Research On Failure Modes Of Press-pack IGBT Devices Used In DCCB

Press-pack IGBT(PPI)devices have the advantages of double-sided heat dissipation,failure short-circuit,and convenient series connection compared to IGBT(Insulated Gate Bipolar Transistor)module.They are very suitable for use in converter valves and DCCB(direct current circuit breaker).At present,many scholars have carried out a lot of research on the failure mode of PPI devices for converter valves,but there are relatively few researches on PPI for DCCB.Due to the different working conditions of the converter valve and the DCCB,the research results of the two cannot be simply directly equivalent.Therefore,it is necessary to conduct in-depth research on the failure mode of PPI for DCCB.In this paper,starting from the common failure modes of PPI,combined with circuit breaker operating conditions,four failure modes are analyzed:electrical failure,thermal failure,mechanical failure,and cosmic ray failure.Thermal failure and mechanical failure are more common in PPI devices for DCCB,and they are the focus of this article.Based on the finite element method,a simulation model of the PPI sub-module containing two contact pairs is constructed.The effect of setting the contact pair is to make the two boundaries not always fixed together.They may be separated and the contact thermal resistance and contact resistance on the boundary will change in real time as the pressure changes.This will make the model closer to the actual situation than the existing model.However,the contact pair leads to poor model convergence,and how to make the model converge is a difficult point.This article simulates the short-circuit current in different situations.The analysis shows that due to the short duration of the short circuit,the heat does not have enough time to conduct outwards.The temperature is highest during the second commutation,and overheating failure is most likely to occur at this time.Due to the effect of thermal expansion,the stress and strain of the chip also reach the maximum at this moment.Multiple short-circuit current impacts may cause chip fatigue failure.Combined with the simulation results,this paper proposes two equivalent methods for thermal failure and mechanical failure.The two equivalent methods use the Arrhenius model and the Coffin-Manson model as the aging life model respectively.An accelerated stress aging test is designed based on the life model.This test is different from the conventional power cycle and other aging tests,and uses short-circuit current as the accelerated stress.This is closer to the actual working conditions of the PPI devices DCCB.