Electric machine, method for its operation and motor vehicle with electric machine

Abstract

An electrical machine with at least one winding (106, 202, 203) that is functionally separate from the electrical machine, wherein the electrical machine comprises a stator (103) and the at least one winding (106, 202, 203) is arranged at least partially in at least one recess (201) of the stator (103) and / or in at least one yoke of the stator (103) and / or on the outside of the stator (103), wherein the at least one winding (106, 202, 203) comprises at least one partial transformer, wherein the partial transformers are grouped together, the number of groups corresponding to the number of phases of the electrical machine, wherein in particular a power flow for each group is separately controllable, characterized in that the power flow of the groups is controllable in such a way that a predetermined saturation value of the magnetic circuit of the electrical machine is maintained.

Description

[0001] The invention relates to an electric machine, a method for operating the electric machine and a motor vehicle comprising at least one electric machine.

[0002] In automotive engineering, electrical consumers are increasingly used due to their good controllability. This correspondingly increases the electrical power required in a motor vehicle.

[0003] To efficiently meet the demand for electrical power, a vehicle electrical system with a voltage greater than 40 V is often used. On the other hand, electrical safety and information electronics components can be efficiently implemented with a lower supply voltage (e.g., less than 5 V).

[0004] For this reason, multi-voltage electrical systems are used, the voltage levels of which are energetically linked. For example, there are vehicles with a 12 V / 42 V or a 12 V / 288 V electrical system.

[0005] It is known to link the on-board networks of different voltages by means of a DC / DC converter.

[0006] Known systems have the problem that an additional electrically isolating magnetic transformer is interposed to safely separate electrical potentials between the on-board power supplies of different voltages.

[0007] Another disadvantage is that when separate generators are used, multi-winding systems are required for the different Voltage ranges are provided, thus minimizing the utilization of the material used for the overall system (total power density).

[0008] Isolation transformers also have the disadvantage that the materials required for guiding the magnetic flux are limited in their technically usable properties, and the components built upon them are bulky, heavy, complex, and difficult to integrate into a vehicle. This also applies to circuits in which the transformer is designed as a converter and has its own electronic control.

[0009] Known approaches result in high system complexity, high system costs, large installation space requirements, and additional weight. For example, a bidirectional electrically isolating converter with a volume of at least 5 liters and a weight greater than 10 kg is required for an on-board power supply of 4 kW. Furthermore, corresponding effort is required for cooling and monitoring the converter.

[0010] The object of the invention is to avoid the aforementioned disadvantages and in particular to provide an efficient way of combining an electric machine and a transformer.

[0011] This problem is solved according to the features of the independent claims. Further developments of the invention also result from the dependent claims.

[0012] To solve the problem, an electrical machine with at least one winding is specified, wherein the at least one winding is functionally separated from the electrical machine.

[0013] In particular, a plurality of windings can be provided, which represent at least one coil and / or at least one transformer.

[0014] The functional separation of the at least one winding from the electrical machine can include electrical separation. In particular, a transformer function of the at least one winding is logically and / or functionally separated from an electromotive function of the electrical machine.

[0015] The term "electric machine" is understood to mean, in particular, any electric machine that uses an electromagnetic operating principle. In particular, the electric machine can comprise an electric motor and / or a generator.

[0016] This approach makes it possible to use components of the electric machine largely independently and / or in addition to the electromotive function of the electric machine itself. For example, a motor core, an iron sheet, or a stator of an electric motor can be used, in combination with the at least one winding, to form, for example, a coil or a transformer. This allows for efficient use of the installation space required by the electric machine.

[0017] A further development is that the at least one winding is part of at least one transformer and / or at least one coil.

[0018] In particular, the coil can be a choke and the transformer can be an isolation transformer.

[0019] Another further development is that the at least one transformer for energy transfer It can be used between different power supplies.

[0020] In particular, the power supplies can be on-board power supplies of different voltages of a motor vehicle.

[0021] Furthermore, it is a further development that the at least one winding is guided at least partially in, on or through an at least partially unused area of ​​an electrical steel sheet or motor iron of the electrical machine.

[0022] It is also a further development that the electrical machine comprises a stator and that the at least one winding is arranged at least partially in at least one recess of the stator and / or in at least one yoke of the stator and / or on the outside of the stator.

