Rotor assembly and alternating pole motor

Abstract

The present application provides a rotor assembly and an alternating pole motor. The rotor assembly comprises a rotor core (1), the rotor core (1) comprises permanent magnetic poles and alternating poles arranged alternately in the circumferential direction, the permanent magnetic poles comprise mounting slots (2), permanent magnets (3) are mounted in the mounting slots (2), the polarities of the permanent magnets (3) facing the outer periphery of the rotor core (1) are the same polarity, the alternating poles comprise an alternating pole center line, a first air slot (4) is arranged on the alternating pole, and the first air slot (4) is arranged on a side of the alternating pole close to the alternating pole center line. According to the rotor assembly of the present application, the problem of increased torque pulsation caused by the rich back-electromotive force harmonic content of the alternating pole motor can be effectively improved, the back-electromotive force harmonic content can be significantly reduced, and the motor performance 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 an alternating-pole motor. Background Art

[0002] The number of permanent magnets used in the alternating-pole permanent magnet synchronous motor is only half of that of the traditional permanent magnet synchronous motor. Therefore, it makes more complete use of the permanent magnets and can significantly reduce the amount of permanent magnets used, thereby reducing the cost of the motor.

[0003] However, its special magnetic circuit structure also brings many problems, including the inconsistent structure of adjacent magnetic poles, which leads to asymmetric distribution of air gap magnetic flux, and then causes high harmonic distortion rate of back EMF. It is no longer a sinusoidal waveform. The non-sinusoidal back EMF interacts with the input sinusoidal current to generate torque, and the torque pulsation will increase, limiting the further promotion and application of alternating pole motors.

[0004] Some alternating pole motors in the prior art improve torque fluctuations by optimizing the pole arc coefficient, mainly targeting the torque fluctuations caused by the tooth slot torque, but have no effect on the torque pulsation caused by non-sinusoidal back EMF. Therefore, they have a poor effect on the problem of increased torque pulsation caused by the rich harmonic content of the back EMF of the alternating pole motor. Summary of the invention

[0005] Therefore, the technical problem to be solved by the present application is to provide a rotor assembly and an alternating pole motor, which can effectively improve the problem of increased torque pulsation caused by the rich back-EMF harmonic content of the alternating pole motor, significantly reduce the back-EMF harmonic content, and improve the motor performance.

[0006] In order to solve the above problems, the present application provides a rotor assembly, including a rotor core, the rotor core including permanent magnetic poles and alternating poles arranged alternately in the circumferential direction, the permanent magnetic poles including mounting grooves, permanent magnets installed in the mounting grooves, the polarities of the permanent magnets facing the outer periphery of the rotor core are the same polarity, the alternating poles include an alternating pole center line, a first air groove is arranged on the alternating pole, and the first air groove is arranged on the side of the alternating pole close to the alternating pole center line.

[0007] Preferably, the first air slot extends in a radial direction of the rotor core.

[0008] Preferably, there are two first air slots, which are respectively arranged on both sides of the center line of the alternating poles.

[0009] Preferably, the two first air slots are symmetrical about the alternating polar center line.

[0010] Preferably, in a plane perpendicular to the central axis of the rotor core, the angle formed by the line connecting the endpoints of the radial outer sides of the two first air slots close to the center line of the alternating poles and the center of the rotor core is a81, and the angle formed by the line connecting the endpoints of the radial outer sides of the two first air slots away from the center line of the alternating poles and the center of the rotor core is a82, where a81 / a82=0.2~0.4.

[0011] Preferably, the relationship between the radial thickness t8 and the circumferential width w8 of the first air groove satisfies t8 / w8=0.2-0.4.

[0012] Preferably, the permanent magnetic pole comprises a magnetic pole center line, and a second air groove is arranged on the magnetic pole center line.

[0013] Preferably, the second air groove extends along the circumferential direction of the rotor core.

[0014] Preferably, the relationship between the radial thickness t6 and the circumferential width w6 of the second air groove satisfies t6 / w6=0.2-0.4.

[0015] Preferably, third air slots are respectively provided on both sides of the magnetic pole center line.

[0016] Preferably, there are two third air slots, and the two third air slots are symmetrical about the center line of the magnetic pole.

[0017] Preferably, the relationship between the radial thickness t6 of the second air groove and the radial thickness t7 of the third air groove satisfies t6 / t7=0.3-0.7.

