acoustic noise and vibrations of electric …€¦ · some specificities of electric vehicles nvh...

© EOMYS ENGINEERING 2013- www.eomys.com

ACOUSTIC NOISE AND VIBRATIONS OF ELECTRIC POWERTRAINS

Focus on electromagnetically-excited NVH for automotive applications and EV/HEV

1

LE BESNERAIS Jean

[email protected]

Note: this presentation is based on extracts of EOMYS technical traininghttps://eomys.com/services/article/formations?lang=en

Part 3 Review of electrical systems in electric powertrains and specificities of electromagnetically-excited NVH

© EOMYS ENGINEERING 2013- www.eomys.com 2

REVIEW OF ELECTRICAL SYSTEMS IN EV / HEV SPECIFITIES OF NVH OF EV / HEV


Review of electrical actuators in ICE vehicles

• A conventional ICE cars can already contain up to 100 electric motors

[R2]

•Electrically assisted steering, clutch control•Electric turbochargers•Electric motors to open and close hoods and trunks•

•Electric motor to open gas cap cover• -by- -by-


Main architectures of HEV [B47]

Series/Parallel HEV (ex: Toyota Prius)

Parallel HEV (ex: Honda Accord) Series HEV (ex: Chevy Volt)


Review of passive components in electric traction chains

• Energy storage • Transformers• Inductors (input filter inductors, power-factor-correction chokes)• Capacitors (DC link filter, DC-DC converters)• Cables


Review of power electronics in HEV/EV

• Switching frequency of most converters goes up to 20 kHz, but switching is lowered under light-load and no-load to reduce switching losses and switching frequency

• Buck-boost converter include a capacitor and an inductor

Name Function Operation mode Components

3-phase DC-AC inverter / rectifier

ESS HV to AC voltage to power electric motors in traction, the opposite in braking

Traction / Braking DC link capacitor

AC-DC rectifier Mains AC 50/60 Hz to ESS Charging Filter capacitors

DC-DC converter ESS HV to onboard LV conversion (ex from 400 V to 12V) = buck/boost converter

Traction / Braking / Parking

Capacitors / inductorsHF transformer

DC-DC converter Mains DC to ESS Charging Filter capacitors


Example of Honda Accord power converter unit [B42]


Electromagnetic NVH sources in cars

Charging Parking Traction Braking

Static components Inductors & capacitorsRectifier

Inverter Inductors & capacitorsRectifier

Rotating components Comfort actuators Starter motorSteering motorParking brake motorComfort actuators

Electric motorCooling motorsAlternator (ICE)Comfort actuators

Electric motor / generatorCooling motorsAlternator (ICE)Comfort actuators


Rotor unbalance in HEV

• Mechanical imbalance of the rotor creates dynamic eccentricity, enriching magnetic force spectrumboth in frequency (sidebands) and space domaines (modulation of wavenumbers with +/-1)

• Dynamic eccentricity transforms pulsing forces in unbalanced magnetic forces, generating shaftbending vibrations and structure borne noise

• Couple imbalance occurs when 2 equal masses are placed symmetrically (static balance but dynamicunbalance)

• Couple imbalance is found frequently in EV/HEV when rotor is connected to imbalanced powertraincomponents [R1]

[R1][R1]


Start-up & shut-down noise of ICE in HEV

• ICE start-up & shup down vibration is a significant contributor to overall vehicle vibration

• Special noise reduction techniques can be applied at neutral or park mode on conventional ICE

• However in HEV, ICE start-up does not always occur at neutral or park mode, it depends of many factors (e.g. state of charge of battery, driver torque demand)

• Dedicated noise reduction techniques are implemented on ignition timing, valve opening/closingtiming, piston stop position etc. [R1]

• In HEV special noise & vibration control techniques are based on compensating ICE torque pulsation during starts using fast response characteristics of the electric motor to mechanical torque ripples[R1]


Some specificities of electric vehicles NVH

• Rubber isolation in more effective on high frequency vibration of electric motors compared to ICE, acoustic absorption materials are also more effective

• New balance between electric motor noise, tire/road noise and wind aerodynamic noise

• Modified moments of inertia & eigen-frequencies in the powertrain, lower torque ripple on the shaft line compared to ICE

• Importance of mass/stiffness of batteries in EV lighter body structure

• High directivity, highly integrated components (ex: L, C, generator + motor), high sensitivity to temperature

• Low reproductibility: +/- 10 dB in electric motor or passive components manufactured according to same specification


Psychoacoustics of electromagnetically-excited noise

• Psychoacoustics of electrical machines is still an active research field

• Below 50 km/h, HEV/EV are considered too quiet from pedestrian/cyclists/visually-impaired point of view (addition of warning sound in some cases)

• In HEV/EV there is no longer masking noise of diesel engine, road noise & powertrain noise are more noticeable

• No hearing experience of drivers to electrical noise

• Specific features: harmonic excitation / high pitch / high tonality / PWM

[R5]

[R9]

ICE EV

Interior noise at full load, 2nd gear


Psychoacoustics of electromagnetically-excited noise

• Objective psychoacoustic metrics often used in EV/HEV: loudness (sound intensity), roughness and fluctuation strength (frequency modulation), tonality, Tone-to-Noise and Prominence Ratios (tonal metrics), sharpness (sound timbre and energy at high frequency), Articulation Index (tone detectability) [R8]

• Subjective psychoacoustic evaluation: hearing tests and subjects surveyfor annoyance judgement, pleasantness judgement, detectability and sound design

[R8]

[R10]

Residential background Shopping background Busy background

[R11]

[R13]

acoustic noise and vibrations of electric …€¦ · some specificities of electric vehicles nvh...

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