Application of finite element method in design of a 50 kW direct drive synchronous generator for variable speed wind turbines

This work presents the electromagnetic design process and methodology for a direct drive synchronous generator for variable speed wind turbines, with an emphasis on the applications of the finite element method (FEM) in electromagnetic design. The finite element method has been used for fine-tuning and verifying the design, as well as for evaluating the performance characteristics such as no-load saturation curve, voltage and current waveforms. Major electromagnetic quantities calculated from the finite element method include flux density, flux, inductance and back emf at various excitation conditions. The designed 480 V, 50 kW, 80 rpm synchronous generator has been produced, installed and tested. Test results are reported in the paper. With the agreement between the FEM analyses and the test results, the methodologies used in the design process have been verified.