[0018] Preferably, in a plane perpendicular to the central axis of the rotor core, the angle formed by the line connecting the endpoints of the radial outer sides of the two third air slots close to the magnetic pole centerline and the center of the rotor core is a72, and the angle formed by the line connecting the endpoints of the radial outer sides of the two third air slots away from the magnetic pole centerline and the center of the rotor core is a71, where a72 / a71=0.2~0.4.

[0019] Preferably, fourth air grooves are respectively provided at both ends of the mounting groove, and the side of the fourth air groove close to the magnetic pole center line extends toward the magnetic pole center line to form a first narrow groove, and the side of the fourth air groove away from the magnetic pole center line extends in a direction away from the magnetic pole center line to form a second narrow groove.

[0020] Preferably, in a plane perpendicular to the central axis of the rotor core, the angle formed by the line connecting the endpoints of the two first slots located on the same permanent magnet pole on the radial outside and close to the center line of the magnetic pole and the center of the rotor core is a51, and the angle formed by the line connecting the endpoints of the two second slots located on the same permanent magnet pole on the radial outside and away from the center line of the magnetic pole and the center of the rotor core is a52, where a51 / a52=0.3~0.5.

[0021] Preferably, when the permanent magnet pole includes two third air slots, in a plane perpendicular to the central axis of the rotor core, the angle formed by the line connecting the endpoints of the radially outer sides of the two third air slots away from the center line of the magnetic pole and the center of the rotor core is a71, and the angle formed by the line connecting the endpoints of the radially outer sides of the two first slots located on the same permanent magnet pole close to the center line of the magnetic pole and the center of the rotor core is a51, where a71 / a51=0.3~0.5.

[0022] Preferably, when the permanent magnet pole includes two first air slots, in a plane perpendicular to the central axis of the rotor core, the angle formed by the line connecting the endpoints of the radial outer sides of the two first air slots away from the center line of the alternating pole and the center of the rotor core is a82, and the angle formed by the line connecting the endpoints of the radial outer sides of the two second slots located on both sides of the alternating pole close to the center line of the alternating pole and the center of the rotor core is a53, where a82 / a53=0.1~0.25.

[0023] According to another aspect of the present application, an alternating-pole motor is provided, comprising a rotor assembly and a stator assembly, wherein the rotor assembly is the above-mentioned rotor assembly.

[0024] The rotor assembly provided by the present application includes a rotor core, the rotor core includes permanent magnetic poles and alternating poles arranged alternately along the circumferential direction, the permanent magnetic poles include mounting grooves, permanent magnets are mounted in the mounting grooves, the polarity of the permanent magnets facing the outer periphery of the rotor core is the same polarity, the alternating poles include an alternating pole center line, a first air slot is arranged on the alternating pole, and the first air slot is arranged on the side of the alternating pole close to the alternating pole center line. The rotor assembly can change the magnetic permeability at the center of the alternating pole by adding the first air slot in the middle of the alternating pole, prevent the magnetic density from being too concentrated at this place, improve the distribution of the magnetic lines of force of the alternating pole, and make the distribution of the magnetic lines of force of the alternating pole more uniform, thereby effectively reducing torque fluctuations, improving the problem of increased torque pulsation caused by the rich harmonic content of the back electromotive force of the alternating pole motor, significantly reducing the back electromotive force harmonic content, and improving the motor performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic structural diagram of a rotor assembly according to an embodiment of the present application;

[0026] Figure 2 A comparison diagram of the back electromotive force of the rotor assembly of the embodiment of the present application and the prior art;

[0027] Figure 3 A comparison diagram of back-EMF harmonics between the rotor assembly of the embodiment of the present application and the prior art;

[0028] Figure 4 This is a torque comparison diagram of the rotor assembly of the embodiment of the present application and the prior art.

[0029] The reference numerals are:

[0030] 1. Rotor core; 2. Mounting slot; 3. Permanent magnet; 4. First air slot; 5. Second air slot; 6. Third air slot; 7. Fourth air slot; 8. First narrow slot; 9. Second narrow slot. DETAILED DESCRIPTION

[0031] See also Figures 1 to 4 As shown, according to an embodiment of the present application, the rotor assembly includes a rotor core 1, the rotor core 1 includes permanent magnetic poles and alternating poles arranged alternately in the circumferential direction, the permanent magnetic poles include mounting slots 2, permanent magnets 3 are mounted in the mounting slots 2, the polarities of the permanent magnets 3 facing the outer periphery of the rotor core 1 are the same polarity, the alternating poles include alternating pole center lines, the alternating poles are provided with first air slots 4, and the first air slots 4 are provided on the side of the alternating poles close to the center line of the alternating poles. The first air slots 4 are provided on the side of the alternating poles close to the center line of the alternating poles, which means that, assuming that the alternating poles are divided into two along the center line of the alternating poles, then for the alternating poles located on the first side of the center line of the alternating poles, the first air slots 4 are provided on the side of the alternating poles close to the center line of the alternating poles, and the first air slots 4 can be located on the center line of the alternating poles or on one side of the center line of the alternating poles. It can also be considered that the first air slots 4 are provided in the middle of the circumferential direction of the alternating poles.

