Separate-excited synchronous machine, motor vehicle, and method for operating separate-excited synchronous machine

Abstract

The invention relates to a separately excited synchronous machine (1), comprising a stator (2) and a rotor (3) that can be rotated relative to the stator (2), the rotor (3) having an excitation winding (4) for providing a rotor magnetic field during operation of the synchronous machine (1), the synchronous machine (1) having an inductive transmission system (5) for wirelessly transmitting electrical power for operating the excitation winding (4) to the excitation winding (4), in order to carry out data transmission between a rotor-external control device (9) and a rotor-side control unit (16) of the separately excited synchronous machine (1), the synchronous machine (1) also has a capacitive transmission device (11), which has a stationary first transmitter (18) and a second transmitter (19) arranged on an end side (23) of the rotor (3) opposite the first transmitter (18).

Description

Technical Field

[0001] The invention relates to a separately excited synchronous machine, comprising a stator and a rotor rotatable relative to the stator, wherein the rotor has an excitation winding for providing a rotor magnetic field during operation of the synchronous machine, wherein the synchronous machine has an inductive transmission system for wirelessly transmitting electrical power for operating the excitation winding to the excitation winding. The invention also relates to a motor vehicle and a method for operating a separately excited synchronous machine. Background Art

[0002] In electrified vehicles, such as electric vehicles and hybrid vehicles, synchronous machines are usually used as power machines (power machines). A special embodiment of a synchronous machine is a so-called separately excited synchronous machine.

[0003] Compared to permanent magnet synchronous motors, the rotor of this type of motor does not use magnetic material, but instead generates the rotor magnetic field by means of an excitation winding energized in the rotor. This advantageously provides additional degrees of freedom in the regulation and design of the separately excited synchronous motor. As a result, an increase in efficiency and performance can be achieved. In known solutions, the energization of the excitation winding is either achieved via slip ring contacts or contactlessly by transmitting power via an inductive transmission system with an inductive rotary transmitter (Drehübertrager). In particular, the inductive power transmission system includes a stationary inverter, an inductive rotary transmitter, a rotating rectifier, and a filter for smoothing the excitation current. With the aid of this transmission system, a DC voltage can be generated contactlessly to drive the excitation current in the excitation winding of the rotor of the separately excited synchronous motor.

[0004] The field current is controlled by driving the stationary inverter with the aid of corresponding control information. This is calculated by means of complex and cost-intensive estimation algorithms. This can lead to large deviations or inaccuracies in providing the correct field current during operation. The strong temperature dependence of the rotor resistance leads precisely to large deviations in the model used by the estimation algorithm, so that the wrong field current is set at certain operating points. This leads to incorrect torques, which can in particular violate functional safety requirements. Overall, the estimation algorithm requires a large computational effort, and a high safety buffer must be provided for incorrect field currents, and an oversize must be used (lower efficiency of the overall system).

[0005] During driving, in particular, sensor data of a rotor position sensor describing the angular position of the rotor is used. The precise rotor position determined in this way is used for efficient and dynamic torque regulation. Known rotor position sensors include, for example, synchronous converters using inductive measurement methods and sensors using the magnetoresistance effect (TMR).

[0006] For improvement in other applications, it is proposed that communication with a control unit in the rotating element is possible in order to transmit measurement data from the rotating element to an external control device, for example.

[0007] WO 2018 / 015 774A1 discloses a device for measuring temperature or other physical quantities, wherein signals and energy are transmitted in a contactless manner. The contactless energy transmission is achieved by inductive coupling, and the contactless signal transmission is achieved by differential capacitive coupling. The application scenarios involve disc brakes and clutch components. Summary of the invention

[0008] It is therefore the object of the present invention to specify a more robust, simpler and improved separately excited synchronous machine with regard to material and / or computational costs.

[0009] This object is achieved according to the invention by a separately excited synchronous machine, a motor vehicle and a method for operating a separately excited synchronous machine according to the independent claims. Advantageous developments result from the dependent claims.

[0010] According to the invention, for a separately excited synchronous machine of the type mentioned at the outset, for data transmission between a rotor-external control device of the separately excited synchronous machine and a rotor-side control unit, the synchronous machine also has a capacitive transmission device having a first stationary transmitter and a second transmitter arranged at the rotor end opposite the first transmitter. Particularly preferably, the capacitive transmission device is also designed as a rotor position sensor for determining the angular position of the rotor.

[0011] As is known, correspondingly dimensioned inductive transmission systems are used for power transmission. In particular, the inductive transmission system can include, for example, a stationary converter / inverter on the stator side, an inductive rotating transmission and a rectifier on the rotor side. A smoothing filter can also be provided on the rotor side. These components can be driven by means of a control device or a control unit in order to set a specific excitation current in the excitation winding.

