another advantageous characteristic of the invention making it possible to improve the capacity of the insulation to prevent the occurrence of electric arcs by optimizing the overflow lengths: - the conductive wire of each electrically conductive layer has a diameter, and - the first overhang length and the second overhang length of each electrically insulating layer are between forty and three hundred and twenty times the diameter of said conductive wire.

[0014] According to yet another advantageous characteristic of the invention making it possible to improve the capacity of the insulation to prevent the appearance of electric arcs by generating a notched profile: - the conductive wire of each electrically conductive layer has a diameter, and - the electrically insulating layers are divided into a group with short overflows and a group with long overflows, - the first overhang length and the second overhang length of the electrically insulating layers of said short overhang group are between forty and one hundred times the diameter of said conductive wire, - the first overhang length and the second overhang length of the electrically insulating layers of said long overhang group are between one hundred and twenty and three hundred and twenty times the diameter of said conductive wire.

[0015] According to yet another advantageous characteristic of the invention making it possible to improve the capacity of the insulation to prevent the occurrence of electric arcs by optimizing the width and thickness of the notches: - the short overflow group is composed of short overflow subgroups of two to four consecutive electrically insulating layers, - the long overflow group is composed of long overflow subgroups of two to four consecutive electrically insulating layers, - the insulating part being formed by an alternation between short overflow subgroups and long overflow subgroups.

[0016] According to yet another advantageous characteristic of the invention making it possible to improve the capacity of the insulation to prevent the appearance of electric arcs by generating an asymmetrical notched profile at the two ends of the coil: - the conductive wire of each electrically conductive layer has a diameter, and - the electrically insulating layers are divided into a group with a first short overflow and a second long overflow, and a group with a first long overflow and a second short overflow, - the first overflow length of the electrically insulating layers of the group with first short overflow and second long overflow, and the second length of overflow of the electrically insulating layers of the group with first long overflow and second short overflow are between forty and one hundred times the diameter of said conductive wire, - the second overhang length of the electrically insulating layers of the group with first short overhang and second long overhang, and the first overhang length of the electrically insulating layers of the group with first long overhang and second short overhang are between one hundred and twenty and three hundred and twenty times the diameter of the conductive wire.

[0017] According to yet another advantageous characteristic of the invention making it possible to improve the capacity of the insulation to prevent the occurrence of electric arcs by optimizing the width and thickness of the notches: - the group with first short overflow and second long overflow is composed of subgroups with first short overflow and second long overflow of two to four consecutive electrically insulating layers, - the group with first long overflow and second short overflow is composed of subgroups with first long overflow and second short overflow of two to four consecutive electrically insulating layers, - the insulating part being formed by an alternation between subgroups with first short overflow and second long overflow and subgroups with first long overflow and second short overflow.

[0018] According to yet another advantageous characteristic of the invention making it possible to improve the capacity of the insulation to prevent the occurrence of electric arcs by generating a profile in which the variation in length is more progressive, by successively selecting the electrically insulating layers radially from the inside to the outside, the first overhang length, and / or the second overhang length of an electrically insulating layer increases, or decreases, relative to the first overhang length, and / or respectively the second overhang length of the preceding electrically insulating layer up to a maximum length, or respectively a minimum length, then decreases, or respectively increases, up to said minimum length, or respectively said maximum length.

[0019] According to yet another advantageous characteristic of the invention making it possible to improve the capacity of the insulation to prevent the occurrence of electric arcs by optimizing the minimum and maximum lengths, the minimum length is between forty and one hundred times the diameter of the conductive wire and the maximum length is between one hundred and twenty and three hundred and twenty times the diameter of the conductive wire.

[0020] According to yet another advantageous characteristic of the invention making it possible to improve the capacity of the insulation to prevent the occurrence of electric arcs, the first overflow length, and / or the second overflow length, increase or decrease according to a sinusoidal function.

