Impact of Rotor Flux-Barriers on Coupling Coefficient in a Brushless Doubly-Fed Reluctance Machine

A brushless doubly-fed reluctance machine offers several advantages over a single-port machine since it requires a partially-rated power converter, provides reduced maintenance, and operates without permanent magnets. The complexity of the air-gap magnetic fields due to differing winding-pole numbers interacting with a reluctance rotor have precluded the use of an analytical framework to optimize the rotor. Instead, researchers have relied upon time-consuming finite element analysis (FEA). This paper presents an analytical method to compute closed-form solutions for the mean torque, captured by the coupling coefficient, using a practical circular ducted rotor. The method also accounts for the potential drop across the flux-barriers, leading to a better estimation of mean torque. The model is validated using both FEA and experimental tests.