Configuration method of low-power-consumption high-torque magnetic harmonic injection rotor magnetic pole array

Abstract

The invention relates to the technical field of permanent magnet motor rotor magnetic pole array configuration, in particular to a low-power-consumption high-torque magnetic harmonic injection rotor magnetic pole array configuration method, which comprises the following steps of: determining a relational expression between air gap flux density distribution and thicknesses of a permanent magnet and a yoke part; the maximum thickness point and the maximum permanent magnet thickness of the permanent magnet after the fundamental waves and the square waves are injected are determined; determining the edge thickness of the fundamental wave and the square wave injected magnetic pole; based on the maximum output torque, constructing a utility function and determining an optimal fundamental wave injection coefficient; determining a contour function of injecting fundamental waves and square waves into the bottom arc of the permanent magnet; a permanent magnet contour function based on harmonic injection is expressed as a parameter equation under a rectangular coordinate system so as to establish a finite element model of a permanent magnet bottom arc injected with fundamental waves and square waves. Under the condition that air gap fundamental waves are improved and high-reliability operation of the magnetic steel is guaranteed, higher harmonics generated by a rotor magnetic pole array are weakened, so that stable loss of an iron core of the permanent magnet motor is guaranteed, and output torque is improved.

Description

Technical Field

[0001] This invention relates to the field of permanent magnet motor rotor pole array configuration technology, and in particular to a configuration method for low-power, high-torque magnetic harmonic injection rotor pole array. Background Technology

[0002] For aviation or marine electric propulsion systems, increasing the output torque of permanent magnet motors within the same volume or mass constraints is crucial, directly determining the system's load-bearing capacity. There are generally two main approaches: increasing the stator winding current and increasing the amount of permanent magnets. However, the former can easily lead to motor overheating and insulation thermal failure, while the latter can result in an excessively large permanent magnet rotor mass, affecting dynamic characteristics. Therefore, many scholars and patents both domestically and internationally have proposed methods to modify the rotor pole array configuration. This involves combining permanent magnets of different shapes and magnetization directions to enhance their interaction with the stator winding current, thereby increasing the air gap magnetic flux density used to generate output torque.

[0003] The most typical and commonly used rotor pole array is a tile-shaped radially alternating magnetized pole array. This tile-shaped array has a simple structure and is easy to manufacture and assemble; however, its air gap magnetic flux density distribution is close to a square wave. Fourier series decomposition shows that this type of square wave magnetic field contains a large number of high-order magnetic harmonics that easily generate eddy current losses in the stator core. In particular, when the rotor lever arm is increased to further enhance the fundamental frequency of the tile-shaped pole array used to generate output torque, its high-order magnetic harmonic content becomes extremely rich. This rich high-order magnetic harmonic content, such as 3... rd 5 th 6 th and 9 th Secondary harmonics can easily lead to large eddy current losses in the stator core, resulting in system overheating and limiting the increase in output torque of the permanent magnet motor.

[0004] Traditional methods for reducing high-order harmonics in rotor magnetic pole arrays include stator and rotor skewed poles and slots, eccentric permanent magnets, changing the permanent magnet pole arc coefficient, permanent magnet top arc trimming (sine type, sine+3rd type, and tan type), and Halbach magnetic pole arrays. However, only the Halbach magnetic pole array can suppress high-order harmonics without reducing output torque; the other methods more or less damage the fundamental frequency of the air gap magnetic flux density, thus leading to a reduction in system output torque.

[0005] With a radial flux rotor as the reference frame, the Halbach pole array consists of alternating radially and tangentially magnetized tile-shaped permanent magnets. Therefore, there are significant assembly and operational repulsive forces between these permanent magnets, which not only increases manufacturing costs and difficulty but, more importantly, easily leads to the detachment of permanent magnets during operation, severely impacting the reliability of the electromagnetic drive. Although rotor sheaths can protect the Halbach permanent magnets, additional sheaths typically introduce significant air gap reluctance, thus affecting the output torque of the electromagnetic drive.

[0006] Therefore, ensuring high reliability of the magnets while increasing the fundamental frequency of the air gap and reducing the high-order harmonics generated by the rotor magnetic pole array are key factors in improving the output torque of the permanent magnet motor and reducing the core loss of the electromagnetic drive system to avoid overheating. Summary of the Invention

[0007] To address this, the present invention provides a configuration method for injecting low-power, high-torque magnetic harmonics into a rotor magnetic pole array, thereby overcoming the problems in the prior art where it is impossible to reduce the high-order harmonics generated by the rotor magnetic pole array without affecting the air gap fundamental wave and ensuring the high reliability of the magnets, resulting in high core losses and large torque pulsation.

