CN209948822U - Rotor assembly and alternating-pole motor - Google Patents

Abstract

The application provides a rotor assembly and a consequent pole motor. This rotor subassembly includes rotor core, rotor core includes the permanent magnetism utmost point and the utmost point in turn of arranging along circumference in turn, the permanent magnetism utmost point includes the mounting groove, install the permanent magnet in the mounting groove, the polarity of permanent magnet towards rotor core outer peripheral edges is same polarity, be provided with first air groove and two at least second air grooves on being located the rotor core in the radial outside of mounting groove, first air groove is located the magnetic pole central line, two at least second air grooves set up and are located magnetic pole central line both sides along the circumference interval, along the radial direction of keeping away from rotor core's center, the interval between the lateral wall that is close to the magnetic pole central line of two at least second air grooves is crescent, first air groove is located the expansion region in two at least second air grooves. According to the rotor assembly, the problem of torque pulsation increase caused by abundant back electromotive force harmonic content of the alternating-pole motor can be effectively solved, the back electromotive force harmonic content is remarkably reduced, and the motor performance is improved.

Description

Rotor assembly and alternating-pole motor

Technical Field

The application relates to the technical field of motors, in particular to a rotor assembly and an alternating-pole motor.

Background

The number of the permanent magnets used by the alternating-pole permanent magnet synchronous motor is only half of that of the permanent magnets of the traditional permanent magnet synchronous motor, so that the permanent magnets are utilized more fully, the use amount of the permanent magnets can be reduced remarkably, and the cost of the motor is reduced.

However, the special magnetic circuit structure also brings many problems, including the problems of output torque reduction caused by reduction of the use amount of the permanent magnets and torque fluctuation increase caused by asymmetry of adjacent magnetic pole structures, and further popularization and application of the alternating-pole motor are limited.

Some alternating-pole motors in the prior art improve torque fluctuation by optimizing pole arc coefficients, mainly aiming at torque fluctuation caused by cogging torque, but have no effect on torque pulsation caused by non-sinusoidal back electromotive force, so that the alternating-pole motors have poor effect on the problem of torque pulsation increase caused by rich back electromotive force harmonic content.

SUMMERY OF THE UTILITY MODEL

Therefore, the technical problem to be solved by the application is to provide a rotor assembly and a consequent pole motor, which can effectively solve the problem of torque pulsation increase caused by abundant content of counter electromotive force harmonic of the consequent pole motor, remarkably reduce the content of the counter electromotive force harmonic, and improve the performance of the motor.

In order to solve the above problem, the application provides a rotor assembly, including rotor core, rotor core includes the permanent magnetism pole and the alternative pole of arranging in turn along circumference, the permanent magnetism pole includes the mounting groove, install the permanent magnet in the mounting groove, the polarity of permanent magnet towards rotor core outer peripheral edges is homopolarity, be provided with first air groove and two at least second air grooves on being located the radial outside rotor core of mounting groove, first air groove is located the magnetic pole central line, two at least second air grooves set up and are located magnetic pole central line both sides along circumference interval, along the radial direction of keeping away from rotor core's center, the interval between the lateral wall that is close to the magnetic pole central line of two at least second air grooves increases gradually, first air groove is located the expansion region of two at least second air grooves.

Preferably, the side wall of the second air groove close to the center line of the magnetic pole comprises a straight line section and a bending section, the bending section extends outwards in a direction away from the center line of the magnetic pole, and an expansion area is formed between the opposite bending sections of at least two second air grooves.

Preferably, an extension line of the straight line segment passes through the central axis of the rotor core.

Preferably, the bending section is a straight section or an arc section, and the expansion area is V-shaped or U-shaped.

Preferably, a first extension section which extends circumferentially towards the direction far away from the central line of the magnetic pole is arranged on the rotor core at the tail end of the bending section.

