Three-level or multi-level inverter circuit, electric drive system and method
A three-level or multi-level inverter circuit for activation of a multiphase electric machine for an electric drive system, with two supply connections couplable to first and second supply potential of voltage supplies, a load output comprising a load output connection for each phase of the electric machine, a controllable three-level or multi-level inverter between the supply connections and the load output designed to convert a direct voltage received on the supply side into an alternating voltage for driving an electric machine, with an operating mode setting device designed to change the inverter between three-level or multi-level operation and two-level operation in dependence upon overall efficiency of the electric drive system, wherein the overall efficiency is a function of the detected phase current of the electric machine and at least one further parameter and/or property of the electric machine which influence the overall efficiency.
1 . An electric drive system for or in a motor vehicle, the electric drive system comprising:
at least one multiphase electric machine which comprises a synchronous machine with a double rotor, wherein the double rotor is constructed from flux-carrying material consisting of solid material,
a three-level or multi-level inverter circuit, which is coupled to a multiphase electric machine at a load output and which is designed to convert a direct voltage received on a supply side into an alternating voltage, via which the multiphase electric machine can be driven via the load output, wherein the inverter circuit has a controllable three-level or multi-level inverter
wherein the synchronous machine has a stator with an inductor, wherein the inductor is designed to carry a primarily radial magnetic flux, and wherein the inductor of the stator has a radial yoke thickness which is less than 30% of an overall radial inductor thickness.
2 . The drive system of claim 1 ,
wherein the three-level or multi-level inverter circuit is configured for activation of the multiphase electric machine for the electric drive system, the three-level or multi-level inverter circuit further comprising:
two supply connections which can be coupled to a first and a second supply potential of a voltage supply,
a load output which comprises a load output connection for each phase of the multiphase electric machine and which can be coupled to the multiphase electric machine,
a controllable three-level or multi-level inverter disposed between the two supply connections and the load output and designed to convert the direct voltage received on the supply side into the alternating voltage to drive the multiphase electric machine connected to the load output,
an operating mode setting device which is designed to change the inverter from three-level or multi-level operation to two-level operation and vice versa depending on an overall efficiency of the electric drive system, wherein the overall efficiency is a function of a detected phase current of the electric machine as well as at least one further parameter or one further property of the electric machine which influence the overall efficiency.
3 . The drive system of claim 1 ,
wherein the flux-carrying material in the rotor consists of iron or an iron alloy.
4 . The drive system of claim 1 ,
wherein the inductor of the stator has a radial yoke thickness which is less than 20% of an overall radial inductor thickness.
5 . The drive system of claim 1 ,
wherein the inductor of the stator has a radial yoke thickness which is less than 10% of an overall radial inductor thickness.
6 . The drive system of claim 1 ,
wherein the synchronous machine is a three-phase synchronous machine and the inverter circuit is a three-phase inverter.
7 . The drive system of claim 1 ,
wherein the multiphase electric machine is a wheel hub motor for an electrically operable motor vehicle.
8 . A method for operating an electric drive system, which comprises a synchronous machine equipped with a double rotor, wherein the double rotor is constructed from a flux-carrying material consisting of solid material,
wherein the synchronous machine can be operated by means of a 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 overall efficiency is determined from a detected phase current of a synchronous machine as well as at least one further parameter or property of the synchronous machine which influence the overall efficiency,
wherein the synchronous machine has a stator with an inductor, wherein the inductor is designed to carry a primarily radial magnetic flux, and wherein the inductor of the stator has a radial yoke thickness which is less than 30% of an overall radial inductor thickness.