Method for measuring static unbalanced magnetic pulling force of permanent magnet synchronous motor with concentrated fractional slot windings

Abstract

The invention provides a method for measuring static unbalanced magnetic pulling force of a fractional slot concentrated winding permanent magnet synchronous motor. The method comprises the following steps: S1, establishing a mathematical model of a radial electromagnetic force wave fr and a tangential electromagnetic force wave ft of a motor, obtaining an unbalanced magnetic pulling force Fx on an x axis and an unbalanced magnetic pulling force Fy on a y axis, and obtaining the value and direction of the overall unbalanced magnetic pulling force; s2, building an electromagnetic model of the tested motor, and determining the position of a rotor generating vertically downward unbalanced magnetic pulling force and a three-phase current instantaneous value; s3, building an experimental measurement platform; s4, adjusting the position of a motor rotor based on a simulation analysis result, inputting a three-phase direct current equal to the instantaneous value of the three-phase current to measure the static unbalanced magnetic pulling force, changing the input three-phase direct current in proportion, and recording the change trend of an output result of the pressure sensor; according to the invention, the change of the unbalanced magnetic pulling force can be indirectly represented, and the unbalanced magnetic pulling force caused by rotor eccentricity can be eliminated.

Description

Technical Field

[0001] The invention relates to the field of permanent magnet synchronous motors, in particular to a method for measuring static unbalanced magnetic pulling force of a fractional slot concentrated winding permanent magnet synchronous motor. Background Art

[0002] Fractional slot concentrated winding permanent magnet synchronous motor has the advantages of high torque density / power density, short winding ends and high slot fill rate. It is widely used as the power source and core moving parts of electric vehicles, household appliances, new energy power generation, CNC machine tools, robots, national defense and military equipment. Among them, slot-pole combination motors such as 4-pole / 9-slot, 8-pole / 9-slot and 10-pole / 9-slot have higher winding fundamental wave coefficient and lower winding end resistance, which have attracted attention in motor design. However, the motors with these slot-pole combinations have large unbalanced magnetic pull in the rotor, which causes motor vibration and noise and reduces the service life of the bearing. Since the unbalanced magnetic pull is a radial force acting on the rotor, its size and direction change with the rotation of the rotor. In normal operation of the motor, in order to prevent the unbalanced magnetic pull from causing rotor eccentricity, the rotor is generally fixed by bearings. Based on the above factors, there are few reports on testing the unbalanced magnetic pull of the motor. Therefore, it is of great significance to study the static unbalanced magnetic pull measurement method of the surface-mounted permanent magnet synchronous motor with fractional slot concentrated winding to suppress the unbalanced magnetic pull. Summary of the invention

[0003] The present invention proposes a static unbalanced magnetic pull measurement method for a fractional-slot concentrated winding permanent magnet synchronous motor, which can indirectly characterize the change of the unbalanced magnetic pull by combining finite element simulation software with actual measurement experiments, and can also eliminate the unbalanced magnetic pull caused by rotor eccentricity during the measurement process.

[0004] The present invention adopts the following technical solutions.

[0005] The present invention adopts the following technical solutions.

[0006] A method for measuring static unbalanced magnetic pull of a fractional slot concentrated winding permanent magnet synchronous motor comprises the following steps:

[0007] Step S1: Establish radial electromagnetic force wave f of fractional slot concentrated winding permanent magnet synchronous motor r and the tangential electromagnetic force wave f t The mathematical model of the two is decomposed and integrated in the two-dimensional plane to obtain the unbalanced magnetic pull F on the x-axis x and the unbalanced magnetic pull F on the y-axis y , the value and direction of the overall unbalanced magnetic pull are obtained through trigonometric functions;

[0008] Step S2: constructing an electromagnetic model of the motor under test in finite element software to determine the rotor position and instantaneous values ​​of the three-phase current that generate the vertically downward unbalanced magnetic pull;

[0009] Step S3: constructing an experimental measurement platform including a pressure sensor, and measuring the force data of the shaft with the pressure sensor when a UMF that causes the shaft to deflect is generated on the motor shaft;

[0010] Step S4: Adjust the motor rotor position based on the simulation analysis results, input three-phase direct current equal to the instantaneous value of the three-phase current to measure the static unbalanced magnetic pull, change the input three-phase direct current proportionally, and record the change trend of the pressure sensor output result.

