A novel analytical approach and finite element modelling of a BDFIM

Nowadays many wind turbines use a doubly fed induction machine (DFIM) as a generator (DFIG). The brushless DFIM (BDFIM), however, has increased fault handling capabilities and suffers less from reliability issues. This paper presents a different method of analytically evaluating the BDFIM. This is done by analyzing the flux density produced by the two stator windings and the interaction with the nested loops of the rotor. Subsequently FEM is used to verify the analytical findings and analyze the behavior of the machine. Additionally several design parameters of the BDFIM such as the pole pair combinations and the number of loops per nest are evaluated. General rules of thumb regarding these design parameters are presented.