CN112968550A - Rotor assembly and self-starting permanent magnet synchronous reluctance motor - Google Patents

Abstract

The application provides a rotor assembly and a self-starting permanent magnet synchronous reluctance motor. The rotor assembly comprises a rotor core (1), wherein a shaft hole (6), a slit groove (2), a q-axis squirrel cage groove (3) and permanent magnets (4) are arranged on the cross section of the rotor core (1), the q-axis squirrel cage groove (3) is arranged at two ends of the slit groove (2), the permanent magnets (4) are arranged at two ends of at least part of the slit groove (2), and the two permanent magnets (4) in the same slit groove (2) are arranged at intervals. According to the rotor subassembly of this application, can increase the utilization ratio in rotor space, when utilizing motor reluctance torque, the permanent magnet torque of increase motor reduces the motor iron loss, promotes motor and gives out power and efficiency.

Description

Rotor assembly and self-starting permanent magnet synchronous reluctance motor

Technical Field

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

Background

The self-starting permanent magnet auxiliary synchronous reluctance motor combines the advantages of an asynchronous motor on the basis of the permanent magnet auxiliary synchronous reluctance motor, realizes self-starting through asynchronous torque generated by a rotor conducting bar, and realizes constant-speed operation through permanent magnet torque and reluctance torque. Compared with an asynchronous motor, the motor can run at a constant speed, the loss of a rotor is low, and the efficiency is high; compared with an asynchronous starting permanent magnet synchronous motor, the permanent magnet synchronous motor has the advantages of less permanent magnet consumption and low motor cost.

However, the rotor of the self-starting permanent magnet auxiliary synchronous reluctance motor is simultaneously provided with the magnetic barrier layer and the magnetic conduction channel, the width of the magnetic barrier layer and the width of the magnetic conduction channel are mutually restricted, and the motor efficiency is affected no matter the width of the magnetic barrier layer or the width of the magnetic conduction channel is too small, so that the saturation degree of a rotor core is high, and the motor saturation degree is further increased by arranging the magnetic barrier layer and the permanent magnet, so that the motor iron loss is increased, and the motor efficiency is reduced.

Disclosure of Invention

Therefore, the technical problem that this application will be solved lies in providing a rotor subassembly and self-starting permanent magnet synchronous reluctance motor, can increase the utilization ratio in rotor space, when utilizing motor reluctance torque, increases the permanent magnet torque of motor, reduces motor iron loss, promotes motor and exports power and efficiency.

In order to solve the problem, the application provides a rotor assembly, including rotor core, on rotor core's cross section, be provided with shaft hole, slot, q axle squirrel cage groove and permanent magnet on the rotor core, q axle squirrel cage groove sets up the both ends at the slot, and the permanent magnet is installed at the both ends in at least partial slot, is located two permanent magnet intervals settings of same slot.

Preferably, the slit grooves are at least two layers, the radial width of the slit grooves along the d-axis direction increases progressively along the direction from the middle to the two ends, and the radial width of the magnetic conduction channel between the adjacent slit grooves along the d-axis direction increases progressively along the direction from the middle to the two ends; and/or the permanent magnet is a rare earth permanent magnet.

Preferably, the slit groove comprises a magnetic resistance section and mounting sections, the mounting sections are located at two ends of the magnetic resistance section, the mounting sections extend along the q-axis direction, the permanent magnet is mounted in the mounting sections, and the magnetizing direction of the permanent magnet is parallel to the d-axis.

Preferably, the permanent magnets are arranged in at least two layers, and the length of the permanent magnets in the q-axis direction increases in a direction radially inward of the d-axis.

Preferably, the permanent magnets are arranged in at least two layers, and the minimum distance between the permanent magnets and the d axis is decreased along the direction radially inward of the d axis.

Preferably, the q-axis cage grooves extend in the q-axis direction and are parallel with respect to the q-axis.

