Separate excitation synchronous motor and motor vehicle

Abstract

The invention relates to a separately excited synchronous machine having a rotor (3) rotatably mounted on a stator (2), the rotor (3) having a rotor winding (4) for generating a rotor magnetic field, the synchronous machine (1) having an inductive energy transfer circuit for supplying the rotor winding (4), the energy transmission circuit comprises a stator-side primary winding (6), a rotor-side secondary winding (7) and a rectifying circuit (8) for rectifying an alternating current provided by the secondary winding (7) in order to supply the rotor winding (4), the rotor (3) having a cooling chamber (9) through which a cooling liquid (10) flows in at least one operating state of the synchronous machine (1), at least one electrical component (11-14) of the rectifying circuit (8) is arranged in the cooling chamber (9) such that the at least one electrical component is in direct contact with the cooling liquid (10) at least in the operating state.

Description

TECHNICAL FIELD

[0001] The invention relates to a separately excited synchronous machine having a rotor rotatably supported on a stator, wherein the rotor has a rotor winding for generating a rotor field, wherein the synchronous machine has an inductive energy transfer circuit for supplying the rotor winding with electrical energy, wherein the energy transfer circuit comprises a primary winding on the stator side, a secondary winding on the rotor side and a rectifier circuit for rectifying an alternating current provided by the secondary winding in order to supply the rotor winding with electrical energy, wherein the rotor has a cooling cavity which is flowed through by a cooling liquid in at least one operating state of the synchronous machine. Furthermore, the invention also relates to a motor vehicle. BACKGROUND

[0002] In contrast to permanent-magnet synchronous machines, separately excited synchronous machines do not require permanent magnets in the rotor and generate the rotor field by supplying the rotor winding of the rotor with electrical energy. In comparison with the use of permanent magnets, additional degrees of freedom arise in the regulation and design of the machine, whereby the efficiency and the performance can be improved.

[0003] The supply of the rotor winding can be effected by means of slip ring contacts or in a contactless manner by means of a power transfer system having an inductive rotary transformer. In the second case, the supply of the rotor winding can be effected by means of a power transfer system having an inverter, an inductive rotary transformer, a rotary rectifier and optionally a filter for smoothing the field current.

[0004] For high-power machines, for example when the synchronous machine is used as a drive machine for a motor vehicle, the waste heat generated when rectifying the coil current of the rotor winding or the discharge of this waste heat from the rectifier can limit the power of the synchronous machine at least in some operating situations.

[0005] A synchronous machine is known from document DE 10 2021 212 017 A1 in which components of the rotor-side rectifier are arranged on a circuit board, the back side of which rests against a cooling body. A cooling fluid for cooling the rotor flows through cooling ribs which are arranged on the side of the cooling body which faces away from the circuit board. SUMMARY

[0006] It is therefore an object of the invention to further improve the efficiency of a separately excited synchronous machine.

[0007] The object is achieved according to the invention by a separately excited synchronous machine of the type mentioned at the outset, wherein at least one electrical component of the rectifier circuit is arranged in the cooling cavity, so that the at least one electrical component is in direct contact with the cooling liquid at least in the operating state.

[0008] In contrast to an indirect cooling of the components, by the provision according to the application a significantly improved thermal coupling of at least one electrical component to the cooling liquid is achieved. When cooling via a cooling body and a circuit board arranged thereon a relatively long thermal path is formed, which significantly reduces the transferable heat even in the case of a suitable selection of the materials for the cooling body and the circuit board, which is avoided by the design according to the application of the synchronous machine.

[0009] In particular if an insulating cooling liquid, for example oil, is used, by which the electrically conductive section of the at least one component can be directly contacted by the cooling liquid, the cooling of the components can be significantly improved, by which in turn a higher current and thus a higher rotor field of the rotor winding can be used. A faster build-up and extinction of the rotor field can furthermore be achieved by the better cooling. Thus, in the case of otherwise identical construction, a better performance of the synchronous machine of a motor vehicle or of a drive train comprising the synchronous machine, for example a higher maximum power and a constant power, is produced compared to the case of an indirect cooling.

