Method for evaluating the NVH behavior of an electric machine with an inclined rotor and / or stator and computing unit

Abstract

Method for evaluating the NVH (Noise, Vibration, Harshness) behavior of an electrical machine, in particular a synchronous machine, with an inclined rotor and / or stator, wherein the method comprises the following steps: Dividing the electric machine into N disks and arranging the disks according to their axial position in the electric machine, Determining electromagnetic excitations (sk1 to sk5) for each disk at a specific harmonic, Calculating a weighted sum (S0) from the individual electromagnetic excitations (sk1 to sk5) for the entire electrical machine, wherein in the weighted sum (S0) the electromagnetic excitations (sk1 to sk5) are weighted according to a proportion of the disks in the electrical machine, Dividing the electric machine into two groups, each corresponding to half the length of the electric machine, and calculating a respective weighted sum (SD1_1, SD1_2) of the individual electromagnetic excitations (sk1 to sk5) for the two groups, wherein in the weighted sums (SD1_1, SD1_2) the electromagnetic excitations (sk1 to sk5) are weighted according to a proportion of the disks in the respective of the two groups, Calculating differences (S1_1, S1_2) according to the following formulas: S1_1 = SD1_1 − S0 , S1_2 = SD1_2 − S0 , Determining an average size (S1) of the differences (S1_1, S1_2), Dividing the electric machine into four groups, each corresponding to a quarter of the length of the electric machine, and calculating a respective weighted sum (SD2_1 to SD2_4) of the individual electromagnetic excitations (sk1 to sk5) for the four groups, wherein in the weighted sums (SD2_1 to SD2_4) the electromagnetic excitations (sk1 to sk5) are weighted according to a proportion of the disks in the respective of the four groups, Calculating differences (S2_1 to S2_4) according to the following formulas: S2_1 = SD2_1 − S1_1 S2_2 = SD2_2 − S1_1 S2_3 = SD2_3 − S1_2 S2_4 = SD2_4 − S1_2 Determining an average size (S2) of the differences (S2_1 to S2_4), and Evaluating the NVH behavior of the electric machine based on the size of the weighted sum (S0) and the average sizes (S1 and S2).

Description

[0001] The present invention relates to a method for evaluating, in particular optimizing, the NVH (Noise, Vibration, Harshness) behavior of an electric machine with an inclined or skewed rotor and / or stator and a computing unit configured and programmed to execute the method.

[0002] Calculating the electromagnetic forces occurring in the air gap between the stator and rotor of an electric machine allows the generation of excitation data sets that can be used for further analysis, such as evaluating NVH (noise, vibration, and harshness) behavior. A common method for optimizing the NVH behavior of an electric machine (e.g., to minimize response to eigenmodes due to specific harmonics or overtones of the electromagnetic excitation) is to tilt or angle the rotor and / or stator of the electric machine.

[0003] If the rotor and / or stator are inclined, it helps to understand and characterize how the harmonics of the excitation force are distributed across all disks to improve the NVH behavior.

[0004] Several prior art articles deal with the optimization of the NVH behavior of electrical machines by optimizing the tilt of the rotor and / or stator: - Lee, CM, Seol, HS, Lee, JY, Lee, SH and Kang, DW, 2017. Optimization of vibration and noise characteristics of skewed permanent brushless direct current motor. IEEE Transactions on Magnetics, 53(11), pp.1-5. - Howard, E., Kamper, MJ and Gerber, S., 2015. Asymmetric flux barrier and skew design optimization of reluctance synchronous machines. IEEE Transactions on Industry Applications, 51(5), pp.3751-3760. - Lin, F., Zuo, SG, Deng, WZ and Wu, SL, 2018. Reduction of vibration and acoustic noise in permanent magnet synchronous motor by optimizing magnetic forces. Journal of Sound and Vibration, 429, pp.193-205. - Ponomarev, Pavel; Aarniovuori, Lassi; Keränen, Janne: Selection of optimal slice count for multi-slice analysis of skewed induction motors. In: IECON 2017 43 rd Annual Conference Of The IEEE Industrial Electronic Society, 29 October 2017 - 01 November 2017. IEEE, 2017. pp. 2149-2153. ISBN 978-1-5386-1127-2.

