Method and device for determining a level of noise and electromagnetic vibrations

Abstract

The present invention relates to a method and device for determining a level of noise and electromagnetic vibrations in a machine with an electric motor. To this end, computer means obtain (31, 32) a set of loading cases and eigenmodes of the machine, determine (33) a significant subset, obtain (34) a set of relevant nodes and calculate (35) a set of frequency response functions restricted to the relevant nodes, obtain (36, 37) a set of operating points and magnetic states of the machine, determine (38) a set of operational loads of the machine, then determine (39) a level of noise and electromagnetic vibrations on the basis of the frequency response functions and the operational loads.

Description

[0001] Description

[0002] Title: Method and device for determining a level of noise and vibrations of electromagnetic origin

[0003] Technical field

[0004] The present invention relates to the virtual prototyping of electrical systems emitting acoustic noise of electromagnetic origin.

[0005] The present invention relates more particularly to a method for determining a level of noise and vibrations of electromagnetic origin of a machine comprising an electric motor.

[0006] The present invention also relates to a device implementing such a method.

[0007] The present invention additionally relates to the design of electric motor machines, implementing such a method.

[0008] The invention will thus find numerous advantageous applications in the design of electrical machines used in sectors such as transport (automobile, rail, naval), industry, energy, medical and domestic applications.

[0009] Prior art

[0010] All mechanical systems produce noise. Very often, resonance phenomena between structural modes and excitation forces are the main cause or a significant contributor to the noise and vibration problem. These resonance phenomena are caused by a specific component of the system, or by the entire system or structure.

[0011] These noise and vibration phenomena are observed on machines in operation, particularly during rotational movement for rotating machines. A high noise or vibration level can result in a loss of acoustic comfort or handling, or even health problems in the event of prolonged exposure to noise, and also generates breakdowns and breakages due to fatigue of the physical structure of the system.

[0012] In the simplest cases, the origin of resonant vibrations can be identified empirically (e.g., a problem with tightening mechanical parts), or the noise can be limited by adapting the structure of the system appropriately (e.g., adding acoustic cover). This origin quickly becomes more complex to identify in the case of noise of electromagnetic origin due to the complexity of the excitation forces involved. The Applicant observes that the solutions proposed to date for predicting vibrations of magnetic origin of a given machine are based on a numerical simulation coupling different finite element software for generic use in the fields of low-frequency electromagnetism, structural dynamics and linear acoustics.These solutions thus provide in a first step an exhaustive calculation of magnetic forces at variable speed, in a second step a calculation of vibrations by modal expansion, and in a third step an evaluation of acoustic radiation around the machine. These solutions make it possible to obtain precise results on the level of vibrations generated by a given machine, but require a very significant calculation time, of the order of 15 hours per machine. Such an approach is thus incompatible with the design phases of electrical machines, since each iteration or design change requires a time-consuming simulation in order to estimate its electromagnetic noise. The Applicant also submits that other complementary approaches have been developed, based on the approximate calculation of magnetic forces or on electromagnetic vibration synthesis, and making it possible to use the linearity of the structures to accelerate calculation times.These can thus be reduced to around 1.5 hours in the simplest cases.

[0013] The Applicant submits, however, that these calculations remain cumbersome, take up a significant amount of memory space, and become even more cumbersome in cases of complex loading, for example in the case of a twisted rotor machine. In addition, these solutions only allow for a final estimate of the total noise generated by the machine. It is therefore difficult to identify how to reduce noise, and improving the design of the machine requires multiplying the simulations in order to find a solution to minimize noise.

[0014] The Applicant thus submits that the current solutions present very long calculation times incompatible with an iterative design approach, a significant memory footprint both during calculations (on RAM) and at the output of the calculation (on the hard disk), a vulnerability to digital noise in the results due to mesh projections, digital interpolations and spectral spreading, and do not provide information or differentiation on the origin of noise and vibrations of magnetic origin.

[0015] The Applicant therefore submits that the solutions for determining a level of noise and vibrations of electromagnetic origin are not satisfactory and in particular unsuitable for industrial design and prototyping needs. Summary of the invention

[0016] The present invention aims to improve the situation described above.

[0017] The present invention aims in particular to overcome the above drawbacks by proposing a method and a device for determining noise of magnetic origin making it possible to integrate such a determination within design phases, so as to provide a tool simplifying and assisting the design of electric motor machines, without slowing it down. According to a first aspect, the subject of the present invention relates to a method for determining a level of noise and vibrations of electromagnetic origin of an electric motor machine having a mechanical structure, said machine comprising a rotor and a stator, said rotor and said stator being separated by an air gap, the method being implemented by at least one processor, the method comprising the following steps:

[0018] - obtaining a first data representative of a set of loading cases associated with the machine, each loading case corresponding to a component of a magnetic loading according to a decomposition on a mathematical basis, preferably in Fourier series;

[0019] - obtaining a second data representative of a set of natural modes of the mechanical structure;

[0020] - determination, from the set of loading cases and the set of eigenmodes, of a subset of significant loading cases and eigenmodes;

[0021] - obtaining a third data representative of a set of relevant nodes associated with the mechanical structure;

[0022] - calculation of a set of frequency response functions, by modal expansion restricted to the set of relevant nodes and to the subset of loading cases and significant eigenmodes;

[0023] - obtaining a fourth data representative of a first set of operating points of the machine, each operating point being associated with a torque and a speed of the machine;

[0024] - obtaining a fifth data item representative of a set of magnetic states of the machine, each magnetic state of the set of magnetic states being associated with an operating point;

[0025] - determination of a set of operational loadings from the set of magnetic states; and

[0026] - determination of information representative of a noise and vibration level of electromagnetic origin of the machine from the set of operational loads and the set of frequency response functions.

[0027] It is understood here that the loading cases correspond to the components of the forces applied to the electrical machine, in particular at different points of the rotor and the stator. The magnetic loadings of the electrical machine are for example defined from the design parameters of the electrical machine, that is to say they result from the structure of the magnetic circuit of the electrical machine. The loading cases are associated with an amplitude or an operational level fixed arbitrarily, for example a unit loading, that is to say associated with an amplitude of IN, so as to simplify the calculations. Each loading case includes for example all of the following information:

[0028] - a type of loading: force or torque;

[0029] - a direction of application, for example for a force: radial, circumferential, axial;

[0030] - an application structure: rotor or stator; and

[0031] - a wave number: r=0, 1, 2, etc.

[0032] According to a particular exemplary embodiment, the set of loading cases is restricted to the lowest wave numbers existing in the machine, for example only the excitations of wave number r=0. The person skilled in the art understands that the lowest wave numbers are associated with the most significant excitations, this restriction can thus limit unnecessary calculations without impacting the accuracy of the results.

[0033] It is further understood that the set of natural modes corresponds to a representation of the harmonic vibration behavior of the machine in a manner appropriate for a vibration analysis. Each natural mode is for example characterized by a modal deformation, a natural frequency and a modal damping. The person skilled in the art understands here that any response to an excitation will correspond to a unique linear combination of the natural modes. The determination of the subset of significant loading cases and natural modes corresponds to an identification of the combinations between loading cases and natural modes resulting in significant vibrations. In other words, this determination makes it possible, for each loading case, to identify the mode(s) whose shape is closest to the loading case.This design thus makes it possible to reduce the set of loading cases and the set of modes specific to the elements contributing significantly to noise of electromagnetic origin, and therefore to avoid unnecessary calculations.

[0034] It is also understood that the set of relevant nodes corresponds to a reduction, with respect to the set of nodes resulting from a mesh of the machine structure, to the nodes relevant for the calculation. These nodes may be relevant for the visualization of the modes of interest, for carrying out the calculation, or for the verification of design criteria, for example vibration standards. The relevant nodes are for example reduced to the level of the tooth heads of the electric motor where the majority of the magnetic forces apply, to the attachment points of the machine where vibration design criteria apply, and to the envelope points of the structure whose normal vibration is responsible for the acoustic radiation.The modal shapes of the eigenmodes of the subset determined above are reduced to this set of relevant nodes, i.e. the modal shapes are calculated, when calculating the set of frequency response functions, only for the set of relevant nodes.

