Electric machine rotor with flux barriers per magnetic pole

Abstract

The invention relates to a rotor for an electric machine, the rotor having a rotor body (1) and pairs of magnetic poles, each magnetic pole being composed of at least two flux barriers - an internal flux barrier comprising two inclined recesses (6) arranged on either side of a central recess (5), - an external flux barrier comprising two inclined recesses (7) arranged between the central recess (5) of the internal flux barrier and the outer edge of the body (1) of the rotor, and a permanent magnet positioned in at least one recess (5, 6, 7) of each of the two flux barriers, and two additional recesses (20) arranged between the recesses (7) of the external flux barrier and the outer edge of the body (1) of the rotor in order to modify the trajectory of the magnetic fluxes emitted by the magnets.

Description

[0001] ELECTRIC MACHINE ROTOR WITH FLUID BARRIERS VIA MAGNETIC POLE

[0002] technical field

[0003] The present invention relates to a rotating synchronous-reluctant electrical machine (assisted by permanent magnets), and more particularly concerns the particular architecture of a rotor of such a machine.

[0004] Generally, such an electrical machine consists of a stator and a rotor arranged coaxially one inside the other.

[0005] The rotor consists of a rotor body with a stack of laminations placed on a rotor shaft. These laminations include housings for permanent magnets and perforations to create flux barriers that direct the magnetic flux from the magnets radially towards the stator, promoting the creation of a reluctance torque, and lightening the rotor to reduce the centrifugal forces that the lamination stack must withstand.

[0006] This rotor is usually housed inside a stator which carries electrical windings configured to generate a rotating magnetic field to drive the rotor into rotation.

[0007] Previous technique

[0008] As described in particular in patent application W02020 / 020580 and in patent application WO 2022 / 0128541, the rotor of a synchronous reluctance machine comprises a plurality of axial recesses which pass through the laminations from one side to the other.

[0009] The rotor design described in patent application W02020 / 020580 proposes a first series of axial recesses, arranged radially one above the other and spaced apart, which form housings for magnetic flux generators, in this case, permanent magnets in the form of rectangular bars. The second series of recesses consists of perforations with an inclined radial direction, extending from these housings to the vicinity of the edges of the laminations, near the air gap. The inclined perforations are arranged symmetrically with respect to the magnet housings so as to form, each time, a geometric figure approximately V-shaped with a flat bottom, where the flat bottom is formed by the magnet housing and the inclined arms of this V are formed by the perforations. This creates flux barriers formed by the perforations.The magnetic flux from the permanent magnets can then only pass through the solid parts between the perforations. These solid parts are made of a ferromagnetic material.

[0010] The rotor design described in patent application WO 2022 / 0128541 is an improvement on the previous design, proposing a rotor body within which flux barriers are formed, with an external and an internal flux barrier. The internal flux barrier is substantially U-shaped, and the external flux barrier is substantially V-shaped, each flux barrier comprising at least one radial magnetic bridge and one tangential magnetic bridge. This configuration of the flux barriers allows for good torque and power performance, while limiting mechanical stresses, particularly to permit applications of the electric machine over a wide range of rotational speeds, including high speeds (e.g., 20,000 rpm or 30,000 rpm).

[0011] The present invention aims to further improve the design of this type of rotor with internal and external flux barriers, in order to increase its performance even further. In particular, it aims to increase the efficiency of the electric machine incorporating the rotor at low load and high speed, while ensuring the control and reduction of noise and vibrations generated by the electric machine during its operation.

[0012] Summary of the invention

[0013] The invention relates firstly to a rotor for an electric machine, said rotor comprising a rotor body formed by a stack of laminations (preferably intended to be placed on a shaft called the rotor shaft, which is also part of the electric machine), and a plurality of pairs of magnetic poles, each magnetic pole being composed of at least two flux barriers, in particular two flux barriers, of which

[0014] - an internal flow barrier comprising two recesses inclined relative to each other and arranged on either side of a central recess, said central recess being perpendicular to a radius of the rotor,

[0015] - an external flow barrier comprising two recesses inclined relative to each other and arranged, on either side of said radius, between the central recess of the internal flow barrier and the outer edge of the rotor body,

[0016] - and at least one permanent magnet positioned in at least one recess of each of said at least two flux barriers.

[0017] At least one of the magnetic poles, in particular each magnetic pole, includes two additional recesses arranged between the recesses of the external flux barrier and the outer edge of the rotor body to modify the path of the magnetic fluxes emitted by said permanent magnets in the rotor.

[0018] As demonstrated later with examples, the electric machine incorporating a rotor thus modified by these additional recesses is more efficient: it allows the no-load voltage peak to be lowered while maintaining a high effective voltage value, which guarantees better performance in both torque / power and maximum speed ramp-up of the electric machine. Preferably, each magnetic pole consists of only two flux barriers.

[0019] The additional recesses provided by the invention effectively make the two-flow barrier system as efficient as if it were equipped with three flow barriers.

[0020] According to one embodiment, the additional recesses each have, for one or each magnetic pole, a circular or oval or ovoid shape, or oblong, or triangular or polygonal shape, in particular with four or more sides, in particular with rounded edges, in particular a square, a trapezoid, a rhombus, a rectangle.

[0021] Preferably they are of a shape that is approximately or exactly triangular or trapezoidal, with possibly rounded vertices.

[0022] In the case of a substantially trapezoidal shape, preferably the largest base of the trapezoid is oriented towards the nearest recess in the external flow barrier. It may at least partially run along the edge of the recess in question.

[0023] The two additional recesses, for one or at least one or each magnetic pole, may have the same shape or a different shape, the same dimensions, or different dimensions.

[0024] The two additional recesses, for one or at least one or each magnetic pole, may be arranged on either side of said radius, in particular inclined to one another, and preferably arranged symmetrically with respect to said radius.

[0025] The additional recesses across the rotor can together represent 0.25% to 5% of the rotor cross-sectional area.

[0026] At least one of the two additional recesses, for one or at least one or each magnetic pole, may have a portion of its edge that runs along the outer edge of the nearest inclined recess of the external flux barrier. In this case, preferably, the portion of the edge of the additional recess(es) that runs along the outer edge of the nearest inclined recess of the external flux barrier is located at a distance of between 0.35 mm and 2 mm from said outer edge.

[0027] In this case, preferably, the edge of the additional recess that runs along the outer edge of the inclined recess of the external flow barrier and said outer edge are substantially straight and are inclined to each other at an angle of tangency between 0° (they are then parallel to each other) and 15° at most.