[0012] According to the invention, it is proposed to supplement the inductive rotary transmission in a separately excited synchronous motor with a capacitive channel. Unlike the inductive channel, which is used to transmit power or energy, the capacitive channel only transmits data signals and can therefore be designed to be relatively small in comparison. The capacitive transmission of the data signal increases the robustness of the overall system, since the capacitive transmission is less susceptible to electromagnetic interference. It has proven to be advantageous that such capacitive data transmission is particularly advantageous for separately excited synchronous motors.

[0013] In particular, it is possible and preferred within the scope of the invention that the rotor has at least one rotor sensor, wherein the control unit is designed to transmit sensor data of the at least one rotor sensor to the control device via a capacitive transmission device, and / or the control device is designed to transmit current information for providing the excitation current to the control unit via a capacitive transmission device. At least one of the at least one rotor sensor can be selected from the following sensors: a rotor temperature sensor, a rotor current sensor and a rotor voltage sensor. It is advantageous here that the rotor current and the rotor voltage are measured on the excitation winding so that the rotor current corresponds to the actually applied excitation current. Advantageously, after the control device is designed to use the sensor data to regulate the excitation current, it can be provided that the sensor data (in particular the rotor temperature and / or the rotor current and / or the rotor voltage) are acquired by means of the at least one rotor sensor, transmitted to the control device by means of the control unit via the capacitive transmission device and used by means of the control device to regulate the excitation current. This can be achieved by correspondingly driving the inverter of the inductive transmission system and / or by correspondingly transmitting the current information to the control unit. A closed rotor control loop is thus achieved, in which the control device determines the excitation current to be set by driving the inverter, the corresponding excitation power is supplied to the rotor via the inductive transmission system, the rotor state caused at least in part by this is measured, and the corresponding sensor data are transmitted to the control device by means of the capacitive transmission system in order to be used for the next control step.

[0014] Specifically, in one embodiment, the rotor current signal, the rotor voltage signal and the rotor temperature signal can be detected as sensor data on the rotor side, and transmitted from the rotating secondary side to the stationary primary side (stator side) via a control unit, in particular an integrated microcontroller, and then transmitted from the primary side to a control device outside the rotor. In general, the sensor data for regulation can be directly detected and the regulation of the separately excited synchronous motor can be improved or the efficiency of the separately excited synchronous motor can be improved, especially in a motor vehicle with an overall power system. In addition, the complex estimation algorithm for estimating the corresponding information can be eliminated by the precise measurement of the sensor data. Since there is no longer a deviation in the excitation current, the robustness of the separately excited synchronous motor is improved. In addition, all requirements for functional safety are met in this way.

[0015] In summary, during the direct measurement of sensor data in the rotor and the provision of these sensor data via capacitive data transmission and the application outside the rotor, the following advantages can be achieved: computationally intensive estimation algorithms for estimating the excitation current and / or estimating the rotor state can be eliminated, so that the design complexity of the control device can be reduced. High precision of the excitation current is achieved in the excitation winding, so that the safety buffer can be eliminated. A significant increase in the efficiency of the separately excited synchronous motor is achieved. At the same time, a reduction in the material costs of power electronic components is achieved. In addition, the high precision of the excitation current enables a more robust design. Over-dimensioning / over-dimensioning can be eliminated. Capacitive data transmission is not susceptible to electromagnetic interference, which helps to improve robustness, so the risk of errors in the excitation current and torque of the synchronous motor is low, especially in the electric power system of a motor vehicle.

[0016] In a particularly preferred development of the invention, as already mentioned, the capacitive transmission device is also designed as a rotor position sensor for determining the angular position of the rotor. The control device can accordingly be designed to take the angular position into account when driving the separately excited synchronous motor. This makes it possible to achieve efficient and dynamic torque control.

[0017] By using a capacitive transmission device as a rotor position sensor, the conventional rotor position sensor can be eliminated, thereby achieving further simplification and reduction of material costs. Nevertheless, the rotor position information important for the separately excited synchronous motor can still be reliably obtained.

[0018] In particular, it can be provided that one of the transmitters, in particular the first transmitter, comprises a non-circumferentially designed, local capacitive transmission element, and the other transmitter, in particular the second transmitter on the rotor end side, comprises an annularly encircling capacitive transmission element, whose capacitive characteristic changes in the circumferential direction, wherein the control device and / or the control unit are designed to determine the angular position using characteristic information describing the change. It is advantageous here that a local, in particular at least substantially point-shaped capacitive sensor is provided as the first transmitter, which has a corresponding transmission element that does not extend in the circumferential direction. For example, the transmission element of one transmitter, in particular the first transmitter, can have an at least substantially rectangular shape at a radial position of the annular other transmission element and / or the shape of a short ring segment, for example covering an angle of 10° or less. The capacitive sensor measures the current capacitance of the second transmission element of the second transmitter, which extends annularly at a radial position on the end side of the capacitive sensor, which current capacitance changes depending on the angular position of the rotor. Thus, the control device requiring rotor position information can determine the angular position, in particular in addition to the transmitted data signal, in particular sensor data. Information and data are thus provided where they are needed. In particular, the greatest possible coverage of the transmission element in the rotational plane is ensured.