[0010] Furthermore, by the improved active cooling the electronics can be designed more efficiently, by which material costs can be reduced, since an oversizing of the electronics, which can be necessary in the case of a lower cooling efficiency in order to provide a thermal reserve, is no longer required. Furthermore, the improved cooling can increase the robustness and the service life of the rotor-side electronics, since smaller thermal gradients can be achieved in the case of load situations. Furthermore, the direct cooling of the components can omit a large cooling body for the entire circuit board or other possibly heavy and / or voluminous components for improving the cooling. Thus, the weight and / or the space requirement of the synchronous machine can be reduced.

[0011] The "cooling cavity is traversed by a cooling liquid" can always be achieved in the operation of the separately excited synchronous machine or for example only in operating states in which the separately excited synchronous machine is to provide a high power and thus to dissipate a high waste heat. The "cooling liquid is conveyed through the cooling cavity" can be achieved by the operation of the synchronous machine itself and / or by a pump as a component of the synchronous machine or by an external pump, for example a pump of a motor vehicle comprising the synchronous machine.

[0012] The rectifier circuit can optionally comprise electrical components for filtering the rectified current in order to reduce the ripple of the current delivered to the rotor winding. Preferably, the electrical components or at least one of the electrical components arranged within the cooling cavity are rectifying components. Optionally, the electrical components for filtering the rectified current can additionally be arranged within the cooling cavity, since these components can also generate a large amount of waste heat. In particular, all electrical components of the rectifier circuit together with the components for filtering can be arranged within the cooling cavity.

[0013] The pump for conveying the cooling liquid and / or the heat exchanger for tempering the cooling liquid can be provided, for example, on the stator side or arranged as a separate component, in particular fixedly with respect to the stator position. The liquid inlet and / or the liquid outlet can be designed in a manner known per se as a fluid guide between components rotating relative to one another, for example by means of a labyrinth seal or the like. Alternatively, it is also possible in principle to integrate the entire cooling circuit into the rotor.

[0014] The electrical component or at least one of the electrical components can be a semiconductor switch or a diode. Thus, in particular, components which actively or passively rectify an electrical current can be directly cooled. Thus, in particular, components which heat up particularly strongly during rectification are in direct contact with the cooling liquid and thus directly cooled.

[0015] The electrical connection and / or the conductor track of the circuit board carrying the respective component which is in contact with the electrical connection can directly adjoin the cooling cavity and thus, in the operating state, be in direct contact with the cooling liquid. Since the electrical connection or the conductor track in contact with the electrical connection typically has a high thermal conductivity, the waste heat of the component can thus be particularly efficiently removed.

[0016] The cooling liquid can be an oil and / or electrically insulating. If an electrically conductive cooling liquid is used, the contact of the cooling liquid with the respective component must be limited to an insulating section of the component, for example its housing, and / or it must be ensured that only electrically conductive regions at the same potential come into contact with the cooling liquid or the relevant partial volume of the cooling liquid. By using an electrically insulating cooling liquid, electrically conductive components at different potentials can also come into contact with the cooling liquid without this leading to a short circuit. An oil has proven to be particularly suitable as a cooling liquid, since it is not only electrically insulating, but also has a high heat capacity and can additionally act as a lubricant, for example when further components of the synchronous machine are also to be cooled by the cooling cavity.

[0017] The cooling cavity can be designed as a cooling channel at least in the section in which the at least one component is arranged, which cooling channel is provided for guiding the cooling liquid from one or more cooling liquid inlets to one or more cooling liquid outlets and which cooling channel is liquid-tight apart from the at least one cooling liquid inlet and the at least one cooling liquid outlet.

[0018] For example, the cooling cavity can be part of a cooling system enclosed at least within the rotor, which cooling system is connected to a portion of the stator side of the cooling system by means of the respective cooling liquid inlet and cooling liquid outlet. It is however also suitable for at least portions of the cooling liquid outlet to guide the cooling liquid into a free space surrounding the rotor, for example in order to cool the rotor coil in the region of the air gap of the synchronous machine.

