Electromagnetic design method of special large-gap permanent magnet synchronous motor for pumps

Abstract

The present invention relates to the technical field of motor design methods, specifically an electromagnetic design method for a special large-gap permanent magnet synchronous motor for pumps. By obtaining the theoretical calculated values ​​and simulation values ​​of the air gap magnetic flux density and input power under different air gaps, the performance of the motor under different air gap conditions can be fully and carefully understood. On this basis, the correction coefficient is calculated, and then the original design parameters are corrected, and finally the motor is designed and manufactured according to the corrected parameters. This design method combines the simulation technology and the idea of ​​parameter correction, and can accurately optimize the impact of air gap changes on motor performance. It effectively solves the problem of motor performance degradation that may be caused by air gap adjustment, significantly improves key performance indicators such as motor efficiency and power factor, makes the motor more stable and efficient during operation, and meets the diverse needs of motor performance in different application scenarios.

Description

Technical Field

[0001] The present invention relates to the technical field of motor design methods, in particular to an electromagnetic design method of a special large-gap permanent magnet synchronous motor for a pump. Background Art

[0002] The size of the air gap is crucial to the design of permanent magnet synchronous motors. Changes in the air gap directly affect the magnetic resistance, leading to changes in a series of electromagnetic parameters including magnetic density and magnetic flux, thereby affecting the motor performance.

[0003] Conventional permanent magnet synchronous motors mainly have small air gaps. In some special application scenarios, large air gap requirements are put forward for the motors: in complex underwater working environments, large air gap motors can reduce the requirements for processing accuracy and allow a certain offset in wheelbase; in the collaborative link of industrial robots, large air gap motors can reduce the magnetic attraction between the stator and rotor and reduce the cogging torque; in low-noise scenarios such as medical equipment, large air gap motors can reduce noise; in working environments with high requirements for thermal management, large air gap motors can arrange cooling channels in the air gap space to increase heat dissipation and reduce the operating temperature of the motor.

[0004] However, increasing the air gap can negatively impact motor performance. For example, increasing the air gap increases the air gap reluctance, which in turn reduces the air gap flux density. This reduced air gap flux density reduces the magnetic flux, which in turn affects the back EMF. Therefore, after changing the motor's air gap, it is necessary to optimize the motor's structural parameters and various performance parameters, such as the size of the permanent magnets, stator, and rotor. However, current designs for permanent magnet synchronous motors with adjustable air gaps are lacking, and further research is needed to optimize these motors. Summary of the Invention

[0005] To avoid and overcome the technical problems existing in the prior art, the present invention provides an electromagnetic design method for a special large-gap permanent magnet synchronous motor for pumps. By obtaining the corresponding air gap correction coefficient, the present invention can optimize the permanent magnet synchronous motor after adjusting the air gap, thereby improving the motor's performance.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] The electromagnetic design method of a special large-gap permanent magnet synchronous motor for pumps includes the following design steps:

[0008] S1. Establish a motor simulation model based on the original design parameters of the permanent magnet synchronous motor;

[0009] S2. Calculate the theoretical calculated values ​​of the air gap magnetic flux density and the theoretical calculated values ​​of the input power of the motor under different air gaps, and simultaneously obtain the theoretical simulated values ​​of the air gap magnetic flux density and the theoretical simulated values ​​of the input power under the same conditions through the motor simulation model;

[0010] S3. Calculate the air gap flux density correction coefficient based on the theoretical calculation value and simulation value of the air gap flux density; and simultaneously calculate the input power correction coefficient based on the theoretical calculation value and simulation value of the input power;

[0011] S4. Correct the original design parameters using the air gap flux correction factor and the input power correction factor to obtain corrected design parameters, and use the corrected design parameters to design and manufacture the permanent magnet synchronous motor.

[0012] As a further solution of the present invention, the steps for establishing the motor simulation model are as follows:

[0013] S11. Select the corresponding electromagnetic simulation software;

[0014] S12. Input the parameters required for constructing the motor into the electromagnetic simulation software to construct a three-dimensional motor simulation model.

[0015] As a further solution of the present invention: the sub-steps of step S2 are as follows:

[0016] S21. Calculate theoretical air gap magnetic flux density values ​​at different air gaps using a calculation formula for theoretical air gap magnetic flux density, and simultaneously calculate theoretical input power values ​​at different air gaps using a calculation formula for theoretical input power density.