Preferably, the width of the magnetic conduction channel between two adjacent q-axis squirrel-cage grooves is d1, the width of the magnetic conduction channel between two slit grooves corresponding to the two q-axis squirrel-cage grooves is d2, wherein d1 is more than or equal to d 2.

Preferably, the slot grooves and the permanent magnets are both multilayer, and the number of layers of the slot grooves is greater than or equal to that of the permanent magnets.

Preferably, the slit groove comprises an arc line segment and a straight line segment, the straight line segment is positioned at two ends of the arc line segment, the curvature of the arc line segment of the slit groove decreases along the direction of the d axis in the radial direction, and the curvature of the outer arc of the slit groove positioned at the same layer is smaller than that of the inner arc.

Preferably, the rotor core is further provided with a d-axis squirrel-cage groove, and the d-axis squirrel-cage groove is located on one side, close to the d axis, of the q-axis squirrel-cage groove.

Preferably, the d-axis cage slots extend in a circumferential direction of the rotor core.

Preferably, one d-axis squirrel-cage groove is arranged under the same pole, and the d-axis squirrel-cage groove is arranged on the d axis; or at least two d-axis squirrel-cage grooves under the same pole are arranged at intervals along the circumferential direction of the rotor core.

Preferably, under the same pole, along the direction of the d axis, the radial width of the d-axis squirrel cage groove is m1, the radial width of the slit groove positioned on the d axis is m2, and the radial width between the outer circle of the shaft hole and the outer circle of the rotor core is m3, wherein (m1+ ∑ m2)/m3 is 0.3-0.5.

Preferably, the total area of the q-axis cage grooves and the d-axis cage grooves is S1, and the total area of the q-axis cage grooves, the d-axis cage grooves and the slit grooves is S2, wherein S1/S2 is 30-70%.

Preferably, on the cross section of the rotor core, an included angle formed by connecting lines between the two circumferential ends of the d-axis squirrel-cage groove and the central axis of the rotor core is alpha 1, wherein alpha 1 is more than or equal to 20 degrees and less than or equal to 60 degrees.

Preferably, the total area of the d-axis cage grooves under each pole is S3, and the maximum area of the single q-axis cage groove is S4, wherein S3 ≧ 2S 4.

Preferably, the q-axis squirrel-cage groove and the d-axis squirrel-cage groove are filled with conductive and non-magnetic materials, end rings are arranged at two ends of the rotor core, and the q-axis squirrel-cage groove and the d-axis squirrel-cage groove are in short-circuit connection through the end rings to form a squirrel-cage structure.

Preferably, the width of the shaft hole in the d-axis is less than or equal to the width in the q-axis; and/or the rotor assembly is of a two-pole structure.

According to another aspect of the present application, there is provided a self-starting permanent magnet synchronous reluctance machine comprising a stator and a rotor assembly, the rotor assembly being as described above.

Preferably, when the slot and the permanent magnet are in multiple layers and the magnetizing direction of the permanent magnet is parallel to the d axis, the minimum thickness of each layer of the permanent magnet along the magnetizing direction is h, wherein h is more than or equal to 4 sigma and less than or equal to 8.5 sigma, and sigma is the radial width of an air gap between the stator and the rotor core.

Preferably, the width of a magnetic conduction channel between two q-axis squirrel cage grooves adjacent to the q axis is d3, the tooth width of the stator is t, and d3 is larger than t.

Preferably, the minimum spacing between the q-axis cage slots and the slot slots of the same layer is h1, where 0.8 σ ≦ h1 ≦ 2 σ, σ being the radial width of the air gap between the stator and rotor core.

Preferably, the minimum spacing between the q-axis cage slots and the outer rotor circle of the rotor core is h2, where h2 > σ, σ being the radial width of the air gap between the stator and the rotor core.

Preferably, when the rotor core is provided with q-axis squirrel cage grooves, slit grooves and d-axis squirrel cage grooves, the q-axis squirrel cage grooves, the slit grooves and the d-axis squirrel cage grooves which are positioned on the same layer form a magnetic barrier layer, the minimum distance between adjacent magnetic barrier layers is h3, the minimum width of the magnetic barrier layer with smaller width along the d-axis direction in the adjacent magnetic barrier layers in the d-axis direction is h4, and h3 is more than or equal to 1.8h 4.