[0021] Another aspect of the invention relates to an electrical transformer comprising: - A speaker, - At least one coil arranged inside the enclosure, and - An electrically insulating fluid arranged inside the enclosure and enveloping said at least one coil. This transformer is remarkable in that said at least one coil is a coil as defined above.

[0022] Thus, in such a transformer, the creation of irregularities in the overflow length of the different electrically insulating layers makes it possible to improve the insulation's ability to prevent the occurrence of electric arcs. Description of figures

[0023] Other features and advantages of the invention will emerge from reading the description given below of particular embodiments of the invention, given for informational but non-limiting purposes, with reference to the appended drawings in which:

[0024] [Fig.1] is a schematic sectional view of the prior art coil;

[0025] [Fig.2] is a schematic sectional view of a first example of embodiment of the coil which is the subject of the invention with a symmetrical crenellated insulation profile;

[0026] [Fig.3] is a schematic view of the detail DI of the first embodiment shown in figure [Fig.2];

[0027] [Fig.4] is a schematic view of detail D2 of the first embodiment shown in figure [Fig.2];

[0028] [Fig.5] is a schematic sectional view of a second embodiment of the coil which is the subject of the invention with an asymmetrical crenellated insulation profile;

[0029] [Fig.6] is a schematic sectional view of a third example embodiment of the coil which is the subject of the invention with a symmetrical sinusoidal insulation profile;

[0030] [Fig.7] is a schematic sectional view of a fourth embodiment of the coil which is the subject of the invention with an insulation profile with a constant short overhang length;

[0031] [Fig.8] is a schematic sectional view of a fifth embodiment of the coil which is the subject of the invention with a cylindrical conductive profile and a symmetrical crenellated insulation profile;

[0032] [Fig.9] is a schematic sectional view of a sixth embodiment of the coil which is the subject of the invention with a parabolic conductive profile and a symmetrical crenellated insulation profile.

[0033] Figures [Fig.1 ] to [Fig.9] do not reflect the actual dimensions of the components. The dimensions of some elements may have been enlarged or reduced in order to facilitate the reader's understanding. In particular, the ratio of overhang length to diameter of the conductive wire shown in the figures does not reflect reality. Detailed description

[0034] The invention relates to a coil (1) for an electrical transformer. The electrical transformer may be a measuring, power, or other transformer. The electrical transformer may be single-phase or three-phase.

[0035] The coil (1) comprises an electrically conductive part (11). The latter comprises several electrically conductive layers (11a, 11b, 11c, 11d, 11f, etc.). In the remainder of the description, and for the sake of simplification, we will speak of an electrically conductive layer (11i) to designate any electrically conductive layer among the set of electrically conductive layers. "i" is a variable that can take a letter of the alphabet as a value so as to allow the distinction of the electrically conductive layers between them as in the example of figures [Fig.3] and [Fig.4] where: - i = a for the electrically conductive layer (1 la) closest to the axis, - i = b for the electrically conductive layer (11b) next to the axis (A), - i = c for the electrically conductive layer (11c) next to the axis (A), - and so on. Alternatively, in the remainder of the description the variables "j" or "k" can be used in a similar way.

[0036] In practice, the coil (1) may comprise between 50 and 150 electrically conductive layers (1 li). Each of said electrically conductive layers (1 li) comprises a conductive wire (111). The conductive wire (111) is preferably an enameled conductive wire. The conductive wire (111) preferably comprises a core made of copper, but may be made of aluminum or any other conductive material suitable to a person skilled in the art. The conductive wire (111) of each electrically conductive layer (1 li) may have a diameter (D). The latter may be between 0.125 mm and 0.3 mm. The conductive wire (111) is wound in a spiral around an axis (A) and extending axially from a first plane (Pli) orthogonal to the axis (A) to a second plane (P2i) orthogonal to the axis (A). The electrically conductive layers (1 li) are arranged coaxially around each other.

