Demagnetization of the rotor of an externally excited synchronous machine

Abstract

The present disclosure relates to a circuit device for demagnetizing the rotor of an externally excited synchronous machine and to a method for operating the circuit device.

Claims

1. A circuit device for demagnetizing a rotor of an externally excited synchronous machine, comprising at least one circuit connected to poles of a rotor winding of the externally excited synchronous machine and having a diode, a capacitor connected downstream of the diode, and a first switch, wherein the rotor winding, the diode, the capacitor, and the first switch are electrically connected in series, and wherein, when the first switch is closed, a current of the rotor winding flows through the diode into the capacitor.

2. The circuit device according to claim 1, further comprising a first resistor is connected in parallel with the capacitor.

3. The circuit device according to claim 1, wherein a positive electrode of the capacitor is connected via a second switch to a positive pole of the rotor winding, and a negative electrode of the capacitor is connected via a third switch to a negative pole of the rotor winding.

4. The circuit device according to claim 1, wherein a positive electrode of the capacitor is connected via a second switch to a positive electrode of an intermediate circuit capacitor of the externally excited synchronous machine, and a negative electrode of the capacitor is connected via a second resistor and a third switch to a negative electrode of an intermediate circuit capacitor of the externally excited synchronous machine.

5. The circuit device according to claim 1, wherein a positive electrode of the capacitor is connected via a second resistor and a second switch to a positive electrode of an intermediate circuit capacitor of the externally excited synchronous machine, and a negative electrode of the capacitor is connected via a third switch to a negative electrode of an intermediate circuit capacitor of the externally excited synchronous machine.

6. The circuit device according to claim 1, further comprising a storage inductor is connected in parallel to the capacitor.

7. The circuit device according to claim 6, wherein poles of the storage inductor are connected via a second switch and a third switch to electrodes of the capacitor, and via a fourth switch and a fifth switch to electrodes of an intermediate circuit capacitor of the externally excited synchronous machine.

8. A method for demagnetization of a rotor of an externally excited synchronous machine, the method comprising: providing at least one switching device having a diode, a capacitor connected downstream of the diode, and a first switch, wherein the at least one switching device is electrically conductively connected to poles of at least one rotor winding of the externally excited synchronous machine, wherein the at least one rotor winding, the diode, the capacitor, and the first switch are electrically connected in series, and wherein, when the first switch is closed, a current of the at least one rotor winding flows through the diode into the capacitor; and transferring electromagnetic energy stored in the rotor winding into the capacitor of the at least one switching device.

9. The method according to claim 8, further comprising: transferring electrical energy stored in the capacitor of the circuit device at least in part into an intermediate circuit capacitor of the externally excited synchronous machine.

10. The method according to claim 8, further comprising: transferring electrical energy stored in the capacitor of the circuit device at least in part into a storage inductor.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) The disclosure is illustrated schematically in the drawings by means of embodiments and will be described in more detail with reference to the drawings. The following is shown:

(2) FIG. 1 a circuit diagram of an EESM according to the prior art.

(3) FIG. 2 a circuit diagram of an EESM with a first embodiment of a circuit device.

(4) FIG. 3 a circuit diagram of an EESM with a second embodiment of a circuit device.

(5) FIG. 4 a circuit diagram of an EESM with a third embodiment of a circuit device.

(6) FIG. 5 a circuit diagram of an EESM with a fourth embodiment of a circuit device.

DETAILED DESCRIPTION

(7) FIG. 2 shows a circuit diagram of an EESM with a first embodiment of a circuit device according to principles of the present disclosure. A circuit is connected to the poles of the rotor winding W.sub.R, which has a diode D.sub.3, a snubber capacitor C.sub.S connected downstream of the diode, and a switch S.sub.9. A discharge resistor R.sub.E, via which the energy of the capacitor C.sub.S can be dissipated, is connected in parallel to the capacitor C.sub.S.

(8) To demagnetize the rotor, the switches S.sub.7 and S.sub.8 are opened and the switch S.sub.9 is closed. The current of the rotor then flows through the diode D.sub.3 into the capacitor C.sub.S. This charges it. The further the capacitor C.sub.S charges, the faster the magnetic energy of the rotor is dissipated. When the magnetic energy of the rotor has gone to zero, the current flow will also have gone to zero. The diode D.sub.3 now prevents the capacitor C.sub.S from carrying energy back into the rotor, since it prevents a current backflow. The discharge resistor R.sub.E is used for its ability to dissipate the energy of the snubber capacitor C.sub.S.

