Rotor, electric machine and traction drive

Abstract

The invention relates to a rotor (10) for constructing an efficient and flexibly deployable electric machine. The rotor (10) comprises a standard pole pair (11), wherein the standard pole pair (11) comprises a permanent magnet (14) and a first electromagnet (16), and a switchable pole pair (12), wherein the switchable pole pair (12) comprises a second electromagnet (18), the rotor (10) being configured to switch the second electromagnet (18) on or off in addition to the first electromagnet (16). The invention further relates to an electric machine and a traction drive.

Description

[0001] The invention relates to a rotor for an electric machine. State of the art

[0002] CN 113507176 A discloses an electric motor with a rotor having DC windings and permanent magnets, wherein in one embodiment DC windings are provided at all poles and permanent magnets are arranged circumferentially at every second pole.

[0003] From CN 105846571 A a rotor of a generator is known which has rotor windings and permanent magnets, wherein a rotor winding is arranged at each pole and permanent magnets are arranged circumferentially at every second pole.

[0004] From WO 2010063882 A1, a rotor of an electric motor or a generator is known which has rotor windings and permanent magnets, wherein first poles are provided which have exclusively a rotor winding, and second poles are provided which have a rotor winding and a permanent magnet.

[0005] From CN 204538925 U a hybrid excited rotor is known which has poles with permanent magnets and poles with rotor windings, with a damping winding additionally provided at all poles.

[0006] EP 0741444 A1 also describes a hybrid excited rotor of an electric motor, which has poles with permanent magnets and a rotor winding and poles with only rotor windings, wherein all rotor windings are connected in series.

[0007] From US 2013328519 A1 a rotor of an electrical machine is known, wherein rotor windings are switchable. Disclosure of the invention

[0008] Synchronous machines with a permanent magnet-excited rotor are known. In these machines, the rotor field is generated via permanent magnets.

[0009] To enable a high maximum machine speed, the rotor field should be weakened at higher speeds to prevent exceeding a maximum system voltage caused by increasing speeds and the resulting induced voltages. Such field weakening can be achieved with a stator current that deliberately generates a field opposite to the magnetization direction of the permanent magnets. However, this portion of the field-weakening current can no longer be used for torque generation, resulting in efficiency losses in this field-weakening range.

[0010] To overcome these disadvantages, hybrid-excited rotors with a single pole pair are used. These rotors have, in addition to permanent magnets, an electromagnet with a winding. A direct current flows through this winding. The rotor field can be precisely controlled via an excitation current in this winding. Therefore, in the field-weakening range, no current component needs to be used for field weakening. Instead, it is sufficient to reduce the excitation current to weaken the rotor field.

[0011] Such a hybrid-excited synchronous machine can only be operated more efficiently in the field-weakening range by adjusting the rotor flux. A machine that can be flexibly adapted across different operating ranges would be desirable.

[0012] The object of the present invention is therefore to offer devices for an electric machine that are particularly flexible and adaptable to different operating ranges while still offering high efficiency. Furthermore, particularly advantageous application areas for these devices or for electric machines equipped with these devices are to be offered.

[0013] The problem is solved first by a rotor for an electric machine comprising a standard pole, wherein the standard pole pair comprises a permanent magnet and a first electromagnet, and a switchable pole pair, wherein the switchable pole pair comprises a second electromagnet, wherein the rotor is configured to switch the second electromagnet on or off in addition to the first electromagnet.

[0014] The rotor thus has at least one standard pole pair, as can be used in a hybrid-excited rotor as described above. This standard pole pair makes it possible to operate an electric machine equipped with the rotor particularly efficiently, especially in a field-weakening region.

[0015] In addition, the rotor has at least one further pole pair, in particular in the form of the switchable pole pair. The switchable pole pair has a second electromagnet. This second electromagnet can be switched on or off. Thus, the switchable pole pair can be switched on or off, for example, depending on the operating range.

[0016] The electric machine can therefore be adapted to such operating areas etc. and thus operated in a particularly flexible manner.

[0017] The rotor has at least one standard pole pair and one switchable pole pair. The rotor therefore has at least four poles. Such a rotor can thus function as a two-pole rotor when the switchable pole pair is deactivated, and as a four-pole rotor when the switchable pole pair is activated. Corresponding rotors with a higher number of poles, particularly with higher pole pairs, are conceivable.

[0018] The second electromagnets each have windings. These windings can be connected in series. This ensures that the poles of the switchable pole pair are operated synchronously, for example. Furthermore, the series connection simplifies the overall circuit topology compared to individually controlled second electromagnets.