[0028] At least one of the two additional recesses for one or at least one or each magnetic pole, may have a portion of its edge running along the outer edge of the rotor body.

[0029] In this case, preferably, the part of the edge of the additional recess(s) which runs along the outer edge of the rotor is distanced from said outer edge by a distance of between 0.35 mm and 1 mm.

[0030] According to one embodiment, the distance between the portion of the edge of the additional recess(s) that runs along the outer edge of the inclined recess of the nearest external flow barrier and said outer edge is between one and two times the distance between the portion of the edge of the additional recess(s) that runs along the outer edge of the rotor body and said outer edge.

[0031] The two additional recesses, for one or at least one or each magnetic pole, may be inclined relative to each other, and their opening angle there is obtuse or right, and preferably identical or close to the opening angle B of the inclined recesses of the external flux barrier.

[0032] At least one of the two additional recesses for one or at least one or each magnetic pole, may be disposed at a distance from and along a portion of the outer edge of the inclined recess of the external flux barrier, in particular over at least 10% to 50% of the length of said outer edge.

[0033] One or at least one or each magnetic pole may also include at least one relief recess between the recesses of the external flux barrier and the outer edge of the rotor body. This relief recess preferably has a substantially triangular shape. The two additional recesses may be arranged on either side of this relief recess. The invention also relates to any electrical machine comprising a stator and a rotor as described above, said rotor being housed inside said stator. It may also include a rotating shaft on which the rotor is mounted.

[0034] Said stator may comprise a plurality of radial notches arranged circumferentially along said stator.

[0035] The said electrical machine may be a synchronous-reluctant electrical machine assisted by permanent magnets.

[0036] According to one embodiment, for each magnetic pole, a permanent magnet, preferably a single permanent magnet, is positioned in said central recess of said internal flux barrier.

[0037] According to one implementation, for each magnetic pole, a permanent magnet, preferably a single permanent magnet, is positioned in each inclined recess of said internal flux barrier.

[0038] According to one embodiment, for each magnetic pole, a permanent magnet, preferably a single permanent magnet, is positioned in each inclined recess of said external flux barrier.

[0039] According to one characteristic, for each magnetic pole, said inclined recesses of said internal and / or external flux barriers are symmetric with respect to said perpendicular radius of said central recess of said internal flux barrier.

[0040] Advantageously, two consecutive magnetic poles are asymmetrical.

[0041] According to one embodiment, the opening angle of the inclined recesses of said internal flow barrier is strictly less than the opening angle of the inclined recesses of said external flow barrier, the opening angle of said inclined recesses of said internal or external flow barriers being defined by the angle formed between two straight lines, each straight line passing through the midpoint of two sides of an inclined recess, said two sides of the inclined recess being the one facing the periphery of the rotor and the one facing the center of the rotor.

[0042] Advantageously, the opening angle of the inclined recesses of said flow barrier is acute.

[0043] In one aspect, the opening angle of the inclined recesses of said external flux barrier is obtuse or right. In one embodiment, each magnetic pole comprises a plurality of permanent magnets arranged in said recesses of said flux barriers, said permanent magnets being of identical dimensions.

[0044] According to an optional embodiment, at least one of the magnetic poles, in particular each magnetic pole, has a relief recess between said external flux barrier and the periphery of said rotor body, preferably said relief recess has a substantially triangular shape, preferably two sides of said triangular shape are substantially parallel to said inclined recesses of said external flux barrier.

[0045] Advantageously, the said number of magnetic pole pairs is between 2 and 9, preferably between 3 and 6, and is preferably 4.

[0046] Advantageously, said at least one permanent magnet has a rectangular cross-section.

[0047] Other features and advantages of the device and method according to the invention will become apparent from the following description of non-limiting examples of embodiments, with reference to the figures attached and described below.

[0048] List of figures

[0049] Figure 1a represents a sheet of a rotor according to a comparative example corresponding to a prior design in accordance with the teaching of patent application WO2022 / 128541.

[0050] Figure 1b represents the geometric parameterization of the rotor in Figure 1a.

[0051] Figure 2 represents a sheet of a rotor according to a first embodiment of the invention.

[0052] Figure 3 represents a sheet of a rotor according to a second embodiment of the invention.

[0053] Figure 4 represents a graph of the no-load back electromotive force (induced voltage) between phases (corresponding to the "Phase-to-phase BEMF" according to the English expression) as a function of the position of the rotor in mechanical angle, with, on the abscissa, the position of the rotor expressed in degrees (°) and on the ordinate the voltage expressed in Volts (V), for the rotor according to a comparative example 2 (according to figure 16) and for a rotor according to example 1 of the invention (according to figure 2), for a rotational speed of 14000 rpm.

[0054] Figure 5 represents a harmonic order graph, i.e. the Fourier series decomposition of the induced open-circuit voltage between phases, with the harmonics on the abscissa and the voltage expressed in volts (V) on the ordinate, with the rotor according to comparative example 2 (figure 16) and a rotor according to example 1 of the invention (figure 2).

[0055] Figure 6 shows a graph of the maximum values ​​of the no-load induced voltage between phases (corresponding to the "Phase-to-phase Peak BEMF" as a function of the motor speed, with the rotor speed in revolutions per minute (rpm) on the x-axis and the voltage expressed in volts (V) on the y-axis, with the rotor according to comparative example 2 (figure 16) and a rotor according to example 1 of the invention (figure 2).

[0056] Figure 7 represents a graph of the maximum effective values ​​of the no-load induced voltage between phases (corresponding to the "Phase-to-phase RMS BEMF" according to the English expression) as a function of the motor speed, with the rotor speed in revolutions per minute (rpm) on the abscissa and the voltage expressed in volts (V) on the ordinate, with the rotor according to comparative example 2 (figure 16) and a rotor according to example 1 of the invention (figure 2).

[0057] Figure 8 represents a graph of the mechanical torque envelope under load of the electric machine expressed in Newton meters (Nm) as a function of the rotational speed expressed in revolutions per minute (rpm), for the machine equipped with the rotor according to comparative example 2 (figure 16) and the rotor according to example 1 of the invention (figure 2).

[0058] Figure 9 represents a graph of the mechanical power envelope under load (expressed in watts (W) as a function of the rotational speed expressed in revolutions per minute (rpm), for the machine equipped with the rotor according to comparative example 2 (figure 16) and the rotor according to example 1 of the invention (figure 2).

