In this paper, a new optimized rotor design for Brushless Doubly Fed Machines (BDFMs) is proposed. The BDFM is considered as an attractive generator particularly for offshore wind power generation and also as a replacement for doubly fed slip ring induction generators. This is due to its higher reliability and lower maintenance reported in the literature. It is shown in this paper from the study of the magnetic field distribution in the rotor core that the conventional design of the BDFM rotor

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... ron core can be modified, leading to a lighter machine. The proposed design method is supported by an analytical study and its practicality is validated using 2-D Finite Element (FE) analysis. A 250 kW experimental BDFM with frame size D400 is considered as the prototype machine. Index Terms--Brushless doubly fed machine (BDFM), rotor back iron, finite element analysis (FEA), magnetic circuit, iron saturation, magnetic flux density.