Analysis of asynchronous machines for direct drive wind power generation

Abstract

The asynchronous machine is not adopted in direct-drive applications, that is, high-power low-speed applications. The reason is that a machine with a high number of poles is disadvantageous since it often requires a fractional-slot winding, which is unsuitable since it cause high MMF space-harmonics in the air-gap. However, this paper shows that in a doubly fed asynchronous machine, a proper choice of the number of stator and rotor slots minimizes the interaction between stator and rotor MMF harmonics, limiting losses and torque ripple. The design strategy of the doubly fed asynchronous machine is explained and the results are commented, highlighting advantages and drawbacks of the proposed solutions

Design and Analysis of Advanced Nonoverlapping Winding Induction Machines for EV/HEV Applications

“…To be able to mitigate or eliminate some MMF harmonics induced in the rotor windings, a double-fed (wound-rotor) IM with multi-layer FSCWs is introduced in Reference [20]. In order to improve the performance of the IMs with FSCWs, some other different methods, such as single-and multi-phase FSCWs [19,21], outer-rotor topology with modular stator windings [22], outer rotor IM with multi-layer FSCWs wound around two and three layers of stator slots [10], multi-layer toroidal windings [8,11], stator cage windings [17], combination of different numbers of turns per one coil side and combined star-delta phase connection [16], and two sets of FSCWs with a dual slot-layer stator structure [23] have been investigated in the last decade.…”