978-1-4799-4161-2/14/$31.00 ©2014 IEEE Electromagnetic Design and Finite-Element Analysis of an Axial-Flux Permanent-Magnet Machine Adrian Augustin POP Departament of Electroenergetics and Management Technical University of Cluj-Napoca Cluj Napoca, Romania Augustin.POP@enm.utcluj.ro Mircea M. RADULESCU Departament of Electrical Machines and Drives Technical University of Cluj-Napoca Cluj Napoca, Romania Mircea.Radulescu@emd.utcluj.ro Horia BALAN Departament of Electroenergetics and Management Technical University of Cluj-Napoca Cluj Napoca, Romania Horia.Balan@enm.utcluj.ro Mihai CHIRCA Departament of Electrical Machines and Drives Technical University of Cluj-Napoca Cluj Napoca, Romania mihaichirca@mail.utcluj.ro Valentin ZAHARIA Departament of Electrical Machines and Drives Technical University of Cluj-Napoca Cluj Napoca, Romania Valentin.ZAHARIA@mae.utcluj.ro Abstract— This paper approaches the electromagnetic design and finite-element analysis of an axial-flux permanent-magnet (AFPM) synchronous generator for small-scale wind turbines. The study is conducted to find a good-performance and cost- effective electric generator topology for micro-wind power application. The proposed double-sided two-stators-one-rotor AFPM synchronous generator with non-overlapping concentrated slotless-stator-winding and ironless PM-rotor disk could be the machine of choice in grid-connected or stand-alone small-scale wind energy conversion systems. Keywords—axial flux; permanent magnet; wind energy; I. INTRODUCTION Despite their great potentials small-scale wind turbines reveal low penetration in the renewable-energy production market, as compared with large utility-size wind turbines, due to the following main reasons [1]: (i) micro-wind turbines operate mostly in low-wind-speed areas, experiencing self- starting problems, which have negative consequences on the energy yield; (ii) the cost per installed kW of current stand- alone micro-wind turbines is much higher than that for large wind turbines; (iii) micro-wind turbines require good technical skills and rather complex equipment in manufacturing and maintenance processes, which increase their installing and operational costs. Many micro-wind turbine manufacturers use direct-driven generators [2], thus avoiding mechanical gear, reducing size of the entire system, lessening noises and lowering installation and maintenance costs. However, a direct-driven micro-wind generator has to operate at very low speeds in order to match the wind turbine speed, and to produce electricity within a reasonable frequency range; hence, the micro-wind generator has a rather big size, and must be designed with a large number of poles. Axial-flux permanent-magnet (AFPM) synchronous generators are increasingly being used in the last decade for direct-drive small-scale wind turbine applications [3, 4]. Compared with conventional radial-flux PM machines, the AFPM synchronous generators have the advantages of more compact structure due to the flat shape with short axial-length, larger power-to-weight ratio and torque density, more flexible PM-field and armature-winding design, better cooling and modular construction. The drawback of a low-speed direct- driven AFPM synchronous generator is that it requires larger diameter, which affects the material cost of the machine [5]. The double-sided two-stators-one-rotor AFPM synchronous generator topology with non-overlapping concentrated slotless-stator-winding and ironless PM-rotor disk is considered in this paper, which is organized as follows. In Section II, the preliminary electromagnetic design of the proposed double-sided internal-rotor AFPM synchronous machine for use as a direct-driven generator with small-scale wind turbines is addressed. Section III presents the 3-D finite- element field analysis and simulation results for the double- sided AFPM synchronous generator design evaluation. Conclusion is drawn in Section IV.