Simulation of electrical machines end effects with reduced length 3D FEM models

This paper presents a fast simplified FEM calculation of electrical machines, which includes end effects. The considered machine size and power is similar to a 2.5 MW permanent magnet direct drive wind generator, and was simulated as a linear machine. The calculation uses a 3D model with a reduced length of the iron stack, and the full result is generated from the reduced length model and a 2D model of the cross-section of the inside region of the machine. The length of the reduced length 3D model, that is necessary for obtaining relevant calculation results, is analyzed here for different air gap sizes. A simple rule of the thumb for the necessary minimum axial length of the reduced length model can be derived from the presented numerical calculation results.