e-Machine dynamic behavior and its contribution to ...

Live-I Public Event

25/01/2021

25/01/2021 Live-I 1

e-Machine dynamic behavior and its contribution

to Powertrain vibroacoustics

Dr. Jean-Baptiste Dupont and Ing. Martin Jeannerot

Introduction

Breaking news

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Introduction

Is that true ?

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Is that true ? Are e-machines that quiet ?

Let’s hear some noises of electric motors

Introduction

Full powertrain

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It appears that emachine can have a NVH issue (are you deaf ?)

Complex physical phenomena that lead to the dynamic behavior of eMachine

and the associated sound radiation

eMachines are often associated to a gearbox (for example in automotive

powertrain)

Consequences of this association ?

Introduction

Is that true ?

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Content

Introduction

Noise generation process

Simulation methodology and validation

Optimization examples

Full powertrain example

Conclusion

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Content

Introduction





Conclusion

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Power supply

Flux density and

electromagnetic

excitation

Structure dynamic

response

Noise radiation

and vibration

transmission


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Motor

Structure noise

Air borne noise

Gearbox

Torque ripple

Main transfer paths:

- Air borne

- Structure borne

- Torque ripple

Electromagnetic excitations

Three main types of electromagnetic excitation

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BlidFd

Fd B

courant

Fd B

courant

Lorentz Force

Current

Force applied to

the wires

Magnetostriction

B

Additional strain under

magnetic flux density

Maxwell pressure

medium 2 (µ2)

P n

Bt1

Bn1

B1

B2Bt2

Bn2

P n

Bt1

Bn1

B1

B2Bt2

Bn2

Medium 1 (µ1)

Force density created

at an interface

0

2

2

1

μ

BP n

n

Maxwell pressure

medium 2 (µ2)

P n

Bt1

Bn1

B1

B2Bt2

Bn2

P n

Bt1

Bn1

B1

B2Bt2

Bn2

Medium 1 (µ1)

Force density created

at an interface

0

2

2

1

μ

BP n

n

Vibroacoustic behavior

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Magnetic forcesStator dynamic

responseAcoustic radiation

Vibration to noise

conversion ?Stator excitation ?

- Stator modes

- Excitation frequencies

- Excitation space distribution

- Deflection waveform

- Conversion efficiency linked to

deflection

Electromagnetic excitations

Wave forces

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They are characterized with:

- their frequency (f),

- their spatial order (m).

Spatial order 2

300Hz

Spatial order 0

250Hz

Spatial order -4

50Hz

Spatial order 4

400Hz


Stator

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Most important structure modes:

Stator radial modes

Mode (2,0) Mode (3,0) Mode (4,0)Mode (0,0)

Breathing mode

1000 Hz 2500 Hz 4500 Hz 6000 Hz


Resonance

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Frequency and space coincidence between an excitation contribution and

a stator mode.

4-lobe rotating force 4-lobe stator mode


Radiation efficiency

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Structure ability to convert vibration into noise : Radiation efficiency

S

2fVSc

fWf

)(

)( )(

Depends on : - the frequency,

- the surface shape,

- the deflection shape

Radiated power

Structure vibration

velocity

« Good » conversion : = 1


Radiation efficiency

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Mode Radiation factor associated to the deflection

0 lobe

2 lobes

3 lobes

4 lobes

Cylinder: R=0.12m

Content

Introduction





Conclusion

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Simulation methodology

Basic principle

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Electromagnetic Simulation

(2D or 3D Finite Element Method)

Electromagnetic mesh

Mapping tool

Electromagnetic

excitation

Dynamic simulation

(3D Finite Element Method)

Structural

mesh

Dynamic

excitation

Acoustic simulation (FEM or BEM or analytical)

Vibration

velocity

Acoustic power

Basic principle:

Electromagnetic finite element

simulations

Projection of the excitations onto

the structural mesh

Dynamic structural simulation

Estimation of the acoustic radiation


Basic principle

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Mapping tool

2D electromagnetic

simulation

3D dynamic simulation

Dupont et al., Simulation of the airborne and structure-borne noise of electric powertrain:

Validation of the simulation methodology. Tech. rep., SAE Technical Paper, 2013.


Validation

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Test

Simulation

Acceleration – H44 (Automotive WRSM)

Speed [rpm]

Accele

rati

on

[m/s²

]


Validation

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Radiated noise power - H4 (automotive auxiliary device)


Validation

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Radiated noise power – H8 (automotive auxiliary device)


Validation

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Radiated noise power – H2 (aviation industry)

10dB

Content

Introduction




o Structure optimization

o EM design optimization


Conclusion

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Example of structural optimization

Context

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Case 1: Noise of ICE starter

– The noise of starter becomes critical with the of « stop & start » systems

– Low noise but increase of the number of occurrences

– What is loud? What is annoying?

