A Study on the Novel Design to Improve Efficiency of Wound Field Synchronous Machine

This study describes the research to improve the performance of motor generator for integrated starter generator (ISG) mounted on ecofriendly vehicles. The ISG must be able to start the engine by high torque at the starting mode and generate electric power at the generating mode. In particular, the existing automotive generator is a field winding alternator of CLAW POLE structure, so wound field synchronous machine (WFSM) was used in early ISG. However, it is difficult to control the starting of WFSM with instantaneous high starting torque required at the start and high field current is applied to field windings to generate the magnetic flux. But high field current generates high heat shortening the life of the device. Therefore, consequent pole wound field synchronous machine (CPWFSM) as a novel structure is proposed in this article. It is possible to generate instantaneous high torque easily at starting because of permanent magnet (PM). In the generating mode, CPWFSM can generate power in a wide operation speed that is proposed by taking advantage of WFSM. CPWFSM consists of consequent pole and field winding in the rotor. So it generates high torque with high responsiveness at starting compared with WFSM and it has the advantage of generating output power using low field current at various speed areas because of PM. Simulation of CPWFSM and WFSM is performed by finite-element method (FEM) of ANSYS Electromagnetic Suite (EM 19.0) software, and the experimental results are compared by the dynamo experiment.