[0037] Each turn of conductive wire (111) in the electrically conductive layer (1 li) is called a turn. For each electrically conductive layer (1 li), the number of turns can be between 1 and 2500. In certain embodiments such as those shown in figures [Fig.2] to [Fig.6] and [Fig.9], the number of turns can decrease from the conductive layer (1 la) closest to the axis to the conductive layer furthest from the axis. The number of turns can decrease linearly as in the exemplary embodiments shown in figures [Fig.2] to [Fig.6]. This type of coil is generally called a "trapezoidal coil". The number of turns can decrease non-linearly, for example according to a parabola as in the exemplary embodiment shown in figure [Fig.9]. This latter type of coil is generally called a "parabolic coil". In other embodiments, and in particular in the exemplary embodiment of the figure [Fig.8], the number of turns may be identical for all electrically conductive layers (1 li). This type of coil is generally called a "cylindrical coil". In still other embodiments. not shown, the number of turns can decrease by one to five turns every three to ten electrically conductive layers (1 li).

[0038] The coil (1) also comprises an electrically insulating part (12). The electrically insulating part (12) comprises several electrically insulating layers (12i). In the remainder of the description, and for the sake of simplification, we will speak of an electrically insulating layer (12i) to designate any electrically insulating layer among the set of electrically insulating layers. "i" is a variable that can take a letter of the alphabet as a value so as to allow the distinction of the electrically insulating layers from one another as in the example of figures [Fig.3] and [Fig.4] where: - i = a for the electrically insulating layer (12a) closest to the axis, - i = b for the electrically insulating layer (12b) next to the axis (A), - i = c for the electrically insulating layer (12c) next to the axis (A), - and so on. Alternatively, in the remainder of the description the variables "j" or "k" can be used in a similar way.

[0039] Each electrically insulating layer (12i) comprises one or more electrically insulating materials of the polyester film type partially covered on both sides with glue, or others. Preferably, the insulating material has a dielectric strength greater than 50 kV / mm. Each of the electrically insulating layers (12i) is arranged between two of the electrically conductive layers (11i) so as to insulate the two said electrically conductive layers from each other. In practice, an electrically insulating layer (12i) can be produced by winding a strip of electrically insulating material around an electrically conductive layer. In this case, the strip of electrically insulating material can have a width of between 50 mm and 350 mm and a thickness of between 20 μm and 50 μm. The winding can be carried out edge to edge or with an overlap.The electrically insulating layer (12i) may comprise several superimposed windings of the same insulating material or of different insulating materials. Advantageously, the electrically insulating layer (12i) comprises from 2 to 4 superimposed windings.

[0040] Each electrically insulating layer (12i) comprises and is extended by a first overflow zone extending, axially, over a first overflow length (L 1 i), beyond the first orthogonal plane (Pli) of the longest of the two adjoining electrically conductive layers (1 li).

[0041] It can also be seen in the figures and for all of the embodiments which will be described that the electrically conductive layers (1 li) overlap at least partially axially.

[0042] The electrically insulating layers (12i) are generally cylindrical in shape and said electrically insulating layers (12i) are arranged coaxially around each other and overlap at least partially axially.

[0043] For example, referring to figure [Fig.3], the electrically insulating layer (12a) comprises a first overflow zone extending axially over a first overflow length (Lia), beyond the first orthogonal plane (P la) of the longest electrically conductive layer (l ia) of the two adjoining electrically conductive layers (l ia, 11b). The same applies: - For the electrically insulating layer (12b) having a first overflow length (Llb) relative to the first orthogonal plane (Pib), - For the electrically insulating layer (12c) having a first overflow length (Lie) relative to the first orthogonal plane (Pic), - For the electrically insulating layer (12d) having a first overflow length (Lld) relative to the first orthogonal plane (Pld), - For the electrically insulating layer (12e) having a first overflow length (Lie) relative to the first orthogonal plane (Pie), - For the electrically insulating layer (12f) having a first overflow length (L If) relative to the first orthogonal plane (Pif), - and so on.

[0044] Advantageously, the first overhang length (Lli) is greater than forty times the diameter (D) of the conductive wire. Preferably, the first overhang length (Lli) is greater than seventy times the diameter (D) of the conductive wire.

[0045] Each electrically insulating layer (12i) comprises a second overflow zone extending, axially, over a second overflow length (L2i), beyond the second orthogonal plane (P2i) of the longest of the two adjoining electrically conductive layers (1 li).

[0046] For example, referring to figure [Fig.4], the electrically insulating layer (12a) comprises a second overflow zone extending, axially, over a second overflow length (L2a), beyond the second orthogonal plane (P2a) of the longest electrically conductive layer (l ia) of the two said electrically conductive layers (l ia, 11b). The same applies: - For the electrically insulating layer (12b) having a second overhang length (L2b) relative to the second orthogonal plane (P2b), - For the electrically insulating layer (12c) having a second overhang length (L2c) relative to the second orthogonal plane (P2c), - For the electrically insulating layer (12d) having a second overhang length (L2d) relative to the second orthogonal plane (P2d), - For the electrically insulating layer (12e) having a second overflow length (L2e) relative to the second orthogonal plane (P2e), - For the electrically insulating layer (12f) having a first overflow length (L2f) relative to the first orthogonal plane (P2f), - and so on.

[0047] Advantageously, the second overhang length (L2i) is greater than forty times the diameter (D) of the conductive wire. Preferably, the second overhang length (L2i) is greater than seventy times the diameter (D) of the conductive wire.

[0048] Referring to figures [Fig.2], [Fig.5] to [Fig.9], the electrical transformer is remarkable in that the first overflow length (Llj), and / or the second overflow length (L2j), of at least one first electrically insulating layer (12j) is greater than the overflow length (Llk), and / or the second overflow length (L2k), of at least one other electrically insulating layer (12k).

[0049] In a manufacturing process based on cutting electrically insulating layers initially having the same dimensions, it can be noted that the technical effect of the invention is obtained without additional cost, the best breakdown resistance being obtained without adding material for the electrically insulating layers.

[0050] The first overhang length (Llj), or the second overhang length (L2j), of the at least one first electrically insulating layer (12j) is advantageously greater than the first overhang length (Llk), or respectively second overhang length (L2k) of the second electrically insulating layer (12k), by at least twenty times the diameter (D) of the conductive wire (111), cleverly, by at least fifty times the diameter (D) of the conductive wire (111), and preferentially, by at least one hundred times the diameter (D) of the conductive wire (111).

[0051] Advantageously, the first overflow length and the second overflow length (Lli, L2i) of each electrically insulating layer (12i) is between forty and three hundred and twenty times the diameter (D) of the conductive wire (111).

[0052] Each electrically insulating layer (12i) may comprise: - either two long overflows, - either two short overflows, - either a long overflow and a short overflow.

[0053] Short overhang is understood to mean that the overhang length (Lli, L2i) of the electrically insulating layer is between forty and one hundred times the diameter (D) of the conductive wire (111). The short overhangs may have different lengths as in the exemplary embodiments shown in figures [Fig.1] to [Fig.6], [Fig.8] and [Fig.9]. In alternative embodiments, and as in the exemplary embodiment shown in figure [Fig.7], the short overhangs may all have the same length. Thus, it is for example possible to keep the conventional overhangs as short overhangs and to lengthen certain overhangs to make them long overhangs. In other alternative embodiments not shown, certain short overhangs may have the same length, others not.

[0054] Long overhang is understood to mean that the overhang length (Lli, L2i) of the electrically insulating layer is between one hundred and twenty and three hundred and twenty times the diameter (D) of the conductive wire (111). The long overhangs may have different lengths as in the embodiments shown in figures [Fig. l] to [Fig.6], [Fig.8] and [Fig.9]. In embodiment variants not shown, the long overhangs may all have the same length. In other embodiment variants not shown, some short overhangs may have the same length, others not.

