A brushless hybrid permanent magnet memory motor based on three excitation sources and its control method

Abstract

The present application provides a brushless hybrid permanent magnet memory motor based on three excitation sources and a control method thereof, belonging to the field of motor technology. The present application adopts the design scheme of a hybrid permanent magnet memory motor, introduces a DC excitation winding into a spoke-type permanent magnet synchronous motor, places it in a magnetic bridge fixed on the end cover, and introduces an axial additional air gap to realize a brushless structure, eliminating devices such as brushes and slip rings; arc-shaped low-coercive force permanent magnets and annular low-coercive force permanent magnets are designed, and matched with air slots distributed on the rotor core, so that the three excitation sources can be matched and combined with each other, and the motor air gap flux can be adjusted, so that the motor can achieve a wide torque range while ensuring the high efficiency and high torque density of the motor. The brushless hybrid permanent magnet memory motor based on three excitation sources provided by the present application has two modes: energy-saving mode and high-performance mode. Each operating mode includes two working states: magnetization and demagnetization, and the output voltage and speed can be adjusted over a wide range.

Description

Technical Field

[0001] The present application belongs to the field of motor technology, and specifically relates to a brushless hybrid permanent magnet memory motor based on three excitation sources and a control method thereof. Background Art

[0002] High torque density, a wide constant power speed range, and high efficiency are key design goals for permanent magnet synchronous motors. However, achieving this wide speed range requires a negative direct-axis armature current to effectively offset the non-adjustable air-gap flux generated by the rare earth permanent magnets, resulting in additional continuous winding copper losses. This shortcoming reduces the overall efficiency of the permanent magnet synchronous motor under all operating conditions and also introduces the risk of permanent magnet demagnetization.

[0003] Introducing low-coercivity permanent magnets into a permanent magnet synchronous motor (PMSM) creates a memory motor. This motor's characteristic is that demagnetization or remagnetization of the low-coercivity permanent magnets is achieved by applying charging and demagnetization current pulses, achieving adjustable air gap magnetic field and output voltage, meeting the motor's requirements for a wide speed regulation range and high efficiency. However, the operating point of low-coercivity permanent magnets is generally very low, resulting in a decrease in the PMSM's torque density.

[0004] Therefore, it is necessary to provide a brushless hybrid permanent magnet memory motor based on three excitation sources and a control method thereof to solve the problems raised in the above background technology. Summary of the Invention

[0005] The present application provides a brushless hybrid permanent magnet memory motor based on three excitation sources and a control method thereof, which realizes the adjustable air gap flux of the motor, thereby enabling the motor to achieve a wide torque range, while ensuring the high efficiency and high torque density of the motor, and can adjust the output voltage and speed over a wide range, which can effectively solve at least one technical problem in the background technology.

[0006] In order to solve the above technical problems, the technical solution of this application is:

[0007] A brushless hybrid permanent magnet memory motor based on three excitation sources, comprising:

[0008] A rotor core, wherein high-coercive force permanent magnets and low-coercive force permanent magnets are mounted on the rotor core, wherein the high-coercive force permanent magnets are embedded in the rotor core, and the low-coercive force permanent magnets are fixed at both ends of the rotor core;

[0009] a stator core, surrounding the outer side of the rotor core and spaced apart from the rotor core to form a radial main air gap, and an armature winding is mounted on the stator core;

[0010] A magnetic bridge is provided at both ends of the rotor core and is spaced apart from the low coercive force permanent magnet to form an axial additional air gap. An excitation winding is installed on the magnetic bridge, and the excitation winding is embedded in one end of the magnetic bridge close to the rotor core.

[0011] As a preferred improvement, the rotor core is a spoke structure, including an inner rim, an outer rim with a spacer ring arranged outside the inner rim, and a plurality of spokes connecting the inner rim and the outer rim. Two adjacent spokes cooperate with the outer rim and the inner rim to form an air groove.

[0012] As a preferred improvement, the low-coercive-force permanent magnet includes an annular low-coercive-force permanent magnet and an arc-shaped low-coercive-force permanent magnet. The annular low-coercive-force permanent magnet is fixed at the end of the inner rim, and the arc-shaped low-coercive-force permanent magnet is fixed at the end of the outer rim and is located on the outer ring side of the outer rim, and is arranged relative to the air slot.