(9) FIG. 3 shows a circuit diagram of an EESM with a second embodiment of a circuit device according to the principles of the present disclosure, which has no discharge resistor R.sub.E. Instead, the positive electrode of the capacitor C.sub.S is connected via a second switch S.sub.10 to the positive pole of the rotor winding W.sub.R, and the negative electrode of the capacitor C.sub.S is connected via a third switch S.sub.11 to the negative pole of the rotor winding W.sub.R.

(10) If the rotor has now been demagnetized by means of switch S.sub.9 and diode D.sub.3 and the capacitor C.sub.S has been charged, in order to discharge the capacitor C.sub.S instead of the discharge resistor R.sub.U shown in FIG. 2, or also in combination with the resistor R.sub.E the switches S.sub.10 and S.sub.11 can be used. By closing the switches S.sub.10 and S.sub.11 the energy of the capacitor C.sub.S can be converted back into magnetic energy in the rotor as soon as driving operation of the vehicle is to be resumed. When the capacitor C.sub.S is discharged to 0V, the switches S.sub.10 and S.sub.11 are opened again.

(11) FIG. 4 shows a circuit diagram of an EESM with a third embodiment of a circuit device according to principles of the present disclosure, in which the positive electrode of the capacitor C.sub.S is connected via a switch S.sub.12 to the positive electrode of the intermediate circuit capacitor C, and the negative electrode of the capacitor C.sub.S is connected via a resistor R and a switch S.sub.13 to the negative electrode of the intermediate circuit capacitor C.

(12) If the magnetic energy of the rotor is stored in the capacitor C.sub.S, the capacitor C.sub.S and the intermediate circuit capacitor C can be parallelized via the switches S.sub.12 and S.sub.13. This then ensures that the energy stored in the snubber capacitor C.sub.S can at least in part flow into the intermediate circuit capacitor C. A resistor R in series with S.sub.13 here ensures a limitation of the charge-reversal current.

(13) It should be noted here that this embodiment only allows the voltages of the capacitor C.sub.S and of the intermediate circuit capacitor C to be matched. Complete transfer of the electrostatic energy from C.sub.S into C is not possible in this way. To achieve this, the embodiment shown in FIG. 5 is suitable.

(14) FIG. 5 shows a circuit diagram of an EESM with a fourth embodiment of a circuit device according to principles of the present disclosure in which a storage inductor L.sub.S is connected in parallel with the capacitor C.sub.S. The poles of the storage inductor L.sub.S are connected via switches S.sub.14 and S.sub.15 to the electrodes of the capacitor C.sub.S and via switches S.sub.16 and S.sub.17 to the electrodes of the intermediate circuit capacitor C.

(15) If capacitor C.sub.S is charged by means of switch S.sub.9 and diode D.sub.3, as already described, and the rotor is fieldless, the switch S.sub.9 is opened. The storage inductor L.sub.S can be charged by closing the two switches S.sub.14 and S.sub.15. The switch S.sub.15 is then opened, and the switches S.sub.16 and S.sub.17 are closed. The current stored in the inductor L.sub.S then flows through the capacitor C and charges it. This procedure can be repeated until the charge of the capacitor C.sub.S is dissipated and transferred into the capacitor C.

(16) In one variant of the method, the switches S.sub.14 and S.sub.15 are closed until the capacitor C.sub.S is completely discharged. The switch S.sub.15 is then opened and the switches S.sub.16 and S.sub.17 are closed until the current flow through the inductor L.sub.S is zero. The switches S.sub.16 and S.sub.17 are then opened again and the process is completed. In this way, the number of switching operations is minimized and losses in the switches are as low as possible. However, the maximum energy which has to be stored in the inductor L.sub.S is in this case high.

(17) In an alternative variant of the method, the switches S.sub.15, S.sub.16 and S.sub.17 are switched several times at a higher frequency, and the described procedure is carried out multiple times. The inductor L.sub.S can thereby be dimensioned significantly smaller.

(18) This application claims priority to German patent application no. 10 2019 124 212.6, filed Sep. 10, 2019, which is hereby incorporated herein by reference in its entirety.

(19) Aspects and features of the various embodiments described above can be combined to provide further embodiments. These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled.