Impact of Stator Segmentation on the Performance of Aerospace Propulsion Machines

Electric machines offering a high power density are required for aerospace applications. Soft magnetic material with a high saturation flux density is one of the key component which is required to realize these power density targets. The need for a high saturation flux density necessitates the use of cobalt iron lamination over the conventional silicon steel. However, cobalt iron is very expensive i.e. order of 10 in comparison to silicon steel. Stator segmentation is identified as an appropriate method to reduce the wastage and cost associated with lamination. Consequently, in this paper, stator segmentation is analyzed on a 1.35 MW, 16-pole 48-slot propulsion machine. The impact of manufacturing is accounted by controlling the resulting airgap between the segmented structures. Electromagnetic performance for various segmented topologies are compared in terms of torque, torque ripple, and iron loss. Average torque is found to degrade by nearly 10% with an increase in the number of stator segments and the thickness of resulting airgap. Therefore, a tight tolerance is required between the segmented parts to retain the electromagnetic performance. On the other hand, this increases the cost of fabrication and nullifies the benefits offered by stator segmentation.