Rotor for electric machine comprising at least two flux barriers having concave centerline

Abstract

The invention relates to a rotor (2) for an electric machine, comprising:-a rotor body; and-the centerlines (L1) of the magnetic poles, the first and second flux barriers being uninterrupted concave lines, each centerline (L1) intersecting the outer diameter (4) of the rotor body at two end points (10, 11), and the point of intersection of each centerline (L1) with its axis of symmetry (AA) being an inner point (12) on an inner radius from the center of the rotor body, wherein an inner radius Ri1 of an inner point (12) of a center line (L1) of the first barrier satisfies Rint + (Rext-Rint) (0.105 p + 0.147-0.05) < = Ri1 < = Rint + (Rext-Rint) (0.105 p + 0.147 + 0.05), an inner radius Ri2 of an inner point of a center line of the second barrier satisfies Rint + (Rext-Rint) (0.066 p + 0.519-0.05) < = Ri2 < = Rint + (Rext-Rint) (0.066 p + 0.519 + 0.05), p is the number of pole pairs, and Rext and Rint are the outer radius and the inner radius of the rotor body.

Description

Technical Field

[0001] The present invention relates to a (permanent magnet assisted) synchronous reluctance rotating electric machine, and more particularly to a specific structure of the rotor in such a machine.

[0002] Generally, such an electric machine includes a rotor and a stator, which are coaxially arranged one inside the other.

[0003] The rotor is formed by a rotor body having a stack of laminations placed on a rotor shaft. These laminations include housings for permanent magnets and perforations for creating flux barriers so that the flux from the magnets can be radially directed to the stator and promote the generation of reluctance torque, and so that the rotor can be lightened to reduce the centrifugal forces that the stack of laminations has to withstand.

[0004] The rotor is typically housed inside a stator carrying electric windings for generating a magnetic field to rotate the rotor. Background Art

[0005] In particular, as better described in patent application WO2020 / 020580, the rotor of such a synchronous reluctance electric machine includes a plurality of axial grooves that pass through the laminations from one side to the other.

[0006] In the rotor design described in this patent application, a first series of axial grooves are arranged one above the other radially and at a certain distance from each other, forming housings for flux generators, in this case permanent magnets in the form of rectangular columns.

[0007] Another series of grooves consists of perforations in an inclined radial direction that start from these housings and reach near the edge of the laminations, i.e., near the air gap.

[0008] The inclined perforations are symmetrically arranged with respect to the housings for the magnets, thus forming in each instance a geometric figure that is substantially V-shaped with a flat bottom, where the flat bottom of the V is formed by the housings for the magnets and the inclined arms of the V are formed by the perforations. This forms a flux barrier formed by the perforations. The flux emitted by the permanent magnets can then only pass through the solid portions between the perforations. These solid portions are made of ferromagnetic material.

[0009] Patent application JP2003 / 348779 is known, which relates to an electric machine rotor having permanent magnets mounted in grooves. However, this rotor does not provide the precise shapes of the flux barriers and grooves for enhancing the performance of the electric machine.

[0010] Patent application US2015 / 137646 relating to an electric machine rotor is also known. However, this rotor does not provide the precise shapes of the flux barriers and grooves for enhancing the performance of the electric machine.

[0011] The technical problem to be solved here is to improve the motor performance by increasing the proportion of the synchronous reluctance in the torque (so the goal is to maximize the reluctance torque) as much as possible, while minimizing the number of permanent magnets required. Summary of the Invention

[0012] The present invention relates to a rotor for an electric motor, the rotor comprising:

[0013] - a rotor body formed by a stack of laminations, preferably configured to be positioned on a rotor shaft, the rotor body being defined by a cylindrical inner surface having an inner diameter and a cylindrical outer surface having an outer diameter, and

[0014] - a plurality of pairs of magnetic poles circumferentially distributed on the rotor body, consecutive magnetic poles being separated by a radial separation plane, each magnetic pole comprising at least two flux barriers radially one above the other, each flux barrier comprising at least one groove, and each magnetic pole comprising at least one permanent magnet in the groove.

