Improved Transverse Flux Directly - Driven Wind PM Generator: Optimal Design with Key FEM Validation

Abstract

In an effort to reduce weight and cost of directly - driven wind generators in the 3 MW, 11 rpm range, the paper introduces, “as improved”, an axial - airgap spoke - PM rotor three phase transverse - flux generator with two dual - core circular shape coils per phase and 3 rotors on same shaft. For optimal design - with a unique multi - dimensional objective function including active materials, capitalized losses, costs, inverter kVA costs plus over temperature and demagnetization avoidance constraints, a 3D nonlinear magnetic equivalent circuit (MEC) is used, to keep the optimization design computation time low. Key FEM validations - related to airgap flux density torque production, torque pulsations, inductances - are offered by a surrogate 2D FEM methodology based on a linear sectorial virtual motor model. Results for 3 MW, 11 rpm, reveal a 30% total (global) objective (cost) function reduction by optimization design for an efficiency of 96.69% power factor cosφ=0.665 at 1 total active materials (copper, laminations and PMs) mass of 9345 kg. the results are very promising in comparison with existing regular such PMSGs potentially allowing, in addition, increased voltages up to 20-30 kV per phase with cable - made stator coils, avoiding the voltage matching transformer towards local power grid.