[0019] The cooling chamber may be a cooling channel or include a cooling channel that extends along the rotor shaft in the axial direction of the synchronous motor. Specifically, the cooling channel may extend through the rotor shaft such that coolant is supplied axially to a first side of the rotor winding via a coolant inlet on the stator side and discharged axially on a second side of the rotor winding via a coolant outlet on the stator side. Alternatively, however, the coolant may be diverted within the rotor shaft, for example, by using coaxial cooling channels that guide the coolant in different directions, so that the coolant inlet and outlet on the stator side are arranged axially on one side of the rotor.

[0020] At least one electrical component of the rectifier circuit, or the entire rectifier circuit, can be arranged in a cooling channel that extends along the rotor shaft in the axial direction of the synchronous motor. Specifically, the circuit board carrying the electrical component, or rectifier circuit, can extend parallel to the axial direction. To better fit this circuit board to the channel geometry of the cooling channel, a curved or flexibly bendable circuit board can be used.

[0021] Instead of circuit boards, electrical components can also be supported directly by the walls of such cooling channels. If the coaxial cooling channels are used to guide coolant in different directions, then, for example, the partition walls separating the cooling channels can support at least one electrical component.

[0022] Integrating at least one electrical component of the rectifier circuit into a cooling channel is particularly efficient in terms of structural space because the geometry of the already known cooling channel, which can also be used for other cooling tasks, requires no modification or at most only slight modification to achieve the cooling of the component. Therefore, a separate cooling channel for delivering coolant to the component is unnecessary. Furthermore, for example, an orientation parallel to the radial direction of the rotor relative to the circuit board carrying the rectifier circuit allows for a smaller rotor and thus a smaller synchronous motor.

[0023] The corresponding sections defining the boundary surfaces of the cooling cavity can be formed by secondary windings and / or primary windings, so that the secondary windings and / or primary windings can be cooled by coolant during operation. This allows for active cooling of the primary windings and / or secondary windings at a lower cost. Active cooling of the corresponding windings enables higher power transfer for a given winding design. Furthermore, compared to situations where such active cooling is not required, a given power transfer can be achieved, for example, with smaller conductor cross-sections of the windings and therefore lower material consumption due to active cooling.

[0024] The rectifier circuit can be configured to actively rectify the AC power supplied by the secondary winding through multiple semiconductor switches. The control device for the control semiconductor switches of the synchronous motor can be configured to transfer power from the primary winding to the secondary winding in a first operating state of the synchronous motor and to transfer power from the secondary winding to the primary winding in a second operating state of the synchronous motor.

[0025] The second operating state is suitable, for example, for recovering the energy used to generate the rotor magnetic field when the rotor magnetic field decreases, such as when the synchronous motor has finished operating, and / or for particularly rapid reduction of the current in the rotor windings, for example, in the event of an accident involving a motor vehicle using a synchronous motor. The rectifier circuit can therefore also operate, in particular, as an inverter or typically as a converter. Thus, the direct current flowing through the rotor windings to maintain the rotor magnetic field can be inverted so that it can be transmitted to the primary winding via the secondary winding.

[0026] The aforementioned active cooling, in which at least one active component of the rectifier circuit, or the converter circuit forming the rectifier circuit, is in direct contact with the coolant via at least one electrical component, can be achieved in the first operating state and / or the second operating state.

[0027] In addition to the separately excited synchronous motor according to the invention, the invention also relates to a motor vehicle that includes the separately excited synchronous motor according to the invention. Because separately excited synchronous motors (if they are to be used as drive motors in motor vehicles) generally require particularly high power density, the design of the separately excited synchronous motor according to the invention for use in motor vehicles is particularly advantageous.

