An evaluation method for transformer core joints considering noise impact

Abstract

A method for evaluating transformer core joints that considers noise impacts first establishes a correspondence between the core size proportionality coefficient and the core joint method with the lowest sound pressure level. The core size proportionality coefficient of the transformer to be evaluated is then calculated and substituted into the established correspondence to determine the core joint method with the lowest sound pressure level for the transformer to be evaluated. By establishing a correspondence between the core size proportionality coefficient and the core joint method with the lowest sound pressure level, this design provides a reference for subsequent transformer joint selection. This minimizes transformer noise while meeting transformer performance requirements, effectively reducing operating and maintenance costs and extending the transformer's service life.

Description

Technical Field

[0001] The invention belongs to the technical field of transformer design, and in particular relates to an evaluation method for transformer core joint modes taking noise influence into consideration. Background Art

[0002] In recent years, large transformers have been increasingly used in residential and public places, and the noise problem of transformers has attracted more and more attention. Certain requirements have been put forward for the noise impact of large transformers and small and medium-sized transformers. Transformer noise suppression has become an urgent problem that needs to be solved in the transformer manufacturing industry and related industries.

[0003] When the transformer's rated operating flux density is within the range of 1.5-1.8T, the noise of dry-type transformers primarily comes from core vibration caused by magnetostriction of the silicon steel sheets. Currently, research on core structure noise reduction focuses primarily on adding side yokes and changing core size. Research on transformer joint methods is limited to the fact that adding beveled joints improves the transformer's magnetic properties and reduces noise. This means that adding beveled joints to a core will improve magnetic properties while also changing its structural characteristics, which in turn affects the noise ultimately generated by the transformer. However, there is a lack of relevant standards and evaluation methods for selecting transformer core joint methods to reduce transformer noise, making it difficult to effectively control transformer noise. Summary of the Invention

[0004] The purpose of the present invention is to overcome the above problems existing in the prior art and provide a method for evaluating transformer core joints that can effectively control transformer noise and takes into account the influence of noise.

[0005] To achieve the above objectives, the present invention provides the following technical solutions:

[0006] A method for evaluating transformer core joints considering noise influence is provided, wherein the evaluation method is performed in the following steps:

[0007] S1. Establish the corresponding relationship between the core size proportional coefficient and the core joint method with the minimum sound pressure level;

[0008] S2. Calculate the core size proportionality coefficient of the transformer to be evaluated, and substitute it into the corresponding relationship established in step S1 to determine the core joint method with the minimum sound pressure level of the transformer to be evaluated.

[0009] Step S1 is performed in the following steps:

[0010] S11, establish multiple transformer three-dimensional simulation models according to different joint modes of the transformer core, and set the core size ratio coefficients in the multiple transformer three-dimensional simulation models to K P，C ;

[0011] S12, performing electromagnetic simulation calculations on multiple three-dimensional transformer simulation models respectively;

[0012] S13, adding solid mechanics analysis to the electromagnetic simulation calculation results obtained in step S12;

[0013] S14, adding acoustic field analysis to the solid mechanics analysis results obtained in step S13;

[0014] S15, according to the sound field analysis result obtained in step S14, a transformer three-dimensional simulation model with the minimum sound pressure level is selected, and the core joint mode of the transformer three-dimensional simulation model is used as the transformer core size relationship proportional coefficient K. P，C The corresponding core joint method with the minimum sound pressure level.

[0015] The core size relationship proportional coefficient K P，C Calculated according to the following formula:

[0016]

[0017] In the above formula, d is the diameter of the core column and the iron yoke, the diameter of the core column is equal to the diameter of the iron yoke, h is the window height of the core, and b is the window width of the core.

[0018] The step S11 specifically includes: modeling the transformer according to different joint methods of the transformer core in Comsol finite element simulation software to obtain multiple three-dimensional transformer simulation models, wherein the transformer core is composed of multiple stacked silicon steel sheets, the joint gap material of the core is set to air, and the transformer shell and clamping parts are ignored during modeling.

