Rotor assembly and self-starting permanent magnet synchronous reluctance motor

Abstract

The present application provides a rotor assembly and a self-starting permanent magnet synchronous reluctance motor. The rotor assembly comprises a rotor core (1), in a transverse section perpendicular to the central axis of the rotor core (1), each pole of the rotor core (1) comprises at least two layers of mounting grooves (2) arranged at intervals along the radial direction, a permanent magnet (3) is installed in the mounting groove (2), and q-axis cage grooves (4) are respectively arranged at both ends of the mounting groove (2), the width of the q-axis cage groove (4) decreases along the direction close to the q-axis, and the length of the q-axis cage groove (4) increases along the direction close to the q-axis. According to the rotor assembly of the present application, the area difference of the cage groove can be reduced, the cage resistance imbalance can be reduced, and the motor starting synchronization capability can be improved.

Description

Technical Field

[0001] The present application relates to the technical field of motors, and in particular to a rotor assembly and a self-starting permanent magnet synchronous reluctance motor. Background Art

[0002] The self-starting permanent magnet synchronous reluctance motor combines the structural characteristics of the induction motor and the synchronous permanent magnet reluctance motor. It starts by generating torque through squirrel cage induction, and runs at a constant speed through the difference in magnetic flux between the rotor d and q axes and the torque generated by the permanent magnet. It can be directly connected to the power supply to start. The self-starting permanent magnet synchronous reluctance motor can use the reluctance torque to increase the motor output torque. Compared with the self-starting permanent magnet motor, the amount of permanent magnets used is reduced and the cost is reduced. Compared with the asynchronous motor, the self-starting permanent magnet synchronous reluctance motor has high efficiency and constant synchronous speed, and the speed does not change with the load.

[0003] Traditional permanent magnet motors and permanent magnet synchronous reluctance motors require drivers for starting and controlling operation, which is costly and complex to control. In addition, the driver accounts for a portion of the loss, reducing the efficiency of the entire motor system.

[0004] The Chinese invention patent with patent publication number CN 107834800 A provides a controller-free self-starting permanent magnet assisted synchronous reluctance motor, which reduces the use of permanent magnet materials; however, its cast aluminum cage area is small and the cage design is unreasonable, resulting in unbalanced cage resistance and poor motor starting synchronization capability. Summary of the invention

[0005] Therefore, the technical problem to be solved by the present application is to provide a rotor assembly and a self-starting permanent magnet synchronous reluctance motor, which can reduce the area difference of the squirrel cage slots, reduce the unbalance of the squirrel cage resistance, and improve the motor starting synchronization capability.

[0006] In order to solve the above problems, the present application provides a rotor assembly, including a rotor core. In a transverse cross-section perpendicular to the central axis of the rotor core, each pole of the rotor core includes at least two layers of radially spaced mounting grooves, permanent magnets are installed in the mounting grooves, and q-axis squirrel cage slots are respectively arranged at both ends of the mounting grooves. The width of the q-axis squirrel cage slot decreases along the direction close to the q-axis, and the length of the q-axis squirrel cage slot increases along the direction close to the q-axis.

[0007] Preferably, the q-axis squirrel cage groove extends along the q-axis direction.

[0008] Preferably, the mounting grooves located in the same layer and the q-axis squirrel cage grooves at both ends thereof together form a magnetic barrier layer.

[0009] Preferably, the mounting slots, the q-axis squirrel cage slots and the permanent magnets are symmetrically distributed with respect to the d-axis.

[0010] Preferably, along the radial outward direction, the length of the permanent magnet is L11, L12, ..., wherein L11≤L12...; and / or, along the radial outward direction, the width of the permanent magnet is W11, W12, ..., wherein W11≤W12...

[0011] Preferably, the sum of the widths W of all permanent magnets under the same pole accounts for 0.15-0.45 of the radial effective width W1 of the rotor core, and the radial effective width W1 of the rotor core is the radial width between the outer circle of the central axis hole of the rotor core and the outer circle of the rotor core.

