Three-dimensional flux electric machine stator, manufacturing method and electric machine comprising such a stator, in particular for aircraft turbomachinery

Abstract

The present invention relates, according to a first aspect, to a stator (10) of a three-dimensional flux electric machine, having a principal axis (X) defining: an axial direction, parallel to the principal axis (X); radial directions perpendicular to the principal axis (X) and passing through it; a circumferential direction defined by a circle contained in a plane perpendicular to the principal axis (X) and centered on it;the stator comprising several stator sectors (1) each comprising a block (2) extending circumferentially between a first side (6) and a second side (7) and extending radially between an inner face (8) opposite the principal axis (X) and an outer face (9) opposite the inner face (8), each sector (1) comprising at least one tooth (5) extending from the inner face (8) of the block (2) in the direction of the principal axis (X), one dimension of the tooth (5) being less than one dimension of the block (2) in the circumferential direction at the level of the inner face (8). Figure for the abbreviation: Fig. 1;

Description

Title of the invention: Stator of a three-dimensional flux electric machine, manufacturing method and electric machine comprising such a stator, in particular for an aircraft turbomachine FIELD OF THE INVENTION

[0001] The invention relates generally to the field of electrical machines, and more particularly to machines having a three-dimensional magnetic flux.

[0002] It finds advantageous application in the field of aeronautics, in particular for aircraft turbomachines. STATE OF THE ART

[0003] Electrical machines allow mechanical energy to be converted into electrical energy, or vice versa. This process being reversible, an electrical machine can operate in one direction of conversion from mechanical energy to electrical energy, or in the opposite direction of conversion from electrical energy to mechanical energy.

[0004] In the field of aeronautics, we speak of a "generator" for an electrical machine operating in order to generate electrical energy from mechanical energy. Such machines make it possible in particular to generate electrical energy from the mechanical energy provided by the rotation of the shaft of a turbomachine such as a gas turbine. This makes it possible, for example, to supply electrical energy to a network operating in alternating current which supplies the so-called primary organs of an aircraft, including equipment linked to navigation, flight and propulsion controls, etc. It is known to integrate generators into a device called a "variable frequency generator" (VFG) which allows the supply of the electrical network with a variable frequency which depends on the speed of the turbomachine.

[0005] Some electrical machines have an operation requiring a magnetic flux path that develops in the three dimensions of space. This is particularly the case for transverse flux machines, for which a stator winding is wound around teeth extending in a radial direction perpendicular to the main axis of the electrical machine. However, machines other than transverse flux machines may have a three-dimensional magnetic flux.

[0006] For the manufacture of stators for such machines, several manufacturing solutions are known from the state of the art. A first solution consists of producing the magnetic circuit of the stator from solid materials, by machining (removal of material) in order to obtain the desired stator shape. Such methods have the advantage of being suitable for industrial production due to their simplicity, but generate a significant loss of material linked to the chips produced, which represents a significant cost. In addition, the stators thus designed, formed from a continuous block around their entire circumference, have considerable iron losses, which harms the performance of the electrical machine and generates heat during its operation - which is not desirable when such machines are used in a turbomachine.

[0007] A second solution for manufacturing stators for three-dimensional flux machines is the use of iron powder. Unlike the previous solution, this reduces iron losses, as would be the case by laminating stator sheets, however the structure thus obtained has reduced mechanical resistance, and is therefore not applicable beyond a certain diameter of electrical machine. In addition, it is necessary to use a binder between the powders, reducing the percentage of magnetic material in the stator and therefore its maximum level of magnetic saturation.

[0008] Finally, a third type of manufacturing process developed more recently, and illustrated by the published international application WO 2019 / 202241 A1, consists of winding, over several layers, a single strip of ferromagnetic sheet in which notches are made in order to produce stator teeth. This process limits iron losses due to the lamination of the stator, while making it possible to maintain a high maximum level of magnetic saturation, however it remains complex to implement on an industrial scale, in particular because of the need to carry out variable and progressive cutting of the sheet upstream of the winding phase. Presentation of the invention

[0009] An aim of the invention is to remedy the aforementioned drawbacks, by proposing a method for manufacturing a stator of a three-dimensional flux electric machine which is suitable for production on an industrial scale while allowing good performance of the electric machine, particularly suitable for large-sized (greater than 10 cm) and high-power electric machines.

[0010] Another aim of the invention is to reduce the manufacturing and use cost as well as the environmental impact of such electrical machines.

[0011] In particular, it is emphasized here that the invention falls within the framework of the environmental policy of the Applicant, which has been working for several years now to make a strong contribution to the fight against climate change and significantly improve the environmental performance of aircraft.