[0017] S22. Using a control variable method and performing grid division on the motor simulation model, the motor simulation model is optimized by means of grid optimization, and the theoretical simulation values ​​of the air gap magnetic flux density and the theoretical simulation values ​​of the input power under different air gaps are obtained by simulating the optimized motor simulation model.

[0018] As a further solution of the present invention: the calculation formula of the theoretical calculation value of the air gap magnetic density is as follows:

[0019] (1);

[0020] (2);

[0021] Where, Indicates air gap magnetic density; represents the original permanent magnet thickness; Indicates residual magnetism; Represents relative magnetic permeability; Indicates the motor air gap; Indicates magnetic load; Represents the magnetic flux leakage coefficient.

[0022] As a further solution of the present invention: the calculation formula of the theoretical calculated value of the input power is as follows:

[0023] (3);

[0024] Where, Indicates input power; Indicates rated power; Indicates the power loss of the rotor iron ring; Copper power loss of the coil; Indicates other power losses.

[0025] As a further solution of the present invention: the sub-steps of step S3 are as follows:

[0026] S31. Compare the theoretical simulation value of the air gap magnetic density with the theoretical calculated value of the air gap magnetic density, and the ratio is the air gap magnetic density correction coefficient; at the same time, compare the theoretical simulation value of the input power with the theoretical calculated value of the input power, and the ratio is the input power correction coefficient;

[0027] S32. Obtain the air gap magnetic flux correction coefficient and input power correction coefficient under different air gaps according to the content of step S31;

[0028] S33. Taking the air gap as the independent variable, and the air gap magnetic flux correction coefficient and the input power correction coefficient as the dependent variables, respectively, an exponential air gap magnetic flux correction coefficient calculation formula and an input power correction coefficient calculation formula are established through the data obtained in step S32.

[0029] As a further solution of the present invention: air gap flux correction coefficient The calculation formula is as follows, and the air gap magnetic flux correction coefficient is applicable to the air gap of 0.5mm-1.5mm:

[0030] (4);

[0031] Where, Represents a natural constant.

[0032] As a further solution of the present invention: input power correction factor The calculation formula is as follows:

[0033] (5);

[0034] Where, represents the sine function, Represents pi.

[0035] As a further solution of the present invention: the calculation formulas of the original design parameters are as follows:

[0036] (6);

[0037] Where, represents the original armature diameter; Indicates the calculation of polar arc coefficient; Indicates the motor winding coefficient; Indicates the air gap magnetic field waveform coefficient; Indicates the rated speed of the motor; It represents the ratio between the armature length and the armature diameter; Indicates the estimated line load; Indicates magnetic load;

[0038] (7);

[0039] Where, represents the original stator outer diameter; represents the stator crack ratio;

[0040] (8);

[0041] Where, represents the original armature length;

[0042] (9);

[0043] Where, represents the original rotor outer diameter;

[0044] (10);

[0045] Where, represents the original pole distance; represents the number of pole pairs;

[0046] (11);

[0047] Where, represents the original per-pole flux, represents the average magnetic flux density;

[0048] (12);

[0049] Where, represents the original total full-load flux;

[0050] (13);

[0051] Where, represents the original back electromotive force; Indicates the current frequency; Indicates the number of coil turns.

[0052] As a further solution of the present invention: the calculation formulas of each modified design parameter are as follows:

[0053] (14);

[0054] Where, Indicates the corrected armature diameter;

[0055] (15);

[0056] Where, Indicates the corrected stator outer diameter;

[0057] (16);

[0058] Where, Indicates the corrected armature length;

[0059] (17);

[0060] Where, Indicates the corrected permanent magnet thickness;

[0061] (18);

[0062] Where, Indicates the corrected rotor outer diameter;

[0063] (19);

[0064] Where, Indicates the corrected pole distance;

[0065] (20);

[0066] Where, Indicates the corrected flux per pole;

[0067] (twenty one);

[0068] Where, Indicates the corrected total full-load flux;

[0069] (twenty two);

[0070] Where, Indicates the corrected back electromotive force.