The application provides a rotor subassembly, including rotor core, on rotor core's cross section, last shaft hole, slot groove, the squirrel cage groove of q axle and the permanent magnet of being provided with of rotor core, q axle squirrel cage groove sets up the both ends at the slot groove, and the permanent magnet is installed at the both ends in at least partial slot groove, is located two permanent magnet intervals setting of same slot inslot. The rotor assembly arranges the permanent magnets at two ends of the slit groove, so that the rotor space can be reasonably utilized to arrange the permanent magnets, the reluctance torque of the motor is ensured, the permanent magnet torque of the motor is increased, the output and efficiency of the motor are improved, and the power factor of the motor is improved; on the other hand, the permanent magnets arranged at the two ends can also reduce the iron loss of the motor, and further improve the efficiency of the motor.

Drawings

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

FIG. 2 is a schematic structural view of a rotor assembly according to an embodiment of the present application;

FIG. 3 is a torque curve comparison of an electric machine according to an embodiment of the present application and a related art electric machine;

fig. 4 is a graph showing a comparison of iron losses of the motor according to the embodiment of the present application and a motor according to the related art.

The reference numerals are represented as:

1. a rotor core; 2. a slit groove; 3. a q-axis squirrel cage slot; 4. a permanent magnet; 5. a d-axis squirrel cage groove; 6. a shaft hole; 7. an installation section; 8. a magnetoresistive segment.

Detailed Description

Referring to fig. 1 to 4 in combination, according to an embodiment of the present application, a rotor assembly includes a rotor core 1, wherein, on a cross section of the rotor core 1, a shaft hole 6, a slit groove 2, a q-axis cage groove 3 and permanent magnets 4 are arranged on the rotor core 1, the q-axis cage groove 3 is arranged at two ends of the slit groove 2, the permanent magnets 4 are arranged at two ends of at least part of the slit groove 2, and two permanent magnets 4 in the same slit groove 2 are arranged at intervals.

Each pole of a rotor assembly of the self-starting permanent magnet synchronous reluctance motor is provided with a magnetic barrier layer formed by a plurality of layers of narrow slot grooves 2 and q-axis squirrel cage grooves 3, when a permanent magnet 4 is arranged in the middle of the magnetic barrier layer, namely on a d axis, the center of a rotor magnetic pole, namely the position of the d axis, is influenced by an axial hole 6, so that the space of a rotor core in the direction of a d main shaft is insufficient, if larger magnetic flux needs to be kept, the width of the permanent magnet 4 must be ensured, therefore, a magnetic conduction channel between adjacent magnetic barrier layers is narrowed, further, the magnetic conduction channel is supersaturated, the efficiency of the motor is reduced, if the magnetic conduction channel is not supersaturated, the width of the permanent magnet 4 is limited, the magnetic flux of the motor is reduced, and the efficiency of the motor. Therefore, the permanent magnet 4 is disposed on the d-axis, and no matter how to adjust the widths of the permanent magnet 4 and the magnetic conduction channel, the motor efficiency is reduced to a certain extent and the motor iron loss is increased due to the limitation of the radial thickness of the rotor core 1 on the d-axis.

