Method for operating a separately excited electric machine in a motor vehicle
A method for operating a separately excited electric machine, in particular, a generator of a motor vehicle, where an exciting current flows through a rotor winding of the electric machine at a nominal current intensity during a normal operation and at a holding current intensity in an idling operation; the holding current intensity being greater than zero and less than the nominal current intensity.
1. A method for operating a separately excited electric machine, which is a generator of a motor vehicle, the method comprising:
providing an exciting current which flows through a rotor winding of the electric machine at a nominal current intensity during a normal operation and at a holding current intensity during an idling operation, in which neither a regenerative, nor a motive operation is called for;
wherein the holding current intensity is greater than zero and less than the nominal current intensity.
2. The method of claim 1 , wherein the holding current intensity is at most 50% of the nominal current intensity.
3. The method of claim 1 , wherein the holding current intensity is selected so that a voltage induced by the electric machine in the idling operation is less than the vehicle battery voltage at the end of charging.
4. The method of claim 1 , wherein the exciting current at the nominal current intensity is provided by applying a pulse-width modulated voltage signal having a first pulse duty factor and a voltage value to the rotor winding of the machine, and wherein the exciting current at the holding current intensity is provided by applying a pulse-width modulated voltage signal having a second pulse duty factor and the voltage value.
5. The method of claim 4 , wherein the voltage value is greater than 24 V and less than 60 V.
6. The method of claim 4 , wherein the first pulse duty factor is 100%, less than 100%, less than 90%, less than 70%, less than 50% or less than 40%.
7. The method of claim 4 , wherein the second pulse duty factor is less than 90%, less than 70%, less than 50%, less than 40%, less than 20% or less than 10%.
8. The method of claim 4 , wherein during a starting phase of the electric machine, a pulse-width modulated voltage signal having the voltage value and a third pulse duty factor is applied to the rotor winding, and wherein the third pulse duty factor is greater than the first pulse duty factor.
9. The method of claim 8 , wherein on the basis of closed-loop control, the voltage signal having the third pulse duty factor is applied to the rotor winding until the exciting current flowing through the rotor winding has the nominal current intensity.
10. The method of claim 9 , wherein the voltage signal having the third pulse duty factor is applied to the rotor winding for a predefined period of time.
11. The method of claim 8 , wherein during the starting phase, the pulse duty factor is reduced in steps from the third pulse duty factor to the first pulse duty factor.
12. The method of claim 4 , wherein the exciting current flowing through the rotor winding is adjusted to the holding current based on a measurement of the exciting current and by controlling the second pulse duty factor.
13. The method of claim 4 , wherein the exciting current flowing through the rotor winding is adjusted to a setpoint holding current intensity by providing a fixed, second pulse duty factor.
14. The method of claim 4 , wherein the voltage value is greater than 24 V and less than 48 V.
15. The method of claim 4 , wherein during a starting phase of the electric machine, a pulse-width modulated voltage signal having the voltage value and a third pulse duty factor is applied to the rotor winding, and wherein the third pulse duty factor is greater than the first pulse duty factor; and the third pulse duty factor is 100%.
16. The method of claim 1 , wherein the holding current intensity is selected so that a voltage induced by the electric machine in the idling operation is less than the vehicle battery voltage at the end of charging, and not more than 95% of the voltage at the end of charging.
17. A processing unit, comprising:
a processor arrangement for operating a separately excited electric machine, which is a generator of a motor vehicle, by performing the following:
providing an exciting current which flows through a rotor winding of the electric machine at a nominal current intensity during a normal operation and at a holding current intensity during an idling operation, in which neither a regenerative, nor a motive operation is called for;
wherein the holding current intensity is greater than zero and less than the nominal current intensity.
18. A computer readable medium having a computer program, which is executable by a processor, comprising:
a program code arrangement having program code operating a separately excited electric machine, which is a generator of a motor vehicle, by performing the following:
providing an exciting current which flows through a rotor winding of the electric machine at a nominal current intensity during a normal operation and at a holding current intensity during an idling operation, in which neither a regenerative, nor a motive operation is called for;
wherein the holding current intensity is greater than zero and less than the nominal current intensity.