[0008] To achieve the above objectives, the present invention provides a configuration method for a low-power, high-torque magnetic harmonic injection rotor pole array, comprising: The relationship between the air gap magnetic flux density distribution and the thickness of a permanent magnet is determined based on the principle of equivalent magnetic circuit. Determine the maximum thickness point and maximum permanent magnet thickness corresponding to the fundamental wave region of the permanent magnet after fundamental wave and square wave injection; Determine the thickness of the magnetic pole edge of the permanent magnet corresponding to the square wave region of the permanent magnet after fundamental wave and square wave injection; Construct the utility function and determine the optimal fundamental injection coefficient corresponding to the maximum torque; Determine the profile functions of the fundamental wave and square wave injected into the bottom arc of the permanent magnet; The contour function is expressed as a parametric equation in a rectangular coordinate system to establish a finite element model of the bottom arc of the injected fundamental wave and square wave permanent magnet.

[0009] Furthermore, the process of determining the maximum thickness point and the maximum permanent magnet thickness corresponding to the fundamental wave region of the permanent magnet after fundamental wave and square wave injection includes: When injecting the fundamental wave and square wave into the air gap magnetic field, the thickness of the permanent magnet varies with... θ Changes; The air gap magnetic field distribution was determined as follows get, in, The thickness of the permanent magnet. θThe azimuth angle of the permanent magnet in the magnetic circuit. g c To determine the air gap constant when injecting harmonics into the bottom arc of the permanent magnet. The fundamental wave injection coefficient is an undetermined parameter. With the square wave injection amplitude a The thickness of the permanent magnet changes accordingly to ensure the maximum allowable thickness. The amplitude of the injected square wave, It is a unit square wave function. p The number of rotor pole pairs. B r It represents the residual magnetization of the rotor permanent magnet.

[0010] Furthermore, the maximum thickness point corresponding to the fundamental wave region of the permanent magnet after fundamental wave and square wave injection is represented as follows: .

[0011] Furthermore, the maximum permanent magnet thickness corresponding to the fundamental wave region of the permanent magnet after fundamental wave and square wave injection is determined to be,

[0012] in, The maximum thickness of the permanent magnet. g c The constant air gap when injecting harmonics into the bottom arc of a permanent magnet; C α For square wave equivalent injection coefficients, .

[0013] Furthermore, the process of determining the thickness of the magnetic pole edge of the permanent magnet corresponding to the square wave region after fundamental and square wave injection includes: in, h pms The minimum edge thickness of the permanent magnet. Injecting amplitude into the square wave, C α For square wave equivalent injection coefficients, .

[0014] Furthermore, the process of constructing the utility function and determining the optimal fundamental injection coefficient corresponding to the maximum torque includes: Constructing a utility function to balance the permanent magnet thickness coefficient and the air gap magnetic load

[0015] in, U(b) For utility function, The amplitude of the fundamental air gap magnetic flux density varies withb A changing function, To balance the thickness coefficient b of the permanent magnet and Weighting factors b This is the thickness coefficient of the permanent magnet. l tr The total thickness of the rotor. b The ratio of the maximum thickness of the harmonic-injected permanent magnet to the total thickness of the rotor.

[0016] Furthermore, the process of constructing the utility function and determining the optimal fundamental injection coefficient corresponding to the maximum torque includes: Setting the first derivative of the utility function to zero, we get: ; The optimal permanent magnet thickness coefficient is determined to be... .

[0017] Furthermore, the optimal fundamental wave injection coefficient is determined. ; .

[0018] Furthermore, the profile functions of the fundamental wave and square wave injected into the bottom arc of the permanent magnet are determined as follows:

[0019] in, h pms The edge thickness of the irregular permanent magnet after harmonic injection.

[0020] Furthermore, the process of expressing the contour function as a parametric equation in a Cartesian coordinate system includes: Determine the profile function of the permanent magnet in Parametric equations for the interval; Let the polar radius in rectangular coordinates r equal ; The profile function of the permanent magnet injected with harmonic bottom arc is obtained in Parametric equations for the interval: ; ;

[0021] in, R i This is the minimum inner diameter of the radial rotor permanent magnet.

[0022] Compared with existing technologies, the advantages of this invention lie in its ability to accurately quantify the mapping relationship between the air gap magnetic flux density distribution and the structural dimensions of the magnetic pole array by establishing a direct relationship between the air gap magnetic field distribution and the permanent magnet and the rotor back iron thickness. The desired air gap magnetic flux density distribution waveform can be arbitrarily preset, and the parameterized equations for the rotor magnetic pole array shape can be directly obtained through the established harmonic injection mathematical model, providing a theoretical basis for the forward design of the motor rotor magnetic pole array.

[0023] Furthermore, the desired fundamental wave and square wave are injected into the bottom arc of the permanent magnet. This stabilizes core losses and torque pulsation by injecting the fundamental wave, while the square wave prevents problems such as insufficient machining and irreversible demagnetization caused by excessively thin permanent magnet edges. Simultaneous injection of the square wave and fundamental wave into the air gap magnetic field improves the motor's operational stability and reliability, reduces energy loss, and increases motor efficiency and lifespan.

