Maximum Winding Temperature Predictions in Electrically Excited Synchronous Machines

Although resistance-estimation-based method is widely used for winding temperature monitoring in electrical machines by using copper temperature dependence, its primary limitation is the inability to predict maximum temperatures. To address this issue, this paper proposes a method that utilizes the average coil temperature as the input variable to predict the maximum winding temperature caused by the copper loss for both overlapping and non-overlapping winding layouts, based on the conduction heat transfer principle. Meanwhile, a simple approach is developed to distinguish the thermal states of active and end windings for overlapping windings by installing a thermal sensor on the end-winding front surface. This enables the separation of average active- and end-winding temperatures, allowing for rapid maximum temperature estimation using simple equations related to winding geometric and thermal parameters. The proposed method does not require knowledge of machine losses and thermal parameters outside the winding region, which is validated numerically and experimentally based on a prototype electrically excited synchronous machine.