[0012] The Applicant takes into consideration the impacting factors in all phases of design and development to obtain aero components and products less energy-intensive, more environmentally friendly nautical vehicles, whose integration and use in civil aviation have moderate environmental consequences with the aim of improving the energy efficiency of aircraft.

[0013] Its ongoing research and development work focuses on new generations of aircraft engines, the weight reduction of aircraft, particularly through the materials used and lighter on-board equipment, the development of the use of electrical technologies to provide propulsion, and, as an essential complement to technological progress, aeronautical biofuels.

[0014] Another aim of the invention is to provide a mechanically robust stator, the iron losses of which are acceptable while having a satisfactory maximum magnetic saturation level.

[0015] To this end, according to a first aspect of the invention, there is proposed a stator of a three-dimensional flux electric machine, having a main axis defining: • an axial direction, parallel to the main axis X • radial directions perpendicular to the main axis X and passing through it; • a circumferential direction defined by a circle included in a plane perpendicular to the main axis X and centered on it;

[0016] the stator comprising several stator sectors each comprising a block extending circumferentially between a first side and a second side and extending radially between an internal face opposite the main axis X and an external face opposite the internal face, characterized in that each sector comprises at least one tooth extending from the internal face of the block in the direction of the main axis X, a dimension of the tooth being less than a dimension of the block in the circumferential direction at the level of the internal face.

[0017] According to one embodiment, one end of the teeth opposite the internal face has a projection extending in the axial direction, the projection being radially opposite the block.

[0018] According to one embodiment, one of the first and second sides has a male connection and the other of the first and second sides has a female connection, the male connection being configured to engage in the female connection so as to prevent relative movement of two adjacent sectors in the axial direction.

[0019] According to one embodiment, the male connection and the female connection have a geometric dovetail shape.

[0020] According to one embodiment, the stator comprises an even number of sectors divided into a first set of sectors and a second set of sectors, the sectors of the first set and the sectors of the second set being arranged in such a way that alternating in the circumferential direction, the sectors of the first set being offset relative to the sectors of the second set in the axial direction.

[0021] Another aspect of the invention relates to a method of manufacturing a stator of a three-dimensional flux electric machine, comprising the steps of: a. manufacturing several stator sectors, each sector comprising a block extending between a first side and a second side in a circumferential direction defined by a circle included in a plane orthogonal to a main axis of the machine and centered thereon, each sector also comprising at least one tooth extending from an internal face of the block arranged between the first and second sides and intended to be located opposite the main axis in an assembled state of the stator, a dimension of the tooth being less than a dimension of the block in the circumferential direction at the level of the internal face, b. assembling the stator by arranging the sectors adjacently in the circumferential direction.

[0022] According to one implementation of the method, the sectors are obtained by machining and / or molding and / or additive manufacturing.

[0023] According to one implementation, the method comprises, before assembly, a step of winding at least one stator winding around the teeth and / or around a projection arranged on one end of the teeth opposite the internal face, said projection extending in the axial direction and radially opposite the block.

[0024] Another aspect of the invention relates to an electrical machine comprising a stator as defined above.

[0025] Another aspect of the invention relates to a turbomachine comprising an electric machine as defined in the preceding paragraph.

[0026] According to one embodiment of the turbomachine, the electrical machine operates in generator mode and is connected directly or via a reducer to a shaft of the turbomachine so as to convert mechanical energy supplied by the rotation of the shaft into electrical energy.

[0027] Another aspect of the invention relates to an aircraft comprising a turbomachine as defined previously.

[0028] Thus, the stators of electrical machines obtained by the proposed method are made by repeating a periodic and / or symmetrical three-dimensional pattern, allowing simple manufacturing and suitable for industrialization of the process. In addition, these stators have both reduced iron losses compared to single-block stators formed from solid blocks, while being mechanically robust and being able to achieve high magnetic saturation. It will be possible to choose a number of sectors adapted to the desired application: the greater the number of sectors, the more the reduction will be stator iron losses. Conversely, for applications where particularly high mechanical strength of the machine is desirable, a smaller number of sectors will be used. DESCRIPTION OF FIGURES

[0029] Other characteristics, aims and advantages of the invention will emerge from the following description, which is purely illustrative and non-limiting, and which must be read in conjunction with the appended drawings in which:

[0030] [Fig.l] schematically illustrates an electric machine stator according to one embodiment of the invention;

[0031] [Fig.2] schematically illustrates a stator sector of an electric machine according to one embodiment of the invention;

[0032] [Fig.3] illustrates an electrical machine according to one embodiment of the invention.