[0013] As a preferred improvement, the outer rim is provided with a mounting groove along the axial direction of the rotor core, and the high coercive force permanent magnet is installed in the mounting groove, with the two ends along the axial direction of the rotor core respectively flush with the two ends of the outer rim, and the inner side along the radial direction of the rotor core faces the air slot.

[0014] As a preferred improvement, each of the air slots corresponds to two of the high coercive force permanent magnets, the two high coercive force permanent magnets are symmetrically arranged about the air slot, an annular low coercive force permanent magnet is arranged between the two high coercive force permanent magnets, and the polarities of the same end of the two high coercive force permanent magnets are opposite.

[0015] As a preferred improvement, the low-coercive-force permanent magnets located at both ends of the rotor core are symmetrically arranged with respect to the rotor core.

[0016] As a preferred improvement, the magnetic bridge is fixed to the end cover, and a mounting groove is provided at one end of the magnetic bridge close to the rotor core, the opening of the mounting groove faces the rotor core, and the excitation winding is installed in the mounting groove.

[0017] A control method for the brushless hybrid permanent magnet memory motor based on three excitation sources as described above comprises the following steps:

[0018] Passing a pulse current into the excitation winding to change the magnetization state of the low-coercive force permanent magnet and enter an energy-saving mode;

[0019] A continuous current is supplied to the excitation winding to change the magnetization state of the low-coercive-force permanent magnet and to participate in the formation of the air gap magnetic flux as an excitation source, thereby entering a high-performance mode.

[0020] As a preferred improvement, the brushless hybrid permanent magnet memory motor based on three excitation sources includes two working states in energy-saving mode: magnetization state and demagnetization state:

[0021] Magnetization state: the high-coercive-force permanent magnet generates main magnetic flux and leakage magnetic flux. The main magnetic flux passes through the high-coercive-force permanent magnet, the stator core, the rotor core and the radial main air gap to form the main magnetic flux magnetic circuit of the high-coercive-force permanent magnet, and the leakage magnetic flux of the high-coercive-force permanent magnet is suppressed by the low-coercive-force permanent magnet; the main magnetic flux generated by the low-coercive-force permanent magnet passes through the low-coercive-force permanent magnet, the magnetic bridge, the axial additional air gap, the rotor core, the stator core and the radial main air gap to form the main magnetic flux magnetic circuit of the low-coercive-force permanent magnet; the magnetic fluxes generated by the high-coercive-force permanent magnet and the low-coercive-force permanent magnet in the radial main air gap are in the same direction, which enhances the main magnetic flux of the motor;

[0022] Demagnetization state: the main magnetic flux of the high-coercive force permanent magnet passes through the main magnetic flux magnetic circuit of the high-coercive force permanent magnet, and the leakage magnetic flux passes through the high-coercive force permanent magnet, the rotor core, the low-coercive force permanent magnet, the magnetic bridge and the axial additional air gap to form the leakage magnetic flux magnetic circuit of the high-coercive force permanent magnet; the main magnetic flux generated by the low-coercive force permanent magnet passes through the main magnetic flux magnetic circuit of the low-coercive force permanent magnet; the magnetic fluxes generated by the high-coercive force permanent magnet and the low-coercive force permanent magnet in the radial main air gap are in opposite directions, which weakens the main magnetic flux of the motor.

[0023] As a preferred improvement, the brushless hybrid permanent magnet memory motor based on three excitation sources includes two working states: magnetization state and demagnetization state in high performance mode:

[0024] Magnetization state: the main magnetic flux of the high-coercive force permanent magnet passes through the main magnetic flux magnetic circuit of the high-coercive force permanent magnet, and the leakage magnetic flux of the high-coercive force permanent magnet is suppressed by the magnetic field generated by the low-coercive force permanent magnet and the excitation winding; the main magnetic flux generated by the low-coercive force permanent magnet passes through the main magnetic flux magnetic circuit of the low-coercive force permanent magnet; the main magnetic flux generated by the excitation winding passes through the low-coercive force permanent magnet, the magnetic bridge, the axial additional air gap, the rotor core, the stator core and the radial main air gap to form the main magnetic flux magnetic circuit of the excitation winding; the magnetic flux generated by the high-coercive force permanent magnet, the low-coercive force permanent magnet and the excitation winding in the radial main air gap has the same direction, which enhances the main magnetic flux of the motor;