[0019] Specifically, the change in the capacitance characteristic can be related to the geometrical dimensions and / or shape of the transmission element, in particular to the dimensions of the transmission element in the radial direction and / or the material thickness of the transmission element. In addition, it can be provided that the change relates to the material and / or coating of the transmission element. These solutions can be used in a complementary manner.

[0020] In other words, there are a number of possibilities for adapting the capacitive properties of a transmission element extending around the entire circumference so that different capacitances result in different angular positions. The transmission element, which is preferably arranged on the rotor end side and is, for example, disk-shaped, is designed such that the capacitance of the transmission path changes as a function of the rotor angle. This can be achieved, for example, by the following design:

[0021] - the variation of the material thickness of the transmission element, i.e. the dimension of the transmission element in the axial direction,

[0022] - the variation of the transmission element width, i.e. the dimension of the transmission element in the radial direction, and

[0023] - Changes in the coating of transmission elements.

[0024] The coating may be a coating having a dielectric in order to locally vary the capacitance.

[0025] In particular, it can be provided that at least one of the capacitive transmission elements is designed as an electrically conductive plate, in particular a metal plate. Alternatively or additionally, at least one of the transmission elements can also be embodied as a layer, for example a metal layer.

[0026] In addition to a separately excited synchronous machine, the invention also relates to a motor vehicle comprising a separately excited synchronous machine according to the invention. In this case, the separately excited synchronous machine is in particular a power motor of a motor vehicle, i.e. part of an electric (or hybrid) drive train. All embodiments of the separately excited synchronous machine according to the invention can be transferred analogously to the motor vehicle according to the invention, with which the advantages already mentioned can also be achieved.

[0027] In the method according to the invention for operating a synchronous machine according to the invention, it is provided that data is transmitted between a rotor-external control device of a separately excited synchronous machine and a rotor-side control unit via a capacitive transmission device. Particularly preferably, the angular position of the rotor is also determined by means of the capacitive transmission device. The embodiments of the separately excited synchronous machine and the motor vehicle also apply to the method. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Further advantages and details of the invention emerge from the exemplary embodiments described below and with reference to the drawings.

[0029] in:

[0030] Figure 1 The schematic diagram of the separately excited synchronous motor according to the present invention is shown.

[0031] Figure 2 A schematic diagram showing a transmission element,

[0032] Figure 3 A possible design of the rotor-side transmission element is shown, and

[0033] Figure 4 A schematic diagram of a motor vehicle according to the invention is shown. DETAILED DESCRIPTION

[0034] Figure 1 The functional principle diagram of a separately excited synchronous machine 1 according to the invention is shown. The separately excited synchronous machine comprises a stator 2 and a rotor 3 with an excitation winding 4. The excitation winding 4 is provided with an inductive transmission system 5 for power, which has a stationary inverter 6, an inductive rotary transmission 7 and a rotor-side rectifier 8. Further components, such as components for current smoothing, may also be provided.

[0035] The rotor-external control device 9 is designed to drive the inverter 6 to adjust a certain excitation current, see arrow 10 . This regulation is based on sensor data which are acquired inside the rotor 3 and transmitted wirelessly to the control device 9 by means of a capacitive transmission device 11 .

[0036] To this end, the rotor 3 has a rotor sensor 12 which in the present case comprises a temperature sensor 13 for measuring the rotor temperature, a rotor current sensor 14 for measuring the rotor current on the excitation winding 4 (i.e. measuring the actual excitation current) and a rotor voltage sensor 15 for measuring the rotor voltage on the excitation winding 4.

[0037] The sensor data of these rotor sensors 12 are transmitted by the control unit 16 of the rotor 3, which is designed as a microchip, via the capacitive transmission device 11 to the control device 9, see arrow 17, so that the control device can adjust the excitation current with high precision in a closed-loop control circuit. In principle, it is also conceivable to transmit the current information for driving the internal components of the rotor from the control device 9 to the control unit 16 in the other direction, for example by means of the capacitive transmission device 11.

[0038] In the present case, the capacitive transmission device 11 is also designed as a rotor position sensor, wherein the corresponding angular position of the rotor 3 is also used by the control device 9 when driving a separately excited synchronous machine.