[0033] [Fig.4] schematically illustrates a method of manufacturing an electrical machine stator according to an embodiment of the invention.

[0034] [Fig. 5] schematically illustrates a turbomachine equipped with an electric machine comprising a stator according to one embodiment of the invention.

[0035] [Fig.6] schematically illustrates an aircraft comprising a turbomachine equipped with an electric machine comprising a stator according to one embodiment of the invention.

[0036] Throughout the figures, similar elements bear identical references.

[0037] DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0038] In all that follows, a system of directions will be defined comprising an axial direction corresponding to a main axis X of the electrical machine, around which the machine rotates during operation; radial directions, corresponding to any direction perpendicular to the main axis X and passing through it, and a circumferential direction defined by a circle included in a plane orthogonal to the main axis X and centered on it.

[0039] With reference to Figures 1 and 2, a stator 10 of an electrical machine comprises a plurality of sectors 1, intended to be assembled so as to form a stator 10, that is to say that each sector 1 comprises a block 2 which covers, between a first side 6 and a second side 7, a part of the circumference of the stator, the set of blocks 2 of the different sectors 1 thus covering the 360° of the circumference of the stator. Each block 2 further comprises a third side 18 and a fourth side 19, arranged in planes orthogonal to the axial direction. Each sector 1 is assembled, at the first side 6 of its block 2, to the second side 7 of the block 2 of a adjacent sector on the one hand, and at the level of the second side 7 of its block 2, to the first side 6 of the block 2 of a second adjacent sector. Each block 2 further has an internal face 8 arranged opposite the main axis X, and an external face 9 arranged on the other side of the block 2 in a radial direction.

[0040] Each sector 1 of the stator 10 has a tooth 5 connected to its block 2 at its internal face 8, the tooth 5 projecting from the block 2 in the direction of the main axis X. A thickness of the tooth 5 is less than a thickness of the block 2, taken at the internal face 8, the thickness being defined according to the circumferential direction. It may be provided that a block 2 has more than one tooth 5, the sum of the thicknesses of the teeth 5 always being less than the thickness of the block 2. As illustrated in [Fig. 3], the teeth 5 make it possible to accommodate one or more first stator windings 15 wound around each tooth - and therefore in a radial direction - and provided to interact with a rotor 17 of the electrical machine 13 once assembled.

[0041] Some of the teeth 5 of the sectors 1 may, according to one embodiment, comprise projections 14 arranged in the axial direction, and radially opposite the corresponding block 2, as shown in [Fig.l]. In other words, a projection of the projection 14 in the radial direction is located on the block 2. This makes it possible in particular to accommodate one or more second stator windings 15' wound in the axial direction. It is thus possible to choose to have only the first stator windings 15 on the teeth 5, or only the second stator windings 15' on the projections 14. It is also possible to combine first radial stator windings 15 with second axial stator windings 15'.This modularity of the placement of the windings 15, 15' on the stator results from the arrangement of the latter in sectors 1, and consequently allows a modularity of the operation of the electrical machine 10 itself: one can choose to connect the windings in series or in parallel, to have a polyphase winding arrangement when the windings arranged on different teeth are independent of each other, or even improve the cooling of the machine by not having windings on certain teeth 5 and / or projections 14 of the stator.

[0042] In order to mechanically connect the blocks 2 of two adjacent sectors 1, the blocks 2 have an indexing system. According to one embodiment, each of the first and second sides 6, 7 of each block 2 comprises a female connection 3 and a male connection 4, the male connection 4 of a block 2 engaging in the female connection 3 of an adjacent block 2 and vice versa. In addition to the fact that it allows precise relative positioning of two adjacent blocks 2 with respect to each other, such an indexing system prevents any relative movement between two adjacent blocks in the axial direction, and must therefore be sufficiently robust to withstand the axial mechanical forces imposed on the sectors 1 during operation of the machine. electrical 13. The indexing system thus allows the alignment and maintenance of the sectors 1, which can in particular be placed in an electrical machine casing.

[0043] According to an embodiment not shown, it can be provided that one of the first side 6 of a first block 2 and the second side 7 of an adjacent second block 2 comprises only one male connection 4, the other of the first side of the first block 2 and the second side 7 of the adjacent second block 2 comprising a female connection 3, these two connections cooperating together in an assembled state of the stator.

