Magnetic field offset multi-layer magnetic barrier permanent magnet synchronous motor and design method

Abstract

The invention discloses a magnetic field offset multi-layer magnetic barrier permanent magnet synchronous motor and a design method, belonging to the field of permanent magnet synchronous motors. The invention solves the problem that the reluctance torque and permanent magnet torque of the existing permanent magnet motor cannot reach the maximum value at the same time. A group of magnet slot groups penetrating along the axial direction is arranged under each pole of the rotor core of the invention. The magnet slot group includes at least two layers of magnet slots spaced apart along the radial direction of the rotor. Each magnet slot includes a magnet insertion slot and a magnetic isolation slot. The magnet insertion slot extends in a direction perpendicular to the d-axis of the rotor. The magnetic isolation slot is arranged at both ends of the magnet insertion slot and is connected thereto. The magnetic isolation slot extends obliquely toward the outer surface of the rotor. The magnet slot group is divided into two symmetrical parts by radial magnetic isolation magnetic barriers: a permanent magnet half pole and a magnetic barrier half pole. The permanent magnet is inserted into the magnet insertion slot of the permanent magnet half pole part. The magnet insertion slot of the magnetic barrier half pole part is vacant. The magnetization directions of the permanent magnets of the adjacent two poles are opposite. The magnetic field offset setting under each pole makes the permanent magnet torque lag, so as to realize the superposition of the reluctance torque and the permanent magnet torque at the amplitude.

Description

Technical Field

[0001] The invention relates to a multi-layer magnetic barrier type permanent magnet synchronous motor in which reluctance torque and permanent magnet torque reach peak values ​​at the same current angle, belonging to the field of permanent magnet synchronous motors. Background Art

[0002] Rare earth permanent magnet motors have the advantages of high torque density and high efficiency. They are widely used in new energy vehicles, aerospace, robotics and other fields. Their performance directly affects energy utilization efficiency and carbon emissions. According to statistics, the total capacity of my country's motor systems currently exceeds 400 million kilowatts, and energy consumption accounts for about 60% of the country's total electricity consumption. Improving motor efficiency can greatly save electricity consumption. However, the cost of rare earth permanent magnet materials is relatively high, and their prices have fluctuated greatly in recent years. Against this background, research on new permanent magnet motors that increase torque without increasing the use of rare earth permanent magnet materials has become a hot topic.

[0003] The electromagnetic torque of a permanent magnet motor is usually composed of reluctance torque and permanent magnet torque. In the design of traditional permanent magnet motors, the current phase angle corresponding to the reluctance torque and the permanent magnet torque amplitude differs by 45°. Therefore, when the electromagnetic torque reaches its maximum value, the reluctance torque and the permanent magnet torque cannot reach their maximum values ​​at the same time, and the motor performance is not fully utilized, resulting in a certain performance waste. Summary of the invention

[0004] In view of the problem that the reluctance torque and permanent magnet torque of the existing permanent magnet motor cannot reach the maximum value at the same time, resulting in the inability to superimpose the amplitudes of the two to increase the electromagnetic torque, the present invention provides a magnetic field offset multi-layer magnetic barrier permanent magnet synchronous motor and a design method.

[0005] The magnetic field offset multi-layer magnetic barrier permanent magnet synchronous motor of the present invention comprises a stator, a rotor and a shaft 4, wherein the rotor is fixed on the shaft 4 and is located inside the stator, and there is a radial gap between the stator and the rotor;

[0006] The rotor comprises a rotor core 3, a plurality of permanent magnets 2 and a radial magnetic field barrier 7;

[0007] A group of magnet slots penetrating in the axial direction is arranged under each pole of the rotor core 3. The magnet slot group includes at least two layers of magnet slots 1 spaced apart in the radial direction of the rotor. Each magnet slot 1 includes a magnet insertion slot and a magnetic isolation slot. The magnet insertion slot extends in a direction perpendicular to the rotor d-axis. The magnetic isolation slots are arranged at both ends of the magnet insertion slot and are connected thereto. The magnetic isolation slots extend obliquely toward the outer surface of the rotor.

