Windings, design and optimization of electrical machines for hybrid traction applications

This research consists of three main parts. The first part extends research on AC windings by utilizing the star of phasors (star of slots) for winding topologies with various numbers of turns per coil or per coil side, as well as for star-delta windings. Following a mathematical approach, possibilities and restrictions on electromagnetic improvements are discussed and main theorems and design guidelines are presented. It is shown that several windings found in the past possess a similar underlying structure, allowing to design more, yet unknown windings. Closed analytical equations for winding factors are derived and several winding examples are illustrated. The second part contributes to design possibilities of high pole PM machines for hybrid traction applications. Due to high electrical frequency, machine design focuses on low iron and AC losses. The design procedure as well as main design considerations are highlighted, showing trade-offs and final decisions. Following these findings, a 36-slot 28-pole PM machine with irregular air gap, shaped tooth tips and a concentrated winding in delta connection is designed. Numerical and analytical calculations for the electromagnetic, mechanical and thermal domain are presented. The third part validates derived machine design by measurements performed on a full scale prototype. Manufactured PM machine, test-bench and performed measurements are described in detail. Results are depicted and compared to predicted values. Deviations are analyzed and further optimization possibilities are discussed. It is shown that derived design fulfills set project requirements on torque and powcer and shall be improved further regarding AC losses.