[0019] It is conceivable that the windings of the second electromagnet have more turns than the windings of the first electromagnet. The electromagnets of the standard pole pair can therefore have fewer turns than the electromagnets of the switchable pole pair. In this way, asymmetries in the rotor flux due to the permanent magnets can be compensated for. Overall, a largely symmetrical rotor field can be achieved with an increased number of pole pairs compared to a rotor with a single pole pair, in particular with at least two pole pairs.

[0020] Alternatively or additionally, for control purposes, for example to correct asymmetries, it is also conceivable to allow different current intensities to flow in the windings of the switchable pole pair than in the windings of the standard pole pair. This can be achieved, for example, via different slip ring systems for supplying the pole pairs.

[0021] To keep the windings simple from a manufacturing perspective, the rotor can be designed as a salient pole rotor.

[0022] Rotors for particularly powerful electric machines can be designed as solid pole rotors.

[0023] The invention also encompasses an electric machine with a rotor of the type described above.

[0024] The electrical machine can be designed as a motor, in particular as an electric motor. Alternatively or additionally, the electrical machine can also be designed as a generator or at least be operable as a generator.

[0025] The additional setting options, in particular the ability to activate or deactivate the switchable pole pair, allow the electric machine to be used in a particularly flexible manner, for example optimized for different operating conditions, operating ranges, etc.

[0026] In particular, it is conceivable that the electric machine is configured to operate in at least two different modes. Each mode can be characterized by a specific selection of standard pole pairs used and / or switchable pole pairs. One mode, for example, can relate to an operating range with low speeds and / or low torques. Another mode can relate to an operating range outside the aforementioned range. For example, this operating range can involve higher speeds and / or higher torques. One mode, for example, can be designed for operating the electric machine in a field-weakening region.

[0027] It is conceivable that the electric machine is set up to automatically activate or deactivate at least one of these modes.

[0028] For example, it is conceivable that the electric machine is set up to select one of the modes depending on an operating range, for example depending on a torque and / or a speed of the electric machine, in particular to activate or deactivate it.

[0029] Such an electric machine with the rotor described above can be particularly advantageously used in a traction drive. Such a traction drive can be highly adaptable and yet operated with high efficiency. Therefore, a traction drive with an electric machine of the type described above also falls within the scope of the invention.

[0030] Due to the additional adjustment options of the electric motor, the traction drive can be used across a particularly wide range of operating conditions, operating ranges, etc. This is especially advantageous for battery-electric vehicles, which should be driven as efficiently as possible at both lower speeds, particularly when starting from a standstill, and at high speeds, such as when driving on a highway.

[0031] Further features and advantages of the invention will become apparent from the following detailed description of an embodiment of the invention with reference to the figures of the drawing, which show details essential to the invention, as well as from the claims.

[0032] The individual features can be implemented individually or in any combination in various versions of the invention. The schematic drawing illustrates exemplary embodiments of the invention, which are explained in more detail in the following description. Brief description of the drawings

[0033] They show: Fig. 1 a schematic representation of a rotor and Fig. 2 a circuit topology of the rotor according to Fig. 1. Embodiments of the invention

[0034] Fig. Figure 1 shows a rotor 10 for an electric machine, for example, an electric motor. The rotor 10 comprises a standard pole pair 11 with a total of two poles. The poles of the standard pole pair 11 are located on opposite sides. Each pole has a permanent magnet 14 and a first electromagnet 16.

[0035] Furthermore, the rotor 10 has a switchable pole pair 12 with a total of two poles. The two poles of the switchable pole pair 12 each comprise a second electromagnet 18, but these are not permanent magnets.

[0036] The windings and magnets are arranged in the rotor lamination 13 at each of the poles of the standard pole pair 11 and at each of the poles of the switchable pole pair 12.

[0037] The first electromagnets 16 and the second electromagnets 18 each exhibit, in Fig. 1 symbolically represented windings. The windings of the second electromagnet have 18 more turns than the windings of the first electromagnet have 16.

[0038] Overall, the rotor 10 is designed as a salient pole rotor.

[0039] The rotor 10 can, for example, be used as the rotor of an electric motor for a traction drive of a battery-electric vehicle, such as a passenger car.

[0040] Fig.Figure 2 shows a circuit topology 20 to explain the connection of the windings of the first electromagnets 16 and the second electromagnets 18.

[0041] It can be seen that the first electromagnets 16 of the standard pole pair 11, in particular their windings, are connected in series. They are directly connected to terminals 22. The rotor 10 is supplied with electrical energy via the terminals 22, for example via slip rings.

