Permanent magnet ac servo motor

Abstract

The application provides a permanent magnet alternating current servo motor, which comprises a rotating shaft, a front end cover, a shell, a rear end cover, a stator assembly and a rotor assembly; the front end cover and the rear end cover are respectively installed on the front and rear sides of the shell, the rotating shaft is rotatably connected with the front end cover and the rear end cover through bearings, and one side of the shell is provided with a junction box; the rotor assembly is installed outside the rotating shaft, the stator assembly is installed inside the shell and outside the rotor assembly; and a fan is installed on one side of the rear end cover penetrating through the rotating shaft; through the combined magnetic circuit structure design of the stator and the rotor, the application effectively solves the technical problem that the torque ripple suppression, the irreversible demagnetization resistance and the constant power weak magnetic speed regulation range of the embedded permanent magnet servo motor are mutually restricted; the stator is provided with wide and narrow alternating stator teeth matched with stepped slots, yoke auxiliary magnetic barrier slots and short-distance double-layer distributed windings, so that the stator side magnetic field harmonic can be suppressed, the air gap magnetic density waveform can be optimized, and the torque ripple can be reduced.

Description

Technical Field

[0001] This invention relates to permanent magnet AC servo motors and belongs to the field of servo drive motor technology. Background Technology

[0002] Embedded permanent magnet AC servo motors have become the mainstream execution components of high-end servo systems due to their advantages such as high power density, good mechanical strength and salient pole field weakening speed regulation capability; however, such motors have always faced technical bottlenecks in electromagnetic design, namely, the mutual constraints between torque ripple suppression, the ability of permanent magnets to resist irreversible demagnetization and the constant power field weakening speed regulation range. In existing permanent magnet AC servo motors, optimization methods such as eccentric air gap, unequal tooth width stator, or skewed pole and slot are commonly used to reduce torque ripple. However, these structures weaken the rotor salient pole effect, resulting in a decrease in the quadrature-direct axis inductance ratio, further compressing the motor's field weakening speed regulation range. To improve the permanent magnet's resistance to irreversible demagnetization, thicker magnets, high coercivity magnets, and additional magnetic isolation slots are generally chosen. This approach not only significantly increases material costs but also introduces additional air gap magnetic field harmonics, exacerbating torque ripple. To broaden the field weakening speed regulation range, the embedding depth of V-shaped magnets is increased, and the pole-to-pole magnetic slots are enlarged, which increases magnetic leakage and disrupts the air gap magnetic flux density waveform. Traditional single-point structural improvements can only achieve local optimization of a single performance characteristic and cannot break the balance between multiple performance characteristics at the root of the magnetic circuit. As a result, the overall performance of the motor is difficult to adapt to the requirements of high-end servo equipment for low torque ripple, high resistance to demagnetization, and wide speed regulation range. To solve the above technical problems, a permanent magnet AC servo motor is proposed. Summary of the Invention

[0003] In view of this, the present invention provides a permanent magnet AC servo motor to solve or alleviate the technical problems existing in the prior art, and at least provides a beneficial alternative.

[0004] The technical solution of the present invention is implemented as follows: a permanent magnet AC servo motor, including a rotating shaft, a front end cover, a housing, a rear end cover, a stator assembly, and a rotor assembly; The front cover and the rear cover are respectively installed on the front and rear sides of the housing. The rotating shaft is rotatably connected to the front cover and the rear cover respectively through bearings. A junction box is installed on one side of the housing. The rotor assembly is mounted on the outside of the shaft, and the stator assembly is mounted inside the housing and located on the outside of the rotor assembly; A fan is installed on one side of the rotating shaft that passes through the rear end cover. A fan cover is installed on the rear end cover. An encoder is installed inside the fan cover. The encoder is connected to one end of the rotating shaft. The stator assembly includes a stator core and an armature winding, and the yoke of the stator core is provided with a yoke auxiliary magnetic barrier slot. The rotor assembly includes a rotor core and a permanent magnet assembly, wherein the permanent magnet assembly includes two main permanent magnets and two L-shaped auxiliary permanent magnets.

[0005] More preferably, the inner circumferential surface of the stator core is alternately arranged with wide stator teeth and narrow stator teeth in the circumferential direction. The tooth tip arc width of the wide stator teeth is greater than that of the narrow stator teeth. The wide stator teeth correspond to the magnetic pole center region of the rotor assembly, and the narrow stator teeth correspond to the inter-pole region of the rotor assembly.