[0035] The person skilled in the art understands that the set of frequency response functions makes it possible to obtain, for each node of the set of relevant nodes, for example the amplitude of the vibrations or even an amplitude of acoustic pressure under the effect of the loading cases applied to the natural modes.

[0036] The principle of modal expansion is known from the state of the art and represents a considerable source of computation time, in particular at high frequencies where the modal density is greater, its restriction to the relevant modes, to the relevant excitations and to the relevant nodes thus makes it possible to greatly limit the computation time and the memory load associated with the determination of the noise, without impacting the accuracy of the results.

[0037] This first set of steps thus makes it possible to characterize the structure of the electrical machine and its vibratory behavior.

[0038] In a second step, or for example in parallel with the first set of steps, a second set of steps allows to characterize the operational stress levels of the machine, i.e. the complex amplitude (norm and phase) of each case of magnetic loading applied to the machine along its operating points.

[0039] It is thus understood that the set of operating points, that is to say the combination of torque and speed of the electric motor, corresponds to a variety of regimes according to which the machine is likely to operate. The set of magnetic states thus corresponds to the flux generated and / or the forces in the machine when it operates in accordance with a given operating point.

[0040] Each magnetic state comprises, for example, a magnetic force torque per stator tooth, comprising a radial force, a circumferential force and a moment. Thus, the set of magnetic states makes it possible to determine a set of operational levels and to evaluate the intensity, for example in N, of a given load according to an operating point. In other words, the set of magnetic states corresponds to a set of excitation forces respectively associated with the operating points.

[0041] The set of operational loads can thus be determined as a function of the set of magnetic states, for example by integrating the Maxwell tensor over a tooth pitch from the magnetic flux distribution in the middle of the air gap. Another more precise way to calculate the operational load is to apply the virtual work method from the magnetic field distribution on the magnetic mesh, then to integrate the torsor of the forces per tooth. Independently of the method of calculating the magnetic force torsor chosen, a Fourier series decomposition of the torsors is carried out in order to determine, for each loading case (e.g. radial force of wave number r=0 applied to the stator) and each operating point, an amplitude in N and a phase in radians.Thus, the determination of the information representative of the level of noise and vibrations of electromagnetic origin corresponds to a matching of the frequency response functions, i.e. the vibrations generated by unit loads, with the operational loads, i.e. the intensity of the loads during operation of the machine.

[0042] The information representative of the level of noise and vibrations of electromagnetic origin therefore includes a level of noise and vibrations as a function of the operating points, i.e. combinations of torque and speed, making it possible to identify the operating points generating noise. It is therefore possible, from this information, to adapt the control of the electrical machine in such a way as to avoid the most significant vibrations, and minimize noise and the risks of breakdown.

[0043] The Applicant thus submits that, thanks to the present invention, the determination of the level of noise and vibrations of magnetic origin of an electrical machine is simplified with reduced calculation times, by only performing calculations on a reduced number of nodes, natural modes and loading cases, making it possible to efficiently integrate electromagnetic vibration analysis into an electrical machine design process. In an advantageous embodiment of the invention, the method further comprises a display, via a human-machine interface, of information belonging to a set of information comprising:

[0044] - information representative of the noise and vibration level;

[0045] - information representative of the subset of significant loading cases and natural modes; and

[0046] - information representative of the set of frequency response functions. It is understood here that the display of the representative information corresponds to a rendering, preferably visual or graphic, of the noise and vibration level determined during the process or other relevant elements that can assist the design process of the electrical machine. Obviously, such a display depends on the representative information determined, in particular its level of detail. The method according to the invention makes it possible, for example, to estimate, in particular with respect to the embodiment variants described below, an overall level of noise or vibration generated by the machine, globally or according to determined points or surfaces, or a specific level of noise or vibration resulting from a mode and / or a loading case considered, according to the operational levels determined during the execution of the method.According to another variant, the method according to the invention makes it possible to estimate a coefficient representative of a correspondence between the loading cases and the eigenmodes of the subset of loading cases and eigenmodes, for example via a projection as described below. The display then corresponds for example to the display of a set of projections between the loading cases and the eigenmodes, from which the subset of loading cases and eigenmodes is determined. It is further understood that the method can be configured for the display of a variety of quantities or functions determined during the execution of the method, in particular the frequency response functions associated with a plurality of loading cases.

[0047] In a particular embodiment, the method further comprises receiving information representative of a set of magnetic loads associated with the machine, and obtaining the first data corresponds to determining the set of loading cases associated with the machine from the set of magnetic loads.

[0048] It is understood here that the method determines the set of loading cases by following the principle of a decomposition on a mathematical basis, applied to the set of magnetic loads. The decomposition corresponds for example to a Fourier series decomposition or on any other mathematical basis known to those skilled in the art. The set of magnetic loads is for example defined by a set of analytical equations on the structure of the forces, characterizing the frequency and the wave number of the rotor and stator loads according to the type of electrical machine and its fault state.

[0049] According to another example, the information representative of the set of magnetic charges includes:

[0050] - information representative of a number of stator slots of the machine; - information representative of a number of pole pairs of the machine; and

[0051] - information representative of a number of machine phases.

[0052] It is understood that such information corresponds to discrete design parameters of the electric machine, from which the analytical equations of the spectral support of the loads can be established.

[0053] According to an alternative variant, obtaining the first data corresponds to a direct reception of the set of loading cases, for example determined analytically outside the execution of the process.

[0054] In an additional embodiment, the method further comprises receiving information representative of the mechanical structure, and obtaining the second data item corresponds to determining the set of eigenmodes from the structure. Those skilled in the art understand here that determining the set of eigenmodes from the structure is carried out, for example, analytically by modeling the stator by an equivalent cylinder or, more precisely, using a beam model, in which the teeth and the yoke of the stator are modeled as beam elements. The information representative of the structure of the machine corresponds, for example, to a model of the machine or to a set of parameters representative of the machine allowing its modeling.

[0055] According to other embodiment variants, the set of natural modes is received by the method and determined outside of its execution by methods known to those skilled in the art.

[0056] The set of eigenmodes is in this case, for example, determined by a calculation using mechanical finite elements, i.e. via a resolution of an eigenvalue problem from stiffness and mass matrices of the machine, or even measured via an experimental modal analysis.

[0057] In an additional embodiment, the method comprises the following steps:

[0058] - determination of a set of projections between the loading cases and the eigenmodes, each projection of the set of projections being associated with a loading case and an eigenmode; and

[0059] - comparison of each projection of the set of projections with a threshold value, the subset of significant loading cases and eigenmodes being determined based on a result of the comparison.

[0060] In other words, each significant combination of a load case and an eigenmode is identified when the projection of the load case with the eigenmode exceeds a threshold value. Load cases and eigenmodes are for example represented in the form of representative vectors, each projection corresponding to a scalar product between the two vectors.

[0061] We therefore understand here that a projection exceeding the threshold value corresponds to a combination of a loading case and a natural mode whose shapes are similar, that is to say to an excitation entering into spatial resonance with a determined structural mode.

[0062] Comparing each projection in the set of projections with a threshold value allows, for example, the formation of a subset of significant projections, and by extension a subset of significant loading cases and eigenmodes.

[0063] According to yet another variant, the calculation of the set of projections makes it possible to identify, for each force, for example each case of structure with wave number r=0, the mode whose form is closest to this force, that is to say the mode for which the projection with the loading case is the highest.

[0064] In yet another embodiment, the method further comprises determining a set of resonant velocities from the subset of loading cases and significant eigenmodes, each resonant velocity being associated with an eigenmode of the subset, and wherein the first set of operating points is associated with the set of resonant velocities.

[0065] It is understood here that the determination of the subset of significant loading cases and eigenmodes makes it possible to determine one or more speeds for which the combination of the loading case and the eigenmode enters into resonance. Each eigenmode is for example associated with a specific frequency or pulsation, from which a resonance speed can be determined, for example via the analytical equations described above.