[0011] In step S1, a mathematical model is established based on the Maxwell stress tensor method.

[0012] In step S1, the radial electromagnetic force wave f of the fractional slot concentrated winding permanent magnet synchronous motor r and the tangential electromagnetic force wave f t The mathematical model is expressed as:

[0013]

[0014] In formula 1, B r and B t Represents radial air gap flux density and tangential air gap flux density, μ 0 Represents the vacuum magnetic permeability. The unbalanced magnetic pull components F on the x and y axes are obtained by decomposing and integrating the radial electromagnetic force wave and the tangential electromagnetic force wave in a two-dimensional plane. x and F y The formula is:

[0015]

[0016] In the formula, R represents the rotor radius, L represents the stator axial length, and θ represents the rotor position;

[0017] Based on formula 2, the overall unbalanced magnetic pull is: The direction angle of the unbalanced magnetic pull can be obtained by using the trigonometric formula:

[0018] The electromagnetic model of the motor under test constructed in the finite element software in step S2 is a 2D electromagnetic model. After the model is incorporated into the formula in step S1, its finite element is simulated to determine the rotor position that generates the vertical downward unbalanced magnetic pull and the instantaneous value of the three-phase current based on the arrangement structure of the three-phase winding of the motor model under test.

[0019] In step S3, the experimental measurement platform includes a motor stator bracket, a pressure sensor, a pressure display instrument and a body mounting platform.

[0020] In step S3, when assembling the experimental measurement platform, the bearing housing is first separated from the motor housing, and then the bearing housing is fixed to the machine body mounting platform through a pressure sensor. Then, the motor housing is directly mounted on the machine body mounting platform, and a filler is placed into the motor air gap to eliminate the unbalanced magnetic pull caused by the rotor eccentricity.

[0021] In step S3, the filler in the motor air gap is a synthetic resin, which is used to eliminate the unbalanced magnetic pull caused by the rotor eccentricity during the measurement process and suppress the UMF generated by the slot-pole combination, so that the experimental process can accurately measure the unbalanced magnetic pull caused by the non-uniformly distributed air gap magnetic field generated by the motor slot-pole combination.

[0022] In step S3, one end of the pressure sensor is fixed to the bearing housing by bolts, and the other end is connected to the body mounting platform;

[0023] In step S3, during the experiment, the pressure display is reset to zero. When a UMF that causes the motor shaft to deviate is generated, the pressure sensor measures relevant data, which is displayed and recorded through the pressure display connected thereto.

[0024] In step S4, the three-phase direct current changes in proportion according to the finite element simulation analysis result, and the rotor position remains unchanged.

[0025] In step S3, the filler inserted into the air gap of the motor allows the unbalanced magnetic pull on the rotor to be shared by the motor housing, and the pressure sensor test result cannot reflect the actual unbalanced magnetic pull of the motor. In this step, in order to reduce the influence of the motor housing on the measured unbalanced magnetic pull result, the change in the unbalanced magnetic pull is indirectly characterized by the change trend of the measured value of the pressure sensor under different current amplitudes.

[0026] The present invention discloses a method for measuring the static unbalanced magnetic pull of a permanent magnet synchronous motor with a fractional slot concentrated winding. For the first time, the method determines the direction of action of the unbalanced magnetic pull based on the Maxwell stress tensor method from the perspective of the mechanism of generating the unbalanced magnetic pull, and fills the air gap of the motor with synthetic resin to eliminate the unbalanced magnetic pull generated by the rotor eccentricity. Finally, a three-phase direct current is input to measure the change trend of the static unbalanced magnetic pull. Compared with the prior art, the method has the following beneficial effects:

[0027] (1) The present invention proposes for the first time a method for measuring the static unbalanced magnetic pull of a fractional-slot concentrated winding permanent magnet synchronous motor, which indirectly characterizes the change of the unbalanced magnetic pull by combining finite element simulation software with actual measurement experiments.

