GALVANIC INSULATION TRANSFORMER

Abstract

The galvanic isolation transformer (100) comprises: - a magnetic core (102); and - a primary winding (112; 112A-C) and a secondary winding (114; 114A-C), wound around the magnetic core (102) so as to be magnetically coupled to each other. The magnetic core (102) is in two parts (1021, 1022), separated from each other, the primary winding (112) being wound around the first part (1021) and the secondary winding (114) being wound around the second part (1022). Figure for the abbreviation: Fig. 1

Description

Title of the invention: GALVANIC INSULATION TRANSFORMER Technical field of the invention

[0001] The present invention relates to a galvanic isolation transformer, and an aircraft comprising such a galvanic isolation transformer.

[0002] The present invention finds application particularly in the field of electrical power conversion, and more specifically in aircraft, both for electrical generation in an onboard network and for electric propulsion. Technological background

[0003] Climate change is a major concern for many legislative and regulatory bodies worldwide. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by various states. In particular, an ambitious standard applies to both new types of aircraft and those currently in operation, requiring the implementation of technological solutions to bring them into compliance with current regulations. Civil aviation has been actively working for several years now to contribute to the fight against climate change.

[0004] Technological research efforts have already led to very significant improvements in the environmental performance of aircraft. The Applicant takes into account the factors impacting all phases of design and development in order to obtain aeronautical components and products that are less energy-intensive, more environmentally friendly, and whose integration and use in civil aviation have moderate environmental impacts, with the aim of improving the energy efficiency of aircraft.

[0005] Consequently, the Applicant is constantly working to reduce its climate impact by using methods and operating virtuous development and manufacturing processes that minimize greenhouse gas emissions to the minimum possible in order to reduce the environmental footprint of its activity.

[0006] This sustained research and development work focuses on new generations of aircraft engines, the weight reduction of aircraft, in particular through the materials used and lighter on-board equipment, the development of the use of electrical technologies to provide propulsion, and, as essential complements to technological progress, aviation biofuels.

[0007] Galvanic isolation of electrical networks can be ensured by a low-frequency transformer or a high-frequency transformer. The use of galvanically isolated transformers makes it possible to ensure segregation between the two sides of the transformer, generally called "primary" and "secondary".

[0008] With the concept of the more electric aircraft, new power sources and loads have emerged. Fault propagation between these is not permitted. This requirement for non-propagation of faults necessitates a redesigned dimensioning and engineering of galvanically isolated transformers.

[0009] As is known in itself, a galvanic isolation transformer comprises a magnetic core (also called a "magnetic body") and at least two windings, for example of copper or aluminum, forming respectively a primary winding and a secondary winding of the galvanic isolation transformer.

[0010] To ensure minimal galvanic isolation, the turns of the primary and secondary windings are electrically insulated from each other using a sheath of electrically insulating material.

[0011] Thus, a galvanic isolation transformer comprising: is known from the prior art - a magnetic core; and - a primary winding and a secondary winding, wound around the magnetic core so as to be magnetically coupled to each other.

[0012] In such a galvanically isolated transformer, the primary and secondary windings are often superimposed, so that the primary and secondary windings are always close to each other, which always represents a risk of galvanic isolation failure. Indeed, in the event of a problem with one of the windings, such as a short circuit, the melting of the winding and the insulation can lead to electrical contact between the windings via the magnetic core, thus breaking the galvanic isolation.

[0013] This problem persists even when the magnetic core is made of ferrite, because this material does not necessarily guarantee adequate insulation against the high voltages required.

[0014] To this end, the invention is the result of technological research aimed at significantly improving aircraft performance and, in this sense, contributes to reducing the environmental impact of aircraft. Summary of the invention

[0015] To this end, a galvanic isolation transformer is proposed comprising: - a magnetic core; and - a primary winding and a secondary winding, wound around the magnetic core so as to be magnetically coupled to each other; characterized in that the magnetic core is in two parts, separated from each other, the primary winding being wound around the first part and the secondary winding being wound around the second part.

[0016] The invention thus proposes to physically separate the primary and secondary windings of the transformer (the latter being traditionally coaxial), but also to divide the magnetic circuit into two parts so as to have two physically separate sectors, one for the primary and the other for the secondary.

[0017] Thus, it is possible to minimize, or even guarantee, the non-propagation of electrical faults from the primary winding to the secondary winding. In particular, in the presence of a fault in, for example, the insulation between the primary and the core, an electrical contact could be established between the defective winding and the magnetic core. However, this fault will not be able to propagate to the secondary of the transformer. For such propagation to occur, there would have to be a fault not only in the insulation between the secondary and the core but also between the two parts of the core. Thus, the invention tolerates a double fault, which is essential in the field of aeronautics.

[0018] Furthermore, the physical separation of the windings according to the invention can provide one or more of the following advantages: - reduction of parasitic capacitances between primary and secondary; thermal improvement: since the two windings are not concentric, it is easier to dissipate heat (something complicated when the windings are concentric, the hot spot being located between the primary and secondary windings); - the leakage inductance provided by the physical separation of the windings can be used to improve harmonic filtering.