[0044] The presence of parasitic air gaps between different parts of a stator reduces the magnetic performance of an electrical machine. Thus, advantageously, the indexing system is designed to ensure the closest possible contact between two adjacent blocks 2, so as to reduce the air gap disposed between them. For example, it may be provided that the female and male connections 3, 4 each have a dovetail shape, this type of connection making it possible to minimize the relative movement of two adjacent blocks 2 in the circumferential direction, once these two blocks are assembled. Other connection geometries may nevertheless be provided, provided that they allow assembly of adjacent sectors 1 by sliding.

[0045] According to an embodiment visible in [Fig.l], the stator is divided into two sets of sectors 11, 12, so that each sector 1 of the first set 11 is, in the assembled state of the stator, arranged circumferentially between two sectors 1 of the second set 12 and each sector 1 of the second set 12 is arranged between two sectors 1 of the first set 11. Such an “alternating” arrangement is characterized by the sole fact that the sectors 1 of the two sets 11, 12 can be offset in the axial direction (X), that is to say that the third sides 18 - and correspondingly the fourth sides 19 - of the sectors 1 of the first set 11 are not arranged on the same plane respectively as the third and fourth sides 18', 19' of the sectors 1 of the second set 12, but on two distinct planes corresponding to two distinct axial positions.This embodiment allows, for certain magnetic flux geometries for which the flux does not pass through the stator, for any circumferential position, over the entire axial direction, to have recesses in the parts of the stator where the flux does not pass. This allows a saving of material during the manufacture of the stator, in comparison with a corresponding monobloc stator, or even with a stator according to the invention but whose sectors 1 are all arranged in the same axial position. This also allows the overall mass of the stator to be reduced, which is particularly interesting for aeronautical applications of the electrical machine 13. .

[0046] According to this embodiment with two sets 11, 12 of sectors 1, and when an indexing system of the blocks 2 is provided, the connections of the blocks 2 of the first set 11 and of the second set 12 are necessarily arranged at a distance axially different from their respective third sides 18, 18' - or equivalently, from their respective fourth sides 19, 19'.

[0047] By way of illustration, a non-limiting example of magnetic flux passing through the electrical machine is shown in red arrows in [Fig.3].

[0048] A method 100 for manufacturing a stator as defined above is illustrated in [Fig. 4]. The method comprises at least a first step 101 of manufacturing stator sectors 1 comprising a block 2 and a tooth 5 as defined above, and a second step 103 of assembling the stator by arranging the sectors 1 next to each other in the circumferential direction.

[0049] The manufacturing step 101 may be a step of molding each sector 1, or of cutting the sector 1 in a mass of material. It may possibly be provided that this is an additive manufacturing step. The material may be any ferrous material having a permeability greater than 1, for example an alloy based on Fe-Si, Fe-Co, Fe-Ni.

[0050] When a system for indexing the blocks 2 is provided, the assembly step 103 comprises the positioning of each male connection 4 in the corresponding female connection 3 of the adjacent block 2, so as to ensure the largest contact surface between the two blocks 2 which leaves the least possible space, in order to minimize the appearance of parasitic air gaps.

[0051] According to one implementation of the method, a step 102 of winding a stator winding 15 is provided. Due to the segmentation of the stator 10 into sectors 1, this step 102 can be carried out individually on each sector 1 before the assembly 103 of the stator, which has the advantage of a winding that is more easily automated and generally more robust than a conventional winding carried out on an assembled stator, due to the geometric simplicity of each sector, and thus allowing the industrial production of such stators and the electrical machines comprising them. For example, an independent winding can be provided on each tooth 5, which is difficult to achieve when the winding is carried out on an assembled stator. Thus, when several winding phases are planned, the fact that the winding 102 is prior to the assembly 103 makes it easier to segregate the different winding phases as desired.Furthermore, the fact of providing the winding 102 before the assembly 103 is advantageous for minimizing the occurrence of partial discharges in the winding: it is possible to arrange turns of separate windings 15, 15' having differences in electrical potential far from each other, so as to avoid exceeding a potential difference, called "breakdown voltage" beyond which such discharges can occur in accordance with Paschen's law. More generally, the fact that the winding 102 takes place before the assembly 103 allows precise placement of the windings 15, 15' on the sectors 1. to achieve a desired organization of the stator.

[0052] Alternatively, the winding step 102 can be carried out, in a conventional manner, after the assembly 103 of the stator.

[0053] Furthermore, the winding step 102 may comprise the winding of a stator winding 15' around projections 14 arranged on the ends of the teeth 5 opposite the internal face 8 of the corresponding blocks 2, the projections 14 extending in the axial direction, and being radially opposite the block 2. Such winding may be provided in addition to the winding of the winding 15 around the teeth 5, or as a replacement for the latter.

