Design method of three-triple-phase split tooth permanent magnet Vernier motor

Abstract

The application discloses a kind of three-three-phase split tooth permanent magnet vernier motor design methods, comprising: the outer rotor of permanent magnet (2) and rotor core, permanent magnet (2) simultaneously adopt axial and circumferential sectional design, surface is pasted in rotor core inside, magnetization direction is radial magnetization and N pole and S pole alternate arrangement;Stator (4) adopts split tooth structure, and interdental placement armature winding (3). Armature winding (3) adopts three-three-phase fractional slot concentrated winding mode. The stator modulation pole of the motor adopts multiple working wave design, more working permeance and magnetic flux density harmonic can be introduced, so as to improve the back electromotive force and output torque of motor;Permanent magnet (2) simultaneously adopt axial and circumferential sectional design, can effectively reduce permanent magnet eddy current loss, and facilitate installation manufacturing;Armature winding (3) adopts three-three-phase connection mode, can increase the torque output of motor and reduce the torque ripple of motor, and the increase of space phase number can make motor have good fault-tolerant operation potential.

Description

Technical Field

[0001] This invention relates to a design method for a three-phase split-tooth permanent magnet vernier motor, belonging to the field of motor design. It is suitable for applications requiring high motor torque capacity and reliability, such as electric vehicles and wind power generation. Background Technology

[0002] Permanent magnet motors have attracted much attention in recent years due to their advantages such as simple structure, high efficiency, stable operation, and high torque density. In industrial applications, the traditional method to achieve low-speed, high-torque operation is to use the motor in conjunction with a gear reduction device. This method not only increases the size and weight of the entire system but also introduces problems such as noise, reduced efficiency, and slower response speed. Permanent magnet vernier motors based on the "magnetic field modulation principle" can improve the torque density of permanent magnet motors. In this type of motor, a low-speed permanent magnet magnetic field is modulated in the air gap through the modulation of the flux modulation poles to generate a high-speed magnetic field. The stator windings are designed according to the high-speed rotating magnetic field, thereby achieving low-speed, high-torque operation of the motor.

[0003] Chinese patent application number 201711308185.2 proposes a topology that integrates a novel magnetic gear into a traditional permanent magnet motor. By slotting the outer rotor and stator and embedding the permanent magnet within the inner rotor, it reduces torque ripple, decreases vibration and noise during motor operation, and improves the overall torque density and efficiency of the composite motor. However, this magnetic gear composite motor has a three-layer air gap structure and two rotating parts, resulting in a complex mechanical structure and increased manufacturing difficulty. Chinese patent application number 202110988212.5 proposes a design method for a low-harmonic dual-three-phase fractional-slot permanent magnet synchronous motor. By using different winding coil turns to eliminate subharmonics, it effectively reduces permanent magnet eddy current losses, unbalanced magnetic pull, and torque ripple. However, this winding configuration requires a specific slot-pole combination.

[0004] Therefore, it is essential to conduct research on how to reduce torque ripple and improve efficiency of motors while maintaining high torque and power density at relatively low speeds, based on the principle of magnetic field modulation. Summary of the Invention

[0005] The purpose of this invention is to solve the problems existing in the prior art and to propose a design method for a three-phase split-tooth permanent magnet vernier motor with high torque density, high power density, high efficiency, and low torque ripple, so as to meet the performance requirements of industrial applications for motors that can improve efficiency and reduce torque ripple while outputting high torque at low speed.

