2018-01-0464 Published 0 3 Apr 2018 © 2018 Ford Motor Co LTD; Ford Motor Company.System-Level Investigation of Traction Inverter High-Temperature Operation Xi Lu, Kewei Xiao, Guangyin Lei, and Chingchi Chen Ford Motor Company Citation: Lu, X., Xiao, K., Lei, G., and Chen, C., “System-Level Investigation of Traction Inverter High-Temperature Operation,” SAE Technical Paper 2018-01-0464, 2018, doi:10.4271/2018-01-0464. Abstract In this paper, the high-temperature capability of the traction inverter was investigated by applying coolant with temper - ature much higher than the typical allowed value until the system fails. The purpose of this study is to identify the weakest link of the traction inverter system in terms of temperature. This study was divided into two stages. In the first stage, a series of nondestructive tests were carried out to investigate temperature rise ( ΔT) of the key component above coolant temperature as a function of the outside controllable parameters-i.e., dc link voltage, phase current, and switching frequency. The key components include power modules, gate driver board, gate driver power supply, current sensors and dc link capacitor. Their temperatures were monitored by ther - mocouples or on-die temperature sensors. The result showed that temperature rises of most key components were strongly affected by phase current, moderately affected by switching frequency, and slightly affected by dc link voltage. Therefore, the operating conditions used in the second stage (destructive test) were chosen to stress the phase current only rather than the dc link voltage and switching frequency for better effec - tiveness. In the second stage (the destructive test), the coolant temperature was controlled to increase every a few hours after the temperature stabilized while maintaining the controllable electrical parameters to be the same. Testing results showed that the traction inverter employed in this study can sustain coolant temperature > 105 °C for more than 10 hours, while the IGBT on-die temperatures were measured to be >200 °C. Under this specific condition, the IGBT module is the first component to fail after the coolant temperature was raised to a certain level (>120 °C). On the contrary, many other compo - nents are found to be functioning after the long-time opera - tion at high temperatures. The measurement results were confirmed by the theoretical analysis. 1.  Introduction For hybrid electrified vehicle application, the traction inverter system is usually packaged under the hood, where the ambient temperature could be as high as 105 °C. Although the state-of-the-art design utilizes a dedi - cated low-temperature cooling loop to prevent the inverter from overheating, the electronic components inside are still experiencing much higher temperature than the coolant temperature due to temperature rise caused by the internal loss. Therefore, automotive electronics are critical and required to pass stringent reliability requirements at higher temperatures comparing to most consumer electronic products. There is some literature discussing the key components are capable of operating at high temperatures [ 1, 2]. Understanding each key component’s high-temperature char - acteristics and capability or limitation is the first step. What’s missing in the component level study is the consideration of the ΔT distribution in the traction inverter system and also the thermal coupling effect between components. Consequently, investigating the inverter’s high temperature operating as a whole is the second step towards examining, designing, and developing an inverter with reasonable temper - ature margin and trustable reliability. However, no one has ever reported any experimental results discussing the high-temperature operation of the whole traction inverter system. The difficulty might be related to 1) operating a whole traction inverter is complicated, which involves monitoring equipment, loads, power su