[0059] Figure 10 shows two graphs side by side,

[0060] - with the graph on the right representing the electromagnetic torque ripples (“EM Torque ripple” in English) as a function of the maximum current (“Ipeak” expressed in amperes (A)) for the machine equipped with the rotor according to comparative example 2 (figure 16) and the rotor according to example 1 of the invention (figure 2)., - and with the graph on the left, representing the average electromagnetic torque (“EM Mean Torque” in English) expressed in Nm, as a function of the maximum current (“Ipeak” expressed in amperes (A)) for the machine equipped with the rotor according to comparative example 2 (figure 16) and the rotor according to example 1 of the invention (figure 2).

[0061] Figure 11 represents a graph comparing the efficiency of two electrical machines as a function of the speed (rpm) of the machine and the mechanical torque (in Nm) for the machine equipped with the rotor according to comparative example 2 (figure 16) and the rotor according to example 1 of the invention (figure 2).

[0062] Figure 12 represents a graph with the mechanical torque envelope (in Nm) as a function of the wheel rotation speed expressed in revolutions per minute (rpm), for a motor vehicle equipped with the electric machine equipped with the rotor according to comparative example 2 (figure 16) and the rotor according to example 1 of the invention (figure 2).

[0063] Figure 13 represents a graph with the mechanical power envelope (W) as a function of the wheel rotation speed expressed in revolutions per minute (rpm), for a motor vehicle equipped with the electric machine equipped with the rotor according to comparative example 2 (figure 16) and the rotor according to example 1 of the invention (figure 2).

[0064] Figure 14 represents a sheet of a rotor according to a third embodiment (example 3) of the invention.

[0065] The figures representing the rotors, in particular, are schematic for ease of reading and do not necessarily represent a portion of the rotor in its operating position within the electrical machine. The same reference numerals designate the same element / object from one figure to another.

[0066] Figure 15 represents, on the left, the distribution of the flow lines according to the comparative example of Figure 1 with the V-shaped barrier and the U-shaped barrier, and, on the right, the same area of ​​the rotor but this time according to the invention, as shown in Figure 2, with the two additional recesses.

[0067] Figure 16 represents a sheet of a rotor according to a second comparative example (comparative example 2).

[0068] A series of examples will be described with the figures: Comparative example 1 is shown in figure 1. Comparative example 2 is shown in figure 16.

[0069] Example 1 according to the invention is shown in Figure 2.

[0070] Example 2 according to the invention is shown in Figure 3.

[0071] Example 3 according to the invention is shown in Figure 14.

[0072] Description of the implementation methods

[0073] The present invention relates to a rotor for an electrical machine, in particular a synchronous reluctance machine assisted by permanent magnets. Furthermore, the present invention relates to an electrical machine comprising a rotor according to the invention and a stator, the rotor being arranged coaxially within the stator. The machine may also include the rotor shaft.

[0074] The present invention is an improvement on the rotor design described in the aforementioned patent application WO2022 / 128541, to which reference may be made for further details. Embodiments of the rotor design according to that application are described below, a design which the invention has supplemented / modified by adding so-called additional recesses. These recesses are not intended to house magnets, but rather to modify, by creating these air pockets, the trajectory of the magnet flux within the rotor, thereby achieving multiple advantages described and demonstrated later.

[0075] The rotor for an electric machine according to patent application WO2022 / 128541 has features also used in the present invention, namely:

[0076] - a rotor body formed by a stack of sheet metal, preferably the rotor body can be placed on a rotor shaft,

[0077] - a plurality of pairs of magnetic poles, each magnetic pole is composed

[0078] - of two flow barriers: an external flow barrier, which is closer to the periphery of the rotor, and an internal flow barrier, which is closer to the center of the rotor, the flow barriers being formed by a plurality of axial recesses (the axial direction being the axial direction of the rotor),

[0079] - at least one permanent magnet positioned in one of the axial recesses of said rotor body.

[0080] The at least one permanent magnet generates a magnetic flux, enabling the rotor to rotate by creating a rotating magnetic field that can be generated by the stator. Flux barriers guide the magnetic field generated by the rotor and the at least one permanent magnet towards the air gap (the space between the rotor's periphery and the stator), thereby limiting magnetic flux leakage and increasing the performance (particularly torque and power) of the electric machine.

[0081] A pair of magnetic poles comprises two magnetic poles of opposite polarities. For each magnetic pole, the internal flux barrier consists of three recesses: two inclined (lateral) recesses positioned and spaced on either side of a central recess, which is perpendicular to a radius of the rotor. The recesses of the internal flux barrier form approximately a U-shape (along a cross-section to the rotor axis, corresponding to the plane of a sheet metal forming the rotor body), with the bottom of the U formed by the central recess, and the opposite segments of the U formed by the inclined recesses. Furthermore, the two inclined recesses are spaced away from the periphery of the rotor. In other words, there is a magnetic bridge (a material bridge) between the inclined recesses and the central recess, and there is a magnetic bridge (a material bridge) between the inclined recesses and the periphery of the rotor.The spacing achieved by these magnetic bridges ensures good mechanical strength of the rotor body while maintaining its magnetic properties. Tangential magnetic bridges (between the inclined recesses and the rotor periphery) create local saturation, allowing the magnetic flux generated by at least one permanent magnet to be directed towards the air gap of the electric machine. Radial magnetic bridges (between the inclined recesses and the central recess) improve the mechanical strength of the electric machine at high speeds (e.g., 20,000, 30,000 rpm). This advantage can also be leveraged for low-speed applications (e.g., 10,000 rpm) to optimize the bridges and maximize torque density. The recesses are inclined relative to the radius perpendicular to the central recess.In other words, each inclined recess is oriented so as to form an angle with respect to the ray perpendicular to the central recess, this angle being non-zero and not a right angle (in other words, the inclined recesses are neither parallel nor perpendicular to the ray perpendicular to the central recess).

[0082] Furthermore, for each magnetic pole, the external flux barrier consists of two recesses: two recesses spaced apart and inclined (lateral) with respect to the radius perpendicular to the central recess of the internal flux barrier of the magnetic pole. The recesses of the external flux barrier essentially form a V (along a cross-section to the rotor axis, which corresponds to the plane of a sheet constituting the rotor body), each inclined recess forming a segment of the V. Moreover, the two inclined recesses are spaced away from the periphery of the rotor. In other words, there is a magnetic bridge (a material bridge) between the inclined recesses, and there is a magnetic bridge (a material bridge) between the inclined recesses and the periphery of the rotor.

