Improvements in Brushless Doubly Fed Reluctance Generators Using High-Flux-Density Steels and Selection of the Correct Pole Numbers

The brushless doubly fed reluctance machine consists of a stator containing two winding sets if different pole number linked by a reluctance type of rotor. This paper studies the magnetic performance of machines with different pole combinations aimed for use in a 2 MW wind turbine. This paper investigates the use of high-flux-density steels in order to observe the influence on torque density. An increase of 27% in performance is observed. In the second part of this paper, the unbalanced magnetic pull on the rotor is investigated. It has been suggested that a 4/6 pole may be suitable for this application, but it is illustrated that the rotor experiences high radial forces that may negate the use of this type of machine due to excessive bearing wear over a prolonged period.