[0028] (2) The present invention only measures the unbalanced magnetic pull caused by the non-uniformly distributed air gap magnetic field generated by the slot-pole combination of the motor, and excludes the unbalanced magnetic pull caused by the rotor eccentricity during the measurement process, which provides an experimental idea for the study of suppressing the unbalanced magnetic pull generated by the slot-pole combination.

[0029] The present invention determines for the first time the rotor position and the instantaneous value of the three-phase current that generate the vertically downward unbalanced magnetic pull through finite element simulation analysis from the perspective of the unbalanced magnetic pull generation mechanism. At the same time, in order to measure only the unbalanced magnetic pull caused by the non-uniformly distributed air gap magnetic field generated by the slot-pole combination of the motor and exclude the unbalanced magnetic pull caused by rotor eccentricity during the measurement process, the motor air gap is filled with synthetic resin, which provides an experimental idea for the study of suppressing the unbalanced magnetic pull generated by the slot-pole combination. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0031] Attached Figure 1 It is a schematic diagram of the side section design of the unbalanced magnetic tension measurement experimental platform in a specific embodiment of the present invention;

[0032] Attached Figure 2 Schematic diagram of an unbalanced magnetic tension measurement experimental platform in a specific embodiment of the present invention;

[0033] Attached Figure 3 is a schematic diagram of a DC three-phase current input in a specific implementation manner of the present invention;

[0034] Attached Figure 4 is a schematic diagram of the rotor position and the direction of the unbalanced magnetic pull in a specific embodiment of the present invention;

[0035] Attached Figure 5 It is a schematic diagram of the static unbalanced magnetic pull measurement results in a specific implementation manner of the present invention. DETAILED DESCRIPTION

[0036] As shown in the figure, the static unbalanced magnetic pull measurement method of the fractional slot concentrated winding permanent magnet synchronous motor includes the following steps:

[0037] Step S1: Establish radial electromagnetic force wave f of fractional slot concentrated winding permanent magnet synchronous motor r and the tangential electromagnetic force wave f t The mathematical model of the two is decomposed and integrated in the two-dimensional plane to obtain the unbalanced magnetic pull F on the x-axis x and the unbalanced magnetic pull F on the y-axis y , the value and direction of the overall unbalanced magnetic pull are obtained through trigonometric functions;

[0038] Step S2: constructing an electromagnetic model of the motor under test in finite element software to determine the rotor position and instantaneous values ​​of the three-phase current that generate the vertically downward unbalanced magnetic pull;

[0039] Step S3: constructing an experimental measurement platform including a pressure sensor, and measuring the force data of the shaft with the pressure sensor when a UMF that causes the shaft to deflect is generated on the motor shaft;

[0040] Step S4: Adjust the motor rotor position based on the simulation analysis results, input three-phase direct current equal to the instantaneous value of the three-phase current to measure the static unbalanced magnetic pull, change the input three-phase direct current proportionally, and record the change trend of the pressure sensor output result.

[0041] In step S1, a mathematical model is established based on the Maxwell stress tensor method.

[0042] In step S1, the radial electromagnetic force wave f of the fractional slot concentrated winding permanent magnet synchronous motor r and the tangential electromagnetic force wave f t The mathematical model is expressed as:

[0043]

[0044] In formula 1, B r and B t Represents radial air gap flux density and tangential air gap flux density, μ 0 Represents the vacuum magnetic permeability. The unbalanced magnetic pull components F on the x and y axes are obtained by decomposing and integrating the radial electromagnetic force wave and the tangential electromagnetic force wave in a two-dimensional plane. x and F y The formula is:

[0045]

[0046] In the formula, R represents the rotor radius, L represents the stator axial length, and θ represents the rotor position;

[0047] Based on formula 2, the overall unbalanced magnetic pull is: The direction angle of the unbalanced magnetic pull can be obtained by using the trigonometric formula:

[0048] The electromagnetic model of the motor under test constructed in the finite element software in step S2 is a 2D electromagnetic model. After the model is incorporated into the formula in step S1, its finite element is simulated to determine the rotor position that generates the vertical downward unbalanced magnetic pull and the instantaneous value of the three-phase current based on the arrangement structure of the three-phase winding of the motor model under test.