[0083] The spacing achieved by this material bridge ensures good mechanical strength of the rotor body while maintaining its magnetic properties. Tangential magnetic bridges (between the inclined recesses and the rotor periphery) create local saturation, allowing the magnetic flux generated by at least one permanent magnet to be directed towards the air gap. Radial magnetic bridges (between the inclined recesses) improve the mechanical strength of the electric machine at high speeds (e.g., 20,000, 30,000 rpm). This advantage can also be leveraged for low-speed applications (e.g., 10,000 rpm) to optimize the bridges and maximize torque density.The angle formed by each inclined recess with respect to the ray perpendicular to the central recess is non-zero and not a right angle (in other words, the inclined recesses are neither parallel nor perpendicular to the ray perpendicular to the central recess).

[0084] In one embodiment, the central recess of the internal flow barrier may have (in the transverse plane of the rotor) a length substantially identical to the length of the lateral recesses of the internal flow barrier. In other words, the length of the central recess of the internal flow barrier may be between 75 and 125% of the length of the lateral recesses of the internal flow barrier.

[0085] The laminations can be made of ferromagnetic material to guide the magnetic flux of the permanent magnets and the stator. The flux barrier recesses can be created by perforations in the stacked laminations forming the rotor body, and the magnetic bridges are formed by the lamination itself.

[0086] At least one permanent magnet may have a rectangular parallelepiped shape, one dimension of which is parallel to the rotor axis. In particular, in a cross-section across the rotor axis, at least one permanent magnet may have a rectangular shape. Preferably, all permanent magnets may have a rectangular parallelepiped shape. Alternatively, at least one permanent magnet may have other shapes, in particular a parallelogram shape in a cross-section across the rotor axis, for example, substantially a trapezoidal shape.

[0087] According to another alternative, in which permanent magnets can be plasto-magnets (flexible magnets), the permanent magnet can have a parallelogram shape in cross-section, or a curved shape. One example is the plasto-ferrite material, which is composed of ferrite powder mixed with a thermoplastic binder. This compound combines the magnetic properties of ferrite with the mechanical properties of thermoplastic.

[0088] The recesses may preferably have a shape compatible with the shape of at least one permanent magnet. For example, the recess may have a substantially parallelogram shape (in cross-section), such as a trapezoid or rectangle, or a curve (particularly in the case of a plasto-magnet). The recesses may also include additional shapes at at least one, preferably both, ends of the recess in the rotor cross-section. These additional shapes may be circular, rectangular, oval, curved, L-shaped, or other. These additional shapes of the recesses, when a permanent magnet is provided in the recess, allow for limiting magnetic flux losses and channeling the magnetic flux towards the air gap of the electric machine, thus limiting mechanical stress in the magnetic bridges.These additional shapes can be filled with a material such as resin, particularly to ensure the stability of the permanent magnets. In the embodiment where the magnet is in the form of a plastic magnet, the recesses may preferably not include additional shapes at the ends.

[0089] For each magnetic pole, a permanent magnet can be positioned in the central recess of the internal flux barrier. Preferably, a single permanent magnet can be positioned in the central recess. This limits the number of permanent magnets per recess, simplifying the manufacturing of the electrical machine and eliminating the manufacturing constraints associated with permanent magnets.

[0090] Alternatively or cumulatively, for each magnetic pole, a permanent magnet can be positioned in each lateral recess of the internal flux barrier. Preferably, a single permanent magnet can be positioned in each lateral recess of the internal flux barrier. This limits the number of permanent magnets per recess, simplifying the manufacturing of the electrical machine and eliminating the manufacturing constraints associated with permanent magnets.

[0091] Alternatively, or in addition to one of the two preceding embodiments, for each magnetic pole, a permanent magnet can be positioned in each lateral recess of the external flux barrier. Preferably, a single permanent magnet can be positioned in each lateral recess of the external flux barrier. This limits the number of permanent magnets per recess, simplifying the manufacturing of the electrical machine and eliminating the manufacturing constraints associated with permanent magnets.

[0092] According to a preferred implementation, each magnetic pole can comprise five permanent magnets positioned in the five recesses: in the three recesses of the internal flux barrier, and in the two recesses of the external flux barrier. This implementation improves torque density and power density. Having five magnets also allows for a smaller diameter rotor with a high number of pole pairs, as fewer magnets need to be arranged within each magnetic pole, while still meeting industrial constraints on permanent magnet dimensions. Alternatively, only the lateral recesses of the internal and external flux barriers can be fitted with permanent magnets.

[0093] When each magnetic pole contains multiple permanent magnets, the permanent magnets can be identical in size. This solution ensures good performance of the electrical machine while minimizing manufacturing costs. This design is particularly advantageous when each magnetic pole contains five permanent magnets.

[0094] Alternatively, the dimensions of the permanent magnets can be different.

[0095] For each magnetic pole, the lateral recesses of the internal and / or external flux barriers can be symmetrical with respect to the radius perpendicular to the central recess of the internal flux barrier. Preferably, this symmetry exists for both the internal and external flux barriers. When the external flux barrier is symmetrical, the magnetic bridge located between the inclined recesses is radial and lies on the radius perpendicular to the central recess of the internal flux barrier. This symmetry allows for optimization of the electrical machine's mechanical performance.

[0096] Advantageously, the central recess of the internal flow barrier can also be symmetrical to the radius perpendicular to it.

[0097] All the rotor's magnetic poles can be identical. Alternatively, consecutive rotor magnetic poles can be different: two consecutive rotor magnetic poles are then asymmetrical. This asymmetry can be created by different inclination angles of the inclined recesses of the internal and external flux barriers. For this implementation, if the rotor has p pairs of magnetic poles, it comprises p identical primary magnetic poles and p identical secondary magnetic poles, each different from the primary magnetic poles, with the secondary magnetic poles interposed between the primary magnetic poles. This asymmetrical design reduces torque ripple, back electromotive force harmonics, and acoustic noise.

[0098] For this embodiment, relationships between the angles of the magnetic poles can be defined. If p denotes the number of pole pairs of the rotor, the average angle of a magnetic pole (which would be the angle of the magnetic poles of a rotor without asymmetry) can be written as: The angle of the primary magnetic poles, ypl, can then be expressed by an equation of the form: ypl = kxy, where k is an asymmetry constant. According to one embodiment of the invention, k can be between 0.9 and 1 (inclusive), and preferably between 0.91 and 0.95 (inclusive). These ranges of values ​​allow for good reduction of torque ripple.

