Rotor assembly and self-starting permanent magnet synchronous reluctance motor

Abstract

The invention 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 a central axis of the rotor core (1), each pole of the rotor core (1) comprises at least two layers of mounting grooves (2) which are arranged at intervals along a radial direction, two ends of each mounting groove (2) are respectively provided with q-axis squirrel cage grooves (4), at least one side of at least part of the q-axis squirrel cage grooves (4) is provided with a cut edge (8), and the cut edge (8) is provided with a gap (9). And the cutting edge (8) is positioned at one end, close to the outer circle of the rotor, of the q-axis squirrel cage groove (4). According to the rotor assembly provided by the invention, the trimming can enable the magnetic flux to enter the stator step by step, thereby reducing the sudden change of the magnetic flux, and reducing the torque pulsation of the motor.

Description

[0001] This application is a divisional application of a Chinese invention patent application with an application date of January 26, 2021, an application number of 202110109635.5, and an invention title of "Rotor Assembly and Self-Starting Permanent Magnet Synchronous Reluctance Motor". Technical Field

[0002] This application relates to the technical field of motors, and particularly relates to a rotor assembly and a self-starting permanent magnet synchronous reluctance motor. Background Art

[0003] The self-starting permanent magnet synchronous reluctance motor combines the structural characteristics of an induction motor and a synchronous permanent magnet reluctance motor. It generates torque through squirrel-cage induction to achieve starting, and realizes constant-speed operation through the flux difference between the d-axis and q-axis of the rotor and the torque generated by the permanent magnet. It can be directly powered on to achieve starting and operation. The self-starting permanent magnet synchronous reluctance motor can use reluctance torque to increase the motor output torque. Compared with the self-starting permanent magnet motor, the amount of permanent magnet used is reduced and the cost is decreased; compared with the asynchronous motor, the self-starting permanent magnet synchronous reluctance motor has high efficiency, and the speed is constant and synchronous, and the speed does not change with the load.

[0004] Traditional permanent magnet motors and permanent magnet synchronous reluctance motors require a driver for starting and control operation, which has high cost, complex control, and the driver occupies a part of the loss, resulting in a decrease in the efficiency of the entire motor system.

[0005] Chinese invention patent with a patent publication number of CN 107834800 A provides a controllerless self-starting permanent magnet assisted synchronous reluctance motor, which reduces the use of permanent magnet materials; however, the cast aluminum squirrel-cage area is small and the squirrel-cage design is unreasonable, resulting in unbalanced squirrel-cage resistance and poor motor starting synchronization ability. In addition, the design of the squirrel-cage structure is not optimized enough, causing the magnetic flux entering the stator to mutate, resulting in a relatively large motor torque ripple. Summary of the Invention

[0006] Therefore, the technical problems to be solved by this application are 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 unbalanced squirrel-cage resistance, and improve the motor starting synchronization ability.

[0007] The technical problems to be solved by this application are to provide a rotor assembly and a self-starting permanent magnet synchronous reluctance motor, which can make the magnetic flux enter the stator gradually, reduce the magnetic flux mutation, and reduce the motor torque ripple.

[0008] To solve the above problems, the present application provides a rotor assembly, which is applied to a self-starting permanent magnet synchronous reluctance motor and includes 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 mounting grooves arranged at intervals in the radial direction. Q-axis squirrel cage grooves are respectively arranged at both ends of the mounting grooves. At least one side of at least part of the Q-axis squirrel cage grooves has a cutting edge, and the cutting edge is located at one end of the Q-axis squirrel cage groove close to the outer circle of the rotor.

[0009] In some embodiments, the angle between the cutting edge and the extended line of the groove edge of the Q-axis squirrel cage groove corresponding to the cutting edge is a, where 10° ≤ a ≤ 50°.

[0010] In some embodiments, the width of the Q-axis squirrel cage groove decreases along the direction close to the Q-axis, and the length of the Q-axis squirrel cage groove increases along the direction close to the Q-axis.