[0025] Demagnetization state: The main magnetic flux of the high-coercive force permanent magnet passes through the main magnetic flux magnetic circuit of the high-coercive force permanent magnet, and the leakage magnetic flux passes through the leakage magnetic circuit of the high-coercive force permanent magnet; the main magnetic flux generated by the low-coercive force permanent magnet passes through the main magnetic flux magnetic circuit of the low-coercive force permanent magnet, and the main magnetic flux generated by the excitation winding passes through the main magnetic flux magnetic circuit of the excitation winding; the direction of the magnetic flux generated by the high-coercive force permanent magnet in the radial main air gap is opposite to the direction of the magnetic flux generated by the low-coercive force permanent magnet and the excitation winding in the radial main air gap, which weakens the main magnetic flux of the motor. The beneficial effects of this application are:

[0026] (1) This application adopts a hybrid permanent magnet memory motor design scheme, introducing a DC excitation winding into a spoke-type permanent magnet synchronous motor, placing it in a magnetic bridge fixed to the end cover, and introducing an axial additional air gap to achieve a brushless structure, thereby avoiding devices such as brushes and slip rings;

[0027] (2) Arc-shaped and annular low-coercivity permanent magnets are designed, and air slots are distributed in special positions of the rotor core. This allows the three excitation sources to be combined with each other, achieving adjustable air gap flux, thereby enabling the motor to achieve a wide torque range while ensuring high efficiency and high torque density.

[0028] (3) It has two operating modes and two working states in each mode, achieving low-speed, high-torque and high-speed performance, and can adjust the output voltage and speed over a wide range, with excellent overall performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present application. Those skilled in the art can also derive other drawings based on these drawings without inventive work, among which:

[0030] Figure 1 A diagram showing the exploded structure of a brushless hybrid permanent magnet memory motor based on three excitation sources provided by the present application from one angle;

[0031] Figure 2 A diagram showing the exploded structure of the brushless hybrid permanent magnet memory motor based on three excitation sources provided by the present application from another angle;

[0032] Figure 3 A 1 / 4 structural diagram of a brushless hybrid permanent magnet memory motor based on three excitation sources provided by the present application is shown;

[0033] Figure 4 A structural diagram showing the rotor core;

[0034] Figure 5A diagram showing the installation structure of low coercive force permanent magnets on the rotor core;

[0035] Figure 6 Schematic diagram of the magnetic circuit showing the demagnetization state in energy-saving mode;

[0036] Figure 7 Schematic diagram of the magnetic circuit showing the magnetization state in energy-saving mode;

[0037] Figure 8 Schematic diagram of the magnetic circuit showing the demagnetized state in high performance mode;

[0038] Figure 9 Schematic diagram of the magnetic circuit showing the magnetization state in high performance mode;

[0039] Figure 10 The radial main air gap magnetic flux distribution diagram showing the magnetization state in energy-saving mode;

[0040] Figure 11 The radial main air gap magnetic flux distribution diagram showing the demagnetization state in energy-saving mode;

[0041] Figure 12 The radial main air gap magnetic flux distribution diagram showing the magnetization state in high performance mode;

[0042] Figure 13 The radial main air gap magnetic flux distribution diagram showing the demagnetization state in high performance mode;

[0043] Figure 14 Linear back EMF diagram showing different working states in energy-saving mode;

[0044] Figure 15 Linear back EMF diagram showing different operating states in high performance mode;

[0045] Figure 16 A comparison chart showing the rated output torque of the brushless hybrid permanent magnet memory motor based on three excitation sources provided in this application and the traditional spoke-type permanent magnet synchronous motor. DETAILED DESCRIPTION

[0046] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0047] Please refer to Figures 1-16This embodiment provides a brushless hybrid permanent magnet memory motor based on three excitation sources, including a rotor core 10, a stator core 20 and a magnetic bridge 30. The stator core 20 surrounds the outer side of the rotor core 10 and is spaced from the rotor core 10 to form a radial main air gap. An armature winding 21 is installed on the stator core 20. When the armature winding 21 is energized, it generates a magnetic field to drive the rotor core 10 to rotate. The installation method of the armature winding 21 can adopt conventional technology in this field, which will not be elaborated in this embodiment.