[0012] Preferably, when the permanent magnet is a rare earth permanent magnet, 0.15*W1<W<0.25*W1; when the permanent magnet is a ferrite, 0.25*W1<W<0.45*W1.

[0013] Preferably, the width of the magnetic conductive channel between adjacent q-axis cage slots is W4, and the width of the magnetic conductive channel between two mounting slots corresponding to the adjacent q-axis cage slots is W5, wherein W4≥W5.

[0014] Preferably, at least one side of at least part of the q-axis cage slots has a cut edge, and the cut edge is located at an end of the q-axis cage slots close to the outer circumference of the rotor.

[0015] Preferably, the angle between the cut edge and the extension line of the groove edge of the q-axis squirrel cage groove corresponding to the cut edge is a, wherein 10°≤a≤50°.

[0016] Preferably, a d-axis squirrel cage slot is further provided on the rotor core, and the d-axis squirrel cage slot is located on a side of the q-axis squirrel cage slot close to the d-axis.

[0017] Preferably, there are a plurality of d-axis cage slots, and the minimum distance between adjacent d-axis cage slots is greater than the radial thickness of the permanent magnet located at the outermost radial side.

[0018] Preferably, the d-axis cage groove extends in a circumferential direction.

[0019] Preferably, the q-axis squirrel cage slot and the d-axis squirrel cage slot are filled with conductive but non-magnetic material.

[0020] Preferably, cage end rings are provided at both ends of the rotor core, and the cage end rings cover all the cage slots and connect the cage slots to form a cage.

[0021] Preferably, the total area of ​​the q-axis cage slot and the d-axis cage slot is S1, and the total area of ​​all cage slots and all mounting slots is S, wherein S1≥0.4*S.

[0022] Preferably, 0.5*S≤S1≤0.8*S.

[0023] Preferably, the cross-sectional shape of the q-axis cage slot and the mounting slot is rectangular or arc-shaped.

[0024] According to another aspect of the present application, a self-starting permanent magnet synchronous reluctance motor is provided, comprising a rotor assembly, which is the above-mentioned rotor assembly.

[0025] Preferably, the self-starting permanent magnet synchronous reluctance motor also includes a stator, an air gap is formed between the stator and the rotor assembly, there are dividing ribs between the q-axis squirrel cage slot and the mounting slot and between the q-axis squirrel cage slot and the outer circle of the rotor, the width of the dividing rib is L6, and the radial width of the air gap is δ, where 0.5δ≤L6≤1.5δ.

[0026] The rotor assembly provided by the present application includes a rotor core, in a transverse section perpendicular to the central axis of the rotor core, each pole of the rotor core includes at least two layers of mounting grooves spaced apart in a radial direction, a permanent magnet is mounted in the mounting groove, and q-axis cage grooves are respectively arranged at both ends of the mounting groove, the width of the q-axis cage groove decreases along the direction close to the q-axis, and the length of the q-axis cage groove increases along the direction close to the q-axis. In the rotor assembly of the present application, the width of the q-axis cage groove decreases along the direction close to the q-axis, and the length of the q-axis cage groove increases along the direction close to the q-axis. On the one hand, the cage slot area can be increased, and the asynchronous torque at high speed can be increased; on the other hand, the area difference of each q-axis cage slot is reduced, the cage resistance imbalance is reduced, the negative sequence asynchronous torque is further reduced, and the torque and pull-in torque during the motor starting process are increased, which is helpful to improve the motor starting ability. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic structural diagram of a rotor assembly according to an embodiment of the present application;

[0028] Figure 2 This is a structural dimension diagram of a rotor assembly according to an embodiment of the present application;

[0029] Figure 3 An axial view of a rotor assembly according to an embodiment of the present application;

[0030] Figure 4 This is a structural dimension diagram of a rotor assembly according to an embodiment of the present application;

[0031] Figure 5 A torque curve comparison diagram of the motor in the embodiment of the present application and the motor in the related art;

[0032] Figure 6 The figure is a speed curve diagram of the starting process of the motor of the embodiment of the present application and the motor in the related art.

