Semi-Analytical Model for Skewed Magnet Axial Flux Machine

The compact design, and high power density distinguishes axial flux permanent magnet (AFPM) machine from other variants of permanent magnet machine. Recent research focused on the development direct drive axial flux machine in several practical area such as wind power generators, electrical vehicle drives, and servo applications. However, the interaction between PMs and slots, produces undesirable cogging torque. This torque produces mechanical vibration, noise, torque ripples, voltage ripples and speed ripple in machine. Enormous design techniques including skewed slot, skewed magnet, axillary slots, magnet pitch ratio and many more have been reported in literature for its reduction. However, these design techniques adversely affects the pattern of no load magnetic field, and consequently, machine performance. In this paper, an analytical model is developed to evaluate the effects of magnet skewing on the performance of AFPM machine. The no load magnetic field, and cogging torque are evaluated for three different types of open slots stators topologies viz. type 1: trapezoidal slot, type 2: Parallel slot, and type 3: trapezoidal slot are investigated. The analytically obtained results are compared with finite element analysis (FEA) for the validation. Finally, the cogging torque of skewed and unskewed AFPM machines are compared.