[0066] The association of the first set of operating points with the resonance speeds, that is to say by including operating points whose speed corresponds to the resonance speeds, thus makes it possible to ensure that the calculations are carried out with respect to the speeds that generate the most noise and vibrations, and therefore makes it possible to ensure an accurate calculation. The first set of operating points is for example expanded so as to include each identified resonance speed, so as to increase the accuracy of the calculation and / or restricted only to the operating points associated with the identified resonance speeds to minimize the calculation time as much as possible.

[0067] In another embodiment that can be combined with the previous embodiments, the method further comprises determining a set of cross-projection coefficients between the loading cases, each cross-projection coefficient being associated with a combination of two loading cases from the set of loading cases, the information representative of the level of electromagnetic noise and vibration being further determined as a function of the set of cross-projection coefficients.

[0068] The Applicant submits that the use of cross-projection coefficients makes it possible to obtain a plurality of coefficients independent of the operational loads, involved in the expression of the mean quadratic vibration speed of the envelope, representative of the overall noise level, and therefore to limit the calculations at the level of determining the information representative of the level of noise and vibrations of electromagnetic origin, that is to say to simplify the matching of the response functions and the operational loads. The determination of the set of cross-projection coefficients thus makes it possible to reduce the total number of calculations at variable speed and to facilitate the processing of a large number of operating points. The cross-projection coefficients correspond for example, like the set of projections described above, to scalar products between the vectors representative of the loading cases.The cross-projection coefficients are, for example, advantageously determined only for the loading cases of the subset of loading cases and natural modes described above, or more generally only for the loading cases taken into account in the determination of the level of noise and vibrations of electromagnetic origin.

[0069] In yet another embodiment, the method further comprises obtaining a sixth piece of data representative of a set of radiation factors, each radiation factor being associated with a natural mode of the set of natural modes, the information representative of the level of noise and vibrations of electromagnetic origin being further determined as a function of the sixth piece of data.

[0070] The Applicant submits that the use of radiation factors, associated with each natural mode, makes it possible to refine the calculations, in particular of power and acoustic pressure, i.e. information representative of the noise and vibration level. The accuracy of the results obtained is therefore improved, in particular in the context of low frequencies. According to another example, the radiation factors are only used in the context of excitation frequencies below a given threshold.

[0071] As stated above, the set of radiation factors is for example obtained only for the eigenmodes belonging to the subset of loading cases and significant eigenmodes. Preferably, the method further comprises receiving information representative of the mechanical structure, and obtaining the sixth data corresponds to determining the set of radiation factors from the structure.

[0072] The Applicant submits that the set of radiation factors can be determined analytically in the execution of the method, for example by modeling the stator by equivalent cylinder.

[0073] The person skilled in the art also understands that the set of radiation factors can be calculated by acoustic finite elements, from the modal deformation of each natural mode.

[0074] The set of radiation factors is for example received directly, in parallel with the set of eigenmodes, or determined from the same representative structure information as the eigenmodes, for example in parallel with the determination of the eigenmodes, or at a later time, once the eigenmodes have been reduced to the subset.

[0075] In one implementation, the set of relevant nodes includes a first subset of nodes for which magnetic forces are applied to the rotor and stator, a second subset of nodes generating acoustic noise radiation, and a third subset of isolated interface nodes.

[0076] The Applicant submits that these three subsets correspond to nodes that are important for the calculations, the set of relevant nodes being, for example, determined by identifying and grouping these three subsets. It is further understood that the set of relevant nodes may be determined in other ways according to the requirements and knowledge of the person skilled in the art, so as to take into account the nodes whose behavior is important for the calculation of vibrations.

[0077] In a particular implementation mode, the set of frequency response functions comprises a set of response functions per load and optionally per eigenmode of the subset of significant loading cases and eigenmodes, the information representative of the level of noise and vibrations of electromagnetic origin of the machine being determined separately for each loading case and optionally for each eigenmode.

[0078] The Applicant submits here that the set of frequency response functions corresponds, in the modal expansion carried out by the method, to a linear combination, for example a finite sum of responses per loading case and per eigenmode. This design thus makes it possible to calculate separately the responses per loading case or even the responses per loading case and per eigenmode, so as to determine and identify the level of noise and vibrations generated specifically by each loading case and optionally by each eigenmode, then the total noise level generated by their combination.

[0079] This combination provides in particular a more detailed analysis of the origin of the noise. A user is then able to identify, for each operating point, the loading cases and / or natural modes generating vibration, and consequently to adapt the design of the electrical machine in order to attenuate them specifically. The user therefore understands which type of force excites which type of mode and can act both on the excitation, for example by adapting the design of the machine's magnetic circuit, and on the structure, for example by shifting a particular natural frequency, in order to reduce noise and vibrations.

[0080] In an additional embodiment, the set of frequency response functions comprises a set of acoustic frequency response functions. In other words, the frequency response functions correspond to an acoustic pressure response under a given loading, for example unit. The frequency response functions are then calculated in the acoustic domain.

[0081] In another embodiment, the set of frequency response functions comprises a set of vibrational frequency response functions.

[0082] In other words, frequency response functions correspond to a vibration response under the effect of a given loading.

[0083] Of course, it is further understood that the determination of the information representative of the noise and vibration level of electromagnetic origin of the machine is carried out according to the determined frequency response functions. In the context of acoustic frequency response functions, the information representative of the noise and vibration level corresponds for example to an acoustic pressure field under the effect of operational excitation. The acoustic frequency response functions are for example determined on an acoustic mesh, once again restricted to the set of nodes relevant to the person skilled in the art (e.g.: points surrounding the machine for calculating the acoustic power according to the standard in force).On the contrary, in the context of vibration frequency response functions, the information representative of the noise and vibration level corresponds, for example, to a mean square vibration associated with at least one part of the machine. It is also possible to determine a set of frequency response functions comprising both a set of acoustic frequency response functions and a set of vibration frequency response functions. This design corresponds, for example, to a combined mechanical-acoustic calculation, or, by combination with the variants described above, to an acoustic calculation separate from a radiation calculation, the radiation being combined with the vibration frequency response functions to obtain the set of acoustic frequency response functions.

[0084] In an additional embodiment, the method further comprises receiving information representative of a second set of operation points of the machine, and wherein obtaining the first set of operation points comprises processing the second set of operation points.

[0085] It is understood here that the second set of operating points corresponds to a set of points imported for the execution of the method, the generation of the first set of operating points making it possible to supplement and / or reduce the number and nature of the operating points, for example so as to bring the operating points into correspondence with the resonance speeds determined above or to reduce the operating points and the associated calculations. The determination of additional operating points is carried out for example by interpolation or extrapolation from the second set of operating points.

[0086] In an implementation mode that can be combined with the previous mode, the set of magnetic states is obtained from the first set of operation points.

[0087] It is understood here that the magnetic states correspond to the magnetic field in the machine, associated with the operating points. The magnetic state of the machine can be calculated in a plurality of ways, for example by magnetic finite elements, by the permeance or magnetomotive force method, by reluctance networks, or even by equivalent electrical circuits. The magnetic states then make it possible to determine the operational loads associated with the operating points, for example according to the methods described above of the Maxwell tensor or virtual work.

[0088] In a particular design, the method comprises receiving information representative of the magnetic states, for example, directly receiving the fifth data, or receiving a distribution of the magnetic flux in the air gap, from which the method determines the magnetic force torsors on the stator teeth, for example by the Maxwell tensor method. Over certain operating ranges, the amplitude of the magnetic loadings may be known as constant or variable. Thus, the determination of all the magnetic states, as well as the operating points, may comprise an extrapolation, the method determining the magnetic state of the machine over a single operating point of the range and extrapolating the amplitude and frequencies of the excitation harmonics over the operating range, or an interpolation between two known operating points.Obviously, the operating points used for interpolation are chosen so as to minimize the error made, i.e. the inaccuracy, during interpolation. It is further understood that the use of interpolation and / or extrapolations over specific ranges further minimizes the computational load, the identification of such ranges ensuring that the accuracy of the results is not impacted. For example, it is known that the amplitude of magnetic loads can be constant over operating ranges of constant flux asynchronous machines, open circuit magnet machines or constant current angle machines.