[0099] The angle of the secondary magnetic poles yp2 can then be deduced by the equation: yp2 = 2y — ypl.

[0100] The angle of inclination of inclined recesses can be defined as the angle between a straight line passing through the center C of the rotor and a midpoint located on an external face of the inclined recess of the considered flow barrier, and the radius perpendicular to the central recess of the internal flow barrier. The angle of inclination of the inclined recesses of the internal flow barrier is referred to as the internal angle of inclination, and the angle of inclination of the inclined recesses of the external flow barrier as the external angle of inclination.

[0101] According to one embodiment, the internal inclination angle of the primary magnetic pole 51 p1 can be defined by the relation:

[0102] Slpl = k lpl x ypl, with k lpl a constant, with k lpl which can be between 0.5 and 0.9 (inclusive), preferably between 0.7 and 0.9 (inclusive).

[0103] Furthermore, the external tilt angle of the primary magnetic pole 52p1 can be defined by the relation:

[0104] <52pl = k 2pl x Slpl with k 2pl a constant, with k 2pl which can be between 0.4 and 0.9 (inclusive), preferably between 0.5 and 0.65 (inclusive).

[0105] According to one embodiment, the internal inclination angle of the secondary magnetic pole 51 p2 can be defined by the relation:

[0106] <51p2 = k lp2 x yp2 with k lp2 a constant, with k lp2 which can be between 0.5 and 0.9 (inclusive), preferably between 0.7 and 0.9 (inclusive). Furthermore, the external inclination angle of the primary magnetic pole 52p2 can be defined by the relation:

[0107] S2p2 = k 2p 2 x <51p2 with k 2p2 a constant, with k 2p2which can be between 0.4 and 0.9 (inclusive), preferably between 0.5 and 0.7 (inclusive).

[0108] These angular ranges allow for optimization of the magnet arrangement, generating reduced torque ripples while maximizing the torque and power of the high-speed machine.

[0109] The opening angle of the inclined recesses of the internal or external flow barrier is defined as the angle formed between two straight lines, each line passing through the midpoint of two sides of an inclined recess (without considering any additional shapes at the ends of the recess). The two sides of the inclined recess are the one facing the periphery of the rotor and the one facing the center of the rotor. These two sides correspond to the shorter sides of the recesses. For the embodiment in which the recesses have a substantially rectangular shape (excluding any additional shapes) in the transverse plane of the rotor, the two sides correspond to the thickness of the recesses. In other words, the opening angle of the external flow barrier corresponds to the angle formed by the segments of the V, and the opening angle of the internal flow barrier corresponds to the angle formed by the opposite segments of the U.

[0110] According to one embodiment, the opening angle of the inclined recesses of the internal flow barrier can be strictly less than the opening angle of the inclined recesses of the external flow barrier.

[0111] According to one embodiment, the opening angle of the inclined recesses of the internal flux barrier can be acute, i.e. less than 90°. Such an angle makes it possible to increase the size of the lateral recesses, and where applicable the size of any lateral permanent magnets, which makes it possible to maximize the torque of the electric machine.

[0112] In one embodiment, the opening angle of the inclined recesses in the external flux barrier can be obtuse or right, i.e., greater than or equal to 90°. Such an angle allows for an increase in the size of the lateral recesses, and where applicable, the size of any lateral permanent magnets, thereby maximizing the torque of the electric machine. An internal radius can be defined to designate the radius of the internal flux barrier, the internal radius being the distance between the center of the rotor and the side of the central recess of the internal flux barrier facing the center of the rotor, this internal radius being defined as the radius perpendicular to the central recess of the internal flux barrier.

[0113] The ratio between the internal radius and the rotor radius can be between 0.3 and 0.8 (inclusive terminals) and preferably between 0.55 and 0.7 (inclusive terminals) to optimize the torque and power of the electric machine.

[0114] An external radius can be defined to designate the radius of the external flux barrier, the external radius being the distance between the center of the rotor and a projection of the point closest to the center of the rotor of an inclined recess of the external flux barrier onto the radius perpendicular to the central recess of the internal flux barrier.

[0115] According to one embodiment, a relationship can be defined between the internal radius r in t, the rotor radius r and the external radius r ex t:

[0116] With kr being a coefficient, kr can be between 0.2 and 0.8 (inclusive), preferably between 0.35 and 0.55 (inclusive) to optimize the magnetic performance of the electric machine.

[0117] The magnetic poles may include weight-relieving recesses arranged between the external flux barrier and the rotor periphery. In other words, each magnetic pole may include a weight-relieving recess between the external flux barrier and the rotor periphery. These weight-relieving recesses are not intended to house permanent magnets. They serve to reduce the rotor mass and minimize mechanical stresses on the rotor body at high speeds, thereby maximizing the rotor's performance density. These weight-relieving areas do not create local saturation between themselves and the V-shaped flux barrier, unlike the additional recesses according to the invention, which create new air gaps.

[0118] Advantageously, the relief recess can have a substantially triangular shape. Preferably, two sides of the triangular shape can be parallel to the inclined recesses of the external flux barrier. Thus, the spacing between the relief recess and the inclined recesses is almost constant, allowing for good mechanical stability of the rotor body without loss of electromagnetic performance. Furthermore, one vertex of the triangle can be positioned on the radius perpendicular to the central recess of the internal flux barrier, and the radius perpendicular to the central recess of the internal flux barrier can optionally be an axis of symmetry of the triangle. In addition, the third side can face the periphery of the rotor, being parallel to the tangent of the rotor periphery at the point of intersection with the radius perpendicular to the central recess of the internal flux barrier.

[0119] Alternatively, the weight-relieving recess can have other shapes, such as circular, rectangular, a portion of a disk shape for example with the face near the periphery of the rotor being an arc of a circle with a radius identical or different from the radius of the periphery of the rotor, etc.

[0120] The rotor can comprise p pairs of magnetic poles (or 2xp magnetic poles). Advantageously, p can be between 2 and 9, and preferably p is between 3 and 6, and preferably equals 4.

[0121] According to the present invention, two additional recesses are added to the rotor, arranged between the recesses of the external flux barrier and the outer edge of the rotor body, to modify the trajectory of the magnetic fluxes emitted by said permanent magnets in the rotor.

[0122] These additional recesses may each be circular, oval, ovoid, triangular, or have four or more sides, including rounded edges, such as a square, trapezoid, rhombus, or rectangle. They may be the same shape or different shapes, the same dimensions, or different dimensions. They may be arranged on either side of the radius R mentioned above, including at an angle to each other, and preferably arranged symmetrically with respect to said radius.

