A numerical simulation method for electromagnetic vibration of permanent magnet synchronous motor

Abstract

The purpose of the present invention is to provide a numerical simulation research method for electromagnetic vibration of a permanent magnet synchronous motor, comprising the following steps: establishing a mechanical model and an electromagnetic model of a permanent magnet synchronous motor; pre-processing the mechanical model and the electromagnetic model; calculating the spatial and temporal distribution of radial and tangential magnetic flux density of the air gap by the electromagnetic model; calculating the spatial and temporal distribution of radial electromagnetic force; correcting the mechanical finite element model; loading electromagnetic force to the mechanical finite element model of the permanent magnet synchronous motor; performing transient response calculation on the mechanical model to obtain vibration response results. The present invention can study the electromagnetic distribution and mechanical characteristics of the permanent magnet synchronous motor through numerical simulation, and then can accurately and efficiently calculate the electromagnetic vibration characteristics of the permanent magnet synchronous motor, which is used to guide the actual design and production of low-noise permanent magnet synchronous motors.

Description

Technical Field

[0001] The invention relates to a method for electromagnetic vibration reduction and noise reduction of a permanent magnet synchronous motor, in particular to a method for predicting and suppressing electromagnetic vibration of a permanent magnet synchronous motor. Background Art

[0002] Permanent magnet synchronous motors have many significant advantages. Their structure is relatively simple and their operation is more reliable. In addition, the motors can be flexibly designed according to the use environment. Therefore, permanent magnet motors are widely used in cutting-edge industries such as the defense industry.

[0003] The vibration frequency range of the motor that people are concerned about is usually 0-1000Hz, while the noise frequency is above 1000Hz. The vibration noise of the motor can be divided into the following three categories: (1) Electromagnetic vibration noise. The excitation source of electromagnetic vibration is the electromagnetic force wave in the air gap, which is generated by the interaction of magnetic flux density (generated by permanent magnets and stator windings). The transmission path of electromagnetic vibration is: stator core-stator housing-base, and finally the vibration is transmitted to the base through the base, and the noise radiates outward through the housing. If the radial force is close to or equal to the natural frequency of the stator-base system, resonance will occur, which will cause deformation of the motor stator system and generate vibration and acoustic noise. Electromagnetic vibration noise is mainly related to factors that are difficult to completely avoid, such as high-order spatial and temporal harmonics, eccentricity, phase imbalance, slot opening, magnetic saturation, and magnetostrictive deformation of the core laminations. (2) Mechanical vibration noise, which is mainly related to factors such as bearing type, bearing defects, shaft diameter ovality, bearing contact surface, shaft bending, rotor imbalance, shaft misalignment, couplings, universal joints and gears. (3) Aerodynamic vibration noise, which is mainly generated by fans. Any obstacles in the air flow path will generate noise.

[0004] The electromagnetic vibration of the permanent magnet synchronous motor is a major cause of motor noise radiation. At the same time, experiments show that by optimizing the electromagnetic design of the motor, the air gap magnetic flux density and the electromagnetic force wave waveform can be optimized, which can effectively reduce the vibration and noise level of the motor. Therefore, in order to effectively reduce the vibration and noise values ​​of the permanent magnet synchronous motor, it is necessary to conduct in-depth research on the distribution of magnetic flux density and electromagnetic force waves in the permanent magnet motor, which not only reveals the inherent theoretical factors that cause motor vibration, but also provides a direction for suppressing the vibration and noise of the permanent magnet motor in engineering.

[0005] Currently, there is little research on the vibration characteristics of permanent magnet synchronous motors, and there is a lack of vibration optimization design to reduce the vibration level. Therefore, numerical simulation of the electromagnetic vibration of permanent magnet synchronous motors is of great significance, which can better study the electromagnetic vibration characteristics of permanent magnet synchronous motors under various working conditions and provide technical support for vibration prediction and vibration optimization. Summary of the invention

[0006] The purpose of the present invention is to provide a numerical simulation research method for electromagnetic vibration of a permanent magnet synchronous motor, which can reduce the limitations of vibration research through experiments, and can predict and optimize the vibration of the permanent magnet synchronous motor based on numerical methods, so as to guide the design and production of actual low-vibration permanent magnet synchronous motors.