Ref: Wojtowicki et al., Noise diagnosis and reduction of

electrical machines based on the use of multi-physical

modelling, Aachen Acoustic Colloquium 2014.


Diagnosis

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Noise of a starter: vibration measurement in starting phase

0.00 5000.00Hz

REF3:+Y (CH12)

0.00

1.00

s

Tim

e

-57.59

42.41

dB

m/s

2

2566.90

AutoPow er REF3:+Y WF 349 [0-1.74 s]

Engine speed

profile

Resonance


Modal characteristics

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After model updating procedure 2-lobe modes

878Hz 937Hz

3-lobe modes

2278Hz 2400Hz

4-lobe modes

3310Hz


Electromagnetic excitation

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Computed electromagnetic excitation


Analysis of the excitation

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H19: 3-lobe excitation

H38: 2-lobe excitation


Critical speed

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2-lobe excitation contribution

at 1000Hz

Critical speed:

Both a frequency and space coincidence between an excitation contribution

and a stator mode

(2,0) mode – ~1000Hz


Optimization

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Diagnosis: Excitation of the 3-lobe mode by the 3-lobe excitation

contribution related to H19

Optimization: modification of the structure in order to shift the 3-lobe mode

outside of the speed range of interest. No impact on the EM performance.

Frequency shift of

the 3-lobe modeOrder tracking – H19

-12dB

Content

Introduction





o EM design optimization


Conclusion

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Examples of EM design optimization

Case 2: PHEV traction machine

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Case 3: Sound radiated by a PHEV traction machine (10-pole PMSM)

Goal: find a EM design that minimizes the noise level radiated by the

machine for given operating conditions (speed(s), current)

Constraints: keep an acceptable torque (i.e. at least -2% compared to the

torque obtained for the initial design)

Modification example (generic design):



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Focus of the

optimization

process



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-14dB

Focus on a specific tonal noise

Same operating conditions (speed, torque, current)

Sound power level – Overall level

Sound p

ow

er

level[d

B r

ef.

1e-1

2 W

]

5dB

— Initial design

— Optimal design


Case 3: ePowertrain

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ePowertrain (Permanent Magnet Synchronous Machine)

Focus on:

o Several operating conditions (WOT, POT…)

o several tonal contributions

o Airborne noise, structure-borne noise and torque ripple

Same operating conditions (speed, torque, current)

Workflow :

Initial diagnosis

Optimization and design specification

Prototype and test


Case 3: ePowertrain

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WOTEngine order 8 Engine order 48

Engine order 96Engine order 24

Initial design

Optimal design

10dB

10dB

10dB

10dB

Initial design

Optimal design

Initial design

Optimal design

Initial design

Optimal design

Content

Introduction


Example of structure optimization



Conclusion

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Full ePowertrain

Presentation

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• Goal : simulate the noise and the vibration of a full ePowertrain

dedicated to automotive traction due to eMachine and gears effect.

• This simulation is a key step in a diagnosis approach and in an

optimization process.

• Characteristics of the full ePowertrain :

o eMachine : 8-pole PMSM (160kW 0-12000rpm)

o 2-stage gearbox directly flanged on the eMachine (helicoidal gears)

• Computation of dynamic response related to gear excitation and EM

excitation (independant computations)

Full ePowertrain

Torque

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• Transient torque generated by the eMachine (5000rpm)∆𝑇

𝑇= 31%

The torque ripple generated by the eMachine is

not taken into account in the gear simulation

Full ePowertrain

Finite Element Model

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Full ePowertrain

Campbell diagram

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Full ePowertrain

Operating Deflection Shapes

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H7,09 – 674Hz – 5700rpm

Excitation of the overall bending mode of the

ePowertrain (coupled to a shaft motion) by the

gear excitation

Full ePowertrain


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H24 – 1320Hz – 3300rpm

Excitation of the overall bending mode of the

ePowertrain by the torque ripple due to the

eMotor

Full ePowertrain


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H14.19 – 2413Hz – 10204rpm

Excitation of a gear bending and shaft bending

mode by the gear excitation

Full ePowertrain


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H48 – 7440Hz – 9300rpm

Excitation of the breathing mode of the eMotor

stator by the 0-lobe radial electromagnetic

excitation

Full ePowertrain

Sound synthesis

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Content

Introduction


Example of structure optimization



Conclusion

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Conclusions

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Vibroacoustics of e-machines: new field of expertise

Powerful multiphysical simulation methodology

Wide optimization possibilities

o Supply strategy (PWM strategy, PWM frequency)

o Electromagnetic optimization


o Optimization of the integration (rubber mounts, acoustic screens…)

Often associated to a gearbox: expertise complementary to gears

o Possibility to compute uncoupled associated responses

o Coupled behavior: that’s a tough one…

That’s all folks !

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Thank you for your attention

[email protected]

&

[email protected]

mailto:[email protected]

mailto:[email protected]

e-Machine dynamic behavior and its contribution to ...

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