[0071] Compared with the prior art, the present invention has the following beneficial effects:

[0072] 1. The present invention can fully and meticulously understand the performance of the motor under different air gap conditions by obtaining the theoretical calculated values ​​and simulated values ​​of the air gap flux density and input power under different air gaps. On this basis, the correction coefficient is calculated, and then the original design parameters are corrected, and finally the motor is designed and manufactured according to the corrected parameters. This design method breaks the traditional design pattern and is no longer limited to a single theoretical calculation or empirical design. Instead, it combines simulation technology and parameter correction ideas, and can accurately optimize the impact of air gap changes on motor performance. It effectively solves the problem of motor performance degradation that may be caused by air gap adjustment, significantly improves key performance indicators such as motor efficiency and power factor, makes the motor more stable and efficient during operation, and meets the diverse demands for motor performance in different application scenarios.

[0073] 2. The calculation formula of the air gap magnetic flux correction coefficient cleverly uses the natural constant " " and motor air gap" ” and other key parameters, establishing a close connection between the air gap flux correction coefficient and these parameters in the form of an exponential function. In practical applications, simply substituting the motor's air gap value into this formula can accurately calculate the air gap flux correction coefficient. This coefficient plays a vital role in motor design. It can accurately adjust the deviation between the theoretical calculated air gap flux density and the actual demand, ensuring a more reasonable magnetic field distribution in the motor, reducing magnetic losses, and improving the motor's electromagnetic conversion efficiency, thereby enhancing the motor's overall performance.

[0074] 3. The input power correction coefficient calculation formula uses the sine function , and combined with the motor air gap Parameters such as , accurately reflect the inherent relationship between the input power correction factor and the motor's air gap. During motor operation, changes in the air gap directly affect the motor's input power characteristics. This formula accurately calculates the corresponding input power correction factor based on the real-time changes in the air gap. This allows designers to adjust the motor's input power based on the calculation results, avoiding problems such as motor overheating and inefficiency caused by improper input power. Precisely controlling input power not only improves motor efficiency and reduces energy consumption, but also extends the motor's lifespan and enhances its adaptability and stability under different operating conditions.

[0075] 4. The calculation formulas for each corrected design parameter cover multiple key motor design parameters such as the corrected armature diameter, corrected stator outer diameter, and corrected armature length, and each formula comprehensively considers multiple factors such as the correction coefficient, calculated pole arc coefficient, motor winding coefficient, and air gap magnetic field waveform coefficient. This comprehensive consideration ensures that each corrected design parameter can accurately reflect the actual needs of the motor after air gap correction. For designers, these formulas are like a detailed operating guide, providing an accurate calculation basis for each link in motor design. Whether in the preliminary design stage of the motor or in the later performance optimization process, designers can use these formulas, combined with the actual motor operating requirements and working conditions, to accurately adjust the various design parameters, thereby designing a permanent magnet synchronous motor with better performance and more in line with actual application needs.

[0076] 5. The formula for the theoretical calculation of the air gap flux density is based on inherent motor parameters such as the original permanent magnet thickness. Through reasonable mathematical derivation, it can accurately calculate the theoretical value of the air gap flux density of the motor under ideal conditions. The formula for the theoretical calculation of input power comprehensively considers multiple aspects such as rated power, rotor iron ring power loss, coil copper power loss, and other power losses, and can accurately calculate the theoretical input power required by the motor during operation. These theoretical calculation values ​​are an important basis for the subsequent calculation of the air gap flux density correction factor and the input power correction factor. Their accuracy directly affects the reliability and effectiveness of the entire design method. Only when the theoretical calculation values ​​are accurate can the rationality of the correction coefficient be guaranteed, thereby achieving precise correction of motor design parameters and effective improvement of motor performance.

[0077] 6. The calculation formula for the original design parameters clarifies the calculation method for the original design parameters of the motor, such as the original armature diameter, the original stator outer diameter, and the original armature length, providing motor designers with unified standards and specifications in the early stages of the project. In the field of motor design, standardized calculation formulas are crucial. They ensure that different designers can operate based on the same theoretical basis and calculation methods when designing motors, avoiding design differences and errors caused by inconsistent calculation methods. At the same time, these formulas are highly versatile and applicable to the initial design of permanent magnet synchronous motors of various types and specifications. Whether it is a small household appliance motor or a large industrial drive motor, designers can use these formulas, combined with specific motor performance requirements and application scenarios, to calculate reasonable original design parameters, laying a solid foundation for subsequent design optimization work. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] Figure 1 It is a flow chart of the design method steps of the present invention.

[0079] Figure 2This is a curve diagram of the change of the air gap magnetic flux correction coefficient in the present invention.

[0080] Figure 3 This is a curve diagram of the change of the input power correction coefficient in the present invention.

