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© CADFEM 2018 Hanke, Wibbeler, Vibration and ERP of Electric Machines during Drive Simulation, KMK 2018
Vibration and Equivalent Radiated Power (ERP) of Electric
Machines during Drive Simulation Martin Hanke
Jürgen Wibbeler
KMK 2018, Ilmenau, March 15th – 16th
1
© CADFEM 2018
Electric Motor Design Platform & Workflow
Advanced Magnetics Modeling
2D & 3D Analysis Efficient Motor Design Toolkit
Design
Emag Therm
NVH, Cooling…
Coupled Analysis Control logic, software
System Validation
3D Physical Validation
Concept Design System Validation
Lab
Motor-CAD Maxwell 2D & 3D Mechanical & CFD Simplorer
© CADFEM 2018
Origin of Noise by Electrical Drives:
Electrical Drives as Noise Sources
Hanke, Wibbeler, Vibration and ERP of Electric Machines during Drive Simulation, KMK 2018 3
Sources captured by the presented method
Magnetic Circuit Magnetic Circuit
Gap forcesGap forces
Fluidics Fluidics
Cooling Cooling
Drive Side Drive Side
Gearbox etc. Gearbox etc.
Reluctance, geometryReluctance, geometry
Current waveform,
Inverters
Current waveform,
Inverters
Magnetic saturationMagnetic saturation
Courtesy of Elektromotorenwerk
Grünhain GmbH
© CADFEM 2018
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
• Load Application for Non-skewed and Skewed Motors
• Postprocessing of Equivalent Radiated Power (ERP)
• Summary
4 Hanke, Wibbeler, Vibration and ERP of Electric Machines during Drive Simulation, KMK 2018
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© CADFEM 2018
Concept of FEM-based Noise Computation
5 Hanke, Wibbeler, Vibration and ERP of Electric Machines during Drive Simulation, KMK 2018
© CADFEM 2018
From Electromagnetic FEM-analysis to Equivalent Radiated Power (ERP):
Concept of FEM-based Noise Computation
6 Hanke, Wibbeler, Vibration and ERP of Electric Machines during Drive Simulation, KMK 2018
Electro-
magnetic
Analysis
Harmonic
Vibration
Analysis DFT
Oscillation,
ERP,
Waterfall Plot Excitation
Loads
Waterfall diagramm
Simulation over speed range!
© CADFEM 2018
Concept of FEM-based Noise Computation
Waterfall (also Campbell) Diagram: Numerical Analysis vs. Measurement
Example: 40 rotational speed points
30 spectral lines
= 1200 simulation points!
FEM-methods with minimized
computational effort:
• reduce electromagetic sim.
• speed up structural dynamics
• ERP instead of true acoustics
Hanke, Wibbeler, Vibration and ERP of Electric Machines during Drive Simulation, KMK 2018 7
One simulation point per rotational
speed and spectral index
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© CADFEM 2018
Electromagnetic Analysis Using ANSYS Maxwell
8 Hanke, Wibbeler, Vibration and ERP of Electric Machines during Drive Simulation, KMK 2018
© CADFEM 2018
Electromagnetic Analysis Using ANSYS Maxwell
Magnetic Field Computation:
• Force density distribution by Maxwell Stress Tensor:
9 Hanke, Wibbeler, Vibration and ERP of Electric Machines during Drive Simulation, KMK 2018
)(
)(
)(
21
21
21
HBBHBHBH
BHHBBHBH
BHBHHBBH
zzyzxz
zyyyxy
zxyxxx
Force density distribution
2m
N][ nf
… normal vector n
© CADFEM 2018
Electromagnetic Analysis Using ANSYS Maxwell
Excitation Loads at Stator (Time Domain):
• Force/moment components condensed
to load centroids at stator teeth:
10 Hanke, Wibbeler, Vibration and ERP of Electric Machines during Drive Simulation, KMK 2018
Frad Ftan
Mz
Frad
Ftan
Fz
MradMz
Mtan
2D 2D 3D 3D
© CADFEM 2018
Electromagnetic Analysis Using ANSYS Maxwell
Treatment of Motors with Skewing:
Axial subdivision into planes
(i.e. both in EM and structural FE-models)
Non-skewed Skewed
Hanke, Wibbeler, Vibration and ERP of Electric Machines during Drive Simulation, KMK 2018 11
© CADFEM 2018
Electromagnetic Analysis Using ANSYS Maxwell
Calculation for Selected Rotational Speed Points:
Reduction of EM-simulations by interpolation
Hanke, Wibbeler, Vibration and ERP of Electric Machines during Drive Simulation, KMK 2018 12
Motor characteristics
f
Excitation
spectrum for n2
1 2 3 4
5
Spectral index i:
Re,
Im
i
i
n
Excitation spectrum for n1
n2
n1
n3
Interpolation of
excitation loads
0
0.5
1
1.5
2
2.5
3
0 5000 10000 15000 20000
Torq
ue
[N
m]
Speed [rpm]
n1 n2
n3 n4 n5
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© CADFEM 2018
Dynamic Analysis Using
Electric Drive Acoustics inside ANSYS
13 Hanke, Wibbeler, Vibration and ERP of Electric Machines during Drive Simulation, KMK 2018
© CADFEM 2018
Dynamic Analysis Using Electric Drive Acoustics inside ANSYS
Harmonic Analysis Based on Mode Superposition:
• Total oscillation as linear combination
of eigenmodes
• Primary result: complex modal amplitudes cm ("modal coordinates")
14 Hanke, Wibbeler, Vibration and ERP of Electric Machines during Drive Simulation, KMK 2018
…
M
m
mm uncnu
1
)i,()i,(
Modal Harmonic
ANSYS project structure:
Excitations
u … complex amplitude at arbitrary location
um … displacement of eigenvector m at loc.