Preferably, in a plane perpendicular to the central axis of the rotor core, an included angle formed by connecting end points of the radial outer edges of the two first extension sections, which are far away from the center line of the magnetic pole, with the center of the rotor core is a22, and an included angle formed by connecting radially outer end points of the two straight-line sections with the center of the rotor core is a21, wherein a21/a22 is 0.15-0.4.

Preferably, in a plane perpendicular to the central axis of the rotor core, an included angle formed by connecting two end points of the radial outer edge of the first air slot and the center of the rotor core is a1, and an included angle formed by connecting two radial outer end points of the two straight line segments and the center of the rotor core is a21, wherein a1/a21 is 0.9-1.1.

Preferably, the radial thickness of the first air groove is t1, the radial thickness of the second air groove is t2, and t1/t2 is 0.1-0.3.

Preferably, the two ends of the mounting groove are respectively provided with a third air groove, and the third air grooves circumferentially extend from the side wall to the center line of the magnetic pole to form a second extending section.

Preferably, in a plane perpendicular to the central axis of the rotor core, the included angle formed by the connection line of the end points of the radial outer edges of the two second extension sections close to the central line of the magnetic poles and the center of the rotor core is a31, and the included angle formed by the connection line of the end points of the radial outer edges of the two third air slots positioned between the adjacent permanent magnetic poles and the center of the rotor core is a32, wherein a31/a32 is 0.8-1.

Preferably, in a plane perpendicular to the central axis of the rotor core, an included angle formed by a connecting line between end points of the radial outer edges of the two second extension sections, which are close to the central line of the magnetic pole, and the center of the rotor core is a31, and an included angle formed by a connecting line between two end points of the radial outer edges of the permanent magnets, which are close to the central line of the magnetic pole, and the center of the rotor core is am, wherein a31/am is 0.7-0.95.

Preferably, when the rotor core is provided with the first extension sections, in a plane perpendicular to the central axis of the rotor core, an included angle formed by a connecting line between end points of the radial outer edges of the two first extension sections, which are far away from the magnetic pole central line, and the center of the rotor core is a22, and an included angle formed by a connecting line between end points of the radial outer edges of the two second extension sections, which are close to the magnetic pole central line, and the center of the rotor core is a31, wherein a22/a31 is 0.4-0.6.

Preferably, the permanent magnet is V-shaped.

Preferably, the number of the second air grooves is two, and the two second air grooves are symmetrical about the center line of the magnetic pole.

According to another aspect of the present application there is provided a consequent pole machine comprising a rotor assembly and a stator assembly, the rotor assembly being as described above.

The utility model provides a rotor subassembly, including rotor core, rotor core includes the permanent magnetism pole and the alternative pole of arranging in turn along circumference, the permanent magnetism pole includes the mounting groove, install the permanent magnet in the mounting groove, the polarity of permanent magnet towards rotor core outer peripheral edges is same polarity, be provided with first air groove and two at least second air grooves on being located the rotor core in the radial outside of mounting groove, first air groove is located the magnetic pole central line, two at least second air grooves set up and are located magnetic pole central line both sides along the circumference interval, along the radial direction of keeping away from rotor core's center, the interval between the lateral wall that is close to the magnetic pole central line of two at least second air grooves increases gradually, first air groove is located the expansion region in two at least second air grooves. The rotor component can plan magnetic lines of force passing through a rotor core by arranging a first air groove and two second air grooves, wherein the first air groove and the two second air grooves are positioned on two sides of a magnetic pole center line, the second air groove has the shape characteristic of opening outwards from the center, the first air groove is wrapped in an opening expansion area, the magnetic line of force distribution at the center part of the magnetic pole is adjusted through the second air groove, the magnetic lines of force are gathered at the center part of the magnetic pole and are limited to gather towards one side of the rotating direction, the gathered magnetic lines of force are slowly and slowly divided towards two sides through the first air groove, the phenomenon that the magnetic pole center part is too concentrated is avoided, the increase of counter electromotive force third harmonic is avoided, the peak position of the counter electromotive force is advanced through the matching of the first air groove and the second air groove, the even number harmonic content is reduced, the sine degree of the counter electromotive force is improved, and the problem of torque, the counter potential harmonic content is obviously reduced, and the motor performance is improved.

