Method for charging a traction battery using a three phase source
The present method relates to a method of charging a traction battery of a vehicle from an external AC power supply system. The traction battery is coupled, via an inverter, to an electric alternating-field machine such that the AC power supply can be connected to the phase windings of the alternating-field machine. The method includes a step of synchronizing the rotational speed of the alternating-field machine with the frequency of the AC power supply. Then the AC power supply is connected to the phase windings of the alternating-field machine and the inverter, which is electrically coupled to the alternating-field machine, is operated as a step-up converter.
1. A method of charging a traction battery ( 2 ) of a motor vehicle from an external AC power supply system, in which the traction battery ( 2 ) to be charged is coupled, via an inverter ( 3 ), to an electric alternating-field machine ( 4 ) such that the AC power supply is connectable to phase windings (L 1 , L 2 , L 3 ) of the alternating-field machine ( 4 ), the method comprising the steps of:
controlling a rotational speed of the alternating-field machine by adjusting, with the inverter, power from the traction battery to the alternating-field machine;
synchronizing the rotational speed of the alternating-field machine ( 4 ) with a frequency of the AC power supply;
connecting the AC power supply to the phase windings (L 1 , L 2 , L 3 ) of the alternating-field machine ( 4 ); and
operating the inverter ( 3 ), that is electrically coupled to the alternating-field machine ( 4 ), as a step-up converter.
2. The method according to claim 1 , further comprising the step of using the inverter ( 3 ) to either drive or feed the alternating-field machine ( 4 ) by the traction battery ( 2 ) for synchronizing the rotational speed of the alternating-field machine.
3. The method according claim 1 , further comprising the step of operating the inverter ( 3 ) as a step-up converter in a direction toward the traction battery ( 2 ).
4. The method according to claim 1 , further comprising the step of separating the alternating-field machine ( 4 ) from a drive-train of the motor vehicle, via a separator clutch, before synchronizing the rotational speed of the alternating-field machine.
5. The method according to claim 1 , further comprising the step of, after synchronizing the rotational speed of the alternating-field machine, operating the alternating-field machine ( 4 ) in an idling mode.
6. The method according to claim 1 , further comprising the step of designing the alternating-field machine ( 4 ) as an asynchronous machine with the phase windings (L 1 L 2 , L 3 ) in a delta connection.
7. The method according to claim 1 , further comprising the step of connecting the AC power supply to the phase windings (L 1 , L 2 , L 3 ), at a synchronous point, by at least one of a synchronizing device ( 7 ) and a connecting device ( 6 ).
8. The method according to claim 1 , further comprising the step of feeding the inverter ( 3 ) with a voltage, via a winding tap ( 4 d , 4 e , 4 f ) on the phase winding (L 1 , L 2 , L 3 ), from the alternating-field machine ( 4 ) which, at least at times, is lower in comparison with a voltage of the AC power supply.
9. The method according to claim 8 , further comprising the step of maintaining a peak value of the reduced voltage lower than a battery voltage of the traction battery ( 2 ).
10. A device for charging a traction battery ( 2 ) of a motor vehicle, the device comprising:
an external AC power supply,
the traction battery ( 2 ) to be charged being coupled, via an inverter ( 3 ), to an electric alternating-field machine ( 4 ) such that the AC power supply is connectable to phase windings (L 1 , L 2 , L 3 ) of the alternating-field machine ( 4 ),
a rotational speed of the alternating-field machine ( 4 ) being controlled by adjusting, with the inverter, power from the traction battery to the alternating-field machine so as to synchronize the rotational speed of the alternating-field machine with a frequency of the AC power supply,
the AC power supply being connected to the phase windings (L 1 , L 2 , L 3 ) of the alternating-field machine ( 4 ), and
the inverter ( 3 ) being electrically coupled to the alternating-field machine ( 4 ) and being operated as a step-up converter.
11. A method of charging a traction battery of a motor vehicle with power from an external AC power supply, the method comprising the steps of:
coupling the traction battery, via an inverter, to an electric alternating-field machine and selectively coupling the AC power supply to phase windings of the alternating-field machine;
determining and comparing, with a synchronization device, a rotational speed of the alternating-field machine and a frequency of the power from the AC power supply;
controlling the rotational speed of the alternating-field machine by adjusting, with the inverter, power from the traction battery to the alternating-field machine so as to synchronize the rotational speed of the alternating-field machine and the frequency of the power from the AC power supply;
coupling the AC power supply to the phase windings of the alternating-field machine; and
operating the inverter as a step up converter for directing at least one of the power from the AC power supply and the power from the alternating-field machine to the traction battery.