[0008] The magnet slot group is divided into two symmetrical parts by the radial magnetic barrier 7, which are permanent magnet half-pole and magnetic barrier half-pole. The permanent magnet 2 is inserted into the magnet insertion slot of the permanent magnet half-pole part; the magnet insertion slot of the magnetic barrier half-pole part is vacant; the magnetization directions of the permanent magnets of adjacent two poles are opposite;

[0009] The magnetic field offset setting under each pole makes the permanent magnet torque lag, realizing the superposition of reluctance torque and permanent magnet torque at the amplitude.

[0010] Preferably, the stator includes a stator core 6 and a stator winding 5. The inner circular side of the stator core 6 is provided with stator teeth and slots, and the stator winding 5 is circumferentially distributed in the stator teeth and slots.

[0011] Preferably, the magnet slot group includes a first magnet slot 11 and a second magnet slot 12 which are arranged at intervals along the radial direction of the rotor. The first magnet slot 11 is located outside the second magnet slot 12. The first magnet slot 11 includes a first magnet insertion slot and a first magnetic isolation slot, and the second magnet slot 12 includes a second magnet insertion slot and a second magnetic isolation slot.

[0012] Preferably, the permanent magnet 2 includes a first permanent magnet 21 and a second permanent magnet 22, and the first permanent magnet 21 and the second permanent magnet 22 are respectively inserted into the two layers of magnet insertion slots of the permanent magnet half pole.

[0013] Preferably, the radial magnetic isolation barrier 7 is located at the middle position of the magnet slot group. The radial magnetic isolation barrier 7 extends along the d-axis direction of the rotor. The radial magnetic isolation barrier 7 divides the magnet slot 1 into two equal parts, and the radial magnetic isolation barrier 7 is not connected to the two parts of the magnet slot 1.

[0014] The present invention also provides another technical solution, a design method of a magnetic field offset type multi-layer magnetic barrier permanent magnet synchronous motor. This method is realized based on the magnetic field offset type multi-layer magnetic barrier permanent magnet synchronous motor, and this method includes the following steps:

[0015] S1. Establish a simplified magnetic circuit model of the permanent magnet half pole in the motor. The first permanent magnet 21 is equivalent to a series-connected first equivalent magnetomotive force F PM1 and a first permanent magnet reluctance R PM1 , the second permanent magnet 22 is equivalent to a series-connected second equivalent magnetomotive force F PM2 and a second permanent magnet reluctance R PM2 . The radial gap between the stator and the rotor is divided into two sections according to the magnetic circuit. The section close to the first permanent magnet 21 is the first air gap, and the other air gap is the second air gap. The reluctance of the first air gap is R g1 , the magnetic flux passing through the first air gap is Φ g1 , the reluctance of the second air gap is R g2 , and the magnetic flux passing through the second air gap is Φ g2 ;

[0016] S2. Perform Fourier decomposition on the magnetic density of the magnetic field offset type multi-layer magnetic barrier permanent magnet synchronous motor to obtain the relationship between the Fourier coefficients a 1 , b 1 and the electrical angle;

[0017] S3. Let a 1 =-b 1, so that the permanent magnet torque lags behind by 45°, and the ratio of the magnetic flux density amplitude is obtained The relationship with the electrical angle;

[0018] S4. Calculate the magnetic flux density amplitude h according to the magnetic circuit model 1 、h 2 The relationship between the motor structure and material parameters is used to obtain the ratio of the magnetic flux density amplitude. Relationship with motor structure and material parameters;

[0019] S5. Combining the two relational expressions in steps S3 and S4, obtain the restriction conditions between the structure and material parameters when the motor realizes the permanent magnet torque hysteresis offset of 45°.

