Permanent-magnet-free Variable Flux Reluctance Machines: Towards a Nonlinear Magnetodynamic Modeling Framework for Heavy-duty Applications

Nonlinear modeling of soft-magnetic laminated steels is critical for electromagnetic devices operating under magnetic saturation. Although it is possible to introduce the single-valued saturation curve of the soft-magnetic material in the 2-D modeling utilizing an iterative nonlinear solver, the modeling of dynamic magnetic field intensity components, i.e. eddy current and excess fields, requires solving the diffusion equation in 3-D. This article proposes a novel 2-D nonlinear finite element analysis coupled with the dynamic field components using the weak formulation. The proposed technique is applied to a variable flux reluctance machine to develop 100 Nm electromagnetic torque for heavy-duty applications. It is observed that the local flux density discrepancy between the proposed magnetodynamic and conventional magnetostatic models reaches 0.5 T, which causes a 51% discrepancy in the iron loss calculation.