[0006] More preferably, the ratio of the tooth tip arc width of the wide stator tooth to the tooth tip arc width of the narrow stator tooth is 7:5-8:5.

[0007] More preferably, the tooth shoe ends of both the wide stator tooth and the narrow stator tooth are provided with stepped grooves. The stepped grooves are divided radially from the inside to the outside into a narrow groove section near the air gap side and a wide groove section near the tooth body side. The ratio of the groove width of the narrow groove section to the width of the wide groove section is 5:9-5:11.

[0008] More preferably, the yoke auxiliary magnetic barrier groove is located at the position corresponding to the radial center extension line of each wide stator tooth of the stator core yoke, the depth of the yoke auxiliary magnetic barrier groove is 1 / 3-1 / 2 of the radial thickness of the yoke, and the groove width is 2mm-4mm.

[0009] More preferably, the armature winding is embedded in the stator slot formed between adjacent wide stator teeth and narrow stator teeth, and the armature winding is a 5 / 6 short-pitch double-layer distributed winding.

[0010] More preferably, the outer circle of the rotor core is an eccentric arc structure, which is composed of 6 eccentric arc segments. Each eccentric arc segment corresponds to a magnetic pole. The permanent magnet assembly is installed inside the eccentric arc. Two main permanent magnets are symmetrically and obliquely arranged along the center line of the magnetic pole to form a V-shaped configuration. The included angle between the two main permanent magnets is 120°-140°. Two L-shaped auxiliary permanent magnets are respectively arranged on both sides of the main permanent magnets.

[0011] In a further preferred embodiment, a crescent-shaped magnetic isolation groove is formed at the center position between the magnetic poles corresponding to the eccentric arc of the rotor core, a bottom arc-shaped magnetic isolation groove is formed on the outer side of the rotor core, and an end rectangular magnetic isolation groove is formed inside the rotor core.

[0012] More preferably, the rectangular magnetic isolation groove at the end is adjacent to the outer side of the radial side of the L-shaped auxiliary permanent magnet and extends radially through it, and the tangential side of the L-shaped auxiliary permanent magnet extends tangentially from the end of the radial side towards the magnetic poles and penetrates into the crescent-shaped magnetic isolation groove between the poles.

[0013] The embodiments of the present invention have the following advantages due to the adoption of the above technical solutions: This invention effectively solves the technical challenge of the mutual constraints among torque ripple suppression, irreversible demagnetization resistance, and constant power field weakening speed regulation range in embedded permanent magnet servo motors through a composite magnetic circuit structure design that coordinates the stator and rotor. The stator adopts a stepped slot with alternating wide and narrow stator teeth, auxiliary magnetic barrier slots in the yoke, and short-pitch double-layer distributed windings, which can suppress stator-side magnetic field harmonics, optimize the air gap magnetic flux density waveform, and reduce torque ripple. The rotor adopts a composite permanent magnet configuration with a V-shaped main permanent magnet and an L-shaped auxiliary permanent magnet, combined with an eccentric circular arc rotor outer circle and multiple partitions including an arc-shaped pole bottom, rectangular ends, and crescent-shaped inter-pole spacing. The magnetic slot structure, without significantly increasing the amount of permanent magnet material used, enhances the protection effect of permanent magnets against irreversible demagnetization, while retaining and optimizing the rotor salient pole effect, ensuring the direct-axis and quadrature axis inductance ratio, and widening the constant power field weakening speed regulation range of the motor. This invention abandons the traditional single-point improvement approach and achieves multi-performance synergistic improvement from the root of the magnetic circuit. While controlling material costs, it effectively suppresses magnetic leakage in the magnetic circuit and avoids additional magnetic field harmonics from aggravating torque pulsation. This enables the motor to simultaneously possess low torque pulsation, excellent anti-demagnetization performance, and a wide speed regulation range, better meeting the comprehensive performance requirements of high-end servo equipment for permanent magnet AC servo motors.