In order to solve the above problems, the present application arranges the permanent magnets 4 located in the slot 2 at two ends of the slot 2, respectively, so that the permanent magnets 4 originally located at the d-axis are changed to be located at two ends of the slot 2, thereby avoiding the over-saturation phenomenon caused by the concentration of the magnetic flux at the d-axis, and simultaneously ensuring the magnetic flux of the whole motor, and in addition, arranges the permanent magnets 4 at two ends of the slot 2, so as to avoid the rotor core with smaller thickness in the d-axis direction, which is most affected by the shaft hole 6, so that the spaces of the rotor core at two ends of the slot 2 can be fully utilized, thereby not only ensuring that the permanent magnets 4 at two ends of the slot 2 have enough thickness, providing more magnetic fluxes, but also ensuring that the width of the magnetic conduction channel between the adjacent slots 2 is enough, and avoiding the over-saturation phenomenon, therefore, on one hand, the rotor space can be reasonably utilized to arrange the, the reluctance torque of the motor is ensured, and meanwhile, the permanent magnet torque of the motor is increased, the output and the efficiency of the motor are improved, and the power factor of the motor is improved; on the other hand, the permanent magnets 4 arranged at the two ends can also reduce the iron loss of the motor, and further improve the efficiency of the motor. In the present embodiment, the rotor assembly has a two-pole structure.

In addition, the permanent magnets 4 are arranged at the two ends of the slot 2, so that the magnetic field direction of the permanent magnets 4 can not be directly opposite to the stator demagnetization magnetic field, and the demagnetization resistance of the permanent magnets 4 can be effectively improved.

In one embodiment, the slit grooves 2 are at least two layers, the radial width of the slit grooves 2 along the d-axis direction increases progressively along the direction from the middle to the two ends, the radial width of the magnetic conduction channel between the adjacent slit grooves 2 along the d-axis direction increases progressively along the direction from the middle to the two ends, so that the width of the permanent magnet 4 along the d-axis direction can be greater than the width of the slit groove 2 on the d-axis, and meanwhile, the width of the magnetic conduction channel at the position of the permanent magnet 4 can be greater than the width of the magnetic conduction channel on the d-axis, on the basis of the increase of the thickness and the increase of the magnetic flux of the permanent magnet 4, the width of the magnetic conduction channel is also increased, so that the width of the magnetic conduction channel can still meet the magnetic conduction requirement of the permanent magnet 4 with the increased thickness, thereby avoiding the over-saturation phenomenon of the magnetic conduction channel, improving the magnetic, the motor output and efficiency are improved, and the motor power factor is improved.

In one embodiment, the permanent magnet is a rare earth permanent magnet, and the rare earth permanent magnet has the advantages of high remanence and strong demagnetization resistance, so that the demagnetization resistance of the permanent magnet 4 can be improved.

In one embodiment, the permanent magnets 4 are arranged in at least two layers, with the length of the permanent magnets 4 in the direction of the q-axis increasing in a direction radially inward of the d-axis. Taking the rotor assembly comprising four layers of permanent magnets 4 as an example, the widths of the permanent magnets 4 along the d axis in the radially inward direction are L1, L2, L3 and L4 in sequence, wherein L4 > L3 > L2 > L1.

In one embodiment, the permanent magnets 4 are arranged in at least two layers, with the minimum spacing between the permanent magnets 4 and the d-axis decreasing in a direction radially inward of the d-axis. Taking the rotor assembly comprising four layers of permanent magnets 4 as an example, the minimum spacing between the permanent magnets 4 and the d-axis is L8, L7, L6 and L5 in sequence along the radially inward direction of the d-axis, wherein L8 > L7 > L6 > L5.

Can prescribe a limit to the structure and the position of permanent magnet 4 along the radial inward direction of d through above-mentioned structure to reduce the magnetic leakage part of permanent magnet 4 self short circuit, improve the utilization ratio of permanent magnet.

The slit groove 2 and the permanent magnet 4 are both multilayer, and the number of layers of the slit groove 2 is larger than or equal to that of the permanent magnet 4, so that the reluctance torque of the motor can be better utilized, and the motor output is improved.

The slit groove 2 comprises a magnetic resistance section 8 and installation sections 7, the installation sections 7 are located at two ends of the magnetic resistance section 8, the installation sections 7 extend along the q-axis direction, the permanent magnet 4 is installed in the installation sections 7, and the magnetizing direction of the permanent magnet 4 is parallel to the d-axis.