[0019] In step S12, the electromagnetic simulation calculation is specifically as follows: the required voltage is added to the multiple three-dimensional simulation models of the transformer respectively, and then the electromagnetic simulation calculation is performed according to the equation of the transformer core in the electromagnetic field, with the magnetic field curl on the core surface being 0 as the boundary condition, and the magnetic field intensity distribution on the surface of the transformer core is obtained by solving, wherein the equation of the transformer core in the electromagnetic field is:

[0020]

[0021] In the above formula, is the Hamiltonian operator, μ is the magnetic permeability, A is the magnetic displacement vector, J e is the external current density, σ is the conductivity, and v1 is the velocity of the charged particles inside the iron core;

[0022] The boundary condition for the core surface magnetic field curl to be 0 is:

[0023] n×H=0-

[0024] In the above formula, n is the normal vector of the core surface, and H is the magnetic field intensity.

[0025] In step S13, the solid mechanics analysis specifically includes: fixing the bottom surface of the transformer core to a constraint, bidirectionally coupling the electromagnetic field on the surface of the transformer core with solid mechanics through magnetostriction, and calculating the force distribution on the surface of the transformer core after deformation due to magnetostrictive force in the alternating electromagnetic field according to the following equation:

[0026]

[0027] In the above formula, [M] is the mass matrix, [C] is the damping matrix, [K] is the stiffness matrix, {F(t)} is the function that changes with time, is the acceleration vector, is the velocity vector and {u} is the node displacement.

[0028] In step S14, the sound field analysis is specifically as follows: first, the core surface vibration velocity is obtained according to the core surface force distribution obtained in step S13, and then the core surface vibration velocity is used as the vibration velocity of the air around the core. The sound field analysis is performed according to the momentum equation of the vibration velocity of the air around the core and the sound pressure intensity of the core in the air, and the acoustic wave equation of the sound wave generated by the core vibration in the air. The core surface vibration velocity is used as the sound field boundary condition to solve the transformer sound pressure level distribution, wherein the momentum equation of the core surface particle vibration velocity and the core sound pressure intensity in the air is:

[0029]

[0030] In the above formula, v2 is the vibration velocity of the air around the iron core, and ρ is the air density;

[0031] The acoustic wave equation of the sound wave generated by the vibration of the iron core in the air is:

[0032]

[0033] In the above formula, p is the sound pressure of the iron core in the air, is the Laplace operator, and c0 is the speed of sound waves in air.

[0034] In step S11, the core size ratio coefficient K P，C It is 0.20-0.45.

[0035] In step S11, the seaming methods include straight seams, half-straight and half-oblique seams, and full-oblique seams.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] In a method for evaluating transformer core joints that considers noise impact, the present invention first establishes a corresponding relationship between a core size proportional coefficient and the core joint method with the lowest sound pressure level. The core size proportional coefficient of the transformer to be evaluated is then calculated and substituted into the established corresponding relationship to determine the core joint method with the lowest sound pressure level for the transformer to be evaluated. By establishing the corresponding relationship between the core size proportional coefficient and the core joint method with the lowest sound pressure level, the design provides a reference for subsequent selection of transformer joint methods, thereby controlling transformer noise within a minimum range while meeting transformer performance requirements, thereby better reducing operating and maintenance costs and extending the service life of the transformer. Therefore, the present invention can effectively control transformer noise while meeting transformer performance requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Flowchart of the present invention.

[0039] Figure 2 1 is an experimental circuit diagram used in the experimental verification of the embodiment.

[0040] Figure 3 Schematic diagram of the distribution of 12 points in the experimental verification of the embodiment.

[0041] Figure 4 This is a diagram of a three-dimensional simulation model of a transformer constructed according to direct seam in the simulation verification of the embodiment.

[0042] Figure 5 This is a three-dimensional simulation model diagram of a transformer built with half-straight and half-oblique joints in the simulation verification of the embodiment.

[0043] Figure 6 This is a diagram of a three-dimensional simulation model of a transformer built with full oblique joints in the simulation verification of the embodiment.

[0044] Figure 7 It is a cloud diagram of the magnetic field intensity distribution on the surface of the core under different joint modes obtained through simulation calculation in the simulation verification of the embodiment.

[0045] Figure 8 It is a cloud diagram of transformer stress distribution under different joint modes obtained through simulation calculation in the simulation verification of the embodiment.

[0046] Figure 9 The figure is a cloud diagram of the sound pressure level distribution around the transformer under different joint modes obtained through simulation calculation in the simulation verification of the embodiment. DETAILED DESCRIPTION

[0047] The present invention will be further described below with reference to the accompanying drawings and specific implementation methods.

