ROTATING ELECTRICAL MACHINE WITH SUPERCONDUCTING ELEMENTS AND CRYOGENIC ENVELOPES

Description

[0001] The invention relates to a rotating electrical machine.

[0002] One field of application of the invention relates to electricity generators and electrically powered motors, to be fitted to means of transport, such as aircraft, for example airplanes or helicopters.

[0003] The document DIFAN ZHOU ET AL, "Topical Review; An overview of rotating machine systems with high-temperature bulk superconductors;", SUPERCONDUCTOR SCIENCE AND TECHNOLOGY, IOP PUBLISHING, TECHNO HOUSE, BRISTOL, GB, vol 25, no. 10, August 08, 2012 (2012-08-08), page 103001, describes a rotating machine according to the preamble of claim 1.

[0004] The paper COLLE ALEXANDRE ET AL, "Analytical Model for the Magnetic Field Distribution in a Flux Modulation Superconducting Machine", December 12, 2019 (2019-12-12), vol 55, no. 12, page 1-9, describes a rotating electric machine with superconducting elements, comprising a rotor and two stators placed on either side of the rotor.

[0005] The paper MASSON PJ ET AL, "Design of HTS Axial Flux Motor for Aircraft Propulsion", IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, IEEE SERVICE CENTER, LOS ALAMITOS, CA, US, vol 17, no. 2, June 2, 2007 (2007-06-02), pages 1533-1536, describes a rotating electric machine with superconducting elements, having a stack of stators and rotors.

[0006] Document EP2037558 relates to a rotating electrical machine comprising a rotor and two stators placed on either side of the rotor.

[0007] Document EP2611007 relates to a rotating electrical machine comprising a rotor and two stators placed on either side of the rotor.

[0008] Rotating machines are known, comprising on their rotor superconducting pellets with flux barriers inside an axial flux inductor coil, and one or two armatures when they operate as generators. The rotation of the pellets creates a modulation of the magnetic flux in the armature(s) between a minimum value created behind the pellets and a maximum value created between the pellets, which makes it possible to generate an electromotive force there.

[0009] However, for applications requiring high energy density, it is necessary to have a large difference between the maximum and minimum value of the magnetic flux in the armature, the modulation amplitude being directly proportional to the electromagnetic force created (Faraday's law).

[0010] Thus, in these known machines it turns out that the minimum value of the magnetic flux in the armature is quite high.

[0011] The invention aims to obtain a rotating electrical machine with superconducting elements, which makes it possible to reduce the minimum value of the magnetic flux in the armature while having a large maximum value of the magnetic flux in the armature.

[0012] For this purpose, a first object of the invention is a rotating electrical machine according to claim 1.

[0013] For this purpose, a second object of the invention is a rotating electrical machine according to claim 2.

[0014] Claims 3 to 14 relate to embodiments of these rotating electrical machines.

[0015] A third subject of the invention is an aircraft, comprising an electricity consuming or electricity generating member and a rotating electrical machine as described above, which is connected to a connection circuit to the electricity consuming or electricity generating member to enable it to be supplied with electricity or to be provided with electricity.

[0016] The invention will be better understood upon reading the following description, given solely as a non-limiting example with reference to the figures in the attached drawings. [ Fig. 1 ] schematically represents in perspective a machine 1 according to a first embodiment of the invention. [ Fig. 2 ] schematically represents in perspective a machine 1 according to a second embodiment of the invention. [ Fig. 3 ] schematically represents in perspective a part of a machine 1 according to a third embodiment of the invention. Fig. 4] is a perspective view in two sectional planes of the magnetic flux iso-lines around and in a superconducting magnetic flux barrier element that can be used in a rotating electrical machine generating electricity according to an embodiment of the invention. Fig. 5 ] schematically represents the value of the magnetic field for a first example of a machine 1 according to the invention. [ Fig. 6 ] schematically represents the value of the magnetic field for a second comparative example of a machine 1 not falling within the scope of the invention. [ Fig. 7 ] schematically represents axial component curves of the magnetic induction generated by a machine according to the first example of the invention and according to the second comparative example at a point located between a rotor and an armature. Fig. 8] schematically represents axial component curves of the magnetic induction generated by a machine according to the first example of the invention and according to the second comparative example at a point located on an armature winding. Fig. 9 ] schematically represents in perspective a solenoid which can be used in the machine according to the invention. [ Fig. 10 ] represents the evolution of the induction as a function of the number of stacks of rotors of the machine according to the invention. [ Fig. 11 ] schematically represents a cryostat plug which can be used in the machine according to the invention. Fig. 12 ] schematically represents in side view a machine which is not according to the invention. Fig. 13 ] schematically represents in front view a machine following the Figure 12 . [ Fig. 14 ] schematically represents in side view a machine according to the first object of the invention. Fig. 15] schematically represents in front view a machine following the Figure 14 . [ Fig. 16 ] schematically represents in side view a machine according to the second object of the invention. Fig. 17 ] schematically represents in front view a machine following the figure 16 .

[0017] To figures 1 , 2 And 3 , in an electrical machine 1 with flux barriers comprising superconducting axial magnetic flux barrier elements 3, the modulation of the magnetic flux depends directly on the position of the screens which oppose the passage of the flux relative to the windings 7 of the armature 5 (generator operation) or of the inductor (motor operation).

[0018] To figures 1 , 2 And 3, the rotating electrical machine 1 is axial flux and has flux barriers. The machine 1 comprises several rotors each generally designated by the reference 2, which may be for example two or three rotors 21, 22 and 23 at figures 1 And 2 , or which may be others. The rotating electrical machine 1 thus comprises one or more first rotors, designated by the reference 21 at figures 1 , 2 And 3 , and one or more second rotors, designated by the reference 22 in the Figure 1 and by references 22 and 23 to the Figure 2. The terms axial and coaxial mean extending along the axis AX of rotation. The radial directions are located in planes perpendicular to the axis AX of rotation and start from the axis AX of rotation. The rotors 2 are secured to each other on a shaft or axis AX of rotation. Each rotor 2 comprises a set of superconducting axial magnetic flux barrier elements 3, which are distributed along the tangential direction DC around the axis AX of rotation and which are located in a plane perpendicular to the axis AX of rotation. Between the superconducting axial magnetic flux barrier elements 3 of each rotor 2, 21, 22, 23 there are zones 4 for the passage of axial magnetic flux, which are distributed along the tangential direction DC around the axis AX of rotation and which are located in the plane perpendicular to the axis AX of rotation. The rotors 2, 21, 22, 23 are spaced successively from each other along the axis AX of rotation.

