Effect of Asymmetric Layout of IGBT Modules on Reliability of Motor Drive Inverters

Power electronics inverters are one of the major failure sources in motor drive systems, and power devices are one of the main causes of the power electronics inverter failures. Typically, an insulated-gate bipolar transistor (IGBT) module has multiple power devices due to some technical and cost advantages. This kind of configurations could have an asymmetric internal layout, which may lead to different thermal loadings and thereby lifetime difference of the power devices. Therefore, both the power rating and the lifetime of inverters are limited by the most stressed device. However, generally common data are provided for all devices in the datasheet and this may cause improper design of the inverters in terms of the lifetime and the power rating. In this paper, an effect of an asymmetric layout of IGBT modules on the reliability of motor drive inverters is studied based on a three-phase motor drive application with a 600 V, 30 A, three-phase transfer molded IGBT module. The thermal impedances of six IGBTs are investigated and its effect on thermal loadings of power devices is studied under the given mission profile. Then, their lifetimes are estimated and compared. Finally, this effect is verified by the experiments.