Experimentally Calibrated Thermal Stator Modeling 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 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 a machine with a distributed winding. Several alternate slot liner and impregnating materials have been evaluated to maximize the heat transfer from the winding body into the machine periphery, and a total of nine stator section samples have been manufactured and tested. The performance tradeoffs between the various combinations are discussed in detail alongside their ability to satisfy the design requirements. Based upon these experimental results, the most promising designs have been selected for transient duty analysis against the design specification. A lumped parameter thermal model has been used for this purpose and calibrated using the data from the subassembly testing. Experimental results on the full machine assembly are presented, showing good correlation with the motorette calibrated thermal model.