Method for operating an electric motor

A method for operating an electric motor having a stator and a rotor, the method comprising:

• using injection signals up to a useful voltage limit in an entirety of a speed range in which the electric motor is operated to estimate at least one of the rotor position or the speed of the electric motor;
• wherein there is anisotropy, i.e., Ld is not equal to Lq.;
• wherein the useful voltage limit results from the difference between an available intermediate circuit voltage and a voltage amplitude of the superimposed injection signal;
• and
• wherein a combination of the use of injection signals and field weakening is provided to achieve higher speeds above the useful voltage limit.