Uneven Airgap


Manatee software allows to assess the effect of uneven bore radius due to mechanical tolerances on the electromagnetic noise and vibrations levels. A particular pattern can be chosen (e.g. elliptical deformation) as well as its magnitude in percentage of the airgap width.

For a quick analysis, Manatee uses a perturbation technique of the airgap flux density to estimate parasitic magnetic forces induced by 3D eccentricities. This method can be applied when using a Magnetic Look Up Table, even when importing the airgap flux from a third party software.

This perturbation technique, also used for eccentricities, is suitable for low airgap deformation values (max 15% of the magnetic airgap width). It can be used to estimate the effect of eccentricity on “high frequency” magnetic force harmonics that are not strongly related to the saturation level of the electrical machine.



This features allows mechanical engineers to calcule the effect of uneven airgap on electromagnetic noise and vibrations. This way, too conservative values of mechanical tolerances can be avoided. Uneven airgap can be induced by the manufacturing process (e.g. segmentation, weldings, shrink fit) of the electrical machine.

It also allows electrical engineers to perform robust e-NVH ranking of different electrical machines. An electrical machine A may be louder than machine B with a perfectly circular stator, while it becomes the opposite when including stator deformation.