[0028] Motor vehicles may include other components formed separately from the synchronous motor, such as at least one pump for delivering coolant and / or at least one heat exchanger for regulating the temperature of the coolant. Alternatively, these components may be at least partially integrated into the synchronous motor itself, such as the stator. Attached Figure Description

[0029] Other advantages and details of the invention will become apparent from the following embodiments and accompanying drawings. The figures show:

[0030] Figure 1 Detailed drawings are shown of one embodiment of a separately excited synchronous motor according to the present invention, and

[0031] Figure 2 An embodiment of a motor vehicle according to the present invention is shown. Detailed Implementation

[0032] Figure 1A detailed view of a separately excited synchronous motor 1 with a rotor 3 rotatably supported on a stator 2 is shown. The rotor 3 has a rotor winding 4 for generating a rotor magnetic field, wherein the energy required to power the rotor winding 4 is transferred from the stator 2 to the rotor 3 via an inductive energy transfer circuit. Here, the energy transfer circuit includes a primary winding 6 on the stator side, an inverter 35 for powering the primary winding 6, a secondary winding 7 on the rotor side, and a rectifier circuit 8 for rectifying the alternating current supplied by the secondary winding 7 to provide direct current to the rotor winding 4.

[0033] As already explained in the overview section of the specification, the dissipation of heat generated during the rectification of the alternating current supplied via the secondary winding 7 can be a limiting factor for the power of the synchronous motor. Therefore, cooling of the electrical components 11-14 of the rectifier circuit 8 in the synchronous motor 1 is achieved by arranging the electrical components 11-14 within a cooling chamber 9, which is circulated by coolant 10 in at least one operating state of the synchronous motor 1, as in... Figure 1 As schematically shown by arrows 29-34. Therefore, components 11-14 are directly contacted and thus cooled by the flowing coolant 10 during operation of the synchronous motor 1.

[0034] exist Figure 1 In the example shown, the entire rectifier circuit 8, including the circuit board 15 carrying electrical components 11-14, is located in the cooling channel 19 of the cooling chamber 9, which extends along the axial direction of the synchronous motor 1 and thus parallel to the rotation axis 18 of the rotor 3. In this example, coolant 10 is supplied to the cooling channel 19 via a coolant inlet located on the left side outside the area shown in the figure and flows out of the synchronous motor via a coolant outlet 16, exemplarily shown as a flange. Except for the coolant inlet and outlet 16, the cooling channel 19 is closed in a liquid-tight manner in this example. However, in an alternative design, a portion of the coolant may also be radially directed outward, for example, in the region of the rotor winding 4, to cool the rotor winding and / or, after flowing into the air gap, to cool the stator winding 5.

[0035] Here, two semiconductor switches 20, 21 and two diodes 22, 23 are exemplarily shown as cooled electrical components 11-14. In this example, half-bridge rectification is implemented by the illustrated components, wherein the positive and negative arms of the half-bridge each include one of the semiconductor switches 20, 21 and one of the diodes 22, 23 connected in parallel therewith as freewheeling diodes. In the illustrated example, the semiconductor switches 20, 21 are controlled by a rotor-side control device 24. Here, the control device 24 can be configured to enable bidirectional energy transfer, that is, to also enable energy feedback from the secondary coil 6 to the primary coil 7, as discussed in the overview section of the specification.

[0036] Additionally, electrical components (not shown) of the rectifier circuit 8, such as those used to filter the rectified current to reduce current ripple, can be cooled by direct contact with the coolant 10, i.e., at least one capacitor and / or resistor.

[0037] In this example, the coolant 10 is an electrically insulating oil. Thus, the electrical connections (not shown) of components 11-14 and the conductor lines (not shown) of the circuit board 15 that contact the electrical connections can be directly adjacent to the cooling cavity 9 and in direct contact with the coolant 10 without the risk of short circuit.

[0038] In this example, the cooling cavity is also directly adjacent to the primary winding 6 and the secondary winding 7 to cool the windings used for inductive current transmission. For this purpose, in this example, a portion of the coolant (as shown by arrows 30 and 32) flows through an external annular channel 36, which is defined in its middle section by the surfaces of the primary winding 6 and the secondary winding 7. After flowing over this surface, the coolant 10 (as shown in...) Figure 1 As shown by arrows 33 and 34, the coolant is guided back into the cooling channel 19 via the perforation 38 of the inner ring 37 on the stator side supporting the rotor shaft and then through the cooling channel to the coolant outlet 16.

