Abstract: Semiconductor modules are used for controlling drive motors such as the electric motors of electric vehicles. IGBT modules are one type of such semiconductor modules. During operation, heat losses arise in the power transistors and the diodes of the semiconductor modules, which causes an increase in their temperature. Therefore, the manufacturers of the IGBT modules recommend that the software of a control unit that controls an IGBT module be provided with a protective function which continuously monitors the temperature of the IGBT module and intervenes as necessary if an unacceptable temperature of a component of the IGBT module is reached. A temperature model is used for the calculation. The manufacturers provide a more accurate higher-order temperature model that however causes an increased amount of computation. According to the proposal, a reduced temperature model is used that is calculated using the balanced truncation method and is optimized for certain working ranges.