Analytical approximation of the displacement process of Roebel bars

Abstract

The mechanical displacement of Roebel bars inlaid in slots of synchronous machines is caused by forces of electromagnetic and mechanical origin. In each occurring operational state, the mechanical behaviour is affected not only by the forces but also by nonlinear magnetic and mechanical material properties. The presented analytical calculations take into account for this influence appropriate boundary conditions and introduce correction coefficients in dependence of the bar currents. The analytical method for calculating the bar displacement is compared with fully coupled electromagnetic-mechanical finite element analyses whereby the sufficient high accuracy of the analytical results is confirmed.