High-torque permanent magnet motor with optimal quadrature-direct axis inductance difference in full-speed domain and design method of high-torque permanent magnet motor

Abstract

The invention relates to the technical field of high-torque permanent magnet motors of electric automobiles, in particular to a high-torque permanent magnet motor with the optimal quadrature-direct axis inductance difference value in a full-speed domain and a design method of the high-torque permanent magnet motor. Eight double-layer rectangular permanent magnets with the centers on the d axis are embedded in the rotor in the circumferential direction, each double-layer rectangular permanent magnet is magnetized in the inner and outer thickness direction, and the magnetizing directions of every two adjacent double-layer rectangular permanent magnets are opposite. Eight small trapezoid magnetic barriers with the centers on the q axis are embedded in the rotor in the circumferential direction, and the two sides, in the tangential direction, of each small trapezoid magnetic barrier are each provided with a small rectangular permanent magnet which is not in contact with the small trapezoid magnetic barrier. According to the method, the relation among the quadrature-direct axis inductance / quadrature-direct axis inductance difference value, the motor torque / rotating speed range and the key size in the hybrid inductance unit is deduced, and the key parameters of the motor are accurately and rapidly determined on the basis of the full-speed domain quadrature-direct axis inductance difference value optimal principle.

Description

Technical Field

[0001] The present invention relates to the technical field of high-torque permanent magnet motors for electric vehicles, and in particular to a high-torque permanent magnet motor with optimal AC- and DC-axis inductance difference in all speed ranges and a design method thereof. Background Art

[0002] In recent years, in order to solve the energy security dilemma and alleviate environmental pollution problems, electric vehicles have rapidly risen around the world. Major automakers have entered the electric vehicle industry and launched a number of new flagship electric models. my country's electric vehicles have been ranked first in global production and sales for eight consecutive years. The continuous and rapid development of electric vehicles remains a national strategy and major demand. Electric vehicles usually have multiple operating conditions such as "frequent acceleration / deceleration, climbing, and high-speed cruising", which puts forward more stringent requirements on the power density and speed range of the core power component of electric vehicles.

[0003] The document with Chinese patent number 201910136786.2 proposes a high torque density permanent magnet assisted reluctance motor for vehicles to meet the typical working conditions such as "heavy load climbing". Compared with the traditional synchronous reluctance motor, this type of motor effectively increases the magnetic load by introducing or adding a permanent magnetic source, thereby increasing the air gap flux and output torque. Considering that rare earth permanent magnet materials are expensive and non-renewable, while reducing the amount of rare earth permanent magnets, the number of winding turns and the connection form are reasonably optimized to increase the electrical load, which can also achieve the improvement of air gap flux and increase output torque. However, the excessive electric density and the resulting excess heat put forward stringent requirements on the cooling system of the motor. The document with Chinese patent number 202410718897.5 proposes a weak magnetic control technology to weaken the permanent magnetic flux and thus widen the speed regulation range, meeting the needs of typical working conditions such as "high-speed cruising", but it will lead to problems such as reduced efficiency of the motor in the weak magnetic control area and irreversible demagnetization of the motor.

[0004] In response to the above problems, the document with Chinese patent number 202310690184.8 proposed a hybrid excitation permanent magnet motor, which achieves flexible adjustment and control of the motor air gap magnetic field by adding an additional excitation winding and adjusting the magnitude and direction of the electric excitation winding current, thereby widening the motor speed regulation range and improving the motor torque density. However, the copper loss generated by the continuous electric excitation current greatly reduces the efficiency of the motor in the high-speed weak magnetic zone, and the additional heat source increases the difficulty of motor heat dissipation.

[0005] It can be seen that automotive permanent magnet motors still have problems in wide speed regulation range and high-speed efficiency, and it is difficult to fully meet the diverse performance requirements of automotive drive motors under variable working conditions. Therefore, it is of great significance to solve the problems of permanent magnet motors' difficult air gap magnetic field adjustment, narrow speed regulation range, and low efficiency in high-speed weak magnetic field areas to meet the needs of electric vehicles in multiple operating conditions. Summary of the invention