[0081] Figure 4 This is a curve diagram of the motor working efficiency change under the original design parameters of the present invention.

[0082] Figure 5 This is a curve diagram of the motor working efficiency change under the modified design parameters in the present invention. DETAILED DESCRIPTION

[0083] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0084] See also Figures 1 to 3 , the specific contents of the embodiment of the present invention are as follows:

[0085] 1. Establishing a motor simulation model

[0086] 1. Clarify design goals and basic parameters

[0087] Core requirements are determined based on the application scenario (e.g., pump motors): The motor must accommodate large gaps (e.g., 0.5mm-1.5mm) to reduce machining precision, magnetic attraction and noise, and optimize heat dissipation. The design targets a 200W permanent magnet synchronous motor, as shown in Table 1. Its rated parameters, including rated power, speed, current, and pole pair number, form the basis for subsequent design.

[0088] Table 1 Rated parameters of permanent magnet synchronous motor

[0089] ;

[0090] 2. Calculate the original design parameters

[0091] Parameter definition: Input power , the specific value is obtained through calculation or simulation. Calculate the polar arc coefficient , generally takes 0.65-0.85, in this embodiment the value is 0.85. , generally takes a value of 0.85-0.97, and in this embodiment takes a value of 0.866. Air gap magnetic field waveform coefficient , generally takes a value of 0.9-1.15, and in this embodiment takes a value of 0.9. The ratio between the armature length and the armature diameter , in this embodiment, the value is 1.2. Estimated line load , generally 3-10A / mm, in this embodiment the value is 10A / mm. In this embodiment, the calculated value is 0.9917T according to the simulation results. , generally takes a value of 0.57±0.015, and in this embodiment takes a value of 0.56. , in this embodiment, the value is 1.05. , generally takes a value of 1.05-1.5, and in this embodiment takes a value of 1.5. According to the material properties, the remanence of the material in this embodiment is 1.23T. , in this embodiment, the value is 3. The specific value is determined by the simulation results. Current frequency f , in this embodiment, the value is 150Hz. , in this embodiment, the value is 134. Average magnetic flux density In this embodiment, the value is determined according to the simulation results.

[0092] According to the electromagnetic design theory of the motor, based on the rated parameters given in Table 1 and the above parameter values, the corresponding formulas in formulas (1) to (22) and relevant motor knowledge are used to preliminarily calculate the original design parameters of the motor before simulation, including the stator outer diameter, inner diameter, rotor inner diameter, outer diameter, armature length, permanent magnet size, tooth slot size, etc. Then, combining the rated parameters and original design parameters of the motor, a motor simulation model is established in the simulation software.

[0093] 3. Build a motor simulation model

[0094] Use professional electromagnetic simulation software (such as Maxwell or Ansys) to input rated parameters and original design parameters to create a 3D or 2D simulation model. The model must include key components such as the stator, rotor, permanent magnets, and air gap, and set material properties (such as silicon steel sheet magnetic permeability and permanent magnet remanence) and boundary conditions (such as winding current and speed). The specific steps are as follows:

[0095] 1) Preliminary preparation: clarify goals and parameters

[0096] (1) Define simulation objectives

[0097] Determine the analysis type: Eddy current field.

[0098] Clarify the output indicators: air gap magnetic flux density and input power.

[0099] (2) Sort out input parameters

[0100] Electrical parameters: rated voltage / current, frequency, power, material electromagnetic parameters (magnetic permeability, electrical conductivity, remanence, etc.).

[0101] Structural parameters: geometric dimensions (length, width, height of components, air space range), material distribution (silicon steel, copper, permanent magnet position).

[0102] Excitation conditions: voltage / current source type, amplitude, phase, boundary conditions (symmetry plane, natural boundary, radiation boundary).

[0103] (3) Select software and dimensions

[0104] Software selection: (Ansys HFSS is preferred).

[0105] Maxwell: Low-frequency scenarios (motors, transformers), supporting multi-physics coupling.

[0106] Ansys HFSS: Accurately calculate radiation and scattering in high-frequency scenarios (antennas, RF components).

[0107] Dimension selection: (preferably 3D).

[0108] 2D: The structure is symmetrical (such as an axially infinitely long motor), and the calculation efficiency is high.

[0109] 3D: Complex asymmetric structures (such as three-dimensional magnetic circuits, antenna spatial radiation), high precision.