[0006] To achieve the above objectives, the technical solution adopted in this invention is as follows: In the radial direction, from the inside out, there are stator (4), permanent magnet (2), and rotor (1), with an air gap between the stator and the outer rotor; wherein, the stator (4) adopts a split-tooth structure, with each armature tooth split into two modulation teeth (6), the armature winding (3) is located between the stator teeth, and a three-phase concentrated winding is adopted; the permanent magnet (2) adopts a segmented design in both axial and circumferential directions, is surface-mounted on the inner side of the rotor core, and the magnetization direction is radial magnetization with alternating N and S poles; wherein the stator core and rotor core are made of magnetically conductive materials such as silicon steel sheets, and the permanent magnet (2) is made of neodymium iron boron material; according to the modulation pole number N... st and the number of permanent magnet pole pairs P r Determine the number of armature winding pole pairs P s Satisfying P s =|N st -P r |=|36-28|=8, Modulation pole number N st =2Z=36. The stator teeth (5) are split into two modulation teeth (6) through slotting. The pitch angle α between the modulation teeth is not equal to the slotting angle α0: α≠α0. The permanent magnets (2) are radially magnetized and the magnetization directions of adjacent permanent magnets (2) are opposite. Under the condition of satisfying the magnetic field modulation relationship, the slot pitch angle of the motor is determined. Z represents the number of slots in the motor. The stator winding arrangement is determined based on the slot pitch angle. Assuming that one slot is numbered 1, the remaining slots are numbered 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, and 18 in a counterclockwise direction. Since the slot pitch angle is 160°, the electrical angle between each slot and its adjacent slot is 160°. The motor windings are divided into three-phase double-layer concentrated windings, with a phase shift angle of 20° between each set of windings. Each stator tooth is wound with a coil.

[0007] The technical solution of the method of the present invention includes the following steps:

[0008] Step 1: The stator tooth (5) is split into two modulation teeth (6) by slotting, keeping the pitch angle between the modulation teeth unequal to the slotting angle (α≠α0). Calculate the air gap magnetic flux density when the permanent magnet (2) is excited alone. The magnetic flux density is obtained as follows:

[0009] ;

[0010] In the formula, F r (θ,t) represents the permanent magnet magnetomotive force, Λ(θ) represents the air gap permeability, θ represents the rotor rotation angle, and F i Let ω be the amplitude of the i-th permanent magnet magnetomotive force harmonic component. r Λ is the mechanical speed of the rotor. jZLet j be the amplitude of the magnetic permeability harmonic component. The order and frequency of the working harmonic are determined by using the calculation formula for the air gap magnetic flux density when the permanent magnet (2) is excited alone.

[0011] Step 2: Adjust the width of the stator teeth (5), the width and height of the modulation teeth (6), the thickness of the stator yoke, and the thickness of the rotor yoke so that the back EMF of the motor reaches its maximum value when the motor magnetic field is not saturated.

[0012] Step 3: By adjusting the structural parameters of the permanent magnet (2), when the motor is not saturated, the permanent magnet structural parameters corresponding to the maximum back EMF amplitude of the motor are calculated using finite element software. The main permanent magnet structural parameters are: permanent magnet pole arc coefficient, permanent magnet thickness, and number of permanent magnet segments. When optimizing the permanent magnet structural parameters, ensure that the slot width and armature winding slot width are the same.

[0013] Step 4: Determine the winding phase shift angle. Derive the torque for the three-phase three-set windings with different phase shift angles to reduce torque pulsation. Determine the phase shift space angle between the three sets of windings to be 20°.

[0014] After adopting the above design scheme, the present invention can achieve the following beneficial effects:

[0015] 1. This invention is based on the principle of magnetic field modulation. By designing the modulation tooth structure and introducing a multi-working-wave design method, the armature winding can fully absorb the permanent magnet magnetic field harmonics. The multi-working-wave design method effectively improves the motor output torque.

[0016] 2. The permanent magnet of this invention employs both radial and circumferential segmentation, which effectively reduces harmonic eddy current losses within the permanent magnet, thereby significantly reducing motor temperature rise and improving motor operational stability. Reasonable selection of the number of axial and circumferential segments also helps reduce the cost of the permanent magnet.

[0017] 3. This invention adopts a three-phase concentrated winding design, with a phase shift angle of 20° between each set of windings. This effectively reduces motor torque ripple, suppresses noise during motor operation, and the increased number of spatial phases gives the motor good fault-tolerant operation potential. Simultaneously, the concentrated winding effectively reduces end length, lowers copper losses, reduces winding complexity, and improves manufacturing manufacturability. Attached Figure Description

[0018] Figure 1 This is an enlarged schematic diagram of the radial cross-section of the present invention;

[0019] Figure 2 This is a schematic diagram of the modulation pole dimensions;

[0020] Figure 3 This is a schematic diagram of the permanent magnet segmentation.

[0021] Figure 4 (a) is a structural diagram of the armature winding; (b) is a schematic diagram of the installation and connection method of the armature winding.

