Incorporating Lamination Processing and Component Manufacturing in Electrical Machine Design Tools

Measures to improve the modeling of steel-sheet laminations in electrical machine design tools are studied. Only the magnetic properties, namely, the permeability (BH curves) and the iron losses are addressed. The sensitivity of these properties upon dimensional, directional (anisotropy) and excitation variations, as well as upon the electrical machines manufacturing steps is evaluated. The studied electrical machines manufacturing step are: guillotine, laser-cutting, welding, pressing and punching. The properties of the delivered lamination coils and the various associated loss figures are also statistically benchmarked. The focus is on finding guidelines for incorporation of these sensitivities in design tools when needed. For this purpose, 5 Hz to 10 kHz tests are conducted on Epstein strips, on L-shaped segments and on standard stator laminations. Two different steel grades are studied. It is shown that the lateral dimension, anisotropy and welding influences are much more pronounced then those for punching, pressing and laser cutting and hence, need to be addressed in design tools. It is found that the commonly used Epstein test results of the coils are slightly inferior to the mean loss value of the online-testing (losses that are measured at every 1 m of the entire coil length). It is also noted that, the delivered laminations are almost always better than those ordered and the losses for each individual lamination coil are nearly constant.