Drawings

FIG. 1 is a schematic structural view of a rotor assembly according to an embodiment of the present application;

FIG. 2 is a dimensional block diagram of a rotor assembly according to an embodiment of the present application;

FIG. 3 is a magnetic flux distribution diagram of a rotor assembly according to an embodiment of the present application;

FIG. 4 is a graph comparing back emf waveforms for a rotor assembly of an embodiment of the present application and a prior art rotor assembly;

FIG. 5 is a graph comparing back emf harmonic content of rotor assemblies of embodiments of the present application with prior art rotor assemblies;

FIG. 6 is a torque waveform comparison of a rotor assembly of an embodiment of the present application with a prior art rotor assembly;

FIG. 7 is a graph of back emf harmonics, electromagnetic torque content versus a21/a22 for a rotor assembly of an embodiment of the present application;

FIG. 8 is a graph of rotor assembly torque ripple, electromagnetic torque as a function of a22/a31 for an embodiment of the present application.

The reference numerals are represented as:

1. a rotor core; 2. mounting grooves; 3. a permanent magnet; 4. a first air tank; 5. a second air tank; 6. a third air tank; 7. a straight line segment; 8. bending sections; 9. a first extension section; 10. a second extension section; 11. a stator assembly.

Detailed Description

With reference to fig. 1 to 8, according to an embodiment of the present application, the rotor assembly includes a rotor core 1, the rotor core 1 includes permanent magnet poles and alternating poles alternately arranged along a circumferential direction, the permanent magnet poles include a mounting groove 2, a permanent magnet 3 is mounted in the mounting groove 2, polarities of the permanent magnet 3 facing an outer periphery of the rotor core 1 are the same, a first air slot 4 and at least two second air slots 5 are disposed on the rotor core 1 located at a radial outer side of the mounting groove 2, the first air slot 4 is located on a magnetic pole center line, the at least two second air slots 5 are circumferentially spaced and located at two sides of the magnetic pole center line, a distance between sidewalls of the at least two second air slots 5 close to the magnetic pole center line is gradually increased along a radial direction away from a center of the rotor core 1, and the first air slot 4 is located in an expansion area of the at least two second air slots 5. For convenience of description, the structure of the same permanent magnet pole is taken as an example for explanation.

The magnetic force lines on the alternating poles of the alternating pole motor lack the constraint of the permanent magnets, due to armature reaction, the magnetic force lines can be gathered towards the rotating side of the rotor, the position of a counter electromotive force peak value is not aligned with the position of the u-phase winding on the q axis, the counter electromotive force peak value can be delayed a little backward, even-numbered harmonics in the counter electromotive force harmonics are increased, the counter electromotive force distortion is serious, and the torque pulsation is increased due to the fact that the current introduced into the winding is sine wave, and the current and the counter electromotive force with the larger distortion rate are acted.

In the present application, the rotor assembly can plan magnetic lines of force passing through the rotor core 1 by providing the first air slot 4 located on the center line of the magnetic pole and the two second air slots 5 located on both sides of the center line of the magnetic pole, the second air slot 5 has a shape characteristic of being flared outward from the center, and wraps the first air slot 4 in a flared expansion region, adjusts the distribution of the magnetic lines of force in the center of the magnetic pole by the second air slot 5, gathers the magnetic lines of force in the center of the magnetic pole, and limits the magnetic lines of force from gathering to one side of the rotation direction, and gradually converges the magnetic lines of force to both sides by the first air slot 4, so as not to be too concentrated in the center of the magnetic pole, as shown in fig. 3, and simultaneously avoids causing an increase of the counter-potential third harmonic, and advances the peak position of the counter-potential by the cooperation of the first air slot 4 and the, reducing the even harmonic content and increasing the back emf sinusoid as shown in figure 5. By the aid of the mode, the problem of torque pulsation increase caused by abundant counter electromotive force harmonic content of the alternating-pole motor can be effectively solved, the counter electromotive force harmonic content is remarkably reduced, and the performance of the motor is improved.

The side wall of the second air groove 5 close to the central line of the magnetic pole comprises a straight line segment 7 and a bending segment 8, the bending segment 8 extends outwards in a slant direction far away from the central line of the magnetic pole, and an expansion area is formed between the opposite bending segments 8 of at least two second air grooves 5. The bending section 8 extends outwards in a direction oblique to the direction away from the central line of the magnetic pole, specifically, the extending direction of the bending section 8 includes the circumferential direction away from the central line of the magnetic pole and the radial direction away from the center of the rotor core 1, and the bending section extends towards the direction away from the central line of the magnetic pole and away from the center of the rotor core 1.

Because the structure that expands outward of the section of bending 8 can form the expansion region in the middle zone of two sections of bending 8, consequently can conveniently carry out the setting of first air groove 4 for first air groove 4 is located the expansion region, forms the interval simultaneously with the section of bending 8 of circumference direction both sides between, makes the magnetic line of force circulate through the magnetic circuit that the interval department formed.

The first air slot 4 is a long strip extending in the circumferential direction, and the radial outer peripheral wall of the first air slot 4 is arc-shaped with the center of the rotor core 1 as the center. The first air slot 4 is, for example, rectangular, or fan-shaped, or oval, etc. The first air groove 4 may also be circular.

Preferably, the first air slots 4 are symmetrical about the pole center line.

Preferably, the extension line of the straight line segment 7 passes through the central axis of the rotor core 1, so that when magnetic lines enter the magnetic circuit in the middle area of the two straight line segments 7, the magnetic lines can be sorted, and the distribution uniformity of the magnetic lines is improved.

Preferably, the bending section 8 is a straight section 7 or an arc section, and the expansion area is V-shaped or U-shaped. The expanded region may have other shapes as long as it is ensured that the distance between the side walls of the two second air slots 5 close to the pole center line is gradually increased in the direction away from the center axis of the rotor core 1.

Preferably, the rotor core 1 at the end of the bent segment 8 is provided with a first extension segment 9 extending circumferentially in a direction away from the center line of the magnetic pole. In the present embodiment, the first extension 9 is an arc-shaped segment extending in the circumferential direction, and the arc diameter of the radial outer peripheral wall of the first extension 9 is the same as the arc diameter of the radial outer peripheral wall of the first air groove 4, and the radial outer peripheral walls of both are located on the same circumference. The two symmetrical straight line segments 7 are arranged to release gathered magnetic lines and then are handed to the first air groove 4 for further arrangement, so that the distribution of the magnetic lines near the center line of the magnetic pole can be optimized, and counter potential harmonics are reduced.

In a plane perpendicular to the central axis of the rotor core 1, an included angle formed by connecting end points of the radial outer edges of the two first extension sections 9, which are far away from the center line of the magnetic pole, with the center of the rotor core 1 is a22, and an included angle formed by connecting radially outer end points of the two straight sections 7 with the center of the rotor core 1 is a21, wherein a21/a22 is 0.15-0.4. The larger the outer angle of the second air groove 5 is, the larger the space occupied by the second air groove 5 is, the larger the magnetic resistance is formed, and if the magnetic resistance is too large, the sharp drop of the electromagnetic torque is caused. The larger the inner angle of the second air grooves 5 is, the more magnetic lines of force gather in the middle of the magnetic poles, which causes too much distortion of the magnetic flux density waveform, so that it is necessary to set the total circumferential width and the minimum circumferential interval of the two second air grooves 5 appropriately. It is found that when a21/a22 is 0.15 to 0.4, the effects of preventing the magnetic resistance from becoming too large and preventing the distortion of the magnetic dense waveform are exhibited, as shown in fig. 7.

In a plane perpendicular to the central axis of the rotor core 1, an included angle formed by connecting two end points of the radial outer edge of the first air slot 4 with the center of the rotor core 1 is a1, and an included angle formed by connecting a radial outer end point of the two straight line segments 7 with the center of the rotor core 1 is a21, wherein a1/a21 is 0.9-1.1. The large angle of the first air groove 4 blocks the flow of the magnetic lines of force modulated by the second air groove 5, reducing the output torque, and the torque ripple increases. The modulation effect of the first air groove 4 is weakened when the angle is too small, the air gap flux density at the central part of the magnetic pole cannot be effectively weakened, and the flux density at the central part of the magnetic pole protrudes by a sharp angle, namely, the third harmonic is increased. The study shows that the best effect can be obtained when the a1/a21 is 0.9-1.1.

The radial thickness of the first air groove 4 is t1, the radial thickness of the second air groove 5 is t2, and t1/t2 is 0.1-0.3. Researches show that the thickness of the first air groove 4 has an optimal value, so that the air gap flux density at the center of the magnetic pole can be properly weakened, the waveform of the whole flux density is just close to a sine wave, and the harmonic content is minimum. The thickness of the second air slot 5 characterizes the convergence capacity for the magnetic field lines, and there is also an optimum value. Research shows that when t1/t2 is 0.1-0.3, the thickness ratio of the first air groove 4 to the second air groove 5 is optimal, and the air gap flux density waveform and the magnetic force line gathering capacity at the center of the magnetic pole can achieve the excellent effect.

The two ends of the mounting groove 2 are respectively provided with a third air groove 6, and the third air grooves 6 circumferentially extend from the side wall to the center line of the magnetic pole to form a second extending section 10. The third air groove 6 adjusts the symmetry of the magnetic density distribution of the permanent magnet poles and the alternating poles, and the asymmetry of the adjacent magnetic density distribution can be caused no matter which one of the magnetic densities is larger or smaller, so that the increase of the torque fluctuation is caused. Through adding the first air groove 4 and the second air groove 5 in the center of the magnetic pole and enabling the first air groove and the second air groove to interact with the third air groove 6, the magnetic density distribution can be effectively improved, and compared with the prior art, the technical scheme of the application obviously reduces torque fluctuation, as shown in fig. 6.

In a plane perpendicular to the central axis of the rotor core 1, an included angle formed by connecting the end points of the radial outer edges of the two second extension sections 10 close to the central line of the magnetic poles and the center of the rotor core 1 is a31, and an included angle formed by connecting the end points of the radial outer edges of the two third air grooves 6 positioned between the adjacent permanent magnetic poles and the central line of the rotor core 1 is a32, wherein a31/a32 is 0.8-1. The ratio represents the pole-arc ratio of adjacent magnetic poles, the smaller the ratio, the larger the magnetic density amplitude under the permanent magnetic pole, the smaller the magnetic density of the alternate pole, and the asymmetry of the magnetic density, otherwise, the larger the ratio, the wider the pole shoe under the permanent magnetic pole, the smaller the constraint effect on the magnetic force line, the smaller the magnetic density, the larger the magnetic density under the alternate pole, and the asymmetry of the magnetic density is also increased. The study shows that the symmetry of the magnetic density of 0.8-1 is the best when the a31/a32 is equal to the magnetic density of the magnetic material.

In a plane perpendicular to the central axis of the rotor core 1, an included angle formed by connecting end points of the radial outer edges of the two second extension sections 10 close to the magnetic pole central line and the center of the rotor core 1 is a31, and an included angle formed by connecting end points of the radial outer edges of the permanent magnets 3 close to the magnetic pole central line and the center of the rotor core 1 is am, wherein a31/am is 0.7-0.95. If the ratio is too large, effective magnetic flux density cannot be formed under the permanent magnetic pole, if the ratio is too small, the second extension section 10 blocks magnetic force lines too much, the utilization rate of the permanent magnet is low, and researches show that the effect of 0.7-0.95 is best, the effective magnetic flux density can be formed under the permanent magnetic pole, the magnetic force lines can be prevented from being blocked too much, and the utilization rate of the permanent magnet is improved.

