Shape Optimal Design of 1 kW-Class Outer Rotor Type Generator with Axial-Flux Permanent Magnet Using Electro-Magnetic Analysis

An urban wind turbine with small scale generator adopts darrieus type vertical blades which make possible to start easily turbine and to produce electricity even under the conditions of weak and irregular winds. The generator for a highly efficient power production should be required, so that the design using a direct-driven permanent magnet synchronous generator has been considered owing to reduction of additional mechanical losses during the power production. In this study, 1 kW-class outer rotor type generator with two stage was proposed, in which an axial-flux permanent magnet was applied to 10 pole/12 slot combination and distributed windings with double layer. Finite element model was prepared by taking into account of single-stage and half geometry of the generator, and then electro-magnetic analysis was carried out to calculate the active powers under given loading conditions and electrical parameters. To meet the requirement of the target specification such as the active power with 250 W, the shape optimal design was conducted, in which 7 design variables were varied and design space was explored under a constraint of weight minimization. As a result, the optimized design variables of the generator were found to satisfy the target specification, and the weight of the generator was maintained at the same level of that for the initial design model.