Prism Gap

Starting with version 18R1 of Opera, the re-meshing algorithm for Motional Electromagnetic models has been enhanced to include prismatic elements in the gap region of rotating electrical machines. This allows machine designers to extend the use of mosaic mesh to all regions of a model. Using prismatic elements in the gap region significantly reduces solving time by virtually eliminating any overheads due to re-meshing in the solving process.

Field accuracy can be improved by using regular meshed elements in the gap and adjacent regions, where field gradients are usually highest. More regions of the machine model can now be meshed using solely hexahedral and prismatic elements (as seen in Figure 2).

Using mosaic elements, only the face connecting the moving and stationary regions needs to be re-meshed, instead of the entire cell volume. This surface mesh is then copied into the third dimension to create the gap mesh for the new position.

The new algorithm eliminates any mesh quality issues, thus making it completely reliable for any rotor position and step size.

Figure 1. Tetrahedral gap mesh

Figure 1. Tetrahedral gap mesh

Figure 2. New prismatic gap mesh

Figure 2. New prismatic gap mesh

For a test case, by removing the overhead due to re-meshing in a Motional EM model, the solving time is reduced by more than 50%, as shown in Figure 3.

Figure 3.Total solve time comparison –time difference due to gap re-meshing

Figure 3.Total solve time comparison –time difference due to gap re-meshing