[0055] In some embodiments, the innermost electrically insulating layer (12a) of the coil (1) may have two short overhangs. In other embodiments, the innermost electrically insulating layer (12a) of the coil (1) may have two long overhangs. In still other embodiments, the innermost electrically insulating layer (12a) of the coil (1) may have one long overhang and one short overhang.

[0056] In a first embodiment, the electrically insulating layers (12i) are divided into a group with short overflows (122) and a group with long overflows (121). That is to say that: - The first overhang length (Llj) and the second overhang length (L2j) of the electrically insulating layers (12j) of the short overhang group (122) is between forty and one hundred times the diameter (D) of the conductive wire (111), and - The first overflow length (Llk) and the second overflow length (L2k) of the electrically insulating layers (12k) of the long overflow group (121) is between one hundred and twenty and three hundred and twenty times the diameter (D) of the conductive wire (H l).

[0057] Generally, the short overhang group (122) may be composed of short overhang subgroups of two to four consecutive electrically insulating layers (12j). Also, the long overhang group (121) may be composed of long overhang subgroups of two to four consecutive electrically insulating layers (12k). Thus, the insulating part (12) is formed by alternating short overhang subgroups and long overhang subgroups.

[0058] In the embodiment shown in figure [Fig.2], the short overflow group (122) is composed of: - Three short overflow subgroups of three consecutive electrically insulating layers (12j), and - A short-overflow subgroup of two consecutive electrically insulating layers (12j).

[0059] The long overflow group (121) is composed of three long overflow subgroups of three consecutive electrically insulating layers (12k).

[0060] In a second embodiment, the electrically insulating layers (12i) are divided into a group with a first short overflow and a second long overflow (123), and a group with a first long overflow and a second short overflow (124). That is to say that: For the electrically insulating layers (12j) of the group with first short overflow and second long overflow (123): o The first overflow length (Llj) is between forty and one hundred times the diameter (D) of the conductive wire (111), o The second overflow length (L2j) is between one hundred and twenty and three hundred and twenty times the diameter (D) of the conductive wire (111), For electrically insulating layers (12k) of the first overflow group long and second short overflow (124): o The first overflow length (Llk) is between one hundred and twenty and three hundred and twenty times the diameter (D) of the conductive wire (111), o The second overflow length (L2k) is between forty and one hundred times the diameter (D) of the conductive wire (111).

[0061] Generally, the first short overflow and second long overflow group (123) is composed of first short overflow and second long overflow subgroups of two to four consecutive electrically insulating layers (12j). Also, the first long overflow and second short overflow group (124) is composed of first long overflow and second short overflow subgroups of two to four consecutive electrically insulating layers (12k). Thus, the insulating part (12) is formed by alternating first short overflow and second long overflow subgroups and first long overflow and second short overflow subgroups.

[0062] In the embodiment shown in figure [Fig.5], the group with short overflow and second long overflow (123) is composed of: - Three subgroups with short overflow and second long overflow of each three consecutive electrically insulating layers (12i), and - A subgroup with short overflow and second long overflow of two consecutive electrically insulating layers (12i).

[0063] The group with first long overflow and second short overflow (124) is composed of three subgroups with first long overflow and second short overflow, each with three consecutive electrically insulating layers (12j).

[0064] In a third embodiment, the overflow lengths gradually increase or decrease.

[0065] For example, by successively selecting the electrically insulating layers radially from the inside to the outside, the first overhang length (Llj) of an electrically insulating layer (12j) increases, or decreases, relative to the first overhang length (Llk) of the preceding electrically insulating layer (12k) up to a maximum length, or respectively a minimum length, then decreases, or respectively increases, up to the minimum length, or respectively the maximum length.

[0066] Alternatively to, or in combination with, the preceding paragraph, the second overflow length (L2j) of an electrically insulating layer (12j) increases, or decreases, relative to the second overflow length (L2k) of the preceding electrically insulating layer (12k) up to a maximum length, or respectively a minimum length, then decreases, or respectively increases, up to the minimum length, or respectively the maximum length.