[0019] It will be appreciated that the fact that the windings are next to each other simplifies their cooling, since it is possible to provide a cooling system (air, forced air or cold plate) against each of the windings, unlike the cases where the windings are superimposed (one surrounded by the other) or intercalated (the turns of one alternating with the turns of the other).

[0020] The invention may further include one or more of the following optional features, according to any technically possible combination.

[0021] Preferably, the first and second parts of the magnetic core are separated by air and / or an electrically insulating material, for example one of: Kapton, Nomex, Mylar, Teflon, Mica, Polypropylene.

[0022] Preferably also, the magnetic core comprises a straight leg having an air gap, the primary winding being wound around the straight leg on one side of the air gap and the secondary winding being wound around the right leg on the other side of the air gap.

[0023] Preferably also, the galvanic isolation transformer further comprises an electrical insulating screen passing through the air gap.

[0024] Preferably also, the galvanic isolation transformer further comprises an electrically conductive screen interposed between the two parts of the magnetic core.

[0025] Preferably also, the electrically conductive screen has eddy current limiting slots.

[0026] An aircraft comprising a galvanic isolation transformer according to the invention is also proposed. Brief description of the figures

[0027] The invention will be better understood with the aid of the following description, given solely by way of example and made with reference to the accompanying drawings in which: - [Fig. 1] is a cross-sectional view of a first galvanic isolation transformer according to the invention, - Figure [Fig. 2] is a cross-sectional view of a second galvanic isolation transformer according to the invention, - Figure 3 is a cross-sectional view of a third galvanic isolation transformer according to the invention. - Figure 4 is a perspective view of a fourth galvanic isolation transformer according to the invention. - [Fig. 5] is a front view of an electrically conductive screen of the fourth galvanic isolation transformer, and - [Fig.6] is a cross-sectional view of a fourth galvanic isolation transformer according to the invention. Detailed description of the invention

[0028] With reference to [Fig.1], a first galvanic isolation transformer 100 according to the invention will now be described.

[0029] The galvanic isolation transformer 100 comprises a magnetic core 102. The magnetic core 102 is in two parts 102i, 1022, separated from each other. For example, as in the illustrated example, the magnetic core 102 has two straight legs 104, 106 and two cross members 108, 110 connecting the ends of the two straight legs 104, 106. Each of the straight legs 104, 106 has an air gap 104E, 106E. The first part 102i of the magnetic core 102 then extends from the air gap 104E to the other 106E through the first cross member 108, while the second part 1022 of the magnetic core 102 extends from the air gap 104E to the other 106E through the second cross member 110.

[0030] The galvanic isolation transformer 100 further comprises a primary winding 112 and a secondary winding 114. Generally, either of the two windings can be designated as "primary," the other being designated as "secondary." Each of the primary winding 112 and the secondary winding 114 comprises, for example, an electrical cable with a central conductor 116 surrounded by an insulating sheath 118.

[0031] The primary winding 112 and the secondary winding 114 are wound around the magnetic core 102 so as to be magnetically coupled to each other. More precisely, the primary winding 112 and the secondary winding 114 are wound side by side along the magnetic core 102, the primary winding 112 being wound around the first portion 102i of the magnetic core 102 and the secondary winding 114 being wound around the second portion 1022 of the magnetic core 102. To enhance the magnetic coupling, the primary winding 112 and the secondary winding 114 are preferably close to each other, for example separated from each other by a distance less than the breakdown distance in air. For example, this distance between windings 112, 114 is less than or equal to 5 millimeters, preferably less than or equal to 1 millimeter.

[0032] For example, as in the illustrated example, the primary winding 112 is wound around the right leg 104 on one side of the air gap 104E of the latter and the secondary winding 114 is wound around the right leg 104 on the other side of the air gap 104E of the latter.

[0033] The air gaps 104E, 106E may remain filled with air, or, as in the illustrated example, contain an electrically insulating material, in particular a solid one. The electrically insulating material, having, for example, an electrical resistance greater than 108 Qm, comprises, for example, one of the following: a polyimide film (for example, Kapton (registered trademark)), Nomex (registered trademark), or a polyethylene terephthalate film (for example, Mylar (registered trademark)). For example, as in the illustrated example, the galvanic isolation transformer 100 further comprises an electrically insulating screen 116 passing through the air gap 104E, as well as through the air gap 106E. Alternatively, two electrically insulating screens could be provided, one passing through the air gap 104E, and the other passing through the air gap 106E.

[0034] With reference to [Fig.2], a second galvanic isolation transformer 200 according to the invention will now be described.

[0035] The second galvanic isolation transformer 200 is identical to the first galvanic isolation transformer 100, except that, instead of the electrical insulating screen 116, an electrically conductive screen 202 is provided, having for example a conductivity greater than 104 S / m, surrounded by two insulating screens. electrical 204, 206 (one of which may be omitted). The electrically conductive screen 202 thus forms an electrostatic screen to enhance galvanic isolation. Preferably, the electrically conductive screen 202 is connected to an electrical ground to prevent a direct flash between the primary winding 116 and the secondary winding 118. Alternatively, a separate electrically conductive screen (covered with one or two electrically insulating screens) could be provided for each air gap 104E, 106e.

