Application of a weak coupling algorithm in the electromagnetic-mechanical finite-element analysis for Roebel bars of large synchronous machines

The deformation process of Roebel bars embedded in slots of electrical machines mainly depends on the acting electromagnetic forces inside the current carrying regions and the mechanical preload due to the slot wedge. With this fully coupled electromagnetic-mechanical problem, the behavior is completely different between the two cases of loose and fixed bars. To accurately include both the volume forces inside conducting regions and the surface forces at material boundaries in the coupled analyses, a weak coupled cascade algorithm of electromagnetic and mechanical finite-element calculations can be applied. Moreover, this algorithm allows to describe the transitional state between both fixed and loose bars in dependence of the electrical bar currents in an efficient way.