When the first extension segments 9 are arranged on the rotor core 1, in a plane perpendicular to the central axis of the rotor core 1, an included angle formed by connecting end points of the radial outer edges of the two first extension segments 9, which are far away from the magnetic pole central line, with the center of the rotor core 1 is a22, and an included angle formed by connecting end points of the radial outer edges of the two second extension segments 10, which are close to the magnetic pole central line, with the center of the rotor core 1 is a31, wherein a22/a31 is 0.4-0.6. The larger the ratio, the more space the second air groove 5 occupies, the greater the resulting magnetic resistance, and the larger the ratio, the more the electromagnetic torque is lowered. Too small a ratio will reduce the number of magnetic lines of force that can be adjusted by the second air slot 5, and thus torque ripple cannot be optimized effectively. The study shows that the effect is best when the a22/a31 is 0.4-0.6, as shown in figure 8.

Preferably, the permanent magnet 3 is V-shaped. In the prior art, the optimization of the torque fluctuation of the alternating-pole motor is mainly concentrated on a linear permanent magnet alternating-pole permanent magnet motor, and the torque fluctuation of the V-shaped permanent magnet alternating-pole motor is difficult to effectively optimize by the conventional strategy due to the large embedding depth of the permanent magnets.

After the scheme of the application is adopted, the progressive magnetic beam arrangement groove combined structure is utilized, magnetic lines of force in the center of the magnetic pole are gathered and then are further adjusted by the second layer of magnetic beam arrangement groove, therefore, the magnetic lines of force can be preliminarily adjusted by utilizing the characteristic that the expansion initial area of the second air groove 5 occupies a small area in the area with large embedding depth, the magnetic lines of force can reach the expansion area under the influence of the second air groove 5, the magnetic lines of force gathered can pass through the adjustment of the first air groove 4 and the second air groove 5 in the expansion area and are slowly distributed to two sides, the magnetic lines of force gathered in the center of the magnetic pole are unlikely to be excessively concentrated, the torque adjustment of the V-shaped permanent magnet becomes practical, the torque fluctuation can be further reduced compared with the prior art, and the working performance of the motor is improved.

Preferably, there are two second air slots 5, and the two second air slots 5 are symmetrical with respect to the center line of the magnetic pole.

The rotor core 1 is formed by laminating soft magnetic material sheets.

According to an embodiment of the present application, the alternating pole machine comprises a rotor assembly, which is the rotor assembly described above, and a stator assembly 11.

It is readily understood by a person skilled in the art that the advantageous ways described above can be freely combined, superimposed without conflict.

The present invention is not intended to be limited to the particular embodiments shown and described, but is to be accorded the widest scope consistent with the principles and novel features herein disclosed. The foregoing is only a preferred embodiment of the present application, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present application, and these modifications and variations should also be considered as the protection scope of the present application.

Claims (15)

1. A rotor assembly is characterized by comprising a rotor core (1), wherein the rotor core (1) comprises permanent magnetic poles and alternating poles which are alternately arranged along the circumferential direction, the permanent magnetic poles comprise mounting grooves (2), permanent magnets (3) are mounted in the mounting grooves (2), the polarities of the permanent magnets (3) facing the outer periphery of the rotor core (1) are the same, first air grooves (4) and at least two second air grooves (5) are arranged on the rotor core (1) which is positioned on the radial outer side of the mounting grooves (2), the first air grooves (4) are positioned on a magnetic pole center line, the at least two second air grooves (5) are circumferentially arranged at intervals and positioned on two sides of the magnetic pole center line, and the distance between the side walls, close to the magnetic pole center line, of the at least two second air grooves (5) is gradually increased along the radial direction far away from the center of the rotor core (1), the first air channel (4) is located in the expansion region of the at least two second air channels (5).