The permanent magnets 4 are arranged at the two ends of the slit groove 2, so that the rotor space can be reasonably utilized to arrange the permanent magnets 4, the reluctance torque of the motor is ensured, the permanent magnet torque of the motor is increased, the output and the efficiency of the motor are improved, and the power factor of the motor is improved, as shown in fig. 3, a torque comparison graph of the motor and a motor in the prior art is shown; on the other hand, the permanent magnets arranged at the two ends can also reduce the iron loss of the motor, so that the efficiency of the motor is further improved, and the iron loss of the motor is compared with that of the motor in the prior art as shown in fig. 4.

As can be seen from FIG. 3, the motor torque of the present application is improved by about 10% and the iron loss is reduced by about 10% compared with the motor torque in the prior art, so that the motor performance and efficiency are both greatly improved.

In one embodiment, the q-axis cage grooves 3 extend in the q-axis direction and are parallel to the q-axis, so that the q-axis cage grooves 3 and the slit grooves 2 can be matched to form a smooth rotor magnetic conduction channel.

In one embodiment, the width of the magnetic conduction channel between two adjacent q-axis squirrel-cage grooves 3 is d1, the width of the magnetic conduction channel between two slit grooves 2 corresponding to the two q-axis squirrel-cage grooves 3 is d2, wherein d1 is greater than or equal to d2, so that sufficient width can be ensured to be reserved between the q-axis squirrel-cage grooves 3, and magnetic field saturation is avoided from occurring to influence the magnetic flux circulation of the magnetic conduction channel between adjacent magnetic barrier layers.

In one embodiment, the slit groove 2 includes an arc segment and a straight segment, the straight segment is located at two ends of the arc segment, the curvature of the arc segment of the slit groove 2 decreases in the direction radially outward along the d-axis, and the curvature of the outer arc of the slit groove 2 located at the same layer is smaller than that of the inner arc. Open in the middle of rotor core 1 has shaft hole 6, adopts such setting mode can increase the utilization ratio in rotor space, and rational arrangement slot 2 to increase rotor salient pole ratio, promote motor reluctance torque. Both ends of the slit groove 2 extend in the q-axis direction as straight line segments parallel to the q-axis, and the straight line segments are used as mounting segments 7 for mounting the permanent magnets 4. Through the limitation, the position of the permanent magnet 4 can be designed by utilizing the special shape of the slot 2 according to the characteristic that the space of the rotor core 1 close to the excircle side is large, so that the reluctance torque of the motor is ensured, the permanent magnet torque is increased, and the motor output is further improved.

The rotor core 1 is also provided with a d-axis squirrel-cage groove 5, and the d-axis squirrel-cage groove 5 is positioned on one side of the q-axis squirrel-cage groove 3 close to the d axis.

In one embodiment, the d-axis cage slots 5 extend in the circumferential direction of the rotor core 1.

In one embodiment, there is one d-axis cage groove 5 under the same pole, the d-axis cage groove 5 being arranged on the d-axis.

In one embodiment, the number of the d-axis cage grooves 5 under the same pole is at least two, and the at least two d-axis cage grooves 5 are arranged at intervals along the circumferential direction of the rotor core 1.

Under same utmost point, along d axle direction, the radial width of d axle squirrel cage groove 5 is m1, and the radial width that lies in the epaxial slot 2 of d is m2, and the radial width between the excircle of shaft hole 6 and the rotor excircle of rotor core 1 is m3, and wherein (m1+ ∑ m2)/m3 is 0.3 ~ 0.5, and the purpose is to select reasonable magnetic barrier to account for the ratio, has both guaranteed sufficient magnetic barrier width, guarantees reasonable magnetic flux passageway again, when increasing the motor salient pole ratio, prevents to appear the magnetic circuit supersaturation.

The total area of the q-axis cage grooves 3 and the d-axis cage grooves 5 is S1, and the total area of the q-axis cage grooves 3, the d-axis cage grooves 5 and the slit grooves 2 is S2, wherein S1/S2 is 30% to 70%, and preferably S1/S2 is 35% to 50%. By reasonably limiting the proportional relation between S1 and S2, the squirrel cage groove area with a certain proportion can be ensured, so that the motor has certain load starting capability.

