Brushless doubly-fed induction machine (BDFIM) has recently gained considerable research interests due to its promising features when incorporated as wind generator or variable speed drive. The BDFIM has two three-phase stator windings with different pole-pair numbers and excitation frequencies. The performance of the machine is based on the magnetic cross-coupling of rotating fields produced by the stator windings through a special squirrel cage rotor. Contrary to the conventional induction machine (IM), the rotor slip and frequency are high throughout the operating speed range. Hence, the rotor core loss cannot be ignored in the steady-state analysis. Although the core loss components have much more study of BDFIM. In this study, analytical expressions are individually derived for a number of core loss components caused by the complicated nature than those of an IM, the precise calculation of these components is important especially on the efficiency each stator winding field. Then, the modified steady-state electric equivalent model is developed by considering the components. The experiments and finite element analysis based on a 3 kW prototype BDFIM verify the accuracy of the proposed model.

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