[0019] In one embodiment, each superconducting axial magnetic flux barrier element 3 of one of the rotors 2 (which may be, for example, the first rotor 21) is coaxial at least partially with another superconducting axial magnetic flux barrier element 3 of the other rotor(s) 2 (which may be, for example, the second rotor(s) 22, 23). Thus, at least a portion of each superconducting axial magnetic flux barrier element 3 of one of the rotors 2 (which may be, for example, the first rotor 21) is coaxial with at least a portion of another superconducting axial magnetic flux barrier element 3 of the other rotor(s) 2 (which may be, for example, the second rotor(s) 22, 23).

[0020] Each zone 4 of axial magnetic flux passage of one of the rotors 2 (which may be for example the first rotor 21) is coaxial at least partially with another zone 4 of axial magnetic flux passage of the other rotor(s) 2 (which may be for example the second rotor(s) 22, 23). Thus, at least a portion of each zone 4 of axial magnetic flux passage of one of the rotors 2 (which may be for example the first rotor 21) is coaxial with at least a portion of another zone 4 of axial magnetic flux passage of the other rotor(s) 2 (which may be for example the second rotor(s) 22, 23).

[0021] The machine 1 comprises one (or more) superconducting inductor coils 6, which is capable of inducing an axial magnetic field, which is directed along the axis AX of rotation and which may be continuous. For this purpose, the superconducting inductor coil 6 may comprise external electrical terminals (not shown) used to connect it to a source of continuous electric voltage or current, to produce the axial magnetic field. The superconducting inductor coil 6 is annular around the axis AX of rotation along the tangential direction DC and surrounds the superconducting axial magnetic flux barrier elements 3 of the rotors 2 and the armature(s) 5. The superconducting inductor coil 6 creates an intense magnetic field B, thanks to large current densities circulating in this coil 6, which may be for example 25 times higher than the current density of copper.

[0022] The machine 1 comprises one or more armatures (or stators), each of which is generally designated by the reference 5, such as for example the armature(s) 51 and 52. Each armature 5 comprises armature windings 7, which are distributed in the tangential direction DC around the axis AX of rotation.

[0023] The rotating electrical machine 1 can operate in electricity generator mode on the armature(s) 5 or in motor mode supplied with electricity on the armature(s) 5.

[0024] According to one embodiment, each armature winding 7 may form, for example, a loop not surrounding the axis AX of rotation and comprises one or more conductors forming a loop not surrounding the axis AX of rotation. This is illustrated as a non-limiting example in Figure 11. Each auxiliary (geometric) direction 70 around which each armature winding 7 extends may be substantially parallel to the axis AX of rotation or have a component parallel to the axis AX of rotation. Thus, this auxiliary direction 70 of the winding (for example substantially parallel to the axis AX of rotation) is located at a first non-zero distance 76 from the axis AX of rotation. Thus, the conductor(s) of the loop formed by each armature winding 7 is located at a second distance 77 relative to its auxiliary direction 70, this second distance being less than the first distance 76 and being able to be variable (as shown in FIG. Figure 11 ) or constant around its auxiliary direction 70.

[0025] Each armature winding 7 may have other external electrical terminals (not shown) used to connect it to an electrical component not shown. In the case where the rotating electrical machine 1 operates in electricity generator mode, each armature winding 7 makes it possible to send to the electrical receiving component the electrical voltage (electromotive force) generated in this armature winding 7 by induction of the variable axial magnetic field moving in the tangential direction DC due to the rotation of the elements 3 of the rotors 2 around the axis AX of rotation. The electromotive force according to the Lenz-Faraday law is: ε = − dϕ dt where ε is the electromagnetic force, Φ is the magnetic flux and t is the time. The elements 3 are brought closer to the armature windings 7 along the axis AX to maximize the modulation of the flux and therefore the electromotive force generated in the armature windings 7.

[0026] The rotors 2 are rotatably mounted on the axis AX of rotation relative to the armature(s) 5 and to the induction coil 6, fixed to each other on a chassis not shown.

[0027] Each armature 5 is positioned between two of the rotors 2 in the direction following the axis AX of rotation.

[0028] In one embodiment shown in Figure 1 , the single armature 5 is positioned between the first rotor 21 and the second rotor 22.

[0029] In one embodiment shown in Figure 2 , the first armature 51 is positioned between the first rotor 21 and the second rotor 22 and the second armature 52 is positioned between the second rotor 22 and the other second rotor 23.

[0030] Generally, the machine 1 has a first number N of rotors 2 successively spaced from each other along the axis AX of rotation, where N is a prescribed natural number, which is greater than or equal to 2 or 3, and a second number N-1 of armatures 5 successively positioned between the N rotors 2 along the axis AX of rotation. Embodiments corresponding to N ≥ 3 are referred to as a machine 1 with several stacks of rotors 2 below.

[0031] As represented in the Figure 3, when the machine 1 is in generator operation, the superconducting inductor coil 6 generates a magnetic field B (as represented by the long arrows F1 and the short arrows F2), which is directed along the axis AX of rotation in the interior space 8 which it surrounds and in which the rotors 2 and the armature(s) 5 are located. Each superconducting axial magnetic flux barrier element 3 is configured to have a determined extent in the plane 30 perpendicular to the axis AX of rotation and to create in this extent an obstacle (or screen) to the passage of the axial magnetic field B, as symbolized by the short arrows F2.For a temperature below their critical temperature (the critical temperature being for example below 100 K, or in particular below 50 K), the superconducting materials of the elements 3, of the inductor coil 6 and possibly of the armature windings 7 have zero resistivity, which allows the circulation of direct currents without losses. For a temperature below their critical temperature, the superconducting materials of the elements 3 have a diamagnetic response when the magnetic field B is increased, that is to say they have a magnetic field barrier behavior analogous to the Meissner effect observed under very low field.