[0005] This paper describes a method for evaluating the NVH behavior of an electric machine with a tilted rotor. - Gyselinck, Johan JC; Vandevelde, Lieven; Melkebeek, Jan AA: Multi-Slice FE Modeling Of Electrical Machines With Skewed Slots - The Skew Discretization Error. In: IEEE Transactions On Magnetics, Vol. 37, 2001, No. 5, pp. 3233-3237. ISSN 0018-9464.

[0006] This paper also describes a method for evaluating the NVH behavior of an electric machine with an inclined rotor.

[0007] However, none of the studies mentioned describe how the excitation forces are to be distributed across the discs.

[0008] Optimizing the electromagnetic excitation in an electric machine is a crucial aspect of improving its NVH (noise, vibration, and harshness) behavior. This typically involves reducing the amplitude of the resulting force across all disks for a specific harmonic of the excitation forces.

[0009] However, the way in which the excitation forces are distributed across all disks of an inclined rotor and / or stator also has a significant influence on the NVH behavior of the electric machine. Therefore, optimizing this distribution also represents a major potential for improving NVH performance.

[0010] It is therefore an object of the present invention to provide a technique which enables a simple and appropriate evaluation of the influence of electromagnetic excitation on the NVH behavior of an electrical machine.

[0011] This problem is solved by the articles with the features according to the independent claims. Advantageous embodiments are the subject of the dependent claims.

[0012] Disclosed is a method for evaluating, in particular optimizing, the NVH (Noise, Vibration, Harshness) behavior of an electrical machine, especially a synchronous machine, with an inclined rotor and / or stator. The method comprises the following steps: Divide the electric machine into N disks and arrange the disks according to their axial position within the machine. N is defined according to the number of disks, e.g., 5. The disks can correspond to stacks. Within the stacks, the inclination can be continuous. However, different inclinations and / or angular spacings can be provided between adjacent stacks. Stacks are typically used for the rotor. The stacks can have the same dimensions or different thicknesses or dimensions in the axial direction of the electric machine. The method can also be applied with a continuous inclination of the rotor and / or stator. With a continuously inclined rotor and / or stator, the number N can be set to a larger value, e.g., 10 or greater. The disks are then arranged according to their position within the electric machine.

[0013] Determining the electromagnetic excitations (sk1 to sk5) for each disk at a specific harmonic. The electromagnetic excitations of the individual disks or stacks can be obtained, for example, by 2D or 3D simulation or calculation.

[0014] Calculate a weighted sum (S0) from the individual electromagnetic excitations (sk1 to sk5) for the entire electric machine. In calculating the weighted sum (S0), the electromagnetic excitations (sk1 to sk5) are weighted according to the proportion of each disk in the electric machine. For example, a disk with a 20% proportion is weighted with a factor of 0.2. As mentioned previously, the disks can have the same thickness or different thicknesses in the axial direction of the electric machine.

[0015] The electric machine is divided into two groups, each corresponding to half the machine's length, and a weighted sum (SD1_1, SD1_2) of the individual electromagnetic excitations (sk1 to sk5) is calculated for each group. When calculating the weighted sums (SD1_1, SD1_2), the electromagnetic excitations (sk1 to sk5) are weighted according to the disk's share of each of the two groups. A disk with a 40% share of the first of the four groups is weighted with 0.4. It is also possible for a disk to have different shares in the groups. If a disk is not included in any group, it is weighted with 0.

[0016] Calculating differences (S1_1, S1_2) according to the following formulas: S1_1=SD1_1−S0, S1_2=SD1_2−S0, and

[0017] Determining an average size (S1) of the differences (S1_1, S1_2).

[0018] The electric machine is divided into four groups, each corresponding to a quarter of the machine's length, and a weighted sum (SD2_1 to SD2_4) of the individual electromagnetic excitations (sk1 to sk5) is calculated for each of the four groups. When calculating the weighted sums (SD2_1 to SD2_4), the electromagnetic excitations (sk1 to sk5) are weighted according to the disk's share of each of the four groups. A disk with a 40% share of the first of the four groups is weighted with 0.4. It is also possible for a disk to have different shares in the groups. If a disk is not included in any group, it is weighted with 0.

[0019] Calculating differences (S2_1 to S2_4) according to the following formulas: S2_1=SD2_1−S1_1, S2_2=SD2_2−S1_1, S2_3=SD2_3−S1_2, S2_4=SD2_4−S1_2, and

[0020] Determining an average size (S2) of the differences (S2_1 to S2_4).

