A Study on Stator Winding Loss Distribution of Additively Manufactured Coils in Fractional Slot Concentrated Windings

This paper focuses on loss distribution and sensitivity analysis in Fractional Slot Concentrated Windings (FSCW) with Additively Manufactured (AM) conductors. This winding with its integrated Heat Pipe (HP) cooling system is one of the critical building blocks of a Surface Permanent Magnet (SPM) machine, enabling an active Specific Power (SP) of 23 kW/kg at a takeoff efficiency of 92% for aviation propulsion. The 250 kW, 5000 rpm, 36/30 slot/pole, 1.25 kHz machine has been developed in accordance with ASCEND (ARPA-E) requirements. The combination of AM coils, integrated HPs, high rated frequency, and FSCW introduces a new phenomenon in the loss distribution pattern which will be investigated in this paper. The paper shows that losses in the conductors of an individual phase are non-uniform in the circumferential direction (in addition to the radial direction). It discusses the flux leakage, armature reaction and their impacts on the AC loss components. The paper additionally studies the effect of the design parameter (tooth tip offset, tooth tip angle, winding configuration, AM conductors) on the loss distribution pattern, and discusses solutions to balance the losses.