[0024] Furthermore, by injecting the desired fundamental and square waves into the bottom arc of the permanent magnet, the motor torque is effectively increased. While increased motor torque inevitably leads to increased core losses in the permanent magnet motor, this solution effectively weakens the high-order harmonics generated by the rotor pole array through fundamental wave injection, reducing energy loss and ensuring stable core losses in the permanent magnet motor. By determining the profile functions of the fundamental and square waves injected into the bottom arc of the permanent magnet, the air gap fundamental wave is effectively enhanced while ensuring reliable operation of the magnets. This pole array, featuring irregularly shaped permanent magnets with radially alternating magnetization, offers advantages over traditional Halbach pole arrays with multi-directional magnetization, including simpler structure, easier assembly, and lower processing costs. Attached Figure Description

[0025] Figure 1 This is a flowchart illustrating the steps of the method for configuring a low-power, high-torque magnetic harmonic wave injection rotor pole array in the embodiment. Figure 2 The figure shows the variation curves of the average magnetic flux density of the air gap with the thickness of the permanent magnet for several air gap lengths in the embodiment. Figure 3 This is a schematic diagram of the finite element model of the bottom arc injection magnetic pole array of the fundamental and square wave permanent magnets in the embodiment; Figure 4 The image shows the magnetic flux density distribution cloud map of the radial rotor under three different magnetic pole array excitations in the embodiment, which are driven by the composite magnetic flux electric drive. Figure 5 This is a comparison diagram of the harmonic components of the air gap magnetic field of the three magnetic pole arrays in the embodiment. Figure 6 This is a comparison diagram of the back electromotive force waveforms of the three magnetic pole arrays in the embodiment; Figure 7 This is a comparison chart of the harmonic content of the three magnetic pole arrays in the embodiment; Figure 8This is a comparison diagram of the output torque waveforms of the three magnetic pole arrays in the embodiment; Figure 9 The figure shows the variation of the average output torque of the composite flux electromagnetic drive with the armature current angle under the excitation of the three magnetic pole arrays in the embodiment. Figure 10 The graph shows the variation of core loss density of the stator and rotor silicon steel materials in the embodiment under different alternating magnetic field parameters. Figure 11 This is a comparison diagram of the core losses of the three magnetic pole arrays in the embodiment; Figure 12 This is a BH curve of the NdFeB permanent magnet N42UH in the embodiment at 150°C; Figure 13 The image shows the distribution cloud map of the demagnetization coefficient of the bottom arc injected magnetic poles of the fundamental and square wave permanent magnets in the embodiment. Detailed Implementation

[0026] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0027] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0028] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0029] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0030] Please see Figure 1 The diagram shows a flowchart of the steps involved in configuring a low-power, high-torque magnetic harmonic wave injection rotor pole array in an embodiment. The method described in this invention includes: S1, Based on the principle of equivalent magnetic circuit, the relationship between the air gap magnetic flux density distribution and the thickness of the permanent magnet is determined; S2, determine the maximum thickness point and maximum permanent magnet thickness corresponding to the fundamental wave region of the permanent magnet after fundamental wave and square wave injection; S3, determine the thickness of the magnetic pole edge of the permanent magnet corresponding to the square wave region of the permanent magnet after the fundamental wave and square wave injection; S4, construct the utility function and determine the optimal fundamental injection coefficient corresponding to the maximum torque; S5, determine the profile functions of the fundamental wave and square wave injected into the bottom arc of the permanent magnet; S6. The contour function is expressed as a parametric equation in a rectangular coordinate system to establish a finite element model of the injected fundamental wave and the bottom arc of the square wave permanent magnet.

[0031] Determining the air gap magnetic field distribution based on the equivalent magnetic circuit principle With the thickness of the permanent magnet The process of establishing relationships between them includes: (1) in, H c For the coercivity of the rotor permanent magnet, B r The residual magnetization of the rotor permanent magnet, The air gap magnetic flux generated per unit area of ​​the rotor magnetic pole array, g(θ) The distribution function of air gap length with respect to circumferential angle. dR For a magnetic pole array, unit magnetic reluctance, μ r For the relative permeability of permanent magnets, μ 0 For the vacuum permeability of permanent magnets, ds It is a small element of the surface area of ​​the magnetic pole, that is, a small element in calculus.

[0032] The relationship between the air gap magnetic flux density distribution and the thickness of the permanent magnet is obtained as follows: (2) Please see Figure 2 As shown, this is a graph illustrating the variation of the average air gap magnetic flux density with the thickness of the permanent magnet for several air gap lengths in the embodiment. The fitted air gap magnetic flux density function for the tile-shaped magnetic pole array is determined as follows: (3) in, x The thickness of the permanent magnet. g The length of the air gap. The thickness of the permanent magnet is x The average magnetic flux density of the air gap at that time.

[0033] Please continue reading. Figure 2As shown, without considering the effects of leakage flux and the magnetic fields of the stator core and armature, a smaller air gap results in a stronger air gap magnetic flux density for the same permanent magnet thickness. With increasing permanent magnet thickness, while the magnetomotive force increases, the internal resistance of the permanent magnet also increases. Therefore, regardless of the air gap length, once the permanent magnet thickness reaches a certain size, further increases in thickness have a negligible effect on improving the air gap magnetic flux density.