[0048] See also Figure 1 A method for evaluating transformer core joints considering noise influence is provided, wherein the evaluation method is performed in the following steps:

[0049] S1. Establish the corresponding relationship between the core size proportional coefficient and the core joint method with the minimum sound pressure level;

[0050] S2. Calculate the core size proportionality coefficient of the transformer to be evaluated, and substitute it into the corresponding relationship established in step S1 to determine the core joint method with the minimum sound pressure level of the transformer to be evaluated.

[0051] Step S1 is performed in the following steps:

[0052] S11, establish multiple transformer three-dimensional simulation models according to different joint modes of the transformer core, and set the core size ratio coefficients in the multiple transformer three-dimensional simulation models to K P,C ;

[0053] S12, performing electromagnetic simulation calculations on multiple three-dimensional transformer simulation models respectively;

[0054] S13, adding solid mechanics analysis to the electromagnetic simulation calculation results obtained in step S12;

[0055] S14, adding acoustic field analysis to the solid mechanics analysis results obtained in step S13;

[0056] S15, according to the sound field analysis result obtained in step S14, a transformer three-dimensional simulation model with the minimum sound pressure level is selected, and the core joint mode of the transformer three-dimensional simulation model is used as the transformer core size relationship proportional coefficient K. P，C The corresponding core joint method with the minimum sound pressure level.

[0057] The core size relationship proportional coefficient K P，C Calculated according to the following formula:

[0058]

[0059] In the above formula, d is the diameter of the core column and the iron yoke, the diameter of the core column is equal to the diameter of the iron yoke, h is the window height of the core, and b is the window width of the core.

[0060] The step S11 specifically includes: modeling the transformer according to different joint methods of the transformer core in Comsol finite element simulation software to obtain multiple three-dimensional transformer simulation models, wherein the transformer core is composed of multiple stacked silicon steel sheets, the joint gap material of the core is set to air, and the transformer shell and clamping parts are ignored during modeling.

[0061] In step S12, the electromagnetic simulation calculation is specifically as follows: the required voltage is added to the multiple three-dimensional simulation models of the transformer respectively, and then the electromagnetic simulation calculation is performed according to the equation of the transformer core in the electromagnetic field, with the magnetic field curl on the core surface being 0 as the boundary condition, and the magnetic field intensity distribution on the surface of the transformer core is obtained by solving, wherein the equation of the transformer core in the electromagnetic field is:

[0062]

[0063] In the above formula, is the Hamiltonian operator, μ is the magnetic permeability, A is the magnetic displacement vector, J e is the external current density, σ is the conductivity, and v1 is the velocity of the charged particles inside the iron core;

[0064] The boundary condition for the core surface magnetic field curl to be 0 is:

[0065] n×H=0 -

[0066] In the above formula, n is the normal vector of the core surface, and H is the magnetic field intensity.

[0067] In step S13, the solid mechanics analysis specifically includes: fixing the bottom surface of the transformer core to a constraint, bidirectionally coupling the electromagnetic field on the surface of the transformer core with solid mechanics through magnetostriction, and calculating the force distribution on the surface of the transformer core after deformation due to magnetostrictive force in the alternating electromagnetic field according to the following equation:

[0068]

[0069] In the above formula, [M] is the mass matrix, [C] is the damping matrix, [K] is the stiffness matrix, {F(t)} is the function that changes with time, is the acceleration vector, is the velocity vector and {u} is the node displacement.

[0070] In step S14, the sound field analysis is specifically as follows: first, the core surface vibration velocity is obtained according to the core surface force distribution obtained in step S13, and then the core surface vibration velocity is used as the vibration velocity of the air around the core. The sound field analysis is performed according to the momentum equation of the vibration velocity of the air around the core and the sound pressure intensity of the core in the air, and the acoustic wave equation of the sound wave generated by the core vibration in the air. The core surface vibration velocity is used as the sound field boundary condition to solve the transformer sound pressure level distribution, wherein the momentum equation of the core surface particle vibration velocity and the core sound pressure intensity in the air is:

[0071]

[0072] In the above formula, v2 is the vibration velocity of the air around the iron core, and ρ is the air density;

[0073] The acoustic wave equation of the sound wave generated by the vibration of the iron core in the air is:

[0074]

[0075] In the above formula, p is the sound pressure of the iron core in the air, is the Laplace operator, and c0 is the speed of sound waves in air.

