Analytical Model for Real-Time Junction Temperature Estimation of Multi-chip Power Module in PWM operation

An analytical electro-thermal model of a multichip power module is described in this paper. The proposed model is intended to be used during in service conditions inside a motor drive for remaining useful lifetime calculation, in combination with a thermal cycle counting algorithm. This model is applied on a motor drive power converter mounted on its air-cooled heatsink. It offers fast calculations of the junction temperature, taking into account the self-heating and the cross coupling effect. The calculations are based on averaged power losses obtained from the expression of the duty cycle, and analytical expressions of the system thermal impedances, which are measured by fast optical fiber temperature sensors. The model results are finally validated based on experimental measurements, which are carried out on a motor test set up at one operating point of the power converter, when the THI-PWM switching technique is used.