[0042] The second electromagnets 18, in particular their windings, are connected in series to each other, but in parallel to the windings of the first electromagnets 16, via two power semiconductors 24.

[0043] It would also be conceivable to connect the electromagnets 16 or 18 in parallel to each other within each type of pole pair 11 or 12, instead of connecting the windings of the first electromagnets 16 of the standard pole pair 11 and / or the windings of the second electromagnets 18 of the switchable pole pair 12 in series.

[0044] The circuit topology 20 provides in particular that the windings of the second electromagnets 18 of the switchable pole pair 12 can be connected to or disconnected from the terminals 22 independently of the windings of the first electromagnets 16 of the standard pole pair 11.

[0045] For this purpose, the power semiconductors 24 are designed as controllable switches. They can, for example, be based on SiC MOSFETs.

[0046] A control circuit 26, which may, for example, include a microcontroller with a processor and memory, as well as executable program code stored in memory, is configured to control the power semiconductors 24. In particular, the control circuit 26 can provide two different modes. In a first mode, the control circuit 26 switches both power semiconductors 24 on, so that the switchable pole pair 12, in particular its second electromagnet 18, is energized and thus active. In this mode, the rotor 10 therefore functions as a 4-pole rotor.

[0047] In a second mode, the control circuit 26 blocks both power semiconductors 24. In this second mode, the switchable pole pair 12 is therefore deactivated. In this mode, the rotor 10 essentially functions as a 2-pole rotor.

[0048] The control circuit 26 can be configured to automatically activate the first or second mode and deactivate the other mode. For this purpose, the control circuit 26 can be connected to signal transmitters that supply it with signals relating to torque and / or rotational speed, in particular from an electric machine with which the rotor 10 is used. The first and / or second mode is then activated or deactivated depending on the torque and / or rotational speed.

[0049] In this embodiment, the control circuit 26 is part of the rotor 10. In general, it is conceivable that the control circuit is generally part of an electrical machine with which the rotor 10 is used, in particular regardless of whether it is rigidly connected to the rotor 10 or not.

[0050] If the electric machine is controlled by a machine control system, for example, the control circuit 26 can be implemented as part of the machine control system. If the electric machine is used as part of a traction drive, the machine control system and / or the control circuit 26 in particular can, in turn, be implemented as part of a traction drive control system. Reference symbol list 10 Rotor 11 standard pole pair 12 switchable pole pairs 13 Rotor plate 14 permanent magnet 16 first electromagnet 18 second electromagnet 20 Circuit topology 22 connection 24 Power semiconductors 26 Control circuit QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] CN 113507176 A

[0002] CN 105846571 A

[0003] WO 2010063882 A1

[0004] CN 204538925 U

[0005] EP 0741444 A1

[0006] US 2013328519 A1

[0007]

Claims

[1] Rotor (10) for an electric machine, comprising - a standard pole pair (11) wherein the standard pole pair (11) comprises a permanent magnet (14) and a first electromagnet (16), - a switchable pole pair (12), wherein the switchable pole pair (12) comprises a second electromagnet (18), wherein the rotor (10) is configured to switch the second electromagnet (18) on or off in addition to the first electromagnet (16). [2] Rotor (10) according to the preceding claim, characterized by , that a winding of the second electromagnet (18) has more turns than a winding of the first electromagnet (16). [3] Rotor (10) according to any of the preceding claims, characterized by , that the rotor (10) is configured to allow different current strengths to flow in the windings of the switchable pole pair (12) than in the windings of the standard pole pair (11). [4] Rotor (10) according to any of the preceding claims, characterized by , that the winding of the second electromagnet (18) can be switched on or off via a power semiconductor (24), for example a SiC MOSFET. [5] Rotor (10) according to any of the preceding claims, characterized by , that the rotor (10) is designed as a salient pole rotor. [6] Rotor (10) according to any of the preceding claims except the preceding claim, characterized by , that the rotor (10) is designed as a full-pole rotor. [7] Electric machine with a rotor (10) according to one of the preceding claims. [8] Electric machine according to the preceding claim, characterized by, that the electrical machine is configured to be operated in at least two different modes, each of which is characterized by a specific selection of standard pole pairs (11) used and / or switchable pole pairs (12). [9] Electric machine according to one of the two preceding claims, characterized by , that the electric machine is set up to activate the mode depending on an operating range, for example a torque and / or a speed of the electric machine. [10] Traction drive with an electric machine according to one of claims 7, 8 or 9.

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