Externally excited synchronous machine and traction network

Abstract

The invention relates to a separately excited synchronous machine (3) with a control circuit, wherein the control circuit comprises a first circuit (6) for generating the stator currents and a second circuit (8) for generating a rotor current, wherein the second circuit (8) is connected to a rotor winding of the separately excited synchronous machine (3) via lines (9), wherein at least one EMC filter (11) is arranged between the second circuit (8) and the rotor winding, the filter having at least one core (12) made of a magnetic material, wherein a rotor of the separately excited synchronous machine (3) is connected to ground by means of a ground connection (14), wherein the ground connection (14) is led from the rotor through the at least one core (12), and a traction network (1).

Description

The invention relates to a separately excited synchronous machine and a traction network for an electric or hybrid vehicle having a separately excited synchronous machine.In most drives for electric or hybrid vehicles, the alternating current for an electric machine is generated by means of a pulse inverter. Pulse inverters generate a disturbance voltage on their output side in the direction of the electric machine, on the basis of the principle. This interference voltage is transmitted via a parasitic capacitive coupling to the rotor, where this causes two problems in particular. On the one hand, the interference voltage on the rotor shaft can lead to bearing currents in the bearings of the rotor shaft to ground, which can damage the surface structure of the bearings. On the other hand, the interference voltage on the rotor shaft can be output via the gear to flange shafts which are located outside the shielding region of the drive and thus emit the interference voltage, which can lead to EMC problems. Therefore, in most applications, the rotor shaft is connected to ground (milled off), so that the interference voltage is reduced. In externally excited synchronous machines, the interference voltage on the rotor shaft is increased on account of the external excitation. The external excitation is galvanically coupled to the rotor winding and from there is capacitively coupled to the rotor shaft. It is further known to provide EMC filters in order to reduce the interference radiation. In this case, an EMC filter can be assigned to the phase lines of the electric machine and a further EMC filter can be assigned to the lines for the external excitation or the rotor current. These EMC filters typically have a core made of a magnetic material, wherein the lines through the core are simply passed through or wound in opposite directions around the core (common mode choke). The magnetic material can be a soft or hard magnetic core. The magnetic material can be sintered or made of nanocrystalline material. Ferrite rings are frequently used. A problem with externally excited synchronous machines is that the current in the core is increased due to the dimensioning, so that the cores must be dimensioned correspondingly larger, which leads to cost and installation space disadvantages.The invention is based on the technical problem of creating a separately excited synchronous machine in which the requirements for an EMC filter are reduced. A further technical problem is the provision of a corresponding traction network for an electric or hybrid vehicle.The solution of the technical problem results from a separately excited synchronous machine having the features of claim 1 and a traction network having the features of claim 8.The externally excited synchronous machine has a drive circuit which has a first circuit for generating the stator currents and a second circuit for generating a rotor current. The first circuit is, for example, a pulse inverter. The second circuit is connected to a rotor winding of the externally excited synchronous machine via lines. In this case, a plurality of rotor windings can also be present. At least one EMC filter is arranged between the second circuit and the rotor winding, said filter having at least one core made of a magnetic material. Furthermore, a rotor of the externally excited synchronous machine is connected to ground by means of a ground connection, wherein the ground connection is guided from the rotor through the at least one core. The advantage is that the common-mode currents in the core thereby compensate one another, so that the core can be dimensioned smaller.In one embodiment, the leads and ground connection are connected to the rotor via slip rings. The slip rings can be arranged close to one another so that the lines and the ground connection can be guided from the EMC filter as cable bundles to the slip rings.In a further embodiment, the lines for the rotor winding have a shielding, wherein the ground connection is formed in sections by the shielding.In one embodiment, the shielding is guided through the core, so that the connection between shielding and ground can be very short.In an alternative embodiment, the lines between the second circuit and the at least one core do not have any shielding, which simplifies the passage through the core.In a further embodiment, the EMC filter is arranged in a housing which is connected to ground, wherein the ground connection is connected to the ground connection of the housing.In a further embodiment, the lines and the ground connection are only carried out by the at least one core. In embodiments where the lines are wound in opposite directions around the core (common mode choke), the ground connection is preferably also wound around the core, which is not obligatory, however.The traction network has at least one externally excited synchronous machine, as has been described above.The invention is explained in more detail below with reference to preferred exemplary embodiments. The figures show: FIG. 1 shows a schematic block diagram of a traction network of an electric or hybrid vehicle in a first embodiment, and FIG. 2 shows a schematic partial illustration of a traction network in a second embodiment.FIG. 1 schematically shows a traction network 1 of an electric or hybrid vehicle. The traction network 1 has a high-voltage battery 2. Furthermore, the traction network 1 has a separately excited synchronous machine 3 which has a stator 4 with stator windings and a rotor with a rotor shaft 5. A first circuit 6, which is designed as a pulse inverter 7, generates stator currents for the stator windings. A second circuit 8 generates a rotor current. The second circuit 8 is connected via lines 9 to slip rings 10, via which the rotor windings, not shown, receive the rotor current. An EMC filter 11 is arranged between the second circuit 8 and the slip rings 10, said filter having at least one core 12 made of a magnetic material. The EMC filter 11 can additionally have Y and / or X capacitors. The first circuit 6, the second circuit 8 and the EMC filter 11 are arranged in a housing 13 which is connected to ground. It should be noted here that the common housing 13 is not obligatory and the EMC filter 11 can also have its own housing or is arranged in a housing only with the second circuit 8.Furthermore, the externally excited synchronous machine 3 has a ground connection 14, which is connected to a slip ring 10 on the rotor shaft 5 and is guided through the core 12. In the housing 13, the ground connection 14 is then connected to the ground of the housing 13. In this case, the current direction of common mode interference signals (common mode currents) which are generated by the second circuit 8, for example, is drawn in in the lines 9 by means of arrows. These disturbances transmitted to the rotor shaft 5 are now dissipated through the ground connection 14, wherein the current direction in the ground connection 14 is also shown by means of an arrow. The interference current in the lines 9 and the ground connection 14 is the same, wherein the direction is reversed, so that the resulting currents in the core 12 are compensated.FIG. 2 shows an alternative embodiment in which the lines 9 are formed in sections with a shielding 15, which is then used in sections for the ground connection 14. For connection to the slip ring 10, a line 16 is then connected to the shielding 15. On the other hand, a line 17 is then connected to the shielding 15 which is then passed through the core 12 and then connected to ground. The ground connection 14 is thus formed by the line 16, the shield 15 and the line 17.List of reference characters1 Traction network 2 High-voltage battery 3 Synchronous machine 4 Stator 5 Rotor shaft 6 First circuit 7 Pulse change switch 8 Second circuit 9 Lines 10 Slip rings 11 EMC filter 12 Core 13 Housing 14 Ground connection 15 Shield 16 Line 17 Line

