Rotor for electric machine having direct current converter

Abstract

The invention relates to a rotor for a current-excited electric machine. The rotor comprises: a rotor induction system comprising one or more electrically conductive rotor windings; and at least one slip ring for providing a slip ring current to the rotor. The rotor further comprises a rotor direct current converter which is designed to convert a slip ring current flowing through the slip ring into an excitation current which is increased by a conversion factor through the rotor induction system.

Description

Technical Field

[0001] The present invention relates to a rotor for an electric motor, particularly for a synchronous motor with current excitation. Background Technology

[0002] Electric vehicles have at least one drive motor, which can be configured as a current-excited synchronous motor. The torque induced by the drive motor can be highly correlated with the height of its excitation current. Typically, as the height of the excitation current increases, the requirements for the design of the brushes and slip rings, which are used to transmit the excitation current to the rotor windings of the drive motor's rotor, also increase. Alternatively or supplementarily, it may be necessary to increase the number of rotor windings, while limiting the height of the excitation current, in order to design the drive motor for a given target torque.

[0003] The increased size and / or number of rotor windings of slip rings lead to increased manufacturing costs and may result in increased rotor weight of the motor. Summary of the Invention

[0004] This paper addresses the following technical problem: to provide a particularly effective rotor for an electric motor with current excitation, and in particular a rotor that can be manufactured in a particularly effective manner.

[0005] The task is addressed by each independent claim. Advantageous embodiments are described, in particular, in the dependent claims. It should be noted that additional features of a dependent claim of an independent claim can form a separate invention independent of the combination of all the features of the independent claim, either without the features of the independent claim or simply in combination with a portion of the features of the independent claim. Such an invention can be the subject of an independent claim, a divisional application, or a subsequent application. This applies in the same manner to the technical teachings described in the specification, which can form an invention independent of the features of the independent claim.

[0006] According to a first aspect, a rotor for a current-excited motor (especially a synchronous motor) is described. The rotor includes a rotor induction system comprising one or more conductive rotor windings. The one or more rotor windings may be arranged around pole shoes of the rotor body (especially a lamination assembly).

[0007] The rotor also includes at least one slip ring (typically at least two slip rings) for providing slip ring current to the rotor. The one or more slip rings may be arranged circumferentially on the rotor shaft. The motor may have brushes that contact the corresponding one or more slip rings to provide slip ring current. A slip ring voltage (especially a DC voltage) may be applied between two slip rings. The slip ring current passing through the slip rings is typically a DC current.

[0008] The rotor also includes a rotor-to-DC converter configured to convert the slip ring current flowing through the slip rings into an excitation current through the rotor induction system with an increased conversion factor. In other words, the rotor-to-DC converter can be configured to (e.g., based on the slip ring voltage) induce an excitation current through the rotor induction system (i.e., through the one or more rotor windings) with a conversion factor higher than that of the slip ring current. The rotor-to-DC converter can, for example, be configured to induce a conversion factor of 2 or greater, particularly 5 or greater.

[0009] Therefore, a rotor is described that, due to the use of a DC-DC converter, particularly a buck converter, allows for a relatively high excitation current (with a correspondingly reduced excitation voltage) through the one or more rotor windings while the slip ring current (and relatively high slip ring voltage) is relatively small. This reduces the requirements on the current carrying capacity of the one or more slip rings and the number of rotor windings (while maintaining the same target torque of the motor). Thus, a particularly efficient rotor can be provided, especially one that can be manufactured in a particularly efficient manner.

[0010] The rotor-DC converter may include at least one active switching element, particularly a semiconductor-based switching element, configured to be repeatedly opened and closed to induce buck conversion, particularly buck conversion with a higher conversion factor. Here, the rotor-DC converter may be configured such that the (repeated) opening and closing of the active switching element induces an excitation current through the rotor induction system, which increases when the switching element is closed and decreases when the switching element is open (and, on a time average, has a higher conversion factor than the slip ring current). By providing an active switching element, the corresponding increase in DC conversion and excitation current can be induced in a particularly effective manner.