[0014] The above overview is for illustrative purposes only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features of the invention will become readily apparent from the accompanying drawings and the following detailed description. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a structural diagram of the present invention; Figure 2 This is a rear view structural diagram of the present invention; Figure 3 This is a structural diagram of the installation of the wind shield in this invention; Figure 4 This is a diagram showing the connection structure of the rotating shaft in this invention; Figure 5 This is a structural diagram of the stator assembly in this invention; Figure 6 This is a structural diagram of the rotor assembly in this invention; Figure 7This is a cross-sectional view of the rotor core in this invention.

[0017] Reference numerals: 11. Shaft; 12. Front end cover; 13. Housing; 14. Junction box; 15. Fan cover; 16. Encoder; 17. Fan; 18. Rear end cover; 19. Bearing; 20. Stator assembly; 21. Stator core; 22. Armature winding; 23. Auxiliary magnetic barrier slot in yoke; 30. Rotor assembly; 31. Rotor core; 32. Main permanent magnet; 33. Arc-shaped magnetic barrier slot at pole bottom; 34. Rectangular magnetic barrier slot at end; 35. Crescent-shaped magnetic barrier slot between poles; 36. L-shaped auxiliary permanent magnet. Detailed Implementation

[0018] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0019] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0020] like Figure 1-7 As shown, this embodiment of the invention provides a permanent magnet AC servo motor, which is applied to the feed servo drive scenario of CNC machine tools. As the actuating power component of the linear feed axis of the machine tool, it needs to simultaneously meet the requirements of low torque pulsation to ensure the surface finish of the machined part, high anti-demagnetization capability to adapt to long-term heavy-load cutting, and wide constant power speed regulation range to adapt to high and low speed switching cutting conditions. The permanent magnet AC servo motor is composed of a rotating shaft 11, a front end cover 12, a housing 13, a rear end cover 18, a stator assembly 20, and a rotor assembly 30. The front cover 12 and the rear cover 18 are respectively assembled at the front and rear ends of the housing 13. The front cover 12 and the rear cover 18 provide a mounting support reference for the bearing 19 and also provide closed protection at both ends of the housing 13 to prevent cutting fluid and metal dust from entering the motor in the machine tool working environment. The rotating shaft 11 is rotated with the front cover 12 and the rear cover 18 through the bearing 19. The bearing 19 bears the radial load and part of the axial load during the rotation of the rotating shaft 11, reducing the friction loss during the high-speed rotation of the rotating shaft 11 and adapting to the frequent forward and reverse rotation of the feed axis. The junction box 14 is fixedly installed on the side wall of the housing 13, and the junction box 14 serves as the armature. The winding 22 serves as a protective carrier for external electrical connections, enabling safe wiring between external drive cables and the internal windings of the motor. The junction box 14 connects to the machine tool servo drive. The rotor assembly 30 is mounted and fixed on the outside of the rotating shaft 11, transmitting electromagnetic torque to the rotating shaft 11 to output mechanical power. The rotating shaft 11 is connected to the CNC machine tool feed screw via a coupling, converting rotational power into linear feed motion of the worktable. The stator assembly 20 is assembled in the internal cavity of the housing 13, and the stator assembly 20 is arranged around the rotor assembly 30. The housing 13 provides radial positioning and external protection for the stator assembly 20, while also conducting the working heat generated by the frequent acceleration and deceleration of the motor. A fan 17 is mounted on one end of the rotating shaft 11 that passes through the rear end cover 18. The fan 17 rotates synchronously with the rotating shaft 11, generating airflow to provide forced air cooling for the rear end cover 18, the inside of the fan shroud 15, and the tail of the motor, thus addressing the heat accumulation of the motor under continuous cutting conditions. The fan shroud 15 is fixed to the outside of the rear end cover 18, providing physical protection for the fan 17 and preventing metal chips and foreign objects generated during machine tool processing from touching the rotating fan 17. It also constrains the airflow direction, improving heat dissipation efficiency. An encoder 16 is arranged inside the internal cavity of the fan shroud 15. The input end of the encoder 16 is connected to the end of the rotating shaft 11. During operation, the encoder 16 rotates synchronously with the rotating shaft 11, collecting the rotor's rotation angle and speed position signals in real time and feeding them back to the machine tool's servo driver. This enables closed-loop position and speed control of the CNC machine tool's feed axis, ensuring the table's feed positioning accuracy. The stator assembly 20 includes a stator core 21 and an armature winding 22. The stator core 21 serves as the magnetic conductor of the magnetic circuit and provides a mounting carrier for the armature winding 22. Auxiliary magnetic barrier slots 23 are formed in the yoke of the stator core 21. These slots can change the local magnetic circuit orientation of the yoke of the stator core 21, suppress magnetic harmonics in the yoke, reduce torque fluctuations caused by harmonics, and meet the requirements for smooth operation in CNC machine tool precision machining. Wide stator teeth and narrow stator teeth are alternately arranged circumferentially along