[0011] In some embodiments, the Q-axis squirrel cage groove extends along the Q-axis direction.

[0012] In some embodiments, the mounting groove in the same layer and the Q-axis squirrel cage grooves at both ends thereof together form a magnetic barrier layer.

[0013] In some embodiments, permanent magnets are installed in the mounting grooves, and the mounting grooves, the Q-axis squirrel cage grooves, and the permanent magnets are symmetrically distributed with respect to the d-axis.

[0014] In some embodiments, along the radially outward direction, the lengths of the permanent magnets are L11, L12... in sequence, where L11 ≤ L12...; and / or, along the radially outward direction, the widths of the permanent magnets are W11, W12... in sequence, where W11 ≤ W12....

[0015] In some embodiments, the cross-sectional shapes of the Q-axis squirrel cage grooves and the mounting grooves are rectangular or arc-shaped.

[0016] The present invention also provides a self-starting permanent magnet synchronous reluctance motor, including a rotor assembly, characterized in that the rotor assembly is the above-mentioned rotor assembly.

[0017] In some embodiments, the self-starting permanent magnet synchronous reluctance motor further 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 grooves and the mounting grooves and between the Q-axis squirrel cage grooves 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.

[0018] The rotor assembly provided by the present application includes 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 mounting grooves arranged at intervals in the radial direction. Q-axis squirrel-cage grooves are respectively arranged at both ends of the mounting grooves. At least one side of at least part of the Q-axis squirrel-cage grooves has a cutting edge, and the cutting edge is located at one end of the Q-axis squirrel-cage groove close to the outer circle of the rotor. The cutting edge can enable the magnetic flux to enter the stator step by step, reduce the magnetic flux mutation, and reduce the torque ripple of the motor. Description of the Drawings

[0019] Figure 1 It is a schematic structural diagram of a rotor assembly according to an embodiment of the present application;

[0020] Figure 2 It is a structural dimension diagram of a rotor assembly according to an embodiment of the present application;

[0021] Figure 3 It is an axial view of a rotor assembly according to an embodiment of the present application;

[0022] Figure 4 It is a structural dimension diagram of a rotor assembly according to an embodiment of the present application;

[0023] Figure 5 It is a comparison diagram of torque curves of the motor according to an embodiment of the present application and the motor in the related art;

[0024] Figure 6 It is a rotational speed curve diagram of the starting process of the motor according to an embodiment of the present application and the motor in the related art.

[0025] The reference numerals are shown as:

[0026] 1. Rotor core; 2. Mounting groove; 3. Permanent magnet; 4. Q-axis squirrel-cage groove; 5. D-axis squirrel-cage groove; 6. Shaft hole; 7. Partition rib; 8. Cutting edge; 9. Squirrel-cage end ring; 10. Rivet hole; 11. Baffle; 12. Rivet. Detailed Embodiments

[0027] With reference to 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 cross-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 at intervals in the radial direction. Permanent magnets 3 are installed in the mounting grooves 2. Q-axis squirrel-cage grooves 4 are respectively arranged at both ends of the mounting grooves 2. The width of the Q-axis squirrel-cage grooves 4 decreases along the direction close to the Q-axis, and the length of the Q-axis squirrel-cage grooves 4 increases along the direction close to the Q-axis.

[0028] For the rotor assembly of the present application, the width of the q-axis squirrel-cage slot 4 decreases along the direction close to the q-axis. Therefore, 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 close to the q-axis, which will also make the q-axis squirrel-cage slot 4 extend deeper into the rotor core 1 as it gets closer to the q-axis. Therefore, the increase in the length of the q-axis squirrel-cage slot 4 can be used to make up for the decrease in width. On the one hand, it can increase the squirrel-cage slot area and increase the asynchronous torque at high speeds; on the other hand, it can reduce the area difference of each q-axis squirrel-cage slot 4, reduce the squirrel-cage resistance imbalance, further reduce the negative-sequence asynchronous torque, increase the torque and pull-in torque during the motor starting process, and contribute to improving the motor starting ability.