[0011] The rotor induction system can be a component of a rotor DC-DC converter. The rotor DC-DC converter can, for example, include a switched DC-DC converter, particularly a buck converter (especially one that can be configured as a switched DC-DC converter, particularly a buck converter), which utilizes the rotor induction system as the converter induction system. Therefore, the DC-DC converter can induce DC conversion in the rotor in a particularly efficient manner.

[0012] The rotor may include an energy supply module configured to supply electrical energy to the rotor-DC converter based on the slip ring voltage applied to the slip rings, and particularly based on the slip ring voltage applied between the two slip rings. Therefore, the rotor's efficiency can be further improved because a separate energy supply to the rotor for operating the rotor-DC converter can be abandoned.

[0013] The rotor can be configured to receive control signals, particularly control signals modulated onto the slip ring current. The rotor-DC converter can be configured to adjust the conversion factor according to the control signals.

[0014] This can cause changes in the conversion factor during motor operation (e.g., within the range of current regulation used to adjust the torque provided by the motor). This can result in particularly efficient and precise operation of the motor.

[0015] The rotor-DC converter, and especially the circuit board with the rotor-DC converter, is preferably disposed directly on the rotor shaft or disposed in a cavity of the (perhaps hollow) rotor shaft. Therefore, even when a rotor-DC converter is provided, a particularly uniform rotor operation can be achieved.

[0016] The rotor may include a circuit board on which a rotor-DC converter is mounted. Alternatively or supplementarily, the rotor may include one or more electronic components, particularly a temperature sensor and / or one or more components for compensating for electromagnetic fields induced by the rotor. These components can be provided on the circuit board in a particularly efficient manner. Therefore, the functionality of the motor can be effectively expanded.

[0017] The rotor may (e.g., on a circuit board) have one or more current sensors, which are accordingly configured to detect measurements of the slip ring current and / or excitation current. The rotor may also (e.g., on a circuit board) have one or more electronic components for providing current regulation, such as providing current regulation for regulating the slip ring current and / or excitation current.

[0018] As an alternative or supplement, the rotor may (e.g., on a circuit board) have at least one communication unit configured to communicate with a communication unit located outside the rotor. This communication unit allows data communication, such as radio-based, optical, and / or power line communication (PLC) based data communication. Through data communication, current ratings for regulating the slip ring current and / or excitation current can be provided to the rotor. Alternatively or supplementarily, measurements from one or more sensors on the rotor can be transmitted via data communication (to a receiver outside the rotor). This, for example, allows for the diagnosis of the rotor's condition.

[0019] According to another aspect, an electric motor, particularly a current-excited synchronous motor, is described, the motor including the rotor described herein.

[0020] According to another aspect, a motor vehicle (road motor vehicle), particularly a passenger car, a freight car, a bus, or a motorcycle, is described, which includes the electric motor described herein.

[0021] It should be noted that the apparatuses and systems described herein can be used not only individually but also in combination with other apparatuses and systems described herein. Furthermore, any aspect of the apparatuses and systems described herein can be combined with each other in a wide variety of ways. In particular, the features of the claims can be combined with each other in a wide variety of ways. Additionally, features set forth in parentheses should be understood as optional features. Attached Figure Description

[0022] The invention will now be described in more detail with the aid of embodiments. The accompanying drawings are as follows:

[0023] Figure 1a Exemplary components of a vehicle having a drive motor are shown;

[0024] Figure 1b Exemplary reverse rectifiers or inverters and exemplary devices for providing excitation current to a motor for a vehicle are shown.

[0025] Figure 1c Exemplary means for providing excitation current for the rotor of an electric motor are shown;

[0026] Figure 2a An exemplary rotor with a DC converter, particularly with a buck converter, is shown; and

[0027] Figure 2b An exemplary rotor is shown, wherein the rotor induction system is used as an induction system for voltage conversion. Detailed Implementation

[0028] As stated at the beginning, this paper aims to improve the rotor efficiency of currently excited motors. In this relationship, Figure 1a Exemplary components of a vehicle 140 are shown, the vehicle having a motor 103 for driving the vehicle 140. The motor 103 is coupled to one or more wheels 141 of the vehicle 140 for driving the one or more wheels 141 and thus driving the vehicle 140. The motor 103 operates by electrical energy from an electrical, particularly electrochemical, energy storage device 130. The energy storage device 130 may be configured to provide a direct current having a defined direct current voltage.