[0006] The purpose of the present invention is to address the shortcomings of the prior art and to propose a high-torque permanent magnet motor with optimal AC-D-axis inductance difference in the full-speed range and a design method thereof. By deriving the relationship between the AC-D-axis inductance / AC-D-axis inductance difference, the motor torque / speed range, and the key dimensions in the hybrid inductance unit, based on the principle of optimal AC-D-axis inductance difference in the full-speed range, the key parameters of the motor are accurately and quickly determined to meet the diverse performance requirements of the automotive drive motor under variable working conditions.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A high-torque permanent magnet motor with optimal inductance difference between AC and DC axes in the full speed range comprises a rotating shaft, a rotor sleeved on the rotating shaft, and a stator sleeved coaxially on the outside of the rotor, wherein eight double-layer rectangular permanent magnets centered on the d-axis are embedded on the rotor along the circumferential direction, the eight double-layer rectangular permanent magnets are evenly spaced, and each double-layer rectangular permanent magnet is magnetized along the inner and outer thickness directions, and the magnetization directions of two adjacent double-layer rectangular permanent magnets are opposite;

[0009] The rotor is embedded with 8 small trapezoidal magnetic barriers centered on the q-axis along the circumferential direction, the 8 small trapezoidal magnetic barriers are arranged at intervals with 8 double-layer rectangular permanent magnets, and each small trapezoidal magnetic barrier is provided with a small rectangular permanent magnet that does not contact it on both sides along the tangential direction, and the two small rectangular permanent magnets are magnetized along the inner and outer thickness directions and the magnetization directions are opposite;

[0010] Eight large trapezoidal magnetic barriers are embedded along the circumferential direction of the outer edge of the rotor, with the center on the q axis; the eight large trapezoidal magnetic barriers are evenly spaced, and the eight large trapezoidal magnetic barriers are respectively arranged one by one with the eight small trapezoidal magnetic barriers, and each large trapezoidal magnetic barrier does not contact the small trapezoidal magnetic barrier in the radial direction;

[0011] A strip-shaped magnetic barrier which is not in contact with the double-layer rectangular permanent magnet and the small rectangular permanent magnet is arranged on both tangential sides of each double-layer rectangular permanent magnet;

[0012] The stator is provided with a plurality of armature windings along the circumferential direction, and the plurality of armature windings are evenly spaced and distributed.

[0013] Preferably, a constant inductance unit is formed between the double-layer rectangular permanent magnet and the inner surface of the rotor; a variable inductance unit is formed between the small trapezoidal magnetic barrier and the two small rectangular permanent magnets on both sides of the small trapezoidal magnetic barrier and the inner surface of the rotor; a fine-tuning inductance unit is formed between the large trapezoidal magnetic barrier and the inner surface of the rotor;

[0014] In the constant inductance unit, the height h of the double-layer rectangular permanent magnet is pm1 =2.5mm, width w pm1=14.0mm;

[0015] In the variable inductance unit, the height h of the small rectangular permanent magnet is pm2 =2.5mm, width w pm2 =4.0mm;

[0016] In the fine-tuning inductor unit, the radial equivalent diameter length w barrier =8.0mm, tangential equivalent length l barrier =9.0mm.

[0017] The present invention also provides a design method for a high-torque permanent magnet motor with an optimal inductance difference between the AC and DC axes in the full speed range, comprising the following steps:

[0018] Step 1: Determine the optimal inductance difference between the direct and alternating axes in the full speed range:

[0019] Electric vehicle motors often require multiple design requirements such as high output torque, wide speed range, and high efficiency. In theory, the priority of each performance varies greatly under different operating conditions. For example, under the "low speed and heavy load" condition, the output torque needs to be given priority; while under the "high speed and light load" condition, the speed range is the key performance. Output torque T e and maximum speed ω max The formula is:

[0020]

[0021] Where P is the number of pole pairs, ψ δ is the effective magnetic flux, L d is the d-axis inductance, L q is the q-axis inductance, N is the number of winding turns, U lim is the voltage limit, φ pm is the permanent magnet flux, S ξ (i s ) is the saliency ratio, S ξ (i s )=L q / L d , and define the inductance difference K of the direct and quadrature axes in the full speed domain ΔL =|L d -L q |, such as Figure 3 As shown;

[0022] According to formula (1), the motor inductance is closely related to the motor torque, maximum speed and other performances. In order to increase the output torque and expand the speed regulation range, it is necessary to achieve L under the "low speed and heavy load" working condition. d >L q , and increase the AC-DC axis inductance difference K ΔL+ =L d -Lq ; Achieve L in "high speed and light load" working condition d <L q , and increase the AC-DC axis inductance difference K ΔL- =L q -L d ;