[0022] Figure 5 Comparison of the harmonic spectrum distribution of the permanent magnet magnetomotive force of the three-phase split-tooth permanent magnet vernier motor designed for this invention and the traditional permanent magnet vernier motor;

[0023] Figure 6 A comparison diagram of losses between the three-phase split-tooth permanent magnet vernier motor designed for this invention and a traditional permanent magnet vernier motor;

[0024] Figure 7 A comparison diagram of the torque waveforms of the three-phase split-tooth permanent magnet vernier motor designed in this invention and the traditional permanent magnet vernier motor;

[0025] In the diagram: 1. Rotor; 2. Permanent magnet; 3. Armature winding; 4. Stator; 5. Stator teeth; 6. Modulation teeth; 7. Non-magnetic shaft. Detailed Implementation

[0026] To make the objectives, technical solutions, and effects of the present invention clearer, the structural features and beneficial effects of the motor of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] like Figure 1 This is a three-phase external rotor permanent magnet vernier motor. In the radial direction, from the inside to the outside, there are stators (4), permanent magnets (2), and rotors (1), with an air gap between the stator and the external rotor. The stator (4) adopts a split-tooth structure, with each armature tooth split into two modulation teeth (6). The armature winding (3) is located between the stator teeth and adopts a three-phase concentrated winding. The permanent magnet (2) adopts a segmented design in both the axial and circumferential directions. It is surface-mounted on the inner side of the rotor core and the magnetization direction is radial magnetization with N poles and S poles arranged alternately. The stator core and rotor core are made of magnetic materials such as silicon steel sheets, and the permanent magnet (2) is made of neodymium iron boron material.

[0028] The stator teeth (5) are split into two modulation teeth (6) by slotting, keeping the pitch angle between the modulation teeth unequal to the slotting angle (α≠α0). The air gap magnetic flux density when the permanent magnet (2) is excited alone is calculated. The magnetic flux density is obtained by the following method:

[0029] ;

[0030] In the formula, F r (θ,t) represents the permanent magnet magnetomotive force, Λ(θ) represents the air gap permeability, θ represents the rotor rotation angle, and F i Let ω be the amplitude of the i-th permanent magnet magnetomotive force harmonic component. rΛ is the mechanical speed of the rotor. jZ Let j be the amplitude of the magnetic permeability harmonic component. The order and frequency of the working harmonic are determined by using the calculation formula for the air gap magnetic flux density when the permanent magnet (2) is excited alone.

[0031] Adjust the width of the stator teeth (5), the width and height of the modulation teeth (6), the thickness of the stator yoke, and the thickness of the rotor yoke so that the back EMF of the motor reaches its maximum value when the motor magnetic field is not saturated.

[0032] By adjusting the structural parameters of the permanent magnet (2), when the motor is not saturated, the permanent magnet structural parameters corresponding to the maximum back EMF amplitude of the motor are determined by finite element software simulation. The main permanent magnet structural parameters are: permanent magnet pole arc coefficient, permanent magnet thickness, and number of permanent magnet segments. When optimizing the permanent magnet structural parameters, the slot width and armature winding slot width are the same.

[0033] The phase shift angle of the windings was determined, and the torque of the three-phase three-set windings with different phase shift angles was derived. With the aim of reducing torque pulsation, the phase shift space angle between the three sets of windings was determined to be 20°.

[0034] When the back electromotive force is symmetrical and there are no even-order harmonics, the expression for the back electromotive force of each winding is:

[0035] (1);

[0036] in, For the first Winding and the first Phase shift angle between winding currents Indicates the harmonic order. Let h be the amplitude of the back EMF of the h-th harmonic. Let be the phase angle of the h-th back EMF harmonic in phase A.

[0037] For three sets of three-phase windings, each set of windings is symmetrical and has the same number of turns, and the current flowing through it is an ideal sinusoidal current, then:

[0038] (2);

[0039] The torque generated by the first winding is:

[0040] (3);

[0041] The total electromagnetic torque generated by the three windings is determined as follows:

[0042] (4);

[0043] Where υ is the torque harmonic order, T υThis represents the amplitude of the υth torque harmonic.

[0044] For a three-phase motor supplied with an ideal sinusoidal current, only when h ± 1 = 2ml (l = 1, 2, 3…) is satisfied will the h-th harmonic back electromotive force generate torque pulsation. The torque harmonic component is 6l, and the 6th harmonic is the lowest order of the torque harmonics. The amplitude of the harmonic decreases as the harmonic order increases.