[0032] The rotor assembly can change the magnetic permeability at the center of the alternating pole by adding a first air slot 4 in the middle of the alternating pole, thereby preventing the magnetic density from being too concentrated at this point, improving the distribution of the magnetic lines of force of the alternating pole, and making the distribution of the magnetic lines of force of the alternating pole more uniform, thereby effectively reducing torque fluctuations, improving the problem of increased torque pulsation caused by rich back-EMF harmonic content of the alternating-pole motor, significantly reducing the back-EMF harmonic content, and improving motor performance.

[0033] In the present application, by setting the first air slot 4 in the middle part of the alternating pole close to the center line of the alternating pole, the non-sinusoidal back electromotive force in the back electromotive force can be adjusted, the distribution form of the magnetic lines of force can be changed, and the magnetic density distribution can be made more sinusoidal, thereby significantly reducing the harmonic content of the back electromotive force and further reducing the torque pulsation.

[0034] The rotor core 1 adopts a disc slotted structure, which is formed by laminating thin sheets of soft magnetic material. A rotor shaft hole is opened at the center of the rotor core 1. An array of permanent magnet mounting slots 2 are opened on the rotor core 1. The permanent magnet mounting slots 2 are close to the outer edge of the rotor core 1, and the number is equal to the number of alternating poles; a rotor pole shoe is formed between the permanent magnet mounting slots 2 and the outer circle of the rotor. Preferably, in this embodiment, the permanent magnet 3 adopts a straight-line structure.

[0035] Preferably, the first air slot 4 extends in the radial direction of the rotor core 1. Because the magnetic lines of force on the permanent magnetic poles are transmitted radially to the radial direction of the alternating poles and then closed through the rotor core 1, the radial first air slot 4 can guide the magnetic lines of force. If it does not extend radially but extends circumferentially, the magnetic resistance on the alternating poles will be significantly increased, reducing the torque.

[0036] Preferably, there are two first air slots 4, which are respectively arranged on both sides of the center line of the alternating poles. The two first air slots 4 can have the same structure and both extend along the radial direction of the rotor core 1, thereby increasing the back electromotive force, reducing the torque fluctuation, reducing the back electromotive force harmonic content, and improving the motor performance.

[0037] Preferably, the two first air slots 4 are symmetrical about the alternating polar center line.

[0038] Preferably, when there is one first air slot 4, the first air slot 4 is located on the center line of the alternating poles.

[0039] In a plane perpendicular to the central axis of the rotor core 1, the angle formed by the line connecting the endpoints of the radial outer sides of the two first air slots 4 close to the center line of the alternating poles and the center of the rotor core 1 is a81, and the angle formed by the line connecting the endpoints of the radial outer sides of the two first air slots 4 away from the center line of the alternating poles and the center of the rotor core 1 is a82, where a81 / a82=0.2~0.4.

[0040] By reasonably setting the value of a81 / a82, it is possible to avoid the inner edges of the two first air slots 4 being too close to each other to cause magnetic saturation. At the same time, it is possible to avoid the outer edges of the two first air slots being too far apart to cause the magnetic flux density on both sides of the alternating poles to be too concentrated. This can more effectively reduce the magnetic flux density on the center line of the alternating pole, improve the magnetic flux density distribution, and reduce torque fluctuations.

[0041] Preferably, the relationship between the radial thickness t8 and the circumferential width w8 of the first air slot 4 satisfies t8 / w8=0.2-0.4. Because the main advantage of the first air slot 4 is to change the magnetic permeability at the center of the alternating pole, thereby improving the magnetic flux density distribution, if the ratio t8 / w8 is too small, it means that t8 is too small or w8 is too large, and t8 is too small, which is obviously not enough to improve the magnetic flux density distribution at this location, and w8 is too large, which will obviously increase the magnetic resistance in the circumferential direction of the alternating pole excessively, affecting the torque; similarly, if the ratio t8 / w8 is too large, it means that t8 is too large or w8 is too small, and t8 is too large, which will also increase the magnetic resistance in the radial direction of the alternating pole, affecting the torque, and if w8 is too small, it will not be enough to improve the magnetic flux density distribution, so setting t8 / w8=0.2-0.4 can effectively improve the magnetic flux density distribution while not excessively increasing the magnetic resistance on the alternating pole and affecting the torque.