the inner circumference of the stator core 21. The tooth tip arc width of the wide stator teeth is greater than that of the narrow stator teeth. The wide stator teeth correspond to the magnetic pole center region of the rotor assembly 30, and the narrow stator teeth correspond to the... The inter-pole region; the wide stator teeth match the high magnetic density region of the pole center, and the narrow stator teeth are adapted to the low magnetic density region between the poles. The two work together to initially optimize the air gap magnetic density distribution, reduce the cogging torque, and avoid the low-speed crawling phenomenon of the feed shaft caused by the cogging torque; both the wide and narrow stator teeth have stepped slots at the ends of the tooth shoes. The stepped slots are divided into a narrow slot section near the air gap side and a wide slot section near the tooth body side from the inside to the outside along the radial direction. The stepped slots can improve the magnetic permeability change problem at the 21 slot of the stator core and further reduce the cogging torque harmonics; the tooth tip arc width of the wide stator teeth and the width of the two slots of the stepped slots are 5:9, which optimizes the magnetic permeability distribution on the stator side and reduces magnetic field harmonics; The armature winding 22 is embedded in the stator slot formed by the wide stator teeth and the narrow stator teeth. The armature winding 22 adopts a 5 / 6 short-pitch double-layer distributed winding. The short-pitch distributed winding can cancel some of the subharmonics generated by the armature winding 22. Together with the unequal width stator teeth, the stepped slot, and the yoke auxiliary magnetic barrier slot 23, it forms a combination effect of multiple harmonic suppression, which synergistically reduces the overall torque pulsation of the motor and ensures the smooth feed of the worktable under the low-speed precision milling condition of the machine tool. The yoke auxiliary magnetic barrier slot 23 is opened at the yoke position of the stator core 21 corresponding to the radial center extension line of each wide stator tooth. It is aligned with the magnetic flux concentration area corresponding to the magnetic pole center and specifically diverts the distorted magnetic flux. The depth and slot width of the yoke auxiliary magnetic barrier slot 23 are set according to the design requirements of this invention to ensure the magnetic barrier suppression effect. The rotor assembly 30 includes a rotor core 31 and a permanent magnet assembly. The permanent magnet assembly consists of two main permanent magnets 32 and two L-shaped auxiliary permanent magnets 36. The main permanent magnets 32 serve as the main excitation source for the motor, establishing the main magnetic field of the rotor. The L-shaped auxiliary permanent magnets 36 help optimize the distribution of the magnetic field between poles and also provide demagnetization protection for the main permanent magnets 32, resisting the risk of demagnetization of the permanent magnets caused by the large reverse magnetic field of the armature during CNC machine tool overload cutting. The outer contour of the rotor core 31 is formed by splicing six eccentric arc segments, each eccentric arc segment corresponding to a magnetic pole. The eccentric arc structure actively changes the air gap length at various points, further smoothing the air gap. The gap magnetic flux density waveform; the permanent magnet assembly is embedded in the inner side of the eccentric circular arc of the rotor core 31. The rotor core 31 serves as both the mounting base for the permanent magnet assembly and a part of the rotor's magnetic conductive circuit; the two main permanent magnets 32 are arranged in a V-shape with the magnetic pole centerline as the reference. The included angle between the two main permanent magnets 32 is set according to the design requirements of this invention. The V-shaped configuration can effectively enhance the rotor's salient pole effect, ensure the difference in inductance between the quadrature and direct axes, provide the basic conditions for the motor's field weakening speed regulation, and meet the constant power output requirements of CNC machine tools during high-speed cutting; two L-shaped auxiliary permanent magnets 36 are respectively arranged on both sides of the main permanent magnets 32; The rotor core 31 has a crescent-shaped magnetic isolation groove 35 at the center between the magnetic poles, an arc-shaped magnetic isolation groove 33 at the bottom of the poles, and an end rectangular magnetic isolation groove 34 inside the rotor core 31. The arc-shaped magnetic isolation groove 33 at the bottom of the poles, the end rectangular magnetic isolation groove 34, and the crescent-shaped magnetic isolation groove 35 work together to block the leakage magnetic path at the edge of the permanent magnet and reduce the leakage magnetic loss inside the permanent magnet. The end rectangular magnetic isolation groove 34 is located outside the radial side of the L-shaped auxiliary permanent magnet 36 and runs radially through it, blocking the radial leakage magnetic field at the end of the main permanent magnet 32. The tangential side of the L-shaped auxiliary permanent magnet 36 extends from the end of the radial side towards the magnetic poles and continues to the crescent-shaped magnetic isolation groove 35 between the poles. The combination of the L-shaped auxiliary permanent magnet 36, the end rectangular magnetic isolation groove 34, and the crescent-shaped magnetic isolation groove 35 between the poles can resist the impact of the reverse magnetic field of the external armature and improve the permanent magnet's resistance to irreversible demagnetization. It can also correct the waveform of the magnetic field between the poles.