[0020] Preferably, the specific process of step S2 is: Fourier decomposition is performed on the magnetic flux density of the magnetic field offset multi-layer magnetic barrier permanent magnet synchronous motor, and the periodic magnetic flux density B is decomposed into a linear combination of sine and cosine functions:

[0021]

[0022] where a 0 represents the average value within a period, a n , b n is the Fourier coefficient, n is the harmonic order, and θ is the electrical angle;

[0023] Fourier coefficient a of the fundamental component when n=1 1 , b 1 It can be obtained by the following formula:

[0024]

[0025] In the above formula, p is the number of pole pairs of the motor; θ 1 is the magnetic barrier mechanical angle of the first magnet slot 11, θ 2 is the magnetic barrier mechanical angle of the second magnet slot 12;

[0026] h 1 The magnetic flux density after the second air gap is obtained as follows:

[0027]

[0028] Where, R is the outer diameter of the rotor; L is the axial length;

[0029] h 2 The magnetic flux density after the first air gap is obtained as follows:

[0030]

[0031] Preferably, the specific process of step S3 is:

[0032] Let a 1 =-b 1 , combining formula (2) and formula (3) to obtain the relationship:

[0033]

[0034] Preferably, the specific process of step S4 is:

[0035] According to the magnetic circuit model, the second equivalent magnetomotive force F PM2 , the second permanent magnet reluctance R PM2 , the first equivalent magnetomotive force F PM1 , the first permanent magnet reluctance R PM1 and the first air gap reluctance R g1 Connected in series, the second air gap magnetic resistance R g2 In parallel with the first equivalent magnetomotive force F PM1 , the first permanent magnet reluctance R PM1 and the first air gap reluctance R g1 The magnetic flux through the first and second air gaps is Φ g1 and Φ g2 ;

[0036] According to Kirchhoff's laws, there is a relationship:

[0037] F PM1 =(R g1 +R PM1 )Φ g1 -R g2 Φ g2 (7)

[0038] F PM2 =R PM2 Φ g1 +(R PM2 +R g2 )Φ g2 (8)

[0039] Arranged as:

[0040]

[0041] Substitute formula (9) into formula (5), substitute formula (10) into formula (4), and obtain the following relationship:

[0042]

[0043] Where, δ is the radial air gap length; μ 0 is the vacuum permeability; μ r is the relative recoil permeability of the permanent magnet; h PM1 and b PM1 are the thickness and width of the first permanent magnet 21, hPM2 and b PM2 are the thickness and width of the second permanent magnet 22 respectively.

[0044] Preferably, the specific process of step S5 is:

[0045] Formula (6) and formula (11) are combined to obtain the limiting condition:

[0046]

[0047] When the motor parameters satisfy formula (12), the permanent magnet torque of the motor is lagging and offset by 45°, thereby achieving the superposition of the reluctance torque and the permanent magnet torque at the amplitude.

[0048] Beneficial effects of the invention: The invention proposes a new type of magnetic field offset multi-layer magnetic barrier permanent magnet synchronous motor. Different from the traditional permanent magnet synchronous motor, the magnetic poles of the magnetic field offset multi-layer magnetic barrier permanent magnet synchronous motor are asymmetrically installed in the rotor slot, and magnetic isolation magnetic barriers are arranged at the symmetric axis position of the rotor slot to maximize the purpose of magnetic field offset. The asymmetric magnetic pole structure makes the torque-angle characteristic of the permanent magnet torque lag a certain angle, and changing its structural parameters can change the lag angle.

[0049] This structure can reduce the phase difference between the reluctance torque and the permanent magnet torque and improve the electromagnetic torque. A structural parameter limiting relationship is provided so that the permanent magnet torque of the magnetic field offset multilayer magnetic barrier permanent magnet synchronous motor lags exactly 45°, so as to achieve the purpose of superposition of the reluctance torque and the permanent magnet torque at the amplitude. This relationship is based on the magnetic circuit equivalent principle. After the magnetic field is offset, the current phase difference at the amplitude of the reluctance torque and the permanent magnet torque is reduced, thereby giving full play to the motor performance and improving the electromagnetic torque of the motor without increasing the amount of permanent magnets.