[0034] When the permanent magnet is a tile-shaped permanent magnet, the thickness of the tile-shaped permanent magnet does not change with the circumferential angle, thus obtaining... ; The relationship between the air gap magnetic flux density distribution and the thickness of the permanent magnet in a tile-shaped permanent magnet is determined by the following formula: (4) Where l is a constant, and is the sum of the thickness of the permanent magnet and the length of the air gap.

[0035] Specifically, the thickness of the permanent magnet is determined to be constant. C h The air gap magnetic flux density of the radially magnetized tile-shaped permanent magnet is: (5) (6) in, It is a unit square wave function. △m It is a constant. Δm=B r / l*C h , p The number of rotor pole pairs. The period of the magnetic field distribution in the air gap space driven by the composite magnetic flux.

[0036] Represent the unit square wave function using a Fourier series: (7) The fundamental amplitude of the tile-shaped magnetic pole is obtained. .

[0037] Determine the bottom arc function of the permanent magnet: Specifically, the air gap is determined to be constant when harmonics are injected into the bottom arc of the permanent magnet. g c The relationship between the air gap magnetic flux density distribution and the thickness of the permanent magnet is obtained as follows: (8) Specifically, to prevent the permanent magnet from becoming too thin at the edges and undergoing irreversible demagnetization under high temperature and high electrical load, the thickness of the permanent magnet should meet the following requirements: (9) Injecting the fundamental wave only into the air gap magnetic field hour, In this situation, the edges of the permanent magnet become sharp, making it difficult to manufacture. Furthermore, sharp edges can lead to irreversible demagnetization. Therefore, the edges of the permanent magnet should retain a certain thickness. Consequently, while injecting the fundamental wave into the magnetic field, a square wave must be injected into the air gap magnetic field.

[0038] Specifically, the process of determining the change in the thickness of the permanent magnet with θ when injecting the fundamental wave and square wave into the air gap magnetic field includes: The air gap magnetic field distribution was determined as follows (10) get, (11) in, The amplitude of the injected square wave, The fundamental wave injection coefficient is an undetermined parameter. With the square wave injection amplitude a The thickness of the permanent magnet changes accordingly to ensure the maximum allowable thickness.

[0039] To reduce core loss and torque pulsation, and to avoid problems such as the permanent magnet edge being too thin, making it impossible to process and causing irreversible demagnetization, square wave and fundamental wave are injected into the air gap magnetic field simultaneously.

[0040] Determine the edge thickness of the fundamental and square wave injected magnetic poles: (12) in, h pms The minimum edge thickness of the permanent magnet. Injecting amplitude into the square wave, C α For square wave equivalent injection coefficients, .

[0041] Specifically, the fundamental wave and square wave are injected into the bottom arc of the permanent magnet. The maximum thickness of the permanent magnet should not exceed the sum of the thickness of the original tile-shaped magnetic pole and its rotor yoke, resulting in: (13) Once the thickness of the permanent magnet exceeds a certain value, further increasing the thickness of the permanent magnet has a negligible effect on improving the electromagnetic drive performance.

[0042] Pick

[0043] in, Injecting magnetic pole thickness coefficients for the undetermined fundamental and square waves. This refers to the thickness of the rotor yoke. l tr This represents the total thickness of the rotor.

[0044] The rotor's N and S poles have a consistent shape and exhibit a periodic distribution. Only using the square wave injection function Periodicity is used to simplify the derivation.

[0045] Determine the maximum thickness point of the fundamental and square wave injected into the permanent magnet. p max When the fundamental wave and square wave are injected into the air gap magnetic field, the determined thickness of the permanent magnet varies with... θ In the variation of the inscribed angle θ The partial differential is zero, that is (14) It was found that the point of maximum thickness of the permanent magnet for both the fundamental and square waves injected at the maximum bottom arc appeared at... (15) Maximum permanent magnet thickness is (16) in, The fundamental wave injection coefficient is an undetermined parameter. With the square wave injection amplitude a Change with change g c The constant air gap when injecting harmonics into the bottom arc of a permanent magnet.

[0046] Based on equations (13)-(16), we obtain: (17) Substituting equation (7) into the air gap magnetic field distribution, we can obtain the air gap magnetic field distribution with a unit square wave function injected into the air gap magnetic field: (18) For star-connected winding electromagnetic drives, the third harmonic of the air gap magnetic field has almost no effect on the output waveform and average torque, and other magnetic field harmonics above the third only produce torque pulsation.

[0047] Based on the electromagnetic principle of electric motors, the average output torque of a permanent magnet motor using fundamental and square wave permanent magnet bottom arc injection can be expressed as: (19) in, T For output torque, K e The electrical power waveform coefficient of the motor, K w For winding coefficient, K i For current coefficient, For motor electrical load, The ratio of the motor's outer diameter to its axial length. D out The maximum outer diameter of the composite flux electromagnetically driven axial rotor.

[0048] Based on equation (19), the magnetic load is obtained. The larger the value, the greater the output torque of the composite flux electromagnetic drive. A m It is a magnetic load.