[0023] In particular, the recess may be a groove, an opening or a cutout.

[0024] It is a further development that part of the at least one winding is arranged in the recess of the stator and part of the winding is arranged on the outside of the stator.

[0025] As part of a further development, the at least one recess and / or the stator windings of a partial transformer are included.

[0026] In particular, the at least one winding comprises windings of at least one partial transformer.

[0027] A further development consists in several partial transformers being connected in parallel and / or in series, in particular in such a way that a transformation ratio can be set.

[0028] Furthermore, the turns ratio can also be adjusted by the number of turns of the windings of the respective sub-transformer.

[0029] One embodiment is that the partial transformers are grouped together, wherein the number of groups corresponds to a number of phases of the electrical machine, wherein in particular a power flow for each group can be controlled separately.

[0030] In particular, one sub-transformer can be provided per group. For example, the groups can each comprise the same number of sub-transformers.

[0031] This makes it possible to use only those areas of the yoke for transformer power transmission that are not already permeated by a magnetic flux due to an electromotive torque.

[0032] An alternative embodiment consists in the power flow of the groups being controllable in such a way that a predetermined saturation value of the magnetic circuit of the electric machine is maintained.

[0033] Another embodiment is that a control is provided for the at least one winding, in particular for at least one transformer comprising the at least one winding, wherein the control is adjustable depending on at least one of the following parameters: – an impedance; – a necessary or predetermined control quality; – a preferred energy flow direction.

[0034] It is also a design feature that a control device is provided for each at least one transformer.

[0035] Another embodiment is that the at least one transformer can be controlled in such a way that the saturation of the magnetic circuit through an interaction of electromechanical and transformer-based energy transfer does not exceed a predetermined value.

[0036] A further development consists in the fact that a predetermined transmission power for at least one transformer can be set based on an operating point of the electrical machine.

[0037] An additional embodiment is that the control system suspends the control of the at least one transformer if the magnetic circuit is heavily or completely used by the electric machine, and that the control system activates the at least one transformer if the electric machine is only slightly or not at all used.

[0038] The electric machine can be used, in particular, as a motor or as a generator. High or low usage of the electric machine can be determined by means of a threshold comparison. Thus, high usage can be detected when a predetermined upper threshold is exceeded, and low usage can be detected when a correspondingly predetermined lower threshold is not reached. This enables the activation and / or partial activation of the transformer function or the activation of the control system provided for the at least one transformer.

[0039] It should be noted that overlapping operating modes are also possible, e.g. a partial, weakened or time-limited perception of the transformer task in an operating range of the electrical machine between its possible operating states (off, full load).

[0040] In particular, the operating points of the transformer task and / or the electromotive task can be continuously adjustable.

[0041] The problem is also solved by means of a method for operating the electrical machine described herein.

[0042] Furthermore, the problem is solved by a motor vehicle comprising at least one electric machine according to the present description.

[0043] Exemplary embodiments of the invention are shown and explained below with reference to the drawings.

[0044] They show:

[0045] Fig. 1 shows two sectional drawings through an electrical machine comprising a stator and a rotor, wherein the stator has at least partially transformer windings;

[0046] Fig. 2 shows a sheet metal section through a stator comprising recesses for receiving windings, e.g., of a transformer for energy transmission between different vehicle electrical systems;

[0047] Fig. 3 shows a sheet metal section through a stator comprising recesses for receiving windings, wherein part of the windings are arranged on the outside of the stator;

[0048] Fig. 4 shows a sheet metal section through a stator comprising recesses for receiving windings, wherein the recesses are arranged offset from each other;

[0049] Fig. 5 shows a sheet metal section through a stator, wherein windings are arranged in recesses of the stator and essentially the yoke cross-section of the stator is used as a transformer;

[0050] Fig. 6 shows an arrangement for an exemplary grouping of windings of a 3-phase electric machine in star connection;

[0051] Fig. 7 shows an arrangement for an exemplary grouping of windings of a 3-phase electric machine in star connection, wherein a star point of the electric machine is also used for the control of the transformers.