[0007] The object of the present invention is achieved in that:

[0008] The present invention provides a numerical simulation research method for electromagnetic vibration of a permanent magnet synchronous motor, which is characterized by:

[0009] (1) Establish the mechanical model and electromagnetic model of permanent magnet synchronous motor;

[0010] (2) Pre-process the mechanical model and the electromagnetic model, divide the mechanical model and the electromagnetic model into grids, assign boundary conditions and connection parameters that reflect the actual situation, assign electromagnetic parameters, and verify the grid independence;

[0011] (3) Calculating the spatiotemporal distribution of radial and tangential magnetic flux in the air gap by using the electromagnetic model, presetting the magnetic flux extraction path, presetting the magnetic flux decomposition formula by using the field equation, and extracting the radial and tangential magnetic flux on the path from the calculation results;

[0012] (4) Apply the Maxwell stress tensor method to calculate the spatial and temporal distribution of radial electromagnetic force;

[0013] (5) Correction of mechanical finite element model based on modal test of permanent magnet synchronous motor;

[0014] (6) Loading electromagnetic force to the mechanical finite element model of the permanent magnet synchronous motor, writing an APDL command flow to load the result calculated in step (4) to the corresponding position on the mechanical finite element model to achieve unidirectional coupling;

[0015] (7) Perform transient response calculations on the mechanical model, obtain vibration response results, and post-process the response results.

[0016] The present invention may also include:

[0017] 1. In step (1), a three-dimensional mechanical model and a two-dimensional electromagnetic model are established for the same motor.

[0018] 2. In step (2), in the mesh division, the meshes of the air gap and tooth area are encrypted.

[0019] 3. Step (4) The radial electromagnetic force is calculated from the magnetic flux density using the Maxwell stress tensor method. The calculation formula is as follows:

[0020]

[0021] Where μ0 is the vacuum magnetic permeability, μ0=4π×10-7 H / m; B r (θ,t) is the radial magnetic flux density; B n (θ, t) is the tangential magnetic flux density; θ is the spatial angle, unit is rad; t is the time, unit is s.

[0022] 4. In step (5), a three-dimensional CAD model of the entire motor is established. By meshing the geometric body, the pre-processed finite element model is imported into the structural finite element software for modal analysis. The finite element model is then corrected based on the experimental modal results, including the connection conditions between the various components of the motor and the internal and external boundary conditions of the entire machine installation state.

[0023] 5. In step (6), the electromagnetic force wave is loaded radially along the inner surface of the stator using the function loading method, and the nodes of the loading force are only selected from the first layer of nodes on the inner surface;

[0024] For the real electromagnetic force wave, it can be regarded as the superposition of single-order single-frequency force waves with different frequencies. The loading function corresponding to the real electromagnetic force wave is:

[0025]

[0026] Where f0 is the electromagnetic force wave of a certain order; F n is the amplitude of a certain order electromagnetic force wave; ω n is the frequency of the electromagnetic force wave; i n is the order of electromagnetic force wave; θ is the angle; is the phase of the electromagnetic force wave.

[0027] The advantages of the present invention are: the electromagnetic distribution and mechanical characteristics of the permanent magnet synchronous motor can be studied through numerical simulation, and then the electromagnetic vibration characteristics of the permanent magnet synchronous motor can be accurately and efficiently calculated to guide the actual design and production of low-noise permanent magnet synchronous motors. For example, in numerical simulation, by modifying the parameters such as the stator core stiffness, thickness and stator housing stiffness, thickness, motor air gap length, winding distribution, permanent magnet shape, etc., a new solution is provided for vibration reduction and noise reduction optimization design, without the need to process the physical object for testing, thereby reducing the development cycle and cost, and saving a lot of manpower and material resources. In addition, the numerical simulation method of the present invention can also obtain: the back electromotive force of the permanent magnet synchronous motor, the magnetic field distribution, the motor performance parameters, the inherent characteristics of the motor, the time domain and frequency domain vibration response of the permanent magnet synchronous motor, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a flow chart of the present invention;

[0029] Figure 2a is the mechanical equivalent model, Figure 2b It is an electromagnetic model;

[0030] Figure 3 Schematic diagram of the spatial and temporal distribution of radial electromagnetic force;

[0031] Figure 4 Schematic diagram of electromagnetic force loaded on the mechanical model at a certain moment. DETAILED DESCRIPTION

[0032] The present invention is described in more detail below with reference to the accompanying drawings:

[0033] Combination Figure 1-4 , the present invention specifically comprises the following steps:

[0034] Step 1: Establishment of the mechanical model and electromagnetic model of the permanent magnet synchronous motor (establishing a three-dimensional mechanical model and a two-dimensional electromagnetic model for the same motor);

[0035] During the establishment of the mechanical model, the basic framework needs to be established strictly according to the drawings, and some structures that have little effect on vibration can be simplified or equivalent to other components. During the establishment of the electromagnetic model, since the magnetic field of the permanent magnet synchronous motor is considered to be axially constant, and the calculation amount of the three-dimensional electromagnetic model is much greater than that of the two-dimensional electromagnetic model, the electromagnetic model of the present invention is a two-dimensional model.

