Rotor for rotating electric machines having flux barriers arranged among bridges

Abstract

A rotor for a synchronous reluctance machine includes a rotor core having a plurality of magnetically conductive laminations stacked in a rotor axial direction. The magnetically conductive laminations include cut-out portions forming a plurality of flux barriers radially alternated by flux paths portions, where at least one of the flux barriers includes a ridge connecting two flux paths portions adjacent to the at least one flux barrier. The at least one flux barrier has a first barrier mid-line, which is a line that is equidistant from both sides of the at least one flux barrier. The bridge has a second bridge mid-line, which is the line that is equidistant from both sides of the bridge. The first and second mid-lines intersect. The bridge has a first and second symmetry axis and is non-symmetrical with respect to at least one of the first and second symmetry axis.

Claims

1. A rotor for a synchronous reluctance machine comprising a rotor core having a plurality of magnetically conductive laminations stacked in a rotor axial direction, wherein said magnetically conductive laminations comprise cut-out portions forming a plurality of flux barriers radially alternated by flux paths portions, at least one of said flux barriers comprising a first and a second bridge (i) connecting two flux paths portions adjacent to said at least one flux barrier and (ii) defining an internal space in said at least one flux barrier, the internal space (i) housing a permanent magnet and (ii) providing a thermal barrier to protect the permanent magnet during a casting process of the rotor, said at least one flux barrier having a first barrier mid-line which is a line that is equidistant from both sides of said at least one flux barrier, said bridge having a second bridge mid-line which is a line that is equidistant from both sides of said bridge, said first and second mid-lines intersecting at an intersection point, said bridge having a first symmetry axis and a second symmetry axis, said first symmetry axis being defined as a straight line tangential to said first barrier mid-line and passing through said intersection point, said second symmetry axis being defined as the straight line orthogonal to said first symmetry axis and passing through said intersection point, said bridge being non-symmetrical with respect to at least one of said first and second symmetry axis.

2. The rotor according to claim 1, wherein said bridge is non-symmetrical with respect to said first symmetry axis and symmetrical with respect to said second symmetry axis.

3. The rotor according to claim 2, wherein both sides of said bridge are substantially curved.

4. The rotor, according to claim 1, wherein said bridge is symmetrical with respect to said first symmetry axis and non-symmetrical with respect to said second symmetry axis.

5. The rotor according to claim 4, wherein both sides of said bridge are substantially curved.

6. The rotor according to claim 1, wherein said bridge is non-symmetrical with respect to both said first symmetry axis and said second symmetry axis.

7. The rotor according to claim 6, wherein both sides of said bridge are substantially curved.

8. The rotor according to claim 1, wherein both sides of said bridge are substantially curved.

9. The rotor according to claim 1, wherein the internal space includes air.

10. The rotor according to claim 9, wherein the air within the internal space provides the thermal barrier to protect the permanent magnet from high temperatures during the casting process of the rotor.

11. The rotor according to claim 9, wherein said internal space in said at least one flux barrier is provided dedicated locks for locking the permanent magnet inside said at least one of said flux barriers.

12. The rotor according to claim 1, wherein the internal space in said at least one flux barrier is provided dedicated locks for locking the permanent magnet inside said at least one of said flux barriers.

13. The rotor according to claim 1, further comprising a support for said bridge.

14. The rotor according to claim 13, wherein said support for said bridge comprises a first straight portion connecting a first end of said bridge with a second end of said bridge, and a second straight portion connecting an intermediate point of said first straight portion with an intermediate point of said bridge.

15. The rotor according to claim 1, wherein at least a part of said flux barriers is filled with an electrically conductive and magnetically non-conductive material creating a cage inside said rotor core.

16. A rotating machine comprising the rotor according to claim 1.

Description

(1) Further features and advantages of the present invention will be more clear from the description of preferred but not exclusive embodiments of a rotor for a rotating electric machine according to the invention, shown by way of examples in the accompanying drawings, wherein:

(2) FIG. 1 is a perspective view of a first embodiment of a lamination for a rotor for an electric machine according to the invention;

(3) FIG. 2 is a view of a detail of a second embodiment of a lamination for a rotor for an electric machine according to the invention;

(4) FIG. 3 is a view of a detail of a third embodiment of a lamination for a rotor for an electric machine according to the invention;

(5) FIG. 4 is a view of a detail of a fourth embodiment of a lamination for a rotor for an electric machine according to the invention;

(6) FIG. 5 is a view of a detail of a fifth embodiment of a lamination for a rotor for an electric machine according to the invention;

(7) FIG. 6 is a view of a detail of a sixth embodiment of a lamination for a rotor for an electric machine according to the invention;

(8) FIG. 7 is a view of a detail of a seventh embodiment of a lamination for a rotor for an electric machine according to the invention

(9) In the following detailed description and in the attached FIGS. 2-7, for sake of simplicity, the present invention will be described with reference to a detail of a lamination showing only a flux barrier FB and two adjacent flux paths FP portions. Also, in FIG. 1 a lamination for a rotor for a four poles synchronous reluctance electrical machine is shown. The same structure and principles can of course be replicated in rotors having a different number of poles and in which the laminations can have any number of flux barrier FB and flux paths FP portions, depending on the needs and the design of the machine.