[0042] The permanent magnetic pole includes a magnetic pole center line, and a second air slot 5 is arranged on the magnetic pole center line. In this embodiment, the second air slot 5 is arranged at a position close to the outer periphery of the rotor core 1 and is symmetrical about the magnetic pole center line. By arranging the second air slot 5 on the magnetic pole center line, the magnetic flux density on the permanent magnetic pole at the magnetic pole center line can be reduced, and the magnetic flux density asymmetry between adjacent magnetic poles can be further avoided, thereby reducing torque fluctuations, and also reducing even harmonics caused by magnetic flux density asymmetry, such as Figure 3 shown.

[0043] Preferably, the second air groove 5 extends along the circumferential direction of the rotor core 1 .

[0044] The third air slots 6 are respectively arranged on both sides of the center line of the magnetic pole, and the second air slots 5 are located radially outside the third air slots 6. A gap is formed between the two third air slots 6, so the magnetic lines of force are affected by the two third air slots 6 after being emitted from the permanent magnet 3, and are gathered and concentrated on the rotor core 1 between the two third air slots 6, and then affected by the second air slots 5 located on the center line of the alternating poles. The gathered magnetic lines of force cannot pass through the position of the second air slots 5, so they are dispersed and pass through both sides of the second air slots 5, thereby realizing the aggregation and dispersion process of the magnetic lines of force, and effectively improving the distortion of the magnetic lines of force.

[0045] Preferably, there are two third air slots 6, and the two third air slots 6 are symmetrical about the center line of the magnetic pole. The third air slot 6 can effectively prevent the magnetic lines of force from being too concentrated on both sides of the second air slot 5, and make the magnetic density more uniform by changing the distribution of the magnetic lines of force, thereby improving the distribution of the magnetic lines of force on the permanent magnetic pole together with the second air slot 5, making the magnetic density more uniform and reducing torque fluctuation.

[0046] The first air slot 4, the second air slot 5 and the third air slot 6 cooperate with each other to form a combined optimization of the alternating poles and the permanent magnet poles, so that the improvement of the torque fluctuation is not only concentrated on the permanent magnet poles, but also reflected in the alternating poles, thereby ensuring that the optimization of the torque fluctuation will not change with the change of the rotor rotation position, not only can the torque fluctuation of the permanent magnet motor during the rotation process be reduced, but also can ensure that the torque fluctuation can be optimized during the entire rotation process of the rotor assembly, further improving the motor performance and improving the motor working stability.

[0047] The fourth air slot 7 is provided at both ends of the mounting slot 2. The side of the fourth air slot 7 close to the magnetic pole center line extends toward the magnetic pole center line to form a first slot 8. The side of the fourth air slot 7 away from the magnetic pole center line extends in a direction away from the magnetic pole center line to form a second slot 9. Preferably, the first slot 8 and the second slot 9 have the same structure and extend in opposite directions. The first slot 8 and the second slot 9 change the magnetic permeability on the permanent magnetic pole and the alternating pole, making the magnetic flux density distributed between the permanent magnetic pole and the alternating pole more uniform and symmetrical, and effectively reducing the torque fluctuation.

[0048] In this embodiment, the relationship between the radial thickness t6 and the circumferential width w6 of the second air slot 5 satisfies t6 / w6=0.2-0.4. The second air slot 5 cannot be too close to the outer periphery of the rotor to avoid forming a too narrow magnetic bridge, which makes the magnetic bridge flux too concentrated, affects the magnetic flux distribution, and further affects the motor performance; at the same time, the thickness and width of the second air slot 5 cannot be too large to avoid increasing the magnetic flux between the second air slot 5 and the two third air slots 6 and reducing the strength of the punching sheet, so the ratio of t6 and w6 needs to satisfy t6 / w6=0.2-0.4.

[0049] Preferably, the relationship between the radial thickness t6 of the second air slot 5 and the radial thickness t7 of the third air slot 6 satisfies t6 / t7=0.3~0.7, thereby effectively ensuring the strength of the punching sheet and the magnetic flux density distribution between the permanent magnet poles, avoiding excessive magnetic flux density, causing magnetic flux asymmetry between adjacent magnetic poles, and causing torque fluctuation.