[0048] The rotor core 10 has a spoke-like structure, comprising an inner rim 11, an outer rim 12 with a spacer ring positioned around the inner rim 11, and a plurality of spokes 13 connecting the inner and outer rims 11, 12. Adjacent spokes 13, along with the outer and inner rims 12, 11, form air slots 14. In this embodiment, there are four spokes 13 arranged in a circular array along the axis of the rotor core 10, corresponding to the number of air slots 14.

[0049] The rotor core 10 is mounted with low-coercive force permanent magnets 40 and high-coercive force permanent magnets 50 . The low-coercive force permanent magnets 40 are fixed at both ends of the rotor core 10 , and the high-coercive force permanent magnets 50 are embedded in the rotor core 10 .

[0050] The low-coercive-force permanent magnet 40 includes an annular low-coercive-force permanent magnet 41 and an arc-shaped low-coercive-force permanent magnet 42. The annular low-coercive-force permanent magnet 41 is fixed to the end of the inner rim 11, and the arc-shaped low-coercive-force permanent magnet 42 is fixed to the end of the outer rim 12 and is located on the outer ring side of the outer rim 12, and is arranged relative to the air slot 14.

[0051] The outer rim 12 is provided with a mounting groove extending through the axial direction of the rotor core 10. The high coercive force permanent magnet 50 is installed in the mounting groove. The two ends along the axial direction of the rotor core 10 are flush with the two ends of the outer rim 12 respectively. The inner side along the radial direction of the rotor core 10 faces the air slot 14. Each air slot 14 corresponds to two high coercive force permanent magnets 50. The two high coercive force permanent magnets 50 are symmetrically arranged about the air slot 14. An annular low coercive force permanent magnet 41 is arranged between the two high coercive force permanent magnets 50. The polarities of the same ends of the two high coercive force permanent magnets 50 are opposite.

[0052] Low-coercive-force permanent magnets 40 are installed at both ends of the rotor core 10 . The low-coercive-force permanent magnets 40 at both ends of the rotor core 10 are symmetrically arranged with respect to the rotor core 10 .

[0053] The magnetic bridge 30 is disposed at both ends of the rotor core 10 and is separated from the low-coercive-force permanent magnet 40 to form an additional axial air gap. An excitation winding 60 is mounted on the magnetic bridge 30 and embedded in one end of the magnetic bridge 30 near the rotor core 10. The additional axial air gap between the magnetic bridge 30 and the low-coercive-force permanent magnet 40 is used to implement a brushless structure.

[0054] Specifically, the magnetic bridge 30 is fixed to the end cover, and a mounting groove is provided at one end of the magnetic bridge 30 close to the rotor core 10 , with the opening of the mounting groove facing the rotor core 10 , and the excitation winding 60 is installed in the mounting groove.

[0055] The high-coercive-force permanent magnet 50 is installed tangentially, and the air slot 14 separates the leakage magnetic flux between the N pole and the S pole of the high-coercive-force permanent magnet 50, so that the magnetic flux of the same magnetic pole of the high-coercive-force permanent magnet 50 is converged into the inner rim 11 through the spokes 13, and then returns to the rotor core 10 after passing through the low-coercive-force permanent magnet 40, the magnetic bridge 30 and the axial additional air gap to form a closed loop.

[0056] This embodiment also provides a control method for a brushless hybrid permanent magnet memory motor based on three excitation sources, comprising the following steps:

[0057] Passing a pulse current into the excitation winding 60 to change the magnetization state of the low-coercive-force permanent magnet 40 and enter an energy-saving mode;

[0058] A continuous current is supplied to the excitation winding 60 to change the magnetization state of the low-coercive-force permanent magnet 40 and to participate in the formation of the radial main air gap magnetic flux as an excitation source, thereby entering a high-performance mode.

