The simple and robust construction of reluctance machines and the fact that they need an unsophisticated control have reignited interest in these machines. The constructional modifications and new configurations such as brushless doubly fed reluctance machines (BDFRM) show superior performance compared to their traditional counterparts, especially in variable speed applications such as pumps and wind generators. The design of BDFRM is different from other machines, as there are unusual pole combinations of stator and rotor besides the absence of a winding on the rotor. The operation and performance of the machine greatly depends on the mutual interaction between the stator windings. This interaction is modulated by the rotor with increased saliency. This paper examines a few critical issues in the design of BDFRM. Design optimization is performed using the gradient method from non-linear programming for 6-4-2 pole and 8-6-4 pole configurations of BDFRM. The performance of these optimized machines is examined through finite element analysis employing MAXWELL 16 software and then compared with 2 kW prototypes constructed for laboratory use. A comparative analysis of the two configurations are presented and experimental results show that the BDFRM with the 8-6-4 ducted rotor is superior to BDFRM with the 6-4-2 reluctance and ducted rotor configurations.

For higher generation of electricity from wind, efficient and cost-effective generators are being developed. Brushless doubly fed reluctance generator with a partially rated converter is one of the promising generators for wind power applications especially for offshore plants. All grid connected wind generators must comply with local grid codes and the prime requirement is reactive power capability. The capabilities of brushless doubly fed reluctance generator need to be investigated under grid connected operation. Therefore, a 2 kW laboratory prototype of this machine is optimally designed and constructed to study generator operation and reactive power capability. This article discusses the development of capability curve for brushless doubly fed reluctance generator from the well-known machine equations in d–q frame. The capability curves of this machine is also obtained from experimental investigations carried out on the 2 kW prototype. The results show that capability curve of brushless doubly fed reluctance generator looks to be ‘V’ shaped and suitable for wind generator applications.

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