[0052] The approach presented here enables safe electrical separation of vehicle electrical system areas (same or different voltages) by efficiently utilizing a magnetic circuit of electric motors or generators present in a vehicle.

[0053] Thus, components that are used at least temporarily and / or not completely for electromechanical energy conversion of the electric machine can be used for transformer-based energy transfer between different on-board power supplies.

[0054] For example, a conventional starter is switched off after the combustion engine has started and remains unused in the vehicle. Furthermore, due to the electromotive principle, only parts of the magnetic circuit are used to generate force in order to produce mechanical motion, while other parts of the same magnetic circuit remain unused. For example, in a known rotating field machine, areas of high and low magnetic load alternate in spatial and temporal sequence.

[0055] The solution approach presented here makes it possible to use the areas of low magnetic load for the transformer coupling of the various on-board network areas in such a way that the electromechanical energy conversion in the electric machine is not adversely affected and, in particular, neither the power density required for the actual task of the electric machine is reduced nor are there any energetically adverse couplings between the electromechanical task and the transformer task of the electric machine during operation.

[0056] This solution is independent of an electromagnetic operating principle of the machine, i.e. the solution is applicable to all known machine types (principle of field generation, winding structure, number of phases, pole pitch / number, stator / rotor arrangement, linear / rotary actuator etc.). Winding structure:

[0057] Fig. 1 shows two sections 101 and 102 through an electric machine comprising a stator 103 and a rotor 104, wherein an air gap 107 is provided between the stator 103 and the rotor 104. A rotation axis 105 and a winding head 108 of the electric machine are also shown.

[0058] The stator 103 additionally has a wick The transformer winding 106 (e.g., a transformer winding) can be used, for example, for power transfer between power supplies in an on-board electrical system. The transformer winding 106 is functionally separate from the electric machine; that is, it does not contribute to the electromotive task of the electric machine. Rather, it efficiently utilizes the fact that the stator has electrical steel sheets that can be used for further windings and that the electric machine does not have to perform its electromotive task 100%, at least temporarily (standstill, starter function, etc.).

[0059] In embodiment 101, the transformer winding 106 is partially arranged outside the stator 103, while in embodiment 102 the transformer winding 106 is guided through the stator 103 in both directions.

[0060] Preferably, the transformer winding 106 is arranged at least partially in a stator yoke. It should be noted that a plurality of transformer windings can be provided. In Fig. 1, a single winding is shown symbolically.

[0061] Preferably, at least one (additional) recess is provided in an electrical steel sheet in areas of a stator yoke of an electrical machine, in which the additional windings for a transformer are arranged.

[0062] Fig. 2 shows by way of example a sheet metal section through a stator comprising recesses 201 for receiving windings e.g. of a transformer for energy transfer between different on-board networks of a vehicle.

[0063] The recess 201 includes, by way of example, windings 202 , 203 in different directions.

[0064] By way of example, the transformer windings 202 are placed in the yoke sections adjacent to the teeth of the usual motor windings and the windings of the transformer are designed as multi-chamber windings, in particular with high-quality electrical insulation.

[0065] For example, each area of ​​the yoke that has a recess forms a partial transformer.

[0066] By connecting the windings of the sub-transformers in series and / or parallel, it is possible to adapt the turns ratio to different voltages in the various vehicle electrical system sections. Furthermore, the turns ratio can be predetermined by the number of turns within the sub-transformers.

[0067] A mixed series-parallel connection of the windings or the partial transformers is also possible. Furthermore, it is possible to provide at least some recesses with only turns of one winding, thereby increasing the leakage inductance of the transformer or the (partial) transformers, or to form one or more chokes (e.g., for use in a boost converter or a buck converter). Transformers with only one winding system (e.g., autotransformers) as well as transformers with taps and transformers with a plurality of galvanically isolated windings can also be designed. In addition, it is an alternative to connect different sections of the electrical system with partial transformers in multi-part electrical networks.

[0068] Another approach is to connect the individual sub-transformers into groups such that the number of groups corresponds to the number of phases of the electric motor and a power flow for each transformer group can be controlled separately. This makes it possible to use only those areas of the yoke for transformer power transmission that are not already permeated by a magnetic flux due to an electromotive torque. Accordingly, the respective output of the sub-transformers can be limited in all areas such that a predetermined saturation value of the magnetic circuit is not exceeded in any area and at the same time the intended transformer power can be used efficiently (e.g., to the maximum).