[0050] At the same time, the rotor structure with multi-layer magnetic barriers can improve the magnetic resistance torque and reduce the use of rare earth permanent magnets, thereby reducing the cost of the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is a structural schematic diagram of the magnetic field offset multi-layer magnetic barrier permanent magnet synchronous motor of the present invention;

[0052] Figure 2 It is a schematic diagram of electrical angle position;

[0053] Figure 3 It is a schematic diagram of the magnetic barrier angle of the structural parameter;

[0054] Figure 4 It is a schematic diagram of magnetic density waveform;

[0055] Figure 5 It is a schematic diagram of the torque angle characteristics before the magnetic pole is biased;

[0056] Figure 6 It is a schematic diagram of the moment-angle characteristics after magnetic pole bias;

[0057] Figure 7 It is a simplified magnetic circuit model of a half-pole motor;

[0058] Figure 8 This is the equivalent magnetic circuit diagram of the simplified magnetic circuit model of the half-pole motor.

[0059] Fig. 9 It is a schematic diagram of the size and structure parameters of the permanent magnet;

[0060] Fig.10 This is a schematic diagram of the magnetic flux waveform of the motor after offset. DETAILED DESCRIPTION

[0061] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0062] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0063] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0064] Specific implementation method 1: The following is combined Figures 1 to 10 This embodiment is described. The magnetic field offset multi-layer magnetic barrier permanent magnet synchronous motor described in this embodiment includes a stator, a rotor and a shaft 4. The rotor is fixed on the shaft 4 and is located inside the stator. There is a radial gap between the stator and the rotor.

[0065] The rotor comprises a rotor core 3, a plurality of permanent magnets 2 and a radial magnetic field barrier 7;

[0066] A group of magnet slots penetrating in the axial direction is arranged under each pole of the rotor core 3. The magnet slot group includes at least two layers of magnet slots 1 spaced apart in the radial direction of the rotor. Each magnet slot 1 includes a magnet insertion slot and a magnetic isolation slot. The magnet insertion slot extends in a direction perpendicular to the rotor d-axis. The magnetic isolation slots are arranged at both ends of the magnet insertion slot and are connected thereto. The magnetic isolation slots extend obliquely toward the outer surface of the rotor.

[0067] The magnet slot group is divided into two symmetrical parts by the radial magnetic isolation barrier 7, which are a permanent magnet half pole and a magnetic barrier half pole. The permanent magnet 2 is inserted into the magnet insertion slot of the permanent magnet half pole part; the magnet insertion slot of the magnetic barrier half pole part is empty; the magnetization directions of the permanent magnets of adjacent poles are opposite; the radial magnetic isolation barrier 7 is located in the middle position of the magnet slot group, and the radial magnetic isolation barrier 7 extends along the d-axis direction of the rotor. The radial magnetic isolation barrier 7 divides the magnet slot 1 into two parts, and the radial magnetic isolation barrier 7 is not connected to the two parts of the magnet slot 1.

[0068] The magnetic field offset setting under each pole makes the permanent magnet torque lag, so that the reluctance torque and the permanent magnet torque are superimposed at the amplitude.

[0069] The stator includes a stator core 6 and a stator winding 5. Stator slots are arranged on the inner circumference of the stator core 6. The stator winding 5 is evenly distributed in the stator slots along the circumferential direction.

[0070] Taking two layers of slots as an example, the magnet slot group includes a first magnet slot 11 and a second magnet slot 12 spaced apart along the radial direction of the rotor, the first magnet slot 11 is located outside the second magnet slot 12, the first magnet slot 11 includes a first magnet insertion slot and a first magnetic isolation slot, and the second magnet slot 12 includes a second magnet insertion slot and a second magnetic isolation slot. The straight slot at the bottom is the magnet insertion slot, and the inclined slots at both ends are magnetic isolation slots.

[0071] The permanent magnet 2 includes a first permanent magnet 21 and a second permanent magnet 22, and the first permanent magnet 21 and the second permanent magnet 22 are respectively inserted into the two layers of magnet insertion slots of the permanent magnet half pole. The present invention adopts an asymmetric installation method, which not only saves the amount of magnets, but also achieves the purpose of superimposing the permanent magnet torque and the reluctance torque at the amplitude.

