A permanent magnet synchronous motor and a control method thereof

Abstract

The present invention provides a permanent magnet synchronous motor and a control method thereof. The present invention provides a permanent magnet disk on one side of the rotor. Permanent magnets with the same shape as the axial magnetic poles of the rotor are attached to the surface of the permanent magnet disk, and the polarity is arranged alternately. The axial magnetic poles correspond to the fan-shaped permanent magnets on the permanent magnet disk at the end of the rotor. The permanent magnet disk is a rotating component. The magnetic field of the motor can be adjusted by adjusting the relative angle difference between the permanent magnet disk and the axial magnetic poles of the rotor.

Description

Technical Field

[0001] The present invention belongs to the technical field of permanent magnet synchronous motors and relates to a permanent magnet synchronous motor and a control method thereof. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] Hybrid excitation synchronous motors combine the advantages of electrically excited synchronous motors (e.g., easy magnetic adjustment and small magnetic adjustment capacity) with the high efficiency and high torque-to-mass ratio of permanent magnet synchronous motors. They also overcome the difficulty of magnetic field regulation in permanent magnet synchronous motors, making them highly promising for widespread adoption. In recent years, hybrid excitation has gained increasing attention in energy-saving, wide-speed drive systems, and independent power generation systems, and has garnered increasing attention in the industry. Hybrid excitation permanent magnet motors have two excitation sources: a permanent magnet, which generates a largely constant magnetic flux in the air gap; and a DC excitation winding. During operation, the magnetic flux in the air gap is varied by adjusting the magnitude and direction of the current flowing in the excitation winding.

[0004] However, according to the inventor's understanding, the current hybrid excitation motor has technical disadvantages in the following aspects:

[0005] 1. Structural design is difficult. It is necessary to build a reasonable magnetic field modulation circuit inside the highly integrated permanent magnet motor and design the location of the electric excitation winding. The existing technology usually builds a large number of auxiliary magnetic circuits and magnetic isolation bridges to achieve a hybrid excitation magnetic circuit, which has high manufacturing costs and is difficult to achieve a good magnetic field modulation effect.

[0006] 2. Existing motor hybrid excitation usually uses an electric excitation winding as the magnetic source of the magnetic regulation branch. It uses high-amplitude current to adjust the magnetic flux. This has low magnetic regulation efficiency and the risk of irreversible demagnetization of the permanent magnets of the permanent magnet motor, reducing the operational reliability of the drive system.

[0007] 3. Large design volume and low power density. Due to the addition of a hybrid excitation magnetic circuit and its magnetic permeation / support mechanism, the size of the permanent magnet motor will increase. In addition, the hybrid excitation magnetic circuit is usually regulated by leakage flux, so the motor power density will decrease and be significantly lower than that of the corresponding permanent magnet motor.

[0008] 4. Weak magnetic adjustment capability, a relatively narrow operating range, and relatively poor starting capability. Existing hybrid excitation magnetic adjustment permanent magnet motors typically adjust the motor's main magnetic circuit by designing a leakage magnetic circuit and adjusting the leakage flux. However, due to the proportional relationship between the leakage magnetic circuit and the main magnetic circuit, their adjustment capability is generally relatively limited.

[0009] Therefore, it is necessary to develop a new type of hybrid excitation permanent magnet motor to address the above technical problems. Summary of the Invention

[0010] In order to solve the above problems, the present invention proposes a permanent magnet synchronous motor and a control method thereof. The present invention provides a permanent magnet disk on one side of the rotor. Permanent magnets with the same shape as the axial magnetic poles of the rotor are attached to the surface of the permanent magnet disk, and the polarity is arranged alternately. The axial magnetic poles correspond to the fan-shaped permanent magnets on the permanent magnet disk at the end of the rotor. The permanent magnet disk is a rotating component. The magnetic field of the motor can be adjusted by adjusting the relative angle difference between the permanent magnet disk and the axial magnetic poles of the rotor.