[0069] Optionally, a recess in the yoke area can be omitted, and instead, the stator of the electric machine can be used as the magnetic circuit of the transformer. According to the embodiment shown in Fig. 3, the individual windings are arranged around the yoke such that part of the winding is located in the slot and the other part of the winding is on the outside of the stator. Thus, the stator iron is used as a toroidal transformer. The winding system can again be configured as an inductor, galvanically isolated, as an autotransformer, and / or as an isolation transformer, etc.

[0070] By appropriately arranging the individual windings, the connection with a main energy flow of the electric machine can be influenced in such a way that no power is drawn from this main energy flow, since the entire electromechanically generated magnetic flux in the circumferential direction becomes zero, which also applies to partial regions of the machine circumference in machines with more than one pole pair. Likewise, an energetic interaction with the to achieve the main energy flow of the machine (e.g., by asymmetrical segmentation of the additional transformer windings in relation to the known winding system of the electric motor).

[0071] By way of example, Fig. 4 shows a sheet metal section through a stator comprising recesses for receiving windings, wherein the recesses are arranged offset from one another. Another example is shown in Fig. 5 with a sheet metal section through a stator, wherein windings are arranged in recesses of the stator and essentially the yoke cross-section of the stator is used as a transformer.

[0072] Another embodiment provides to use such areas of a motor iron for the transformer that previously had no significance for guiding a magnetic flux and are, for example, only present for design reasons (e.g., adapting the outer contour of the motor to predetermined geometries).

[0073] For example, in the case of right-angled outer contours of the motor iron, the outer corners can be provided for the insertion of transformer windings.

[0074] Furthermore, the aforementioned winding arrangements can be combined with each other. Steering:

[0075] Control of the transformer windings can be carried out depending on their impedance, on a necessary or predetermined control quality and / or on a preferred energy flow direction, in particular by means of controlled circuits on the primary and secondary side of the transformers as well as by means of mechanical commutation devices and / or simple rectifiers.

[0076] It is also possible to equip the various sub-transformers with their own control devices. Known control devices for transformers, transducers, or DC-DC converters can be used for this purpose. Preferably, the control of the transformers is integrated spatially, technologically, and functionally into the control of the electric motor.

[0077] For example, the individual windings of the partial transformers can be connected to a star point of the electric machine. This can significantly reduce the complexity of the control system.

[0078] A control strategy takes into account, in particular, the different capabilities of the individual vehicle electrical system sections and / or possibilities of electromechanical energy conversion, e.g., storing energy over a period of time and covering load fluctuations from the energy storage devices. Due to the dynamic nature of electromechanical energy conversion with comparatively low base load requirements, electromechanical energy conversion is preferably prioritized over the transformer-based use of the magnetic circuit.

[0079] When high demands are placed on the continuity of energy transfer between the various vehicle electrical system sections, the sub-transformers can be controlled section by section in such a way that the local saturation of the magnetic circuit due to the interaction of electromechanical and transformer-based energy transfer does not exceed a predetermined value (e.g., a maximum value). For this purpose, for example, the saturation characteristic of the electric machine is stored in the control software, and the permissible transfer power of each sub-transformer is determined from a current operating point of the electric machine (e.g., using rotor angle, phase currents, pulse pattern) and set using the respective pulse patterns of the transformer controls.

[0080] If the requirements for the continuity of energy transfer between the various vehicle electrical system sections are low, the division of the transformer into sub-transformers and their at least partially independent control can be dispensed with. In this way, the total power to be transferred by the transformer can be efficiently adapted to the electromechanical utilization of the machine. For example, the transformer-based energy transfer is suspended if the magnetic circuit is already highly or completely utilized by the motor and / or generator load of the electric machine. Conversely, the transfer power can be maximized if the electric machine operates with low torque or not at all as a motor and / or generator, but at the same time energy levels of certain vehicle electrical system sections need to be balanced.Between these two extremes of the control, the operating points can be continuously adjusted.