[0050] In a plane perpendicular to the central axis of the rotor core 1, the angle formed by the end points of the radial outer sides of the two third air slots 6 close to the magnetic pole centerline and the line connecting the center of the rotor core 1 is a72, and the angle formed by the end points of the radial outer sides of the two third air slots 6 far from the magnetic pole centerline and the line connecting the center of the rotor core 1 is a71, wherein a72 / a71=0.2-0.4. By setting the circumferential width of the two third air slots 6 and their circumferential spacing, the strength of the punching sheet and the magnetic flux density distribution between the permanent magnet poles can be further guaranteed, and the magnetic flux density is prevented from being too large, causing the magnetic flux density between adjacent magnetic poles to be asymmetric, and causing torque fluctuation.

[0051] When the permanent magnet pole includes two third air slots 6, in a plane perpendicular to the central axis of the rotor core 1, the angle formed by the line connecting the end points of the radial outer sides of the two third air slots 6 away from the magnetic pole center line and the center of the rotor core 1 is a71, and the angle formed by the line connecting the end points of the radial outer sides of the two first slots 8 located on the same permanent magnet pole close to the magnetic pole center line and the center of the rotor core 1 is a51, where a71 / a51=0.3~0.5.

[0052] The simulation shows that when the three ratio ranges of t6 / t7=0.3~0.7, a72 / a71=0.2~0.4 and a71 / a51=0.3~0.5 are met, the back EMF peak is larger and the waveform is more sinusoidal, such as Figure 2 As shown, the torque is greater, such as Figure 4 shown.

[0053] In a plane perpendicular to the central axis of the rotor core 1, the angle formed by the end points of the radially outer side of the two first slots 8 located at the same permanent magnetic pole close to the magnetic pole centerline and the line connecting the center of the rotor core 1 is a51, and the angle formed by the end points of the radially outer side of the two second slots 9 located at the same permanent magnetic pole away from the magnetic pole centerline and the line connecting the center of the rotor core 1 is a52, wherein a51 / a52=0.3~0.5. The positions of the first slot 8 and the second slot 9 close to the outer periphery of the rotor core 1 cannot be too close to prevent magnetic saturation. In addition, the first slot 8 and the second slot 9 cannot extend too far to both sides to avoid excessive concentration of magnetic flux on the permanent magnetic pole. Therefore, the ratio of a51 and a52 needs to satisfy a51 / a52=0.3~0.5, so as to avoid excessive concentration of magnetic flux on the permanent magnetic pole while avoiding magnetic saturation, thereby improving the working performance of the motor.

[0054] When the permanent magnetic pole includes two first air slots 4, in a plane perpendicular to the central axis of the rotor core 1, the angle formed by the line connecting the end points of the radial outer side of the two first air slots 4 far from the center line of the alternating pole and the center of the rotor core 1 is a82, and the angle formed by the line connecting the end points of the radial outer side of the two second slots 9 located on both sides of the alternating pole close to the center line of the alternating pole and the center of the rotor core 1 is a53, wherein a82 / a53=0.1-0.25. Setting this angle can ensure that the alternating pole yoke between the first air slot 4 and the second slot 9 has a certain circumferential width, which will not be too large or too small. Whether a82 is too large or a53 is too small, the circumferential width on the alternating pole yoke will be reduced, the magnetic resistance will be increased, and the magnetic lines of force emitted from the permanent magnetic pole will pass through the alternating pole yoke and close through the rotor core. If a82 is too small or a53 is too large, the magnetic flux distribution cannot be fully and effectively improved, thereby achieving the purpose of reducing torque fluctuation.

[0055] According to an embodiment of the present application, an alternating-pole motor includes a rotor assembly and a stator assembly, and the rotor assembly is the above-mentioned rotor assembly.

[0056] It is easy for those skilled in the art to understand that the above-mentioned advantageous methods can be freely combined and superimposed without conflict.