[0029] To facilitate the description of the structure of the rotor assembly, the following embodiments will be described by taking three layers of mounting slots 2 per pole as an example.

[0030] In this embodiment, along the direction away from the q-axis, the widths of the q-axis squirrel-cage slots 4 are W21, W22, and W23 in sequence, and the lengths are L21, L22, and L23 in sequence, where W21 < W22 < W23 and L21 > L22 > L23. The cross-sectional areas of the q-axis squirrel-cage slots 4 are S11, S12, and S13 in sequence, where S11 ≈ L21 * W21, S12 ≈ L22 * W22, and S13 ≈ L23 * W23. Since the widths of the three layers of q-axis squirrel-cage slots 4 are smaller and the lengths are longer, S11, S12, and S13 are relatively close, the area difference is small, and the squirrel-cage resistance imbalance is also small, effectively improving the motor starting performance.

[0031] The q-axis squirrel-cage slot 4 extends along the q-axis direction, that is, the extension direction of the q-axis squirrel-cage slot is parallel to the q-axis direction. The extension direction of the q-axis squirrel-cage slot is generally along the q-axis, which can reduce its obstruction to the q-axis magnetic flux, and the magnetic flux can more easily enter the stator, effectively increasing the reluctance torque.

[0032] The mounting slot 2 and the q-axis squirrel-cage slots 4 at its two ends on the same layer together form a magnetic barrier layer. In this embodiment, at least two layers of magnetic barrier layers are arranged in the radial direction of the rotor core 1, which can ensure that the magnetic barrier layer can reach a sufficient number of layers, increase the d-axis reluctance of the motor, make more permanent magnet magnetic fields flow to the q-axis, increase the difference between the d-axis inductance and the q-axis inductance, increase the motor saliency ratio, and increase the reluctance torque.

[0033] In one embodiment, the mounting slot 2, the q-axis squirrel-cage slot 4, and the permanent magnet 3 are symmetrically distributed with respect to the d-axis or the q-axis.

[0034] In one embodiment, along the radially outward direction, the lengths of the permanent magnets 3 are L11, L12, …… in sequence, where L11 ≤ L12 ……. Taking the three-layer mounting groove 2 as an example, the permanent magnets 3 are also in three layers, and the lengths of the permanent magnets 3 are L11, L12, L13 in sequence, where L11 ≤ L12 ≤ L13, that is, the length of the outer-layer permanent magnet 3 is greater than or equal to the length of the adjacent inner-layer permanent magnet 3.

[0035] Along the radially outward direction, the widths of the permanent magnets 3 are W11, W12, …… in sequence, where W11 ≤ W12 ……. Taking the three-layer mounting groove 2 as an example, the permanent magnets 3 are also in three layers, and the widths of the permanent magnets 3 are W11, W12, W13 in sequence, where W11 ≤ W12 ≤ W13.

[0036] By defining the relationship between the length and width of the permanent magnet 3 along the radial direction, while effectively utilizing the permanent magnet 3 to improve the motor torque, the demagnetization resistance of the permanent magnet 3 can be improved.

[0037] The sum W of the widths of all the permanent magnets 3 under the same pole accounts for 0.15 - 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 shaft hole 6 of the rotor core 1 and the outer circle of the rotor core 1. Taking the three-layer mounting groove 2 as an example, the sum W of the widths of all the permanent magnets 3 = W13 + W12 + W11.

[0038] 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.

[0039] The rare-earth permanent magnet has a strong remanence and a strong demagnetization resistance, so the thickness is small, and the amount of permanent magnet used can be reduced; the ferrite permanent magnet has a low remanence and a poor demagnetization resistance, so the thickness is large. While ensuring the motor efficiency, the motor demagnetization resistance is improved.

