Device and method for controlling an electric machine

A method for controlling an electric machine (1) with the steps of:

• providing (S01) a desired torque value (54) for a torque to be exerted by the electric machine (1);
• determining (S02) a fault signal (51) that indicates a fault state of the electric machine (1);
• determining (S03) a current rotor angle value (56) of the electric machine (1);
• determining (S04) a fault state operating point (62;
• 62′) on the basis of the provided desired torque value (54), the determined fault signal (51) and the determined current rotor angle value (56);
• and
• shifting or moving (S05) an operating point at which the electric machine (1) is operated from a normal state operating point (61) to the determined fault state operating point (62;
• 62′).

The method as claimed in claim 9,

• wherein the normal state operating point (61) is arranged on a first branch (72) of a current ratio function (71) that is separated from a second branch (73) of the current ratio function (71);
• wherein the current ratio function represents a ratio of an electric current, iq, in a q-direction of the electric machine (1) to an electric current, id, in a d-direction of the electric machine (1);
• wherein the q-direction and the d-direction represent coordinate directions that are arranged with a fixed relationship to a rotor of the electric machine (1);
• and
• wherein the fault state operating point (62) is determined on the first branch (72) of the current ratio function (71) and/or on the second branch (73) of the current ratio function (71) depending on the determined fault signal (51) and the determined current rotor angle value (56).