[0054] An electrical machine 13 provided with a stator as defined previously is illustrated in [Fig. 3]. It comprises a stator 10 as defined previously, as well as a rotor 17, an excitation coil 16 and one or more stator winding(s) 15, 15'.

[0055] [Fig. 5] represents a turbomachine 24 provided with an electric machine 13 as defined previously, operating in engine mode or in generator mode. The turbomachine may comprise a fan section 20, and comprises a compression section 21, a combustion section 22 and a turbine section 23. For example, provision may be made to use the electric machine 13 in generator mode, in order to convert part of the mechanical energy resulting from the rotation of the turbomachine shaft 26 into electrical energy, in particular to power the so-called “primary” components of an aircraft, comprising the components linked to navigation, flight controls and propulsion. If necessary, a reducer may be interposed between the shaft of the turbomachine 26 and the rotor 17 of the electric machine so as to allow the rotation speed of the rotor 17 to be regulated.Alternatively, it can be provided that the rotor 17 of the electric machine is directly connected to the shaft of the turbomachine 26, and therefore rotates at the same speed as the latter.

[0056] An aircraft 25 equipped with a turbomachine 24 as defined in the preceding paragraph is illustrated in [Fig.6].

Claims

Claims

1. Stator (10) of a three-dimensional flux electric machine, having a main axis (X) defining: • an axial direction, parallel to the main axis (X) • radial directions perpendicular to the main axis (X) and passing through it; • a circumferential direction defined by a circle included in a plane perpendicular to the main axis (X) and centered on it;the stator comprising several stator sectors (1) each comprising a block (2) extending circumferentially between a first side (6) and a second side (7) and extending radially between an internal face (8) facing the main axis (X) and an external face (9) opposite the internal face (8), characterized in that each sector (1) comprises at least one tooth (5) extending from the internal face (8) of the block (2) in the direction of the main axis (X), a dimension of the tooth (5) being less than a dimension of the block (2) in the circumferential direction at the level of the internal face (8).;

2. Stator (10) according to the preceding claim, one end of the teeth (5) opposite the internal face (8) having a projection (14) extending in the axial direction, the projection being radially opposite the block (2).

3. Stator (10) according to the preceding claim, one of the first (6) and second (7) sides having a male connection (4) and the other of the first (6) and second (7) sides having a female connection (3), the male connection (4) being configured to engage in the female connection (3) so as to prevent relative movement of two adjacent sectors (1) in the axial direction.

4. Stator (10) according to claim 3, the male connection (4) and the female connection (3) having a dovetail geometric shape.

5. Stator (10) according to any one of the preceding claims, comprising an even number of sectors (1) divided into a first set (11) of sectors and a second set (12) of sectors, the sectors of the first set (11) and the sectors of the second set (12) being arranged alternately in the circumferential direction, the sectors of the first set (11) being offset relative to the sectors of the second set (12) in the axial direction.

6. Method (100) for manufacturing a stator (10) of a three-dimensional flux electric machine, comprising the steps of: a. manufacturing (101) several stator sectors (1), each sector (1) comprising a block (2) extending between a first side (6) and a second side (7) in a circumferential direction defined by a circle included in a plane orthogonal to a main axis (X) of the machine and centered thereon, each sector (1) also comprising at least one tooth (5) extending from an internal face (8) of the block (2) arranged between the first (6) and the second side (7) and intended to be located opposite the main axis (X) in an assembled state of the stator (10), a dimension of the tooth (5) being less than a dimension of the block (2) in the circumferential direction at the internal face (8), b. assembly (103) of the stator (10) by arranging the sectors (1) adjacently in the circumferential direction.

7. Method of manufacturing a stator (10) according to claim 6, the sectors (1) being obtained by machining and / or molding and / or additive manufacturing.

8. Method of manufacturing a stator (10) according to any one of claims 6 or 7, comprising before assembly (103), a step of winding (102) at least one stator winding (15, 15') around the teeth (5) and / or around a projection (14) arranged on one end of the teeth (5) opposite the internal face (8), said projection (14) extending in the axial direction and radially opposite the block (2).

9. An electrical machine (13) comprising a stator (10) according to any one of claims 1 to 5.

10. Turbomachine (24) comprising an electric machine (13) according to the preceding claim.

11. Turbomachine according to the preceding claim, the electric machine (13) operating in generator mode and being connected directly or via a reducer to a shaft of the turbomachine (24) so as to convert mechanical energy supplied by the rotation of the shaft into a electrical energy.

12. Aircraft (25) comprising a turbomachine (24) according to any one of claims 10 and 11.

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