2. The rotor assembly according to claim 1, wherein the side walls of the second air slots (5) close to the pole center line comprise straight sections (7) and bent sections (8), the bent sections (8) extend obliquely outwards away from the pole center line, and the expansion area is formed between the opposite bent sections (8) of the at least two second air slots (5).

3. The rotor assembly according to claim 2, wherein an extension of the straight section (7) passes through a central axis of the rotor core (1).

4. The rotor assembly according to claim 2, wherein the bending section (8) is a straight section (7) or an arc section, and the expansion area is V-shaped or U-shaped.

5. The rotor assembly according to claim 2, wherein the rotor core (1) at the end of the bent section (8) is provided with a first extension section (9) extending circumferentially in a direction away from the center line of the magnetic pole.

6. The rotor assembly according to claim 5, wherein in a plane perpendicular to the central axis of the rotor core (1), an included angle formed by a connecting line of an end point of the radial outer edge of the two first extension sections (9) far away from the pole center line and the center of the rotor core (1) is a22, and an included angle formed by a connecting line of a radial outer end point of the two straight sections (7) and the center of the rotor core (1) is a21, wherein a21/a22 is 0.15-0.4.

7. The rotor assembly according to claim 2, wherein in a plane perpendicular to the central axis of the rotor core (1), an included angle formed by a connecting line of two end points of the radial outer edge of the first air slot (4) and the center of the rotor core (1) is a1, and an included angle formed by a connecting line of two radial outer end points of the straight line segment (7) and the center of the rotor core (1) is a21, wherein a1/a21 is 0.9-1.1.

8. The rotor assembly according to claim 1, wherein the radial thickness of the first air groove (4) is t1, the radial thickness of the second air groove (5) is t2, and t1/t2 is 0.1-0.3.

9. A rotor assembly as claimed in any one of claims 2 to 7, wherein both ends of the mounting slot (2) are respectively provided with a third air slot (6), and the third air slots (6) circumferentially extend from the side wall to the magnetic pole center line to form a second extension section (10).

10. The rotor assembly according to claim 9, wherein in a plane perpendicular to the central axis of the rotor core (1), the included angle formed by the end point of the radial outer edge of the two second extension sections (10) close to the center line of the magnetic poles and the connecting line of the center of the rotor core (1) is a31, and the included angle formed by the end point of the radial outer edge of the two third air grooves (6) between the adjacent permanent magnetic poles and the connecting line of the end point of the radial outer edge close to the center line of the alternate poles and the center of the rotor core (1) is a32, wherein a31/a32 is 0.8-1.

11. The rotor assembly according to claim 9, wherein in a plane perpendicular to the central axis of the rotor core (1), an included angle formed by a connecting line of end points of the radial outer edges of the two second extension sections (10) close to the magnetic pole center line and the center of the rotor core (1) is a31, and an included angle formed by a connecting line of two end points of the radial outer edges of the permanent magnets (3) close to the magnetic pole center line and the center of the rotor core (1) is am, wherein a31/am is 0.7-0.95.

12. The rotor assembly according to claim 9, wherein when the rotor core (1) is provided with the first extension sections (9), in a plane perpendicular to the central axis of the rotor core (1), an included angle formed by a connecting line between an end point of the radial outer edge of the two first extension sections (9) far away from the magnetic pole center line and the center of the rotor core (1) is a22, and an included angle formed by a connecting line between an end point of the radial outer edge of the two second extension sections (10) near the magnetic pole center line and the center of the rotor core (1) is a31, wherein a22/a31 is 0.4-0.6.

13. A rotor assembly according to any one of claims 1 to 8, wherein the permanent magnets (3) are V-shaped.

14. The rotor assembly according to any one of claims 1 to 8, wherein the number of the second air slots (5) is two, and the two second air slots (5) are symmetrical with respect to a pole center line.

15. A consequent pole machine comprising a rotor assembly and a stator assembly (11), characterised in that the rotor assembly is as claimed in any one of claims 1 to 14.

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