[0089] According to another embodiment, the first set of operating points and the set of magnetic states associated with the operating points are both imported directly, the magnetic states being for example determined outside the execution of the magnetic finite element method.

[0090] In yet another embodiment, the method further comprises receiving information representative of a selection of an objective belonging to a set of objectives comprising:

[0091] - a mean square vibration of a machine surface;

[0092] - a mean square vibration of at least one node of the machine; and

[0093] - acoustic power radiated by part or all of the machine, the information representative of the level of noise and vibrations of electromagnetic origin of the machine being further determined according to the selection.

[0094] It is understood here that it is possible, via the execution of the method according to the invention, to obtain a plurality of information items each being representative of the level of noise and vibrations of electromagnetic origin, the use and usefulness of which may vary depending on the application cases. In particular, a user may seek to obtain a result on a restricted portion of the machine, resulting from the vibratory behavior of the entire machine, for example a surface or a given point. This design thus makes it possible to determine precisely what level of noise and vibrations to determine during the execution of the method, in particular for a display of this information in accordance with the variant described above.

[0095] According to a second aspect, the present invention relates to a device for determining a level of noise and vibrations of electromagnetic origin of an electric motor machine, the device comprising a memory associated with a processor configured for implementing the steps of the method according to the first aspect of the present invention.

[0096] According to a third aspect, the present invention relates to a computer program which comprises instructions adapted for executing the steps of the method according to the first aspect of the present invention, in particular when the computer program is executed by at least one processor.

[0097] According to a fourth aspect, the present invention relates to a computer-readable recording medium on which is recorded a computer program comprising instructions for carrying out the steps of the method according to the first aspect of the invention. On the one hand, the recording medium may be any entity or device capable of storing the program. For example, the medium may comprise a storage means, such as a ROM memory, a CD-ROM or a microelectronic circuit type ROM memory, or else a magnetic recording means or a hard disk.

[0098] Furthermore, this recording medium may also be a transmissible medium such as an electrical or optical signal, such a signal being able to be conveyed via an electrical or optical cable, by conventional or hertzian radio or by self-directed laser beam or by other means. The computer program according to the present invention may in particular be downloaded from a network such as the Internet.

[0099] Alternatively, the recording medium may be an integrated circuit in which the computer program is incorporated, the integrated circuit being adapted to perform or to be used in performing the method in question.

[0100] According to a fifth aspect, the present invention relates to a use of the method according to the first aspect of the present invention for the design of an electric motor machine. It is understood here that the design of an electric motor machine comprises the production of a plurality of prototypes or models of machines, for which it is advantageous to determine as early as possible the magnetic (e.g.: torque, losses) and vibro-acoustic behavior, in order to identify and correct any defects, in particular by adapting the magnetic excitation and / or the physical structure, while minimizing investments and manufacturing costs.

[0101] The method according to the present invention thus allows a speed of execution which makes it possible to launch sensitivity and optimization studies, that is to say the integration of the method in a design phase, on an industrial scale, of electric motor machines.

[0102] Thus, through the various functional and structural technical characteristics above, the Applicant proposes a method and a device for determining a level of noise and vibrations of electromagnetic origin of an electric motor machine allowing a significant reduction in calculation time and integration into an industrial process for designing and / or prototyping an electric motor machine.

[0103] Brief description of the figures

[0104] Other characteristics and advantages of the present invention will emerge from the description of the particular and non-limiting exemplary embodiments of the present invention below, with reference to the appended figures 1 to 6, and in which:

[0105] [Fig- 1]

[0106] Figure 1 illustrates the structure and mechanical mesh of an electric motor machine, according to a particular and non-limiting exemplary embodiment of the present invention;

[0107] [Fig- 2]

[0108] Figure 2 schematically illustrates a device configured to determine a level of noise and vibrations of electromagnetic origin of the machine of Figure 1, according to a particular and non-limiting exemplary embodiment of the present invention;

[0109] [Fig- 3]

[0110] Figure 3 illustrates a flowchart of the different steps of a method for determining a level of noise and vibrations of electromagnetic origin of the machine of Figure 1, according to a particular and non-limiting exemplary embodiment of the present invention;

[0111] [Fig. 4]

[0112] Figure 4 illustrates a first graph representative of a level of noise and vibrations of electromagnetic origin of the machine of Figure 1, determined by a method in accordance with Figure 3;

[0113] [Fig. 5] Figure 5 illustrates a second graph representative of a level of noise and vibrations of electromagnetic origin of the machine of Figure 1, determined by a method in accordance with Figure 3;

[0114] [Fig- 6]

[0115] Figure 6 illustrates a third representative graph of a level of noise and vibrations of electromagnetic origin of the machine of Figure 1, determined by a method in accordance with Figure 3.

[0116] Description of examples of implementation

[0117] A method and a device for determining a level of noise and vibrations of electromagnetic origin of an electric motor machine will now be described in the following with joint reference to figures 1 to 6. The same elements are identified with the same reference signs throughout the description which follows.

[0118] As indicated in the preamble to the description, current solutions for determining noise of electromagnetic origin correspond to generic software, not adapted to this particular task, whose calculation times are considerable and unsuitable for industrial needs.

[0119] One of the objectives of the present invention is to propose a determination of the level of noise and vibrations of electromagnetic origin, the operation of which is adapted to its integration into the design of an electrical machine, in particular within sensitivity and optimization studies.

[0120] This is made possible in the example described below, which considers a use of the method according to the invention in a design phase of an electrical machine.

[0121] It will be understood here that this example is not limiting and that the method according to the invention can be integrated into a variety of different phases involving the vibration analysis of an electric motor machine.

[0122] According to the example of Figure 1, a machine 1 includes an electric motor, comprising a rotor 11 and a stator 12 separated by an air gap 13. The machine 1 corresponds for example to a model of an electric machine in the design phase, or to a physical prototype whose vibration behavior is to be studied in detail, for example in order to identify more precisely the sources of its vibrations. The machine 1 corresponds for example to a synchronous machine, to an asynchronous machine, or to a variable reluctance machine. Of course, according to other examples, the machine 1 can comprise several rotors 11 and / or several stators 12. A rotating electric machine generally consists of two main parts: the rotor 11 and the stator 12, the connection of which is ensured by a bearing. The air gap 13 designates the space located between the rotor 11 and the stator 12, the electromechanical conversion taking place in the air gap.The electrical machine may contain several rotors and several stators, which does not change the method described except for the number of magnetic loading cases. The stator 12 is a fixed part which is made of ferromagnetic material and which comprises so-called stator slots 12a, 12b, 12c filled by a winding; this winding is connected to a source capable of electrically supplying the winding of the stator 12 with so-called stator currents. These stator currents create a rotating magnetic field in the air gap 13 of the machine 1.

[0123] The rotor 11 is a long, elongated part which is made of ferromagnetic material and which is capable of rotating on itself along its longitudinal axis, for example around a shaft 15.

[0124] According to the example of figure 1, the machine 1 corresponds to a synchronous machine with magnets 14, the stator slots 12a, 12b, 12c comprising a first set of slots 12a associated with a first phase, a second set of slots 12b associated with a second phase and a third set of slots 12c associated with a third phase.

[0125] In another example, the machine 1 corresponds to an asynchronous machine. In such an example, the rotor 11 comprises so-called rotor slots filled by a winding traversed by currents, called rotor currents, which are induced by the fluctuations of the magnetic field generated by the stator 12.

[0126] During the operation of the machine 1, i.e. the operation of the electric motor, the rotor 11 begins to rotate in an attempt to follow the magnetic field generated by the stator 12 according to the Lenz-Faraday law. In an asynchronous machine, the mechanical rotational speed of the rotor 11 differs slightly from the rotational speed of the stator field, while in a synchronous machine, the rotor 11 rotates synchronously with the magnetic field of the stator 12.

