Robert Boschgmbh

Stefan Gaab

Michele Hirsch

Torsten Heidrich

Markus Kretschmer

Tobias Werner

Christian Djonga

Michael Heeb

The invention relates to a method for operating an electrical machine () controlled by an inverter (), wherein the inverter () comprises half-bridge branches (-U,-V,-W) having power components in the form of controllable power switching elements () and power diodes () respectively connected in parallel therewith, wherein each of the half-bridge branches (-U;-V;-W) is arranged on a separate semiconductor module (-U;-V;-W), which are arranged jointly on a baseplate (), wherein the phase currents (1_U, 1_V, 1_W) flowing through the half-bridge branches (-U,-V,-W), the voltages present at the power components and temperatures (t_Sens_U, t_Sens_V, t_Sens_W) on the semiconductor modules (-U,-V,-W) are determined, from the current (1_U; 1_V; 1_W) respectively flowing at a power component and from the voltage respectively present a power loss (P) is calculated for each of the power components, from the power losses (P) a relevant temperature swing (&#x394;t; &#x394;t_Sens) is determined for each of the power components and for temperature sensors (-U,-V,-W) serving to determine the temperatures on the semiconductor modules, a temperature (TempCooler) of the baseplate () is determined from the determined temperatures (t_Sens_U, t_Sens_V, t_Sens_W) on the semiconductor modules (--V,-W) and the determined temperature swings (&#x394;t_Sens) at the temperature sensors (-U,-V,-W), and a torque or a power of the electrical machine () is determined in a manner dependent on the determined temperature swings (&#x394;t) and the determined temperature (TempCooler) of the baseplate ().

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Ludwigsburg, Germany

Stefan Gaab