[0059] The brushless hybrid permanent magnet memory motor based on three excitation sources includes two working states: magnetization state and demagnetization state in energy-saving mode:

[0060] Magnetization state: Figure 6 As shown, the high-coercive-force permanent magnet 50 generates a main magnetic flux and a leakage magnetic flux. The main magnetic flux passes through the high-coercive-force permanent magnet 50, the stator core 20, the rotor core 10, and the radial main air gap to form the main magnetic flux magnetic path A1 of the high-coercive-force permanent magnet 50, while the leakage magnetic flux of the high-coercive-force permanent magnet 50 is suppressed by the low-coercive-force permanent magnet 40. The main magnetic flux generated by the low-coercive-force permanent magnet 40 passes through the low-coercive-force permanent magnet 40, the magnetic bridge 30, the axial additional air gap, the rotor core 10, the stator core 20, and the radial main air gap to form the main magnetic flux magnetic path A2 of the low-coercive-force permanent magnet 40. The magnetic flux generated by the high-coercive-force permanent magnet 50 and the low-coercive-force permanent magnet 40 in the radial main air gap has the same direction, which enhances the main magnetic flux of the motor.

[0061] Demagnetization state: Figure 7 As shown, the main magnetic flux of the high-coercive-force permanent magnet 50 passes through the main magnetic flux path A1 of the high-coercive-force permanent magnet 50, while the leakage magnetic flux passes through the high-coercive-force permanent magnet 50, the rotor core 10, the low-coercive-force permanent magnet 40, the magnetic bridge 30, and the axial additional air gap to form the leakage magnetic flux path A3 of the high-coercive-force permanent magnet 50. The main magnetic flux generated by the low-coercive-force permanent magnet 40 passes through the main magnetic flux path A2 of the low-coercive-force permanent magnet 40. The magnetic flux generated by the high-coercive-force permanent magnet 50 and the low-coercive-force permanent magnet 40 in the radial main air gap is in opposite directions, which weakens the main magnetic flux of the motor.

[0062] The brushless hybrid permanent magnet memory motor based on three excitation sources includes two working states: magnetization state and demagnetization state in high performance mode:

[0063] Magnetization state: Figure 8 As shown, the main magnetic flux of the high-coercive force permanent magnet 50 passes through the main magnetic flux magnetic path A1 of the high-coercive force permanent magnet 50, and the leakage magnetic flux of the high-coercive force permanent magnet 50 is suppressed by the magnetic field generated by the low-coercive force permanent magnet 40 and the excitation winding 60. The main magnetic flux generated by the low-coercive force permanent magnet 40 passes through the main magnetic flux magnetic path A2 of the low-coercive force permanent magnet 40. The main magnetic flux generated by the excitation winding 60 passes through the low-coercive force permanent magnet 40, the magnetic bridge 30, the axial additional air gap, the rotor core 10, the stator core 20 and the radial main air gap to form the main magnetic flux magnetic path A4 of the excitation winding 60. The magnetic fluxes generated by the high-coercive force permanent magnet 50, the low-coercive force permanent magnet 40 and the excitation winding 60 in the radial main air gap are in the same direction, which enhances the main magnetic flux of the motor.

[0064] Demagnetization state: Figure 9 As shown, the main magnetic flux of the high-coercive-force permanent magnet 50 passes through the main magnetic flux path A1 of the high-coercive-force permanent magnet, and the leakage magnetic flux passes through the leakage magnetic flux path A3 of the high-coercive-force permanent magnet 50. The main magnetic flux generated by the low-coercive-force permanent magnet 40 passes through the main magnetic flux path A2 of the low-coercive-force permanent magnet 40, and the main magnetic flux generated by the excitation winding 60 passes through the main magnetic flux path A4 of the excitation winding 60. The direction of the magnetic flux generated by the high-coercive-force permanent magnet 50 in the radial main air gap is opposite to the direction of the magnetic flux generated by the low-coercive-force permanent magnet 40 and the excitation winding 60 in the radial main air gap, which weakens the main magnetic flux of the motor.

[0065] The magnetic flux density analysis results of the radial main air gap (the air gap between the rotor core 10 and the stator core 20) of the brushless hybrid permanent magnet memory motor based on three excitation sources provided in this embodiment under no-load condition are as follows: Figure 10-13 As shown, Figure 10The radial main air gap magnetic flux distribution diagram showing the magnetization state in energy-saving mode; Figure 11 The radial main air gap magnetic flux distribution diagram showing the demagnetization state in energy-saving mode;

[0066] Figure 12 The radial main air gap magnetic flux distribution diagram showing the magnetization state in high performance mode; Figure 13 The radial main air gap magnetic flux distribution diagram shows the demagnetization state in high performance mode. Figure 10-13 It can be seen that the brushless hybrid permanent magnet memory motor based on three excitation sources provided in this embodiment can achieve a wide range of adjustment on the radial main air gap flux, and the motor can operate in a wide speed range.

