Electrical drive system and method

Method for operating an electric drive system for or in a motor vehicle,

• having at least one multiphase electric machine which has a double rotor, wherein the double rotor is constructed from flux-carrying material consisting of solid material,
• having a three-level or multi-level inverter circuit for driving the electric machine which has:
• a controllable three-level or multi-level inverter coupled on the output side to the electric machine, said inverter being designed to supply the electric machine with an alternating voltage, and an having an operating mode setting device which is designed to operate the inverter selectively in three-level operation or multi-level operation or in two-level operation in dependence upon at least one parameter influencing the overall efficiency of the electric drive system,
• wherein the synchronous machine can be operated by means of the controllable three-level or multi-level inverter in dependence upon an overall efficiency of the electric drive system both in a three-level or multi-level operating mode and also in a two-level operating mode wherein the method comprises determining, by an evaluation device of the operating mode setting device, as a function of at least a detected phase current of the electric machine and optionally at least one further property of the electric drive system influencing the overall efficiency, the overall efficiency of the electric drive system including inverter losses and electric-machine losses attributable to harmonic components of a magnetic flux density in the double rotor, and controlling the inverter to operate in the three-level or multi-level operating mode or in the two-level operating mode based on the determined overall efficiency.