noise & vibrations

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Noise & Vibrationsxxx

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ContentInroductionCoupling LMS – Direct MethodRincipleImplementationCouping NASTRAN – Indirect Method

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Introduction Today, motors are used in many applications close to the user. The

noise pollutes the environment of the user. It is a nuisance that must be mitigated.

Origin of the noise in motors: Driving electronic Torque ripple on gears Electromagnetic forces on stator Coils

To reduce the noise level, a clear identification of the noise and its source is needed.

FLUX is connected to vibrational tool

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How it worksExport magnetic forces computed by FLUX to mechanical CAE tools for vibro-acoustic studies.

Flux applications:2D Transient Magnetics3D Transient MagneticsSKEW Transient Magnetics

mechanical CAE tools:MSC NASTRAN/ACTRANLMS Virtual.Lab

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How it works

Calculation and visualization of magnetic forces

Import :File1.bulk

File.unv

PATRAN

NASTRAN

Virtual.Lab

Export: File2.bulk

Indirect Method

Direct Method

Support for computation

Forces on support

Forces and support

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How it works in FLUXNew function in a new dedicated contextMenu [Computation]/[Open mechanical analysis context]

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Coupling to MSC NastranMagnetic pressures: Maxwell tensor Only for the rotating machines.Computed in the air gap.On a circle (2D) or a cylinder (3D et Skew)

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Coupling to MSC NastranVibro-acoustic analysis must be performed on a full mechanical cycle (360°mech).The time sampling and the mesh must be set to take into account:

space harmonics.time harmonics

Computation in FLUX can be performed using periodicities. The signal is automatically rebuilt to the full mechanical cycle.Magnetic pressures will be calculated in the airgap, tangential and normal comp.

Normal component:

Tangential component:

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0 211

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tn HB

tn HB

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Coupling to MSC Nastran

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Coupling to Virtual.Lab

Geometry

Mesh

Physics Solving Post-processing

Import of Forces from Flux

Structural Model + Modal Basis

Mapping to Structural Model + Vibration

ResponseAcoustic Respons

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Coupling to Virtual.Lab

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Coupling to Virtual.Lab – A Salient Pole Motor

Mechanical Power Mean Value 55 kW

Rotor velocity 7500 rpm

Currents in phases Peak value (sinus wave) 70 A

Field current Constant value 10 A

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Coupling to Virtual.Lab

The UNV file containing the EM Surface Mesh and time domain forces is imported in LMS Virtual.Lab Acoustics

The user can inspect the force distribution per time step and animate the forces in time domain

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Structural model + Modal basis

Contains stator, windings, end caps, housing

One homogenized but orthotropic material is chosen to model the stator (stiffness)

In first instance, a modal basis is used to capture the dynamics of the structure

Coupling to Virtual.Lab

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Forces mapping to structural model + Modal basis

LMS Virtual.Lab maps the EM Forces conservatively from the EM surface to the coarser structural mesh surface

A Fourier transform provides frequency domain forces

These forces are used to compute the vibration response

Coupling to Virtual.Lab

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Acoustic response

LMS Virtual.Lab Acoustics further computes the acoustic radiation:

SPL Sound Power Directivity

Enabling technologies ensuring a fast acoustic simulation result: FEM Acoustics, AML (PML technology)

The results show clearly the harmonic content (7500 RPM stator teeth freq = 6 kHz, rotor pole freq = 500 Hz) of the forces as well as the modal content of the structure (eg first breathing mode around 3 kHz)

Coupling to Virtual.Lab

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Thank you for your interest in our modelling solutions

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