[0023] Step 2: Based on the requirement of optimal difference between the AC and DC axis inductances in the full speed range, a regional comprehensive design of the hybrid inductor unit is performed;

[0024] The permanent magnet reluctance R in the constant inductance unit is calculated according to the formula pm1 , the permanent magnet reluctance R in the variable inductance unit pm2 and leakage magnetic resistance R σ (i s ), and fine-tuning the magnetic barrier reluctance R in the inductor unit b The relationship is:

[0025]

[0026] The relationship between the magnetic resistance in the three inductor units and the dimensions in the three inductor units is as follows: Figure 4 As shown. In the constant inductance unit, the height of the permanent magnet is h pm1 , with a width of w pm1 ; In the variable inductance unit, the height of the permanent magnet is h pm2 , with a width of w pm2 , the tangential length of the leakage flux bridge is w σ , radial length is l σ ; In the fine-tuning inductor unit, the radial equivalent diameter length is w barrier , the tangential equivalent length is l barrier ;

[0027] according to Figure 4 The key dimensions of the three inductor units given in Figure 6 The magnetization curve and relative permeability of the core material under different working conditions are given, and the permanent magnet reluctance R in the constant inductance unit pm1 , the permanent magnet reluctance R in the variable inductance unit pm2 and leakage magnetic resistance R σ (i s ), and fine-tuning the magnetic barrier reluctance R in the inductor unit b The expression is:

[0028]

[0029] In the formula, μ pm is the relative magnetic permeability of the permanent magnet; μ0 is the magnetic permeability of vacuum; L axial is the axis length, B σis the magnetic flux density under different currents; μ1 is the magnetic permeability of silicon steel sheets; m and k are the proportional coefficients of magnetic permeability under low speed and heavy load and high speed and light load respectively; according to Figure 5 It can be seen that w barrier =πθ a R 2 barriers / (180l barrier )-(R barrier -L4) / 2.

[0030] Preferably, based on the design principle of optimal difference between the inductance of the AC and DC axes in the full speed range, the evaluation function f is defined as max To determine the key parameters of the motor:

[0031] f max =k1K ΔL- +k2K ΔL+ (4)

[0032] In the formula, k1 and k2 are the specific gravity coefficient of high-speed working condition and the specific gravity coefficient of low-speed working condition respectively, and k1+k2=1;

[0033] In order to further determine the motor parameter values, a multi-operating condition comprehensive optimization method is adopted, in which the inductance difference is used as the optimization target for the first time, such as Figure 7 The parameter frontier is given and the motor parameters are finally determined.

[0034] By adopting the above technical solution: a variable inductance unit, a constant inductance unit and a fine-tuning inductance unit are innovatively introduced into the rotor at the same time; the constant inductance unit focuses on the d-axis magnetic field, and the size of the d-axis inductance can be changed by designing the size and position of the double-layer permanent magnet introduced; the fine-tuning inductance unit focuses on the q-axis magnetic field, and the non-uniform air gap introduced by design helps to fine-tune the q-axis magnetic circuit and adjust the q-axis inductance L q The variable inductance unit utilizes the saturation effect of the "low speed and heavy load" working condition and the leakage magnetic effect of the "high speed and light load" working condition to achieve the reversible inductance design under all working conditions; the coordinated design of the three units helps to achieve the optimal inductance difference in the full speed range, that is, to achieve L under the "low speed and heavy load" working condition. d >L q , increase the AC-DC axis inductance difference K ΔL+ =L d -L q ; Achieve L in "high speed and light load" working condition d <L q , increase the AC-DC axis inductance difference K ΔL- =L q -L d, thereby increasing the output torque while widening the speed regulation range; the relationship between the AC-DC axis inductance / AC-DC axis inductance difference, the motor torque / speed range, and the key dimensions in the hybrid inductance unit is derived, and based on the optimal principle of the AC-DC axis inductance difference in the full-speed range, the key parameters of the motor are accurately and quickly determined.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. The present invention proposes a "hybrid inductance unit design" method, which innovatively introduces a variable inductance unit, a constant inductance unit and a fine-tuning inductance unit into the rotor at the same time; the magnetic circuits of the three units are separated and non-interfering, which alleviates the magnetic flux coupling and helps to carry out targeted design of each inductance unit.