[0011] According to some embodiments, the present invention adopts the following technical solutions:

[0012] A permanent magnet synchronous motor comprises a stator, a rotor and a permanent magnet disc, wherein the rotor is built into the stator and is coaxially arranged with the stator, and the permanent magnet disc is placed on the side of one end of the rotor with an axial air gap between the permanent magnet disc and the rotor;

[0013] The stator is provided with an armature winding, and the permanent magnetic disc at the end of the rotor is provided with a sector-shaped permanent magnet;

[0014] The rotor is provided with magnetic spokes that extend to the side of the permanent magnet disc at the end of the rotor, forming axial rotor poles with alternating polarity. The rotor axial poles directly face the permanent magnets attached to the permanent magnet disc of the motor rotor. The permanent magnets attached to the permanent magnet disc have the same shape as the axial rotor poles and correspond one to one.

[0015] The rotor is provided with a permanent magnet;

[0016] The permanent magnet disk is a rotating component, and the magnetic field of the motor is regulated by adjusting the relative angle difference between the permanent magnet disk and the axial magnetic pole of the rotor.

[0017] The control method of the permanent magnet synchronous motor includes:

[0018] When the motor is starting or operating normally, the permanent magnets on the permanent magnet disk and the axial magnetic poles of the motor rotor are opposite to each other with the same polarity. The magnetic flux generated by the permanent magnets on the motor rotor and the magnetic flux generated by the permanent magnets on the permanent magnet disk enter the stator, the main magnetic flux of the motor increases, and the stator applies q-axis current to generate driving torque;

[0019] When the motor needs to perform field weakening operation, the motor stator applies q-axis drive current to adjust the polarity of the permanent magnets on the permanent magnet disk to face the axial magnetic poles of the motor rotor. More magnetic flux generated by the permanent magnets on the motor rotor is absorbed into the permanent magnet disk, and the main magnetic flux of the motor is reduced.

[0020] Alternatively, the motor magnetic field can be adjusted by applying a d-axis demagnetization current to the stator and adjusting the relative position angle between the permanent magnets on the permanent magnet disk and the axial magnetic poles of the motor rotor.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The hybrid excitation motor of the present invention uses an end permanent magnet disk as the magnetic source of the magnetic modulation branch. The main magnetic flux of the motor is adjusted by adjusting the relative position angle between the end permanent magnet disk and the axial magnetic pole of the rotor. This has high magnetic modulation efficiency and does not cause the risk of irreversible demagnetization of the permanent magnets of the permanent magnet motor, significantly improving the operational reliability of the drive system.

[0023] 2. The permanent magnet discs at the ends of the motor of this invention are very thin, resulting in a compact overall motor with high power density. The hybrid excitation magnetic circuit and its magnetic conduction / support mechanism utilize the inherent support components of the spoke-type rotor, without adding additional motor volume. Furthermore, the hybrid excitation magnetic circuit incorporates flux regulation, which increases the motor's power density, with a maximum power density exceeding that of comparable permanent magnet motors.

[0024] 3. Strong magnetic adjustment capability, relatively wide operating range and strong starting capability. The hybrid excitation magnetic adjustment permanent magnet motor of the present invention designs an end permanent magnet excitation magnetic circuit and injects this magnetic flux into the motor's main magnetic circuit. The motor magnetic circuit is adjusted according to the relative position angle between the permanent magnets on the end permanent magnet disks and the rotor's axial magnetic poles, resulting in excellent adjustment capability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0026] Figure 1 This is a schematic diagram of the overall structure of the motor of the present invention;

[0027] Figure 2 、 3 This is a schematic diagram of the three-dimensional structure of the motor rotor and the end permanent magnet disk of the present invention;

[0028] Figure 4 This is a schematic diagram of the structure of the permanent magnet disk at the end of the motor rotor of the present invention;

[0029] In the figure, 1. The first section of the rotor, 2. The second section of the rotor, 3. The permanent magnet, 4. The rib structure of the first section of the rotor, 5. The rib structure of the second section of the rotor, 6. The magnetic spokes connecting the first section of the rotor to the ribs, 7. The magnetic spokes connecting the second section of the rotor to the ribs, 8. The stator, 9. The stator armature winding, 10. The stator slots, 11. The stator teeth, 12. The permanent magnet disk at the end of the rotor, 13. The permanent magnet attached to the permanent magnet disk. DETAILED DESCRIPTION