[0057] 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), the rotor core (1) comprising permanent magnetic poles and alternating poles arranged alternately in a circumferential direction, the permanent magnetic poles comprising mounting grooves (2), permanent magnets (3) being mounted in the mounting grooves (2), the polarities of the permanent magnets (3) facing the outer periphery of the rotor core (1) being the same polarity, the alternating poles comprising alternating pole center lines, the alternating poles being provided with first air grooves (4), the first air grooves (4) being provided on a side of the alternating poles close to the alternating pole center lines; The permanent magnetic pole comprises a magnetic pole center line, a second air slot (5) is arranged on the magnetic pole center line, and the second air slot (5) extends along the circumferential direction of the rotor core (1); third air slots (6) are arranged on both sides of the magnetic pole center line, the second air slots (5) are located radially outside the third air slots (6), and gaps are formed between the third air slots (6); In a plane perpendicular to the central axis of the rotor core (1), an angle formed by a line connecting the end points of the radial outer sides of the two third air slots (6) close to the magnetic pole centerline and the center of the rotor core (1) is a72, and an angle formed by a line connecting the end points of the radial outer sides of the two third air slots (6) away from the magnetic pole centerline and the center of the rotor core (1) is a71, wherein a72 / a71=0.2~0.

4.

2. The rotor assembly according to claim 1, characterized in that: The first air slot (4) extends in the radial direction of the rotor core (1).

3. The rotor assembly according to claim 1, characterized in that: There are two first air slots (4), which are respectively arranged on both sides of the alternating pole center line.

4. The rotor assembly according to claim 3, characterized in that: The two first air grooves (4) are symmetrical about the alternating polar center line.

5. The rotor assembly according to claim 3, characterized in that: In a plane perpendicular to the central axis of the rotor core (1), an angle formed by a line connecting the end points of the radial outer sides of the two first air slots (4) close to the alternating pole centerline and the center of the rotor core (1) is a81, and an angle formed by a line connecting the end points of the radial outer sides of the two first air slots (4) away from the alternating pole centerline and the center of the rotor core (1) is a82, wherein a81 / a82=0.2~0.

4.

6. The rotor assembly according to claim 3, characterized in that: The relationship between the radial thickness t8 and the circumferential width w8 of the first air groove (4) satisfies t8 / w8=0.2-0.

4.

7. The rotor assembly according to claim 1, characterized in that The relationship between the radial thickness t6 and the circumferential width w6 of the second air groove (5) satisfies t6 / w6=0.2-0.

4.

8. The rotor assembly according to claim 1, characterized in that There are two third air slots (6), and the two third air slots (6) are symmetrical about the magnetic pole center line.

9. The rotor assembly according to claim 8, characterized in that The relationship between the radial thickness t6 of the second air groove (5) and the radial thickness t7 of the third air groove (6) satisfies t6 / t7=0.3-0.

7.

10. The rotor assembly according to any one of claims 1 to 9, characterized in that: Fourth air grooves (7) are respectively provided at both ends of the mounting groove (2); a side of the fourth air groove (7) close to the magnetic pole center line extends toward the magnetic pole center line to form a first narrow groove (8); and a side of the fourth air groove (7) away from the magnetic pole center line extends in a direction away from the magnetic pole center line to form a second narrow groove (9).

11. The rotor assembly according to claim 10, characterized in that In a plane perpendicular to the central axis of the rotor core (1), an angle formed by a line connecting the end points of the radially outer sides of the two first slots (8) located at the same permanent magnetic pole and close to the magnetic pole centerline and the center of the rotor core (1) is a51, and an angle formed by a line connecting the end points of the radially outer sides of the two second slots (9) located at the same permanent magnetic pole and away from the magnetic pole centerline and the center of the rotor core (1) is a52, wherein a51 / a52=0.3~0.

5.

12. The rotor assembly according to claim 10, characterized in that When the permanent magnetic pole includes two third air slots (6), in a plane perpendicular to the central axis of the rotor core (1), the angle formed by the line connecting the end points of the radial outer sides of the two third air slots (6) away from the magnetic pole centerline and the center of the rotor core (1) is a71, and the angle formed by the line connecting the end points of the radial outer sides of the two first narrow slots (8) located on the same permanent magnetic pole and close to the magnetic pole centerline and the center of the rotor core (1) is a51, wherein a71 / a51=0.3~0.

5.

13. The rotor assembly according to claim 10, characterized in that When the permanent magnet pole comprises two first air slots (4), in a plane perpendicular to the central axis of the rotor core (1), an angle formed by a line connecting the end points of the radial outer sides of the two first air slots (4) away from the center line of the alternating pole and the center of the rotor core (1) is a82, and an angle formed by a line connecting the end points of the radial outer sides of the two second slots (9) located on both sides of the alternating pole and close to the center line of the alternating pole and the center of the rotor core (1) is a53, wherein a82 / a53=0.1~0.

25.

14. An alternating-pole motor, comprising a rotor assembly and a stator assembly, characterized in that: The rotor assembly is the rotor assembly according to any one of claims 1 to 13.

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