[0045] (5);

[0046] To eliminate the 6th harmonic, γ = 20° is chosen, at which torque ripple can be minimized. Furthermore, the fundamental winding coefficient reaches its maximum value at this point, effectively increasing the motor's torque density.

[0047] By adopting the above design scheme, more working magnetic permeability and magnetic flux density harmonics can be introduced. Figure 5 This significantly improves the motor's output torque and reduces torque ripple. Figure 6 In addition, it can effectively reduce motor losses and improve motor efficiency. Figure 7 ).

[0048] In summary, this invention discloses a design method for a three-phase split-tooth permanent magnet vernier motor. Utilizing the principle of magnetic field modulation, a multi-wave design is adopted for the stator modulation poles of the motor, which can introduce more working magnetic permeability and magnetic flux density harmonics, thereby improving the motor's back electromotive force and output torque. The permanent magnet is designed with axial and circumferential segmentation, which effectively reduces eddy current losses and facilitates installation and manufacturing. Furthermore, the structural parameters of the motor are rationally optimized, improving magnetic field utilization and allowing the motor's performance to be fully realized. The armature winding adopts a three-phase design, which increases the motor's torque output and reduces torque ripple; the increased number of spatial phases also gives the motor good fault-tolerant operation potential. In conclusion, this invention's motor, while possessing the low-speed, high-torque output characteristics of traditional permanent magnet vernier motors, overcomes the disadvantages of high eddy current losses and large torque ripple in permanent magnets. That is, this motor features high torque density, low ripple, high reliability, and high efficiency.

Claims

1. A design method of a three-triple-split-tooth permanent-magnet Vernier motor, characterized by: The motor comprises, from inside to outside, a stator (4), a permanent magnet (2), and a rotor (1), and an air gap is left between the stator (4) and the rotor (1); The stator adopts a split tooth structure and comprises 18 stator teeth (5), each of which is split into two modulation teeth (6), and an armature winding (3) is placed between the teeth, and the armature winding (3) adopts a three-three-phase concentrated winding; wherein the stator core and the rotor core adopt silicon steel sheet magnetic conductive material, and the permanent magnet (2) adopts neodymium iron boron material; According to the number of modulation poles N st and the number of permanent magnet pole pairs P r Determine the number of armature winding pole pairs P s , meet P s =|N st -P r |=|36-28|=8, the number of modulation poles N st =2Z=36; The stator tooth (5) is split into two modulation teeth (6) through slotting, and the pitch angle α between the modulation teeth is not equal to the slotting angle α0; The permanent magnet (2) adopts an axial and circumferential segmented design, the permanent magnet (2) is radially magnetized, and adjacent permanent magnets (2) are magnetized in opposite directions; The design method comprises the following steps: Step 1: split the stator tooth (5) into two modulation teeth (6) through slotting, keep the pitch angle between the modulation teeth not equal to the slotting angle, and calculate the air gap magnetic flux density when the permanent magnet (2) is excited alone, the magnetic flux density is obtained according to the following method: ； where F r is the permanent magnet magnetic motive force, Λ(θ) is the air-gap permeance, θ is the rotor rotation position angle, F i is the amplitude of the i-th permanent magnet magnetic motive force harmonic component, ω r is the mechanical rotation speed of the rotor, Λ jZ is the amplitude of the j-th permeance harmonic component, and Z is the slot number of the motor. The order and frequency of the working harmonic are determined by calculating the air-gap flux density when the permanent magnet (2) is excited alone. Step 2: adjust the width of the stator tooth (5), the width and height of the modulation tooth (6), the thickness of the stator yoke, and the thickness of the rotor yoke, so that the motor back electromotive force reaches the maximum value when the motor magnetic field does not reach saturation; Step 3: adjust the permanent magnet (2) structure parameters, use finite element software simulation when the motor magnetic field does not reach saturation, determine the corresponding permanent magnet structure parameters when the motor back electromotive force amplitude is maximum, and the permanent magnet structure parameters are: permanent magnet pole arc coefficient, permanent magnet thickness, and permanent magnet segmentation number; Step 4: determine the winding phase shift angle, deduce the torque of three-three-phase three sets of windings with different phase shift angles, and determine the phase shift angle between the three sets of windings as 20° for the purpose of reducing torque ripple.

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