[0030] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0031] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0032] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0033] A permanent magnet synchronous motor. The motor rotor of the present invention is divided into two sections. The two sections have identical structures and are coaxially connected. The yoke of each section of the rotor has p rib structures that are alternately distributed. The ribs of the two sections of the rotor form a certain staggered angle. The staggered angle is related to the number of poles and is 360 / 2p degrees. This arrangement makes the ribs of the two sections of the rotor present opposite polarity. The end shafts of the two sections of the rotor are designed with magnetic spokes of different radii. The magnetic spokes are directly connected to the rotor ribs, which can guide the magnetic flux of the ribs of the two sections of the rotor with different polarity to the end side of the rotor, and form axial magnetic poles with alternating magnetic polarity at the end. Permanent magnetic disks corresponding to the rotor axial magnetic poles are provided on the end side of the rotor axial magnetic poles. Permanent magnets with the same shape as the rotor axial magnetic poles are attached to the permanent magnetic disks, and the polarity is alternating.

[0034] The rotor is equipped with slots containing permanent magnets. These magnets interact with each other through a "magnetic focusing effect" to form magnetic poles. The magnetic flux generated by the rotor's permanent magnets is divided into two parts: one portion directly enters the radial stator through the radial air gap, forming the motor's main magnetic flux; the other portion travels through the rotor ribs, the rotor's magnetic spokes, and the rotor's axial magnetic poles to the rotor ends, forming axial magnetic poles. These axial magnetic poles correspond to the sector-shaped permanent magnets on the rotor's permanent magnet disks. These rotating disks are adjusted to adjust the relative angle between the permanent magnet disks and the rotor's axial magnetic poles. When the sector-shaped permanent magnets on the magnetic-adjusting side permanent magnet disk are facing the same magnetic polarity as the rotor axial magnetic poles, the magnetic flux of the sector-shaped permanent magnets on the permanent magnet disk can enter the stator through the "magnetic spokes-rotor ribs-rotor yoke", thereby increasing the magnetization of the main magnetic flux of the motor; when the magnetic-adjusting side permanent magnet disk is facing the rotor axial magnetic poles with different polarity, the magnetic flux generated by the permanent magnets on the rotor will enter the permanent magnet disk at the end along the "rotor yoke-rotor ribs-magnetic spokes", thereby reducing the main magnetic flux of the motor.

[0035] To achieve the above object, the specific solutions of the present invention are as follows:

[0036] A permanent magnet synchronous motor, such as Figure 1As shown, it includes three main components: a stator, a rotor, and an end permanent magnet disk. The rotor is built into the stator and placed coaxially with the stator. The permanent magnet disk is placed on the side of the rotor end with an axial air gap between it and the rotor. The stator is equipped with an armature winding. The permanent magnet disk at the end of the rotor is attached with a fan-shaped permanent magnet.

[0037] like Figure 2 and Figure 3 As shown in the figure, the rotor is composed of two rotor sections with the same structure. Each rotor section has p staggered rib structures and is connected to the rotor yoke. p is the number of pole pairs of the motor. The ribs of the two rotor sections are staggered by a certain angle. The degree of stagger is related to the number of poles and is 360 / 2p degrees. As a result, the ribs of the two rotor sections have opposite magnetic polarities.

[0038] The two rotor end shafts are designed with magnetic spokes of different radii. Since the magnetic spokes are connected to the ribs of the two rotors, the magnetic spokes of the two rotors have opposite magnetic polarities. The magnetic spokes of the two rotors extend to the side of the permanent magnet disc at the end of the rotor, forming axial rotor poles with alternating polarity. The rotor axial poles directly face the permanent magnets attached to the permanent magnet disc of the motor rotor. Figure 4 As shown, the shape of the permanent magnets attached to the permanent magnet disk is the same as the axial rotor poles and corresponds one to one;

[0039] The rotor is provided with permanent magnets, which generate magnetic flux on the rotor through the "magnetic focusing effect". A portion of the permanent magnets passes through the rotor yoke and directly faces the air gap between the stator and rotor, forming radial magnetic poles, and the other portion passes through the "rotor rib-rotor magnetic spokes" to reach the rotor end, forming axial magnetic poles.