On the cross section of the rotor core 1, an included angle formed by connecting lines between the two circumferential ends of the d-axis squirrel-cage grooves 5 and the central axis of the rotor core 1 is alpha 1, wherein alpha 1 is more than or equal to 20 degrees and less than or equal to 60 degrees, the total area of the d-axis squirrel-cage grooves 5 under each pole is S3, the maximum area of a single q-axis squirrel-cage groove 3 is S4, and S3 is more than or equal to 2S 4. By the arrangement, the d-axis squirrel cage groove 5 can form an arc-shaped magnetic barrier layer and serve as a squirrel cage groove, so that the d-axis squirrel cage groove can be used as the magnetic barrier layer to increase the reluctance torque of the motor, and can also be used as a starting squirrel cage to improve the starting performance of the motor.

The q-axis squirrel-cage groove 3 and the d-axis squirrel-cage groove 5 are filled with conductive and non-magnetic materials, preferably aluminum or aluminum alloy, the two ends of the rotor core 1 are provided with end rings, the q-axis squirrel-cage groove 3 and the d-axis squirrel-cage groove 5 are in short circuit connection through the end rings to form a squirrel-cage structure, and the end ring materials are the same as the filling materials in the filling grooves. The self-short-circuited squirrel-cage structure provides asynchronous torque in the starting stage of the motor so as to realize the self-starting of the motor. The rotor multilayer permanent magnetic barrier structure consisting of the slot 2, the squirrel cage slot and the permanent magnet 4 provides permanent magnet torque and reluctance torque for the motor so as to realize synchronous operation of the motor.

In one embodiment, the width of the shaft hole 6 on the d axis is smaller than that on the q axis, so that a flat shaft hole structure can be formed, the width of the rotor core 1 on the d axis is increased, the rotor space is increased, the arrangement of the slot 2 and the magnetic conduction channel is facilitated, and better motor performance is obtained.

In one embodiment, the shaft hole 6 is circular, elliptical, or similar to a circle formed by a combination of circular arcs and straight lines.

According to an embodiment of the present application, a self-starting permanent magnet synchronous reluctance machine includes a stator and a rotor assembly, which is the above-described rotor assembly.

When the slot 2 and the permanent magnet 4 are both multilayer, and the magnetizing direction of the permanent magnet 4 is parallel to the d axis, the minimum thickness of each layer of permanent magnet 4 along the magnetizing direction is h, wherein h is more than or equal to 4 sigma and less than or equal to 8.5 sigma, and sigma is the radial width of the air gap between the stator and the rotor core 1. Preferably, h is more than or equal to 5 sigma and less than or equal to 7 sigma, and optimally, h is more than or equal to 5.2 sigma and less than or equal to 5.4 sigma, so that the permanent magnet is ensured to have higher demagnetization resistance, and the motor performance is improved.

In one embodiment, the width of the magnetic conduction channel between two q-axis squirrel cage grooves 3 adjacent to the q axis is d3, the width of the stator tooth part is t, wherein d3 is more than t, so as to ensure that the main magnetic circuit channel is not saturated, and simultaneously, the magnetic flux effectively enters the stator tooth part to generate torque.

The minimum spacing between the q-axis cage slots 3 and the slit slots 2 of the same layer is h1, wherein 0.8 sigma is more than or equal to h1 is more than or equal to 2 sigma, and sigma is the radial width of the air gap between the stator and the rotor core 1. The purpose of setting up like this can guarantee the mechanical strength of rotor part structure on the one hand, reduces the magnetic leakage between q axle squirrel cage groove 3 and the slit groove 2, and on the other hand is smoothly connected between q axle squirrel cage groove 3 and the slit groove 2, can make the magnetic circuit passageway of rotor part smooth and easy, reduces rotor magnetic circuit magnetic resistance.