[0127] The electromagnetic forces at the origin of the torque in the air gap 13 are also at the origin of vibrations and acoustic noise: the forces generated deform the structures of the rotor 11 and the stator 12 and propagate more generally to the entire physical structure of the machine 1. The vibrations generated can, on the one hand, propagate to the ambient air and radiate in the audible frequencies, representing a source of discomfort, on the other hand generate mechanical fatigue which can be harmful for applications where the operation of the machines must be guaranteed over long periods, for example for hydroelectric or wind generators.

[0128] These electromagnetic forces come mainly from the interaction between the different groups of magnetic flux harmonics (Maxwell forces); the magnetic flux harmonics themselves come from the interaction between different harmonics known as magnetic permeance and magnetomotive force.

[0129] It therefore appears that resolving and identifying sources of electromagnetic vibration, or more simply determining whether a given machine is likely to generate vibrations, represents a complex problem, particularly during the preliminary design phases. While there are currently combinations of software solutions available to estimate the electromagnetic noise of a given machine, these are complex and particularly time-consuming.

[0130] In order to propose a solution to this problem, the machine 1 is associated with computer means configured for the implementation of a method for determining its level of noise and vibrations of electromagnetic origin, for example the method of figure 3. As illustrated in figure 2, such computer means are for example advantageously grouped in an electronic device 2, for example a computer (hereinafter referred to as "computer"). The computer 2 is for example configured to transmit and receive data within a communication network. The elements of the computer 2, individually or in combination, can be integrated in a single integrated circuit, in several integrated circuits, and / or in discrete components. The computer 2 can be produced in the form of electronic circuits or software (or computer) modules or even a combination of electronic circuits and software modules.

[0131] The computer 2 comprises one (or more) processor(s) configured to execute instructions for carrying out the steps of the method and / or for executing the instructions of the software(s) embedded in the computer 2. The processor may include integrated memory, an input / output interface, and various circuits known to those skilled in the art. The computer 2 further comprises at least one memory corresponding for example to a volatile and / or non-volatile memory and / or comprises a memory storage device which may comprise volatile and / or non-volatile memory, such as EEPROM, ROM, PROM, RAM, DRAM, SRAM, flash, magnetic or optical disk.

[0132] The computer code of the embedded software(s) comprising the instructions to be loaded and executed by the processor is for example stored in the memory of the computer 2. According to an alternative embodiment, the computer 2 is configured for the implementation of a method for determining a level of noise and vibrations of electromagnetic origin forming part of a broader method, for example a method for designing an electric motor machine, in which the quantities calculated during the method according to the invention, for example the acoustic power or the level of noise and vibrations per loading case and optionally per natural mode below, are according to this example calculated at each iteration of the design method.The method according to the invention can also, according to another example, be carried out iteratively for a plurality of machines 1 corresponding to different designs, so as to provide a comparison between the different designs. The method for designing an electric motor machine comprises, for example, the creation of the model of the machine 1, the information associated with the model being recorded in a memory 20 of the computer 2.

[0133] In a first step 31 of the method for determining the noise and vibration level, the computer 2 obtains a first data item representative of a set of loading cases associated with the machine 1. Each loading case here corresponds to a component of a magnetic loading according to a decomposition on a mathematical basis, for example in Fourier series. Preferably, each loading case corresponds to a unit loading and is characterized by a type of loading, a direction of application, an application structure and a wave number r. For example, a magnetic loading case corresponds to a radial force on the rotor of spatial frequency r=0.

[0134] The first data is for example received by a beacon unit 22 of the computer 2, for example a beacon unit 22 in communication with a human-machine interface 220 of the computer 2. The computer 2 forms for example a communication network, for example a multiplexed communication network, in which data is transmitted via a wireless or wired link. The computer 2 therefore establishes communication between the human-machine interface 220, serving as a data acquisition peripheral, and the beacon unit 22 so as to allow the exchange of data.

[0135] According to another example in accordance with the variant described above, the first data is obtained from the memory 20 of the computer 2. The first data corresponds in these two cases to an input data, the set of loading cases having been determined outside the execution of the method, for example analytically.

[0136] According to an alternative embodiment, the computer 2 receives, for example via the beacon unit 22 or the memory 20, information representative of a set of magnetic loads associated with the machine 1. A processor 21 of the computer then determines the set of loading cases associated with the machine 1 from the set of magnetic loads. The information representative of the set of magnetic loads corresponds for example to a set of analytical equations, making it possible to characterize the frequency and the wave number of the effective loads, for example as a function of the type of machine 1, and / or to parameters of these analytical equations. Such analytical equations are further established from discrete design parameters of the machine 1.

[0137] According to an exemplary embodiment, an open circuit permanent magnet machine is associated with the following analytical equations: f = h r 2fe

[0138] With r the wave number of the load, f the frequency of the load, k s and h r two relative integers resulting from the Fourier series decomposition of the magnetic flux, f e the electrical frequency proportional to the operating speed, Z s the number of stator slots 12 and p the number of pole pairs of the machine. The term modulo [Z s / 2] relates to the wave numbers of the forces seen by the stator teeth due to the spatial sampling phenomenon.

[0139] For example, in the context of a machine 1 for which: [Math 3]

[0140] [Math 4]

[0141] Z s = 48

[0142] Machine 1 contains an excitation of wave number:

[0143] [Math 5] r = 0 = 48 — 6 * 8

[0144] And an associated frequency: [Math 6] f = ~^f e

[0145] Also with

[0146] [Math 7] h r = —6

[0147] Such excitation occurs both in the radial and circumferential directions, on the stator 12 and on the rotor 11.

[0148] Separate analytical formulas are used for other types of machines 1, including synchronous machines, asynchronous machines and variable reluctance machines. Such analytical formulas can also be established under load from the number of phases q s of machine 1. Analytical formulas can also be modified to take into account fault cases, for example eccentricity adding new loading cases.

[0149] The higher the wavenumber of the excitations, the lower the vibrations. These analytical formulas therefore also make it possible to restrict the study domain both in terms of maximum wavenumbers and frequencies, which reduces the computation time. Knowledge of the frequencies a priori also makes it possible to optimize the time sampling of the electromagnetic simulation.

[0150] Thus, according to one example, the information representative of the set of magnetic loads comprises information representative of a type of machine as well as a plurality of information representative of design parameters of the machine 1, in particular the parameters Z s , p and q s .

[0151] In a second step 32, the computer 2 obtains a second data item representative of a set of natural modes of a mechanical structure of the machine 1.

[0152] Like the embodiment variants described above, the second data is, according to one example, directly received from the beacon unit 22 or the memory 20 of the computer 2. The second data is in this case, for example, determined by mechanical finite elements or measured by experimental modal analysis, by the use of an excitation hammer on a physical machine 1.

[0153] According to another example, the computer 2 receives information representative of the mechanical structure, for example the model of the machine 1 or parameters representative of its structure, for example of the rotor 11 and / or of the stator 12, from which the processor 21 determines the set of natural modes. The processor 21 determines for example the natural modes from parameters representative of the stator 12, by modeling it by an equivalent cylinder or more precisely by modeling the teeth and the yoke of the stator 12 in beam elements. In each of these exemplary embodiments, the set of natural modes of the mechanical structure corresponds to a series of modes characterized respectively by a modal deformation, a natural frequency and a modal damping.

[0154] In a third step 33, the computer 2, for example the processor 21, determines a subset of significant loading cases and eigenmodes. In other words, the processor 21 determines which loading cases and which eigenmodes are most likely to contribute to the vibrations. The vibrations resulting from a resonance between a loading case and an eigenmode, it is understood here that the subset of loading cases and eigenmodes corresponds to the combinations, two by two, of loading cases whose shape is close to an eigenmode, or vice versa.

[0155] According to a variant, the processor 21 determines a set of projections between the loading cases and the eigenmodes. Each loading case and each eigenmode is for example represented in the form of a vector, the processor 21 calculating, for each combination of loading cases and eigenmode, a scalar product between the two vectors corresponding to a projection.

