AC Winding Loss Reduction in High Speed Axial Flux Permanent Magnet Machines Using a Lamination Steel Sheet

This paper examines a method of AC copper loss reduction in a single-sided open slotted Axial Flux Machine (AFM) using a Soft Magnetic Composite (SMC) core and a steel lamination sheet to shield the coils from stray fields. This approach is easy to implement for this topology and does not require the use of more complex twisted and Litz type conductors. To improve performance, the machine has a steel lamination sheet placed between the coils and airgap which has been optimized using 3D finite element analysis (FEA) to minimize both coil AC loss and lamination eddy current losses. Concentrated windings are used. These are pre-wound and slide onto the open, parallel sided stator tooth. This method of construction ensures a very high slot fill factor. The 3DFE simulations are validated with experimental tests and this paper shows the method has reduced AC copper loss by harnessing the shielding effect of the lamination sheet. It is found that the higher the conductivity of lamination, the lower the AC copper loss and better efficiency.