The minimum interval between the q-axis squirrel-cage groove 3 and the outer circle of the rotor core 1 is h2, wherein h2 is more than sigma, and sigma is the radial width of an air gap between the stator and the rotor core 1, so that the leakage flux of the motor can be reduced and the efficiency of the motor can be improved under the condition of ensuring the mechanical strength of the rotor.

When the rotor core 1 is provided with the q-axis squirrel cage groove 3, the slit groove 2 and the d-axis squirrel cage groove 5, the q-axis squirrel cage groove 3, the slit groove 2 and the d-axis squirrel cage groove 5 which are positioned on the same layer form a magnetic barrier layer, the minimum distance between the adjacent magnetic barrier layers is h3, the minimum width of the magnetic barrier layer with smaller width along the d-axis direction in the adjacent magnetic barrier layers in the d-axis direction is h4, and h3 is more than or equal to 1.8h 4. The arrangement can also reduce the processing difficulty of the rotor and ensure the uniformity and the unsaturation degree of the magnetic density distribution of the rotor.

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 (24)

1. The rotor assembly is characterized by comprising a rotor core (1), wherein the cross section of the rotor core (1) is provided with a shaft hole (6), a slit groove (2), a q-axis squirrel-cage groove (3) and a permanent magnet (4), the q-axis squirrel-cage groove (3) is arranged at two ends of the slit groove (2), the permanent magnet (4) is arranged at two ends of at least part of the slit groove (2), and the permanent magnet (4) is positioned at two same positions in the slit groove (2) and is arranged at intervals.

2. The rotor assembly according to claim 1, wherein the slit grooves (2) are at least two layers, the radial width of the slit grooves (2) along the d-axis direction increases along the direction from the middle to the two ends, and the radial width of the magnetic conduction channel between the adjacent slit grooves (2) along the d-axis direction increases along the direction from the middle to the two ends; and/or the permanent magnet (4) is a rare earth permanent magnet.

3. The rotor assembly according to claim 1, wherein the slot (2) comprises a reluctance section (8) and a mounting section (7), the mounting section (7) is located at both ends of the reluctance section (8), the mounting section (7) extends along a q-axis direction, the permanent magnet (4) is mounted in the mounting section (7), and a magnetizing direction of the permanent magnet (4) is parallel to a d-axis.

4. The rotor assembly according to claim 3, wherein the permanent magnets (4) are arranged in at least two layers, the permanent magnets (4) having increasing lengths in the q-axis direction in a direction radially inward of the d-axis.

5. The rotor assembly according to claim 3, wherein the permanent magnets (4) are arranged in at least two layers, the minimum spacing between the permanent magnets (4) and the d-axis decreasing in a direction radially inwards of the d-axis.

6. The rotor assembly according to claim 1, wherein the q-axis cage grooves (3) extend in a q-axis direction and are parallel with respect to the q-axis.

7. The rotor assembly according to claim 6, wherein the magnetic conduction channel width between two adjacent q-axis cage grooves (3) is d1, and the magnetic conduction channel width between two slit grooves (2) corresponding to the two q-axis cage grooves (3) is d2, wherein d1 is larger than or equal to d 2.

8. The rotor assembly according to claim 1, wherein the slot slots (2) and the permanent magnets (4) are each multi-layered, the number of layers of the slot slots (2) being greater than or equal to the number of layers of the permanent magnets (4).

9. The rotor assembly according to claim 8, wherein the slot (2) comprises an arc segment and straight segments, the straight segments are positioned at two ends of the arc segment, the curvature of the arc segment of the slot (2) is reduced along the direction of the d axis and the curvature of the outer arc of the slot (2) positioned at the same layer is smaller than that of the inner arc.

10. The rotor assembly according to claim 8, wherein a d-axis cage groove (5) is further formed in the rotor core (1), and the d-axis cage groove (5) is located on one side, close to the d axis, of the q-axis cage groove (3).

11. The rotor assembly according to claim 10, wherein the d-axis squirrel cage slots (5) extend in the circumferential direction of the rotor core (1).