[0021] The NVH behavior of the electric machine is evaluated based on the magnitude of the weighted sum (S0) and the average values ​​(S1 and S2). Therefore, the NVH behavior of the electric machine can already be adequately assessed using these three determined values. Furthermore, these three values ​​are also determined for a different number of disks, so that the same parameters can always be used to evaluate the NVH behavior.

[0022] Furthermore, an angle (alpha_o1) between the vector (S1_1, S0) and the vector (S1_2, S0) can be calculated, and this angle (alpha_o1) can be taken into account when evaluating the NVH behavior. Therefore, an additional parameter is available for evaluating the NVH behavior.

[0023] A warning can be issued if the angle (alpha_o1) deviates from 180°. Therefore, a warning will be issued if the design of the electrical machine is faulty.

[0024] Furthermore, an angle (alpha_o2_1) between the vector (S2_1, S1_1) and the vector (S2_2, S1_1) can be calculated, and this angle (alpha_o2_1) can be taken into account when evaluating the NVH behavior. Therefore, an additional parameter is available for evaluating the NVH behavior.

[0025] Additionally, an angle (alpha_o2_2) between the vector (S2_3, S1_2) and the vector (S2_4, S1_2) can be calculated, and this angle (alpha_o2_2) can be taken into account when evaluating the NVH behavior. Therefore, another parameter is available for evaluating the NVH behavior.

[0026] An angle (beta_o2) between the vector (S2_1, S2_2) and the vector (S2_3, S1_4) can be calculated and this angle (beta_o2) can be taken into account when evaluating NVH behavior. Therefore, an additional parameter is available for evaluating NVH behavior.

[0027] After the procedure has been carried out, the design of the electric machine can be modified. The procedure is then repeated to evaluate the NVH behavior of the modified design. Consequently, the two designs of the electric machine can be compared. These newly defined parameters can also be used as target criteria for multi-objective optimization of the electric machine.

[0028] The procedure can be performed for a multiple of harmonics. The harmonics can be specifically selected according to their influence on NVH behavior.

[0029] Finally, the design of the electric machine, in which the NVH behavior is optimized or exhibits the desired or required characteristics, can be output in order to manufacture the electric machine accordingly. Therefore, an electric machine with optimized NVH behavior can be manufactured.

[0030] Furthermore, a computing unit is revealed that is trained and programmed to execute the procedure according to the aspects mentioned above. The procedure is then present in the form of program code.

[0031] The present invention is described in detail below with reference to the figure. The figure shows: Fig. 1 a diagram showing parameters for evaluating the NVH behavior of an electric machine according to the present invention.

[0032] The present invention is described below with reference to preferred embodiments and the figure. However, this description of embodiments should not be considered exhaustive.

[0033] Fig. Figure 1 shows a diagram in which parameters for evaluating the NVH behavior of an electric machine according to the present invention are shown.

[0034] The procedure described below is applied to single harmonics (complex values) of an electromagnetic excitation. The application is described for a single harmonic (e.g., in the radial direction) for an inclined rotor divided into N=5 different disks of equal thickness. Therefore, in this example, each disk corresponds to 20% of the total axial length of the electric machine.

[0035] The actual values ​​of the disk angular positions are not used in the disassembly process. The application to other harmonics (e.g., in other directions or with other orders) or to other configurations of an inclined rotor and / or stator, or a different number of disks, is similar.

[0036] The disks are first sorted in ascending order according to their respective axial position.

[0037] The harmonic values ​​of the electromagnetic excitation are first determined for all disks. In the example under consideration, this corresponds to a vector of 5 complex values, which correspond to the previously mentioned order. These values ​​are in the Fig. The diagram shown in point sk1 to sk5 represents the points.

[0038] The weighted sum of the vector under consideration is then calculated. The weights consist of the ratio of the respective disk thickness to the total axial length. The sum of all weights is 1. For the subsequent steps of this disclosure, this value is referred to as "order 0" and denoted by "GLB" in Fig. 1 is marked. A vector S0 thus corresponds to a vector from the origin to the point GLB.

[0039] Two groups are then formed: one representing 0% to 50% (Group 1) and the other representing 50% to 100% (Group 2) of the axial length. New weights, designated "W1", are calculated for each group, based on the relative thickness of each layer compared to the axial length of the group.

