Torque limitation for an electrical machine

A protective device (40) for an electrical machine (30) is ready to output at a first output (61) for a final excitation current command value input (ESV) a value that compensates for an excitation flux of the electrical machine (30) partially or fully. In a first aspect, the protective device (40) to a second output (62) for switching an inverter controller (80) in an idle operation. In a second aspect, the protective device (40) is to prepare, after a fault has been detected, a command (bAKB) to a converter (20) to which the electric machine (30) is operated to transition to an active short-circuit operation, at least then outputting, (no) is its speed range (NB) when the electrical machine (30) in an upper region. The invention also relates to a converter circuit (20) having a power semiconductor switch module (21) for operating an electric machine (30), wherein the converter circuit (20) comprises a protection device according to the invention (40) and a corresponding method (100).