[0029] The vehicle 140 has an inverter 100 configured to generate phase currents for different phases of the motor 103 based on direct current from the energy storage 130. The inverter 100 can be operated via a device (control device) 101.

[0030] Figure 1b An exemplary inverter 100 is shown, which is configured to, based on the vehicle network voltage U DC Phase voltage 110 (i.e., DC voltage) generates phase voltage 111 (i.e., AC voltage) for the coils of motor 103. Inverter 100 may have an intermediate circuit with an intermediate circuit capacitor 105, and the on-board network voltage U... DC 110 is applied to the intermediate circuit capacitor.

[0031] The inverter 100 (or converter) includes multiple switches or switching elements 102, 104, which, in the described example, are arranged in a half-bridge for each phase 121, 122, 123. Each switching element 102, 104 is controlled by a (control) device 101 to generate a phase voltage 111 for the motor 103. Each individual phase current 112 and / or phase voltage 111 can be supplied to the motor 103 through a corresponding phase line.

[0032] The motor 103 may have a current-excited rotor having rotor windings that form a rotor induction system 151 (as exemplarily in...). Figure 1b and 1c (As described in the text). An excitation current 162 (especially a direct current) can flow through the rotor induction system 151, causing a magnetic field to be generated through the rotor induction system 151. The rotating magnetic field caused by the stator acts on this magnetic field to drive the rotor.

[0033] The excitation current 162 for the rotor induction system 151 can be supplied to the rotor via a slip ring 152, wherein the (rotating) slip ring 152 is in contact with (stationary) brushes 153. An excitation voltage 161 (especially a DC voltage) can be applied to the brushes 153, thereby inducing the excitation current 162. The level of the excitation voltage 161 can be adjusted by a DC-DC converter 154 configured to generate the excitation voltage 161 from a supply voltage 160 (which may correspond to the on-board network voltage 110).

[0034] The height of the excitation current 162 can be adjusted by the height of the excitation voltage 161, for example, in the case of current regulation. Here, the torque provided by the motor 103 typically increases with the height of the excitation current 162.

[0035] Motor 103 can be designed for a given maximum possible target torque. This may necessitate designing slip ring 152 for a relatively high excitation current 162. On the other hand, the target torque may necessitate a relatively high number of rotor windings (if the excitation current 162 should be limited). Therefore, designing motor 103 for a relatively high target torque may result in relatively high overhead when designing the rotor of motor 103.

[0036] This document describes a rotor (as exemplarily in...) Figure 2a and 2b As described in the diagram, the rotor has a rotor-DC converter 200 between the slip ring 153 and the rotor induction system 151. Here, the rotor induction system 151 can be advantageously used for voltage conversion. Figure 2a The rotor 150 is shown, wherein a slip ring voltage 261 (generated, for example, by a stationary converter 154) is applied between slip rings 152. A slip ring current 262 flows through the slip rings 152. The rotor 150 includes a (rotating) rotor DC-DC converter 200 configured to generate an excitation voltage 161 based on the slip ring voltage 261, which preferably has a defined conversion factor less than the slip ring voltage 261. Thus, a step-down conversion with a defined conversion factor can be induced by the rotor converter 200. In a corresponding manner, the excitation current 162 flowing through the rotor induction system 151 is increased relative to the slip ring current 262 (by conversion factor) by the rotor converter 200.

[0037] Therefore, the provision of the rotor converter 200 allows for a relatively high excitation current 162 for the rotor induction system 151 (in order to reduce the number of rotor windings) while employing a relatively low slip ring current 262 through the slip ring 152 (in order to reduce the requirements on the slip ring 152). This allows for a particularly efficient design of the rotor 150.