[0110] 2) Modeling execution: from geometry to materials

[0111] (1) Geometric modeling

[0112] Self-built model:

[0113] Use built-in tools to draw 2D cross-sections (such as rectangles and circles) or 3D solids (extrude, revolve, and use Boolean operations). Motor modeling requires drawing stator slots, rotor permanent magnets, and air gaps; antenna modeling requires precisely drawing the shape of metal arms.

[0114] Importing external models:

[0115] Import STEP / IGES files, check units (mm / m) and simplify geometry (remove non-critical features such as chamfers, threads, etc.).

[0116] (2) Assigning material properties

[0117] Call the material library: directly select preset materials such as silicon steel (such as 35W250), copper, air, etc.

[0118] Custom Material: Enter the conductivity ( σ ), relative magnetic permeability ( μ r)、Remanence density( B r ), coercive force ( H c ) and other parameters, the permanent magnet needs to define the magnetizing direction.

[0119] (3) Setting boundaries and incentives

[0120] Boundary conditions:

[0121] Natural boundary / radiation boundary: simulate infinite space (low frequency / high frequency scenario).

[0122] Symmetrical boundary: Reduces the amount of calculation (such as taking a 1 / 2 pole model of the motor and setting the symmetric plane of the antenna).

[0123] PEC / PMC: Ideal electric / magnetic conductor boundary (commonly used in high-frequency simulations).

[0124] Incentive Type:

[0125] DC / low frequency: current source (DC / sinusoidal AC current), voltage source, permanent magnet magnetization excitation.

[0126] High frequency: wave port / lumped port excitation, set characteristic impedance (such as 50Ω) and number of modes.

[0127] 3) Simulation Settings: Mesh and Solver

[0128] (1) Grid division

[0129] Automatic meshing: The software automatically generates meshes based on geometric curvature (suitable for simple models).

[0130] Manual Control:

[0131] Refine the mesh in critical areas (air gap, windings, permanent magnet surface, antenna edge) to ensure that the mesh size is less than the skin depth.

[0132] For three-dimensional models, hexahedral meshes (higher accuracy) are preferred, while tetrahedral meshes are used for complex structures.

[0133] Mesh Check: Verify minimum mesh quality (e.g. mesh Jacobian > 0.2 in Maxwell).

[0134] (2) Solver and parameter configuration

[0135] Select a solver:

[0136] Static Magnetic Field: Calculates the DC magnetic field distribution (such as the magnetic circuit of a permanent magnet).

[0137] Eddy current field: Analyze eddy current losses under alternating magnetic fields (such as power frequency transformers).

[0138] Transient field: simulate dynamic processes (such as motor starting, pulse excitation).

[0139] High Frequency Mode: In HFSS, select either a terminal solver or a mode solver (depending on the port type).

[0140] Convergence Settings:

[0141] Set the energy error threshold (e.g. <1%), and for transient simulation, define the time step (e.g. 1 / 100 of the electrical cycle) and the termination time.

[0142] High frequency sweep: Set the start / end frequency and step size (e.g. 1-10GHz, step size 0.1GHz).

[0143] 4) Result verification and optimization

[0144] (1) Results analysis

[0145] Field distribution visualization: magnetic flux density ( B ) cloud map, magnetic field vector diagram, electric field strength ( E )distributed.

[0146] Key parameter extraction:

[0147] Low frequency: inductance, Ampere force, iron loss / copper loss, efficiency.

[0148] High frequency: S parameters (such as S 11 return loss), standing wave ratio (VSWR), far-field gain, and directivity.

[0149] (2) Model validation

[0150] Comparison of analytical solutions: For example, the magnetic field of an infinitely long wire and the parallel plate capacitance formulas are compared with simulation results.

[0151] Experimental data comparison: The error between the measured inductance, no-load current, and antenna pattern and the simulation values ​​is controlled within 5%.

[0152] Parameter sensitivity analysis: Scan the air gap length, number of winding turns, and operating frequency to observe performance change trends.

[0153] (3) Optimization iteration

[0154] Use the software parameter sweep (ParametricSweep) to automatically calculate multiple sets of solutions, or set the objective function (such as minimum loss, maximum gain) through the optimization module (such as MaxwellOptimization) to generate the optimal structural parameters to obtain the optimal motor simulation model.

[0155] Unit unification: Confirm the global unit (mm or m) before modeling to avoid deviation in results due to unit errors.

