Beam Element Model


Manatee e-NVH software provides fast structural mechanics model for the rapid evaluation of vibration levels under electromagnetic excitations. The model is based on Beam Element Model of the stator yoke/tooth system.  Rotor structure is not modelled, and stator structure is discretized in beam elements. Stator winding is modeled as an added mass. For external rotor PMSM, the equivalent cylindrical shell model is prefered.


During concept design phase of electrical machines, it is important to avoid structural resonances between main lamination modes and main magnetic forces. Electrical engineers can use these fast structural models to quickly evaluate stator vibration and noise levels due to magnetic forces and make a first ranking of different electrical machine topologies. Mechanical engineers can rely on the stator BEM model to estimate the natural frequencies of the stator in free-free boundary conditions. Even if natural frequencies shift when the lamination is integrated in the final housing, an order of magnitude of the main stator modes which can be excited by magnetic forces (such as breathing mode, ovalization mode) is particularly useful for early e-NVH risk assessment.

Compared to equivalent cylindrical shell model the BEM model is more representative of stator tooth bending effect and assesses impact of both radial and circumferential forces (in particular by using the linear contribution plot). It should then be preferred for inner rotor machines.

This fast model is used by electromagnetic design engineers to directly optimize the magnetic circuit with respect to stator RMS vibration level in dB or sound power level in dBA instead of working at magnetic stress or force level.

In detailed design phase, once a detailed CAD model of the e-machine structural environment (e.g. housing, gearbox, etc) is available, calculations can be refined using Manatee 3D modal basis import feature.