Design of lowelectromagneticNoise, Vibration, Harshness ...?Design of lowelectromagneticNoise, Vibration, Harshness (NVH) electricalmachines usingFEMAG and MANATEE ... traction induction

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  • FEMAG Anwendertreffen 2017, 2/3 November 2017


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




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    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

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    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




    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


    E-NVH Computation Process using MANATEE software


  • 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)


    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


    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



    Max torque :~320 N.m


    300 N.m

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    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


    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




    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


    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


    r=2 r=3




    Unit harmonic loads for wavenumbers

    r=0, 2, 4


    r=0 r=2


    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)


    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)


    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:


    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:


    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



    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


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