[0156] Air domain settings: For low-frequency models, the air domain must enclose all components (usually 1.5-2 times the physical size). For high-frequency models, a sufficiently large radiation boundary or PML layer must be added.

[0157] Computational resource management: When the 3D model has a large mesh size, computation time can be reduced by reducing the mesh density, using symmetry boundaries, or parallel computing (such as ANSYS distributed solver).

[0158] 2. Perform simulation

[0159] Modifying the air gap of a permanent magnet synchronous motor, using the air gap as the independent variable and the motor's air gap flux density and input power as the dependent variables, the air gap size was varied from 0.5mm to 0.7mm, 0.9mm, 1.1mm, 1.3mm, and 1.5mm, respectively. Simulation analysis was then performed using a motor simulation model. A conventional small air gap motor (0.5mm) was used as a baseline, and the gap was gradually increased to a large one (1.5mm) to cover the actual needs of applications such as pumps.

[0160] According to the air gap reluctance , we know the air gap length After a change, the air gap reluctance is the first to be affected, which in turn affects the air gap flux density, which in turn affects other performance and structural parameters. Therefore, when constructing a new design algorithm, the air gap flux density is the primary factor causing changes in other performance and structural parameters of a permanent magnet synchronous motor after a change in the air gap. Therefore, when determining the correction coefficient, the air gap flux density should be the primary factor to be corrected, as it is the primary factor causing changes in other performance and structural parameters of the permanent magnet synchronous motor after a change in the air gap.

[0161] In the design calculation of motor size structure, in addition to the correction of motor air gap magnetic flux, input power is also a very important parameter, which directly affects the design of stator inner and outer diameters and rotor inner and outer diameters. Therefore, when determining the correction coefficient, the input power is also corrected.

[0162] 3. Obtaining the Correction Factor

[0163] 1. Theoretical calculation of air gap magnetic flux density

[0164] According to the calculation formula of the motor design parameters, the theoretical calculation values ​​of the air gap magnetic density under air gaps of 0.5mm, 0.7mm, 0.9mm, 1.1mm, 1.3mm and 1.5mm are first calculated respectively. Then, through simulation analysis, the simulation values ​​of the air gap magnetic density under air gaps of 0.5mm, 0.7mm, 0.9mm, 1.1mm, 1.3mm and 1.5mm are obtained. According to the simulation values ​​and the theoretical calculation values, the correction coefficient of the air gap magnetic density is determined.

[0165] According to Ohm's law of magnetic circuits, the magnetic flux generated by a permanent magnet must overcome the air gap reluctance. The magnetic flux density is proportional to the thickness of the permanent magnet and inversely proportional to the air gap length. The theoretical calculation formula for the air gap magnetic flux density is shown in Formula (1). Comparing the simulated value with the theoretical value yields the air gap magnetic flux density correction factor, as shown in Table 2.

[0166] Table 2 Air gap magnetic flux correction coefficient

[0167] ;

[0168] The data in Table 2 were used to draw the Figure 2 The air gap flux correction coefficient curve is shown in Figure 1. As can be seen from this figure, as the air gap increases, the air gap flux density gradually decreases. Due to possible inaccuracies in the calculation model and derivation process, the theoretical value differs from the actual air gap flux density variation. The gap between the simulated value and the theoretical value becomes more pronounced as the air gap increases.

[0169] According to the design formula of the motor, the theoretical calculation values ​​of the input power at air gaps of 0.5mm, 0.7mm, 0.9mm, 1.1mm, 1.3mm and 1.5mm are first calculated respectively. Then, the simulation values ​​of the input power at air gaps of 0.5mm, 0.7mm, 0.9mm, 1.1mm, 1.3mm and 1.5mm are obtained through simulation analysis. The correction coefficient of the input power is determined based on the simulation values ​​and the theoretical calculation values.

[0170] The input power correction factor can be obtained by comparing the simulated value with the theoretical value, as shown in Table 3.

[0171] Table 3 Input power correction factor

[0172] ;

[0173] The data in Table 3 were used to draw the Figure 3 The input power correction coefficient curve is shown in Figure 1. As can be seen from this graph, when the air gap length increases slightly, slight magnetic flux leakage occurs and the magnetic field harmonics increase slightly. However, due to the increase in the air gap, the iron loss also decreases, so the input power changes little. As the air gap length increases, severe magnetic flux leakage occurs and the magnetic field harmonics increase significantly. Other losses dominate the loss change, resulting in a significant change in input power.