[0036] With reference to [Fig. 3], a third galvanic isolation transformer 300 according to the invention will now be described. The third galvanic isolation transformer 300 is three-phase.

[0037] Thus, the third galvanic isolation transformer 300 is identical to the first galvanic isolation transformer 100, except that the magnetic core 102 has several straight legs, specifically three in the illustrated example, labeled 302A-C, each with an air gap 302AE, 302BE, 302CE. The third galvanic isolation transformer 300 then comprises, around each leg 302A-C, a primary winding 112A-C and a secondary winding 114A-C wound around each other as in [Fig. 1]. All the primary windings 112A-C are wound around the first part 102i of the magnetic core 102, while all the secondary windings 118A-C are wound around the second part 1022 of the magnetic core 102.

[0038] The third galvanic isolation transformer 300 further comprises an electrical insulating screen 304 passing through all the air gaps 302AE, 302BE, 302CE. Alternatively, an electrical insulating screen could be provided for each air gap 302Ae, 302Be, 302Ce.

[0039] With reference to [Fig.4], a fourth galvanic isolation transformer 400 according to the invention will now be described.

[0040] The fourth galvanic isolation transformer 400 is identical to the third galvanic isolation transformer 300, except that the electrical insulating screen 304 is replaced by an electrically conductive screen 402 surrounded by two electrically insulating screens 404, 406 (one of them could be omitted), as in [Fig.2].

[0041] With reference to [Fig.5], the electrically conductive screen 402 includes, for example, slots 502 in order to limit eddy currents.

[0042] These slots may extend only outside the air gaps, in particular between the straight legs 302A-C (top figure), or along the entire length of the electrically conductive screen 502 (bottom figure). In the latter case, a mechanical support 504, 506 may be provided at each end of the slots. These mechanical supports 504, 506 prevent the formation of short-circuited turns.

[0043] With reference to [Fig.6], in another embodiment, the magnetic core 102 has a third straight leg 602 and the two cross members 108, 110 connect the ends of the three straight legs 104, 106, 602. The third straight leg 602 also has an air gap 602E in which, for example, the electrical insulating screen 116 also passes, when the latter is provided.

[0044] For example, as illustrated, the right leg 104 around which the windings 104, 106 are wound is the central leg of the magnetic core 102.

[0045] In conclusion, it is clear that a galvanic isolation transformer such as those described above makes it possible to strengthen galvanic isolation.

[0046] It should also be noted that the invention is not limited to the embodiments described above. It will indeed be apparent to those skilled in the art that various modifications can be made to the embodiments described above, in light of the information just disclosed to them.

[0047] In particular, it will be appreciated that the invention can be applied to different types of transformers: conventional single-phase, three-phase, or polyphase or planar, as well as to different types of winding (strip, copper flat, Litz, etc.). Furthermore, a galvanic isolation transformer according to the invention can be used at both low and high frequencies.

[0048] In the detailed presentation of the invention given above, the terms used shall not be interpreted as limiting the invention to the embodiments set forth in this description, but shall be interpreted as including all equivalents which can be foreseen by a person skilled in the art by applying their general knowledge to the implementation of the teaching which has just been disclosed to them.

Claims

Demands

1. Galvanic isolation transformer (100; 200; 300; 400) comprising: - a magnetic core (102); and - a primary winding (112; 112A-C) and a secondary winding (114; 114A-C), wound around the magnetic core (102) so as to be magnetically coupled to each other; characterized in that the magnetic core (102) is in two parts (102i, 1022), separated from each other, the primary winding (112; 112A-C) being wound around the first part (1020) and the secondary winding (114; 114A-C) being wound around the second part (1022).

2. Galvanic isolation transformer (100; 200; 300; 400) according to claim 1, wherein the first and second parts (102i, 1022) of the magnetic core (102) are separated by air and / or an electrically insulating material, for example one of: Kapton, Nomex, Mylar, Teflon, Mica, and Polypropylene.

3. Galvanic isolation transformer (100; 200; 300; 400) according to claim 1 or 2, wherein the magnetic core (102) has a straight leg (104; 302A-C) having an air gap (104e; 302Ae - 302CE), the primary winding (112; 112A-C) being wound around the straight leg (104; 302A-C) on one side of the air gap (104E; 302AE - 302CE) and the secondary winding (114; 114A-C) being wound around the straight leg (104; 302A-C) on the other side of the air gap (104E; 302AE - 302CE).

4. Galvanic isolation transformer (100; 200; 300; 400) according to claim 3, further comprising an electrical insulating screen (116; 204, 206; 304; 404, 406) passing through the air gap (104E; 302AE - 302Ce).

5. Galvanic isolation transformer (200; 400) according to any one of claims 1 to 4, further comprising an electrically conductive screen (202; 402) interposed between the two parts (102i, 1022) of the magnetic core (102).

6. Galvanic isolation transformer (400) according to claim 5, wherein the electrically conductive screen (402) has eddy current limiting slots (502).

7. Aircraft includes a galvanic isolation transformer (100; 200; 300; 400) according to any one of claims 1 to 6.

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