Circuit arrangements and methods for operating an electrical machine

1. A circuit arrangement comprising:

a first battery;

a second battery;

an electrical machine connected between the first battery and the second battery wherein the electrical machine is connected to the first battery via a first switching arrangement and the electrical machine is connected to the second battery via a second switching arrangement;

a controller configured to control the first switching arrangement and the second switching arrangement such that a current that has a DC component flows through the electrical machine.

2. The circuit arrangement of claim 1 , wherein the first switching arrangement is coupled to the electrical machine via a multi-phase connection and the second switching arrangement is coupled to the electrical machine via a multi-phase connection.

3. The circuit arrangement of claim 1 , wherein the machine is a three-phase machine and the first switching arrangement is coupled to the electrical machine via a three-phase connection and the second switching arrangement is coupled to the electrical machine via a three-phase connection.

4. The circuit arrangement of claim 1 , wherein the electrical machine has three branches, wherein each branch has a first terminal connected to the first battery via the first switching arrangement and a second terminal connected to the second battery via the second switching arrangement.

5. The circuit arrangement of claim 1 , wherein the controller is configured to control the first switching arrangement and the second switching arrangement such that a current that has a DC component flows through at least one of the branches of the electrical machine.

6. The circuit arrangement of claim 1 , wherein the controller is configured to control the first switching arrangement and the second switching arrangement such that a current that has a DC component flows through the electrical machine DC component above a pre-determined threshold.

7. The circuit arrangement of claim 1 , wherein the controller is configured to control the first switching arrangement and the second switching arrangement such that a current that has a DC component flows from the first battery to the second battery via the electrical machine.

8. The circuit arrangement of claim 1 , wherein at least one of the first switching arrangement and the second switching arrangement is an inverter.

9. The circuit arrangement of claim 1 , wherein the controller is configured to control the first switching arrangement and the second switching arrangement such that the first switching arrangement, the electrical machine and the second switching arrangement act as a DCDC converter.

10. The circuit arrangement of claim 1 , wherein a controller is configured to control the first switching arrangement and the second switching arrangement such that the first switching arrangement, the electrical machine and the second switching arrangement act as a step-down converter or a boost converter.

11. The circuit arrangement of claim 1 , wherein the electrical machine is a vehicle motor.

12. The circuit arrangement of claim 1 , wherein the first battery and the second battery are vehicle batteries.

13. The circuit arrangement of claim 1 , wherein the first battery and the second battery have different voltages.

14. The circuit arrangement of claim 1 , wherein the first battery is a 12V car battery and the second battery is a 48V car battery.

15. A method for operating an electrical machine comprising

controlling a first switching arrangement, via which a first battery is coupled with the electrical machine, and a second switching arrangement, via which a second battery is coupled with the electrical machine, such that a current that has a DC component flows through the electrical machine.

16. A circuit arrangement comprising:

a first battery;

a second battery;

an electrical machine connected between the first battery and the second battery wherein the electrical machine is connected to the first battery via a first switching arrangement and the electrical machine is connected to the second battery via a second switching arrangement and wherein the electrical machine is connected to the second switching arrangement via a plurality of terminals; and

a controller configured to control the second switching arrangement, in response to the detection of an error of the second switching arrangement or the second battery, such that the terminals are short-circuited by means of the second switching arrangement.

17. The circuit arrangement of claim 16 , wherein the electrical machine has three branches, wherein each branch is connect to the second switching arrangement by means of one terminal of the plurality of terminals.

18. The circuit arrangement of claim 16 , further comprising a detector configured to detect the error of the second switching arrangement or the second battery.

19. The circuit arrangement of claim 16 , wherein the second switching arrangement comprises a plurality of switches and the error of the switching arrangement is a failure of one of the plurality of switches.

20. A method for operating an electrical machine comprising

controlling a switching arrangement, via which a battery is coupled with the electrical machine via a plurality of terminals, such that the terminals are short-circuited by means of the switching arrangement in response to the detection of an error of the switching arrangement or the battery.

21. A circuit arrangement comprising:

a first battery;

a second battery;

an electrical machine connected between the first battery and the second battery wherein the electrical machine is connected to the first battery via a first switching arrangement and the electrical machine is connected to the second battery via a second switching arrangement;

a controller configured to control the first switching arrangement and the second switching arrangement such that the first battery supplies electric power to drive the electrical machine and the electric machine supplies power to the second battery to charge the second battery.

22. The circuit arrangement of claim 21 , wherein the first switching arrangement and the second switching arrangement are inverters and are controlled based on space vector modulation or field oriented control.

23. A method for operating an electrical machine comprising

controlling a first switching arrangement, via which a first battery is coupled with the electrical machine and a second switching arrangement, via which a second battery is coupled with the electrical machine such that the first battery supplies electric power to drive the electrical machine and the electric machine supplies power to the second battery to charge the second battery.