[0049] Due to magnetic load The square wave injection function *a* is monotonically increasing in the interval (0, +∞), therefore it has no extreme points. For a given maximum permanent magnet thickness, a larger square wave injection coefficient results in a larger output torque. However, a larger square wave injection function also leads to a higher harmonic content. Therefore, to improve magnet processing performance and avoid introducing more higher harmonics, h pms Take 2mm.

[0050] Fundamental wave injection coefficient The larger the output torque, the greater the thickness of the permanent magnet. That is, the output torque is a function of the fundamental magnetic flux density, expressed as... (20) The first and second derivatives of the function of the fundamental magnetic flux density are respectively (twenty one) in, B load For the fundamental magnetic flux density, the fundamental magnetic flux density function is as follows: b Monotonically increasing, without extreme points and as b The rate of increase in air gap magnetic load also slows down with the increase in air gap magnetic load. When b As the magnetic flux density approaches infinity, the rate of change of the fundamental magnetic flux density approaches zero. Therefore, a utility function is constructed. To determine the optimal permanent magnet thickness coefficient, thereby balancing the permanent magnet thickness and the air gap magnetic load.

[0051] (twenty two) in The increase in air gap magnetic load per unit thickness of permanent magnet. b The ratio of the maximum thickness of the harmonic-injected permanent magnet to the total thickness of the rotor is called the permanent magnet thickness coefficient. The amplitude of the fundamental air gap magnetic flux density varies with b A changing function; Setting the first derivative of the utility function to zero, we get: (twenty three) in, U(b)For utility function, l tr This represents the total thickness of the rotor.

[0052] Therefore, the optimal utility permanent magnet thickness coefficient is (twenty four) Combining the optimal permanent magnet thickness coefficient with equation (17), we obtain the optimal fundamental wave injection coefficient. The profile functions of the final fundamental wave and square wave injected into the bottom arc of the permanent magnet can be expressed as: (25) in, h pms The edge thickness of the irregular permanent magnet after harmonic injection.

[0053] Specifically, the establishment of finite element models for fundamental and square wave permanent magnet bottom arc injection and the optimal harmonic injection coefficients are as follows: Establish finite element models of the bottom arc of the injected fundamental wave and square wave permanent magnet; The process of expressing the profile function of a permanent magnet based on harmonic injection as a parametric equation in a Cartesian coordinate system includes: Determine the profile function of the permanent magnet in Parametric equations for the interval; Let the polar radius in rectangular coordinates r equal ; The profile function of the permanent magnet injected with harmonic bottom arc is obtained in Parametric equations for the interval: (26) (27) in, R i This is the minimum inner diameter of the radial rotor permanent magnet.

[0054] Please see Figure 3 As shown, this is a schematic diagram of the finite element model of the fundamental and square wave permanent magnet bottom arc injection magnetic pole array in the embodiment. The embodiment uses a semi-analytical method to obtain the optimal... b and h pms To account for the effects of parallel magnetization and leakage magnetic flux between permanent magnet poles on the harmonic injection coefficient, permanent magnet thickness coefficient, and minimum edge thickness of the fundamental and square wave injected magnetic poles, the finite element model has a total of 196,071 mesh elements.

[0055] Traditional methods for reducing high-order harmonics in rotor pole arrays include stator and rotor skewed poles and slots, eccentric permanent magnets, changing the pole arc coefficient of permanent magnets, permanent magnet top arc trimming (sine type, sine+3rd type, and tan type), and Halbach pole arrays. However, only Halbach pole arrays can suppress certain orders of high-order harmonics without reducing output torque; the other methods usually damage the fundamental frequency of the air gap magnetic flux density, leading to a reduction in system output torque. Furthermore, Halbach pole arrays typically consist of alternating radially and tangentially magnetized tile-shaped permanent magnets. Therefore, there are significant assembly and operational repulsive forces between these permanent magnets, which not only greatly increases assembly costs and difficulty but, more importantly, easily leads to the detachment of permanent magnets during electromagnetic drive operation, affecting its reliability, especially for rotor designs with large air gap diameters. Although Halbach permanent magnets can be protected by rotor sheaths, additional rotor sheaths usually introduce significant air gap reluctance or rotor sheath eddy currents, thereby reducing the output torque of the electromagnetic drive and increasing rotor heating. In contrast, the fundamental and square wave permanent magnet bottom arc injection magnetic pole array proposed in this scheme does not have complex multi-directional magnetized permanent magnets, thus avoiding the unreliability caused by the extremely large magnetic repulsion between magnetic poles, as well as the problems of additional rotor sheath eddy current losses.

[0056] In the current embodiment, the fundamental wave and square wave permanent magnet bottom arc injection magnetic pole arrays are compared with traditional typical tile-shaped stimulation arrays and Halbach magnetic pole arrays using the finite element method. All three magnetic pole arrays are positioned on the radial rotor side of a composite flux three-dimensional winding electromagnetic drive with the same structure and current input parameters to ensure fairness in the comparison.

[0057] Compare the harmonic content of the air gap magnetic flux density; Please see Figure 4 As shown, this is a magnetic flux density distribution cloud map of the radial rotor under three different magnetic pole array excitation methods in the embodiment, driven by the composite magnetic flux. From left to right, these are the magnetic flux density distribution cloud maps of the tile-shaped radial magnetized poles, the Halbach pole array, and the back iron permanent magnet synergistic shaping array. Compared to the typical tile-shaped radial alternating magnetic pole array, the Halbach and the proposed back iron permanent magnet synergistic shaping magnetic pole array can effectively reduce magnetic saturation at the rotor back iron, avoiding an increase in the equivalent magnetic reluctance of the rotor back iron. The main reason is that the Halbach tangentially magnetized permanent magnet can guide some magnetic lines of force to link directly with the winding without passing through the back iron. However, the large magnetic repulsion between the tangentially magnetized permanent magnet and its radially magnetized permanent magnet is difficult to avoid. In contrast, the rotor with back iron permanent magnet synergistic shaping proposed in this scheme only has radially alternating magnetized permanent magnets, avoiding magnetic repulsion and ensuring the reliability of rotor operation.

[0058] Please see Figure 5 As shown, this is a comparison of the harmonic components of the air gap magnetic field for the three types of magnetic pole arrays in the embodiments. The back-iron permanent magnet synergistic shaping magnetic pole array achieves the highest fundamental magnetic flux density compared to the other two typical magnetic pole arrays. By injecting a specific amount of fundamental and square waves into the air gap magnetic field driven by the composite magnetic flux through the synergistic shaping of the back iron and permanent magnet, the fundamental magnetic flux density of the air gap driven by the composite magnetic flux is effectively improved. In addition, the third and fifth magnetic harmonics in the air gap magnetic field are also effectively suppressed, thereby helping to reduce the core loss caused by the higher harmonics of the system. The other orders and smaller amplitudes of the higher magnetic harmonics of the back-iron permanent magnet synergistic shaping magnetic pole array are basically consistent with those of the traditional magnetic pole array, and do not introduce excessively high frequency core loss. Although the Halbach magnetic pole array improves the fundamental amplitude of the air gap magnetic flux density to a certain extent compared with the traditional tile-shaped radially alternating magnetized magnetic pole array, its third magnetic harmonic is not effectively suppressed. The above comparison results verify that the proposed rotor back iron and permanent magnet synergistic shaping method can indeed suppress high-order harmonics while increasing the fundamental magnetic flux density of the air gap, creating favorable conditions for low core loss and high torque output.

[0059] Three types of magnetic pole arrays include fundamental and square wave permanent magnet bottom arc injection magnetic pole arrays, traditional typical tile-shaped stimulation arrays, and Halbach magnetic pole arrays.

[0060] The back iron permanent magnet collaborative shaping array is a magnetic pole array injected into the bottom arc of the fundamental wave and square wave permanent magnets.

[0061] The waveforms of the winding back electromotive force and the harmonic content of the three magnetic pole arrays were compared. When a three-phase symmetrical current of a certain frequency is applied to the stator winding of a composite flux electromagnetic drive, the armature winding will generate an armature rotating magnetic field with the same number of pole pairs as the rotor pole array. This armature rotating magnetic field attracts the rotor permanent magnet to rotate at the same frequency. Simultaneously, the air gap magnetic fields of different orders generated by the rotor pole array will produce back electromotive force (EMF) waveforms of different orders in the three-phase windings. The fundamental wave of this back EMF interacts with the fundamental wave of the armature current to output effective electromagnetic power and electromagnetic torque. The remaining higher-order back EMF harmonics interact with the armature current, only producing torque pulsations. Therefore, a thorough analysis of the back EMF harmonic distribution under the combined action of the shaped rotor pole array is crucial for demonstrating the superiority of the proposed pole array.

[0062] Please participate separately. Figure 6 and Figure 7The figures show the back electromotive force waveforms of the three types of magnetic pole arrays in the embodiments and a comparison of the harmonic content of each type of magnetic pole array. The back-iron permanent magnet synergistic shaping magnetic pole array can effectively increase the fundamental back electromotive force while suppressing the 5th and 9th back electromotive force harmonics. The fundamental back electromotive force amplitude of the Halbach magnetic pole array is indeed improved; however, for rotors with large electromagnetic radius and few pole pairs, the suppression effect of Halbach magnetization on higher harmonics in the air gap is limited, resulting in a higher 5th harmonic content in the Halbach magnetic pole array.

[0063] The output torque characteristics and magnet utilization rates of the three magnetic pole arrays were compared. Please see Figure 8 The figure shows a comparison of the output torque waveforms of the three magnetic pole arrays in the embodiment. The average torques of the traditional typical tile-shaped magnetic pole array, Halbach magnetic pole array, and back-iron permanent magnet synergistic shaping magnetic pole array are 930.0 Nm, 938.9 Nm, and 962.3 Nm, respectively. The output torque of the composite flux electromagnetic drive of the back-iron permanent magnet synergistic shaping magnetic pole array can be effectively increased by 32.3 Nm. The average torque of the Halbach magnetic pole array is only increased by 8.9 Nm. In addition, the torque pulsation before and after the injection of the base and square waves is basically the same, and the pulsation is mainly caused by the 7th back electromotive force harmonic.