[0076] In step S11, the core size ratio coefficient K P，C It is 0.20-0.45.

[0077] In step S11, the seaming methods include straight seams, half-straight and half-oblique seams, and full-oblique seams.

[0078] Example:

[0079] See also Figure 1 A method for evaluating transformer core joints considering noise impact is proposed. Three transformers are used as evaluation objects. The specific steps are as follows:

[0080] S1. Establish the corresponding relationship between the core size proportional coefficient and the core joint method with the minimum sound pressure level

[0081] S11. Establish multiple transformer 3D simulation models based on different joint methods of the transformer core

[0082] In the Comsol finite element simulation software, the transformer is modeled according to the transformer core direct seam, semi-straight semi-oblique seam, and full oblique seam, and three transformer three-dimensional simulation models are obtained. The core size relationship proportional coefficients in the three transformer three-dimensional simulation models are all set to K P，C , K P，C The transformer core is composed of a plurality of stacked silicon steel sheets. The joint gap material is set to air. The transformer housing and clamping parts are ignored during modeling.

[0083] S12. Perform electromagnetic simulation calculations on multiple transformer three-dimensional simulation models

[0084] The required voltages were added to the three transformer 3D simulation models. Then, electromagnetic simulation calculations were performed based on the equations for the transformer core in the electromagnetic field. The magnetic field intensity distribution on the surface of the transformer core was obtained using the boundary condition of 0 magnetic field curl on the core surface. The equation for the transformer core in the electromagnetic field is:

[0085]

[0086] In the above formula, is the Hamiltonian operator, μ is the magnetic permeability, A is the magnetic displacement vector, J e is the external current density, σ is the conductivity, and v1 is the velocity of the charged particles inside the iron core;

[0087] The boundary condition for the core surface magnetic field curl to be 0 is:

[0088] n×H=0 -

[0089] In the above formula, n is the normal vector of the core surface, and H is the magnetic field intensity.

[0090] S13, adding solid mechanics analysis to the electromagnetic simulation calculation results obtained in step S12

[0091] In the fixed constraint boundary condition of solid mechanics in the Comsol finite element simulation software, the bottom surface of the core is selected and fixedly constrained. The electromagnetic field on the surface of the transformer core is bidirectionally coupled with the solid mechanics through magnetostriction. The force distribution on the surface of the transformer core after deformation due to magnetostrictive force in the alternating electromagnetic field is calculated according to the following equation:

[0092]

[0093] In the above formula, [M] is the mass matrix, [C] is the damping matrix, [K] is the stiffness matrix, {F(t)} is the function that changes with time, is the acceleration vector, is the velocity vector, {u} is the node displacement;

[0094] S14: Adding acoustic field analysis to the solid mechanics analysis results obtained in step S13

[0095] First, the core surface vibration velocity is obtained based on the force distribution on the core surface obtained in step S13. Then, the core surface vibration velocity is used as the vibration velocity of the air around the core. According to the momentum equation of the vibration velocity of the air around the core and the sound pressure intensity of the core in the air, and the acoustic wave equation of the sound wave generated by the core vibration in the air, the sound field analysis is performed. The core surface vibration velocity is used as the sound field boundary condition to solve the sound pressure level distribution around the transformer. The momentum equation of the core surface particle vibration velocity and the sound pressure intensity of the core in the air is:

[0096]

[0097] In the above formula, v2 is the vibration velocity of the air around the iron core, and ρ is the air density;

[0098] The acoustic wave equation of the sound wave generated by the vibration of the iron core in the air is:

[0099]

[0100] In the above formula, p is the sound pressure of the iron core in the air, is the Laplace operator, c0 is the propagation speed of sound waves in air;

[0101] S15, according to the sound field analysis result obtained in step S14, a transformer three-dimensional simulation model with the minimum sound pressure level is selected, and the core joint mode of the transformer three-dimensional simulation model is used as the transformer core size relationship proportional coefficient K. P，C The corresponding core joint method with the minimum sound pressure level;

[0102] The corresponding relationship between the core size ratio coefficient and the core joint method with the minimum sound pressure level is finally established through the dichotomy method: when 0.2≤K P，C When 0.32 is less than K, the transformer core adopts half straight and half oblique joints to have the minimum sound pressure level. P，C When the transformer core adopts full oblique joints, the minimum sound pressure level is achieved. P，C When it is 0.32, the sound pressure level of the transformer core with half straight and half oblique joints is equal to the sound pressure level of the transformer core with full oblique joints, and both are lower than the sound pressure level of the transformer core with straight joints.

