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EOMYS ENGINEERING
Noise and vibration Dynamic Signal Analysis on electrical machines
15/04/2015
LE BESNERAIS Jean
SOURON Quentin
www.eomys.com
© EOMYS ENGINEERING 2014-2015
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A. EOMYS ENGINEERING
B. Why Dewesoft ?
C. Magnetic acoustic noise and vibrations in electrical machines
D. Measurement set-up
E. Acquisition software set-up
F. Post-processings
G. Conclusion
EOMYS ENGINEERING 2014-2015
(C) ©EOMYS
ENGINEERING 2013-2014
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A. EOMYS ENGINEERING
Overview
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Young Innovative Company* created in may 2013
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Located in Lille, North of France
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Activities : engineering consultancy & applied research
specialized in electrical engineering
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Sectors : transportation (railway, automotive, marine,
aeronautics), energy (wind, hydro), industry
*"Jeune Entreprise Innovante": the French government recognises that EOMYS runs significant R&D activities
© EOMYS ENGINEERING 2014-2015
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Services
Analyze and solve your multi-physics technical issues
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multiphysics experiments (investigation, pre-certification) and simulations
advanced post-processings of experimental and simulation data
sensitivity studies, technical state of the art
proposal of technical solutions and validation by tests or simulation
Improve your design process performance
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development, validation and integration of high performance models
development of user-specific design interfaces
formalization of design rules
delivery of high-level technical trainings
Optimize your products and processes
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coupling with multiobjective constrained optimization methods
automation of the design process
optimization of the “virtual prototyping” chain
Innovate
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technical state of the art, ideation, concept ranking and validation
research consortium / co-development projects
licence granting
© EOMYS ENGINEERING 2014-2015
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MANATEE software
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fast electromagnetic and vibro-acoustic simulation of electrical machines (Matlab-based)
use of analytical, semi analytical and numerical models to reach the best compromise accuracy / speed
automated coupling with FEMM (electromagnetic) and GetDP (mechanics)
modeling of all space and time harmonics
fault simulation (e.g. eccentricity, broken bar, demagnetization)
more than 100 post processing graphs
… see more at www.eomys.com
© EOMYS ENGINEERING 2014-2015
EOMYS
ENGINEERING – 121, rue de Chanzy 59260 Lille-Hellemmes
FRANCE
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Experience
Optimal design of innovative systems
permanent magnet synchronous wind generators, traction induction machines
transformers and inductors
Scientific software development
use of open sources (FEMM, GetDP, OpenFoam, Octave) & commercial software (Flux, Opera, Ansys, Matlab)
advanced optimization methods (multiobjective constrained genetic algorithms, space-mapping)
development and distribution of MANATEE® software
Analytical, semi-analytical and numerical modelling
CFD simulation coupled to thermal nodal networks, hydraulic networks
electromagnetic subdomain models, reluctance network models
structural beam element models
Experimental characterization
noise and vibration measurements
thermal and electrical measurements
© EOMYS ENGINEERING 2014-2015
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Internal R&D programme
Reduction of noise & vibration in electrotechnical systems
active and passive techniques in rotating electrical machines and passive components
3D electro-vibro-acoustic simulation of rotating machines (asymmetries, skewing)
modeling of magnetic forces in rotating machines
magnetostriction and Maxwell force simulation (GetDP)
development of hybrid simulation methods (FEM / semi-analytic)
Experimental vibroacoustic characterization
advanced post processings
new measuring methods of structural modes and operational deflection shapes
© EOMYS ENGINEERING 2014-2015
EOMYS
ENGINEERING – 121, rue de Chanzy 59260 Lille-Hellemmes
FRANCE
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B. WHY DEWESOFT ?
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A “multiphysic” acquisition software suitable for multiphysics consulting activities of EOMYS (electrical
engineering, thermics, vibro-acoustics, etc.)
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A flexible software suitable for both investigation tests and pre-certification tests
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An acquisition system suitable for both low frequency (ex: temperature) and high frequency (ex: noise)
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A light-weight acquisition module suitable for field measurements
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A cost-competitive solution
© EOMYS ENGINEERING 2014-2015
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C. MAGNETIC NOISE AND VIBRATIONS IN ELECTRICAL MACHINES
What do we call “electromagnetic acoustic noise” or electrical noise ?
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Sinusoidally-fed squirrel cage induction machine during run-up (« slotting noise »)
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Non-sinusoidally-fed squirrel cage induction machine at starting (« PWM noise »)
-> « high » frequency (100 to 10000 Hz), high tonality noise
Definition
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Magnetic noise and vibrations is defined as noise and vibrations due to magnetic forces
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Magnetic forces can be defined as « forces arising from the presence of a magnetic field »
-> magnetic noise stops when an induction machine is current-free
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Two magnetic forces exist in electrical machines: magnetostriction & Maxwell forces
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Magnetostriction forces tend to
« shrink » the iron along the field lines
Maxwell forces tend to get the
stator closer to the rotor
STATOR
yoke
ROTOR
slots
teeth
from [B7]
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Electrical noise and vibration phenomena
electrical machine
endplate
mount
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Tangential and radial magnetic force harmonics generate radial
vibrations propagating to the external frame
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Torque harmonics can propagate through rotor shaft as
torsional vibrations, and efficiently radiated (large surface /
normal vibrations) like gearbox frame or mount
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Unbalance forces harmonics generate shaft bending vibrations
which propagate to bearing & frame
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Axial forces make endplates axial vibrations
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Forced excitation + resonances
gearbox
frame
shaft
supports
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Why do electrical noise and vibrations matter ?