[0156] The determination of the subset of significant loading cases and eigenmodes results for example from a comparison, for each combination, of the associated projection with a threshold value, for example a threshold value recorded in the memory 20 of the computer 2 or a threshold value corresponding to an input data item received by the beacon unit 22. The threshold value is for example determined so as to establish a level of precision of the calculations, a higher threshold value making it possible to limit the number of significant loading cases and eigenmodes, and therefore to limit the calculations carried out. Optionally, the computer 2 also determines, from the subset of significant loading cases and eigenmodes, a resonance speed. The resonance speed corresponds for example to the electrical frequency f edescribed above. Each natural mode being characterized by a natural frequency fo and the machine 1 being advantageously characterized by analytical equations characterizing its frequency f as a function of the electrical frequency f e , it becomes possible to determine a resonance speed, that is to say an electrical frequency f e associated with the resonance of a natural mode with a loading case.

[0157] In accordance with the example described above, the processor 21 calculates for example a projection of the excitations whose wave number r = 0, corresponding to the most significant excitations, in order to identify the mode whose shape is closest to this force. For example, the projection between the modes and a unit force r = 0 in the radial direction makes it possible to identify a particular natural mode, called the “breathing mode” of the stator. In accordance with the analytical equations given above, we then obtain: [Math 8]

[0158] / o = 12 / e

[0159] And we then determine the resonance speed, corresponding to the electrical frequency f e associated with the combination between the loading case and the natural mode, from the natural frequency fo of the breathing mode.

[0160] In a fourth step 34, the computer 2 obtains a third data representative of a set of relevant nodes associated with the mechanical structure. From this set of relevant nodes, the computer 2 calculates in a fifth step 35 a set of frequency response functions by modal expansion. The modal expansion, known to those skilled in the art, is in particular restricted to the relevant nodes and to the subset of loading cases and significant eigenmodes, so as to reduce the main source of calculation time and memory space.

[0161] As an example, the generic modal expansion formula is given by: [Math 9]

[0162] With x the complex harmonic displacement restricted to the set of nodes of interest I, co m the natural frequency of the natural mode m in rad / s, the modal damping of the mode m, O m the modal shape of mode m among the subset of modes J, F the magnetic excitation strength in N, and co the excitation frequency in rad / s.

[0163] In other words, the computer determines a set of nodes of machine 1 to which the modal expansion calculations will be restricted. The modal expansion is also restricted to the subset determined above, so as to specifically study the responses likely to generate resonances.

[0164] According to an advantageous variant, the set of relevant nodes comprises a first subset of nodes for which the magnetic forces are applied to the rotor 11 and the stator 12, a second subset of nodes generating acoustic noise radiation and a third subset of isolated interface nodes. In other words, the subsets correspond to different criteria for identifying the relevant nodes, in order to ensure accurate calculations while restricting the total number of nodes. According to another example, the relevant nodes correspond to the nodes arranged, in the structure of the machine 1, at the level of the tooth heads and at the fixing points of the machine 1.

[0165] Here we understand that each frequency response function corresponds to the behavior of a node, as a function of the frequency of the electric motor, resulting from the interaction of the loading cases with the natural modes. The response can correspond to an acoustic pressure response, in the context of acoustic frequency response functions, or to a vibration response, i.e. a deformation of a node, in the context of vibration frequency response functions.

[0166] For example, in a finite element mechanical model, in which the external envelope of surface S of machine 1 is discretized into a mesh of N eiem elements of index e included in the interval [1, N eiem ], of elementary surface dS e , of normal vector n e and centered on point C e , the normal deformation U n of an element by modal expansion is given by the following formula:

[0167] [Math 10]

[0168] Where Nmode is the total number of eigenmodes considered, and y m (f) is the modal projection factor of mode m defined as:

[0169] [Math 10]

[0170] Knot

[0171] With Fk(f) the loading case associated with the projection and H m the amplification factor such as:

[0172] [Math 11]

[0173] The Applicant submits in particular that the direct calculation of frequency response functions by modal expansion, according to the generic modal expansion formula given above, is advantageous for reducing the calculation time when the number of loads to be processed is high.

[0174] According to a particular embodiment variant, the frequency response functions are determined separately for each loading case and / or for each eigenmode. A person skilled in the art understands here that the response of a node to a set of loading cases and eigenmodes corresponds to a linear combination of individual responses to each pair of loading cases and eigenmodes. It is therefore possible to calculate the frequency response functions separately for each loading case with respect to all the eigenmodes or even individually for each combination of loading cases and eigenmodes. In particular, the frequency response functions can be determined only with respect to the unique combinations of loading cases and eigenmodes of the subset determined above, their prior selection corresponding to the vibration-generating combinations.

[0175] So, for example, the deformed U n of a node can be calculated separately for each separate excitation, in particular using the following formula:

[0176] [Math 12]

[0177] Where WFRFi corresponds to the frequency response function associated with load case i in the interval [1, Nie] with Nie the number of load cases, and Fi the complex amplitude of load case i.

[0178] Similarly, each frequency response function can be separated into its eigenmodes using the following formula: [Math 13]

[0179] With \| / i,m the projection of the loading case i with the mode m.

[0180] In particular, Frequency Response Functions, also called FRF, allow the determination of a proportional response to a given amplitude loading, for example a unit loading.

[0181] In a sixth step 36, the computer 2 obtains a fourth data item representative of a first set of operating points of the machine 1. Each operating point corresponds to a torque and a speed of the machine 1, that is to say to a speed under which the engine is likely to operate.

[0182] Like the variants described above, the fourth data item is for example directly received from the beacon unit 22 or from the memory 20, or determined by the processor 21. The computer 2 receives for example a second set of operating points, from which the processor 21 determines the first set of operating points. It is understood here that the determination of the first set of operating points corresponds to the establishment of a given number of operating points, sufficient to establish the behavior of the machine 1. The number and nature of the operating points naturally depend on the operating criteria known to those skilled in the art. For example, it is possible to construct a first set comprising 200 operating points.

[0183] According to an advantageous variant, the first set of operating points is associated with the resonance speeds determined above, so as to ensure that the calculations are carried out at the speeds for which the determination of the subset of loading cases and significant eigenmodes indicates a resonance. It is understood here that, in this case, the obtaining of the fourth data is carried out following the determination of the subset of loading cases and significant eigenmodes. In other cases, the obtaining of the fourth data can be carried out at another time, for example in parallel or upstream of the operations described above.

[0184] In accordance with the example above, the first set of operating points includes, for example, one or more points for which the speed corresponds to the electrical frequency f eresulting from the breathing mode of the stator 12, associated with one or more torque levels. In a seventh step 37, the computer 2 obtains a fifth data representative of a set of magnetic states of the machine 1. The computer obtains in particular the distribution and the amplitude of the magnetic forces in the machine 1.

[0185] Once again, obtaining the fifth data item varies depending on the design and the type of input data. According to several examples, the computer determines the electromagnetic state of the machine according to the magnetic finite element method, the permeance / magnetomotive force method, or the magnetic reluctance network method, coupled or not to an equivalent electrical circuit. It is understood here that one or other of these methods can be selected by the person skilled in the art according to different criteria, in particular according to different compromises between calculation time and accuracy. According to yet another variant, the computer 2 receives the fifth data item directly, in particular in parallel with the first set of operating points.

[0186] In one example, each magnetic state includes a magnetic force torsor per stator tooth, each torsor including a radial force, a circumferential force, and a moment.

[0187] Furthermore, each magnetic state in the set of magnetic states is associated with an operation point in the first set of operation points. Obviously, obtaining the set of magnetic states also depends on obtaining the first set of operation points.

[0188] In particular, when the processor 21 determines a set of magnetic states associated with a large number of operating points, the calculations can be reduced by interpolation or extrapolation of the forces, that is to say along specific operating ranges, for example for a fixed torque or speed, or for the same torque / speed ratio. Depending on the operating range considered, the magnetic loads can be of constant amplitude, in which case the processor 21 determines a magnetic state associated with an operating point and extrapolates it over the range. For example, such extrapolation can be applied to a constant flux asynchronous machine 1, a machine 1 with open circuit magnets or a constant current angle.

