Transient thermal network model for train-induced wind cooling dry-type on-board traction transformer in electric multiple units

Thermal characteristic is one of the key performances of dry-type on-board traction transformer(D-OBTT),which directly affects the operation safety of the new generation electric multiple units.However,due to the particularity of train-induced wind cooling mode of D-OBTT,the existing efficient thermal modelling methods cannot be used under fluctuating air velocity and load.A time-saving transient thermal model for D-OBTT is proposed.First,the framework of the transient thermal network model(TTNM)is proposed considering the coexistence of non-fully and fully developed state of the train-induced wind and the addition heat flow in the solid domain.Then,a novel formula for calculating the length of non-fully developed section considering the geometric dimensions and heat flux density is proposed based on computational fluid dynamics(CFD)parametric sweeps for the first time.The accuracy of TTNM is validated by a D-OBTT experimental setup,and the time consumption is significantly reduced compared with CFD.