[0038] In a preferred embodiment, the rotor induction system 151 is used directly as a component of the rotor converter 200, as exemplarily in Figure 2b As described in [the text]. Figure 2bThe rotor converter 200 described herein is configured, for example, as a buck converter, with the converter sensing system corresponding to the rotor sensing system 151. The rotor converter 200 includes at least one active (semiconductor-based) switching element 201 that can be repeatedly opened and closed to induce voltage conversion. The switching element 201 can have an open phase and an closed phase, respectively, within one cycle, in which the switching element 201 is open and in which it is closed. The cycle can have a defined cycle duration T, the open phase can have an open duration To, and the closed phase can have a closed duration Tg. The conversion factor of the rotor converter 200 can typically be adjusted by a so-called duty cycle, which corresponds, for example, to the ratio of the closed duration to the cycle duration. The switching element 201 can be repeatedly opened and closed in a sequence of successive cycles to induce voltage conversion. The rotor converter 200 can therefore be a switching voltage converter.

[0039] The rotor converter 200 may also have additional (perhaps passive) switching elements 202 (e.g., diodes). Additionally, the rotor converter 200 may optionally have (filtering) capacitors, particularly capacitors.

[0040] The rotor converter 200 may operate with a (predetermined) constant switching factor. Therefore, the switching element 201 can operate with the same duty cycle, so that it is not necessary to transmit the control signal for the switching element 201 from outside the rotor 150 to the switching element 201.

[0041] On the other hand, it may be advantageous to change the cycle duration and / or duty cycle of the switching element 201 during the operation of the motor 103. In this case, a control signal (e.g., a control signal for the (control) device 101) can be transmitted to the drive circuit of the switching element 201 (the drive circuit is located on the rotor 150). The control signal can be modulated, for example, onto the slip ring current 262 (e.g., in the case of employing power line communication technology, i.e., PLC technology). Therefore, the provision of a separate signal line can be abandoned (with a separate slip ring for the signal line).

[0042] If the rotor converter 200 can be actively controlled by a control signal, then the rotor converter 200 can be connected to a current regulator for adjusting the excitation current 162. Therefore, it may be possible to simplify the (stationary, non-rotating) electronic device used to generate the excitation current 162.

[0043] The rotor 150 may have an energy supply module (not shown in the figure) for supplying energy to one or more active elements 201 of the rotor converter 200. The energy for operating the energy supply module and / or the one or more active elements 201 of the rotor converter 200 may be provided based on the slip ring voltage 261 (so that no additional energy supply line from the stationary parts of the motor 103 to the rotor 150 is required).

[0044] As explained at the beginning, in a current-excited synchronous motor 103 with slip rings 152, the electrical energy used to excite the rotor 150 is transmitted through one or more slip rings 152. Because the one or more slip rings 152 need to be sized according to the current 262 to be transmitted, it is typically advantageous to keep the slip ring current 262 small. If the slip ring current 262 corresponds to the excitation current 162, this can result in a relatively high number of windings (i.e., a relatively large number of parallel conductors) to generate the required excitation for the rotor 150. Manufacturing a relatively high number of windings with relatively thin wires is technically demanding. Furthermore, this may therefore affect the mechanical stability and inductance.

[0045] The following measures are described herein: In the case of using a buck converter 200 integrated in rotor 150, the measures allow the desired rotor excitation to be generated by means of a relatively small number of windings and a relatively high excitation current in a single conductor, while the slip ring current is relatively small.

[0046] Through the measures described herein, the current intensity of power transmitted through the one or more slip rings 152 can be kept relatively small. Furthermore, the windings on the rotor 150 can be manufactured with a relatively small number of windings and a relatively large conductor cross-section.

[0047] The power supplied to rotor 150 (with a relatively high slip ring voltage 261 and a relatively small slip ring current 262) can be converted on rotor 150 by means of buck converter 200 into a relatively high excitation current 161 with a relatively small excitation voltage 162. The induction system for buck converter 200 can be formed by the rotor windings, i.e., by the rotor induction system 151 itself. The excitation current 162 can be greater than the slip ring current 262 with a conversion factor of converter 200. The excitation voltage 161 can be less than the slip ring voltage 261 with a conversion factor of converter 200.

