Power output to electric traction drive systems varies over a wide range during real-world operation. As a result, the inverters, responsible for converting direct current battery (DC) to alternating current (AC) for electric motor operation, experience temperature changes that are important to consider in thermal design of the whole system, as well as implications for reliability in actual use. Because of the implications of temperature on device & system reliability, it is necessary to design appropriate thermal management systems to control their temperatures to meet product reliability goals. This study utilizes US Environmental Protection Agency standard driving schedules as case studies in how driving characteristics result in power module temperature profiles during operation for various heat removal schemes and design efficiencies. The temperature profiles obtained in this study clearly demonstrate a strong relationship between motor power output and inverter heat sink temperature. Moreover, when integrated with various degrees of road incline, the driving schedules show how road and elevation also impacts the need for various cooling technologies. This information can be integrated into use condition analyses for predicting reliability of the electronic components using reliability models developed from accelerated testing and qualifications to ensure the proper certification envelope is demonstrated for any given vehicle and environment, as well as demonstrate the effectiveness of cooling methods for determination of technical and economic feasibility.

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