On Analytical Modelling of the Air gap Field Modulation in the Brushless Doubly Fed Reluctance Machine

The Brushless Doubly Fed Reluctance Machine (BDFRM) is receiving an increased attention of the research community thanks to its potential as alternative drive for variable speed applications, both as motor and generator. Currently, the sizing of the BDFRM in literature is based on the model of an ideal axially laminated rotor (ALR) and discrepancies are hidden in compensation factors which are in turn tuned with a Finite Element Analysis (FEA). This paper proposes an analytical framework to accurately model the air gap field modulation, and by extension the torque density, of the BDFRM with ducted segmental rotor (DSR) and salient pole rotor (SPR). These results are verified with FEA and validated on a BDFRM prototype.