Optimization of Magnetic Circuit for Brushless Doubly Fed Machines

This paper presents an optimized design method for the magnetic circuit of brushless doubly fed machines (BDFMs). The BDFM is an attractive electrical machine, particularly for wind power applications, as a replacement for doubly fed slip-ring generators. This study shows that the conventional design methods for the BDFM stator and rotor back iron can be modified, leading to a lighter and smaller machine. The proposed design concepts are supported by analytical methods, and their practicality is verified using two-dimensional finite-element modeling and analysis. Two BDFMs with frame sizes D180 and D400 are considered in this study.