Evaluation of thermal condition of permanent-magnet starter-generator in continuous operation mode

The concept of fully electrified and hybrid vehicles allows to replace the hydraulic, pneumatic and mechanical on-board systems of electric drives cars, which leads to a reduction in emissions and fuel consumption. An important component of this concept is the use of one starter generator (SG) instead of two separate electric machines for starting the engine and powering on-board consumers. Permanent magnet (PM) machines are good candidates for use as SG in an automobile due to advantages such as high power density, torque, and energy efficiency. This article presents a thermal analysis of the generator mode of SG operation. First, the necessity of conducting such a study in order to obtain a forecast of the maximum temperatures of the winding and magnets is justified. Next, we describe the formulation of the problem of 2-D modeling of the temperature field in convective heat exchange with the environment under conditions of natural heat removal and forced blowing of the finned housing. As a result of FE modeling, the temperature state of the active parts of the SG is estimated and recommendations are given for the choice of insulating and magnetic materials.