A Methodology to Extract Thermal Impedance Distribution along Whole Heat Transfer Path

Abstract

Motor drive systems with three-phase inverter circuits are becoming common in order to meet demands of high controllability and lower power consumption. Adequate thermal design is vital to allow integration of the motor drive system with lightweight, small inverters. To realize adequate thermal design, we must understand the heat transfer structure of the system. In this paper, we propose a methodology to obtain a thermal impedance distribution along the heat transfer path, as the heat transfer structure. Firstly, the thermal impedance distribution expression utilizing a Cauer thermal network is explained. Secondly, two types of test boards with a MOSFET sample are prepared and are measured to obtain the transient junction temperatures. After that, the thermal impedance distributions are extracted from the measurement results and these results are discussed.