[0033] The reference numerals are:

[0034] 1. Rotor core; 2. Mounting slot; 3. Permanent magnet; 4. Q-axis cage slot; 5. D-axis cage slot; 6. Shaft hole; 7. Splitting rib; 8. Cutting edge; 9. Cage end ring; 10. Rivet hole; 11. Baffle; 12. Rivet. DETAILED DESCRIPTION

[0035] See also Figures 1 to 6 As shown, according to an embodiment of the present application, the rotor assembly includes a rotor core 1. In a transverse section perpendicular to the central axis of the rotor core 1, each pole of the rotor core 1 includes at least two layers of mounting grooves 2 arranged radially at intervals, and permanent magnets 3 are installed in the mounting grooves 2. Both ends of the mounting grooves 2 are respectively provided with q-axis cage grooves 4, and the width of the q-axis cage grooves 4 decreases along the direction close to the q-axis, and the length of the q-axis cage grooves 4 increases along the direction close to the q-axis.

[0036] In the rotor assembly of the present application, the width of the q-axis squirrel cage slot 4 decreases along the direction approaching the q-axis, so the closer to the q-axis, the smaller the width of the q-axis squirrel cage slot 4, and the length of the q-axis squirrel cage slot 4 increases along the direction approaching the q-axis, which will make the q-axis squirrel cage slot 4 closer to the q-axis and extend longer into the interior of the rotor core 1. Therefore, the increase in the length of the q-axis squirrel cage slot 4 can be used to compensate for the decrease in width. On the one hand, the squirrel cage slot area can be increased to increase the asynchronous torque at high speed; on the other hand, the area difference of each q-axis squirrel cage slot 4 is reduced, the unbalanced cage resistance is reduced, the negative sequence asynchronous torque is further reduced, the torque and pull-in torque during motor starting are increased, and it helps to improve the motor starting ability.

[0037] In order to facilitate the description of the structure of the rotor assembly, the following embodiments are described by taking the example that each pole includes three layers of mounting grooves 2 .

[0038] In this embodiment, along the direction away from the q-axis, the widths of the q-axis cage slot 4 are W21, W22, and W23, and the lengths are L21, L22, and L23, respectively, wherein W21<W22<W23, L21>L22>L23, and the cross-sectional areas of the q-axis cage slot 4 are S11, S12, and S13, respectively, wherein S11≈L21*W21, S12≈L22*W22, and S13≈L23*W23. Since the width of the three-layer q-axis cage slot 4 is smaller and the length is longer, S11, S12, and S13 are relatively close, the area difference is smaller, and the cage resistance imbalance is also smaller, thereby effectively improving the starting performance of the motor.

[0039] The q-axis cage slot 4 extends along the q-axis direction, that is, the extension direction of the q-axis cage slot is parallel to the q-axis direction. The extension direction of the q-axis cage slot 4 is generally along the q-axis, which can reduce its obstruction to the q-axis magnetic flux, and the magnetic flux is easier to enter the stator, which can effectively increase the magnetic resistance torque.

[0040] The mounting slots 2 located on the same layer and the q-axis cage slots 4 at both ends thereof together form a magnetic barrier layer. In this embodiment, the magnetic barrier layer is arranged in at least two layers in the radial direction of the rotor core 1, which can ensure that the magnetic barrier layer can reach a sufficient number of layers, so that the d-axis magnetic resistance of the motor is increased, more permanent magnet magnetic fields flow toward the q-axis, the difference between the d-axis inductance and the q-axis inductance is increased, the motor salient pole difference is increased, and the magnetic resistance torque is increased.

[0041] In one embodiment, the mounting slots 2 , the q-axis cage slots 4 and the permanent magnets 3 are symmetrically distributed with respect to the d-axis or the q-axis.

