Losses and thermal calculation of IGBT and FWD in PWM inverter for electric engineering maintenance rolling stock

In this paper, a basic design scheme of electric engineering maintenance rolling stock (EEMRS) is briefly described, which is composed of six power converters. In order to reduce the size of heatsink and increase the energy conservation and efficiency of power converters, the thermal resistance model of IGBT module and heatsink, and its thermal equivalent circuit are presented. A calculation method of losses in insulated gate bipolar transistor (IGBT) and freewheeling diode (FWD) in PWM inverter is given in detail, in which a new modulating function is introduced on the basis of space vector pulse width modulation (SVPWM) method. IGBT and FWD average losses expressions are deduced from the function. Moreover, a foster model is depicted considering the power devices junction temperature ripple. Finally, a calculation example is presented, the computational results are close to simulation. The results show that the junction temperature of FWD is higher than that of IGBT. It means that both of them in IGBT module must be taken into account when designing heat dissipation system.