[0032] This screen or barrier to the passage of the axial magnetic field B results in a strong attenuation ATTB of the value of the magnetic field in front of and behind the element 3 along the axis AX, this attenuation ATT being all the stronger (i.e. the value of the magnetic field B being all the smaller) as one goes from the outer edge 31 of the element 3 to the center 32 of the element 3 behind the rear face 33 of the element 3 and in front of the front face 34 of the element 3, as shown in Figure 4 , showing the magnetic flux iso-lines around and in element 3 and their value expressed in Tesla (T) with reference to the first ECH1 scale of values.

[0033] At this Figure 4 , the superconducting pellet forming element 3 is circular cylindrical around the axis AX with a radius of 4 cm, is immersed in the constant axial magnetic field B of 3 T and has a critical current density of 1000 A / mm2. The Figure 4was obtained by calculation using a finite element electromagnetic model (H-formulation). The majority of the current in the superconducting pellets 3 develops over a thin penetration thickness from their outer surface. The penetration thickness depends on the intensity of the magnetic field in which the pellet is immersed, as well as on its intrinsic electrical properties. It can be noted that the penetration thickness is greater perpendicular to the AX axis, than along the AX axis. The thickness along the AX axis is proportional to the distance from the center 32 of the pellet. Generally speaking, the penetration thickness of the element 3 or of the pellet 3 along the AX axis is relatively small, so as not to have degraded performance.

[0034] We see at the Figure 4that the value B1 of the magnetic field near the outer edge 31 of the element 3 is greater than the value B2 of the magnetic field near the center 32 of the element 3 in the same plane perpendicular to the axis AX.

[0035] Similarly, this ATTB attenuation of the magnetic field value is all the weaker (i.e. the magnetic field value is all the greater) as one moves away from element 3 parallel to the AX axis. We see in fact at Figure 4 that the value B3 of the magnetic field far from element 3 is greater than the value B4 of the magnetic field at a closer distance from element 3 in the same direction parallel to the axis AX.

[0036] On the other hand, the zones 4 of axial magnetic flux passage allow VB values ​​of the axial magnetic field B to pass through, which are greater than those located in front of and behind the element 3. We can see in fact at Figure 4that the value B5 of the magnetic field transversely next to the element 3 is greater than the value B2 of the magnetic field near the center 32 of the element 3 in front of and behind it.

[0037] The rotation of the rotors 2 around the axis AX generates through the armature(s) 5 a magnetic flux, which varies depending on whether a superconducting element 3 of axial magnetic flux barrier of the rotors 2 or a zone 4 of axial magnetic flux passage passes axially opposite the armature(s) 5.

[0038] In one embodiment shown in figures 1 to 3, each superconducting axial magnetic flux barrier element 3 of one of the rotors 2 (which may be for example the first rotor 21) is aligned (i.e. is completely coaxial) along the axis AX of rotation with another superconducting axial magnetic flux barrier element 3 of the other rotor(s) 2 (which may be for example the second rotor(s) 22, 23), and each axial magnetic flux passage zone 4 of one of the rotors 2 (which may be for example the first rotor 21) is aligned (i.e. is completely coaxial) along the axis AX of rotation with another axial magnetic flux passage zone 4 of the other rotor(s) 2 (which may be for example the second rotor(s) 22, 23).

[0039] Each superconducting axial magnetic flux barrier element 3 may have an extent limited to a first non-zero determined angular sector around the rotation axis AX, and each axial magnetic flux passage zone 4 may have an extent limited to a second non-zero determined angular sector around the rotation axis AX. For example, the first determined angular sector may be equal to the second determined angular sector.

[0040] Each armature winding 7 may have an extent limited to a third determined non-zero angular sector around the axis AX of rotation. The third determined angular sector may be less than or equal to the first determined angular sector. The third determined angular sector may be less than or equal to the second determined angular sector. The number of armature windings 7 on each armature 5 may be greater than or equal to the sum of the number of superconducting axial magnetic flux barrier elements 3 and the number of axial magnetic flux passage zones 4 of each rotor 2, as shown in figures 1 And 2. Thus, in each rotational position of the rotors 2 around the rotation axis AX, when certain armature windings 7 are axially opposite superconducting axial magnetic flux barrier elements 3, other armature windings 7 are axially opposite axial magnetic flux passage zones 4. Thus, during rotation of the rotors 2 around the rotation axis AX, successively very low then very high values ​​of magnetic flux are obtained in each armature winding 7.

[0041] There Figure 5schematically represents a distribution calculated by the finite element method for the value of the magnetic field, with reference to the second scale ECH2 of values ​​in Tesla (T), and this around two axially aligned superconducting axial magnetic flux barrier elements 3, when an armature winding 7 is located between these two elements 3 and when a constant external axial field is applied, and this without other elements 3 positioned along the axis AX of rotation, for a first example of a machine 1 according to the embodiment of the invention of the Figure 1 , further having the following parameters: nominal power of 50 kW, nominal torque of 95 Nm, rotation speed of 5000 revolutions per minute, operating temperature of 30 K, radius of elements 3 of 40 mm, total weight of 20 kg, weight of each rotor of 4 kg.

[0042] There Figure 6schematically represents a distribution calculated by the finite element method for the value of the magnetic field, with reference to the third scale ECH3 of values ​​in Tesla (T), and this around two other 7' armature windings aligned axially, when a superconducting element 3' of axial magnetic flux barrier identical to element 3 of the Figure 5 is located between these two 7' armature windings when a constant external axial field identical to that of the Figure 5 is applied, and this without other armature windings 7' and without other superconducting element 3' of axial magnetic flux barrier, according to a second comparative example not falling within the scope of the invention.