[0015] Furthermore, the centerlines of the first and second flux barriers of each magnetic pole counted from the center of the rotor outwards are uninterrupted concave lines. In a cross-section, each centerline intersects the cylindrical outer surface of the rotor body at two end points and has a radial axis of symmetry. The intersection point of each centerline with its radial axis of symmetry is an internal point located at the inner radius of the center of the rotor body. The inner radius Ri1 of the internal point of the centerline of the first barrier satisfies R int +(R ext -R int )·(0.105·p + 0.147 - 0.05) ≤ Ri1 ≤ R int +(R ext -R int )·(0.105·p + 0.147 + 0.05), and the inner radius Ri2 of the internal point of the centerline of the second barrier satisfies R int +(R ext -R int )·(0.066·p + 0.519 - 0.05) ≤ Ri2 ≤ R int +(R ext -R int )·(0.066·p + 0.519 + 0.05), where p is the number of pole pairs, R ext is half of the outer diameter of the rotor body, and R int is half of the inner diameter of the rotor body.

[0016] Preferably, the radial straight lines passing through the respective end points of the center line of the first flux barrier form an angle between 21° / (2*p) and 31° / (2*p) with the nearest radial separation plane, while the radial straight lines passing through the respective end points of the center line of the second flux barrier form an angle between 57° / (2*p) and 67° / (2*p) with the nearest radial separation plane.

[0017] Advantageously, each flux barrier includes zero, one, two, or three permanent magnets.

[0018] Advantageously, the permanent magnets have a curved shape or a rectangular shape adapted to the shape of the flux barrier.

[0019] According to one configuration of the present invention, each pole of the rotor body includes three or four flux barriers.

[0020] Preferably, the first and second flux barriers counted from the center to the outside each have three grooves, one of the three grooves being a central groove and the other two being lateral grooves, the third flux barrier has two grooves, and the fourth flux barrier (if any) has two grooves.

[0021] Advantageously, the first flux barrier includes three permanent magnets, one in each groove; the second flux barrier includes two permanent magnets, one in each lateral groove; and the third flux barrier and the fourth flux barrier (if any) do not include permanent magnets.

[0022] According to an alternative form of the present invention, the number of pole pairs is from 2 to 9 pairs, preferably from 3 to 6 pairs, and more preferably 4 pairs.

[0023] Advantageously, the width of the flux barrier can be constant or can decrease from an internal point towards the radial ends.

[0024] The present invention also relates to an electric machine comprising a stator and a rotor as described above, the rotor being accommodated within the stator.

[0025] Preferably, the electric machine is a synchronous reluctance machine. Description of the Drawings

[0026] Other features and advantages of the rotor and the electric machine according to the present invention will become apparent by reading the following description of embodiments given by way of non - limiting example with reference to the drawings.

[0027] Figure 1 A cross - sectional view of the stator and rotor of an electric machine according to an embodiment of the present invention is shown.

[0028] Figure 2 Details of a cross - sectional view of the rotor of an electric machine according to an embodiment of the present invention are shown. Detailed Description

[0029] The present invention relates to a rotor of an electric machine, in particular a rotor of a permanent magnet assisted synchronous reluctance machine. Furthermore, the present invention relates to an electric machine comprising a rotor and a stator according to the present invention, the rotor being coaxially arranged inside the stator relative to the stator.

[0030] According to the present invention, the rotor of the electric machine comprises:

[0031] - A rotor body, formed by a stack of laminations, preferably configured to be positioned on a rotor shaft, the rotor body being defined by a cylindrical inner surface having an inner diameter and a cylindrical outer surface having an outer diameter. Thus, the inner surface and the outer surface are cylindrical, and in a cross-sectional view in a plane perpendicular to the axis of rotation, the inner surface and the outer surface are respectively represented as circles. Thus, the rotor body forms an annular space between the inner surface and the outer surface, which space is particularly defined by the inner diameter and the outer diameter respectively; and,

[0032] - A plurality of pairs of magnetic poles, which are circumferentially distributed along the rotor body.