n … rotational speed, ω…frequency
M … total included eigenmodes
© CADFEM 2018
Dynamic Analysis Using Electric Drive Acoustics inside ANSYS
Comparison:
Speed-up due to computation in the low-
dimensional space of modal coordinates cm
Hanke, Wibbeler, Vibration and ERP of Electric Machines during Drive Simulation, KMK 2018 15
Example model:
Example model:
≈ 123.000 finite elements
≈ 260.000 nodes
≈ 770.000 unknowns
200 eigenmodes
40 x 30 frequency points
0
5
10
15
20
25
Full Harmonic Mode Superpos.
Elap
sed
tim
e [
h]
Harmonic Response
Modal
© CADFEM 2018
Dynamic Analysis Using Electric Drive Acoustics inside ANSYS
Hanke, Wibbeler, Vibration and ERP of Electric Machines during Drive Simulation, KMK 2018
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
© CADFEM 2018
Dynamic Analysis Using Electric Drive Acoustics inside ANSYS
Data Processing:
Hanke, Wibbeler, Vibration and ERP of Electric Machines during Drive Simulation, KMK 2018 17
Load application points Load application points
attached to faces
Surface
Excitation spectra in
frequency domain
Excitation loads in time
domain, supplied by user
DFT
Mode-Superposition
Harmonic Analysis
(Sweep of Rot. Speed)
Computation of
ERP-spectrum
Modal coordinates
(.mcf-file)
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© CADFEM 2018
Postprocessing of Equivalent Radiated Power (ERP)
18 Hanke, Wibbeler, Vibration and ERP of Electric Machines during Drive Simulation, KMK 2018
© CADFEM 2018
Postprocessing of Equivalent Radiated Power (ERP)
Hanke, Wibbeler, Vibration and ERP of Electric Machines during Drive Simulation, KMK 2018
Equivalent Radiated Power (ERP):
• Integrated structural velocity on selected
surface A (surface normal component vn)
• No true acoustic field calculation
Fast!
• Direct computation from mode shapes
and modal coordinate results
Additional speed-up
• Natural deviation from true radiated power
Use air-borne acoustic field analysis at selected operating points only.
19
AvcP dˆ2
1 2nERP
© CADFEM 2018
Postprocessing of Equivalent Radiated Power (ERP)
Complementing by Optional Acoustic Field Simulations:
20 Hanke, Wibbeler, Vibration and ERP of Electric Machines during Drive Simulation, KMK 2018
f
n
ERP [dB]
Identify critical OPs Get vibration shapes
for critical OPs only
Analyse true radi-
ation by acoustic
field simulation
(by dedicated tools for
air-borne acoustics)
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© CADFEM 2018
Summary
21 Hanke, Wibbeler, Vibration and ERP of Electric Machines during Drive Simulation, KMK 2018
© CADFEM 2018
Summary
• FEM-based method for ERP-computation and display in a Waterfall plot
• Employs several methods to speed up the process
• Continuous workflow with prepared easy-to-use functions
• Implemented for ANSYS Mechanical FEM-software
(Electric Drive Acoustics inside ANSYS)
• Enables fast design analysis and comparison during virtual prototyping
22 Hanke, Wibbeler, Vibration and ERP of Electric Machines during Drive Simulation, KMK 2018
© CADFEM 2018
Future
Why do we need significant speed-up?
Hanke, Wibbeler, Vibration and ERP of Electric Machines during Drive Simulation, KMK 2018 23
Synchronous motor:
short, well defined periodic
interval
few spectral components
within excitations
(< 100)
Induction motor:
long, slip-dependent
periodic interval
dense spectrum containing
several 100 lines
!