[0072] Specific implementation method 2: The following is combined Figures 1 to 10 This embodiment describes a design method for a magnetic field offset type multi-layer magnetic barrier permanent magnet synchronous motor described in this embodiment. This method is implemented by the magnetic field offset type multi-layer magnetic barrier permanent magnet synchronous motor described in embodiment 1, and is characterized in that the method comprises the following steps:

[0073] S1. Establish a simplified magnetic circuit model of the permanent magnet half pole in the motor, see Figure 7 The first permanent magnet 21 is equivalent to the first equivalent magnetomotive force F in series PM1 and the first permanent magnet reluctance R PM1 The second permanent magnet 22 is equivalent to the second equivalent magnetomotive force F in series PM2 and the second permanent magnet reluctance R PM2 The radial gap between the stator and rotor is divided into two sections according to the magnetic circuit. The first section of the air gap is close to the first permanent magnet 21, and the other section of the air gap is the second section of the air gap. The magnetic resistance of the first section of the air gap is R g1 , the magnetic flux through the first air gap is Φ g1 , the magnetic resistance of the second air gap is Rg2 , the magnetic flux through the second air gap is Φ g2 ;

[0074] S2. Perform Fourier decomposition on the magnetic flux density of the magnetic field offset multi-layer magnetic barrier permanent magnet synchronous motor to obtain the Fourier coefficient a of the fundamental wave component. 1 , b 1 The relationship with the electrical angle;

[0075] S3, let a 1 =-b 1 , so that the permanent magnet torque lags behind by 45°, and the ratio of the magnetic flux density amplitude is obtained The relationship with the electrical angle;

[0076] S4. Calculate the magnetic flux density amplitude h according to the magnetic circuit model 1 、h 2 The relationship between the motor structure and material parameters is used to obtain the ratio of the magnetic flux density amplitude. Relationship with motor structure and material parameters;

[0077] S5. Combining the two relational expressions in steps S3 and S4, obtain the restriction conditions between the structure and material parameters when the motor realizes the permanent magnet torque hysteresis offset of 45°.

[0078] The specific process of step S2 is: Fourier decomposition is performed on the magnetic flux density of the magnetic field offset multi-layer magnetic barrier permanent magnet synchronous motor, and the periodic magnetic flux density B is decomposed into a linear combination of sine and cosine functions:

[0079]

[0080] where a 0 represents the average value within a period, a n , b n is the Fourier coefficient, n is the harmonic order, and θ is the electrical angle;

[0081] Fourier coefficient a of the fundamental component when n=1 1 , b 1 It can be obtained by the following formula:

[0082]

[0083] In the above formula, p is the number of pole pairs of the motor; θ 1 is the magnetic barrier mechanical angle of the first magnet slot 11, θ 2 is the magnetic barrier mechanical angle of the second magnet slot 12;

[0084] h 1 The magnetic flux density after the second air gap is obtained as follows:

[0085]

[0086] Where R is the outer diameter of the rotor; L is the axial length

[0087] h 2 The magnetic flux density after the first air gap is obtained as follows:

[0088]

[0089] The specific process of step S3 is:

[0090] Let a 1 =-b 1 , combining formula (2) and formula (3) to obtain the relationship:

[0091]

[0092] The specific process of step S4 is:

[0093] According to the magnetic circuit model, the second equivalent magnetomotive force F PM2 , the second permanent magnet reluctance R PM2 , the first equivalent magnetomotive force F PM1 , the first permanent magnet reluctance R PM1 and the first air gap reluctance R g1 Connected in series, the second air gap magnetic resistance R g2 In parallel with the first equivalent magnetomotive force F PM1 , the first permanent magnet reluctance R PM1 and the first air gap reluctance R g1 The magnetic flux through the first and second air gaps is Φ g1 and Φ g2 ;

[0094] According to Kirchhoff's laws, there is a relationship:

[0095] F PM1 =(R g1 +R PM1 )Φ g1 -R g2 Φ g2 (7)

[0096] F PM2 =R PM2 Φ g1 +(R PM2 +R g2 )Φ g2 (8)

[0097] Arranged as:

[0098]

[0099] Substitute formula (9) into formula (5), substitute formula (10) into formula (4), and obtain the following relationship:

[0100]

[0101] Where, δ is the radial air gap length; μ 0 is the vacuum permeability; μ r is the relative recoil permeability of the permanent magnet; h PM1 and b PM1 are the thickness and width of the first permanent magnet 21, h PM2 and b PM2 are the thickness and width of the second permanent magnet 22, see Fig. 9 shown.