[0033] (Circumferentially) consecutive magnetic poles are separated from each other by a radially separating plane. Thus, they are completely separated from each other. Thus, the radially separating plane divides the rotor body into a plurality of angular regions, and all the angular regions together form the rotor body. Each angular region of the rotor forms a single magnetic pole.

[0034] Furthermore, each magnetic pole comprises at least two flux barriers radially one above the other, each flux barrier comprising at least one groove (each flux barrier preferably comprises a plurality of grooves). The grooves of the flux barriers are axial. In other words, the grooves extend axially (longitudinally), i.e., along the rotor axis extending through the entire axial length of the rotor.

[0035] Furthermore, each magnetic pole comprises at least one permanent magnet in the groove.

[0036] The permanent magnet is capable of generating a magnetic flux, allowing the rotor to rotate by creating a rotating magnetic field, which rotating magnetic field can also be generated by the stator. The flux barriers are capable of guiding the magnetic field generated by the rotor and at least one permanent magnet towards the air gap (the air gap is the space formed between the rotor periphery and the stator) to limit magnetic flux leakage and improve the performance of the electric machine (in particular torque and power). A pair of magnetic poles comprises two magnetic poles with opposite polarities.

[0037] The outer diameter of the rotor body corresponds to twice the outer radius of the rotor body; the inner diameter of the rotor body corresponds to twice the inner radius of the rotor body.

[0038] According to the present invention, the centerlines of the first and second flux barriers of each pole counted from the rotor center towards the outside are uninterrupted concave lines. The term "centerline" refers to the line that is equidistant from the edges of the flux barrier (facing the rotor center and the periphery respectively), and this centerline is defined in the rotor cross-section (i.e., the cross-section on a plane perpendicular to the rotor axis). Thus, the first flux barrier counted from the rotor center (from the axis) towards the outside corresponds to the internal flux barrier, i.e., the flux barrier closest to the rotor axis. The second flux barrier counted from the rotor center (from the axis) towards the outside thus corresponds to the next flux barrier closest to the rotor axis after the first flux barrier.

[0039] Due to the concave and uninterrupted shape of the centerlines of the first and second flux barriers, the performance of the motor is improved.

[0040] An "uninterrupted" line means that the line is fully differentiable and there is no situation where the derivative on one side of a point is not equal to the derivative on the other side of that point. When the flux barrier is formed by a plurality of grooves particularly separated by at least one magnetic bridge, the centerline also passes through the magnetic bridge. In other words, the magnetic bridge does not form a discontinuity in the centerline.

[0041] Advantageously, all the flux barriers of the rotor can have concave and uninterrupted centerlines.

[0042] In the cross-section, each centerline intersects the cylindrical outer surface of the rotor body (which intersects the rotor body at its outer diameter) at two end points. In other words, in each transverse cross-section plane (or view), the first centerline intersects the circle representing the outer surface of the rotor body (cylindrical outer surface) at the two first end points.

[0043] "Transverse cross-section" means a cross-section on a plane perpendicular to the axis of rotation.

[0044] Furthermore, each centerline has a radial axis of symmetry, and the intersection point of each centerline with its axis of symmetry is an internal point, and the distance of this point from the center of the rotor body (from the axis) corresponds to the inner radius. At the internal point of the centerline, the tangent of the centerline is perpendicular to the radial axis of symmetry. Thus, there is no discontinuity at the internal point of the centerline, so the derivative on one side of the centerline is equal to the derivative on the other side of the centerline.

[0045] The symmetry allows for the optimization of the mechanical performance of the motor.

[0046] According to the present invention, the inner radius Ri1 of the internal point of the first barrier centerline satisfies R int +(R ext -R int )·(0.105·p + 0.147 - 0.05) ≤ Ri1 ≤ R int +(R ext -R int)·(0.105·p + 0.147 + 0.05) (in millimeters for example), and the inner radius Ri2 of the inner points within the centerline of the second barrier satisfies the following condition: R int +(R ext -R int )·(0.066·p + 0.519 - 0.05) ≤ Ri2 ≤ R int +(R ext -R int )·(0.066·p + 0.519 + 0.05) (in millimeters for example), where p is the number of pole pairs, and R ext is the outer radius of the rotor body (corresponding to half of the outer diameter of the rotor body), and R int is the inner radius of the rotor body (corresponding to half of the inner diameter of the rotor body). In fact, by using this specific inner point, the shape of the flux barrier can improve the torque and power density of the motor.