[0036] Step 2: Pre-processing of the mechanical model and the electromagnetic model (dividing the mechanical model and the electromagnetic model into grids respectively, assigning boundary conditions and connection parameters that reflect the actual situation, assigning accurate electromagnetic parameters, and verifying grid independence);

[0037] In the numerical model, the boundary conditions and connection parameters determine the accuracy of the calculation results. The present invention takes into account the setting of different boundary conditions and connection parameters under engineering practice. In the pre-processing process of the mechanical model and the electromagnetic model, the division of the mechanical grid and the electromagnetic grid has a great influence on the convergence and accuracy of the subsequent numerical calculation, especially the grid encryption process in the length direction of the air gap area in the electromagnetic grid division has a great influence on the numerical simulation of the electromagnetic force, and for the mechanical model, the mesh encryption of the tooth part of the loading force has a great influence on the vibration response calculation. The present invention takes into account the different requirements for mesh encryption of different air gap lengths and tooth areas, and encrypts the meshes of the air gap and tooth areas according to the parameters selected for the numerical simulation.

[0038] Step 3: Calculate the spatiotemporal distribution of radial and tangential magnetic flux in the air gap by electromagnetic model (preset magnetic flux extraction path, preset magnetic flux decomposition formula through field equation, extract radial and tangential magnetic flux on the path from calculation results);

[0039] When calculating the magnetic field of a permanent magnet synchronous motor through an electromagnetic model, it is necessary to preset a magnetic flux extraction path in the area of ​​interest. In addition, there are no direct radial and tangential magnetic flux results in the electromagnetic calculation results, so the magnetic flux needs to be decomposed into radial and tangential in the field calculator.

[0040] Step 4: Use the Maxwell stress tensor method to calculate the spatiotemporal distribution of the radial electromagnetic force (preset the calculation formula of the radial electromagnetic force through the field equation);

[0041] The radial electromagnetic force can be calculated from the magnetic flux density by using the Maxwell stress tensor method. The calculation formula is as follows:

[0042]

[0043] Where μ0 is the vacuum magnetic permeability, μ0=4π×10 -7 H / m; B r (θ,t) is the radial magnetic flux density; B n (θ, t) is the tangential magnetic flux density; θ is the spatial angle, unit is rad; t is the time, unit is s.

[0044] Since the radial electromagnetic force result cannot be directly obtained from the two-dimensional electromagnetic calculation results, it is necessary to obtain the radial electromagnetic force result by calculating the magnetic density in the field calculator. The obtained radial electromagnetic force is a function of time and space angle.

[0045] Step 5: Correct the mechanical finite element model based on the modal test of the permanent magnet synchronous motor (correct the mechanical finite element model to improve the calculation accuracy);

[0046] The transmission path of motor vibration is affected by the motor topology, installation status, material properties, etc. Due to the uncertainty of material properties and installation status, the model needs to be modified many times and the test data needs to be corrected during finite element simulation. Therefore, the calculation process requires multiple iterations and continuous corrections. The basic idea is as follows: First, establish the overall three-dimensional CAD model of the motor, use the meshing of the geometric body, import the pre-processed finite element model into the structural finite element software for modal analysis, and then correct the finite element model through the test modal results, mainly correcting the connection between the various components of the motor, the installation status of the whole machine and other internal and external boundary conditions. Because the inherent characteristics of the structure are mainly its natural vibration frequency and vibration mode, the test modal results are used to correct the finite element model from these two aspects. Because the stator and rotor of the motor are the most critical parts in modal analysis, both parts are meshed with high-quality meshes.