[0123] The recesses, which are the subject of the invention, on the whole of the rotor (described by a solid disk of external diameter which is that of the rotor) can together represent 0.25% to 5% of the surface area of ​​the rotor cross-section.

[0124] At least one of the two additional recesses may have a portion of its edge running along the outer edge of the inclined recess of the nearest external flow barrier

[0125] At least one of the two additional recesses may have a portion of its edge that runs along the outer edge of the rotor body.

[0126] The two additional recesses may be inclined relative to each other, and their opening angle (y), defined similarly to the opening angles a, B mentioned above, may be obtuse or right, and preferably be identical to or close to the opening angle B of the inclined recesses of the external flow barrier. At least one of the two additional recesses may be located at a distance from and along a portion of the outer edge of the inclined recess of the external flow barrier, in particular for at least 10%, 25%, or 50% of the length of said outer edge.

[0127] The invention also relates to an electrical machine comprising a stator and a rotor as described above. The rotor is arranged inside the stator. Conventionally, the stator includes windings to generate a rotating magnetic field capable of rotating the rotor relative to the stator. The windings can be inserted into axial slots in the stator, the slots being arranged circumferentially within the stator.

[0128] According to one embodiment, the electrical machine is a synchronous reluctance machine assisted by permanent magnets.

[0129] Figures 1a and 1b, described together, schematically and without limitation illustrate an electric machine rotor according to a first comparative example (comparative example 1) corresponding to a rotor embodiment according to the aforementioned patent application WO2022 / 128541 (comparative example 1). It is a view of a cross-section perpendicular to the rotor axis: Figure 1 represents one-quarter of the rotor corresponding to two magnetic poles of a rotor with four pairs of magnetic poles; the other pairs of magnetic poles are deduced by circular repetition of the partial view. In this Figure 1, no permanent magnets are shown; the different embodiments of the permanent magnet arrangement are illustrated and detailed in Figures 3 to 8. The rotor 1 is formed from a stack of laminations connected to a rotor shaft 4. The illustrated portion of the rotor 1 includes two magnetic poles 16 and 16'.Each magnetic pole 16, 16' comprises two flux barriers: an internal flux barrier 2 and an external flux barrier 3. The internal flux barrier 2 comprises a central recess 5 and two inclined recesses 6 on either side of the central recess 5; these three recesses 5, 6 form a flux barrier having a substantially U-shape. A radial magnetic bridge 17 is provided between the central recess 5 and each inclined recess 6. A tangential bridge 18 is provided between each inclined recess 6 and the periphery of the rotor 1. The external flux barrier 3 comprises two inclined recesses 7; these two recesses 7 form a flux barrier having a substantially V-shape. A radial magnetic bridge 19 is provided between the inclined recesses 7. A tangential bridge 20 is provided between each inclined recess 7 and the periphery of the rotor 1.

[0130] In addition, the rotor includes an optional weight-relieving recess 8, substantially triangular in shape, located between the external flow barrier 3 and the periphery of the rotor 1. The weight-relieving recess 8 has two sides parallel to the lateral recesses 7 of the external flow barrier 3, and the third side faces the periphery of the rotor 1. The rotor may include other weight-relieving recesses, such as the weight-relieving recesses 15 provided between the rotor shaft 4 and the internal flow barrier 2.

[0131] For the embodiment shown in Figure 1a, each recess 5, 6, or 7 of the internal and external flow barriers is substantially rectangular in shape and includes two additional shapes at its ends. These are the additional shapes 10 for the central recess 5, the additional shapes 9 for the inclined recesses 6, and the additional shapes 11 for the inclined recesses 7. These additional shapes 9, 10, and 11 are L-shaped, rounded rectangular, and segment-shaped.

[0132] Figure 1b shows the radius R, which is perpendicular to the central recess 5. The radius R is an axis of symmetry of the central recess 5. Furthermore, in this figure, the lines D6 and D7 are drawn. The lines D6 pass through the midpoints of two opposite sides of the inclined recesses 6 (not counting the additional shapes 9). The lines D7 pass through the midpoints of two opposite sides of the inclined recesses 7 (not counting the additional shapes 11). The opening angle of the inclined recesses 6 of the internal flow barrier is denoted α; it is defined by the angle formed by the two lines D6, this angle α is an acute angle. The opening angle of the inclined recesses 7 of the external flow barrier is denoted β; it is defined by the angle formed by the two lines D7, this angle β is an obtuse angle. Furthermore, we have the following relationship: α <p.

[0133] In the illustrated embodiment, the magnetic pole is symmetrical with respect to the radius R. In this case, angle α is formed by a first angle of inclination α1 and a second angle of inclination α2. Each of angles α1 and α2 is defined between a line D6 and the radius R, with α1 = α2 (which implies that the inclined recesses α6 are symmetrical). Furthermore, angle β is formed by a first angle of inclination β1 and a second angle of inclination β2. Each of angles β1 and β2 is defined between a line D7 and the radius R, with β1 = β2 (which implies that the inclined recesses β7 are symmetrical).

[0134] Furthermore, the two magnetic poles 16 and 16' are different: the angles of the inclined recesses of the flux barriers of magnetic pole 16 are greater than the angles of the inclined recesses of the flux barriers of magnetic pole 16'. In addition, the supplementary shapes 10, 11 are different between magnetic poles 16 and 16'.

[0135] Furthermore, here, the radius R is an axis of symmetry of the relief recess 8.

[0136] Alternatively, all the magnetic poles of rotor 1 can be identical. Figure 2 shows a first example of an embodiment according to the invention (example 1) of a portion of the rotor, here a quarter of the rotor, analogous to the representation in Figure 1a. The characteristics already described in Figure 1, concerning the design of the internal flux barrier 2 and the external flux barrier 3, will not be described again. Only the additional characteristics, different from or modified from those of the rotor in Figure 1, will be described:

[0137] Here, there is no weight-relieving recess 8 (although this recess can be provided optionally, as described later with reference to Figure 14). Two additional recesses 20 are provided in the area of ​​the rotor 1 delimited on one side by the external flow barrier 3 defined by the two recesses 7 and on the other side by the outer edge 21 of the rotor body 1. They are triangular in shape with rounded edges and are identical in size and shape. They are arranged on either side of the radius R, preferably symmetrically with respect to this radius, like the recesses 7. One of their edges runs along the outer edge 21 of the rotor, and another of their edges runs along the outer edge 71 of the nearest recess 7. The triangular shape shown here is essentially isosceles, but could also be equilateral, rectangular, or otherwise.