[0040] The magnetic flux of the radial magnetic poles of the motor enters the stator through the radial air gap and interacts with the magnetic flux generated by the armature winding on the stator to form the main magnetic flux of the motor. The axial magnetic poles of the motor correspond to the permanent magnets on the permanent magnetic disk. When the same polarity is relative to each other, the magnetic flux of the permanent magnets on the permanent magnetic disk will enter the motor rotor and enter the motor stator along the "magnetic spokes-rotor ribs-rotor yoke", thereby increasing the main magnetic flux of the motor; when the permanent magnet disk at the end of the motor is relative to the magnetic pole of the motor shaft system with different polarity, the permanent magnets on the permanent magnetic disk absorb the magnetic flux on the rotor into the permanent magnetic disk, and the magnetic flux generated by the permanent magnets on the rotor enters more into the axial magnetic circuit, thereby reducing the main magnetic flux.

[0041] When the motor is running, the main magnetic flux and driving torque of the motor are dynamically adjusted by adjusting the relative position angle between the permanent magnets on the permanent magnet disk on the rotor's magnetic adjustment side and the rotor's axial magnetic poles, thereby achieving dynamic control of the motor's operation.

[0042] In some embodiments, the stator is made of laminated silicon steel sheets, and the stator includes stator slots, stator teeth and a stator yoke, and the armature winding is placed in the stator slots; the end permanent magnet disc is made of laminated silicon steel sheets, or can be made of pure steel in an integrated manner, and a permanent magnet is attached to the surface of the permanent magnet disc, which corresponds to and has the same shape as the axial magnetic pole of the rotor. The permanent magnet disc is a rotatable component, which is driven by a servo motor. During normal operation, the permanent magnet disc is dragged to maintain the same speed as the rotor, or when dynamic adjustment of the main magnetic circuit is required, the relative angle between the permanent magnet disc and the axial magnetic pole of the rotor is adjusted.

[0043] In some embodiments, the rotor has rotor slots, in which permanent magnets are placed. The permanent magnets are connected in series and parallel to achieve a "magnetic focusing effect" and generate magnetic poles in the radial and axial directions of the rotor.

[0044] In some embodiments, the radial magnetic poles and the axial magnetic poles face the permanent magnet disks at the ends of the stator and rotor of the motor respectively. There are radial and axial air gaps between the radial and axial magnetic poles and the stator and the permanent magnet disks. The radial main magnetic flux generated by the radial magnetic poles interacts with the magnetic field on the stator to generate torque. The axial magnetic poles correspond to the permanent magnets on the permanent magnet disk. The magnetic field distribution state of the motor is adjusted by adjusting the relative position angle between the two.

[0045] In some embodiments, the entire rotor is composed of two identical rotor sections, each of which has a staggered rib structure. The rib structure of each rotor section is connected to the magnetic spokes on the rotor end shaft. The magnetic spokes extend beyond the end of the motor's magnetic adjustment side to form axial magnetic poles, which correspond to the permanent magnets on the permanent magnet disk on the rotor side.

[0046] In some embodiments, the rotor can be constructed from laminated silicon steel sheets, connected to the magnetic spokes via fasteners or bolts. Alternatively, the rotor can be a solid rotor made of a soft magnetic composite material, integrally formed through methods such as casting. To enhance the rotor's mechanical strength, the rotor can be encapsulated with epoxy resin to ensure the mechanical reliability of the rotor's magnetic spokes.

[0047] In some embodiments, the magnetic flux generated by the permanent magnets on the rotor is divided into two parts: a radial main magnetic flux and an axial main magnetic flux. The radial and axial magnetic paths are connected in parallel. By adjusting the relative position angle between the axial magnetic poles on the axial magnetic guide spokes and the permanent magnets on the end permanent magnet disks, the magnetic flux in the axial magnetic path can be controlled, thereby adjusting the overall magnetic field distribution of the motor.

[0048] Furthermore, when the axial permanent magnet disk of the motor is opposite to the axial magnetic pole with the same polarity, the magnetic flux generated by the rotor permanent magnet enters the stator more, and the magnetic flux generated by the permanent magnets on the end permanent magnet disk will also enter the stator along the "axial air gap-rotor magnetic spokes-rotor ribs-rotor yoke", the main magnetic flux of the motor increases, and the unit current output torque is significantly improved; when the axial permanent magnet disk of the motor is opposite to the axial magnetic pole with opposite polarity, most of the magnetic flux generated by the permanent magnets on the rotor enters the axial permanent magnet disk, the magnetic flux entering the stator is reduced, and the main magnetic flux of the motor is reduced, which helps to broaden the constant power operation range of the motor.