[0189] According to other operating ranges, the processor 21 can interpolate the forces between two operating points, by selecting the operating points so as to minimize the error made. For example, the variations of the current vector are limited between two successive operating points.

[0190] In an eighth step 38, the computer 2 then determines a set of operational loads from the set of magnetic states.

[0191] In particular, like the loading cases, the operational loadings correspond to a decomposition of the magnetic forces, so as to determine, for a given operating point, an amplitude, for example in N, of each loading case.

[0192] The computer 2 therefore deduces the set of operational loads from the fifth data, for example by the Maxwell tensor method. According to another variant, the fifth data includes a distribution of the magnetic field on a magnetic mesh of the machine 1 and the computer 2 applies the virtual work method and integrates the torsor of the forces per tooth to deduce the set of operational loads.

[0193] Thus, the operational loads make it possible to determine the amplitude of the loading cases determined above, for example the complex amplitude Fi(f) stated above. Finally, in a ninth step 39, the computer determines information representative of a level of noise and vibrations of electromagnetic origin of the machine 1 from the set of operational loads and the set of frequency response functions.

[0194] It is understood here that this determination corresponds to a matching of the frequency response functions, that is to say of the vibratory or pressure reaction in response to a given load, with the real intensity of each load according to the operating point of the machine 1.

[0195] It is further understood that the information may be determined with more or less detail depending on the steps of the method. In particular, the information is for example determined separately for each loading case and / or for each natural mode, the total noise level corresponding to a linear combination of all the information determined.

[0196] For example, the information representing the level of noise and vibrations of electromagnetic origin corresponds to a mean quadratic speed Vrms 2 determined via the so-called electromagnetic vibration synthesis formula: [Math 14]

[0197] In which Cij corresponds to a cross-projection coefficient between the loading cases of indices i and j, and is given by the formula:

[0198] [Math 15]

[0199] In which (p m ,i corresponds to the projection of the modal forms associated with the modes m and 1, such that: [Math 16]

[0200] In particular, it appears that the cross-projection coefficients Cij, just like the projection of the modal forms (p m,i, are independent of the operational loading. According to an advantageous embodiment, the computer 2 thus determines a set of cross-projection coefficients between the loading cases, and calculates the information representative of the noise and vibration level, for example the mean quadratic speed, as a function of this set of cross-projection coefficients. In other words, the set of cross-projection coefficients is recorded in a memory 20 of the computer, so as to simplify the calculations when matching the frequency response functions and the operational level of each loading.

[0201] Furthermore, according to the following identity: [Math 17]

[0202] C ij = C j*,i

[0203] It is also possible to determine only half of the cross-projection coefficients. In another example, the level of noise and vibrations of electromagnetic origin is determined in the acoustic domain, like the frequency response functions. For example, the computer 2 creates a mesh of the machine 1 according to the ISO3744 standard, the acoustic pressure p being given, for any point M of the ISO3744 mesh, by the formula: [Math 18]

[0204] With WFRF ap the frequency response function in the acoustic domain and OLC the operational loading.

[0205] In the same example, the acoustic power W of machine 1 is given by the formula:

[0206] [Math 19]

[0207] With Wo equal to 10' 12 W, Po equal to 20pPa, S1S03744 the total surface area of ​​the mesh according to the standard

[0208] ISO 3744 and N1S03744 the total number of nodes according to ISO 3744.

[0209] It is further understood that the information representative of the noise level and vibrations of electromagnetic origin sought and therefore the calculation methods used may vary depending on the objective of the person skilled in the art. Thus, according to a particular embodiment variant, the computer 2 also receives information representative of the selection of an objective belonging to a set of objectives, for example from the beacon unit 22 in communication with the human-machine interface 220.

[0210] The set of objectives includes for example:

[0211] - a mean square vibration of a surface of machine 1;

[0212] - a mean square vibration of at least one node of machine 1; and

[0213] - an acoustic power radiated by a part or the whole of the machine 1. The information representative of the level of noise and vibrations of electromagnetic origin is then determined according to the selection made. Obviously, it is understood that other elements may depend on this selection, for example the calculation of frequency response functions in the acoustic domain or in the vibration domain. According to yet another variant, the computer 2 obtains a sixth data representative of a set of radiation factors, each radiation factor being associated with a natural mode of the set of natural modes. The computer 2 receives for example directly the set of natural modes and the set of associated radiation factors, the radiation factors having been determined outside the execution of the method, for example by acoustic finite elements from the modal deformation of each mode.In another example, the set of radiation factors is determined, for example for each eigenmode of the subset of loading cases and significant eigenmodes, from information representative of the mechanical structure of the machine 1. The radiation factors are then determined analytically, for example by modeling the stator 12 by an equivalent cylinder.

[0214] For example, the radiation factor c m of a proper mode m of a cylinder of finite length is given by the formula: [Math 20]

[0215] With k the wave number, Rc the outer radius of the cylinder, L st the length of the cylinder, k z the longitudinal wave number and k r the radial wave number.

[0216] In this variant, the information representative of the level of noise and vibrations of electromagnetic origin is further determined as a function of the set of radiation factors associated with the natural modes. The Applicant submits that the use of radiation factors makes it possible in particular to ensure more precise results in low-frequency calculations.

[0217] In the case where radiation factors are imposed, the formula for calculating vibrational frequency responses can be artificially altered as follows: [Math 21]

[0218] So that the electromagnetic vibration synthesis formula can be retained, the acoustic power level then taking into account the effect of the modal radiation factors. Thus, the ninth step 39 makes it possible to obtain a set of noise levels as a function of the operating points of the machine 1, allowing at least the identification of the combinations of torque and speed generating noise.

[0219] Optionally, the computer 2 then displays the information representative of the noise and vibration level via a human-machine interface in communication with the computer 2. The computer 2 communicates for example with the human-machine interface 220 via the beacon unit 22 or another dedicated unit so as to allow the display of graphic content representative of the determined noise and vibration level.

[0220] The graphic content corresponds, for example, to one or more of the graphics illustrated in Figures 4 to 6.

[0221] Thus, the first graph 4 of figure 4 corresponds to a spectrogram illustrating the evolution of the acoustic power 43, in dB, along curves defined by the frequency 41, in Hz, and the rotation speed 42, in revolutions per minute, of the machine 1. It then becomes possible to deduce the noisiest excitations, for example the excitations H24 and H48, corresponding to a ratio between the frequency 41 and the rotation speed 42.

[0222] The second graph 5 of Figure 5 illustrates a separation of the contribution 52, in %, of the different loading cases to the overall noise level of the machine 1, as a function of the rotation speed 51, in revolutions per minute. This second graph 5 makes it possible, for example, to determine, for a given speed, which forces are at the origin of the noise, for example, at low speed, the circumferential forces of wave number r = 0 on the stator, and at high speed, the radial forces of wave number r = 0 on the stator.

[0223] The third graph 6 of figure 6 represents another spectrogram illustrating, for a given speed, the acoustic power level 63 as a function of the order of the natural modes 61 and the loading cases 62. This third graph 6 then makes it possible to separate the contribution of the loading cases and the modes to the noise of electrical origin.

[0224] According to other designs, it is also possible to separate, for example, the contribution of the different radiating surfaces of the machine 1, for example so as to differentiate the radiation from the flanges and the radiation from the yoke of the machine 1.

[0225] This plurality and precision in the information transmitted to the user thus makes it possible to understand what type of force excites what type of mode, in order to reduce the vibrations by acting, as desired, both on the excitation of the machine 1 and on its structure, for example by designing the magnetic circuit differently, the control of the machine, or by moving a natural frequency of the machine 1. It will be understood that this contribution allows parallel work in the electrical domain and in the mechanical domain, and assists the design teams in these two aspects.

