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1 Numerical Prediction of Motor Noise in a Continuous Speed Range Titelmasterformat durch Klicken bearbeiten Steffen Peters TAE Symposium Elektromagnetismus 2018 Jürgen Wibbeler Künzelsau, March 8 th 9 th Martin anke 1

2 Electrical Drives as Noise Sources Wikipedia E-mobility Railway traction Wikipedia Marine Propulsion Energy Sector Schottel Industrial Drives ome Appliances Universal Motors, 2

3 Electrical Drives as Noise Sources Origin of Noise by Electrical Drives: Magnetic Circuit Fluidics Drive Side Reluctance, geometry Cooling Gearbox etc. Magnetic saturation Current waveform, Inverters Sources captured by the presented method Gap forces Courtesy of Elektromotorenwerk Grünhain Gmb 3

4 Contents Concept of FEM-based Noise Computation Electromagnetic Analysis Using ANSYS Maxwell Computation of Magnetic Excitation Loads Dynamic Analysis Using Electric Drive Acoustics inside ANSYS Computation of Structural Vibration and Noise Level Summary 4

5 Titelmasterformat Concept of FEM-based durch Noise Computation Klicken bearbeiten 5

6 Concept of FEM-based Noise Computation From Electromagnetic FEM-analysis to Equivalent Radiated Power (ERP): Electromagnetic Analysis DFT Excitation Loads armonic Vibration Analysis Oscillation, ERP, Waterfall Plot Waterfall diagramm Simulation over speed range! 6

7 Concept of FEM-based Noise Computation Waterfall (also Campbell) Diagram: Numerical Analysis vs. Measurement Measurement tools: Accelerometers Microphones Spectrum analyser Anechoic room Fast generation at run-up of the motor Measurement always returns a combined result of all contributing sources. 7

8 Concept of FEM-based Noise Computation Waterfall (also Campbell) Diagram: Numerical Analysis vs. Measurement Example: 40 rotational speed points 30 spectral lines One simulation point per rotational speed and spectral index = 1200 simulation points! FEM-methods with minimized computational effort: reduce electromagetic sim. speed up structural dynamics 8

9 Titelmasterformat Electromagnetic Analysis durch Using Klicken ANSYS Maxwell bearbeiten 9

10 Electromagnetic Analysis Using ANSYS Maxwell Magnetic Field Computation: Force density distribution by Maxwell Stress Tensor: 10 ) ( ) ( ) ( z z y z x z z y y y x y z x y x x x Force density distribution 2 m N ] [ n f n normal vector

11 Electromagnetic Analysis Using ANSYS Maxwell Excitation Loads at Stator (Time Domain): M z 2D F z 3D M rad M z F rad Ftan F rad M tan Ftan Force/moment components are condensed to load centroids at stator teeth (by integrating force density at integration lines). 11

12 Electromagnetic Analysis Using ANSYS Maxwell Evaluation of Obtained Data Quality by Circular Wave Decomposition: Time domain, Force data of all teeth of pole sector 2D-DFT (here using Octave): M 1N 1 mk nl 2i 2i,, e M e N l m n m0 n0 Fˆ k F Ftan Poor quality igh numerical noise! r00.01 r r Ftan Good quality Distinct components r0 r4 r Rot. speed order r0 Wave index r0 12

13 Torque [Nm] Electromagnetic Analysis Using ANSYS Maxwell Calculation for Selected Rotational Speed Points: Reduction of EM-simulations by interpolation n 3 n n 1 n Speed [rpm] n 3 n 4 n 5 Motor characteristics Spectral index i: Interpolation of excitation loads n 2 Re, Im 5 i Excitation spectrum for n 2 i n 1 Excitation spectrum for n 1 13 f

14 Titelmasterformat Dynamic Analysis Using durch Klicken bearbeiten Electric Drive Acoustics inside ANSYS 14

15 Dynamic Analysis Using Electric Drive Acoustics inside ANSYS armonic Analysis ased on Mode Superposition: Eigenmodes and -frequencies as intermediate result ANSYS Project Structure: Fast! Mode 1 Mode 3 Mode z 1456 z 2654 z Modal Analysis armon. Analysis Excitation loads will be imported into the harmonic analysis using functions of Electric Drive Acoustics inside ANSYS. Excitations 15

16 Dynamic Analysis Using Electric Drive Acoustics inside ANSYS Electric Drive Acoustics inside ANSYS: Extension for ANSYS Mechanical FEM-software Supports import of excitation loads harmonic simulation, sweep through speed range ERP computation and display 16

17 Dynamic Analysis Using Electric Drive Acoustics inside ANSYS Support of Load Import and Application: Text-based import interface, flexible formats DFT at import Graphical check Load application at load centroid points (= Remote Points in ANSYS) Excitation loads Load file table Remote Points attached to faces Import preview 17

18 Dynamic Analysis Using Electric Drive Acoustics inside ANSYS Support of Solution and ERP-postprocessing: Definition of sweep parameters ERP-waterfall diagram across speed range ERP-spectrum at selected speed point Extraction of vibration shape at selected OP 18

19 Dynamic Analysis Using Electric Drive Acoustics inside ANSYS Equivalent Radiated Power (ERP): Integrated structural velocity on selected surface A (surface normal component v n ) No true acoustic field calculation P ERP 1 c vˆ 2 2 n da Fast results due to low FE-model size compared to air-borne acoustics direct computation based on mode-superposition harmonic analysis Natural deviation of ERP from true radiated power (P ERP = σ P acoust., σ = 0 1) Use air-borne acoustic field analysis at selected operating points only. 19

20 Dynamic Analysis Using Electric Drive Acoustics inside ANSYS Complementing ERP-results by Optional Acoustic Field Simulations: n Identify critical OPs ERP [d] Get vibration shapes for critical OPs only Analyse true radiation by acoustic field simulation (by dedicated tools for air-borne acoustics) f 20

21 Dynamic Analysis Using Electric Drive Acoustics inside ANSYS Complementing ERP-results by Optional Acoustic Field Simulations: Comparison of ERP and airborne sound power level 3D-field of sound pressure level n [rpm] f [z] ERP [d] Air-borne [d] z 1467 z 21

22 Titelmasterformat Summary durch Klicken bearbeiten 22

23 Summary FEM-based method for ERP-computation and display in a Waterfall plot Employs several methods to speed up the process Implemented for ANSYS Mechanical FEM-software (Electric Drive Acoustics inside ANSYS) Enables fast design analysis and comparison during virtual prototyping Can be refined by air-borne sound analysis 23