Claims

Externally excited synchronous machine (3) having a drive circuit, wherein the drive circuit has a first circuit (6) for generating the stator currents and a second circuit (8) for generating a rotor current, wherein the second circuit (8) is connected to a rotor winding of the externally excited synchronous machine (3) via lines (9), wherein at least one EMC filter (11) is arranged between the second circuit (8) and the rotor winding, said EMC filter having at least one core (12) made of a magnetic material, wherein a rotor of the externally excited synchronous machine (3) is connected to ground by means of a ground connection (14), characterized in that the ground connection (14) is led from the rotor through the at least one core (12).Externally excited synchronous machine according to Claim 1, characterized in that the lines (9) and the ground connection (14) are connected to the rotor via slip rings (10).Externally excited synchronous machine according to Claim 1 or 2, characterized in that the lines (9) for the rotor winding have a shielding (15), wherein the ground connection (14) is formed in sections by the shielding.Externally excited synchronous machine according to Claim 3, characterized in that the shielding (15) is guided through the core (12).Externally excited synchronous machine according to Claim 3, characterized in that the lines (9) do not have any shielding (15) between the second circuit (8) and the at least one core (12).Externally excited synchronous machine according to one of the preceding claims, characterized in that the EMC filter (11) is arranged in a housing (13) which is connected to ground, the ground connection (14) being connected to the ground connection of the housing (13).Externally excited synchronous machine according to one of the preceding claims, characterized in that the lines (9) and the earth connection (14) are made only by the at least one core (12).Traction network (1) of an electric or hybrid vehicle, characterized in that the traction network (1) has a separately excited synchronous machine (3) according to one of Claims 1 to 7.

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