Vibro-acoustic Analysis for Noise Reduction of Electric Machines

Vibro-acoustic Analysis for Noise Reduction of Electric Machines From Flux to OptiStruct Example : Synchronous Machine Flux 2D coupling to OptiStruct Patrick LOMBARD Application Team Manager Patrick.Lombard@cedrat.com Christophe BAILLY Senior Application Engineer bailly@altair.com

Introduction Goal of this presentation : illustrate the different steps of a vibro-acoustic study of a rotating machine with the coupling between Flux 2D/3D and OptiStruct Content Main steps in Flux modeling New vibro-acoustic coupling in Flux Steps in OptiStruct 3

Electro-magnetic analysis 4

Main Steps Geometry Mesh Physics Solving Post-processing Transient application Analysis on one mechanical period + Forces computation + Visualization + Forces export Geometry Mechanical mesh Forces import from Flux Vibratory response Acoustic response OptiStruct 5

Synchronous Machine to Model - Presentation Targeted performance Mechanical Power Mean Value 55 kw Rotor velocity 7500 rpm Currents in phases Peak value (sinus wave) 70 A Field current Constant value 10 A 6

Main Steps in Flux Geometry Mesh Physics Solving Postprocessing The geometry is built with Flux overlays 7

Main Steps in Flux Geometry Mesh Physics Solving Postprocessing The geometry is ready to be meshed when we use Flux Overlays 8

Main Steps in Flux Geometry Mesh Physics Solving Postprocessing In this section we make the following steps: Create materials Create circuit Create mechanical sets Define the different regions of the device A Python file may be prepared with the different quantities mentioned above. These quantities will be created automatically. 9

Main Steps in Flux Geometry Mesh Physics Solving Postprocessing Define law of variation of parameters (solving scenario) Solve 10

Main Steps in Flux Geometry Mesh Physics Solving Postprocessing Open the dedicated vibro-acoustic context Create computation support Compute the magnetic forces and their harmonics (on the defined computation support) Display magnetic forces and their harmonics Export the computed magnetic forces to OptiStruct 11

Main Steps in Flux Implementation Geometry Mechanical mesh Forces import from Flux Vibratory response Acoustic response 1- In OptiStruct generate the mechanical support OptiStruct 12

Main Steps in Flux Implementation Geometry Mechanical mesh Forces import from Flux Vibratory response Acoustic response 2- In Flux go to the mechanical analysis context OptiStruct 13

Main Steps in Flux Implementation 3- Import the mechanical support (.bulk) Geometry Mesh Physics Solving Post-processing Transient application Create 2 coordinate systems REP1 and REP2. REP1 depends on XY1 and REP2 depends on REP1 The mechanical support is imported in REP2 Analysis on one mechanical period + Forces computation + Visualization + Forces export 14

Main Steps in Flux Implementation 4- Launch the computations Geometry Mesh Physics Solving Post-processing Transient application Create a computation support inside the airgap The computation support should be on the ¼ of the airgap close to the stator when the computation is for the stator Analysis on one mechanical period + Forces computation + Visualization + Forces export Computation Support Mechanical Support Sliding Cylinder Rotor radius 15

Main Steps in Flux Implementation 4- Launch the computations Geometry Mesh Physics Solving Post-processing Transient application Analysis on one mechanical period + Forces computation + Visualization + Forces export The computation must be launched on one mechanical period 360 In Flux we can choose to run the computation on one mechanical period or one electrical period For example in the case of one mechanical period [60 ;420 ] corresponding to [1.333 E -3 s;9.333 E -3 s] we can consider only ¼ of this period: [7.333 e -3 s ; 9.333 E -3 s] => [330 ; 420 ] We can specify to compute only the magnetic forces or to compute magnetic forces AND harmonics 16

Main Steps in Flux Implementation Geometry Mesh Physics Solving Post-processing Transient application Analysis on one mechanical period + Forces computation + Visualization + Forces export 4- Launch the computations 17

Main Steps in Flux Implementation Geometry Mesh Physics Solving Post-processing Transient application Analysis on one mechanical period + Forces computation + Visualization + Forces export 5- Visualization of the magnetic forces 18

Main Steps in Flux Implementation Geometry Mechanical mesh Forces import from Flux Vibratory response Acoustic response 6- Export the computed magnetic forces to OptiStruct as (*.bulk) file OptiStruct 19

NVH ANALYSIS 20

NVH analysis Step to setup the NVH analysis, we can use this workflow : 1. Mesh the parts 2. Add properties material 3. Import the forces from Flux 4. Add the ERP output 5. Execute the frequency response analysis and post process the radiated surfaces 6. Optional : Use the optimization capabilities to reduce the noise of electric machines 21

NVH analysis Mesh description : Stator : Isotropic material Number of elements = 440 000 DOF = 1.6 millions 22

NVH analysis Mechanical excitation: The excitation are directly exported to the OptiStruct format from the Flux analysis These forces are imported as an include file 23

NVH analysis Modal analysis : Free-free modal analysis between 0 50 000 Hz (1.6 millions of DOF) 1075 modes (include 6 rigid body modes) in this frequency range First elastic mode at 1045 Hz 11 elastic mode at 2788 Hz 24

NVH analysis Modal analysis : Free-free modal analysis between 0 50 000 Hz (1.6 millions of DOF) 1075 modes (include 6 rigid body modes) in this frequency range The job ran on 8 CPUs : Intel Xeon CPU E5-2680 v3 @ 2.50GHz Elapsed time = 54 minutes Normal modes computation = 46 minutes Data recovery (6Go) = 8 minutes 25

NVH analysis Frequency Response analysis : 27360 nodes are excited from the Flux analysis between 0 and 31 875 Hz Constant damping of 0.06% was defined 26

NVH analysis Frequency Response analysis : ERP (Equivalent Radiated Power) output Minimize ERP Reduction of noise and vibrations ERP evaluation ERP Mathematical Expression ERPC : the speed of sound ERPRHO : fluid density ERPRLF : radiation loss 27

NVH analysis Frequency Response analysis : Displacement result 28

NVH analysis Frequency Response analysis : ERP result 29

Conclusions 30

Conclusions The coupling between Flux 2D/3D and OptiStruct works Flux is able to export the excited load in an OptiStruct format The import in HyperMesh is direct The NVH analysis is managed by OptiStruct Shapes variables example Use the optimization capabilities to reduce the noise of the rotating machines : Conceptual or tuning optimization with OptiStruct Electro-magnetic and NVH optimization with a strong coupling with HyperStudy 31

The End 32