[0043] We see at the Figure 5 that, although at the Figure 5each axial magnetic flux barrier superconducting element 3 is further axially from the armature winding 7 than is each armature winding 7' from the axial magnetic flux barrier superconducting element 3' of the Figure 6 , the value (minimum value) of the magnetic field at the center 71, 72 of the front and rear faces of the armature winding 7 at the Figure 5 is lower (0.25 T) than the value (minimum value) of the magnetic field at the center 71', 72' of the front and rear faces of the armature windings 7' at the Figure 6 (0.45 T), facing the 3' element. We also see at the Figure 5 that the maximum value of the magnetic flux taken transversely next to the armature 5 (points 73 and 74 on the Figure 5 ) is substantially identical to the maximum value of the magnetic flux next to the armature windings 7' (points 73', 73'', 74', 74'') of the Figure 6 .

[0044] The invention therefore results in a 44% reduction in the minimum value of the magnetic flux in the armature 5 while having a high maximum value of the magnetic flux in the armature. This allows an increase in the rotor torque of 25%. The invention thus results in an increase in the modulation of the magnetic flux in the armature(s) 5, and therefore an increase in the production of electricity in the armature(s) 5.

[0045] There Figure 7 represents: the curve C1 of the axial component B z (expressed in T on the ordinate and calculated via the three-dimensional electromagnetic model with finite elements described previously) of the magnetic induction generated by a machine 1 according to the first example mentioned above according to the invention at a point located at a mean radius of the rotors 2 relative to the axis AX (located axially opposite the elements 3 of the rotors 2 and opposite one of the armature windings 7 during the rotation of the rotors 2) and at the center of the air gap between one of the rotors 2 and an armature 5, as a function of the angular position of rotation (expressed in radians) of the rotors 2 on the abscissa, as well as the curve C2 of the axial component B z (expressed in T on the ordinate and calculated via the three-dimensional electromagnetic model with finite elements described previously) of the magnetic induction, generated by another machine according to the second comparative example mentioned above, not falling within the scope of the invention,whose single rotor is located axially between two single armatures according to the aforementioned comparative example, taken at a point located at an average radius of the rotor relative to the axis AX (located axially opposite superconducting axial flux barrier pellets of the rotor 2 and opposite one of the armature windings during rotation of the rotor 2) and at the center of the air gap between the rotor and one of the armatures, as a function of the angular position of rotation (expressed in radians) of its rotor on the abscissa.

[0046] We see at the Figure 7 that axially opposite the superconducting axial magnetic flux barrier elements 3, the magnetic flux is reduced by 95% between its maximum value and its minimum value on curve C2 for the comparative machine, whereas the magnetic flux is reduced by 99% between its maximum value and its minimum value on curve C1 for the machine according to the invention.

[0047] There figure 8 represents: the curve C3 of the axial component B z (expressed in T on the ordinate and calculated via the three-dimensional electromagnetic model with finite elements described previously) of the magnetic induction generated by a machine 1 according to the first example mentioned above according to the invention at a point located at a mean radius of the rotors 2 relative to the axis A and on the turns of one of the armature windings 7 furthest from the elements 3 during the rotation of the rotors, as a function of the angular position of rotation (expressed in radians) of the rotors 2 on the abscissa, as well as the curve C4 of the axial component B z (expressed in T on the ordinate and calculated via the three-dimensional electromagnetic model with finite elements described previously) of the magnetic induction, generated by the second comparative example mentioned above of another comparative machine at a point located at a mean radius of the rotors 2 relative to the axis AX ... further from its elements,as a function of the angular position of rotation (expressed in radians) of its rotor on the abscissa.

[0048] We see at the figure 8 that on the armature windings 7, the magnetic flux varies between the maximum value of 1.4 T and the minimum value of 0.06 T on curve C3 for the machine according to the invention, i.e. a variation of 1.34 T which is 45% greater than the variation of 0.92 T between the maximum value of 1.26 T and the minimum value of 0.34 T on curve C4 for the comparative machine. Consequently, the invention makes it possible to increase the screening effect by 45% and to increase the torque by 25% compared to the comparative machine having a configuration according to the state of the art. This also results in an increase in the power of the machine 1 according to the invention, while making it possible to have an identical cryogenic cooling enclosure.

[0049] In one embodiment shown in figures 1 to 4, one or more or all of the superconducting axial magnetic flux barrier elements 3 comprises or is formed from a solid axial magnetic flux barrier pellet of a superconducting material, the extent of which is delimited by its outer edge 31. The solid axial magnetic flux barrier pellet 3 may be cylindrical about a direction parallel to the axis AX of rotation, for example circular cylindrical.

[0050] In another embodiment not shown, one or more or all of the superconducting axial magnetic flux barrier elements 3 comprises or is formed from one or more axial magnetic flux barrier loops of a superconducting material, the extent of which is delimited by its outer edge.

[0051] On each rotor 2, the superconducting axial magnetic flux barrier elements 3 are fixed in through openings of an electrically insulating support 9 forming part of the rotor 2. This support 9 is fixed to the axis AX of rotation and can be formed of a flat plate, for example circular around the axis AX. In an embodiment shown in figures 1 And 2 , one or more or all of the axial magnetic flux passage zones 4 comprises or is formed from a portion of the support 9 made of the electrically insulating insulating material. In one embodiment shown in Figure 3 , one or more or all of the axial magnetic flux passage zones 4 comprises or is formed from another gaping opening of the support 9.

[0052] In one embodiment shown in figures 1 to 17 , one or more or all of the armature windings 7 comprises or is formed from a superconducting winding (first case).

[0053] In another embodiment shown in figures 1 to 17 , one or more or all of the armature windings 7 comprises or is formed from a conductive and non-superconductive winding, which may be made of copper or other materials (second case).

[0054] In one embodiment shown in figures 1 to 3 , 14 And 16 , the superconducting inductor coil 6 has an axial extent L, which surrounds both the rotors 2 (and thus also surrounds the superconducting axial magnetic flux barrier elements 3), and the armature(s) 5 in the tangential direction DC around the axis AX of rotation. This further reduces the demagnetizing magnetic field and increases the induction level. A single superconducting inductor coil 6 may be provided.

