Circuit arrangement for operating an electrical machine in a motor vehicle with provision of a DC voltage

A method for operating a circuit arrangement (100), which is used for operating an electric machine (101) of a motor vehicle, including a first electric drive phase line (103-1), in which a first battery direct inverter (105-1) is connectable to the electric machine (101) via a first switching device (107-1);

• a second electric drive phase line (103-2), in which a second battery direct inverter (105-2) is connectable to the electric machine (101) via a second switching device (107-2);
• a third electric drive phase line (103-3), in which a third battery direct inverter (105-3) is connected to the electric machine (101), a first inverter terminal (105-3A) of the third battery direct inverter (105-3) is connected to the second drive phase line (103-2) via a third switching device (107-3), and a second inverter terminal (105-3B) of the third battery direct inverter (105-3) is connected to the second drive phase line (103-2) via a fourth switching device (107-4);
• a DC voltage section (109) for providing a DC voltage for a vehicle electrical system, which is connected to the first, second, and third drive phase line (103-1, 103-2, 103-3) via a rectifier (111-1, 111-2, 111-3) in each case;
• and a charging section (113) for supplying a charging current to the first, second, and third battery direct inverter (105-1, 105-2, 105-3), which is connected to the first drive phase line (103-1) and the third drive phase line (103-3), including the steps of:
• setting a positive voltage offset between the two common connecting points (Ps, Pn) of the drive phase lines (103-1, 103-2, 103-3);
• and/or
• setting a constantly positive voltage drop (Us3) across the third battery direct inverter (105-3).