[0064] Please see Figure 9 As shown, this graph illustrates the variation of the average output torque of the composite flux electromagnetic drive with the armature current angle under the excitation of the three magnetic pole arrays in the embodiment. The maximum torque point of the back-iron permanent magnet synergistic shaping magnetic pole array of this invention does not occur at the point where the current angle is zero. Therefore, it can be seen that the back-iron permanent magnet synergistic shaping magnetic pole array can introduce additional reluctance torque. The maximum torque point of the traditional tile-shaped and Halbach magnetic pole arrays occurs in the region where the current angle is zero. That is, the d-axis and q-axis inductances of the traditional tile-shaped and Halbach magnetic pole arrays are basically the same, and they cannot introduce additional reluctance torque.

[0065] Because the rotor back iron permanent magnet shaped pole array incorporates rotor poles embedded within the rotor back iron, its total radial permanent magnet usage is only 0.899L. In contrast, the total usage of traditional tile-shaped and Halbach poles is 0.905L. This means the magnet utilization rate of the back iron permanent magnet shaped pole array is 1070.4 Nm / L, an improvement of 42.8 Nm / L compared to the 1027.6 Nm / L of the traditional tile-shaped pole array. Therefore, the back iron permanent magnet shaped pole array can generate greater torque with less magnet usage.

[0066] The stator and rotor core losses of three types of magnetic pole arrays are compared. Neglecting the relatively small hysteresis effect of silicon steel, the stator and rotor core losses mainly originate from the eddy current losses induced within the stator and rotor cores by the alternating air gap magnetic field. Excessive core losses can easily lead to severe core heating, limiting the use of larger electrical loads in composite flux electromagnetic drives to improve system torque density.

[0067] Please see Figure 10 and Figure 11 As shown, these are, respectively, graphs showing the variation of core loss density of the stator and rotor silicon steel materials under different alternating magnetic field parameters, and comparison graphs showing the core loss of the three magnetic pole arrays. Figure 10 It is known that the greater the amplitude of the magnetic flux density acting on the stator and rotor cores, or the higher the frequency of the magnetic field alternation, the greater the core loss density of the stator and rotor. Moreover, the frequency of the magnetic field alternation has a greater impact on core loss than the magnetic flux density amplitude, exhibiting an exponential growth trend. That is, suppressing the amplitude of high-frequency air gap magnetic flux density is an effective means to reduce core loss. However, compared with the traditional typical tile-shaped magnetic pole array, the back-iron permanent magnet synergistic shaping magnetic pole array, while improving the fundamental magnetic flux density and torque output of the air gap, did not increase the additional stator and rotor core loss, verifying the effectiveness of the synergistic shaping method. The fundamental reason is that the back-iron permanent magnet synergistic shaping magnetic pole array, while improving the fundamental magnetic flux density of the air gap, also suppresses the amplitude of higher-order magnetic harmonics, including the third and fifth higher-order magnetic harmonics. Although the Halbach magnetic pole array improves the output torque of the traditional tile-shaped magnetic pole array to some extent, its total stator and rotor loss increases by about 800W due to the rotor sheath eddy current loss.

[0068] Verify the demagnetization characteristics of the back iron permanent magnet cooperative shaping magnetic pole array; Analysis of demagnetization resistance is crucial for the development of back-mounted permanent magnet synergistic shaping magnetic pole arrays, especially for high-electric-load, high-temperature electromagnetic drives. Please refer to [link / reference]. Figure 12 The figure shows the BH curve of the NdFeB permanent magnet N42UH in the embodiment at 150°C. When the armature magnetic field is applied to the permanent magnet, the system operating line OP can be calculated using the equivalent magnetic circuit principle. The intersection of the operating line OP and the BH curve of the permanent magnet is the operating point of the permanent magnet. When the applied reverse magnetic field is large enough that the operating point of the permanent magnet exceeds the knee of the BH curve, the permanent magnet will undergo irreversible demagnetization. That is, the remanence of the permanent magnet will decrease from B... r0 Descend to B r1 Therefore, the degree of demagnetization of a permanent magnet can be determined by the demagnetization coefficient B. r1 / B r0 An evaluation is conducted. A demagnetization coefficient of 1 indicates that the permanent magnet is completely undemagnetized, while a demagnetization coefficient of 0 indicates that the permanent magnet is completely demagnetized.

[0069] Please see Figure 13As shown, it is a cloud map of the demagnetization coefficient distribution of the bottom arc injected magnetic poles of the fundamental and square wave permanent magnets in the embodiment. Figure 13 It can be seen that the back-mounted permanent magnet shaped magnetic pole array did not undergo irreversible demagnetization even at a high temperature of 150℃, with a minimum demagnetization coefficient of 0.9919. That is, the back-mounted permanent magnet shaped magnetic pole array can operate reliably at high temperatures.

