Magnetic circuit modeling of brushless doubly-fed machines with induction and reluctance rotors

This paper presents a magnetic circuit modeling (MCM) technique for analysis of the brushless doubly-fed machine (BDFM). Two rotor types are considered: the induction type and the reluctance type. The flux density in both the stator and rotor can be calculated by the developed MCM. This is particularly beneficial to the BDFM with the induction rotor since the generated rotor currents may saturate the rotor or stator and this is difficult to foresee at the design stage due to the complex flux patterns in the machine. A coupling factor is proposed to determine the flux coupling between the stator and rotor teeth of the induction type of BDFM. Saturation is also considered in the MCM. Finite element analysis is used to verify the analytical results.