[0067] The line back electromotive force analysis results of the brushless hybrid permanent magnet memory motor based on three excitation sources under no-load condition in different operation and working states are as follows: Figure 14-15 As shown, Figure 14 Linear back EMF diagram showing different working states in energy-saving mode; Figure 15 The back electromotive force diagram of different working states in high performance mode is shown. Figure 14 It can be seen that in energy-saving mode, after forward magnetization demagnetization and reverse magnetization remagnetization, the fundamental wave line back electromotive force is 149.5V and 102.3V respectively, and the voltage adjustment range is 68.4% to 100%. Figure 15 It can be seen that in the high-performance mode, the fundamental line back electromotive force in the full flux enhancement state and the full flux weakening state are 183.3V and 99.1V respectively, and the maximum voltage adjustment range is 54.1% to 100%.

[0068] The analysis results of the rated output torque of the brushless hybrid permanent magnet memory motor based on three excitation sources provided in this embodiment under rated conditions and different operating and working conditions are as follows: Figure 16 As shown, from Figure 16 It can be seen that under the MTPA control strategy and rated current, the output torque in high-performance mode is 9.58 Nm, which is 12.7% higher than the 8.50 Nm of the traditional spoke-type permanent magnet synchronous motor. However, the torque fluctuation of 10.56% is higher than the 7.33% of the traditional spoke-type permanent magnet synchronous motor. In energy-saving mode, the rated torques in the magnetizing and demagnetizing states are 7.73 Nm and 5.84 Nm, respectively, and the torque fluctuations are 8.48% and 6.89%, respectively.

[0069] The embodiments of the present application are described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of this application, ordinary technicians in this field can also make many forms without departing from the purpose of this application and the scope of protection of the claims, all of which are within the protection of this application.

Claims

1. A brushless hybrid permanent magnet memory motor based on three excitation sources, characterized in that: include: A rotor core, wherein high-coercive force permanent magnets and low-coercive force permanent magnets are mounted on the rotor core, wherein the high-coercive force permanent magnets are embedded in the rotor core, and the low-coercive force permanent magnets are fixed at both ends of the rotor core; a stator core, surrounding the outer side of the rotor core and spaced apart from the rotor core to form a radial main air gap, and an armature winding is mounted on the stator core; A magnetic bridge is provided at both ends of the rotor core and is spaced apart from the low coercive force permanent magnet to form an axial additional air gap. An excitation winding is mounted on the magnetic bridge and is embedded in one end of the magnetic bridge close to the rotor core. The rotor core is a spoke-type structure, comprising an inner rim, an outer rim with a spacer ring arranged outside the inner rim, and a plurality of spokes connecting the inner rim and the outer rim, wherein two adjacent spokes cooperate with the outer rim and the inner rim to form an air slot; The low-coercive-force permanent magnet includes an annular low-coercive-force permanent magnet and an arc-shaped low-coercive-force permanent magnet. The annular low-coercive-force permanent magnet is fixed to the end of the inner rim, and the arc-shaped low-coercive-force permanent magnet is fixed to the end of the outer rim and is located on the outer ring side of the outer rim and is spaced apart from the air slot. The outer rim is provided with a mounting groove extending through the axial direction of the rotor core. The high coercive force permanent magnet is mounted in the mounting groove, with both ends along the axial direction of the rotor core flush with the ends of the outer rim respectively, and the inner side along the radial direction of the rotor core faces the air slot; Each air slot corresponds to two high coercive force permanent magnets, the two high coercive force permanent magnets are symmetrically arranged about the air slot, an annular low coercive force permanent magnet is arranged between the two high coercive force permanent magnets, and the polarities of the same end of the two high coercive force permanent magnets are opposite.

2. The brushless hybrid permanent magnet memory motor based on three excitation sources according to claim 1 is characterized in that: The low coercive force permanent magnets located at two ends of the rotor core are symmetrically arranged with respect to the rotor core.

3. The brushless hybrid permanent magnet memory motor based on three excitation sources according to claim 1 is characterized in that: The magnetic bridge is fixed to the end cover. An installation slot is provided at one end of the magnetic bridge close to the rotor core. The opening of the installation slot faces the rotor core. The excitation winding is installed in the installation slot.

