Experimentally calibrated thermal stator modelling of AC machines for short-duty transient operation

This paper presents an approach to the thermal design of an AC machine where the application requires a low-duty transient operation. To provide accurate temperature predictions the design process has been informed with experimental data from tests on a stator-winding sector (motorette). These have been shown to be a time and cost-effective means of calibrating the thermal model of a full machine assembly, prior to manufacture of the final design. Such an approach is usually adopted in design analysis of machines with a concentrated winding topology. Here, the motorette testing has been extended to machines with distributed windings. In the interest of improving heat transfer from the winding body into the machine periphery, several alternative slot liner and impregnating materials have been compared. A total of nine stator section samples have been manufactured and evaluated. The performance trade-offs between the various combinations are discussed in detail alongside their ability to satisfy the design requirements. Based upon these experimental results three stator segment samples have been selected for transient duty analysis. A lumped parameter thermal model has been used and calibrated to match the performance of the experimental samples. This is turn has been used to predict the transient thermal performance of the full machine assembly, for the design specification. The most promising motorette variant has been selected for machine prototyping.