[0021] In operation, the present invention is as follows: During assembly, the armature winding 22 can be preferentially embedded into the stator core 21 to form the stator assembly 20, and the stator assembly 20 is pressed into the housing 13 for fixation; the main permanent magnet 32 ​​and the L-shaped auxiliary permanent magnet 36 are embedded and fixed into the rotor core 31 to obtain the rotor assembly 30, and the rotor assembly 30 is press-fitted and fixed onto the shaft 11; the bearings 19 are respectively assembled onto the front end cover 12 and the rear end cover 18, and the shaft 11 is inserted into the inner cavity of the stator assembly 20 to complete the locking and fixing of the front end cover 12, the rear end cover 18, and the housing 13; during operation... The fan 17 and encoder 16 are sequentially installed at the position where the shaft 11 extends beyond the rear end cover 18. Finally, the fan cover 15 is fixedly installed to the outside of the rear end cover 18 to complete the assembly of the whole machine. After the assembly is completed, the motor is installed and fixed on the servo mounting base of the CNC machine tool. The armature winding 22 is fed with the three-phase drive current output by the servo driver to establish the stator rotating magnetic field. The stator side magnetic field is coupled to the rotor assembly 30 through the stator core 21 and the air gap, and interacts with the rotor magnetic field established by the permanent magnet assembly, driving the rotor assembly 30 mounted on the rotating shaft 11 to rotate and output torque. The rotating shaft 11 passes through The coupling drives the lead screw to complete the table feed motion. In the low-speed feed condition of finishing, the wide stator teeth and narrow stator teeth on the stator core 21, together with the stepped slots and the auxiliary magnetic barrier slots 23 on the yoke, combined with the 5 / 6 short-pitch double-layer distributed armature windings 22, work together to suppress the air gap magnetic field harmonics, reduce the motor torque pulsation, eliminate the low-speed crawling of the table, and improve the surface quality of the workpiece. In the heavy-load rough cutting condition, the V-shaped main permanent magnets 32 on the rotor core 31 are paired with L-shaped auxiliary permanent magnets 36, combined with the bottom arc-shaped magnetic isolation slots 33 and the end rectangular magnetic isolation slots. The slot 34 and the inter-pole crescent-shaped magnetic isolation slot 35 together construct a composite magnetic circuit, which enhances the permanent magnet's resistance to irreversible demagnetization and avoids performance degradation of the permanent magnet caused by heavy load impact. In high-speed cutting conditions, the rotor retains the rotor salient pole effect to ensure the quadrature and direct axis inductance characteristics, widens the constant power field weakening speed regulation range of the motor, and realizes constant power output at high speed. Throughout the motor operation, the fan 17 at the tail of the shaft 11 rotates with the shaft 11 to dissipate heat from the motor body. The encoder 16 collects the rotation information of the shaft 11 in real time and feeds it back to the servo driver to complete the closed-loop control of the feed axis position.