[0102] The specific process of step S5 is:

[0103] Formula (6) and formula (11) are combined to obtain the limiting condition:

[0104]

[0105] When the motor parameters satisfy formula (12), the permanent magnet torque of the motor is lagging and offset by 45°, thereby achieving the superposition of the reluctance torque and the permanent magnet torque at the amplitude.

[0106] The following takes the pole pair number p=4 as an example to explain the principle:

[0107] The overall structure of the motor is as follows: Figure 1 As shown, the motor electrical angle position and structural parameters are shown in Figure 2 , 3 The magnetic flux waveform of this motor is as shown in Figure 4 As shown, after Fourier decomposition, the coefficient a 1 , b 1 It is expressed as:

[0108]

[0109] The torque angle characteristics before and after the magnetic pole bias are as follows Figure 5 , 6 As shown, the permanent magnet torque leads the reluctance torque by 45°. 1 and b 1 Expression, from π / 2>θ 2 >θ 1 >0, we know that a 1 is positive, b 1 is negative. 1 =-b 1 , the permanent magnet torque can be delayed by 45°, that is,

[0110]

[0111] By a 1 =-b 1 Available,

[0112]

[0113] Since the magnetic bridge leakage, the magnetic barrier leakage and the magnetic barrier leakage are ignored, and the symmetry of the magnetic circuit of this type of motor is considered, the simplified magnetic circuit model of the half-pole motor can be obtained as follows: Figure 7 As shown, the simplified magnetic circuit model is organized as follows Figure 8 As shown, F PM1 and R PM1 are the equivalent magnetomotive force and magnetic resistance of permanent magnet 1 respectively; F PM2 and R PM2 are the equivalent magnetomotive force and magnetic resistance of permanent magnet 2 respectively; R g1 and R g2 are the magnetic resistance of the first air gap and the second air gap respectively; Φ g1 and Φ g2 are the magnetic fluxes passing through the first air gap and the second air gap respectively. According to Kirchhoff's law, we can get:

[0114] F PM1 =(R g1 +R PM1 )Φ g1 -R g2 Φ g2

[0115] F PM2 =R PM2 Φ g1 +(R PM2 +R g2 )Φ g2

[0116] Arranged available,

[0117]

[0118] Magnetic field amplitude h 1 and h 2 It can be expressed as,

[0119]

[0120] In summary,

[0121]

[0122] The following example verifies the accuracy of this design. The specific structural parameters of the magnetic field offset multi-layer magnetic barrier permanent magnet synchronous motor are shown in the following table, where R stator1 is the stator outer diameter, R stator2is the inner diameter of the stator, R is the outer diameter of the rotor, R rotor2 is the inner diameter of the rotor.

[0123] Table 1 Motor structure parameters

[0124]

[0125] When the magnetic barrier angle θ 2 =20°, substitute the following parameter relationship:

[0126]

[0127] We can get θ 1 =14.037°. At this time, the magnetic flux density waveform after the offset is as follows Fig.10 As shown in the figure, after Fourier decomposition, the offset of the offset magnetic flux fundamental wave is 45.2°, which is less than the predetermined target offset of 45°, indicating that the scheme has high accuracy. The motor structural parameters meet the restrictions of formula (12), and the fundamental wave offset of about 45° can be achieved, which can achieve the purpose of superposition of the reluctance torque and the permanent magnet torque at the amplitude.

[0128] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should therefore be understood that many modifications may be made to the exemplary embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in a manner different from that described in the original claims. It should also be understood that the features described in conjunction with a single embodiment may be used in other described embodiments.