12. The rotor assembly according to claim 11, wherein the d-axis cage groove (5) under the same pole is one, the d-axis cage groove (5) being provided on the d-axis; or at least two d-axis squirrel-cage grooves (5) are arranged under the same pole, and the at least two d-axis squirrel-cage grooves (5) are arranged at intervals along the circumferential direction of the rotor core (1).

13. The rotor assembly according to claim 10, wherein the radial width of the d-axis cage groove (5) along the d-axis direction under the same pole is m1, the radial width of the slit groove (2) on the d-axis is m2, and the radial width between the outer circle of the shaft hole (6) and the outer circle of the rotor core (1) is m3, wherein (m1+ ∑ m2)/m3 is 0.3-0.5.

14. The rotor assembly of claim 10, wherein the total area of the q-axis cage grooves (3) and the d-axis cage grooves (5) is S1, and the total area of the q-axis cage grooves (3), the d-axis cage grooves (5) and the slit grooves (2) is S2, wherein S1/S2 is 30-70%.

15. The rotor assembly according to claim 10, wherein in the cross section of the rotor core (1), a line connecting both circumferential ends of the d-axis cage grooves (5) and the central axis of the rotor core (1) forms an included angle α 1, wherein 20 ° α 1 is less than or equal to 60 °.

16. The rotor assembly of claim 10, wherein the total area of the d-axis cage grooves (5) under each pole is S3, and the maximum area of the single q-axis cage groove (3) is S4, wherein S3 ≧ 2S 4.

17. The rotor assembly according to claim 10, wherein the q-axis cage grooves (3) and the d-axis cage grooves (5) are filled with an electrically and magnetically non-conductive material, end rings are arranged at two ends of the rotor core (1), and the q-axis cage grooves (3) and the d-axis cage grooves (5) are in short circuit connection through the end rings to form a cage structure.

18. A rotor assembly as claimed in any one of claims 1 to 17, wherein the width of the shaft bore (6) in the d-axis is less than or equal to the width in the q-axis; and/or the rotor assembly is of a two-pole structure.

19. A self-starting permanent magnet synchronous reluctance machine comprising a stator and a rotor assembly, characterised in that the rotor assembly is as claimed in any one of claims 1 to 18.

20. Self-starting permanent magnet synchronous reluctance machine according to claim 19, wherein when said slot (2) and said permanent magnets (4) are both multilayer, the magnetizing direction of said permanent magnets (4) being parallel to the d-axis, the minimum thickness of each layer of said permanent magnets (4) along the magnetizing direction is h, where 4 σ ≦ h ≦ 8.5 σ, σ being the radial width of the air gap between said stator and said rotor core (1).

21. Self-starting permanent magnet synchronous reluctance machine according to claim 19, wherein the conducting channel width between two q-axis cage slots (3) adjacent to the q-axis is d3, the tooth width of the stator is t, where d3 > t.

22. Self-starting permanent magnet synchronous reluctance machine according to claim 19, wherein the minimum spacing between said q-axis cage slots (3) and said slot slots (2) of the same layer is h1, where 0.8 σ ≦ h1 ≦ 2 σ, σ being the radial width of the air gap between said stator and said rotor core (1).

23. Self-starting permanent magnet synchronous reluctance machine according to claim 19, wherein the minimum separation between said q-axis cage slots (3) and the outer rotor circle of said rotor core (1) is h2, where h2 > σ, σ being the radial width of the air gap between said stator and said rotor core (1).

24. The self-starting permanent magnet synchronous reluctance machine according to claim 19, wherein when said rotor core (1) is provided with q-axis cage grooves (3), slit grooves (2) and d-axis cage grooves (5), said q-axis cage grooves (3), slit grooves (2) and d-axis cage grooves (5) located at the same layer form a magnetic barrier layer, the minimum distance between adjacent said magnetic barrier layers is h3, the minimum width of the magnetic barrier layer having smaller width along d-axis direction in adjacent magnetic barrier layers in d-axis direction is h4, wherein h3 is 1.8h 4.

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