3D FEM approach to study the physics of inter-bar currents in induction machines

Abstract

The proposed numerical model is used to study the physics of inter-bar currents by investigating the three dimensional field solution. The long-term aim is to get a deeper and more accurate understanding of the physics to be able to further fine tune analytical theories about inter-bar currents. This work is used to verify the model and to get an idea of what can be achieved with it in the future. The geometry, the partial differential equation and specific material properties as substitutes for the rotor lamination are introduced. After that the boundary conditions are presented, including the Neumann condition to replace the whole stator geometry with its winding heads. The closing verification is split up into two steps. In the first step the 3D model is verified without inter-bar currents while a validated analytical tool is used as reference. In the second step inter-bar currents are added and an experiment is used to verify the simulation. As a side result of the verification, the results show that the inter-bar current is affected by two separate convergence effects, depending on the slip and the inter-bar resistance. The results additionally show that a low stacking factor can equalise the influence of a band of different inter-bar resistances on the torque-speed behaviour.