Electric machine design and selection for General Motors e-Assist Light Electrification Technology

The integrated starter generator replaces conventional starter and alternator with one electrical machine handling both functions. Start/Stop functionality, vehicle launch assistance and higher speed transient power supplementing enhances the vehicle performance at the lower fuel consumption rate. This functionality requires the electrical machine to provide high starting and launch assistant torque in motoring mode and relatively high power capability over the wide speed range for battery charging. The overall cost of the system is the underlining concern and crucial part of the design optimization. This paper focuses on advantages of induction machines in automotive industry and an approach to design a cost effective electrical machine for belted starter-alternator application. Design optimization of the induction machine is described to achieve desired performance including; rotor bar count, solid conductor (bar winding) vs. stranded winding design, rotor bar shape optimization and finally performance maps for the electrical machine including both, predicted and measured results. Thermal study of the machine is also presented as well as the NVH consideration in the design selection.