[0049] In this example, based on the arrangement structure of the three-phase winding of the motor model under test, the rotor position angle that generates the vertical downward unbalanced magnetic pull is determined to be -145.5 degrees, and the relationship between the instantaneous values ​​of the three-phase current is i a =-2i b 、i a =-2i c .

[0050] In step S3, the experimental measurement platform includes a motor stator bracket, a pressure sensor, a pressure display instrument and a body mounting platform.

[0051] In step S3, when assembling the experimental measurement platform, the bearing housing is first separated from the motor housing, and then the bearing housing is fixed to the machine body mounting platform through a pressure sensor. Then, the motor housing is directly mounted on the machine body mounting platform, and a filler is placed into the motor air gap to eliminate the unbalanced magnetic pull caused by the rotor eccentricity.

[0052] In step S3, the filler in the motor air gap is a synthetic resin, which is used to eliminate the unbalanced magnetic pull caused by the rotor eccentricity during the measurement process and suppress the UMF generated by the slot-pole combination, so that the experimental process can accurately measure the unbalanced magnetic pull caused by the non-uniformly distributed air gap magnetic field generated by the motor slot-pole combination.

[0053] In step S3, one end of the pressure sensor is fixed to the bearing housing by bolts, and the other end is connected to the body mounting platform;

[0054] In step S3, during the experiment, the pressure display is reset to zero. When a UMF that causes the motor shaft to deviate is generated, the pressure sensor measures relevant data, which is displayed and recorded through the pressure display connected thereto.

[0055] In step S4, the three-phase direct current changes in proportion according to the finite element simulation analysis result, and the rotor position remains unchanged.

[0056] In step S3, the filler inserted into the air gap of the motor allows the unbalanced magnetic pull on the rotor to be shared by the motor housing, and the pressure sensor test result cannot reflect the actual unbalanced magnetic pull of the motor. In this step, in order to reduce the influence of the motor housing on the measured unbalanced magnetic pull result, the change in the unbalanced magnetic pull is indirectly characterized by the change trend of the measured value of the pressure sensor under different current amplitudes.

[0057] In this example, the change rate of the unbalanced magnetic pull measured by the pressure sensor is approximately equal to the change rate of the unbalanced magnetic pull simulated by the finite element method.

Claims

1. A method for measuring static unbalanced magnetic pull of a fractional-slot concentrated winding permanent magnet synchronous motor, characterized in that: The steps include: Step S1: Establish radial electromagnetic force wave f of fractional slot concentrated winding permanent magnet synchronous motor r and the tangential electromagnetic force wave f t The mathematical model of the two is decomposed and integrated in the two-dimensional plane to obtain the unbalanced magnetic pull F on the x-axis x and the unbalanced magnetic pull F on the y-axis y , the value and direction of the overall unbalanced magnetic pull are obtained through trigonometric functions; Step S2: constructing an electromagnetic model of the motor under test in finite element software to determine the rotor position and instantaneous values ​​of the three-phase current that generate the vertically downward unbalanced magnetic pull; Step S3: constructing an experimental measurement platform including a pressure sensor, and measuring the force data of the shaft with the pressure sensor when a UMF that causes the shaft to deflect is generated on the motor shaft; Step S4: Adjust the motor rotor position based on the simulation analysis results, input three-phase direct current equal to the instantaneous value of the three-phase current to measure the static unbalanced magnetic pull, change the input three-phase direct current proportionally, and record the change trend of the pressure sensor output result.

2. The method for measuring static unbalanced magnetic pull of a fractional-slot concentrated winding permanent magnet synchronous motor according to claim 1, characterized in that: In step S1, a mathematical model is established based on the Maxwell stress tensor method.