[0047] Preferably, the radial lines passing through the respective end points of the centerline of the first flux barrier and the nearest radial separation plane can form an angle between 21° / (2*p) and 31° / (2*p), where p is the number of pole pairs; and the radial lines passing through the respective end points of the centerline of the second flux barrier and the nearest radial separation plane can form an angle between 57° / (2*p) and 67° / (2*p). In fact, the specific positions of these end points can enhance the effect of the flux barrier and increase the reluctance torque.

[0048] Advantageously, each flux barrier can include zero, one, two, or three permanent magnets. For example, one flux barrier can include three permanent magnets, while another flux barrier can include a single magnet. Thus, the rotor can be adapted to different expected operating or application conditions.

[0049] According to one configuration of the present invention, the permanent magnet can have a curved shape adapted to the shape of the flux barrier groove. Since this shape is adapted to the groove of the flux barrier, the number of permanent magnets in the curved groove can be optimized, thereby increasing the performance of the motor. In addition, the use of a curved magnet adapted to the groove shape can increase the reluctance torque, while the use of a prismatic magnet or a rectangular bar-shaped magnet according to the prior art will result in a reduction in the reluctance torque due to the inappropriate shape. The curved magnet can be obtained particularly by machining or any similar method.

[0050] Advantageously, each pole of the rotor body can include three or four flux barriers. In fact, the more flux barriers each pole includes, the better the magnetic field is guided. The number of three or four barriers provides an excellent compromise between the expected performance and the manufacturing complexity.

[0051] According to a preferred configuration of the present invention, the first and second flux barriers counted from the center towards the outside can each have (include) three grooves (preferably only three grooves). One of the three grooves of the first and second flux barriers is a central groove: it is positioned on the radial symmetry axis and is symmetric about the radial symmetry axis. The other two grooves of the first and second flux barriers are side (peripheral) grooves, with one lateral groove on each side of the central groove. The lateral grooves can be symmetric with respect to each other about the radial symmetry axis.

[0052] Therefore, these two lateral grooves are positioned on both sides of the central groove and are spaced apart.

[0053] The grooves of each inner flux barrier form a generally U shape (in a cross-section perpendicular to the rotor axis, which corresponds to the plane of the laminations constituting the rotor body), the bottom of the U shape is formed by the central groove, and the opposite sections of the U shape are formed by the lateral grooves.

[0054] The laminations of the rotor body can be made of ferromagnetic material to guide the magnetic flux generated by the permanent magnets and possibly existing stator windings. The grooves of the flux barriers can be obtained by perforations in the stack of laminations constituting the rotor body, and the magnetic bridges are formed by the laminations themselves.

[0055] For this configuration, the third flux barrier can preferably include (or consist of) two grooves (which are two lateral grooves symmetric with respect to each other about the radial symmetry axis), and the fourth flux barrier (if present) can also include (or consist of) two grooves (which are two lateral grooves symmetric with respect to each other about the radial symmetry axis).

[0056] Therefore, such a rotor can better guide the magnetic field towards the stator and increase the reluctance torque.

[0057] Advantageously, the first flux barrier can include three (and preferably only three) permanent magnets, one in each groove; and the second flux barrier can include two (and preferably only two) permanent magnets, one in each lateral groove. In addition, the third flux barrier and the fourth flux barrier (if present) do not include permanent magnets. This configuration can maximize the motor torque and power density while limiting the number of permanent magnets required. Limiting the number of permanent magnets can also reduce the industrial limitations on the size of the permanent magnets and also reduce the manufacturing cost.

[0058] Preferably, the number of pole pairs p can be 2 to 9 pairs, preferably 3 to 6 pairs, and more preferably 4 pairs. These numbers of poles give the motor good performance.