[0055] The superconducting axial magnetic flux barrier elements 3 may be cooled by a first cooling device, not shown, with circulation of cryogenic fluid, which may be for example helium, in particular in the embodiments of the figures 14 to 17 , described below. The superconducting inductor coil 6 can be cooled by a second cooling device, not shown, with circulation of cryogenic fluid, which can be for example helium, in particular in the embodiments of the figures 14 to 17 , described below. The cooling of the superconducting inductor coil 6 can be carried out by the same fluid circulating in series near the superconducting inductor coil 6 and the superconducting axial magnetic flux barrier elements 3 of the rotors 2, in particular in the embodiments of the figures 14 to 17, described below. When in addition the superconducting axial magnetic flux barrier elements 3 are superconducting pellets, these superconducting elements 3 have a higher temperature tolerance than the superconducting coil 6, and the fluid (helium) cools the superconducting inductor coil 6, before the superconducting pellets 3, in particular in the embodiments of the figures 14 to 17 , described below and in the first and second cases described below. The rotors 2 may be placed inside a cryogenic vacuum enclosure, for example according to one of the embodiments described below with reference to the figures 14 to 17 The vacuum ensures the absence of heat exchanges by convection between the surfaces of the enclosure and the rotors 2, and therefore thermal insulation, particularly in the embodiments of the figures 14 to 17 , described below.

[0056] The cryogenic cooling enclosures of the embodiments described below may contain the cooling fluid. This cooling fluid may be, for example, helium, or other. The cooling of the rotating axial magnetic flux barrier superconducting elements 3 may be carried out using a rotating collector circulating the helium inside copper channels in contact with these elements 3, in particular in the cryogenic cooling enclosure 12 of the embodiment of the Figures 14 and 15 , in the cryogenic cooling enclosure 13 of the embodiment of the figures 16 and 17 and in the cryogenic cooling enclosure 14 of the embodiment of the figures 16 and 17 , described below and in the fourth cryogenic cooling enclosure described below. The cryogenic cooling enclosures of the embodiments described below may operate at different temperatures from each other.

[0057] According to a first cooling case, the cryogenic cooling enclosures 11, 12, 13, 14 of the embodiments of the figures 14 to 17 can be arranged and / or connected, from the point of view of the circulation of the cooling fluid, so that the cooling fluid first cools the superconducting inductor coil 6, then the armature windings 7 of the armature 5, and then the rotors 2, 21, 22 and / or 23 (superconducting axial magnetic flux barrier elements 3), in the first case where the armature windings 7 comprise one (or more) superconducting armature windings 7. The order of cooling of the enclosures is from the coldest to the hottest, because the cooling fluid will heat up during cooling.

[0058] According to a second cooling case, the cryogenic cooling enclosures 11, 12, 13, 14 of the embodiments of the figures 14 to 17can be arranged and / or connected, from the point of view of the circulation of the cooling fluid, so that the cooling fluid first cools the superconducting inductor coil 6, then the rotors 2, 21, 22 and / or 23 (superconducting axial magnetic flux barrier elements 3), and then the armature windings 7 of the armature 5, in the second case where the armature windings 7 are formed of conductive, non-superconducting windings 7. The order of cooling of the enclosures is from the coldest to the hottest, because the cooling fluid will heat up during cooling.

[0059] In the second case, the armature windings 7 formed from non-superconducting, conductive windings 7 of the armature 5 will typically operate at higher temperatures (which may be of the order of 100 K) than in the first case of the armature windings 7 comprising one (or more) superconducting armature windings 7, which will have to be cooled below their critical temperature <100 K, for example to a temperature which may be 70 K or 50 K). The comparison made previously concerning the improvement in torque for a configuration according to the second comparative example compared to a configuration according to the first example according to the invention is accompanied by an improvement in the machine power of the machine, which is proportional only for a completely superconducting machine. In this case, the size of the cryogenic enclosure remains relatively the same.

[0060] In the case of Figures 12 and 13, the machine 1 comprises a cryogenic cooling enclosure 10, inside which are placed the rotors 2, the armature(s) 5 and the superconducting induction coil 6, in the case where the armature windings 7 are also superconducting.

[0061] In one embodiment shown in Figures 14 and 15, the superconducting inductor coil 6 is placed in a first cryogenic cooling enclosure 11 in the form of an annular ring around the axis AX of rotation. The superconducting inductor coil 6 is located in a first housing space 113 of the enclosure 13, located between a first outer wall 111 of the first enclosure 11 and a second annular inner wall 112 of the first enclosure 11, which delimit it radially. This first housing space 113 is distinct from a second space 114 located radially inside the second annular inner wall 11. In this second inner space 114 is placed a second cryogenic cooling enclosure 12, in which the rotors 2 and the armature(s) 5 are located in the case where the armature windings 7 are also superconducting.The second cryogenic cooling enclosure 12 has a circular cylindrical shape around the axis AX of rotation and is delimited radially by a third outer wall 121 located inside the second annular inner wall 112. Having several enclosures allows more efficient cooling: each enclosure is cooled to the temperature required by the parts located inside the enclosures.

[0062] According to one embodiment, the first cryogenic cooling enclosure 11 of the embodiment of the Figures 14 and 15comprises one (or more) first coolant introduction inlet connected to a source sending the coolant to it, and one (or more) first coolant ejection outlet. The first coolant ejection outlet or one (or more of or all of) the first coolant ejection outlets is connected to one (or more) second coolant introduction inlet of the second cryogenic cooling enclosure 12. The second cryogenic cooling enclosure 12 comprises one (or more) second coolant ejection outlet.

[0063] The (or one of the or more or all of the) second coolant introduction inlet of the second cryogenic cooling enclosure 12 may be closer to the armature(s) 5 than to the rotors 2, 21, 22 and / or 23, in the first case where the armature windings 7 comprise one (or more) superconducting armature windings 7, in order to implement the first cooling case mentioned above. The (or one of the or more or all of the) second coolant ejection outlet may be closer to the rotors 2, 21, 22 and / or 23 than to the armature(s) 5, in the first case where the armature windings 7 comprise one (or more) superconducting armature windings 7, in order to implement the first cooling case mentioned above.