[0103] S2. Calculate the core size proportional coefficient K of the transformer to be evaluated according to the following formula: P，C is 0.214:

[0104]

[0105] In the above formula, d is the diameter of the core leg and the iron yoke, the diameter of the core leg is equal to the diameter of the iron yoke, h is the window height of the core, and b is the window width of the core;

[0106] Since the core size of the transformer to be evaluated has a proportional coefficient of 0.2≤K P,C <0.32. According to the corresponding relationship established in step S1, it can be known that the transformer to be evaluated has the minimum sound pressure level when using a half-straight and half-oblique joint.

[0107] Verification

[0108] In order to verify the accuracy of the evaluation results in the embodiment, the following tests were performed:

[0109] 1. Experimental verification

[0110] The transformer with different joint modes (core size ratio coefficient K P,C is 0.214) access as Figure 2In the experimental circuit shown, after inputting the required voltage, 12 points with the same distance from the transformer core are selected. The distribution of the 12 points is shown in Figure 3 The sound pressure levels at 12 points were measured by a decibel meter and the average value was taken for verification. The average sound pressure levels of the transformers under different joint methods are shown in Table 1:

[0111] Table 1 Measurement results of average transformer sound pressure level under different joint modes

[0112] Seaming method Sound pressure level / dB Direct seam 50.2 Half straight half bevel seam 45.4 Fully beveled seams 48.6

[0113] As shown in Table 1, when the transformer core size ratio coefficient K P,C When the value is 0.214, the sound pressure level of the semi-straight and semi-oblique joint is the lowest.

[0114] 2. Simulation Verification

[0115] According to step S1 in the embodiment, simulation verification is performed, wherein the three-dimensional simulation model of the transformer is established according to the straight seam, semi-straight semi-oblique seam, and full oblique seam (the core size ratio coefficient K P,C is 0.214) respectively as Figure 4-6 As shown in the figure, through simulation calculation, the magnetic field intensity distribution cloud diagram of the core surface under different joint modes is obtained when the core column located in the middle of the core is at the maximum moment (see Figure 7 , from left to right are direct seam, semi-straight and semi-oblique seam, full oblique seam), transformer stress distribution cloud diagram under different seam methods (see Figure 8 , from left to right are direct seam, semi-straight and semi-oblique seam, full oblique seam), the sound pressure level distribution cloud diagram around the transformer under different seam methods (see Figure 9 , from left to right are straight seam, half straight and half oblique seam, full oblique seam), let the center point on the core column in the middle of the core be point X, the magnetic induction intensity, force, and sound pressure level at point X are shown in Table 2:

[0116] Table 2 Magnetic induction intensity, force and sound pressure level at point X under different joint methods

[0117] Seaming method Magnetic induction intensity / T Stress / MPa Sound pressure level / dB Direct seam 1.46 4.20 49.4 Half straight half bevel seam 1.62 4.34 45.1 Fully mitered seams 1.72 5.13 47.7

[0118] Combine Figure 9 As shown in Table 2, when the transformer core size ratio coefficient K P,C When the value is 0.214, the sound pressure level of the semi-straight and semi-oblique joint is the lowest.

[0119] In summary, the correspondence between the core size proportional coefficient and the core joint method with the minimum sound pressure level established by the evaluation method of the present invention can provide a reference basis for the subsequent selection of transformer joint methods, and the evaluation accuracy is good.

