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FEMAG Anwendertreffen 2017, 2/3 November 2017

1

Design of low electromagnetic Noise, Vibration, Harshness(NVH) electrical machines using FEMAG and MANATEE software

Pierre BONNEELEmile DEVILLERS

Jean LE BESNERAIS

EOMYS ENGINEERINGwww.eomys.com

2

EOMYS ENGINEERING, specialist of e-NVH issues

Engineering consultancy company specialized in acoustic noise and vibrations of electrical machines

Lille (1 hour from Paris), North of France, 5 R&D Engineers

Modeling, simulation & experimental measurements

Experience on more than 50 electrical machines electromagnetically-excited Noise, Vibration, Harshness from 100 W to 30 MW

Developer and distributor of MANATEE software, the first simulation software dedicated to fast electromagnetic & vibroacoustic design optimization of electric machines

www.manatee-software.com

3

Noise and vibrations of electrical machines

Aerodynamic (e.g. fans)

Mechanical (e.g. bearings)

Electromagnetic (e.g. Maxwell forces on stator) = e-NVH

Electrical machine Outer frame

Link with the frame

Gearbox

Vibrations

Noise

Magnetic rotating force wave

Machine structure deflection

Magnetic rotating fields

Electromagnetically-excited noise

MANATEE workflow :

MANATEE can be used:

in basic electromagnetic design phase using fast analytical / semi-analytical models (variable speed noise calculated in a few seconds)

in detailed design phase using optimized coupling with third party electromagnetic or structural FEA (e.g. Optistruct, Ansys) based on Spectrogram Synthesis and Electromagnetic Vibration Synthesis techniques

MANATEE currently available in Matlab (no toolbox) but migration to Python will be completed in Feb 2017

4

E-NVH Computation Process using MANATEE software

MANATEE GUI (PyQT)

Coupling between FEMAG and MANATEE using airgap flux import:

FEMAG: non-linear electromagnetic simulation accounting for control strategy at variable speed

MANATEE: fast NVH calculation and dedicated post-processings (e.g. harmonic analysis, spectrograms, operational deflection shapes, noise maps)

5

Coupling FEMAG and MANATEE

FEMAG flux import

MANATEE e-NVH computation at variable speed

IPMSM with : 48 stator slots (distributed single layer winding),

8 poles (V-shaped buried magnets)

Operating cycle: maximum of the torque versus speed curve (100 RPM/7000 RPM)1

Control strategy: Maximum Torque Per Ampere (MTPA)2

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Study case: Interior PM Synchronous Machine (Toyota Prius 2004)

2Z. Yang, M. Krishnamurthy and I. P. Brown, "Electromagnetic and vibrational characteristic of IPM over full

torque-speed range," IEMDC 20013.1Mitch Olszewski, "Evaluation of 2004 Toyota Prius Hybrid Electric Drive System, 2006

Femag

model

Max torque :~320 N.m

7000

300 N.m

7

FEMAG to MANATEE coupling: development steps

3: Generate the Femag model in Python with femagtools

1 : Define the machine in MANATEE GUI

2 : Find the correspondingModel in Femag

FEMAG to MANATEE coupling: development steps

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4: Run the simulation in Python with femagtools

5: Automated conversion of results for import in MANATEE

6: Run MANATEE structural and acoustic models

FEMAG to MANATEE coupling: simulation workflow

Simulation for 229 spatial nodes in the moving band (~38 nodes/stator pitch), 229 rotor positions and 100 speed iterations

Setting MTPA control strategy for targeted RMS input phase current and output magnetic torque values or taking the Id/Iq curve from the reference.

Computation time : ~25 minutes per speed (~41h 40 minutes for 100 speeds)

Computer used: i7-5820K @ 3.3GHz - RAM 32Go - Windows 8.1 64 bits

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FEMAG simulation model

Moving band

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Airgap waveforms of radial flux density at 3 different operating points (fixed time):

FEMAG simulation results over space

p

3p

5p

7p 9p

12p = Zs - p

15p = Zs + p

N [RPM] Id [A] Iq [A] T [N.m]

1500 -190 149 324

4000 -47 63 100

7000 -22 40 60

No new wavenumbers despite saturation

p

3p 5p 7p9p

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Time waveforms of radial flux density at 3 different operating points (fixed angle):

FEMAG simulation results over time

No new time orders despite saturation

N [RPM] Id [A] Iq [A] T [N.m]

1500 -190 149 324

4000 -47 63 100

7000 -22 40 60

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Tangential and radial harmonic magnetic forces (magnitude,

wavenumber, frequency, phase)