4. A control method for a brushless hybrid permanent magnet memory motor based on three excitation sources according to any one of claims 1 to 3, characterized in that: The steps include: Passing a pulse current into the excitation winding to change the magnetization state of the low-coercive force permanent magnet and enter an energy-saving mode; A continuous current is supplied to the excitation winding to change the magnetization state of the low-coercive-force permanent magnet and to participate in the formation of the air gap magnetic flux as an excitation source, thereby entering a high-performance mode.

5. The control method of the brushless hybrid permanent magnet memory motor based on three excitation sources according to claim 4, characterized in that: The brushless hybrid permanent magnet memory motor based on three excitation sources includes two working states: magnetization state and demagnetization state in energy-saving mode: Magnetization state: the high-coercive-force permanent magnet generates main magnetic flux and leakage magnetic flux. The main magnetic flux passes through the high-coercive-force permanent magnet, the stator core, the rotor core and the radial main air gap to form the main magnetic flux magnetic circuit of the high-coercive-force permanent magnet, and the leakage magnetic flux of the high-coercive-force permanent magnet is suppressed by the low-coercive-force permanent magnet; the main magnetic flux generated by the low-coercive-force permanent magnet passes through the low-coercive-force permanent magnet, the magnetic bridge, the axial additional air gap, the rotor core, the stator core and the radial main air gap to form the main magnetic flux magnetic circuit of the low-coercive-force permanent magnet; the magnetic fluxes generated by the high-coercive-force permanent magnet and the low-coercive-force permanent magnet in the radial main air gap are in the same direction, which enhances the main magnetic flux of the motor; Demagnetization state: the main magnetic flux of the high-coercive force permanent magnet passes through the main magnetic flux magnetic circuit of the high-coercive force permanent magnet, and the leakage magnetic flux passes through the high-coercive force permanent magnet, the rotor core, the low-coercive force permanent magnet, the magnetic bridge and the axial additional air gap to form the leakage magnetic flux magnetic circuit of the high-coercive force permanent magnet; the main magnetic flux generated by the low-coercive force permanent magnet passes through the main magnetic flux magnetic circuit of the low-coercive force permanent magnet; the magnetic fluxes generated by the high-coercive force permanent magnet and the low-coercive force permanent magnet in the radial main air gap are in opposite directions, which weakens the main magnetic flux of the motor.

6. The control method of the brushless hybrid permanent magnet memory motor based on three excitation sources according to claim 4, characterized in that: The brushless hybrid permanent magnet memory motor based on three excitation sources includes two working states: magnetization state and demagnetization state in high performance mode: Magnetization state: the main magnetic flux of the high-coercive force permanent magnet passes through the main magnetic flux magnetic circuit of the high-coercive force permanent magnet, and the leakage magnetic flux of the high-coercive force permanent magnet is suppressed by the magnetic field generated by the low-coercive force permanent magnet and the excitation winding; the main magnetic flux generated by the low-coercive force permanent magnet passes through the main magnetic flux magnetic circuit of the low-coercive force permanent magnet; the main magnetic flux generated by the excitation winding passes through the low-coercive force permanent magnet, the magnetic bridge, the axial additional air gap, the rotor core, the stator core and the radial main air gap to form the main magnetic flux magnetic circuit of the excitation winding; the magnetic flux generated by the high-coercive force permanent magnet, the low-coercive force permanent magnet and the excitation winding in the radial main air gap has the same direction, which enhances the main magnetic flux of the motor; Demagnetization state: the main magnetic flux of the high-coercive force permanent magnet passes through the main magnetic flux magnetic circuit of the high-coercive force permanent magnet, and the leakage magnetic flux passes through the leakage magnetic circuit of the high-coercive force permanent magnet; the main magnetic flux generated by the low-coercive force permanent magnet passes through the main magnetic flux magnetic circuit of the low-coercive force permanent magnet, and the main magnetic flux generated by the excitation winding passes through the main magnetic flux magnetic circuit of the excitation winding; the direction of the magnetic flux generated by the high-coercive force permanent magnet in the radial main air gap is opposite to the direction of the magnetic flux generated by the low-coercive force permanent magnet and the excitation winding in the radial main air gap, which weakens the main magnetic flux of the motor.

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