Claims

1. A method for evaluating transformer core joints considering noise impact, characterized by: The evaluation method is carried out in the following steps: S1. Establish the corresponding relationship between the core size proportional coefficient and the core joint method with the minimum sound pressure level; S2. Calculate the core size proportionality coefficient of the transformer to be evaluated, and substitute it into the corresponding relationship established in step S1 to determine the core joint method that minimizes the sound pressure level of the transformer to be evaluated; Step S1 is performed in the following steps: S11, according to the different joint modes of the iron core in the transformer, multiple three-dimensional transformer simulation models are established, and the core size relationship ratio coefficients in the multiple three-dimensional transformer simulation models are all set to ; S12, performing electromagnetic simulation calculations on multiple three-dimensional transformer simulation models respectively; S13, adding solid mechanics analysis to the electromagnetic simulation calculation results obtained in step S12; S14, adding acoustic field analysis to the solid mechanics analysis results obtained in step S13; S15, according to the sound field analysis result obtained in step S14, a transformer three-dimensional simulation model with the minimum sound pressure level is selected, and the core joint mode of the transformer three-dimensional simulation model is used as the transformer core size relationship proportional coefficient. The corresponding core joint method with the minimum sound pressure level; The core size relationship proportional coefficient Calculated according to the following formula: ； In the above formula, is the diameter of the core column and the iron yoke. The diameter of the core column is equal to the diameter of the iron yoke. is the window height of the core, is the window width of the core.

2. The method for evaluating transformer core joints considering noise impact according to claim 1, characterized in that: The step S11 specifically includes: modeling the transformer according to different joint methods of the transformer core in Comsol finite element simulation software to obtain multiple three-dimensional transformer simulation models, wherein the transformer core is composed of multiple stacked silicon steel sheets, the joint gap material of the core is set to air, and the transformer shell and clamping parts are ignored during modeling.

3. The method for evaluating transformer core joints considering noise impact according to claim 2, characterized in that: In step S12, the electromagnetic simulation calculation is specifically as follows: the required voltage is added to the multiple three-dimensional simulation models of the transformer respectively, and then the electromagnetic simulation calculation is performed according to the equation of the transformer core in the electromagnetic field, with the magnetic field curl on the core surface being 0 as the boundary condition, and the magnetic field intensity distribution on the surface of the transformer core is obtained by solving, wherein the equation of the transformer core in the electromagnetic field is: ； In the above formula, is the Hamiltonian operator, is the magnetic permeability, is the magnetic displacement vector, is the external current density, is the conductivity, is the speed of the charged particles inside the iron core; The boundary condition for the core surface magnetic field curl to be 0 is: ； In the above formula, is the normal vector of the core surface, is the magnetic field strength.

4. The method for evaluating transformer core joints considering noise impact according to claim 3, characterized in that: In step S13, the solid mechanics analysis specifically includes: fixing the bottom surface of the transformer core to a constraint, bidirectionally coupling the electromagnetic field on the surface of the transformer core with solid mechanics through magnetostriction, and calculating the force distribution on the surface of the transformer core after deformation due to magnetostrictive force in the alternating electromagnetic field according to the following equation: ； In the above formula, is the mass matrix, is the damping matrix, is the stiffness matrix, is a function that changes with time, is the acceleration vector, is the velocity vector, is the node displacement.

5. The method for evaluating transformer core joints considering noise impact according to claim 4, characterized in that: In step S14, the sound field analysis is specifically as follows: first, the core surface vibration velocity is obtained according to the core surface force distribution obtained in step S13, and then the core surface vibration velocity is used as the vibration velocity of the air around the core. The sound field analysis is performed according to the momentum equation of the vibration velocity of the air around the core and the sound pressure intensity of the core in the air, and the acoustic wave equation of the sound wave generated by the core vibration in the air. The core surface vibration velocity is used as the sound field boundary condition to solve the transformer sound pressure level distribution, wherein the momentum equation of the core surface particle vibration velocity and the core sound pressure intensity in the air is: ； In the above formula, is the vibration speed of the air around the core, is the air density; The acoustic wave equation of the sound wave generated by the vibration of the iron core in the air is: ； In the above formula, is the sound pressure of the iron core in the air, is the Laplace operator, is the speed of sound waves in air.

6. The method for evaluating transformer core joints considering noise impact according to claim 1, characterized in that: In step S11, the core size ratio coefficient It is 0.20-0.

45.

7. The method for evaluating transformer core joints considering noise impact according to claim 1, characterized in that: In step S11, the seaming methods include straight seams, half-straight and half-oblique seams, and full-oblique seams.

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