[0049] Furthermore, the main magnetic flux of the motor can be adjusted by controlling the relative position angle between the permanent magnets on the permanent magnet disk at the end of the motor and the axial magnetic pole of the rotor, so that the motor can obtain different magnetic field distribution states and operating states.

[0050] In some embodiments, the stator armature winding can be a single-layer winding or a double-layer winding. The number of motor phases, m, is ≥ 3, and the number of pole pairs, p, is ≥ 1. In this embodiment, the example diagram shows an 8-pole motor with an interleaving degree of 360 / 2p degrees. The number of permanent magnet blocks and poles on the end permanent magnet disks is 8, the number of rotor slots is 8, the two rotor sections have a total of 8 ribs, the number of permanent magnet blocks is 16, the number of rotor poles is 8, the number of motor phases is 3, and the number of stator teeth is 48.

[0051] The control method of the above-mentioned motor is as follows: the q-axis current applied to the stator armature winding interacts with the rotor main magnetic field to generate driving torque, and the relative position angle between the permanent magnets on the permanent magnet disk at the rotor end and the axial magnetic poles of the motor rotor is adjusted to adjust the amplitude of the motor main magnetic field. Specifically, it includes:

[0052] When the motor is starting or operating normally, the permanent magnets on the permanent magnet disk at the end of the motor are opposite to the axial magnetic poles of the motor rotor with the same polarity. The magnetic flux generated by the permanent magnets on the motor rotor and the magnetic flux generated by the permanent magnets on the end permanent magnet disk enter the stator, the main magnetic flux of the motor increases, and the stator applies q-axis current to generate driving torque;

[0053] When the motor needs to perform weak magnetic operation, the motor stator can still apply the q-axis drive current to adjust the polarity of the permanent magnets on the permanent magnet disk at the end of the motor and the axial magnetic poles of the motor rotor to be relative to each other. The magnetic flux generated by the permanent magnets on the motor rotor is more absorbed into the axial permanent magnet disk at the end, and the main magnetic flux of the motor is reduced; or, the motor magnetic field can be adjusted by applying the d-axis demagnetization current on the stator and adjusting the relative position angle of the permanent magnets on the permanent magnet disk at the end of the motor and the axial magnetic poles of the motor rotor in coordination.

[0054] In other embodiments, various performances can be achieved by reasonably designing various parameters of the motor, such as air gap length, permanent magnet thickness, number of stator armature winding turns, etc., according to the rated speed, rated torque and specific performance requirements of the motor.

[0055] Although the above describes the specific embodiments of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without any creative work are still within the scope of protection of the present invention.

Claims

1. A permanent magnet synchronous motor, characterized in that: The invention comprises a stator, a rotor and a permanent magnet disk, wherein the rotor is built into the stator and is coaxially placed with the stator, and the permanent magnet disk is placed on the side of one end of the rotor, with an axial air gap between the permanent magnet disk and the rotor; The stator is provided with an armature winding, and the permanent magnetic disc at the end of the rotor is provided with a sector-shaped permanent magnet; The rotor is provided with magnetic spokes that extend to the side of the permanent magnet disc at the end of the rotor, forming axial rotor poles with alternating polarity. The rotor axial poles directly face the permanent magnets attached to the permanent magnet disc of the motor rotor. The permanent magnets attached to the permanent magnet disc have the same shape as the axial rotor poles and correspond one to one. The rotor is provided with a permanent magnet; The permanent magnet disc is a rotating component, and the magnetic field of the motor is regulated by adjusting the relative angle difference between the permanent magnet disc and the axial magnetic pole of the rotor; The rotor is composed of two rotor sections with the same structure. Each rotor section has p staggered rib structures and is connected to the rotor yoke. P is the number of pole pairs of the motor. The ribs of the two rotor sections are staggered by a certain angle. The degree of stagger is related to the number of poles and is 360 / 2p degrees. The ribs of the two rotor sections have opposite magnetic polarities. The end shafts of the two rotors of identical structure are provided with magnetic spokes of different radii. The magnetic spokes of the different rotor sections have opposite magnetic polarities. The magnetic spokes of the two rotor sections extend to the side of the permanent magnet disk at the end of the rotor to form axial rotor poles with alternating polarities. The axial rotor poles directly face the permanent magnets attached to the permanent magnet disk of the motor rotor. The permanent magnets attached to the permanent magnet disk have the same shape as the axial rotor poles and correspond one-to-one. The permanent magnets on the rotor generate magnetic flux on the rotor through the magnetic focusing effect. A part of it passes through the rotor yoke and directly faces the air gap between the stator and the rotor, forming radial magnetic poles, and the other part reaches the rotor end through the path of the rotor rib-rotor magnetic spokes, forming axial magnetic poles.