[0070] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

[0071] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for configuring a low-power, high-torque magnetic harmonic wave injection rotor pole array, characterized in that, include: The relationship between the air gap magnetic flux density distribution and the thickness of a permanent magnet is determined based on the principle of equivalent magnetic circuit. Determine the maximum thickness point and maximum permanent magnet thickness corresponding to the fundamental wave region of the permanent magnet after fundamental wave and square wave injection; Determine the thickness of the magnetic pole edge of the permanent magnet corresponding to the square wave region of the permanent magnet after fundamental wave and square wave injection; Construct the utility function and determine the optimal fundamental injection coefficient corresponding to the maximum torque; Determine the profile functions of the fundamental wave and square wave injected into the bottom arc of the permanent magnet; The contour function is expressed as a parametric equation in a rectangular coordinate system to establish a finite element model of the bottom arc of the injected fundamental wave and square wave permanent magnet.

2. The configuration method for low-power, high-torque magnetic harmonic injection rotor pole array according to claim 1, characterized in that, The process of determining the maximum thickness point and maximum permanent magnet thickness corresponding to the fundamental wave region of the permanent magnet after fundamental wave and square wave injection includes: When injecting the fundamental wave and square wave into the air gap magnetic field, the thickness of the permanent magnet varies with... θ Changes; The air gap magnetic field distribution was determined as follows get, in, The thickness of the permanent magnet. θ The azimuth angle of the permanent magnet in the magnetic circuit. g c To determine the air gap constant when injecting harmonics into the bottom arc of the permanent magnet. The fundamental wave injection coefficient is an undetermined parameter. With the square wave injection amplitude a The thickness of the permanent magnet changes accordingly to ensure the maximum allowable thickness. The amplitude of the injected square wave, It is a unit square wave function. p The number of rotor pole pairs. B r It represents the residual magnetization of the rotor permanent magnet.

3. The configuration method for low-power, high-torque magnetic harmonic injection rotor pole array according to claim 2, characterized in that, The maximum thickness point corresponding to the fundamental wave region of the permanent magnet after fundamental wave and square wave injection is represented as follows: 。 4. The configuration method for low-power, high-torque magnetic harmonic injection rotor pole array according to claim 3, characterized in that, The maximum permanent magnet thickness corresponding to the fundamental wave region of the permanent magnet after fundamental wave and square wave injection is determined to be [value missing]. ； in, The maximum thickness of the permanent magnet. g c The constant air gap when injecting harmonics into the bottom arc of a permanent magnet; C α For square wave equivalent injection coefficients, .

5. The configuration method for low-power, high-torque magnetic harmonic injection rotor pole array according to claim 4, characterized in that, The process of determining the thickness of the magnetic pole edge of the permanent magnet corresponding to the square wave region after fundamental and square wave injection includes: ； in, h pms The minimum edge thickness of the permanent magnet. Injecting amplitude into the square wave, C α For square wave equivalent injection coefficients, .

6. The configuration method for low-power, high-torque magnetic harmonic injection rotor pole array according to claim 5, characterized in that, The process of constructing the utility function and determining the optimal fundamental injection coefficients corresponding to the maximum torque includes: Constructing a utility function to balance the permanent magnet thickness coefficient and the air gap magnetic load ； in, U(b) For utility function, The amplitude of the fundamental air gap magnetic flux density varies with b A changing function, To balance the thickness coefficient b of the permanent magnet and Weighting factors b This is the thickness coefficient of the permanent magnet. l tr The total thickness of the rotor. b The ratio of the maximum thickness of the harmonic-injected permanent magnet to the total thickness of the rotor.

7. The configuration method for low-power, high-torque magnetic harmonic injection rotor pole array according to claim 6, characterized in that, The process of constructing the utility function and determining the optimal fundamental injection coefficients corresponding to the maximum torque includes: Setting the first derivative of the utility function to zero, we get: ； The optimal permanent magnet thickness coefficient is determined to be... 。 8. The configuration method for low-power, high-torque magnetic harmonic injection rotor pole array according to claim 7, characterized in that, Determine the optimal fundamental wave injection coefficient ; 。 9. The configuration method for low-power, high-torque magnetic harmonic injection rotor pole array according to claim 8, characterized in that, The profile functions for the fundamental wave and square wave injected into the bottom arc of the permanent magnet are determined as follows: ； in, h pms The edge thickness of the irregular permanent magnet after harmonic injection.

10. The configuration method for low-power, high-torque magnetic harmonic injection rotor pole array according to claim 9, characterized in that, The process of expressing the contour function as a parametric equation in a Cartesian coordinate system includes: Determine the profile function of the permanent magnet in Parametric equations for the interval; Let the polar radius in rectangular coordinates r equal ; The profile function of the permanent magnet injected with harmonic bottom arc is obtained in Parametric equations for the interval: ； ； in, R i This is the minimum inner diameter of the radial rotor permanent magnet.

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