[0022] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various variations or substitutions within the technical scope disclosed in the present invention, and these should all be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A permanent magnet AC servo motor, characterized in that: It includes a rotating shaft (11), a front end cover (12), a housing (13), a rear end cover (18), a stator assembly (20), and a rotor assembly (30). The front cover (12) and the rear cover (18) are respectively installed on the front and rear sides of the outer shell (13). The rotating shaft (11) is rotatably connected to the front cover (12) and the rear cover (18) respectively through the bearing (19). A junction box (14) is installed on one side of the outer shell (13). The rotor assembly (30) is mounted on the outside of the rotating shaft (11), and the stator assembly (20) is mounted inside the housing (13) and located on the outside of the rotor assembly (30); A fan (17) is installed on one side of the shaft (11) through the rear end cover (18). A fan cover (15) is installed on the rear end cover (18). An encoder (16) is installed inside the fan cover (15). The encoder (16) is connected to one end of the shaft (11). The stator assembly (20) includes a stator core (21) and an armature winding (22), and the yoke of the stator core (21) is provided with a yoke auxiliary magnetic barrier slot (23). The rotor assembly (30) includes a rotor core (31) and a permanent magnet assembly, which includes two main permanent magnets (32) and two L-shaped auxiliary permanent magnets (36).

2. The permanent magnet AC servo motor according to claim 1, characterized in that: The inner circumferential surface of the stator core (21) is alternately arranged with wide stator teeth and narrow stator teeth in the circumferential direction. The tooth tip arc width of the wide stator teeth is greater than that of the narrow stator teeth. The wide stator teeth correspond to the magnetic pole center region of the rotor assembly (30), and the narrow stator teeth correspond to the inter-pole region of the rotor assembly (30).

3. The permanent magnet AC servo motor according to claim 2, characterized in that: The ratio of the arc width at the top of the wide stator tooth to the arc width at the top of the narrow stator tooth is 7:5-8:

5.

4. The permanent magnet AC servo motor according to claim 2, characterized in that: Both the wide stator teeth and the narrow stator teeth have stepped grooves at their tooth shoe ends. The stepped grooves are divided radially from the inside out into a narrow groove section near the air gap side and a wide groove section near the tooth body side. The ratio of the groove width of the narrow groove section to the width of the wide groove section is 5:9 to 5:

11.

5. The permanent magnet AC servo motor according to claim 2, characterized in that: The auxiliary magnetic barrier groove (23) of the yoke is located at the position corresponding to the radial center extension line of each wide stator tooth of the yoke of the stator core (21). The depth of the auxiliary magnetic barrier groove (23) of the yoke is 1 / 3-1 / 2 of the radial thickness of the yoke, and the groove width is 2mm-4mm.

6. The permanent magnet AC servo motor according to claim 2, characterized in that: The armature winding (22) is fitted into the stator slot formed between adjacent wide stator teeth and narrow stator teeth, and the armature winding (22) is a 5 / 6 short-pitch double-layer distributed winding.

7. The permanent magnet AC servo motor according to claim 1, characterized in that: The outer circle of the rotor core (31) is an eccentric arc structure. The outer circle of the rotor core (31) is composed of 6 eccentric arc segments spliced ​​together. Each eccentric arc segment corresponds to a magnetic pole. The permanent magnet assembly is installed inside the eccentric arc. The two main permanent magnets (32) are symmetrically and obliquely arranged along the center line of the magnetic pole to form a V-shaped configuration. The included angle between the two main permanent magnets (32) is 120°-140°. The two L-shaped auxiliary permanent magnets (36) are respectively arranged on both sides of the main permanent magnets (32).

8. The permanent magnet AC servo motor according to claim 7, characterized in that: The rotor core (31) has a crescent-shaped magnetic isolation groove (35) at the center position between the magnetic poles corresponding to the eccentric arc, a bottom arc-shaped magnetic isolation groove (33) on the outside of the rotor core (31), and an end rectangular magnetic isolation groove (34) inside the rotor core (31).

9. The permanent magnet AC servo motor according to claim 8, characterized in that: The rectangular magnetic isolation groove (34) at the end is adjacent to the outer side of the radial side of the L-shaped auxiliary permanent magnet (36) and extends radially through it. The tangential side of the L-shaped auxiliary permanent magnet (36) extends tangentially from the end of the radial side towards the magnetic poles and penetrates into the crescent-shaped magnetic isolation groove (35) between the poles.

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