Claims

1. Magnetic field offset multi-layer magnetic barrier permanent magnet synchronous motor, It is characterized in that It comprises a stator, a rotor and a shaft (4), wherein the rotor is fixed on the shaft (4) and is located inside the stator, and a radial gap exists between the stator and the rotor; The rotor comprises a rotor core (3), a plurality of permanent magnets (2) and a radial magnetic field barrier (7); A group of magnet slots penetrating in the axial direction is arranged under each pole of the rotor core (3), the magnet slot group comprising at least two layers of magnet slots (1) spaced apart and arranged along the radial direction of the rotor, each magnet slot (1) comprising a magnet insertion slot and a magnetic isolation slot, the magnet insertion slot extending in a direction perpendicular to the d-axis of the rotor, the magnetic isolation slots being arranged at both ends of the magnet insertion slot and communicating therewith, and the magnetic isolation slots extending obliquely towards the outer cylindrical surface of the rotor away from the d-axis direction; The magnet insertion slot is divided into two symmetrical parts by a radial magnetic barrier (7), namely a permanent magnet half pole and a magnetic barrier half pole. The permanent magnet (2) is inserted into the magnet insertion slot of the permanent magnet half pole part; the magnet insertion slot of the magnetic barrier half pole part is vacant, and the radial magnetic barrier (7) is not connected to the two parts of the magnet slot (1); the magnetization directions of the permanent magnets of the adjacent two poles are opposite; The magnetic field offset setting under each pole makes the permanent magnet torque lag, so that the reluctance torque and the permanent magnet torque are superimposed at the amplitude.

2. According to the magnetic field offset multi-layer magnetic barrier permanent magnet synchronous motor of claim 1, It is characterized in that The stator comprises a stator core (6) and a stator winding (5); stator tooth slots are arranged on the inner circumference of the stator core (6); and the stator winding (5) is evenly distributed in the stator tooth slots along the circumferential direction.

3. According to the magnetic field offset multi-layer magnetic barrier permanent magnet synchronous motor of claim 1, It is characterized in that The magnet slot group comprises a first magnet slot (11) and a second magnet slot (12) which are arranged spaced apart along the radial direction of the rotor, the first magnet slot (11) is located outside the second magnet slot (12), the first magnet slot (11) comprises a first magnet insertion slot and a first magnetic isolation slot, and the second magnet slot (12) comprises a second magnet insertion slot and a second magnetic isolation slot.

4. According to the magnetic field offset multi-layer magnetic barrier permanent magnet synchronous motor of claim 3, It is characterized in that The permanent magnet (2) comprises a first permanent magnet (21) and a second permanent magnet (22), and the first permanent magnet (21) and the second permanent magnet (22) are respectively inserted into two layers of magnet insertion slots of permanent magnet half poles.

5. The magnetic field offset multi-layer magnetic barrier permanent magnet synchronous motor according to claim 1, 3 or 4, It is characterized in that The radial magnetic isolation barrier (7) is located in the middle of the magnet slot group, extends along the d-axis direction of the rotor, divides the magnet slot (1) into two parts, and the radial magnetic isolation barrier (7) is not connected to the two parts of the magnet slot (1).