[0037] 2. The constant inductance unit in the present invention focuses on the d-axis magnetic field, and the size of the d-axis inductance can be changed by designing the size and position of the double-layer permanent magnet introduced; the fine-tuning inductance unit focuses on the q-axis magnetic field, and the non-uniform air gap introduced by design helps to fine-tune the q-axis magnetic circuit and adjust the q-axis inductance L. q The variable inductance unit utilizes the saturation effect of the "low speed and heavy load" working condition and the leakage magnetic effect of the "high speed and light load" working condition to achieve a reversible inductance design for all working conditions.

[0038] 3. The coordinated design of the three units in the present invention helps to achieve the optimal inductance difference in the full speed range, that is, to achieve L under the "low speed and heavy load" working condition. d >L q , increase the AC-DC axis inductance difference K ΔL+ =L d -L q ; Achieve L in "high speed and light load" working condition d <L q , increase the AC-DC axis inductance difference K ΔL- =L q -L d , thereby increasing the output torque and widening the speed regulation range.

[0039] 4. The present invention derives the relationship between the AC-DC axis inductance / AC-DC axis inductance difference, the motor torque / speed range, and the key dimensions in the hybrid inductance unit, and based on the optimal principle of the AC-DC axis inductance difference in the full-speed range, realizes accurate and rapid determination of the key parameters of the motor.

[0040] 5. The present invention proposes a multi-objective optimization method that takes into account variable working conditions. Taking into account the relationship between inductance and motor torque / speed range, the "AC-direct axis inductance difference" is introduced for the first time as a design goal and optimization goal, which helps to comprehensively improve the motor torque, speed regulation range and other performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 A schematic diagram of a design method for a hybrid inductor unit in a high-torque permanent magnet motor proposed by the present invention;

[0042] Figure 2 The structural diagram of the high torque permanent magnet motor with the optimal inductance difference between the AC and DC axes in the full speed range of the present invention;

[0043] Figure 3 A schematic diagram of the difference in inductance between the AC and DC axes under different working conditions defined in the present invention;

[0044] Figure 4 is a diagram showing the relationship between magnetic resistance and size in three inductor units of the present invention;

[0045] Figure 5 The dimension diagram of the high torque permanent magnet motor with the optimal inductance difference between the AC and DC axes in the full speed range of the present invention;

[0046] Figure 6 The magnetization curve and relative magnetic permeability diagram of the core material under different working conditions of the present invention;

[0047] Figure 7 Parameter frontier diagram of comprehensive optimization of multiple working conditions of the present invention, (a) low speed working condition (b) high speed working condition;

[0048] Figure 8 The inductance distribution diagram of the high torque permanent magnet motor with the optimal inductance difference between the AC and DC axes in the full speed range of the present invention;

[0049] Fig. 9 This is the speed torque envelope diagram of the permanent magnet motor with optimal AC and DC axis inductance difference in the full speed range of the present invention.

[0050] In the figure: 1 stator, 2 rotor, 3 armature winding, 4 rotating shaft, 5 double-layer rectangular permanent magnet, 6 small rectangular permanent magnet, 7 strip-shaped magnetic barrier, 8 small trapezoidal magnetic barrier, 9 large trapezoidal magnetic barrier. DETAILED DESCRIPTION

[0051] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings, so that those skilled in the art can better understand the advantages and features of the present invention, thereby making a clearer definition of the protection scope of the present invention. The embodiments described in the present invention are only a part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention.

[0052] See also Figure 1-Figure 2A high-torque permanent magnet motor with optimal inductance difference between AC and DC axes in the full speed range, comprising a rotating shaft 4, a rotor 2 sleeved on the rotating shaft 4, and a stator 1 sleeved coaxially on the outside of the rotor 2, wherein eight double-layer rectangular permanent magnets 5 centered on the d-axis are embedded on the rotor 2 along the circumferential direction, the eight double-layer rectangular permanent magnets 5 are evenly spaced, and each double-layer rectangular permanent magnet 5 is magnetized along the inner and outer thickness directions, and the magnetization directions of two adjacent double-layer rectangular permanent magnets 5 are opposite;

[0053] The rotor 2 is embedded with 8 small trapezoidal magnetic barriers 8 centered on the q-axis along the circumferential direction. The 8 small trapezoidal magnetic barriers 8 are arranged at intervals with 8 double-layer rectangular permanent magnets 5. Each small trapezoidal magnetic barrier 8 is provided with a small rectangular permanent magnet 6 that does not contact it on both sides along the tangential direction. The two small rectangular permanent magnets 6 are magnetized along the inner and outer thickness directions and the magnetization directions are opposite.