[0067] Advantageously, the minimum length is between forty and one hundred times the diameter of the conductive wire. Also advantageously, the maximum length is between one hundred and twenty and three hundred and twenty times the diameter of the conductive wire.

[0068] Cleverly, and as in the example embodiment shown in figure [Fig.6], the first overflow length (Lli), and / or the second overflow length (L2i), increase or decrease according to a sinusoidal function (S).

[0069] Another aspect of the invention relates to an electrical transformer. This electrical transformer may be a measuring transformer intended to supply measuring devices, meters, relays and other similar devices. In particular, this transformer may be a voltage transformer. This transformer may also be a power transformer. The electrical transformer may be single-phase or three-phase.

[0070] The electrical transformer comprises an enclosure. This enclosure is preferably metallic, but can also be made of any material suitable to a person skilled in the art. The enclosure preferably has a cylindrical shape, but can also be of any shape suitable to a person skilled in the art.

[0071] The electrical transformer also comprises at least one coil (1) according to the invention. The coil (1) is arranged inside the enclosure. When the electrical transformer is single-phase, said transformer comprises a single coil (1) arranged inside the enclosure. When the electrical transformer is three-phase, said transformer comprises three coils (1) arranged inside the enclosure.

[0072] The transformer also comprises an electrically insulating fluid arranged inside the enclosure and surrounding the coil (1). This electrically insulating fluid may be of the oil type such as those described in the IEC60296 standard, insulating liquid such as those described in the IEC60867 standard, sulfur hexafluoride (SF6), or any other electrically insulating fluid suitable to those skilled in the art. Preferably, and in order to limit the risks of pollution linked to possible leaks from the enclosure, the fluid used is of the oxygen, nitrogen, carbon dioxide, fluoronitrile, fluoroketone, mixture of fluoronitrile or fluoroketone with oxygen or nitrogen or carbon dioxide, or even a mixture of sulfur hexafluoride with a significant quantity of nitrogen, etc. type. In practice, the insulating fluid has a dielectric strength greater than 2 kV / mm. The fluid may be arranged under pressure inside the enclosure.In particular, the fluid pressure can be between 3.5 bar rel and 6.3 bar rel.

Claims

Claims Coil (1) for an electrical transformer comprising: - an electrically conductive part (11) comprising several electrically conductive layers (1 li), each of said electrically conductive layers comprising a conductive wire (111) wound in a spiral around an axis (A) and extending axially from a first plane (Pli) orthogonal to said axis to a second plane (P2i) orthogonal to said axis, said electrically conductive layers being arranged coaxially around each other, - an electrically insulating part (12) comprising several electrically insulating layers (12i), each of said electrically insulating layers being arranged between two of said electrically conductive layers so as to insulate the two said electrically conductive layers from each other, said electrically insulating layer comprising a first overflow zone and a second overflow zone extending axially, over a first overflow length (Lli), respectively second overflow length (L2i), beyond the first plane (Pli), respectively second plane (P2i), of the longest of the two said electrically conductive layers, characterized in that the first overflow length (Llj), and / or the second overflow length (L2j), of at least one first electrically insulating layer (12j) is greater than the first overhang length (Llk), and / or respectively the second overhang length (L2k), of at least one other electrically insulating layer (12k). Coil according to claim 1 characterized in that said electrically conductive layers overlap at least partially axially. Coil according to claim 1 or 2, characterized in that the electrically insulating layers (12i) are of generally cylindrical shape and that said electrically insulating layers are arranged coaxially around each other and overlap at least partially axially. Coil according to any one of claims 1 to 3, characterized in that said electrically insulating layer is extended by a first overhang zone and by a second overhang zone extending axially Coil according to any one of claims 1 to 4, characterized in that: - the conductive wire (111) of each electrically conductive layer (1 li) has a diameter (D), and - the first overhang length (Llj), or the second overhang length (L2j), of the at least one first electrically insulating layer (12j) is greater than the first overhang length (Llk), or respectively second overhang length (L2k) of the second electrically insulating layer (12k) by at least twenty times the diameter (D) of said conductive wire. Coil according to one of the preceding claims, characterized in that: - the conductive wire (111) of each electrically conductive layer (1 li) comprises a diameter (D), and - the first overhang length (Lli) and the second overhang length (L2i) of each electrically insulating layer (12i) are between forty and three hundred and twenty times the diameter (D) of said conductive wire.