[0040] The weights W1 calculated for the example under consideration are explained in more detail here. Each value "W1" is assigned an index that corresponds to the order of the discs (e.g., W1_3: weight for disc 3). For each group, the sum of all weights is equal to 1. For discs that are not present in a particular group, the corresponding weights are 0. - Group 1: W1_1 = 0.4; W1_2 = 0.4; W1_3 = 0.2; W1_4 = 0; W1_5 = 0 - Group 2: W1_1 = 0; W1_2 = 0; W1_3 = 0.2; W1_4 = 0.4; W1_5 = 0.4

[0041] Four groups are then formed: from 0% to 25% (Group 1), from 25% to 50% (Group 2), from 50% to 75% (Group 3), and from 75% to 100% (Group 4) of the axial length of the electric machine. For each group, new weights designated "W2" are calculated, which result from the relative thickness of each disk compared to the axial length of the group.

[0042] The weights W2, calculated for the example under consideration, are explained in more detail below. Each value "W2" is assigned an index corresponding to the disk's position (e.g., W2_3: weight for disk 3). For each group, the sum of all weights is equal to 1. For disks not present in a particular group, the corresponding weights are 0. - Group 1: W2_1 = 0.8; W2_2 = 0.2; W2_3 = 0; W2_4 = 0; W2_5 = 0 - Group 2: W2_1 = 0; W2_2 = 0.6; W2_3 = 0.4; W2_4 = 0; W2_5 = 0 - Group 3: W2_1 = 0; W2_2 = 0; W2_3 = 0.4; W2_4 = 0.6; W2_5 = 0 - Group 4: W2_1 = 0; W2_2 = 0; W2_3 = 0; W2_4 = 0.2; W2_5 = 0.8

[0043] For each of the two groups, the weighted sum of the individual groups is calculated using the initial excitation vector. The two resulting complex values ​​(one for each group) are labeled "SD1_1" and "SD1_2," respectively. These values ​​are represented in the diagram as triangles with their vertices pointing upwards.

[0044] The differences S1_1 = SD1_1 - S0 and S1_2 = SD1_2 - S0 are calculated. The value S1 is the average of S1_1 and S1_2 and is designated as "order 1". In the diagram, S1 is represented as a vector of GLB in the direction of point SD1_1.

[0045] For each of the four groups, the weighted sum of the individual groups is calculated using the initial excitation vector. The four resulting complex values ​​(one for each group) are labeled "SD2_1", "SD2_2", "SD2_3", and "SD2_4", respectively. These values ​​are represented in the diagram as downward-pointing triangles.

[0046] Then the differences S2_1 = SD2_1 - S1_1, S2_2 = SD2_2 - S1_1, S2_3 = SD2_3 - S1_2, and S2_4 = SD2_4 - S1_2 are calculated. The value S2 is the average of S2_1, S2_2, S2_3, and S2_4 and is referred to as "order 2". The value of S2 is in Fig. 1 is shown as an example vector from SD1_1 to SD2_1.

[0047] These three values, S0, S1, and S2, can be used to evaluate the NVH behavior of the electrical machine under consideration (e.g., specific resonance). By modifying the design of the electrical machine, these values ​​can then be adjusted accordingly to achieve the desired or required NVH behavior.

[0048] Furthermore, additional values ​​can be determined to evaluate the NVH behavior of the electric machine.

[0049] The angle between the vectors (S1_1, S0) and (S1_2, 0) is calculated and labeled "alpha_o1". A warning should be issued if the value deviates from 180 degrees.

[0050] The angle between the vectors (S2_1, S1_1) and (S2_2, S1_1) is calculated and denoted by “alpha_o2_1”.

[0051] The angle between the vectors (S2_3, S1_2) and (S2_4, S1_2) is calculated and denoted by “alpha_o2_2”.

[0052] The angle between the vectors (S2_1, S2_2) and (S2_3, S1_4) is calculated and denoted by "beta_o2".

[0053] The force distribution for the considered excitation harmonic is then preferably characterized by seven scalar values: S0, S1, S2, alpha_o1, alpha_o2_1, alpha_o2_2, and beta_o2. Relating these values ​​to the NVH behavior of the electrical machine under consideration (e.g., specific resonance) yields new optimization variables for improving the design and / or performance.

[0054] The proposed approach has been described in detail for the case of an inclined rotor with N=5 different disks. It can also be applied to continuously inclined rotors and / or stators by considering a large number of disks, e.g., 10 or more.