[0040] The width of the magnetic conduction channel between adjacent q-axis squirrel-cage slots 4 is W4, and the width of the magnetic conduction channel between the two mounting grooves 2 corresponding to the adjacent q-axis squirrel-cage slots 4 is W5, where W4 ≥ W5, so that the width of the magnetic conduction channel can be matched with its position, avoiding excessive saturation of the magnetic conduction channel and improving the motor efficiency.

[0041] At least one side of at least part of the q-axis squirrel-cage slots 4 has a trimming edge 8, and the trimming edge 8 is located at one end of the q-axis squirrel-cage slot 4 close to the outer circle of the rotor.

[0042] The angle between the trimming edge 8 and the extended line of the slot edge of the q-axis squirrel-cage slot 4 corresponding to the trimming edge 8 is a, where 10° ≤ a ≤ 50°. The trimming edge 8 can make the magnetic flux enter the stator step by step, reduce the magnetic flux mutation, and reduce the motor torque ripple.

[0043] The rotor core 1 is also provided with a d-axis squirrel cage slot 5, and the d-axis squirrel cage slot 5 is located on the side of the q-axis squirrel cage slot 4 closer to the d-axis. In this embodiment, the d-axis squirrel cage slot 5 is located in the groove formed by the q-axis squirrel cage slot 4 at the outermost radial side and the mounting groove 2. The opening of this groove faces the rotor outer circle, and the d-axis squirrel cage slot 5 is closer to the d-axis than the q-axis squirrel cage slot 4.

[0044] In one embodiment, there are multiple d-axis squirrel cage slots 5, and the minimum distance W3 between adjacent d-axis squirrel cage slots 5 is greater than the radial thickness of the outermost permanent magnet 3 in the radial direction. When the mounting groove 2 has three layers, the radial thickness of the outermost permanent magnet 3 in the radial direction is W13, and W3 > W13. Such a limitation can effectively avoid the problem of excessive saturation of the permanent magnet 3 at the magnetic conduction channel between adjacent d-axis squirrel cage slots 5.

[0045] In one embodiment, the d-axis squirrel cage slot 5 extends in the circumferential direction.

[0046] The q-axis squirrel cage slot 4 and the d-axis squirrel cage slot 5 are filled with a conductive and non-magnetic material. In one embodiment, the conductive and non-magnetic material is, for example, aluminum or aluminum alloy.

[0047] The squirrel cage slots include the q-axis squirrel cage slot 4 and the d-axis squirrel cage slot 5. The total area of the squirrel cage slots filled with the conductive and non-magnetic material is S1, that is, the total area of the q-axis squirrel cage slot 4 and the d-axis squirrel cage slot 5 is S1. The total area of all the squirrel cage slots and all the mounting grooves 2 is S, where S1 ≥ 0.4 * S.

[0048] As a preferred embodiment, 0.5 * S ≤ S1 ≤ 0.8 * S.

[0049] Squirrel cage end rings 9 are provided at both ends of the rotor core 1. The squirrel cage end rings 9 cover all the squirrel cage slots and connect the squirrel cage slots to form a squirrel cage. The above-mentioned squirrel cage end rings 9 are, for example, die-cast squirrel cage end rings. All the squirrel cage slots refer to all the q-axis squirrel cage slots 4 and all the d-axis squirrel cage slots 5.

[0050] The squirrel cage can assist the motor in starting. A larger area of the squirrel cage slots can effectively improve the starting synchronization ability of the motor.

[0051] Combined with reference to Figure 6 As shown, the motor in the related art has insufficient pull-in torque and speed out-of-step when approaching the synchronous speed, while the self-starting permanent magnet synchronous reluctance motor adopting the technology of this application can smoothly pull into synchronization.

[0052] Non-magnetic baffles 11 are provided at both ends of the rotor core 1. The baffles 11 are fixed on the rotor core 1 by inserting rivets 12 through rivet holes 10 to shield and fix the permanent magnets 3; alternatively, the permanent magnets 3 can be fixed by injecting an injection molding material into the mounting groove 2, and the injection molding material is a non-conductive and non-magnetic material.

