Analysis and Implementation of New Ironless Stator Axial-Flux Permanent Magnet Machine With Concentrated Nonoverlapping Windings

This paper presents the integrated design and analysis of a new axial-flux permanent magnet (AFPM) machine, which consists of an ironless stator with double-layer concentrated nonoverlapping windings and twin external rotors with Halbach-array PMs. A general sizing equation based on fundamental theory, easily adjustable for ironless stator AFPM machine with concentrated windings, is derived to obtain preliminary parameters. Then, by using three-dimensional (3-D) finite element analysis (FEA), the optimization of a primary machine is implemented. A precise and fast calculation method based on a 3-D FEA model is proposed to confirm the eddy-current loss for ironless stator winding. By making a tradeoff between dc current loss and eddy-current loss of Litz wire for winding, the efficiency is further improved for a high frequency operation. Despite using Halbach-array PMs, a certain thickness of a rotor yoke is recommended to increase air-gap flux density. Finally, a prototype machine is developed, experimented, and evaluated. The test results reveal the strong overload and heat dispersal capacity of the proposed stator ironless AFPM machine with the maximum efficiency of 98.5%. Measured performances of the manufactured prototype verify the validity of the proposed analysis method and FEA results.