[0042] In one embodiment, along the radially outward direction, the lengths of the permanent magnets 3 are L11, L12, ..., wherein L11≤L12. ... Taking the three-layer mounting slot 2 as an example, the permanent magnets 3 are also three layers, and the lengths of the permanent magnets 3 are L11, L12, L13, wherein L11≤L12≤L13, that is, the length of the outer layer permanent magnets 3 is greater than or equal to the length of the adjacent inner layer permanent magnets 3.

[0043] Along the radial outward direction, the width of the permanent magnet 3 is W11, W12, ..., wherein W11≤W12. ... Taking the three-layer installation slot 2 as an example, the permanent magnet 3 is also three-layered, and the width of the permanent magnet 3 is W11, W12, W13, wherein W11≤W12≤W13.

[0044] By limiting the relationship between the length and width of the permanent magnet 3 along the radial direction, the anti-demagnetization capability of the permanent magnet 3 can be improved while effectively utilizing the permanent magnet 3 to improve the motor torque.

[0045] The sum W of the widths of all permanent magnets 3 under the same pole accounts for 0.15 to 0.45 of the radial effective width W1 of the rotor core 1. The radial effective width W1 of the rotor core 1 is the radial width between the outer circle of the central axis hole 6 of the rotor core 1 and the outer circle of the rotor core 1. Taking the three-layer mounting slot 2 as an example, the sum W of the widths of all permanent magnets 3 = W13 + W12 + W11.

[0046] When the permanent magnet 3 is a rare earth permanent magnet 3, 0.15*W1<W<0.25*W1; when the permanent magnet 3 is a ferrite, 0.25*W1<W<0.45*W1.

[0047] Rare earth permanent magnets have strong remanence and strong resistance to demagnetization, so they are thinner and can reduce the amount of permanent magnets used; ferrite permanent magnets have low remanence and poor resistance to demagnetization, so they are thicker and can improve the motor's anti-demagnetization ability while ensuring motor efficiency.

[0048] The width of the magnetic channel between adjacent q-axis cage slots 4 is W4, and the width of the magnetic channel between two mounting slots 2 corresponding to the adjacent q-axis cage slots 4 is W5, where W4≥W5, so that the width of the magnetic channel can be matched with its position, avoiding excessive saturation of the magnetic channel and improving motor efficiency.

[0049] At least one side of at least part of the q-axis cage slots 4 has a cut edge 8 , and the cut edge 8 is located at one end of the q-axis cage slots 4 close to the outer circumference of the rotor.

[0050] The angle between the cut edge 8 and the extended line of the slot edge of the q-axis cage slot 4 corresponding to the cut edge 8 is a, where 10°≤a≤50°. The cut edge 8 can make the magnetic flux enter the stator gradually, reduce the sudden change of magnetic flux, and reduce the torque pulsation of the motor.

[0051] The rotor core 1 is also provided with a d-axis cage slot 5, which is located on the side of the q-axis cage slot 4 close to the d-axis. In this embodiment, the d-axis cage slot 5 is located in a groove formed by the radially outermost q-axis cage slot 4 and the mounting groove 2, the opening of the groove faces the outer circle of the rotor, and the d-axis cage slot 5 is closer to the d-axis than the q-axis cage slot 4.

[0052] In one embodiment, there are multiple d-axis cage slots 5, and the minimum distance W3 between adjacent d-axis cage slots 5 is greater than the radial thickness of the permanent magnet 3 located at the radially outermost side. When the mounting slots 2 are three layers, the radial thickness of the permanent magnet 3 at the radially outermost side is W13, and W3>W13. This limitation can effectively avoid the problem of over-saturation of the permanent magnet 3 at the magnetic conductive channel between adjacent d-axis cage slots 5.

[0053] In one embodiment, the d-axis cage slot 5 extends along the circumferential direction.

[0054] The q-axis cage slot 4 and the d-axis cage slot 5 are filled with a conductive but non-magnetic material. In one embodiment, the conductive but non-magnetic material is, for example, aluminum or an aluminum alloy.