[0039] Figure 2 The above reference is shown as an example. Figure 1 The application of the separately excited synchronous motor 1 in the motor vehicle 25 is illustrated, wherein the synchronous motor 1 serves as the power unit of the motor vehicle 25 in this example. In addition to the synchronous motor 1 forming the cooling chamber 9, the motor vehicle 25 also includes other components of a closed coolant circulation loop 28, which are formed separately from the synchronous motor 1 in this example.

[0040] In this example, the circulation of coolant 10 is achieved by pump 26. For temperature regulation, coolant 10 is directed in this example through heat exchanger 27 of vehicle 25, which cools the coolant by exchanging heat with ambient air, which is directed through heat exchanger 27, for example by driving air and / or by means of an additional fan.

Claims

1. A separately excited synchronous motor having a rotor (3) rotatably supported on a stator (2), wherein, The rotor (3) has a rotor winding (4) for generating a rotor magnetic field, wherein the synchronous motor (1) has an inductive energy transfer circuit for supplying power to the rotor winding (4), wherein the energy transfer circuit includes a primary winding (6) on the stator side, a secondary winding (7) on the rotor side, and a rectifier circuit (8) for rectifying the alternating current supplied by the secondary winding (7) to supply power to the rotor winding (4), wherein the rotor (3) has a cooling cavity (9) through which coolant (10) flows in at least one operating state of the synchronous motor (1). Its features are, At least one electrical component (11-14) of the rectifier circuit (8) is arranged in the cooling cavity (9) such that the at least one electrical component is in direct contact with the coolant (10) at least in the operating state.

2. The separately excited synchronous motor according to claim 1, Its features are, The electrical component (11-14) or at least one of the electrical components (11-14) is a semiconductor switch (20, 21) or a diode (22, 23).

3. The separately excited synchronous motor according to claim 1 or 2, Its features are, The conductor lines of at least one electrical connection and / or the circuit board (15) carrying the corresponding component are in direct contact with the electrical connection and are directly adjacent to the cooling cavity (9) and thus in direct contact with the coolant (10) in operation.

4. The separately excited synchronous motor according to any one of the preceding claims, Its features are, The coolant (10) is oil and / or electrically insulating.

5. The separately excited synchronous motor according to any one of the preceding claims, Its features are, The cooling chamber (9) is designed as a cooling channel in at least one section in which at least one component (11-14) is arranged, the cooling channel being configured to guide coolant (10) from one or more coolant inlets to one or more coolant outlets (16), the cooling channel being liquid-sealed except for at least one coolant inlet and at least one coolant outlet (16).

6. The separately excited synchronous motor according to any one of the preceding claims, Its features are, The cooling cavity (9) is a cooling channel (19) or includes a cooling channel (19) that extends along the rotor shaft (17) in the axial direction of the synchronous motor (1).

7. The separately excited synchronous motor according to claim 6, Its features are, At least one electrical component (11-14) or the entire rectifier circuit (8) is arranged in a cooling channel (19) that extends along the rotor shaft (17) in the axial direction of the synchronous motor (1).

8. The separately excited synchronous motor according to any one of the preceding claims, Its features are, The corresponding sections defining the boundary surface of the cooling cavity (9) are formed by the secondary winding (7) and / or the primary winding (6) so that the secondary winding (7) and / or the primary winding (6) are cooled by the coolant (10) in operation.

9. The separately excited synchronous motor according to any one of the preceding claims, Its features are, The rectifier circuit (8) is configured to actively rectify the AC power supplied by the secondary winding (7) through a plurality of semiconductor switches, wherein the control device (24) of the control semiconductor switches (20, 21) of the synchronous motor (1) is configured to transfer power from the primary winding (6) to the secondary winding (7) in a first operating state of the synchronous motor (1) and to transfer power from the secondary winding (7) to the primary winding (6) in a second operating state of the synchronous motor (1).

10. A motor vehicle, Its features are, The motor vehicle includes a separately excited synchronous motor (1) according to any one of the preceding claims.

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