7. Coil according to any one of the preceding claims, characterized in that: - the conductive wire (111) of each electrically conductive layer (1 li) has a diameter (D), and - the electrically insulating layers (12i) are divided into a group with short overflows (122) and a group with long overflows (121), - the first overhang length (Llj) and the second overhang length (L2j) of the electrically insulating layers (12j) of said short overhang group are between forty and one hundred times the diameter (D) of said conductive wire, - the first overhang length (Llk) and the second overhang length (L2k) of the electrically insulating layers (12k) of said long overhang group are between one hundred and twenty and three hundred and twenty times the diameter (D) of said conductive wire.

8. Coil according to claim 7 characterized in that: - the short overflow group (122) is composed of short overflow subgroups of two to four consecutive electrically insulating layers (12j), - the long overflow group (121) is composed of long overflow subgroups of two to four consecutive electrically insulating layers (12k), - the insulating part (12) being formed by an alternation between short overflow subgroups and long overflow subgroups.

9. Coil according to any one of claims 1 to 6, characterized in that: - the conductive wire (111) of each electrically conductive layer (1 li) has a diameter (D), and - the electrically insulating layers (12i) are divided into a group with first short overflow and second long overflow (123), and a group with first long overflow and second short overflow (124), - the first overhang length (Llj) of the electrically insulating layers (12j) of the group with first short overhang and second long overhang (123), and the second overhang length (L2k) of the electrically insulating layers (12k) of the group with first long overhang and second short overhang (124) are between forty and one hundred times the diameter (D) of said conductive wire, - the second overhang length (L2j) of the electrically insulating layers (12j) of the group with first short overhang and second long overhang (123), and the first overhang length (Llk) of the electrically insulating layers (12k) of the group with first long overhang and second short overhang (124) are between one hundred and twenty and three hundred and twenty times the diameter of the conductive wire.

10. Coil according to claim 7 characterized in that: - the group with first short overflow and second long overflow (123) is composed of subgroups with first short overflow and second long overflow of two to four consecutive electrically insulating layers (12j), - the group with first long overflow and second short overflow (124) is composed of subgroups with first long overflow and second short overflow of two to four consecutive electrically insulating layers (12k), - the insulating part being formed by an alternation between subgroups with first short overhang and second long overhang and subgroups with first long overhang and second short overhang. Coil according to any one of the preceding claims, characterized in that, by successively selecting the electrically insulating layers (12i) radially from the inside to the outside, the first overhang length (Lli), and / or the second overhang length (L2i) of an electrically insulating layer (L2i) increases, or decreases, relative to the first overhang length (Llj), and / or respectively the second overhang length (L2j) of the preceding electrically insulating layer (12j) up to a maximum length, or respectively a minimum length, then decreases, or respectively increases, up to said minimum length, or respectively said maximum length.Coil according to claim 11 characterized in that the minimum length is between forty and one hundred times the diameter of the conductive wire and the maximum length is between one hundred and twenty and three hundred and twenty times the diameter of the conductive wire. Coil according to one of claims 11 or 12 characterized in that the first overflow length (Lli), and / or the second overflow length (L2i), increase or decrease according to a sinusoidal function (S). Electrical transformer comprising:. - A speaker, - At least one coil (1) arranged inside the enclosure, and - An electrically insulating fluid arranged inside the enclosure and enveloping said at least one coil, characterized in that said at least one coil is a coil according to any one of the preceding claims.

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