6. A design method for a magnetic field offset multi-layer magnetic barrier permanent magnet synchronous motor, the method being implemented based on the magnetic field offset multi-layer magnetic barrier permanent magnet synchronous motor according to claim 5, It is characterized in that The method comprises the following steps: S1. Establish a simplified magnetic circuit model of a permanent magnet half pole in the motor. The first permanent magnet (21) is equivalent to the first equivalent magnetomotive force F in series. PM1 and the first permanent magnet reluctance R PM1 The second permanent magnet (22) is equivalent to the second equivalent magnetomotive force F connected in series PM2 and the second permanent magnet reluctance R PM2 The radial gap between the stator and the rotor is divided into two sections according to the magnetic circuit. The first section of the air gap is close to the first permanent magnet (21), and the other section of the air gap is the second section of the air gap. The magnetic resistance of the first section of the air gap is R g1 , the magnetic flux through the first air gap is Φ g1 , the magnetic resistance of the second air gap is R g2 , the magnetic flux through the second air gap is Φ g2 ; S2. Perform Fourier decomposition on the magnetic flux density of the magnetic field offset multi-layer magnetic barrier permanent magnet synchronous motor to obtain the Fourier coefficient a of the fundamental wave component. 1 , b 1 The relationship with the electrical angle; S3, let a 1 =-b 1 , so that the permanent magnet torque lags behind by 45°, and the ratio of the magnetic flux density amplitude is obtained. 1 / h 2 The relationship with the electrical angle; S4. Calculate the magnetic flux density amplitude h according to the magnetic circuit model 1 、h 2 The relationship between the motor structure and material parameters is used to obtain the ratio of the magnetic flux density amplitude h 1 / h 2 The relationship between the motor structure and material parameters, h 1 is the magnetic flux density amplitude passing through the second air gap, h 2 is the magnetic flux amplitude passing through the first air gap; S5. Combining the two relational expressions in steps S3 and S4, obtain the restriction conditions between the structure and material parameters when the motor realizes the permanent magnet torque hysteresis offset of 45°.

7. The design method of the magnetic field offset multi-layer magnetic barrier permanent magnet synchronous motor according to claim 6, It is characterized in that The specific process of step S2 is: Fourier decomposition is performed on the magnetic flux density of the magnetic field offset multi-layer magnetic barrier permanent magnet synchronous motor, and the periodic magnetic flux density B is decomposed into a linear combination of sine and cosine functions: where a 0 represents the average value within a period, a n , b n is the Fourier coefficient, n is the harmonic order, and θ is the electrical angle; Fourier coefficient a of the fundamental component when n=1 1 , b 1 It can be obtained by the following formula: In the above formula, p is the number of pole pairs of the motor; θ 1 is the magnetic barrier mechanical angle of the first magnet slot (11), θ 2 is the magnetic barrier mechanical angle of the second magnet slot (12); h 1 The magnetic flux density after the second air gap is obtained as follows: Where, R is the outer diameter of the rotor; L is the axial length; h 2 The magnetic flux density after the first air gap is obtained as follows:

8. The design method of the magnetic field offset multi-layer magnetic barrier permanent magnet synchronous motor according to claim 7, It is characterized in that The specific process of step S3 is: Let a 1 =-b 1 , combining formula (2) and formula (3) to obtain the relationship:

9. The design method of the magnetic field offset multi-layer magnetic barrier permanent magnet synchronous motor according to claim 8, It is characterized in that The specific process of step S4 is: According to the magnetic circuit model, the second equivalent magnetomotive force F PM2 , the second permanent magnet reluctance R PM2 , the first equivalent magnetomotive force F PM1 、The first permanent magnet reluctance R PM1 and the first air gap reluctance R g1 Connected in series, the second air gap magnetic resistance R g2 In parallel with the first equivalent magnetomotive force F PM1 、The first permanent magnet reluctance R PM1 and the first air gap reluctance R g1 The magnetic flux through the first and second air gaps is Φ g1 and Φ g2 ; According to Kirchhoff's laws, there is a relationship: F PM1 =(R g1 +R PM1 )F g1 -R g2 F g2 (7) F PM2 =R PM2 F g1 +(R PM2 +R g2 )F g2 (8) Arranged as: Substitute formula (9) into formula (5), substitute formula (10) into formula (4), and obtain the following relationship: Where, δ is the radial air gap length; μ r is the relative recoil permeability of the permanent magnet; h PM1 and b PM1 are the thickness and width of the first permanent magnet (21), h PM2 and b PM2 are the thickness and width of the second permanent magnet (22) respectively.

10. The design method of the magnetic field offset multi-layer magnetic barrier permanent magnet synchronous motor according to claim 9, It is characterized in that The specific process of step S5 is: Formula (6) and formula (11) are combined to obtain the limiting condition: When the motor parameters satisfy formula (12), the permanent magnet torque of the motor is lagging and offset by 45°, thereby achieving the superposition of the reluctance torque and the permanent magnet torque at the amplitude.

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