[0053] As can be seen from Figure 5 Figure 5 , compared with the motors of the related art, for the self-starting permanent magnet synchronous reluctance motor adopting the technology of the present application, under the same stator and current, the average torque is increased and the torque ripple is reduced, and the technical effect is better.

[0054] The cross-sectional shapes of the q-axis squirrel-cage slots 4 and the mounting slots 2 are rectangular or arc-shaped. Both the rectangle and the arc here are approximate figures. For example, in order to facilitate the setting of the q-axis squirrel-cage slots 4 at both ends, the mounting slots 2 are designed as trapezoids, but the overall structure is similar to that of a rectangle and all adopt straight-edge structures.

[0055] According to an embodiment of the present application, the self-starting permanent magnet synchronous reluctance motor includes a rotor assembly, and the rotor assembly is the above-mentioned rotor assembly.

[0056] The self-starting permanent magnet synchronous reluctance motor further includes a stator. An air gap is formed between the stator and the rotor assembly. There are dividing ribs 7 between the q-axis squirrel-cage slots 4 and the mounting slots 2 and between the q-axis squirrel-cage slots 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, where 0.5δ ≤ L6 ≤ 1.5δ.

[0057] By reasonably setting the width of the dividing rib 7, the magnetic leakage can be minimized as much as possible while ensuring the mechanical strength, and the motor performance can be improved.

[0058] It is easy for those skilled in the art to understand that, on the premise of no conflict, the above advantageous ways can be freely combined and superimposed.

[0059] The above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application. The above is only the preferred implementation manner of the present application. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present application, several improvements and modifications can still be made, and these improvements and modifications should also be regarded as the protection scope of the present application.

Claims

1. A rotor assembly, characterized in that, Applied to a self-starting permanent magnet synchronous reluctance motor, including a rotor core (1). In a transverse cross-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 at intervals in the radial direction. Q-axis squirrel-cage grooves (4) are respectively arranged at both ends of the mounting groove (2). At least one side of at least part of the Q-axis squirrel-cage grooves (4) has a cut edge (8), and the cut edge (8) is located at one end of the Q-axis squirrel-cage groove (4) close to the outer circle of the rotor.

2. The rotor assembly according to claim 1, 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, where 10° ≤ a ≤ 50°.

3. The rotor assembly according to claim 1, characterized in that, The width of the Q-axis squirrel-cage groove (4) decreases along the direction close to the Q-axis, and the length of the Q-axis squirrel-cage groove (4) increases along the direction close to the Q-axis.

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

5. The rotor assembly according to claim 1, characterized in that, The mounting groove (2) in the same layer and the Q-axis squirrel-cage grooves (4) at both ends thereof together form a magnetic barrier layer.

6. The rotor assembly according to claim 1, characterized in that, A permanent magnet (3) is installed in the mounting groove (2), and the mounting groove (2), the Q-axis squirrel-cage groove (4), and the permanent magnet (3) are symmetrically distributed with respect to the d-axis.

7. The rotor assembly according to claim 6, characterized in that, Along the radially outward direction, the lengths of the permanent magnets (3) are L11, L12... in sequence, where L11 ≤ L12...; and / or, along the radially outward direction, the widths of the permanent magnets (3) are W11, W12... in sequence, where W11 ≤ W12....

8. The rotor assembly according to claim 6 or 7, 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.

9. 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 8.

10. The self-starting permanent magnet synchronous reluctance motor according to claim 9, characterized in that, The self-starting permanent magnet synchronous reluctance motor further includes a stator. An air gap is formed between the stator and the rotor assembly. There are dividing ribs (7) between the Q-axis squirrel-cage groove (4) and the mounting groove (2) and between the Q-axis squirrel-cage groove (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, where 0.5δ ≤ L6 ≤ 1.5δ.

Images