[0064] The (or one of the or more or all of the) second coolant introduction inlet of the second cryogenic cooling enclosure 12 may be closer to the rotors 2, 21, 22 and / or 23 than to the armature(s) 5, in the second case where the armature windings 7 are formed of non-superconducting, conductive windings 7, in order to implement the second cooling case mentioned above. The (or one of the or more or all of the) second coolant ejection outlet may be closer to the armature 5 than to the rotors 2, 21, 22 and / or 23, in the second case where the armature windings 7 are formed of non-superconducting, conductive windings 7, in order to implement the second cooling case mentioned above.

[0065] In one embodiment shown in figures 16 and 17 , the first enclosure 11 is similar to that of the embodiment described above with reference to the Figures 14 and 15. In the second interior space 114 is placed a second cryogenic cooling enclosure 13, in which the first rotor 21 is placed without the armature 5, and a third cryogenic cooling enclosure 14, in which the second rotor 22 is placed without the armature 5, in the second case where the armature windings 7 are not superconducting. The second cryogenic cooling enclosure 13 has a circular cylindrical shape around the axis AX of rotation and is delimited radially by a third outer wall 131 located inside the second annular inner wall 112. The third cryogenic cooling enclosure 14 has a circular cylindrical shape around the axis AX of rotation and is delimited radially by a fourth outer wall 141 located inside the second annular inner wall 112.The third cryogenic cooling enclosure 14 is separate and located axially at a distance from the second cryogenic cooling enclosure 13. In the second interior space 114 and between the second cryogenic cooling enclosure 13 and the third cryogenic cooling enclosure 14 is the armature 5. For example, a cryogenic enclosure 13 or 14 is provided around each rotor 2 of the machine 1. The machine 1 may thus comprise N cryogenic cooling enclosures 13, 14, in which the N rotors 2 are respectively placed. The armature windings 7 may be inserted between the transverse outer surfaces of two different enclosures 13 and 14, for example according to the embodiment described below with reference to the . Figure 11. In the first case where the armature windings 7 comprise one (or more) superconducting armature windings 7, each armature 5 is placed in a fourth cryogenic cooling enclosure, which is located between the second cryogenic cooling enclosure 13 and the third cryogenic cooling enclosure 14, which has a circular cylindrical shape around the axis AX of rotation and which is delimited radially by a fourth outer wall located inside the second annular inner wall 112. Having several enclosures allows more efficient cooling: each enclosure is cooled to the temperature required by the parts located inside the enclosures.

[0066] According to one embodiment, the first cryogenic cooling enclosure 11 of the embodiment of the figures 16 and 17comprises one (or more) first inlet for introducing the cooling fluid connected to a source sending the cooling fluid to it, and one (or more) first outlet for ejecting the cooling fluid. The second cryogenic cooling enclosure 13 comprises one (or more) second inlet for introducing the cooling fluid and one (or more) second outlet for ejecting the cooling fluid. The third cryogenic cooling enclosure 14 comprises one (or more) third inlet for introducing the cooling fluid and one (or more) third outlet for ejecting the cooling fluid. In the first case, the fourth cryogenic cooling enclosure comprises one (or more) fourth inlet for introducing the cooling fluid and one (or more) fourth outlet for ejecting the cooling fluid.

[0067] In the first case where the armature windings 7 comprise one (or more) superconducting armature windings 7, in order to implement the first cooling case mentioned above, the (or one of the or more or all of the) first outlet for ejecting the cooling fluid from the first cryogenic enclosure 11 for cooling the superconducting inductor coil 6 is connected to the (or one of the or more or all of the) fourth inlet for introducing the cooling fluid from the fourth cryogenic cooling enclosure (armature 5).The (or one of the or several or all of the) fourth coolant ejection outlet of the fourth cryogenic cooling enclosure (armature 5) is connected to the (or several or all of the) second coolant introduction inlet of the second cryogenic cooling enclosure 13 and to the (or one of the or several or all of the) third coolant introduction inlet of the third cryogenic cooling enclosure 14, in the first case where the armature windings 7 comprise one (or several) superconducting armature windings 7, in order to implement the first cooling case mentioned above.

[0068] In the second case where the armature windings 7 are formed of non-superconducting, conductive windings 7, in order to implement the second cooling case mentioned above, the (or one of the or several of the or all of the) first cooling fluid ejection outlet is connected to the (or one of the or several of the or all of the) second cooling fluid introduction inlet of the second cooling cryogenic enclosure 13 and to the (or one of the or several of the or all of the) third cooling fluid introduction inlet of the third cooling cryogenic enclosure 14. In the second case, forced air or liquid cooling devices may be envisaged to cool the armature windings 7.For example, a crown on the radial outer and / or inner peripheries of the armature windings 7 lends itself well to a cooling device by circulation of a liquid in the second case.

[0069] In the embodiment of the Figure 11 , the armature windings 7 of an armature 5 can be fixed on a cryostat cap 35 (for example made of ceramic) of the enclosure 13 and / or 14 in the form of a ring around the axis AX, a transverse face of which comprises notches 36 in which the armature windings 7 are respectively mounted. This system can in particular make it possible to serve as a mechanical support for the coils in the absence of a magnetic yoke (ironless machine). Channels and fins can be integrated into the cryostat cap 34 in order to improve cooling.

[0070] Machine 1 according to the invention, and particularly that according to the embodiment described above with N ≥ 3 rotors and N-1 ≥ 2 armatures with reference to the Figure 2 , called multiple rotor stacks 2, lends itself well to very high power machines with volume constraints (e.g., maximum outer radius), or to fully superconducting topologies, because the armatures and rotors can all be placed inside a single cryogenic enclosure.

[0071] In the axial flux electric machine 1, the addition of a stack according to the Figure 2increases the power and also the mass. The power density of the machine is increased. In fact, the stack of rotors 2 leads to an increase in the length L of the inductor coil 6 (operation in generator mode). This lengthening of the coil 6 results in the reduction of the demagnetizing magnetic field H d , which increases the level of induction at the heart of the machine 1 and therefore its power density.

