Permanent magnet motor bearing load reduction design method based on stator eccentricity and permanent magnet synchronous motor

Abstract

The invention belongs to the technical field of motor manufacturing, and particularly relates to a permanent magnet motor bearing load reduction design method based on stator eccentricity and a permanent magnet synchronous motor. The method comprises the following steps: establishing a non-uniform air gap permanent magnet synchronous motor model; performing magnetic field distribution simulation to obtain magnetic flux density and magnetic field intensity distribution data; calculating the magnetic tension distribution of different air gap positions, and evaluating the influence of non-uniformly distributed air gaps on the bearing; the thickness of the non-uniform air gap is adjusted, and the effect of reducing the bearing load is achieved. Through the design of the non-uniform air gaps, the magnetic pulling force can generate a reverse torque in the self-weight direction of the motor, and the torque can effectively counteract the influence of the self-weight of the motor to a certain extent. Therefore, the gravity of the motor and the magnetic pulling force interact with each other, so that the comprehensive influence on the bearing is formed, and the extra load needing to be borne by the bearing is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of motor manufacturing, and in particular relates to a permanent magnet motor bearing load reduction design method based on stator eccentricity and a permanent magnet synchronous motor. Background Art

[0002] Permanent Magnet Synchronous Motor (PMSM) has been widely used in many fields such as industrial automation, robotics, electric vehicles, and aerospace due to its high efficiency, high power density, low noise, and good control performance. In the design of PMSM, the uniformity of the air gap is an important factor affecting the performance of the motor. Traditional motor designs often use uniform air gaps, but in the actual manufacturing process, due to processing errors, improper assembly, or uneven materials, the air gap is often impossible to be completely uniform.

[0003] Uneven air gaps can lead to uneven magnetic field distribution, which in turn causes instability in magnetic pull, and in turn causes unbalanced loads on the bearing shaft. This uneven magnetic pull not only affects the working efficiency of the motor, but also produces periodic mechanical vibration, noise, and bearing wear, which can lead to motor performance degradation or even failure in severe cases. Therefore, it is of great engineering significance to study and optimize the effect of uneven air gaps on the magnetic pull of permanent magnet synchronous motor bearing shafts.

[0004] In the traditional permanent magnet synchronous motor (PMSM) design, a uniform air gap model is usually adopted, in which the air gap thickness between the stator and the rotor is consistent throughout the motor. However, in practical applications, the influence of the motor's own gravity on the bearing shaft cannot be ignored. Under the uniform air gap design, the motor's own weight and load are directly applied to the bearing, resulting in the bearing having to bear a large load. Especially during long-term operation, the continuous load caused by the motor's own gravity may cause bearing wear, vibration, and heat accumulation, which in turn affects the stability and service life of the motor.

[0005] Currently, bearing overload and vibration issues have become a challenge in motor design. In the prior art, research on reducing bearing loads mainly focuses on improving bearing structure or optimizing materials, but there is relatively little research on the design optimization of the motor itself. Traditional designs do not fully utilize the distribution characteristics of the motor's magnetic pull to reduce the bearing burden. Summary of the invention

[0006] The purpose of the present invention is to introduce an uneven air gap design in a permanent magnet synchronous motor and utilize the uneven distribution characteristics of magnetic pulling force to offset the influence of the motor's deadweight on the bearing shaft, thereby reducing the bearing load and improving the stability and operating efficiency of the motor.

[0007] In order to achieve the above-mentioned purpose, the technical solution provided by the present invention is a permanent magnet motor bearing load reduction design method based on stator eccentricity, comprising the following steps: Establish a model of non-uniform air gap permanent magnet synchronous motor; Conduct magnetic field distribution simulation to obtain magnetic flux density and magnetic field intensity distribution data; Calculate the magnetic pull distribution at different air gap positions and evaluate the impact of unevenly distributed air gaps on the bearing shaft; Adjust the thickness of the uneven air gap to reduce the bearing load.

[0008] Preferably, in the uneven air gap permanent magnet synchronous motor model, the air gap thickness between the stator and the rotor in the lower part is unevenly distributed in the axial direction, and the air gap thickness gradually increases from both sides to the middle; the air gap thickness between the stator and the rotor in the upper part is evenly distributed.

[0009] Preferably, the uniformly distributed air gap thickness is less than or equal to a minimum value of the non-uniformly distributed air gap thickness.

[0010] The present invention also provides a non-uniform air gap permanent magnet synchronous motor, in which the air gap thickness between the stator and the rotor in the lower part of the motor is unevenly distributed in the axial direction, and the air gap thickness gradually increases from both sides to the middle; the air gap thickness between the stator and the rotor in the upper part is evenly distributed.

[0011] The present invention can make the magnetic pull generate a reverse torque in the direction of the motor's own weight through the design of the uneven air gap, and this torque can effectively offset the influence of the motor's own gravity to a certain extent. In this way, the motor's gravity and the magnetic pull interact with each other, thereby forming a comprehensive influence on the bearing shaft, reducing the additional load that the bearing shaft needs to bear.