(10) With reference to the attached figures, in its more general definition, a rotor for a synchronous reluctance machine according to the present invention comprises a rotor core having a plurality of magnetically conductive laminations generally designated in the attached figure with the reference numbers 1 to 6.

(11) According to known design principles, the magnetically conductive laminations 1, 2, 3, 4, 5, 6 are stacked in a rotor axial direction to form a rotor core and comprise cut-out portions 11, 21, 31, 41, 51, 61 forming a plurality of flux barriers FB radially alternated by flux paths FP portions.

(12) One of the characterizing features of the rotor for a synchronous reluctance machine according to the present invention is given by the fact that at least one of said flux barriers FB comprises a bridge 12, 22, 32, 42, 521, 522, 621, 622 which connects two flux paths FP portions adjacent to said at least one flux barrier FB.

(13) A further characterizing feature of a synchronous reluctance machine according to the present invention is given by the fact that said bridge 12, 22, 32, 42, 521, 522, 621, 622 is non-symmetrical with respect to at least one of a first 150, 250, 350, 450 and second symmetry axis 160, 260, 360, 460.

(14) For the purposes of the present invention, the first and second symmetry axis will be now defined with reference to a lamination having the bridge configuration shown in FIG. 2. The first and second symmetry axis can be similarly defined for the laminations shown in the other figures, and in general for other laminations in which the flux barriers are provided with curved bridges.

(15) Thus, with reference to FIG. 2, the magnetically conductive lamination 2 comprises a cut-out portion 21 forming a flux barrier FB radially alternating the flux paths FP portions. The flux barriers FB 21 comprises a bridge 22 which connects the two flux paths FP portions adjacent to said flux barrier FB 21.

(16) As shown in FIG. 2, the flux barrier FB 21 has a first (barrier) mid-line 210 which is represented by a line that is equidistant from both sides of said at least one flux barrier 21.

(17) Similarly, said bridge 22 has a second (bridge) mid-line 220 which is the line that is equidistant from both sides of said bridge 22, and the first 210 and second 220 mid-lines intersect each other at an intersection point IC 230.

(18) One of the characterizing features of the rotor of the present invention is given by the fact that said bridge 22 has a first symmetry axis 250 and a second symmetry axis 260. According to the present invention, with reference to FIG. 2, the first symmetry axis 250 is defined as the straight line tangential to said first (barrier) mid-line 210 and passing through said intersection point 230, while the second symmetry axis 260 is defined as the straight line orthogonal to said first symmetry axis 250 and passing through said intersection point 230.

(19) Thus, in a lamination for a rotor according to the present invention, the bridge 22 is non-symmetrical with respect to at least one of said first 250 and second symmetry axis 260. Specifically, with reference to FIG. 2, the bridge 22 of the embodiment shown in said figure is non-symmetrical with respect to both said first 250 and second symmetry axis 260.

(20) In general, and considering also the other figures, the rotor of the present invention is therefore characterized in that the bridges 12, 22, 32, 42, 521, 522, 621, 622 have a first symmetry axis 150, 250, 350, 450 and a second symmetry axis 160, 260, 360, 460, and in that said bridges 12, 22, 32, 42, 521, 522, 621, 622 are non-symmetrical with respect to at least one of said first 150, 250, 350, 450 and second symmetry axis 160, 260, 360, 460.

(21) Similarly to what explained with reference to FIG. 2, in the embodiments shown in the FIGS. 3-6, the flux barriers 11, 31 and 41 have a first (barrier) mid-line (not shown) which is considered as the line that is equidistant from both sides of the flux barrier 11, 31 and 41. Also, the bridges 12, 32 and 42 have a second (bridge) mid-line (not shown) which is considered as the line that is equidistant from both sides of the bridge 12, 32 and 42, said first (barrier) mid-line and said second (bridge) mid-line intersecting each other at the intersection points 130, 330, and 430.

(22) Then, the first symmetry axis 150, 350, 450 are defined as the straight line tangential to the first (barrier) mid-line (not shown in FIG. 3-6, but defined in a way similar to the mid-line 210 of FIG. 2) and passing through the intersection points 130, 330 and 430, while the second symmetry axis 160, 360, and 460 are defined as the straight line orthogonal to said first symmetry axis 150, 350, and 450 and passing through said intersection point 130, 330, and 430.

