Lifetime Prediction of IGBT Modules in Suspension Choppers of Medium/Low-Speed Maglev Train Using an Energy-Based Approach

Maglev trains attracted to suspend above tracks without mechanical contact is a promising type of track transportation. Suspension choppers with levitation magnets resembling wheels of traditional trains or tires of automobiles are responsible for levitation and support of maglev trains. With successful launch of the first Chinese medium/low-speed maglev line, lifetime prediction of power devices in suspension choppers becomes a crucial topic. This paper analyzes the lifetimes under two typical daily mission profiles of suspension choppers. Using look-up tables of IGBT/diode losses, a widely used RC thermal network is established. A test rig is built to measure the IGBT/diode transient case temperature and extract the thermal impedance of a heat sink. Therefore, the junction temperatures under these typical mission profiles are estimated. Using comprehensive equations to describe solder behavior, the stress-strain curves under different temperature profiles can be plotted by means of Clech's algorithm. Finally, an energy-based approach is utilized for lifetime evaluation. The daily mission profile where maglev trains operate without landing during operation hours is expected to survive much longer.