[0012] Specifically, when the air gap is designed with a smaller thickness at the top and a larger thickness at the bottom, the magnetic flux density at the top of the motor is larger, generating a stronger magnetic pull; the magnetic flux density at the bottom of the air gap is smaller, generating a weaker magnetic pull. In this way, through the difference in the distribution of the magnetic pull, the magnetic pull at the top of the motor partially offsets the downward pull of the motor's own weight on the shaft, thereby effectively reducing the load that the bearing needs to bear when the motor is running.

[0013] This design can not only reduce the bearing burden of the motor, reduce bearing wear and vibration, but also significantly extend the service life of the bearing. At the same time, reducing the bearing load also helps to improve the overall stability and operating efficiency of the motor, especially in high-speed, high-load application scenarios. By further optimizing the design of the uneven air gap, the motor can maintain a more balanced stress state during operation, thereby achieving an ideal bearing load reduction effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Schematic diagram of a model of a non-uniform air gap permanent magnet synchronous motor in an embodiment of the present invention; Figure 2 Detailed diagram of the changing uneven air gap; Figure 3 Global analytical model of equivalent surface-mount permanent magnet motor; Figure 4 Schematic diagram of polar coordinate system for establishing analytical model; Figure 5 Radial air gap magnetic flux waveform under uneven air gap; Figure 6 Magnetic pull force simulation distribution waveform. DETAILED DESCRIPTION

[0015] The present invention is further described below in conjunction with specific embodiments and the accompanying drawings. More details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention is obviously capable of being implemented in a variety of other ways different from the description herein. For those skilled in the art, any substitution, improvement or change made to the embodiments of the present invention is within the protection scope of the present invention, and the protection scope of the present invention should not be limited by the content of this specific embodiment.

[0016] The present invention provides a permanent magnet motor bearing load reduction design method based on stator eccentricity, which specifically includes the following steps: 1. Establish a model of a non-uniform air gap permanent magnet synchronous motor; the structural design of the motor model is as follows: 1. Stator part: adopt standard stator structure, set winding parameters consistent with conventional PMSM to ensure that the basic performance of the motor is not affected.

[0017] 2. Rotor part: It adopts permanent magnet rotor, and the pole arrangement corresponds to the stator.

[0018] 3. Air gap design: Set the air gap thickness to be shorter at the top and longer at the bottom, forming an obvious uneven air gap. Figure 1 and Figure 2 As shown, the air gap thickness between the stator and the rotor in the lower part is unevenly distributed in the axial direction, and the air gap thickness gradually increases from both sides to the middle; the air gap thickness between the stator and the rotor in the upper part is evenly distributed. For ease of explanation, in the embodiment of the present invention, the air gap thickness between the stator and the rotor in the upper part is 1.5 mm, and the air gap thickness in the lower part gradually increases from both sides to the middle along the axial direction, and evenly transitions from 1.5 mm to 2.0 mm.

[0019] 4. Material parameter setting: including the magnetic permeability of the stator core, rotor permanent magnet and air gap.

[0020] 2. Magnetic Field Analysis Calculation The V-type magnet motor model is equivalent to an equivalent surface-mount magnet analytical motor model, and the model is used for analytical calculation.

[0021] (1) The magnetic isolation bridges on both sides of the two permanent magnets are equivalent to two sectors, and the sectors have a constant width angle along the radial direction.

[0022] (2) In the equivalent model, the width angle of each sector is equal to the width angle of the magnetic isolation bridge; the angle between the two sectors under one pole is equal to the central angle occupied by the two permanent magnets.

[0023] (3) The two permanent magnets are equivalent to a surface-mounted permanent magnet. The surface-mounted area has a constant thickness along the circumferential direction, and the straight lines at its two ends are respectively in a straight line with the boundaries of the two sectors.

[0024] (4) In the equivalent model, the thickness of the surface-mounted area is equal to the height of a permanent magnet in the original motor.

[0025] (5) Determine the radius of the surface-mounted area so that the magnetic flux of the equivalent analytical motor model is equal to the magnetic flux of the V-magnet motor model.

[0026] The global analytical model of the eccentric magnetic field of the surface-mounted motor is derived by using the canonical perturbation method, and the air gap magnetic field distribution under the eccentric state is obtained. On this basis, the unbalanced magnetic pull under this state is analyzed.

[0027] The basic idea of ​​the canonical perturbation method is: for a system with a parameter that is difficult to determine accurately or changes slowly, to find an approximate solution near a given parameter, the problem can be reduced to a perturbation problem of a small parameter through parameter transformation. Therefore, the perturbation method is also called the small parameter expansion method. The small parameter that can reflect the physical characteristics is used as the perturbation quantity, and then it is assumed that the solution can be expanded into a power series according to the small parameter. After substituting this formal series into the dimensionless equation, approximate equations of various levels can be obtained. Based on these equations, the coefficients of the power series can be determined, and the series can be truncated and approximated to obtain an asymptotic solution to the original equation.

[0028] The solution area is divided into permanent magnet area 1, non-uniform air gap area 2, and stator slot area 3, as shown in Figure 3 shown.