(23) With reference to FIG. 3, the bridge 12 of the embodiment shown in said figure is symmetrical with respect to said first symmetry axis 150 and non-symmetrical with respect to second symmetry axis 160. In practice, in the embodiment of FIG. 3 the half bridge on the right-hand side of the first axis 150 overlap the half bridge on the left-hand side of the axis 150 when mirrored with respect to said first axes 150, while the part of the bridge above the second axis 160 does not overlap the part of the bridge below the second axis 160 when mirrored with respect to said second axes 160.

(24) With reference to FIG. 4 the bridge 32 of the embodiment shown in said figure is non-symmetrical with respect to both said first symmetry axis 350 and said second symmetry axis 360. In practice, in the embodiment of FIG. 4 the half bridge on the right-hand side of the first axis 350 does not overlap the half bridge on the left-hand side of the axis 350 when mirrored with respect to said first axes 350, and the part of the bridge above the second axis 360 does not overlap the part of the bridge below the second axis 360 when mirrored with respect to said second axes 360.

(25) Similarly, with reference to FIG. 5 the bridge 42 of the embodiment shown in said figure is non-symmetrical with respect to both said first symmetry axis 450 and said second symmetry axis 460. Thus, also in the case of FIG. 5 the half bridge on the right-hand side of the first axis 450 does not overlap the half bridge on the left-hand side of the axis 450 when mirrored with respect to said first axes 450, and the part of the bridge above the second axis 460 does not overlap the part of the bridge below the second axis 460 when mirrored with respect to said second axes 460.

(26) In general, although not shown in the attached figures, embodiments in which the bridge is non-symmetrical with respect to said first symmetry axis and symmetrical with respect to said second symmetry axis are also possible.

(27) Preferably, as shown in the attached figures, both sides of said bridge 12, 22, 32, 42, 521, 522, 621, 622 are substantially curved. For the purposes of the present invention the substantially curved sides are those delimiting the bridge 12, 22, 32, 42, 521, 522, 621, 622 with respect to the corresponding flux barrier 11, 21, 31, 41, 51, 61.

(28) In particularly preferred embodiments of the rotor according to the present invention, shown e.g. in FIGS. 1, 6 and 7, at least one of said flux barriers FB 11, 51, and 61 comprises a first 521, 621 and a second bridge 522, 622 which connect two flux paths FP portions adjacent to said at least one flux barrier 11, 51, and 61.

(29) Thus, as shown for instance in details in FIGS. 6 and 7, in such a case the bridges 521, 522 and 621, 622 define an internal space, respectively 53 and 630, in said flux barrier FB, respectively 51 and 61.

(30) Said internal space 53, 630 is typically aimed at housing one or more permanent magnets PM (55). As previously said, this solution offers thermal protection of magnets during the casting process, if magnets are inserted before casting. Indeed, with reference for instance to the embodiment of FIG. 6, the air between the bridges 521, 522 and the magnet 55 acts as a thermal barrier (increased with respect to the previous variation), which can be sized according to needs.

(31) With reference to FIGS. 6 and 7, when permanent magnets are present in the rotor, in a particular embodiment of the rotor according to the present invention, the internal space 53, 630 in said flux barrier 51, 61 is provided locking means for locking one or more permanent magnets PM inside said flux barrier 51, 61.

(32) For instance, with reference to FIG. 6 the internal space 53 can be conveniently provided with a first 56 and a second 57 rib spaced apart at a distance substantially corresponding to the length of the magnet 55, so that the magnet 55 is kept in place inside the internal space 53 of the flux barrier 51. Depending on the design of the rotor, other solutions for locking the magnet into place inside the flux barriers are also possible.

(33) With reference to FIG. 7 in a particular embodiment of the rotor according to the present invention, the lamination 6 can be conveniently provided with a support for said bridge.

(34) In particular, in correspondence of each bridge 621 and 622, the lamination 6 comprise a supporting structure 631 and 632 for the corresponding bridge, aimed at maximizing the mechanical strength of the lamination, and consequently of the rotor, for applications in which the arch-shaped bridge alone could not be able to withstand the forces, such as in high speed applications.

(35) In the embodiment shown in FIG. 7, each support 631, 632 for the corresponding bridge 621, 622 comprises a first straight portion 651, 661 which connects a first end of the corresponding bridge 621, 622 with a second end of said bridge 621, 622. Each support 631, 632 further comprises a second straight portion 652, 662 which connects an intermediate point of said first straight portion 651, 661 with an intermediate point of the corresponding bridge 621, 622.

(36) In this way the mechanical strength of the lamination, and consequently of the rotor, is greatly improved. The embodiment shown is just an example of possible support and reinforcing structures. Depending on the design of the rotor, other solutions for reinforcing the lamination are also possible.

(37) A rotating machine, in particular a synchronous reluctance machine, more in particular a PM-assisted synchronous reluctance machine, comprising a rotor as described herein is also part of the present invention.

(38) Several variations can be made to the rotor for a synchronous reluctance machine thus conceived, all falling within the scope of the attached claims. In practice, the materials used and the contingent dimensions and shapes can be any, according to requirements and to the state of the art.