[0174] 4. Optimizing Permanent Magnet Synchronous Motors

[0175] The original design parameters are corrected using the air gap flux correction coefficient and the input power correction coefficient to obtain the corrected design parameters, and the permanent magnet synchronous motor is designed and manufactured using the corrected design parameters.

[0176] Based on Table 2 and Figure 2The data in Table 3 and the calculation formula of the air gap flux correction coefficient are constructed as shown in formula (4). Figure 3 The data in is used to construct the input power correction coefficient calculation formula shown in formula (5).

[0177] The present invention designs a 200W permanent magnet synchronous motor, and changes the air gap from 0.5mm to 0.7mm, 0.9mm, 1.1mm, 1.3mm and 1.5mm respectively. The simulation values ​​of parameters such as air gap flux density, which mainly affect the performance after the air gap is changed, are obtained, and the values ​​are corrected with the initial theoretical calculated values. A new motor design algorithm is constructed through the correction coefficient, and the following set of correction formulas for permanent magnet synchronous motors under different air gap states are obtained, as shown in formulas (14) to (22).

[0178] Taking the air gap of 0.5 mm as an example, the modified design parameters are shown in Table 4.

[0179] Table 4 Modified design parameters

[0180] ;

[0181] The present invention first constructs a motor simulation model based on the original design parameters, obtains the theoretical calculation values ​​and simulation values ​​of the air gap flux density and input power under different air gaps, and then deduces the corresponding air gap flux density correction coefficient and input power correction coefficient. Through specific formulas, these correction coefficients are used to correct a series of original design parameters such as the armature diameter and stator outer diameter. At the same time, the theoretical calculation value formulas of the air gap flux density and input power and the calculation formulas of the original design parameters provide a theoretical basis and basic support for the entire design process. Finally, a permanent magnet synchronous motor is designed and manufactured based on the corrected design parameters to achieve the purpose of optimizing motor performance.

[0182] In order to more intuitively reflect the degree of optimization of motor performance, some design parameters are selected from the original design parameters for optimization. The selected design parameters and specific values ​​are shown in Table 5.

[0183] Table 5 Original design parameters

[0184] ;

[0185] The data in Table 5 and the specific values ​​of other original design parameters are input into the electromagnetic simulation software Ansys to simulate the working efficiency of the motor. The simulation results are as follows: Figure 4 As shown, Figure 4 The horizontal axis represents the power angle, and the vertical axis represents the motor's operating efficiency. From the simulation results, we can see that under the design parameters, the motor's operating efficiency is 88% when the optimal power angle is 6.14°.

[0186] The optimized values ​​of the design parameters in Table 5 are obtained from Table 4 and input into the electromagnetic simulation software Ansys together with the specific values ​​of other original design parameters to simulate the working efficiency of the motor. The simulation results are as follows: Figure 5 As shown, Figure 5 The horizontal axis represents the power angle, and the vertical axis represents the motor's operating efficiency. The simulation results show that under the revised design parameters, the motor's operating efficiency increases to 90% at an optimal power angle of 6.14°.

[0187] The results show that the motor's operating efficiency increased from 88% to 90%. This 2% improvement may seem small, but it is actually a valuable advancement. This is because in the technical breakthrough of improving motor energy efficiency, every 1% breakthrough requires overcoming multiple technical bottlenecks such as material properties, electromagnetic losses, and structural optimization. This not only means a significant improvement in energy conversion efficiency, but also represents a comprehensive upgrade in terms of energy conservation, consumption reduction, and operational stability.