[0059] Advantageously, the width of the flux barriers (in particular the grooves in the flux barriers) can decrease from an inner point towards the radial ends. In other words, the width of each groove in each of the flux barriers decreases from an inner point towards the radial ends of the flux barrier. This configuration can maximize the motor torque and power density.

[0060] Preferably, the magnets may then have a suitable shape, with a thickness corresponding to the width of the grooves into which they are inserted and decreasing from the center of the rotor body towards the outside.

[0061] Alternatively, the width of the flux barriers can remain constant from an inner point to the radial ends to simplify the manufacture of, for example, the laminations and the permanent magnets.

[0062] Preferably, the magnets may then have a suitable shape, with a thickness corresponding to the width of the grooves into which they are inserted and remaining constant from the center of the rotor body towards the outside.

[0063] Figure 1 A partial cross-sectional view of a motor stator and rotor according to the present invention is shown in a schematic and non-limiting manner.

[0064] The motor includes a stator 1 and a rotor 2. The stator 1 and the rotor 2 are coaxial, and the rotor 2 is mounted inside the stator 1. In other words, the stator 1 surrounds the rotor 2.

[0065] The rotor 2 includes a rotor body, which is defined by a cylindrical inner surface with an inner radius of R int and a cylindrical outer surface with an outer radius of R ext .

[0066] The rotor 2 includes three pairs of magnetic poles (one third of the rotor is depicted in the figure, showing two magnetic poles, so the rotor 2 has a total of six magnetic poles).

[0067] Here, each magnetic pole of the rotor includes four flux barriers, one above the other radially outwards from the center.

[0068] The first flux barrier (i.e., the inner flux barrier closest to the rotor rotation axis) is defined by a first center line L1, while the second flux barrier is defined by a second center line L2.

[0069] The third and fourth flux barriers are defined by third and fourth center lines L3 and L4.

[0070] The first, second, third, and fourth center lines L1, L2, L3, and L4 are concave and unbroken.

[0071] The first flux barrier includes at least three grooves: a central groove 6 and two lateral grooves 5a and 5b. A permanent magnet is mounted in each of these grooves (the permanent magnets of one magnetic pole are shown in black, and the permanent magnets of the other magnetic pole are shown in dark gray).

[0072] The second flux barrier includes at least three grooves: a central groove 8 and two lateral grooves 7a and 7b. A permanent magnet is installed in each of the lateral grooves 7a and 7b (the permanent magnet of one magnetic pole is shown in black, and the permanent magnet of the other magnetic pole is shown in dark gray). The central groove 8 remains empty (without a permanent magnet).

[0073] The third and fourth flux barriers each include two lateral grooves 9 in which no permanent magnets are installed. These flux barriers do not have a central groove.

[0074] As can be seen from the figure, the shape of the permanent magnet is adapted to the shape of the groove, whereas, in the prior art, the groove is basically of rectangular cross-section to accommodate the basically rectangular shape of the permanent magnet. Figure 1 The permanent magnets in have a curved shape and are along the first and second centerlines L1 and L2 of the flux barrier on which they are installed.

[0075] Thanks to its specific shape, the number of permanent magnets is optimized and the torque and power density of the motor are increased.

[0076] Figure 2 Details of the flux barrier of the motor rotor according to the present invention are shown in a schematic and non-limiting manner.

[0077] Figure 2 A part of the rotor body of the rotor 2 for a motor is shown. The rotor body is defined by a cylindrical inner surface of an inner radius 3 that can be mounted on a rotor shaft and a cylindrical outer surface of an outer radius 4 that is substantially equal to the inner radius of the motor stator.

[0078] Figure 2 One-third of the cross-section of the rotor body is shown and includes two magnetic poles. Thus, the rotor includes three pairs of magnetic poles.

[0079] The magnetic poles are circumferentially distributed on the rotor body and are separated by radial separation planes P1 and P2: thus, the rotor body includes the same number of radial separation planes as its number of magnetic poles.

[0080] Here each magnetic pole includes four flux barriers that are radially one above the other from the center outwards.

[0081] The first flux barrier (i.e., the innermost flux barrier closest to the rotor rotation axis) is defined by the first centerline L1.