[0029] Establish an analytical model in polar coordinate system, such as Figure 4 As shown, the stator center Is a fixed coordinate system The origin of the rotor is a rotating coordinate system The origin of is the eccentricity coefficient; is the initial value of the component in this direction; is the eccentricity angle, and the relationship between the two coordinate systems is as follows: (1); (2).

[0030] 1. Magnetic field distribution analysis: Use analytical algorithms to simulate the magnetic field of the non-uniform air gap model to obtain the distribution of magnetic flux density and magnetic field intensity.

[0031] In the coordinate system The vector magnetic potential in the non-uniform air gap region satisfies the Laplace equation and Poisson equation: Permanent magnet area 1: (3); Uneven air gap area 2: (4); No. Stator slot area 3: (5); in, , is the current density loaded in the stator slot, is the symbol of partial derivative; is the magnetization intensity of the permanent magnet; is the vacuum permeability, Represents the curl of the magnetization intensity, which is usually zero inside a permanent magnet.

[0032] The above formula is about the vector magnetic potential ( A 1 ,A 2 ,A i 3 ), which are expressed in the cylindrical coordinate system (r,θ) and describe the magnetic field behavior in different regions of the motor.

[0033] Combined with the boundary conditions, the zero-order air gap flux density and the first-order air gap flux density distribution are obtained. The total air gap flux density distribution under rotor eccentricity is as follows: (6); (7); in, and Represent the radial and tangential components of the air gap flux density, respectively. (0) represents the zero-order magnetic flux density component when there is no eccentricity, and the superscript (1) It indicates the change of the first-order magnetic flux component due to eccentricity. The radial air gap magnetic flux waveform under uneven air gap is as follows: Figure 5 shown.

[0034] 2. Magnetic force calculation: According to the simulation results, calculate the magnetic force distribution, such as Figure 6As shown, special attention is paid to the change of magnetic tension in the bearing area.

[0035] The radial unbalanced magnetic pull can be written as: (8); in, is the magnitude of the resultant force, i.e., the two forces and The magnitude of the single force obtained after synthesis; and There are two mutually perpendicular force components in the x-axis and y-axis directions respectively.

[0036] error: (9).

[0037] 3. Evaluation of the impact of magnetic pull on bearings 1. Magnetic force distribution characteristics: The uneven air gap causes differences in magnetic flux density in the axial direction. The upper air gap is smaller, the magnetic flux density is larger, and the magnetic force is stronger; the lower air gap is larger, the magnetic flux density is smaller, and the magnetic force is weaker. This distribution causes the bearing shaft to bear uneven magnetic force in the axial direction, forming an unbalanced torque; 2. Vibration and noise impact: Uneven magnetic pull will cause periodic vibration and noise during the operation of the motor. This vibration will have a negative impact on the stability and service life of the motor, increase mechanical wear, and reduce the operating efficiency of the motor.

[0038] The simulation results show that the magnetic flux density in the upper part of the air gap is 0.75 T and in the lower part is 0.65 T. Through the force calculation module, it is found that the magnetic pull force on the upper part of the bearing shaft is 820 N and on the lower part is 808 N, resulting in an axial unbalanced force of 12 N on the bearing shaft. Further analysis shows that the stress of the bearing shaft is concentrated in the upper area, which may cause local fatigue and fracture.

[0039] Fourth, adjust the thickness of the uneven air gap and verify its effect through simulation.

[0040] Based on the above evaluation results, the air gap thickness is optimized to effectively improve the running stability of the motor and the service life of the bearing shaft.

Claims

1. A method for reducing the load on the bearing of a permanent magnet synchronous motor based on stator eccentricity, characterized in that: The following steps are involved: Establish a model of non-uniform air gap permanent magnet synchronous motor; Conduct magnetic field distribution simulation to obtain magnetic flux density and magnetic field intensity distribution data; Calculate the magnetic pull distribution at different air gap positions and evaluate the impact of unevenly distributed air gaps on the bearing shaft; Adjust the thickness of the uneven air gap to reduce the bearing load.

2. The method for designing bearing load reduction of a permanent magnet synchronous motor based on stator eccentricity according to claim 1 is characterized in that: In the uneven air-gap permanent magnet synchronous motor model, the air gap thickness between the stator and the rotor in the lower part is unevenly distributed in the axial direction, and the air gap thickness gradually increases from both sides to the middle; the air gap thickness between the stator and the rotor in the upper part is evenly distributed.

3. The method for designing bearing load reduction of a permanent magnet synchronous motor based on stator eccentricity according to claim 2 is characterized in that: The uniformly distributed air gap thickness is less than or equal to a minimum value of the non-uniformly distributed air gap thickness.

4. A non-uniform air gap permanent magnet synchronous motor, characterized in that: The thickness of the air gap between the stator and the rotor in the lower part of the motor is unevenly distributed in the axial direction, and the thickness of the air gap gradually increases from both sides to the middle; the thickness of the air gap between the stator and the rotor in the upper part is evenly distributed.

5. The non-uniform air gap permanent magnet synchronous motor according to claim 4, characterized in that: The uniformly distributed air gap thickness is less than or equal to a minimum value of the non-uniformly distributed air gap thickness.

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