Validation and Application of Magnetic Sub-Model Techniques in Turbogenerator End Zones for Local Eddy Current Calculation in Roebel Bars

Applying a novel magnetic sub-modeling technique allows resolving local phenomena such as eddy currents in electric machine components while incorporating effects due to magnetic fields arising from larger machine parts. Employing this procedure to turbogenerators gives the opportunity to study effects of a rotor's magnetic field impinging upon and penetrating individual copper strands of stator Roebel bars at core ends. It should be noted that the magnetically relevant end region of examined non-salient pole synchronous machines extends to several meters, whereas the complex geometry of a Roebel bar is four to five orders of magnitude smaller. This article highlights the significance of step iron design for joule heating inside stator bars and describes the mathematical framework of the applied procedure. This cutting-edge method enables accurate calculation of resulting heat generation rates due to the described phenomenon with high resolution for different end zone designs.