[0047] Step 6: Load the electromagnetic force onto the mechanical finite element model of the permanent magnet synchronous motor (write an APDL command flow to load the result calculated in step 4 onto the corresponding position on the mechanical finite element model to achieve unidirectional magneto-solid coupling);

[0048] Taking into account both computing resources and accuracy, this paper ignores the changes of electromagnetic force waves along the axial direction of the motor, and assumes that the force on the inner surface of the motor stator does not change with the change of the axial length. In order to accurately simulate the real state of electromagnetic force waves acting on the stator, this paper uses the function loading method to load the electromagnetic force waves along the radial direction of the inner surface of the stator. Since the real electromagnetic force wave is an interface force, the nodes of the loading force are only selected on the first layer of nodes on the inner surface.

[0049] For the real electromagnetic force wave, it can be regarded as the superposition of many single-order and single-frequency force waves with different frequencies. The loading function corresponding to the real electromagnetic force wave is:

[0050]

[0051] Where f0 is the electromagnetic force wave of a certain order; F n is the amplitude of a certain order electromagnetic force wave; ω n is the frequency of the electromagnetic force wave; i n is the order of electromagnetic force wave; θ is the angle; is the phase of the electromagnetic force wave.

[0052] During the transient analysis, the electromagnetic force wave loading at a certain moment is as follows: Figure 4 shown.

[0053] Step 7: Perform transient response calculation on the mechanical model to obtain vibration response results (perform transient calculation on the mechanical finite element model to obtain transient calculation results of vibration response).

[0054] The electromagnetic force selects the stable stage of the finite element simulation calculation. The transient response calculation time length is the same as the total duration of the electromagnetic force loading. The stable stage of the vibration response is taken as the transient response result. The calculated vibration response is subjected to Fourier transform to obtain the motor vibration response spectrum under different operating conditions.

Claims

1. A numerical simulation research method for electromagnetic vibration of a permanent magnet synchronous motor, characterized by: (1) Establish a mechanical model and an electromagnetic model of a permanent magnet synchronous motor, and establish a three-dimensional mechanical model and a two-dimensional electromagnetic model for the same motor; (2) Pre-process the mechanical model and the electromagnetic model, divide the mechanical model and the electromagnetic model into grids, assign boundary conditions and connection parameters that reflect the actual situation, assign electromagnetic parameters, and verify the grid independence; (3) Calculating the spatiotemporal distribution of radial and tangential magnetic flux in the air gap by using the electromagnetic model, presetting the magnetic flux extraction path, presetting the magnetic flux decomposition formula by using the field equation, and extracting the radial and tangential magnetic flux on the path from the calculation results; (4) Apply the Maxwell stress tensor method to calculate the spatial and temporal distribution of radial electromagnetic force; (5) Correction of mechanical finite element model based on modal test of permanent magnet synchronous motor; Establish the overall 3D CAD model of the motor, divide the geometric body into meshes, import the pre-processed finite element model into the structural finite element software for modal analysis, and then modify the finite element model based on the test modal results, including modifying the connection between the motor components and the internal and external boundary conditions of the whole machine installation state; (6) Loading electromagnetic force to the mechanical finite element model of the permanent magnet synchronous motor, writing an APDL command flow to load the result calculated in step (4) to the corresponding position on the mechanical finite element model to achieve unidirectional coupling; The electromagnetic force wave is loaded along the radial direction of the inner surface of the stator using the function loading method, and the nodes of the loading force are only selected from the first layer of nodes on the inner surface; For the real electromagnetic force wave, it can be regarded as the superposition of single-order single-frequency force waves with different frequencies. The loading function corresponding to the real electromagnetic force wave is: Where f0 is the electromagnetic force wave of a certain order; F n is the amplitude of a certain order electromagnetic force wave; ω n is the frequency of the electromagnetic force wave; i n is the order of electromagnetic force wave; θ is the angle; is the phase of electromagnetic force wave; t is time; (7) Perform transient response calculations on the mechanical model, obtain vibration response results, and post-process the response results.

2. The method for numerical simulation of electromagnetic vibration of a permanent magnet synchronous motor according to claim 1 is characterized in that: In step (2) of dividing the mesh, the meshes of the air gap and tooth area are encrypted.

3. The method for numerical simulation of electromagnetic vibration of a permanent magnet synchronous motor according to claim 1 is characterized by: Step (4) uses the Maxwell stress tensor method to calculate the radial electromagnetic force from the magnetic flux density. The calculation formula is as follows: Where μ0 is the vacuum magnetic permeability, μ0=4π×10 -7 H / m; B r (θ,t) is the radial magnetic flux density; B n (θ, t) is the tangential magnetic flux density; θ is the spatial angle, unit is rad; t is the time, unit is s.

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