Noise & Vibrations. xxx. www.tianyuantech.com www.magsoft-flux.com www.cedrat.com. Content. Inroduction Coupling LMS – Direct Method Rinciple Implementation Couping NASTRAN – Indirect Method. Introduction .
Coupling LMS – Direct Method
Couping NASTRAN – Indirect Method
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:
To reduce the noise level, a clear identification of the noise and its source is needed.
FLUX is connected to vibrational tool
Export magnetic forces computed by FLUX to mechanical CAE tools for vibro-acoustic studies.
mechanical CAE tools:
Support for computation
Forces on support
Calculation and visualization of magnetic forces
Forces and support
New function in a new dedicated context
Menu [Computation]/[Open mechanical analysis context]
Magnetic pressures: Maxwell tensor
Only for the rotating machines.
Computed in the air gap.
On a circle (2D) or a cylinder (3D et Skew)
Vibro-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:
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.
Import of Forces from Flux
Structural Model + Modal Basis
Mapping to Structural Model + Vibration Response
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
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
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
Forces mapping to structural model + Modal basis
LMS Virtual.Lab Acoustics further computes the acoustic radiation:
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)