[0082] The centerlines of the different flux barriers are all concave and unbroken. In addition, they are symmetric about the radial symmetry axis AA. The radial symmetry axis AA of the flux barrier of the magnetic pole forms the bisector of the angle formed by the separation planes P1 and P2 on both sides of the magnetic pole.

[0083] The first flux barrier includes at least three grooves: a central groove 6 and two lateral grooves 5a and 5b. A permanent magnet is installed in each of these grooves (the permanent magnets of one magnetic pole are shown in black and those of the other magnetic pole are shown in dark gray).

[0084] The second flux barrier includes at least three grooves: a central groove 8 and two lateral grooves 7a and 7b. A permanent magnet is installed in each of the lateral grooves 7a and 7b (the permanent magnets of one magnetic pole are shown in black and those of the other magnetic pole are shown in dark gray). The central groove 8 remains empty (without a permanent magnet).

[0085] The third and fourth flux barriers each include two lateral grooves 9 in which no permanent magnets are installed. These flux barriers do not have a central groove.

[0086] As can be seen from the figure, the shape of the permanent magnet is adapted to the shape of the groove, whereas, conversely, in the prior art, the groove is basically of rectangular cross-section to accommodate the basically rectangular shape of the permanent magnet. Figure 2 The permanent magnets in have a curved shape and are along the first and second centerlines of the first and second flux barriers in which they are installed.

[0087] Thanks to its specific shape, the number of permanent magnets is optimized and the torque and power density of the motor are increased.

[0088] The first centerline L1 is defined by two end points 10 and 11 which are located at the intersections of the centerline with the cylindrical outer surface of the rotor body (having an outer radius 4) in a section in a plane perpendicular to the axis of rotation. In fact, in such a section, both the inner surface and the outer surface of the rotor body are represented as circles.

[0089] The radial line passing through the intersection points 10 and 11 forms an angle θ with the nearest separation plane (plane P1 in the case of end point 11 and plane P2 in the case of end point 10).

[0090] The first centerline L1 is also defined by an internal point 12 located on the radial symmetry axis AA, the distance of which from the center is equal to the first inner radius Ri1.

[0091] At the internal point 12, the centerline is perpendicular to the radial symmetry axis AA.

[0092] Similarly, the second centerline, and the third and preferably the fourth centerlines when present, are each defined by two end points which are located at the intersections of the respective centerlines with the cylindrical outer surface of the rotor body in a section in a plane perpendicular to the axis of rotation. In fact, in such a section, both the cylindrical inner surface and the outer surface of the rotor body are represented as circles. The radial line passing through the intersection point of each centerline forms an angle with the nearest separation plane.

[0093] Each centerline is also defined by an internal point located on the radial symmetry axis AA, the distance of which from the center is equal to the inner radius.

[0094] At the internal point of each centerline, the centerline is perpendicular to the radial symmetry axis AA.

[0095] It can be seen that in Figure 2 , as in Figure 1 , the width of the flux barrier groove decreases from the internal point towards the end points. The thickness of the permanent magnet is variable and decreases in the same way from the inside to the outside of the rotor to adapt to the shape of the groove. This shape can increase the motor torque.

[0096] Alternatively and without departing from the scope of the present invention, the width of the groove can be kept constant from the internal point to the end points. This configuration simplifies the manufacture of the magnet (in this case the magnet has a constant thickness to adapt to the constant width of the groove into which it is inserted).

[0097] To increase the torque and power density of the motor, the shape of the centerlines can be optimized, especially the first two centerlines counted from the center towards the outside. In particular, when the inner radius Ri1 of the internal point of the first barrier centerline satisfies R int +(R ext -R int )·(0.105·p + 0.147 - 0.05) ≤ Ri1 ≤ R int +(R ext -R int )·(0.105·p + 0.147 + 0.05) and the inner radius Ri2 of the internal point of the second barrier centerline satisfies R int +(R ext -R int )·(0.066·p + 0.519 - 0.05) ≤ Ri2 ≤ R int +(R ext -R int )·(0.066·p + 0.519 + 0.05), the motor provides better performance, where p is the number of pole pairs, R ext is the outer radius of the rotor body, and R int is the inner radius of the rotor body.