[0054] Eight large trapezoidal magnetic barriers 9 with their centers on the q-axis are embedded along the circumferential direction of the outer edge of the rotor 2; the eight large trapezoidal magnetic barriers 9 are evenly spaced, and the eight large trapezoidal magnetic barriers 9 are respectively arranged in one-to-one correspondence with the eight small trapezoidal magnetic barriers 8, and each large trapezoidal magnetic barrier 9 does not contact the small trapezoidal magnetic barrier 8 in the radial direction;

[0055] A strip-shaped magnetic barrier 7 which is not in contact with the double-layer rectangular permanent magnet 5 and the small rectangular permanent magnet 6 is arranged on both tangential sides of each double-layer rectangular permanent magnet 5;

[0056] The stator 1 is provided with a plurality of armature windings 3 along the circumferential direction, and the plurality of armature windings 3 are evenly spaced and distributed.

[0057] Specifically, a constant inductance unit is formed between the double-layer rectangular permanent magnet 5 and the inner surface of the rotor 2; a variable inductance unit is formed between the small trapezoidal magnetic barrier 8 and the two small rectangular permanent magnets 6 on both sides of the small trapezoidal magnetic barrier 8 and the inner surface of the rotor 2; a fine-tuning inductance unit is formed between the large trapezoidal magnetic barrier 9 and the inner surface of the rotor 2; in the constant inductance unit, the height h of the double-layer rectangular permanent magnet 5 is pm1 =2.5mm, width w pm1 =14.0mm; in the variable inductance unit, the height h of the small rectangular permanent magnet 6 pm2 =2.5mm, width w pm2 =4.0mm; in the fine-tuning inductor unit, the radial equivalent diameter length w barrier =8.0mm, tangential equivalent length l barrier =9.0mm.

[0058] In this embodiment, a variable inductance unit, a constant inductance unit and a fine-tuning inductance unit are simultaneously introduced into the rotor. In the constant inductance unit, 8 double-layer rectangular permanent magnets 5 centered on the d-axis are embedded along the circumferential direction; each double-layer rectangular permanent magnet 5 is magnetized along the inner and outer thickness directions, and the magnetization directions of two adjacent double-layer rectangular permanent magnets 5 are opposite; the design of the constant inductance unit can change the size of the d-axis inductance by designing the size and position of the double-layer rectangular permanent magnet 5, and once the structure of the double-layer rectangular permanent magnet 5 is determined, the inductance remains constant under various conditions, and a constant permanent magnetic field can be provided to ensure that the drive motor can obtain a higher output torque under all working conditions. In the variable inductance unit, 8 small trapezoidal magnetic barriers 8 are embedded along the circumferential direction with the center on the q-axis. Each small trapezoidal magnetic barrier 8 is provided with a small rectangular permanent magnet 6 that does not contact it on both sides along the tangent direction. The two small rectangular permanent magnets 6 are magnetized along the inner and outer thickness directions and the magnetization directions are opposite. The variable inductance unit helps to achieve the reversible inductance design under all working conditions through the saturation effect of working conditions such as "low speed and heavy load" and the leakage magnetic effect of working conditions such as "high speed and light load". In the fine-tuning inductance unit, 8 large trapezoidal magnetic barriers 9 with the center on the q-axis are embedded along the circumferential direction of the outer edge of the rotor as non-uniform air gaps, which helps to fine-tune the q-axis magnetic circuit and adjust the q-axis inductance L. q The variable inductance unit and the fine-tuning inductance unit are not in contact with each other in the radial direction; a strip-shaped magnetic barrier 7 is arranged between the double-layer rectangular permanent magnet 5 in the constant inductance unit and the small rectangular permanent magnet 6 in the variable inductance unit, which is not in contact with the double-layer rectangular permanent magnet 5 and the small rectangular permanent magnet 6; based on the design principle of the hybrid inductance unit, a high-torque permanent magnet motor structure with the optimal inductance difference between the direct and quadrature axes in the full speed range can be obtained, such as Figure 2 shown.

[0059] See also Figure 3 Schematic diagram of the difference in inductance between the AC and DC axes under different operating conditions defined in the present invention; As we all know, the modern traffic driving environment is becoming increasingly complex and the operating conditions are becoming increasingly diverse. In order to simulate and evaluate various operating conditions in cities or suburbs, various countries have developed a variety of different standard driving cycles to test vehicle performance, among which NEDC (New European Driving Cycles) and UDDS (Urban Dynamometer Driving Schedule) are widely used to simulate the variable operating conditions in cities or suburbs

[64] -

[66] . Figure 3 As shown, firstly, the motor operating points under different working conditions are given; electric vehicle motors often require multiple design requirements such as high output torque, wide speed regulation range, and high efficiency.

[0060] A design method for a high-torque permanent magnet motor with optimal inductance difference between AC and DC axes in all speed ranges comprises the following steps:

[0061] Theoretically, the priority of each performance varies greatly under different operating conditions. For example, under the "low speed and heavy load" condition, the output torque needs to be given priority; while under the "high speed and light load" condition, the speed range is the key performance. Output torque T e and maximum speed ω max The formula is as follows:

[0062]

[0063] Where P is the number of pole pairs, ψ δ is the effective magnetic flux, L d is the d-axis inductance, L q is the q-axis inductance, N is the number of winding turns, U lim is the voltage limit, φ pm is the permanent magnet flux, S ξ (i s ) is the saliency ratio, S ξ (i s )=L q / L d , and defines the inductance difference K between the direct and alternating axes in the full speed domain ΔL =|L d -L q |, such as Figure 3 shown.

[0064] According to formula (1), the motor inductance is closely related to the motor torque, maximum speed and other performances. In order to increase the output torque and expand the speed regulation range, it is necessary to achieve L under the "low speed and heavy load" working condition. d >L q , and increase the AC-DC axis inductance difference K ΔL+ =L d -L q ; Achieve L in "high speed and light load" working condition d <L q , and increase the AC-DC axis inductance difference K ΔL- =L q -L d .

[0065] See also Figure 4 The relationship between the magnetic resistance and size of the three inductance units is shown in the figure. The magnetic resistance R of the permanent magnet in the constant inductance unit is calculated according to the formula pm1 , the permanent magnet reluctance R in the variable inductance unit pm2 and leakage magnetic resistance R σ (i s ), and fine-tuning the magnetic barrier reluctance R in the inductor unit b The relationship is:

[0066]

[0067] The relationship between the magnetic resistance in the three inductor units and the dimensions in the three inductor units is as follows: Figure 4 As shown. In the constant inductance unit, the height of the permanent magnet is h pm1 , with a width of w pm1 ; In the variable inductance unit, the height of the permanent magnet is h pm2 , with a width of w pm2 , the tangential length of the leakage flux bridge is w σ , radial length is l σ ; In the fine-tuning inductor unit, the radial equivalent diameter length is w barrier , the tangential equivalent length is l barrier .

[0068] according to Figure 4 The key dimensions of the three inductor units given in Figure 6 The magnetization curve and relative permeability of the core material under different working conditions are given, and the permanent magnet reluctance R in the constant inductance unit pm1 , the permanent magnet reluctance R in the variable inductance unit pm2 and leakage magnetic resistance R σ (i s ), and fine-tuning the magnetic barrier reluctance R in the inductor unit b The expression is:

[0069]

[0070] In the formula, μ pm is the relative magnetic permeability of the permanent magnet; μ0 is the magnetic permeability of vacuum; L axial is the axis length, B σ is the magnetic flux density under different currents; μ1 is the magnetic permeability of silicon steel sheets; m and k are the proportional coefficients of magnetic permeability under low speed and heavy load and high speed and light load respectively; according to Figure 5 It can be seen that w barrier =πθ a R 2 barriers / (180l barrier )-(R barrier -L4) / 2.

[0071] Based on the design principle of optimal inductance difference between the direct and quadrature axes in full speed range, the evaluation function f is defined. max , to determine the key parameters of the motor:

[0072] f max =k1K ΔL- +k2K ΔL+ (4)

[0073] In the formula, k1 and k2 are the specific gravity coefficient of high-speed working condition and the specific gravity coefficient of low-speed working condition respectively, and k1+k2=1;

[0074] In order to further determine the motor parameter values, a multi-operating condition comprehensive optimization method was adopted, in which the inductance difference was used as the optimization target for the first time, such as Figure 7 The parameter frontier is given and the motor parameters are finally determined as shown in Table I:

[0075] Table I Key parameters of the motor

[0076]

[0077] See also Figure 8 , is the inductance distribution diagram of the high torque permanent magnet motor with the best inductance difference between the direct and alternating axes in the full speed range of the present invention. It can be seen that in the "low speed and heavy load" working condition, the d-axis inductance L d Greater than the q-axis inductance L q , that is, the salient rate K ρ =L q / L d <1, and the inductance difference K ΔL+ The value is large, for example, when the current is 25A, K ΔL+ =2.1; at this time, the motor has a magnetic field enhancement effect, thereby increasing the output torque and reducing the risk of irreversible demagnetization; in the "high speed and light load" working condition, the motor salient pole ratio K ρ =L q / L d >1, and the inductance difference K ΔL- The value is large, for example, when the current is -25A, K ΔL+ =1.1.

[0078] See also Fig. 9 , is the speed torque envelope diagram of the permanent magnet motor with the optimal inductance difference between the AC and DC axes in the full speed range of the present invention. It can be seen that due to the use of the hybrid inductance unit design and the mutual coordination of the three inductance units, the inductance difference K under low speed and heavy load conditions is increased. ΔL+ =L d -L q The difference in inductance K between the high speed and light load conditions ΔL- =L q -L d ; Therefore, an increased reluctance torque can be obtained, and the output torque and efficiency can be improved simultaneously within a wider speed range; in addition, when running at high speed, the magnetic flux of the permanent magnet in the variable inductance unit is completely leaked, thereby further widening the speed regulation range.

[0079] In summary, the present invention derives the relationship between the AC-D axis inductance / AC-D axis inductance difference, the motor torque / speed range, and the key dimensions in the hybrid inductance unit, and based on the optimal principle of the AC-D axis inductance difference in the full-speed range, realizes the accurate and rapid determination of the key parameters of the motor to meet the diverse performance requirements of the automotive drive motor under variable working conditions.

[0080] The description and practice disclosed in the present invention are easy to think and understand for ordinary technicians in this technical field, and several improvements and modifications can be made without departing from the principles of the present invention. Therefore, modifications or improvements made without departing from the spirit of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A high-torque permanent magnet motor with optimal inductance difference between AC and DC axes in the full speed range, comprising a rotating shaft (4), a rotor (2) sleeved on the rotating shaft (4), and a stator (1) sleeved on the outside of the rotor (2) coaxially, characterized in that: The rotor (2) is embedded with eight double-layer rectangular permanent magnets (5) centered on the d-axis along the circumferential direction, the eight double-layer rectangular permanent magnets (5) are evenly spaced and distributed, and each double-layer rectangular permanent magnet (5) is magnetized along the inner and outer thickness directions, and the magnetization directions of two adjacent double-layer rectangular permanent magnets (5) are opposite; The rotor (2) is embedded with eight small trapezoidal magnetic barriers (8) centered on the q-axis in the circumferential direction, the eight small trapezoidal magnetic barriers (8) are arranged at intervals with eight double-layer rectangular permanent magnets (5), and each small trapezoidal magnetic barrier (8) is provided with a small rectangular permanent magnet (6) that does not contact it on both sides along the tangent direction, and the two small rectangular permanent magnets (6) are magnetized along the inner and outer thickness directions and in opposite directions; Eight large trapezoidal magnetic barriers (9) with their centers on the q axis are embedded along the circumferential direction of the outer edge of the rotor (2); the eight large trapezoidal magnetic barriers (9) are evenly spaced and arranged, the eight large trapezoidal magnetic barriers (9) are respectively arranged in one-to-one correspondence with the eight small trapezoidal magnetic barriers (8), and each large trapezoidal magnetic barrier (9) does not contact the small trapezoidal magnetic barrier (8) in the radial direction; A strip-shaped magnetic barrier (7) which is not in contact with the double-layer rectangular permanent magnet (5) or the small rectangular permanent magnet (6) is arranged on both tangential sides of each double-layer rectangular permanent magnet (5); The stator (1) is provided with a plurality of armature windings (3) along the circumferential direction, and the plurality of armature windings (3) are evenly spaced and distributed.