3. The method for measuring static unbalanced magnetic pull of a fractional-slot concentrated winding permanent magnet synchronous motor according to claim 2, characterized in that: In step S1, the radial electromagnetic force wave f of the fractional slot concentrated winding permanent magnet synchronous motor r and the tangential electromagnetic force wave f t The mathematical model is expressed as: In formula 1, B r and B t represents the radial air gap magnetic flux and the tangential air gap magnetic flux, and μ0 represents the vacuum magnetic permeability. The unbalanced magnetic pull components F on the x and y axes are obtained by decomposing and integrating the radial electromagnetic force wave and the tangential electromagnetic force wave in a two-dimensional plane. x and F y The formula is: In the formula, R represents the rotor radius, L represents the stator axial length, and θ represents the rotor position; Based on formula 2, the overall unbalanced magnetic pull is: The direction angle of the unbalanced magnetic pull can be obtained by using the trigonometric formula:

4. The method for measuring static unbalanced magnetic pull of a fractional-slot concentrated winding permanent magnet synchronous motor according to claim 3, characterized in that: The electromagnetic model of the motor under test constructed in the finite element software in step S2 is a 2D electromagnetic model. After the model is incorporated into the formula in step S1, its finite element is simulated to determine the rotor position that generates the vertical downward unbalanced magnetic pull and the instantaneous value of the three-phase current based on the arrangement structure of the three-phase winding of the motor model under test.

5. The method for measuring static unbalanced magnetic pull of a fractional-slot concentrated winding permanent magnet synchronous motor according to claim 3, characterized in that: In step S3, the experimental measurement platform includes a motor stator bracket, a pressure sensor, a pressure display instrument and a body mounting platform.

6. The method for measuring static unbalanced magnetic pull of a fractional-slot concentrated winding permanent magnet synchronous motor according to claim 3, characterized in that: In step S3, when assembling the experimental measurement platform, the bearing housing is first separated from the motor housing, and then the bearing housing is fixed to the machine body mounting platform through a pressure sensor. Then, the motor housing is directly mounted on the machine body mounting platform, and a filler is placed into the motor air gap to eliminate the unbalanced magnetic pull caused by the rotor eccentricity.

7. The method for measuring static unbalanced magnetic pull of a fractional-slot concentrated winding permanent magnet synchronous motor according to claim 6, characterized in that: In step S3, the filler in the motor air gap is a synthetic resin, which is used to eliminate the unbalanced magnetic pull caused by the rotor eccentricity during the measurement process and suppress the UMF generated by the slot-pole combination, so that the experimental process can accurately measure the unbalanced magnetic pull caused by the non-uniformly distributed air gap magnetic field generated by the motor slot-pole combination.

8. The method for measuring static unbalanced magnetic pull of a fractional-slot concentrated winding permanent magnet synchronous motor according to claim 6, characterized in that: In step S3, one end of the pressure sensor is fixed to the bearing housing by bolts, and the other end is connected to the body mounting platform; In step S3, during the experiment, the pressure display is reset to zero. When a UMF that causes the motor shaft to deviate is generated, the pressure sensor measures relevant data, which is displayed and recorded through the pressure display connected thereto.

9. The method for measuring static unbalanced magnetic pull of a fractional-slot concentrated winding permanent magnet synchronous motor according to claim 6, characterized in that: In step S4, the three-phase direct current changes in proportion according to the finite element simulation analysis result, and the rotor position remains unchanged.

10. The method for measuring static unbalanced magnetic pull of a fractional-slot concentrated winding permanent magnet synchronous motor according to claim 6, characterized in that: In step S3, the filler inserted into the air gap of the motor allows the unbalanced magnetic pull on the rotor to be shared by the motor housing, and the pressure sensor test result cannot reflect the actual unbalanced magnetic pull of the motor. In this step, in order to reduce the influence of the motor housing on the measured unbalanced magnetic pull result, the change in the unbalanced magnetic pull is indirectly characterized by the change trend of the measured value of the pressure sensor under different current amplitudes.

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