[0098] The shape of the flux barrier can be further improved by defining the positions of the end points of the first and second centerlines as follows:

[0099] - The radial line passing through each end point of the first flux barrier centerline forms an angle between 21° / (2*p) and 31° / (2*p) with the nearest radially separating plane,

[0100] - The radial straight line passing through each end point of the second magnetic flux barrier center line forms an angle between 57° / (2*p) and 67° / (2*p) with the nearest radially separated plane.

[0101] The topology of a specific rotor of the present invention, and the motor according to the present invention enable the reduction of the required number of permanent magnets, and thus the reduction of the usage of rare earths. In addition, it has the advantage of maximizing the torque generated by the magnets consumed per unit mass, especially generating reluctance torque (independent of magnets, accounting for more than 50% of the total torque) and synchronous torque (depending on magnets).

[0102] Example

[0103] An example of a rotor according to the present invention was compared with a rotor according to the prior art WO2020 / 020580 in the same motor.

[0104] The characteristics of the motor equipped with the rotor according to the present invention and the prior art rotor are as follows:

[0105] - Length: 175 mm

[0106] - Outer diameter of the rotor: 120 mm (outer radius of the rotor: 60 mm)

[0107] - Inner diameter of the rotor: 36 mm (inner radius of the rotor: 18 mm)

[0108] The rotor of the present invention corresponds to Figure 1 the rotor with three pairs of magnetic poles in

[0109] - The inner radius Ri1 of the inner point of the first barrier center line satisfies R int +(R ext -R int )·(0.105·p + 0.147 - 0.05) ≤ Ri1 ≤ R int +(R ext -R int )·(0.105·p + 0.147 + 0.05)

[0110] - The inner radius Ri2 of the inner point of the second barrier center line satisfies R int +(R ext -R int )·(0.066·p + 0.519 - 0.05) ≤ Ri2 ≤ R int +(R ext -R int )·(0.066·p + 0.519 + 0.05), where p is the number of pairs of magnetic poles, R ext is the outer radius of the rotor body, and R int is the inner radius of the rotor body.

[0111] - The radial straight lines passing through each end point of the first magnetic flux barrier center line form an angle between 21° / (2*p) and 31° / (2*p) with the nearest radial separation plane.

[0112] - The radial straight lines passing through each end point of the second magnetic flux barrier center line form an angle between 57° / (2*p) and 67° / (2*p) with the nearest radial separation plane.

[0113] Therefore, for the rotor of the present invention:

[0114] - The internal point of the first center line is located at an inner radius of 37.7 mm from the center;

[0115] - The internal point of the second center line is located at an inner radius of 47.7 mm from the center;

[0116] - The first center line is defined by two end points, and the straight line passing through these end points forms an angle of 4° with the nearest separation plane on each side;

[0117] - The second center line is defined by two end points, and the straight line passing through these end points forms an angle of 10° with the nearest separation plane on each side.

[0118] In addition, for the rotor of the present invention, when using four pairs of magnetic poles instead of three pairs of magnetic poles:

[0119] - The internal point of the first center line is located at an inner radius of 42.1 mm from the center;

[0120] - The internal point of the second center line is located at an inner radius of 51.19 mm from the center;

[0121] - The first center line is defined by two end points, and the straight line passing through these end points forms an angle of 3.5° with the nearest separation plane on each side;

[0122] - The second center line is defined by two end points, and the straight line passing through these end points forms an angle of 8° with the nearest separation plane on each side.

[0123] Benefiting from the rotor of the present invention with four pairs of magnetic poles, the motor equipped with this rotor can obtain the following performance when using 1.54 kg of magnets:

[0124] - Maximum torque: 274 N.m

[0125] - Maximum power: 194 kW

[0126] - Power at maximum voltage: 147 kW

[0127] The following densities are thus obtained:

[0128] - Magnet mass torque density: 178 N.m / kg magnet

[0129] - Magnet mass power density: 126 kW / kg magnet

[0130] Compared with the motor according to the prior art, the motor has about 20% improvement in torque density and about 15% improvement in power density compared with the motor of the prior art, which proves the advantages of the rotor according to the present invention.

