Implementation of PM Step Skew Technique to Optimum Design of a Transverse Flux PM Generator for Small Scale Wind Turbine

Abstract

Basic Transverse flux permanent magnet generators (TFPMs) are considered for direct drive wind turbine applications because of having high value of torque density. However, the presence of cogging torque in TFPMs is troublesome in wind turbine applications. This paper implements step skewing technique to eliminate the cogging torque of the TFPM. The analytical approach is presented to formulize the optimum skew angle validated by both finite element method (FEM) and magnetic equivalent circuit (MEC) method. The design algorithm of the TFPM based on MEC modeling is presented including the step skew and iron saturation effects. The MEC results are compared by FEM in terms of accuracy and time consumptions. The MEC method is ten times faster than FEM and it also shows acceptable accuracy. In order to achieve the optimum design, Taguchi design of experiments is used to optimize the TFPM torque characteristics.