[0055] The cage slots include q-axis cage slots 4 and d-axis cage slots 5. The total area of ​​the cage slots filled with conductive and non-magnetic materials is S1, that is, the total area of ​​the q-axis cage slots 4 and d-axis cage slots 5 is S1. The total area of ​​all cage slots and all mounting slots 2 is S, where S1≥0.4*S.

[0056] As a preferred embodiment, 0.5*S≤S1≤0.8*S.

[0057] The rotor core 1 is provided with cage end rings 9 at both ends, which cover all cage slots and connect the cage slots to form a cage. The cage end rings 9 are, for example, die-cast cage end rings. All cage slots refer to all q-axis cage slots 4 and all d-axis cage slots 5.

[0058] The squirrel cage can help the motor start, and the larger squirrel cage slot area can effectively improve the motor starting synchronization capability.

[0059] See also Figure 6 As shown, the motor of the related art has insufficient pull-in torque and loses speed when approaching synchronous speed, while the self-starting permanent magnet synchronous reluctance motor using the technology of the present application can be smoothly pulled into synchronization.

[0060] Non-magnetic baffles 11 are provided at both ends of the rotor core 1. Rivets 12 are inserted through rivet holes 10 to fix the baffles 11 on the rotor core 1 to block and fix the permanent magnets 3. The permanent magnets 3 can also be fixed by injecting injection molding material into the installation groove 2 and solidifying it. The injection molding material is a non-conductive and non-magnetic material.

[0061] from Figure 5 It can be seen that compared with the motors in related technologies, the self-starting permanent magnet synchronous reluctance motor using the technology of the present application has an increased average torque and reduced torque pulsation under the same stator and current, and the technical effect is better.

[0062] The cross-sectional shape of the q-axis cage slot 4 and the mounting slot 2 is a rectangle or an arc. The rectangle or arc here are approximate shapes. For example, in order to facilitate the setting of the q-axis cage slots 4 at both ends, the mounting slot 2 will be designed as a trapezoid, but the overall structure is similar to a rectangle and adopts a straight-side structure.

[0063] According to an embodiment of the present application, a self-starting permanent magnet synchronous reluctance motor includes a rotor assembly, which is the above-mentioned rotor assembly.

[0064] The self-starting permanent magnet synchronous reluctance motor also includes a stator, an air gap is formed between the stator and the rotor assembly, and there are dividing ribs 7 between the q-axis squirrel cage slot 4 and the mounting slot 2 and between the q-axis squirrel cage slot 4 and the outer circle of the rotor. The width of the dividing rib 7 is L6, and the radial width of the air gap is δ, wherein 0.5δ≤L6≤1.5δ.

[0065] By properly setting the width of the dividing rib 7, it is possible to minimize magnetic leakage and improve motor performance while ensuring mechanical strength.

[0066] It is easy for those skilled in the art to understand that, under the premise of no conflict, the above-mentioned advantageous methods can be freely combined and superimposed.

[0067] The above are only preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application. The above are only preferred implementations of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and variations can be made without departing from the technical principles of the present application, and these improvements and variations should also be regarded as the protection scope of the present application.

Claims

1. A rotor assembly, characterized in that: The invention comprises a rotor core (1), wherein in a transverse section perpendicular to the central axis of the rotor core (1), each pole of the rotor core (1) comprises at least two layers of installation grooves (2) arranged at intervals along the radial direction, a permanent magnet (3) is installed in the installation groove (2), and q-axis cage grooves (4) are respectively arranged at both ends of the installation groove (2), the width of the q-axis cage groove (4) decreases along the direction close to the q-axis, and the length of the q-axis cage groove (4) increases along the direction close to the q-axis.

2. The rotor assembly according to claim 1, characterized in that: The q-axis squirrel cage groove (4) extends along the q-axis direction.

3. The rotor assembly according to claim 1, characterized in that: The installation grooves (2) located on the same layer and the q-axis squirrel cage grooves (4) at both ends thereof together form a magnetic barrier layer.