Claims

1. A rotor (2) for an electric machine, the rotor comprising: - a rotor body formed by a stack of laminations, the rotor body being preferably configured to be positioned on a rotor shaft, the rotor body being defined by a cylindrical inner surface having an inner diameter and a cylindrical outer surface having an outer diameter, and - a plurality of pairs of magnetic poles, the plurality of pairs of magnetic poles being circumferentially distributed on the rotor body, consecutive magnetic poles being separated by radial separation planes (P1, P2), each magnetic pole comprising at least two flux barriers radially one above the other, each flux barrier comprising at least one groove (5a, 5b, 6, 7a, 7b, 8, 9), each magnetic pole comprising at least one permanent magnet in the groove. It is characterized in that the center lines (L1, L2) of the first and second flux barriers of each magnetic pole counted from the center of the rotor to the outside are uninterrupted concave lines. In the cross-section, each center line (L1, L2) intersects the cylindrical outer surface of the rotor body at two end points (10, 11), and has a radial symmetry axis (AA). And the intersection point of each center line (L1, L2) and the radial symmetry axis (AA) of the center line is an internal point (12) located at the inner radius of the center of the rotor body. The inner radius Ri1 of the internal point (12) of the center line (L1) of the first barrier satisfies R int +(R ext -R int )·(0.105·p + 0.147 - 0.05) ≤ Ri1 ≤ R int +(R ext -R int )·(0.105·p + 0.147 + 0.05), and the inner radius Ri2 of the internal point of the center line of the second barrier satisfies R int +(R ext -R int )·(0.066·p + 0.519 - 0.05) ≤ Ri2 ≤ R int +(R ext -R int )·(0.066·p + 0.519 + 0.05), where p is the number of pole pairs, R ext is half of the outer diameter of the rotor body, and R int is half of the inner diameter of the rotor body.

2. The rotor according to claim 1, wherein a radial line through each end point (10, 11) of the center line (L1) of the first flux barrier forms an angle (θ) between 21° / (2*p) and 31° / (2*p) with the nearest radial separation plane (P1, P2), and a radial line through each end point of the center line (L2) of the second flux barrier forms an angle between 57° / (2*p) and 67° / (2*p) with the nearest radial separation plane (P1, P2).

3. The rotor according to any one of the preceding claims, wherein each flux barrier comprises zero, one, two or three permanent magnets.

4. The rotor according to any one of the preceding claims, wherein the permanent magnet has a curved shape or a rectangular shape adapted to the shape of the flux barrier.

5. The rotor according to any one of the preceding claims, wherein each magnetic pole of the rotor body comprises three or four flux barriers.

6. The rotor according to claim 5, wherein the first and second flux barriers counted from the center outwards each have three grooves (5a, 5b, 6, 7a, 7b, 8), one of the three grooves being a central groove (6, 8), and the other two of the three grooves being lateral grooves (5a, 5b, 7a, 7b), the third flux barrier having two grooves (9), and the fourth flux barrier having two grooves if present.

7. The rotor according to claim 6, wherein the first flux barrier comprises three permanent magnets, one in each groove (5a, 5b, 6), the second flux barrier comprises two permanent magnets, one in each lateral groove (7a, 7b), and the third flux barrier and the fourth flux barrier, if present, do not comprise permanent magnets.

8. The rotor according to any one of the preceding claims, wherein the number p of pairs of magnetic poles is from 2 to 9 pairs, preferably from 3 to 6 pairs, more preferably 4 pairs.

9. The rotor according to any one of the preceding claims, wherein the width of the flux barrier can be constant or can decrease from the internal point (12) towards the radial ends (10, 11).

10. An electric machine comprising a stator (1) and a rotor (2) according to any one of the preceding claims, the rotor (2) being received within the stator (1).

11. The motor according to claim 10, wherein the motor is a synchronous reluctance motor.

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