[0039] Reference Figure 2 and Figure 3 The embodiment of the capacitive transmission device 11 provided for this purpose is described in detail. Figure 2 Schematically shown, the capacitive transmission device 11 comprises a first transmitter 18 of the stator 2 and a second transmitter 19 of the rotor 3. Here, the stationary first transmitter 18 comprises a capacitive sensor 20 having a capacitive transmission element 21 formed locally at the location of the capacitive sensor 20. The capacitive sensor 20 thus measures at a certain angular position.

[0040] In contrast, the capacitive transmission element 22 of the second transmitter 19 is designed in an annular manner at a radial position of the capacitive transmission element 21 with reference to the axis of rotation. Figure 3 The capacitive transmission element 22 formed on the end side 23 of the rotor 3 is shown in more detail.

[0041] The capacitive transmission element 22, which can be designed as an annular disk or annular plate made of a conductive material (e.g. metal), obviously has an irregularly changing shape and / or size in the circumferential direction. This means that the capacitive characteristics of the capacitive transmission element change along the circumferential direction, so that the capacitive sensor 20 measures different capacitances depending on the angular position of the rotor 3, thereby being able to accurately determine the angular position of the rotor 3. Other measures for changing the capacitive characteristics in the circumferential direction include changing the material thickness of the capacitive transmission element 11 and changing the coating of the capacitive transmission element 11.

[0042] After the characteristic information describing the change in the capacitance characteristic has been supplied to the control device 9 , the control device 9 can determine the angular position from the measured capacitance.

[0043] at last, Figure 4 The schematic diagram of a motor vehicle 24 according to the invention is shown, which comprises a separately excited synchronous machine 1 according to the invention as a drive machine, which forms part of an electric drive train.

Claims

1. A separately excited synchronous motor (1), comprising a stator (2) and a rotor (3) rotatable relative to the stator (2), wherein: The rotor (3) has an excitation winding (4) for providing a rotor magnetic field when the synchronous motor (1) is in operation, wherein the synchronous motor (1) has an inductive transmission system (5) for wirelessly transmitting electric power for operating the excitation winding (4) to the excitation winding (4). It is characterized in that For data transmission between a control device (9) outside the rotor of a separately excited synchronous motor (1) and a control unit (16) on the rotor side, the synchronous motor (1) also has a capacitive transmission device (11) having a stationary first transmitter (18) and a second transmitter (19) arranged on the end side (23) of the rotor (3) and opposite to the first transmitter (18).

2. The separately excited synchronous motor according to claim 1, It is characterized in that The capacitive transmission device (11) is also designed as a rotor position sensor for determining the angular position of the rotor (3).

3. The separately excited synchronous motor according to claim 2, It is characterized in that One of the transmitters (18, 19), in particular the first transmitter (18), comprises a non-circumferentially designed, local capacitive transmission element (21), while the other transmitter (19, 18), in particular the second transmitter (19) on the end side (23) of the rotor (3), comprises an annularly surrounding capacitive transmission element (22), the capacitance characteristic of which changes in the circumferential direction, wherein the control device (9) and / or the control unit (16) is designed to determine the angular position using characteristic information describing the change.

4. The separately excited synchronous motor according to claim 3, It is characterized in that The variation is related to the geometrical dimensions and / or shape of the capacitive transmission element (22), in particular to the dimension in the radial direction and / or the material thickness of the transmission element (22).

5. The separately excited synchronous motor according to claim 3 or 4, It is characterized in that The variation is dependent on the material and / or the coating of the transmission element (22).

6. The separately excited synchronous motor according to any one of claims 3 to 5, It is characterized in that At least one of the capacitive transmission elements (21, 22) is designed as an electrically conductive plate, in particular a metal plate.

7. A separately excited synchronous motor according to any one of the preceding claims, It is characterized in that The control device (9) is designed to transmit current information for providing an excitation current to a control unit (16) via a capacitive transmission device (11).

8. A separately excited synchronous machine according to any one of the preceding claims, It is characterized in that The rotor (3) has at least one rotor sensor (12), wherein the control unit (16) is designed to transmit sensor data of the at least one rotor sensor (12) to the control device (9) via a capacitive transmission device (11).

9. The separately excited synchronous motor according to claim 8, It is characterized in that At least one of the at least one rotor sensor (12) is selected from the group consisting of a rotor temperature sensor (13), a rotor current sensor (14), and a rotor voltage sensor (15).

10. A motor vehicle (24) comprising a separately excited synchronous machine (1) according to any one of the preceding claims.

11. A method for operating a separately excited synchronous machine (1) according to any one of claims 1 to 9, characterized in that: Data is transmitted between a control device (9) outside the rotor of a separately excited synchronous motor (1) and a control unit (16) on the rotor side via a capacitive transmission device (11).

12. The method according to claim 11, It is characterized in that The angular position of the rotor (3) is determined by means of a capacitive transmission device (11).

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