[0072] The magnetic induction created by a solenoid S carrying a current density J can be resolved by an Amperian or Colombian approach, with reference to the figure 9 The demagnetizing field is typically Coulombic, the surface magnetic charges are written: σ s r = μ 0 J R 2 − R 1 pour 0 < r < R 1 σ s r = μ 0 J R 2 − r pour R 1 < r < R 2 σ s r = 0 pour r > R 2

[0073] For a distribution of charges spread over a surface Σ, the demagnetizing magnetic field H d is given at a point M by: H d M = ∬ Σ σ s 4 πε 0 PM d 2 S where P is a point on the surface Σ. In the absence of an external magnetic field source, the total magnetic field vector H is simply written as: H = H d

[0074] Finally, the expression of the induction vector B is: B = μ 0 H + M = μ 0 H d + M

[0075] Vectorially the demagnetizing magnetic field H d is opposed to the magnetization M of the solenoid, which explains the demagnetizing character. By increasing the length L of the superconducting coil 6, the distance PM of the above expression of the demagnetizing magnetic field H d increases and decreases the demagnetizing magnetic field H d . Thus in view of the expression of B, the total induction increases and therefore the torque / power set of the machine also. A coefficient k can be used to represent the evolution of the induction as a function of the number of rotors 2 in the machine 1 according to the invention, such that: k = B zN B z 1 where B z1 is the induction for an axial flux machine comprising a single rotor and a single armature and B zN the induction of a machine 1 according to the invention comprising N rotors. The induction is proportional to this coefficient k. The increase in torque and power of the machine 1 is also proportional to this coefficient k.

[0076] There Figure 10 represents the evolution of the coefficient k (and therefore of the induction) as a function of the number (N-1) of stacks of rotors 2. This curve C5 was obtained by the interpolation of results obtained for finite element calculations of the machine 1 according to the invention comprising different numbers N-1 of stacks of rotors 2. It can be seen that the coefficient k and the power density of the machine 1 are doubled for N=3 (point P1 on the curve C5) and more than tripled for N=9 (point P2 on the curve C5). The curve C5 was determined to be for example of the form k = B zN / B z 1 = A . N . F D − C

[0077] In the aforementioned example of machine 1 according to the invention having the aforementioned parameters, A=9.03T -1< .m -1< , D=0.1372, C=5.15 and F=0.06m. Of course, the coefficients A, D, C and F may be other for other values ​​of the parameters of the machine 1 according to the invention.

[0078] The invention can be used for electrical machines 1 comprising flux barriers (superconducting solid pellets or superconducting short-circuited ribbons).

[0079] The technical field of use of the invention falls within the context of aircraft electrification. Preparing for the installation of increasingly powerful electrical systems for electric or hybrid propulsion requires the design of electric motors capable of competing with, exceeding or improving the performance of thermal engines. The electric aircraft will require electric machine power densities greater than 20 kW / kg. The use of superconducting materials represents a key tool for achieving these power densities. The invention can be used for electric machines comprising flux barriers 3 (superconducting massive pellets or superconducting short-circuited ribbons). The invention applies to fully superconducting machines (superconducting armature 3 and inductor 6) but also to partially superconducting machines (superconducting armature 3 or inductor 6).

[0080] The rotating electrical machine 1 may be part of an aircraft and have the at least two outer electrical terminals of the armature windings 7 which are connected to an electricity consuming member or to an electricity generating member. This consuming or generating member may be located for example in one or more propulsion turbomachines of the aircraft. In the case where the rotating electrical machine 1 operates in electricity generating mode, the rotating electrical machine 1 may have the at least two outer electrical terminals of the armature windings 7 which are connected to an electricity consuming member or to a connection circuit (which may be for example with controllable switching) itself connected by electrical conductors to an electricity consuming member, so that the electricity generating rotating electrical machine 1 can supply electricity to this consuming member.In the case where the rotating electrical machine 1 operates in motor mode, the rotating electrical machine 1 may have the at least two outer electrical terminals of the armature windings 7 connected to the electricity generating member or to a connection circuit (which may be for example with controllable switching) itself connected by electrical conductors to the electricity generating member, so that the rotating electrical machine 1 can be supplied with electricity by this generating member. Of course, the embodiments, characteristics, possibilities and examples described above may be combined with each other or be selected independently of each other.

Claims

1. A rotating electric machine (1), comprising: at least one rotor (2) comprising a set of superconducting axial magnetic flux barrier elements (3) distributed in a plane perpendicular to the axis of rotation (AX) in a tangential direction (DC) about the axis of rotation (AX), said superconducting axial magnetic flux barrier elements (3) being spaced by axial magnetic flux passage areas (4) distributed in the tangential direction (DC) about the axis of rotation (AX), at least one armature (5), comprising armature windings (7) distributed in the tangential direction (DC) about the axis of rotation (AX), at least one superconducting inductor coil (6) surrounding the superconducting axial magnetic flux barrier elements (3) and the at least one armature (5) in the tangential direction (DC) about the axis of rotation (AX), the at least one superconducting inductor coil (6) being able to induce an axial magnetic field directed along the axis of rotation (AX), the at least one rotor (2) being rotatably mounted on the axis of rotation (AX) with respect to the armature (5) and to the at least one inductor coil (6), the machine (1) comprising as a rotor (2, 21, 22, 23) at least one first rotor (21) and at least one second rotor (22, 23), the at least one first rotor (21) and the at least one second rotor (22, 23) being spaced from each other along the axis of rotation (AX), the at least one armature (5) being positioned between the at least one first rotor (21) and the at least one second rotor (22, 23), the superconducting axial magnetic flux barrier elements (3) of the at least one first rotor (21) being coaxial at least partly with the superconducting axial magnetic flux barrier elements (3) of the at least one second rotor (22, 23), the axial magnetic flux passage areas (4) of the at least one first rotor (21) being coaxial at least partly with the axial magnetic flux passage areas (4) of the at least one second rotor (22, 23), the rotating electric machine (1) comprising a first cryogenic cooling enclosure (11), which has an annular shape about the axis of rotation (AX) and which is delimited radially by a first external wall (111), characterized in that the first cryogenic cooling enclosure (11) is delimited radially by a second internal annular wall (112), the at least one superconducting inductor coil (6) being located in the first cryogenic cooling enclosure (11) between the first external wall (111) and the second internal annular wall (112), the machine comprising a second cryogenic cooling enclosure (12), which has a circular cylindrical shape about the axis of rotation (AX) and which is delimited radially by a third external wall (121) located inside the second internal annular wall (112), the rotors (2, 21, 22, 23) and the at least one armature (5) being located in the second cryogenic cooling enclosure (12).

