Improved Short Time Thermal Transient Model and Testing Procedure for High Power Density Motors

The Short Time Thermal Transient (STTT) testing procedure is a fast and accurate method for evaluating the winding thermal capacitance and winding to back iron thermal resistance of AC motors. This procedure has been extensively validated for industrial motors and involves short duration DC excitation with the motor phases connected in series, followed by data analysis based on a first-order lumped parameter thermal network. However, when the phase terminals are not fully accessible, such as in motor drives for traction, the all-in-series canonical STTT procedure cannot be used. Additionally, for highly loaded traction motors, the estimated thermal parameters are more dependent on the duration of the DC excitation, rendering the existing first-order STTT model impractical. To address these issues, this paper presents and improved STTT model, the related testing sequence and data processing approach having a wider and more general, to be used in a wider range of applications. The new approach is validated through experimental results.