[0138] The surface area of ​​these additional recesses throughout the rotor represents 0.25% to 5% of the total rotor cross-section.

[0139] The surface area of ​​these additional recesses can also represent, for comparison, 5% to 50% of the surface area of ​​the recesses 7 of the external flow barrier.

[0140] The presence of these additional recesses 20 will modify the magnetic flux generated by the magnets of the magnetic pole in question, which can be visualized using Figure 15: on the left, flux lines are shown for a portion of the rotor according to the comparative example (Figure 1), and on the right, the flux lines are shown when the two additional recesses are provided according to Example 1 of the invention (Figure 2). The presence of the air gaps creates at least two local saturations (darker areas in the figure), one near the magnet and the other near the outer radius of the rotor. These saturations create toothing in the rotor, which helps to reduce the harmonics of magnetic flux and voltage.

[0141] Figure 3 shows a second embodiment of the invention (example 2): All other things being equal with the first example shown in Figure 2, the additional recesses 20' here have a more trapezoidal shape, with rounded edges. Their longer sides (corresponding to the larger base of the trapezoid) 201 run along the outer edge 71 of the recesses 7, and one of their shorter sides (corresponding to the smaller base of the trapezoid) runs along the outer edge 21 of the rotor. Their surfaces are larger than the surfaces of the additional recesses 20 shown in Figure 1, and they are inclined relative to each other, along the length of their longer edges 201 (corresponding to the larger base of the trapezoid), at an opening angle θ that may be similar or identical to the opening angle B between the recesses 7.

[0142] Figure 14 shows a rotor plate according to a third embodiment (Example 3) of the invention: all other things being equal, it adds to the rotor of Example 2 (according to Figure 3) a weight-reducing recess 8', 8" arranged between each pair of additional recesses 20. These weight-reducing recesses may or may not be identical to each other. In this Example 3, they are arranged in the same way with respect to the recesses 20; they are both circular, but one (8') has a larger diameter than the other (8"). Alternatively, the weight-reducing recesses may be identical and / or arranged differently with respect to the other recesses and / or non-circular in shape (oval, for example). As their name indicates, their function is solely to lighten the rotor, unlike the recesses 20.

[0143] Comparative example 2 is shown in Figure 16: all other things being equal, it represents a portion of rotor similar to that of the comparative example according to Figure 1a, with the difference that here there is no weight-reduction recess 8.

[0144] Figures 4 to 7 represent, through different graphs, the no-load performance of the electric machine equipped with the rotor according to comparative example 2 of figure 16 (curves C1) and according to example 1 according to the invention (curves C2):

[0145] The graph in Figure 4 represents the phase-to-phase induced voltage curve C1 of the electric machine integrating the rotor according to comparative example 2 (Figure 16) and the curve C2 of the one integrating the rotor according to the first example (Figure 2): we see that by the appropriate placement of the two additional recesses, we manage to modulate the waveform of the induced voltage, with a C1 curve smoother than the C2 curve and with a lowered maximum peak.

[0146] The graph in Figure 5 represents the Fourier series decomposition of the induced voltage between phases. For each harmonic, the right-hand bar of the bar graph corresponds to comparative example 2 (Figure 16) and the left-hand bar to that of the first example (Figure 2): we see the very significant contribution of the additional cutouts 20 on the 5th, 11th and 13th harmonics, which leads to easier control of the electrical machine.

[0147] The graph in Figure 6 represents the maximum induced phase-to-phase voltage as a function of motor speed (rotor speed), using the same conventions as in Graph 4: curve C1 corresponds to comparative example 2 (Figure 16) and curve C2 to the first example (example 1, Figure 2) according to the invention. It can be seen that curve C2 is below curve C1, and this difference is more pronounced as the rotor speed increases.

[0148] The graph in Figure 7 represents the fundamental of the induced voltage as a function of the engine speed, with the same conventions as for graphs 4 and 6: curve C1 corresponds to comparative example 2 (Figure 16) and curve C2 to the first example according to the invention (example 1, Figure 2). The curves are almost superimposed.

[0149] What we can deduce from the graphs in Figure 6 and Figure 7 is that with the invention:

[0150] - we manage to significantly reduce the peak induced no-load voltage, here by about 10% (figure 6), which is favorable to a rapid increase in the speed of the electric machine-

[0151] - while the corresponding voltage drop (figure 7) is very small, here less than 1%, which is favorable to obtaining a high torque.

[0152] The solution according to the invention, compared with the prior art, therefore makes it possible to lower the no-load voltage peak while maintaining a high effective voltage value, which guarantees better performance in both torque / power and maximum speed ramp-up of the electric machine.

[0153] Figures 8 to 11 represent, through different graphs, the load performance of the electric machine equipped with the rotor according to comparative example 2 (figure 16) (curves C1) and according to the first example (example 1, figure 2) according to the invention (curves C2):

[0154] Figure 8 shows that the mechanical torque envelope as a function of rotor rotation speed is close for both examples.

[0155] Figure 9 shows that the mechanical power envelope as a function of rotational speed is also close for both examples, with the advantage, for the first example according to the invention (curve C2) of being able to ensure operation at very high rotational speeds, beyond 12000 rpm and even in the vicinity of 15000 rpm, rotational speed values ​​inaccessible with the comparative example (curve C1).

[0156] Figure 10 includes:

[0157] - a graph on the right representing the electromagnetic torque ripple (“EM Torque ripple”) as a function of the peak current (“Ipeak”), in amperes (A) for the machine equipped with the rotor according to comparative example 2 (figure 16) and the rotor according to the invention (example 1, figure 2): we see that the curve C2, for a current of 100A, starts above the curve C1, then it crosses the curve C1 for an intensity of about 150 A and beyond this value, it drops much more than the curve C1, with a break in the curve around 230 A. We see that around 350 to 450 A, the curve C1 reaches high values, around 17%, while the curve C2 is only at 10%: we thus see that with the invention, we very significantly reduce the “ripple” over a very wide range of current.

[0158] - a graph on the left, representing the average electromagnetic torque (“EM Mean Torque” in English) expressed in Nm, as a function of the peak current (“Ipeak”), in amperes (A) for the machine equipped with the rotor according to comparative example 2 (figure 16) and the rotor according to the invention (example 1, figure 2): we see that the two curves C1 and C2 are almost superimposed, the curve C2 standing out from the curve C1 and being slightly below it when the current reaches 250 A.