2. A rotating electric machine (1), comprising: at least one rotor (2) comprising a set of superconducting axial magnetic flux barrier elements (3) distributed in a plane perpendicular to the axis of rotation (AX) in a tangential direction (DC) about the axis of rotation (AX), said superconducting axial magnetic flux barrier elements (3) being spaced by axial magnetic flux passage areas (4) distributed in the tangential direction (DC) about the axis of rotation (AX), at least one armature (5), comprising armature windings (7) distributed in the tangential direction (DC) about the axis of rotation (AX), at least one superconducting inductor coil (6) surrounding the superconducting axial magnetic flux barrier elements (3) and the at least one armature (5) in the tangential direction (DC) about the axis of rotation (AX), the at least one superconducting inductor coil (6) being able to induce an axial magnetic field directed along the axis of rotation (AX), the at least one rotor (2) being rotatably mounted on the axis of rotation (AX) with respect to the armature (5) and to the at least one inductor coil (6), the machine (1) comprising as a rotor (2, 21, 22, 23) at least one first rotor (21) and at least one second rotor (22, 23), the at least one first rotor (21) and the at least one second rotor (22, 23) being spaced from each other along the axis of rotation (AX), the at least one armature (5) being positioned between the at least one first rotor (21) and the at least one second rotor (22, 23), the superconducting axial magnetic flux barrier elements (3) of the at least one first rotor (21) being coaxial at least partly with the superconducting axial magnetic flux barrier elements (3) of the at least one second rotor (22, 23), the axial magnetic flux passage areas (4) of the at least one first rotor (21) being coaxial at least partly with the axial magnetic flux passage areas (4) of the at least one second rotor (22, 23), the rotating electric machine comprising a first cryogenic cooling enclosure (11), which has an annular shape about the axis of rotation (AX) and which is delimited radially by a first external wall (111), characterized in that the cryogenic cooling enclosure (11) which is delimited radially by a second internal annular wall (112), the at least one superconducting inductor coil (6) being located in the first cryogenic cooling enclosure (11) between the first external wall (111) and the second internal annular wall (112), the machine comprising at least one second cryogenic cooling enclosure (13), which has a circular cylindrical shape about the axis of rotation (AX) and which is delimited radially by a third external wall (131) located inside the second internal annular wall (112), the at least one first rotor (21) being located in the second cryogenic cooling enclosure (13), the machine comprising at least one third cryogenic cooling enclosure (14), which has a circular cylindrical shape about the axis of rotation (AX), which is located axially at a distance from the second cryogenic cooling enclosure (13) and which is delimited radially by a fourth external wall (141) located inside the second internal annular wall (112), the at least one second rotor (22, 23) being located in the third cryogenic cooling enclosure (14), the at least one armature (5) being located between the second cryogenic cooling enclosure (13) and the third cryogenic cooling enclosure (14).

3. The rotating electric machine according to claim 1 or 2, characterized in that the at least one second rotor (22) comprises an armature (51, 52) on either side.

4. The rotating electric machine according to claim 3, characterized in that it comprises N rotors comprising on either side of each of the rotors an armature, N being a natural number greater than or equal to 2.

5. The rotating electric machine according to any one of the preceding claims, characterized in that it comprises N armatures comprising on either side of each of the armatures a rotor, N being a natural integer greater than or equal to 2.

6. The rotating electric machine according to any one of the preceding claims, characterized in that the superconducting axial magnetic flux barrier elements (3) of the at least one first rotor (21) are aligned along the axis of rotation (AX) with the superconducting axial magnetic flux barrier elements (3) of the at least one second rotor (22, 23), and the axial magnetic flux passage areas (4) of the at least one first rotor (21) are aligned along the axis of rotation (AX) with the axial magnetic flux passage areas (4) of the at least one second rotor (22, 23).

7. The rotating electric machine according to any one of claims 1 and 3 to 6, when they depend on claim 1, characterized in that the armature windings (7) comprise at least one superconducting armature winding.

8. The rotating electric machine according to any one of claims 2 and 3 to 6, when they depend on claim 2, characterized in that the armature windings (7) comprise at least one conductive winding not superconducting.

9. The rotating electric machine according to any one of the preceding claims, characterized in that the at least one superconducting inductor coil (6) has an axial extent (L), which surrounds the plurality of the rotors (2, 21, 22, 23) and the at least one armature (5) in the tangential direction (DC) about the axis of rotation (AX).

10. The rotating electric machine according to claim 7, characterized in that the machine comprises a single superconducting inductor coil (6).

11. The rotating electric machine according to any one of the preceding claims, characterized in that at least one of the superconducting axial magnetic flux barrier elements (3) comprises at least one full superconducting axial magnetic flux barrier pad.

12. The rotating electric machine according to any one of the preceding claims, characterized in that at least one of the superconducting axial magnetic flux barrier elements (3) comprises at least one superconducting axial magnetic flux barrier loop.

13. The rotating electric machine according to claim 2 or any one of claims 3 to 12, when they depend on claim 2, characterized in that the armature windings (7) are fixed on a cryostat cap (35) of the second cryogenic cooling enclosure (13) and / or of the third cryogenic cooling enclosure (14) in the form of a ring about the axis (AX), one transverse face of the cryostat cap (35) comprises notches (36) in which the armature windings are respectively mounted (7).

14. An aircraft, comprising an electricity-consuming member or an electricity-generating member and a rotating electric machine (1) according to any one of the preceding claims, which is connected to a circuit for connection to the electricity-consuming member or to the electricity-generating member to allow supplying it or providing it with electricity.