[0226] According to a variant, the computer 2 displays other representative information, for example in addition to or replacing the information representative of the noise and vibration level. The computer displays, for example, graphic content corresponding to the graphics illustrated in Figures 7 and 8.

[0227] The fourth graph 7 of figure 7 thus illustrates a set of projections between the loading cases 72 and the eigenmodes 71. Each point of the fourth graph 7 thus illustrates, for a combination of a loading case 72 with an eigenmode 71, the value of the associated scalar product 73, here in kg 0 5 .ms' 2. The points of the fourth graph 7 correspond, for example, only to the combinations of the subset of loading cases and eigenmodes, i.e. to the projections greater than the threshold value used. Such a fourth graph 7 thus allows a simple visualization of the subset of significant loading cases and eigenmodes, as well as, among this subset, the most important combinations. It is for example possible, from this fourth graph, to adapt the threshold value used to better calibrate the level of detail of the calculations. Advantageously, the fourth graph 7 also illustrates, for each eigenmode 71, the associated natural frequency 74.

[0228] The fifth graph 8 of figure 8 illustrates the evolution of a set of frequency response functions 82 determined, for example in m / N, as a function of the frequency 81, for example in Hz. This fifth graph 8 thus makes it possible to visualize the vibration behavior of the machine 1 under the effect of an arbitrarily fixed load, for example unitary, without taking into account the operating points of the machine 1.

[0229] Thus, it will be understood that the present invention provides a method and a device for determining a level of noise and vibrations of electromagnetic origin of an electric motor machine. This method makes it possible in particular to greatly accelerate and simplify the calculations carried out in the field, in particular in comparison with the solutions used in the prior art. This method thus allows the integration of electromagnetic vibration analysis into the design phases of electric motor machines, allowing results to be obtained within a timeframe adapted to the time constraints of the field, without sacrificing accuracy.

[0230] It will be understood that this determination method can be applied to a variety of electric motor machines, and can be integrated into a broader method of designing and / or modeling electric motor machines. It should be noted that this detailed description relates to a particular exemplary embodiment of the present invention, but that in no case does this description have any limiting character with respect to the subject of the invention; on the contrary, its objective is to remove any possible imprecision or misinterpretation of the claims which follow.

[0231] Of course, the present invention is not limited to the exemplary embodiments described above but extends to a method for determining information representative of noise of electromagnetic origin which would include secondary steps without thereby departing from the scope of the present invention. The same would apply to a system and / or a device configured for the implementation of such a method.

[0232] It should also be noted that the reference signs placed in parentheses in the following claims are in no way limiting; these signs have the sole purpose of improving the intelligibility and understanding of the following claims as well as the scope of the protection sought.

Claims

Claims 1. Method for determining a level of noise and vibrations of electromagnetic origin of a machine (1) with an electric motor having a mechanical structure, said machine (1) comprising a rotor (11) and a stator (12), said rotor (11) and said stator (12) being separated by an air gap, said method being implemented by at least one processor, said method comprising the following steps: - obtaining (31) a first data representative of a set of loading cases associated with said machine (1), each loading case corresponding to a component of a magnetic loading according to a decomposition on a mathematical basis, preferably in Fourier series; - obtaining (32) a second data item representative of a set of natural modes of said mechanical structure; - determination (33), from said set of loading cases and said set of eigenmodes, of a subset of significant loading cases and eigenmodes; - obtaining (34) a third data representative of a set of relevant nodes associated with said mechanical structure; - calculation (35) of a set of frequency response functions, by modal expansion restricted to said set of relevant nodes and to said subset of loading cases and significant natural modes; - obtaining (36) a fourth data item representative of a first set of operating points of said machine (1), each operating point being associated with a torque and a speed of said machine (1); - obtaining (37) a fifth data item representative of a set of magnetic states of said machine (1), each magnetic state of said set of magnetic states being associated with an operating point; - determining (38) a set of operational loadings from said set of magnetic states; and - determination (39) of information representative of a level of noise and vibrations of electromagnetic origin of said machine (1) from said set of operational loads and said set of frequency response functions.

2. Method according to claim 1, which further comprises a display, via a human-machine interface, of information belonging to a set of information comprising: - said information representative of said noise and vibration level; - information representative of said subset of loading cases and significant natural modes; and - information representative of said set of frequency response functions.

3. Method according to claim 1 or 2, which further comprises receiving information representative of a set of magnetic loads associated with said machine (1), and in which said obtaining (31) of said first data corresponds to a determination of said set of loading cases associated with said machine (1) from said set of magnetic loads.

4. Method according to one of claims 1 to 3, which further comprises receiving information representative of said mechanical structure, and in which said obtaining (32) of said second data corresponds to a determination of said set of eigenmodes from said structure.

5. Method according to one of claims 1 to 4, which comprises the following steps: - determination of a set of projections between said loading cases and said eigenmodes, each projection of said set of projections being associated with a loading case and an eigenmode; and - comparison of each projection of said set of projections with a threshold value, said subset of loading cases and significant eigenmodes being determined (33) depending on a result of said comparison.

6. Method according to one of claims 1 to 5, which further comprises a determination of a set of resonance speeds from said subset of loading cases and significant eigenmodes, each resonance speed being associated with an eigenmode of said subset, and in which said first set of operating points is associated with said set of resonance speeds.

7. Method according to one of claims 1 to 6, which further comprises a determination of a set of cross-projection coefficients between said loading cases, each cross-projection coefficient being associated with a combination of two loading cases of said set of loading cases, said information representative of said level of electromagnetic noise and vibrations being determined (39) further as a function of said set of cross-projection coefficients.

8. Method according to one of claims 1 to 7, which further comprises obtaining a sixth data item representative of a set of radiation factors, each radiation factor being associated with a natural mode of said set of natural modes, said information representative of said level of noise and vibrations of electromagnetic origin being determined (39) furthermore as a function of said sixth data.

9. The method of claim 8, which further comprises receiving information representative of said mechanical structure, and wherein said obtaining of said sixth data corresponds to a determination of said set of radiation factors from said structure.

10. Method according to one of claims 1 to 9, wherein said set of relevant nodes comprises a first subset of nodes for which magnetic forces are applied to said rotor (11) and said stator (12), a second subset of nodes generating acoustic noise radiation, and a third subset of isolated interface nodes.

11. Method according to one of claims 1 to 10, in which said set of frequency response functions comprises a set of response functions per loading and optionally per eigenmode of said subset of loading cases and significant eigenmodes, said information representative of said level of noise and vibrations of electromagnetic origin of said machine (1) being determined (39) separately for each loading case and optionally for each eigenmode.

12. Method according to one of claims 1 to 11, wherein said set of frequency response functions comprises a set of acoustic frequency response functions.

13. Method according to one of claims 1 to 12, wherein said set of frequency response functions comprises a set of vibrational frequency response functions.

14. Method according to one of claims 1 to 13, which further comprises receiving information representative of a second set of operating points of said machine (1), and wherein said obtaining (36) of said first set of operating points comprises processing of said second set of operating points.

15. Method according to one of claims 1 to 14, wherein said set of magnetic states is obtained (37) from said first set of operating points.

16. Method according to one of claims 1 to 15, which further comprises receiving information representative of a selection of an objective belonging to a set of objectives comprising: - a mean quadratic vibration of a surface of said machine (1); - a mean quadratic vibration of at least one node of said machine (1); and - an acoustic power radiated by a part or the whole of said machine (1), said information representative of said level of noise and vibrations of electromagnetic origin of said machine (1) being determined (39) furthermore as a function of said selection.

17. Computer program comprising instructions for implementing the method according to any one of the preceding claims, when these instructions are executed by a processor.

18. Computer-readable recording medium on which is recorded a computer program comprising instructions for carrying out the steps of the method according to one of claims 1 to 16.

19. Device (2) for determining a level of noise and vibrations of electromagnetic origin of an electric motor machine, said device (2) comprising a memory (21) associated with at least one processor (20) configured for implementing the steps of the method according to any one of claims 1 to 16.

20. Use of the method according to any one of claims 1 to 16 for the design of an electric motor machine.

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