[0159] What can be deduced from these two graphs is that the example according to the invention slightly reduces the average torque at maximum current by 2-3%, this loss being largely acceptable in view of the gain observed on the torque ripples of the order of 40%.

[0160] Figure 11 shows a graph comparing the efficiency of two electrical machines as a function of machine speed (rpm) and mechanical torque (in Nm) for the machine equipped with the rotor according to comparative example 2 (Figure 16) (C1, solid curve) and the rotor according to example 1 (Figure 2) of the invention (C2, dashed curve). The circled areas Z are impacted areas.

[0161] It follows that the example according to the invention makes it possible to improve the efficiency of the machine from 9000 rpm, with gains of up to 3, or even 5 points of efficiency.

[0162] However, a decrease in efficiency of approximately 1 percentage point is observed at low speeds and high loads. This decrease in efficiency in this range is largely offset by the gain observed at high speeds.

[0163] From this series of figures, we see that the maximum power of the electric machine equipped with the rotor according to the invention remains unchanged, but that we have been able to gain about 10% on the maximum speed of the electric machine, which is very significant.

[0164] Figures 12 and 13 concern the torque / power envelope graphs referred to the wheels of a vehicle equipped with an electric motor machine described above, with the rotor according to comparative example 2 - figure 16 (curve C1) and according to example 1 - figure 2 according to the invention (curve C2): figure 12 relates to the torque envelope and figure 13 to the power envelope, as a function of the wheel speed in revolutions per minute.

[0165] From these two figures, we can see that with the invention we have gained about 10% on the maximum speed of the electric machine, and that we have been able to increase the torque on the road by about 10% at the same maximum speed of the vehicle.

Claims

Demands 1. Rotor for an electric machine, said rotor comprising a rotor body (1) formed by a stack of laminations, and a plurality of pairs of magnetic poles (16, 16'), each magnetic pole (16, 16') being composed of at least two flux barriers, of which - an internal flow barrier (2) comprising two recesses inclined (6) to each other and arranged on either side of a central recess (5), said central recess (5) being perpendicular to a radius (R) of the rotor, - an external flow barrier (3) comprising two recesses inclined (7) to each other and arranged, on either side of said radius (R), between the central recess (5) of the internal flow barrier (2) and the outer edge (21) of the rotor body (1), - and at least one permanent magnet (12) positioned in at least one recess (5,6,7) of each of said two flux barriers (2, 3), characterized in that at least one of the magnetic poles, in particular each magnetic pole, comprises two additional recesses (20) disposed between the recesses (7) of the external flux barrier (3) and the outer edge (21) of the body (1) of the rotor to modify the trajectory of the magnetic fluxes emitted by said permanent magnets (12) in the rotor.

2. Rotor for electric machine according to claim 1, characterized in that each magnetic pole (16, 16') is composed of only two flux barriers.

3. Rotor for electric machine according to claim 1 or 2, characterized in that the additional recesses (20) each have a circular or oval or ovoid, or oblong, or triangular or polygonal shape, in particular with four or more sides, in particular with rounded edges, in particular a square, a trapezoid, a rhombus, a rectangle.

4. Rotor for electric machine according to any one of the preceding claims, characterized in that the two additional recesses (20) of a magnetic pole have the same shape or a different shape, the same dimensions, or different dimensions.

5. Rotor for electric machine according to any one of the preceding claims, characterized in that the two additional recesses (20) of a magnetic pole are arranged on either side of said radius (R), in particular inclined to each other, and preferably arranged symmetrically with respect to said radius (R).

6. Rotor for electric machine according to any one of the preceding claims, characterized in that the additional recesses (20) over the whole rotor together represent 0.25% to 5% of the surface area of ​​the rotor cross-section.

7. Rotor for electric machine according to any one of the preceding claims, characterized in that at least one of the two additional recesses (20) has a part of its edge which runs along the outer edge (71) of the inclined recess (7) of the nearest external flux barrier (3).

8. Rotor for electric machine according to the preceding claim, characterized in that the part of the edge of the additional recess(s) (20) which runs along the outer edge (71) of the inclined recess (7) of the nearest external flux barrier (3) is distant from said outer edge (71) by a distance of between 0.35 mm and 2 mm.

9. Rotor for electric machine according to any one of the preceding claims, characterized in that at least one of the two additional recesses (20) has at least a part of its edge which runs along the outer edge (21) of the rotor body.

10. Rotor for electric machine according to the preceding claim, characterized in that the part of the edge of the additional recess(s) (20) which runs along the outer edge (21) of the rotor is distant from said outer edge (21) by a distance of between 0.35 mm and 1 mm.

11. Rotor for electric machine according to claims 7 and 9, characterized in that the distance between the part of the edge of the additional recess(20) which runs along the outer edge (71) of the inclined recess (7) of the nearest external flux barrier (3) and said outer edge (71) is between one and two times the distance between the part of the edge of the additional recess(20) which runs along the outer edge (21) of the rotor body and said outer edge (21).

12. Rotor for electric machine according to any one of the preceding claims, characterized in that the two additional recesses of a magnetic pole (20) are inclined relative to each other, and in that their opening angle (y) is obtuse or right, and preferably identical or close to the opening angle (B) of the inclined recesses (7) of the external flux barrier (3).

13. Rotor for an electric machine according to any one of the preceding claims, characterized in that at least one of the two additional recesses (20) of a magnetic pole is disposed at a distance from and along a portion of the outer edge (71) of the inclined recess (7) of the external flow barrier (3), in particular over at least 10% to 50% of the length of said outer edge.

14. Rotor according to any one of the preceding claims, characterized in that at least one of the magnetic poles, in particular each magnetic pole also comprises a lightening recess (8) between the recesses (7) of the external flux barrier (3) and the outer edge (21) of the rotor body (1), said lightening recess (8) preferably having a substantially triangular shape, the two additional recesses (20) being arranged on either side of said lightening recess (8).

15. Electrical machine characterized in that it comprises a stator and a rotor (1) according to any one of the preceding claims, said rotor being housed inside said stator.

16. Electric machine according to the preceding claim, characterized in that said stator comprises a plurality of radial slots arranged circumferentially along said stator.

17. Electric machine according to any one of claims 15 or 16, characterized in that said electric machine is a synchronous-reluctant electric machine assisted by permanent magnets.

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