4. The rotor assembly according to claim 1, characterized in that: The installation groove (2), the q-axis squirrel cage groove (4) and the permanent magnet (3) are symmetrically distributed relative to the d-axis.

5. The rotor assembly according to claim 1, characterized in that: Along the radial outward direction, the length of the permanent magnet (3) is L11, L12, ..., wherein L11≤L12...; and / or, along the radial outward direction, the width of the permanent magnet (3) is W11, W12, ..., wherein W11≤W12...

6. The rotor assembly according to claim 1, characterized in that The sum W of the widths of all permanent magnets (3) under the same pole accounts for 0.15 to 0.45 of the radial effective width W1 of the rotor core (1), and the radial effective width W1 of the rotor core (1) is the radial width between the outer circle of the central axis hole (6) of the rotor core (1) and the outer circle of the rotor core (1).

7. The rotor assembly according to claim 6, characterized in that When the permanent magnet (3) is a rare earth permanent magnet (3), 0.15*W1<W<0.25*W1; when the permanent magnet (3) is a ferrite, 0.25*W1<W<0.45*W1.

8. The rotor assembly according to claim 1, characterized in that The width of the magnetic conductive channel between adjacent q-axis cage slots (4) is W4, and the width of the magnetic conductive channel between two mounting slots (2) corresponding to the adjacent q-axis cage slots (4) is W5, wherein W4≥W5.

9. The rotor assembly according to claim 1, characterized in that: At least one side of at least part of the q-axis cage slot (4) has a cut edge (8), and the cut edge (8) is located at an end of the q-axis cage slot (4) close to the outer circle of the rotor.

10. The rotor assembly according to claim 9, characterized in that The angle between the cut edge (8) and the extended line of the groove edge of the q-axis squirrel cage groove (4) corresponding to the cut edge (8) is a, wherein 10°≤a≤50°.

11. The rotor assembly according to any one of claims 1 to 10, characterized in that: The rotor core (1) is also provided with a d-axis cage slot (5), and the d-axis cage slot (5) is located on a side of the q-axis cage slot (4) close to the d-axis.

12. The rotor assembly according to claim 11, characterized in that There are a plurality of d-axis cage slots (5), and the minimum distance between adjacent d-axis cage slots (5) is greater than the radial thickness of the permanent magnet (3) located at the radially outermost side.

13. The rotor assembly according to claim 11, characterized in that The d-axis squirrel cage groove (5) extends along the circumferential direction.

14. The rotor assembly according to claim 11, characterized in that The q-axis squirrel cage slot (4) and the d-axis squirrel cage slot (5) are filled with conductive but non-magnetic material.

15. The rotor assembly according to claim 14, characterized in that Cage end rings (9) are provided at both ends of the rotor core (1); the cage end rings (9) cover all the cage slots and connect the cage slots to form a cage.

16. The rotor assembly according to claim 11, characterized in that The total area of ​​the q-axis cage slot (4) and the d-axis cage slot (5) is S1, and the total area of ​​all cage slots and all mounting slots (2) is S, wherein S1≥0.4*S.

17. The rotor assembly according to claim 16, characterized in that 0.5*S≤S1≤0.8*S.

18. The rotor assembly according to any one of claims 1 to 10, characterized in that The cross-sectional shapes of the q-axis squirrel cage groove (4) and the mounting groove (2) are rectangular or arc-shaped.

19. A self-starting permanent magnet synchronous reluctance motor, comprising a rotor assembly, characterized in that: The rotor assembly is the rotor assembly according to any one of claims 1 to 18.

20. The self-starting permanent magnet synchronous reluctance motor according to claim 19, characterized in that: The self-starting permanent magnet synchronous reluctance motor also includes a stator, an air gap is formed between the stator and the rotor assembly, a dividing rib (7) is provided between the q-axis squirrel cage slot (4) and the mounting slot (2) and between the q-axis squirrel cage slot (4) and the outer circle of the rotor, the width of the dividing rib (7) is L6, and the radial width of the air gap is δ, wherein 0.5δ≤L6≤1.5δ.

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