2. A high torque permanent magnet motor with optimal inductance difference between the direct and alternating axes in full speed range according to claim 1, characterized in that: A constant inductance unit is formed between the double-layer rectangular permanent magnet (5) and the inner surface of the rotor (2); a variable inductance unit is formed between the small trapezoidal magnetic barrier (8) and the two small rectangular permanent magnets (6) on both sides of the small trapezoidal magnetic barrier (8) and the inner surface of the rotor (2); and a fine-tuning inductance unit is formed between the large trapezoidal magnetic barrier (9) and the inner surface of the rotor (2); In the constant inductance unit, the height h of the double-layer rectangular permanent magnet (5) is pm1 =2.5mm, width w pm1 =14.0mm; In the variable inductance unit, the height h of the small rectangular permanent magnet (6) is pm2 =2.5mm, width w pm2 =4.0mm; In the fine-tuning inductor unit, the radial equivalent diameter length w barrier =8.0mm, tangential equivalent length l barrier =9.0mm.

3. The design method of a high torque permanent magnet motor with optimal AC and DC axis inductance difference in all speed range according to claim 2 is characterized in that: The steps include: Step 1: Determine the optimal inductance difference between the direct and alternating axes in the full speed range and the output torque T e and maximum speed The formula is: Where P is the number of pole pairs, ψ δ is the effective magnetic flux, L d is the d-axis inductance, L q is the q-axis inductance, N is the number of winding turns, U lim is the voltage limit, φ pm is the permanent magnet flux, S ξ (i s ) is the saliency ratio, S ξ (i s )=L q / L d , and define the inductance difference K of the direct and quadrature axes in the full speed domain ΔL =|L d -L q |; According to formula (1), the motor inductance is closely related to the motor torque and maximum speed performance. In order to increase the output torque and expand the speed regulation range, it is necessary to achieve L under low speed and heavy load conditions. d >L q , and increase the AC-DC axis inductance difference K ΔL+ =L d -L q ; Achieve L under high speed and light load conditions d <L q , and increase the AC-DC axis inductance difference K ΔL- =L q -L d ; Step 2: Based on the requirement of optimal difference between the AC and DC axis inductances in the full speed range, a regional comprehensive design of the hybrid inductor unit is performed; The permanent magnet reluctance R in the constant inductance unit is calculated according to the formula pm1 , the permanent magnet reluctance R in the variable inductance unit pm2 and leakage magnetic resistance R σ (i s ), and fine-tuning the magnetic barrier reluctance R in the inductor unit b The relationship is: In the constant inductance unit, the height of the permanent magnet is h pm1 , with a width of w pm1 ; In the variable inductance unit, the height of the permanent magnet is h pm2 , with a width of w pm2 , the tangential length of the leakage flux bridge is w σ , radial length is l σ ; In the fine-tuning inductor unit, the radial equivalent diameter length is w barrier , the tangential equivalent length is l barrier ; According to the key dimensions of the three inductance units and the magnetization curve and relative permeability of the core material under different working conditions, the permanent magnet reluctance R in the constant inductance unit pm1 , the permanent magnet reluctance R in the variable inductance unit pm2 and leakage magnetic resistance R σ (i s ), and fine-tuning the magnetic barrier reluctance R in the inductor unit b The expression is: In the formula, μ pm is the relative magnetic permeability of the permanent magnet; μ0 is the magnetic permeability of vacuum; L axial is the axis length, B σ is the magnetic flux density under different currents; μ1 is the magnetic permeability of silicon steel sheet; m and k are the proportional coefficients of magnetic permeability under low speed and heavy load and high speed and light load respectively; w barrier =πθ a R 2 barriers / (180l barrier )-(R barrier -L4) / 2.

4. The design method of a high torque permanent magnet motor with optimal AC and DC axis inductance difference in all speed range according to claim 3 is characterized in that: Based on the design principle of optimal inductance difference between the direct and alternating axes in full speed range, the evaluation function f is defined. max To determine the key parameters of the motor: f max =k1K ΔL- +k2K ΔL+ (4) In the formula, k1 and k2 are the specific gravity coefficient of high-speed working condition and the specific gravity coefficient of low-speed working condition respectively, and k1+k2=1; In order to further determine the motor parameter values, a multi-operating condition comprehensive optimization method is adopted, in which the inductance difference is taken as the optimization target for the first time, and the motor parameters are finally determined.

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