3D airgap flux distribution

HARMONIC FORCE PROJECTION

r=2 r=3

ELECTROMAGNETIC MODEL

r=0

STRUCTURAL MODEL

Unit harmonic loads for wavenumbers

r=0, 2, 4

STRUCTURAL FREQUENCY RESPONSE FUNCTIONS

r=0 r=2

ELECTROMAGNETIC VIBRATION SYNTHESIS

Complex FRFs (radial & tangential) for each

wavenumber rVibration and noise spectrograms

Importing FEMAG results

Manatee 2,5D analytic model

Computation time: 3 sec per speed

MANATEE e-NVH simulation process

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Projection of the airgap Maxwell stress tensor on stator tooth tips:

MANATEE magnetic forces model

Harmonic decomposition of time and spatial pressure distribution (FFT2D):

, , , /

, , ,

2 /

/, /, !"#$%,

&, ' : frequency and wavenumber : magnitude of the harmonic &, ' ( : phase of the harmonic &, '

Maxwell stress tensor is available in .PLT0 of FEMAG

Lumped forces per tooth using Maxwell stress integration over stator tooth not available yet, but one can show that they are equivalent to Maxwell stress airgap projection

r=0 r=1 r=2

Analytical models can be used for the calculation of natural frequencies and deflections of an equivalent 2.5D cylinder

Some rules are used to take into account teeth stiffness and mass as well as winding and frame

The effect of boundary conditions (clamped / free / simply supported) is also included

If necessary MANATEE can also be coupled to structural FEA (e.g. GetDP, Optistruct)

14

MANATEE structural model: modal basis

&), *),2+

Computing the static displacement ,,) due to each magnetic excitation , considering the stator structure as an equivalent ring:

Computing the dynamic displacement accounting for modal basis:

The Frequency Response Function -.- & is obtained by putting unit rotating wave as input (,=1) If the analytical model assumptions are not fulfilled FRF can be automatically calculated by calling a structural

FEA model (e.g. free software GetDP, or commercial software Optistruct)

15

MANATEE structural model: Frequency Response Function

,,/ , .)0.)123,,/ , 12.)0.)1

5325' 1

,, ,,/

1 &&)6 27 &&)

-.- &

Overall radial yoke displacement & velocity levels are given by linear superposition:

, & -.- & ,

MANATEE structural model: Electromagnetic Vibration Synthesis

8 & 92+&, & Unit magnitude FRF allow to understand better the physics (e.g. presence of multiple resonances, relative

effect of tangential & radial forces), to decouple structural characterization from operationalelectromagnetic force calculation and to more computationally efficient

Acoustic noise is deduced from vibrations by calculation of a cylindrical modal radiation factor:

MANATEE acoustic model

Graphical representation of FFT2D spectrum:

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Radial pulsating (wavenumber r=0) force harmonics (red boxes) are likely to produce air-borne acoustic noise

, , !"#$%,

6 12

f=2fs, r=8 f=6fs and 12fs, r=0

Time orders are proportional to 2fs (2pfR) and wavenumbers are proportional to GCD(Zs,2p)=2p=8

FEMAG to MANATEE NVH results of Prius 2004 magnetic forces

A comparison is made between MANATEE results (analytical) and FEA results (Ansys) found in literature2 infree-free boundary conditions

Risk of resonance:

19

2Z. Yang, M. Krishnamurthy and I. P. Brown, "Electromagnetic and vibrational characteristic of IPM over full torque-speed range," IEMDC 20013.

MANATEE 642 1673 2908 4239 5173

r = m = 0

f : &)= 5173 Hz orr = m = 8

f : &)= 7854 Hz

FEMAG to MANATEE NVH results of Prius 2004 structural modes

Significant differences are found for high circumferential indices but the winding modeling strategy is not detailed in the article2 using Ansys

FEMAG to MANATEE NVH results of Prius 2004 magnetic forces

Automated derivation of theoretical spectrum of magnetic forces and potential resonances:

Analytical derivation of magnetic force characteristics and structural modal analysis predict a resonance of mode (0,0) stator lamination at 6463 rpm with magnetic forces at 12fs involving 11p and 13p rotor mmfharmonics:

FEMAG to MANATEE NVH results of Prius 2004

6fs

12fs

There is no unphysical harmonics due to meshing issues

On Prius 2004, sound power level is fully dominated by breathing mode of stator lamination mainly under 6fsexcitation and there is no strong resonance occuring below 6000 rpm

Overal sound power level including modal participation factors, and noise spectrogram:

FEMAG to MANATEE NVH results of Prius 2004

Acoustic noise spectrogr