In power electronic applications the expected lifetime is an important issue. This paper focuses on the elongation of the expected lifetime of IGBT-power-modules. Temperature swings caused by alternating operation conditions are the major influencing factor. The temperature swings can be reduced by increasing the power losses in low load conditions. This is realized by a model based junction temperature control system. Possible correcting variables are the variation of the switching frequency and the presetting of a current amplitude. Each correcting variable has its benefits and drawbacks. This paper presents a model based junction temperature control system which combines these two correcting variables in a beneficial manner. The functionality is demonstrated on a three phase two level inverter equipped with opened and blackened IGBT power modules feeding a PMSM The correcting variables have no negative influence on the demanded output power of the PMSM.