[0055] The approach can be applied to all inclined profiles, including “V-shapes” (i.e., with axial symmetry) and completely asymmetric shapes (i.e., with any individual angular positions and thickness values).

[0056] The result of the presented decomposition consists of the seven scalar values ​​mentioned above for all cases, regardless of the number of disks or other inclination properties.

[0057] The design of the electric machine can be modified after the procedure has been carried out. The steps of the procedure can then be repeated to evaluate the NVH behavior of the modified design.

[0058] If the NVH behavior is optimized or exhibits the desired or required characteristics, the design of the electric machine can be provided in order to manufacture the electric machine accordingly.

[0059] The procedure can be implemented in a computing unit that is trained and programmed to execute the procedure. The procedure then exists as program code, so that the procedure corresponds to a computer-implemented procedure.

Claims

[1] Method for evaluating the NVH (Noise, Vibration, Harshness) behavior of an electrical machine, in particular a synchronous machine, with an inclined rotor and / or stator, the method comprising the following steps: Dividing the electric machine into N disks and arranging the disks according to their axial position in the electric machine, Determining electromagnetic excitations (sk1 to sk5) for each disk at a specific harmonic, Calculating a weighted sum (S0) from the individual electromagnetic excitations (sk1 to sk5) for the entire electrical machine, wherein in the weighted sum (S0) the electromagnetic excitations (sk1 to sk5) are weighted according to a proportion of the disks in the electrical machine, Dividing the electric machine into two groups, each corresponding to half the length of the electric machine, and calculating a respective weighted sum (SD1_1, SD1_2) of the individual electromagnetic excitations (sk1 to sk5) for the two groups, wherein in the weighted sums (SD1_1, SD1_2) the electromagnetic excitations (sk1 to sk5) are weighted according to a proportion of the disks in the respective of the two groups, Calculating differences (S1_1, S1_2) according to the following formulas: S1_1=SD1_1−S0, S1_2=SD1_2−S0, Determining an average size (S1) of the differences (S1_1, S1_2), Dividing the electric machine into four groups, each corresponding to a quarter of the length of the electric machine, and calculating a respective weighted sum (SD2_1 to SD2_4) of the individual electromagnetic excitations (sk1 to sk5) for the four groups, wherein in the weighted sums (SD2_1 to SD2_4) the electromagnetic excitations (sk1 to sk5) are weighted according to a proportion of the disks in the respective of the four groups, Calculating differences (S2_1 to S2_4) according to the following formulas: S2_1=SD2_1−S1_1 S2_2=SD2_2−S1_1 S2_3=SD2_3−S1_2 S2_4=SD2_4−S1_2 Determining an average size (S2) of the differences (S2_1 to S2_4), and Evaluating the NVH behavior of the electric machine based on the size of the weighted sum (S0) and the average sizes (S1 and S2). [2] The method of claim 1, comprising: Calculating an angle (alpha_o1) between the vector (S1_1, S0) and the vector (S1_2, S0), taking the angle (alpha_o1) into account when evaluating the NVH behavior. [3] The method of claim 2, comprising: Issue a warning if the angle (alpha_o1) deviates from 180°. [4] Method according to any one of claims 1 to 3, comprising: Calculating an angle (alpha_o2_1) between the vector (S2_1, S1_1) and the vector (S2_2, S1_1), taking the angle (alpha_o2_1) into account when evaluating the NVH behavior. [5] A method according to any one of claims 1 to 4, comprising: Calculating an angle (alpha_o2_2) between the vector (S2_3, S1_2) and the vector (S2_4, S1_2), taking the angle (alpha_o2_2) into account when evaluating the NVH behavior. [6] A method according to any one of claims 1 to 5, comprising: Calculating an angle (beta_o2) between the vector (S2_1, S2_2) and the vector (S2_3, S1_4), taking the angle (beta_o2) into account when evaluating the NVH behavior. [7] Method according to any one of claims 1 to 6, comprising: Modify the design of the electrical machine and repeat the steps of the procedure for evaluating the NVH behavior of the modified design. [8] Method according to any one of claims 1 to 7, wherein the method is carried out for a plurality of harmonics. [9] Method according to any one of claims 1 to 8, comprising: Output of the design of the electrical machine in which the NVH behavior is optimized or has the desired characteristics, in order to manufacture the electrical machine accordingly. [10] Computing unit which is trained and programmed to execute the method according to claims 1 to 9.

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