[0048] The measures described herein can simplify the manufacture of the rotor windings. Additionally, the strength and speed of the rotor 150 can be improved. Furthermore, demagnetization around the rotor 150 can be improved (by reducing the induction system). Furthermore, the use of semiconductors in the rotor 150 allows for the possibility of additional functions, such as active demagnetization and / or temperature measurement within the rotor 150.

[0049] The windings on the rotor 150 can be manufactured using rectangular copper enameled wire (with a relatively large cross-section). The winding connections can be made in advance using a PCB (printed circuit board), such as an IMS board (insulated metal substrate circuit board), on which (perhaps the entire) electronics are also mounted. The PCB can be axially inserted into the rotor 150. The PCB can then be connected to one or more slip rings 152.

[0050] The cost and / or weight of the rotor 150 of the motor 103 can be reduced by the measures described herein without reducing the target torque that can be provided by the motor 103.

[0051] The present invention is not limited to the embodiments shown. In particular, it should be noted that the specification and drawings are intended to illustrate the principles of the proposed apparatus and systems merely by way of example.

Claims

1. A rotor (150) for a current-excited motor (103), the rotor (150) comprising: A rotor induction system (151) includes one or more conductive rotor windings; At least one slip ring (152) for providing slip ring current (262) to the rotor (150); and A rotor DC-DC converter (200) is configured to convert a slip ring current (262) flowing through a slip ring (152) into an excitation current (162) through a rotor induction system (151) with a conversion factor increased.

2. The rotor (150) according to claim 1, wherein, The rotor (150) has at least two slip rings (152), and a slip ring voltage (261) is applied to each slip ring; and The rotor DC-DC converter (200) is configured to generate an excitation current (162) based on the slip ring voltage (261).

3. The rotor (150) according to any one of the preceding claims, wherein, The rotor DC-DC converter (200) includes at least one active, in particular semiconductor-based, switching element (201) configured to be repeatedly opened and closed to induce buck conversion, in particular buck conversion with conversion factor.

4. The rotor (150) according to claim 3, wherein, The rotor DC-DC converter (200) is configured such that repeated opening and closing of an active switching element (201) causes an excitation current (161) through the rotor induction system (151), which increases when the switching element (201) is closed and decreases when the switching element (201) is open.

5. The rotor (150) according to any one of the preceding claims, wherein, The rotor induction system (151) is a component of the rotor DC converter (200).

6. The rotor (150) according to any one of the preceding claims, wherein, The rotor DC-DC converter (200) includes a switching DC-DC converter, particularly a buck converter, which utilizes a rotor induction system (151) as the converter induction system.

7. The rotor (150) according to any one of the preceding claims, wherein, The rotor (150) includes an energy supply module configured to supply electrical energy to the rotor DC-DC converter (200) based on the slip ring voltage (261) applied to the slip rings (152), and in particular based on the slip ring voltage (261) applied between the two slip rings (152).

8. The rotor (150) according to any one of the preceding claims, wherein, The rotor (150) is configured to receive control signals, particularly control signals modulated onto the slip ring current (262); and The rotor DC-DC converter (200) is configured to adjust the conversion factor according to the control signal.

9. The rotor (150) according to any one of the preceding claims, wherein, The rotor (150) has a rotor shaft; and The rotor DC-DC converter (200), and especially the circuit board having the rotor DC-DC converter (200), is directly mounted on the rotor shaft or mounted in a cavity of the rotor shaft.

10. The rotor (150) according to any one of the preceding claims, wherein, The rotor DC-DC converter (200) is configured to produce a conversion factor of 2 or greater, especially 5 or greater.

11. The rotor (150) according to any one of the preceding claims, wherein, The rotor (150) includes: A circuit board on which a rotor-DC converter (200) is mounted; and One or more electronic components, particularly temperature sensors and / or one or more components for compensating for the electromagnetic field caused by the rotor (150), particularly each of the aforementioned components is disposed on a circuit board.

12. A current-excited synchronous motor (103), the synchronous motor comprising a rotor (150) according to any one of the preceding claims.

Images