[0188] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. The electromagnetic design method of a special large-gap permanent magnet synchronous motor for pumps is characterized by: The design steps include: S1. Establish a motor simulation model based on the original design parameters of the permanent magnet synchronous motor; S2. Calculate the theoretical calculated values ​​of the air gap magnetic flux density and the theoretical calculated values ​​of the input power of the motor under different air gaps, and simultaneously obtain the theoretical simulated values ​​of the air gap magnetic flux density and the theoretical simulated values ​​of the input power under the same conditions through the motor simulation model; S3. Calculate the air gap magnetic flux correction coefficient based on the theoretical calculation value and simulation value of the air gap magnetic flux; At the same time, the input power correction coefficient is calculated based on the theoretical calculated value and simulation value of the input power; S4. Correcting the original design parameters using the air gap flux correction factor and the input power correction factor to obtain corrected design parameters, and designing and manufacturing the permanent magnet synchronous motor using the corrected design parameters; The sub-steps of step S3 are as follows: S31. Compare the theoretical simulation value of the air gap magnetic density with the theoretical calculation value of the air gap magnetic density, and the ratio is the air gap magnetic density correction coefficient; at the same time, compare the theoretical simulation value of the input power with the theoretical calculation value of the input power, and the ratio is the input power correction coefficient; the air gap magnetic density correction coefficient The calculation formula is as follows: ； Where, represents a natural constant; Indicates the motor air gap; S32. Obtain the air gap magnetic flux correction coefficient and input power correction coefficient under different air gaps according to the content of step S31; S33, with the air gap as the independent variable, and the air gap magnetic flux correction coefficient and the input power correction coefficient as the dependent variables, respectively, establish an exponential air gap magnetic flux correction coefficient calculation formula and an input power correction coefficient calculation formula through the data obtained in step S32; the input power correction coefficient The calculation formula is as follows: ； Where, represents the sine function, Represents pi.

2. The electromagnetic design method of a special large-gap permanent magnet synchronous motor for a pump according to claim 1, characterized in that: The steps to establish the motor simulation model are as follows: S11. Select the corresponding electromagnetic simulation software; S12. Input the parameters required for constructing the motor into the electromagnetic simulation software to construct a three-dimensional motor simulation model.

3. The electromagnetic design method of a special large-gap permanent magnet synchronous motor for a pump according to claim 2, characterized in that: The sub-steps of step S2 are as follows: S21. Calculate theoretical air gap magnetic flux density values ​​at different air gaps using a calculation formula for theoretical air gap magnetic flux density, and simultaneously calculate theoretical input power values ​​at different air gaps using a calculation formula for theoretical input power density. S22. Using a control variable method and performing grid division on the motor simulation model, the motor simulation model is optimized by means of grid optimization, and the theoretical simulation values ​​of the air gap magnetic flux density and the theoretical simulation values ​​of the input power under different air gaps are obtained by simulating the optimized motor simulation model.

4. The electromagnetic design method of a special large-gap permanent magnet synchronous motor for a pump according to claim 3, characterized in that: The calculation formula of the theoretical value of air gap magnetic density is as follows: ； ； Where, Indicates air gap magnetic density; represents the original permanent magnet thickness; Indicates residual magnetism; Represents relative magnetic permeability; Indicates the motor air gap; Indicates magnetic load; Represents the magnetic flux leakage coefficient.

5. The electromagnetic design method of a special large-gap permanent magnet synchronous motor for a pump according to claim 4, characterized in that: The calculation formula for the theoretical value of input power is as follows: ； Where, Indicates input power; Indicates rated power; Indicates the power loss of the rotor iron ring; Copper power loss of the coil; Indicates other power losses.

6. The electromagnetic design method of a special large-gap permanent magnet synchronous motor for a pump according to claim 5, characterized in that: The calculation formulas for each original design parameter are as follows: ； Where, represents the original armature diameter; Indicates the calculation of polar arc coefficient; Indicates the motor winding coefficient; Indicates the air gap magnetic field waveform coefficient; Indicates the rated speed of the motor; It represents the ratio between the armature length and the armature diameter; Indicates the estimated line load; Indicates magnetic load; ； Where, represents the original stator outer diameter; represents the stator crack ratio; ； Where, represents the original armature length; ； Where, represents the original rotor outer diameter; ； Where, represents the original pole distance; represents the number of pole pairs; ； Where, represents the original per-pole flux, represents the average magnetic flux density; ； Where, represents the original total full-load flux; ； Where, represents the original back electromotive force; Indicates the current frequency; Indicates the number of coil turns.

7. The electromagnetic design method of a special large-gap permanent magnet synchronous motor for a pump according to claim 6, characterized in that: The calculation formulas for each modified design parameter are as follows: ； Where, Indicates the corrected armature diameter; ； Where, Indicates the corrected stator outer diameter; ； Where, Indicates the corrected armature length; ； Where, Indicates the corrected permanent magnet thickness; ； Where, Indicates the corrected rotor outer diameter; ； Where, Indicates the corrected pole distance; ； Where, Indicates the corrected flux per pole; ； Where, Indicates the corrected total full-load flux; ； Where, Indicates the corrected back electromotive force.

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