2. A permanent magnet synchronous motor according to claim 1, characterized in that: The permanent magnet is in a sector shape.

3. A permanent magnet synchronous motor according to claim 1, characterized in that: The radial magnetic pole flux enters the stator through the radial air gap and interacts with the magnetic flux generated by the armature winding on the stator to form the main magnetic flux of the motor. The axial magnetic poles of the motor correspond to the permanent magnets on the permanent magnet disk. When the same polarity is opposite to each other, the magnetic flux of the permanent magnets on the permanent magnet disk will enter the motor rotor and enter the motor stator along the path of magnetic spokes-rotor ribs-rotor yoke, thereby increasing the main magnetic flux of the motor. When the permanent magnet disk at the end of the motor faces the motor shaft magnetic poles of different polarities, the permanent magnets on the permanent magnet disk absorb the magnetic flux on the rotor into the permanent magnet disk, and more of the magnetic flux generated by the permanent magnets on the rotor enters the axial magnetic circuit, reducing the main magnetic flux.

4. A permanent magnet synchronous motor as claimed in claim 3, characterized in that: The permanent magnet disc is driven by a servo motor. During normal operation, the permanent magnet disc and the rotor maintain the same rotation speed. When dynamic adjustment of the main magnetic circuit is required, the relative angle between the permanent magnet disc and the axial magnetic pole of the rotor is adjusted.

5. A permanent magnet synchronous motor according to claim 3 or 4, characterized in that: The radial magnetic poles and axial magnetic poles face the permanent magnet disks at the ends of the stator and rotor of the motor respectively. There are radial and axial air gaps between the radial and axial magnetic poles and the stator and the permanent magnet disks. The radial main magnetic flux generated by the radial magnetic poles interacts with the magnetic field on the stator to generate torque. The axial magnetic poles correspond to the permanent magnets on the permanent magnet disk. The magnetic field distribution state of the motor is adjusted by adjusting the relative position angle between the two.

6. A permanent magnet synchronous motor according to claim 1, characterized in that: The magnetic flux generated by the permanent magnets on the rotor is divided into two parts, forming radial main magnetic flux and axial main magnetic flux. The radial and axial magnetic circuits are in parallel. By adjusting the relative position angle between the axial magnetic poles on the axial magnetic guide spokes and the permanent magnets on the end permanent magnet disk, the magnetic flux on the axial magnetic circuit is controlled, thereby adjusting the overall magnetic field distribution of the motor.

7. The control method of a permanent magnet synchronous motor according to any one of claims 1 to 6, characterized in that: include: When the motor is starting or operating normally, the permanent magnets on the permanent magnet disk and the axial magnetic poles of the motor rotor are opposite to each other with the same polarity. The magnetic flux generated by the permanent magnets on the motor rotor and the magnetic flux generated by the permanent magnets on the permanent magnet disk enter the stator, the main magnetic flux of the motor increases, and the stator applies q-axis current to generate driving torque; When the motor needs to perform field weakening operation, the motor stator applies q-axis drive current to adjust the polarity of the permanent magnets on the permanent magnet disk to face the axial magnetic poles of the motor rotor. More magnetic flux generated by the permanent magnets on the motor rotor is absorbed into the permanent magnet disk, and the main magnetic flux of the motor is reduced. Alternatively, the motor magnetic field can be adjusted by applying a d-axis demagnetization current to the stator and adjusting the relative position angle between the permanent magnets on the permanent magnet disk and the axial magnetic poles of the motor rotor.

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