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Health (e.g. in industry): lower the exposure to acoustic noise level
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Comfort (e.g. in transportation): increase the sound “pleasantness” based on psychoacoustic metrics
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Security (e.g. in defense): lower the vibroacoustic signature
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Robustness (e.g. in energy): lower the electromechanical fatigue
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Standard requirements
Electromagnetics & vibroacoustics interactions
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Cost optimization -> thinner yoker -> increased vibration & noise
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Skewing technique which is used to reduce noise and vibration levels degrades torque and efficiency
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Electromagnetic & thermal & vibro-acoustic design have therefore strong interactions
© EOMYS ENGINEERING 2014-2015
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Characterization of electrical noise and vibration
• “time” frequency f
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“space” frequency = space order = wavenumber r
r=0
r=6
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harmonic origin: slotting, winding, PWM, saturation, eccentricity…
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wave type: pulsating Vs rotating, rotation direction
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forced excitation Vs resonance
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largest magnetic force occurs at f=2fs (electrical frequency) r=2p (pole pair number)
© EOMYS ENGINEERING 2014-2015
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D. MEASUREMENT SETSET-UP
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Dewetron SIRIUS 8 channel ACC+
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B&K 1-axis radial accelerometer in the middle of the stator stack
(at least 8 recommended to capture r=4 order)
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PCB ½ ’’ free field microphone 1 m away from the outer frame
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Optel Thevon tachometer (1 pulse per rev)
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Chauvin Arnoux current clamps
ACTIVE
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E. ACQUISITION SETSET-UP
Spectrograms
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FFTs for noise (20 kHz), accelerometers (10 kHz) and current (5 kHz)
Tachometer setup
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Analog tacho
Order tracking
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For magnetic vibrations due to “slotting effects” the best orders to be tracked are 2p, Zr-2p, Zr, Zr+2p (p:
number of pole pairs, Zr: number of rotor slots or number of rotor poles)
-> some high rank orders are needed for high torque machines (ex: Zr=212)
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For mechanical vibrations the order 1 should be also tracked
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Specific set-ups are used for the best tradeoff between rpm and Hz accuracy
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© EOMYS ENGINEERING 2014-2015
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Operation Deflection Shape
Use of modal test environment of Dewesoft to visualize the stator deflection under magnetic forces
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Calculation of reverberation time
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Use of Dewesoft + Matlab to obtain the reverberation time in order to estimate the direct field (electrical
machine) and indirect field (room reflections) contribution to the overall sound pressure level
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A-weighting and third octave analysis
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dB and dBA as a function of speed
Other tips
=
− 20
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Normalization of the noise level to the current level
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Online estimation of slip in asynchronous machines using tracking filter
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Current angle calculation based on 2 or 3 phase measurements
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“Spatiograms”: 2D FFT run-ups of circumferential vibration waves
© EOMYS ENGINEERING 2014-2015
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=1−
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F. EXPERIMENTAL RESULTS
Operation deflection shape (case of a 1MW induction machine, r=1 & 2)
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Current spectrograms (IM, raw)
fundamental
© EOMYS ENGINEERING 2014-2015
slotting harmonic with dynamic
rotor motion
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Case of a concentrated winding PM synchronous machine (12 stator slots, 10 poles)
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run-up to 2200 rpm
switching frequency at 1500 Hz
8 accelerometers
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Accelerometer spectrograms (raw)
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slotting excitations
Accelerometer spectrograms (run(run-up)
PWM +slotting excitations
PWM excitations
natural frequencies (vertical lines)
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Zoom on « slotting » excitations matching a mode close to 250 Hz
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Order tracking
© EOMYS ENGINEERING 2014-2015
Wavenumber r=2
modulated by
eccentricity
250 Hz natural frequency (parabola)
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Spatiogram:
Spatiogram: spectrogram of a specific space order r
Complex value + dual side FFT
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r=2, f=2fs
Spatiogram r=2
r=2p=10, f=-fswi -2fs
same as r=-10, f=fswi +2fs
r=2p=+10, f=fswi -2fs
not available yet as a function of rpm…
© EOMYS ENGINEERING 2014-2015
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r=-2 and +2 spatiograms are the same (transposition)
r=2
r=-2
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r=0
r=2
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Sidebands due to eccentricities
Mechanical unbalance (rotation frequency)
r=1
First bending mode
r=2
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r=3
r=2
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r=4
r=2
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Plot / slot interactions appear as single sided-excitation (pure rotating force waves)
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Eccentricities and PWM vibrations appear as double sided excitations (modulation effects: pairs of travelling
vibration waves)
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Natural frequencies appear as symmetrical amplifications in double sided FFTs
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The machine vibration behavior is determined by wavenumbers 1 and 2
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“Spatiograms” based on Dewesoft Math functions are far more efficient than doing an ODS at each
frequency and each speed…
© EOMYS ENGINEERING 2014-2015
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G. CONCLUSIONS
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Advanced rotating machine analysis applied to electrical noise & vibrations reduction
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On field post-processings allow to quickly identify the physical origin of noise & vibration
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Combined with internal simulations (e.g. MANATEE software) some mechanical and electromagnetic
redesign possibilities can be proposed and validated
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Up to 15 dB reduction has been obtained after redesign
© EOMYS ENGINEERING 2014-2015
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Thank you for your attention
Any questions?
questions?
www.eomys.com
© EOMYS ENGINEERING 2014-2015
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