[0081] Fig. 6 shows an arrangement for an exemplary grouping of windings of a 3-phase electric machine in star connection.

[0082] The electric machine 600 comprises transformers 601 to 603, each of which is separate from the function of the electric machine 600 and connected to an associated control unit 604 to 606 and provides a first voltage level 607 and a second voltage level 608.

[0083] Winding strands 609 to 611 of the electric machine 600 are connected on one side to a motor control 612 and on the other side to a star point 613 of the electric machine 600.

[0084] Fig. 7 shows an arrangement for an exemplary grouping of windings of a 3-phase electric machine in star connection, wherein a star point of the electric machine is used for the control of the transformers.

[0085] The electric machine 700 comprises transformers 701 to 703, each of which is separate from the function of the electric machine 700 and is connected to an associated control unit 704 to 706 or to a star point 713 of the electric machine. The control units 704 to 706 are connected to a first voltage level 707 and to a second voltage level 708.

[0086] Winding strands 709 to 711 of the electric machine 700 are connected on one side to a motor control 712 and on the other side to the star point 713. Further advantages:

[0087] The approach presented here minimizes the effort required to couple different voltage levels, especially in the electrical system of a motor vehicle.

[0088] Thus, no additional magnetic elements are required. Different functions can be combined in one component using a common technology basis. Advantageously, the connection technology requires only reduced effort. Likewise, there are reduced requirements for the design effort involved in wiring, insulation, cooling, and housing.

[0089] The reduction in complexity is accompanied by savings in system costs, installation space, and weight. Compared to a conventional DC / DC converter with the same functionality connected between the voltage levels, the complexity, installation space, weight, and costs are reduced by approximately 80%.

Claims

[1] Electrical machine with at least one winding (106 , 202 , 203 ) which is functionally separate from the electrical machine. [2] Electrical machine according to claim 1, wherein the at least one winding (106 , 202 , 203 ) is part of at least one transformer (601 ,602 , 603 ) and / or at least one coil. [3] Electrical machine according to claim 2, wherein the at least one transformer (601 , 602 , 603 ) can be used for energy transfer between different power supplies. [4] Electric machine according to one of the preceding claims, wherein the at least one winding (106 , 202 , 203 ) is guided at least partially in, on or through an at least partially unused area of ​​an electrical steel or motor iron of the electric machine. [5] Electric machine according to any one of the preceding claims, – in which the electric machine includes a stator (103 ) and – wherein the at least one winding (106 , 202 , 203 ) is arranged at least partially in at least one recess (201 ) of the stator (103 ) and / or in at least one yoke of the stator (103 ) and / or on the outside of the stator (103 ). [6] Electric machine according to claim 5, in which part of the at least one winding (106 , 202 , 203 ) is arranged in the at least one recess (201 ) of the stator (103 ) and part of the winding (106 , 202 , 203 ) is arranged on the outside of the stator (103 ). [7] Electrical machine according to one of claims 5 or 6, wherein the at least one winding (106 , 202 , 203 ) comprises at least one partial transformer. [8] Electrical machine according to claim 7, in which several partial transformers are connected in parallel and / or in series, in particular such that a transformation ratio is adjustable. [9] Electrical machine according to one of claims 7 or 8, wherein the partial transformers are grouped together, the number of groups corresponding to the number of phases of the electrical machine, wherein in particular a power flow for each group is separately controllable. [10] Electric machine according to claim 9, wherein the power flow of the groups can be controlled in such a way that a predetermined saturation value of the magnetic circuit of the electric machine is maintained. [11] Electric machine according to one of the preceding claims, with a control for the at least one winding, in particular for at least one transformer comprising the at least one winding, wherein the control is adjustable depending on at least one of the following parameters: – An impedance; – a necessary or predetermined level of regulatory quality; – a preferred direction of energy flow. [12] Electrical machine according to claim 11, wherein a control device is provided for each at least one transformer. [13] Electrical machine according to one of claims 11 or 12, in which the at least one transformer can be controlled in such a way that the saturation of the magnetic circuit by an interaction of electromechanical and transformer-based energy transfer does not exceed a predetermined value. [14] Electrical machine according to claim 13, wherein a predetermined transmission power for the at least one transformer can be set based on an operating point of the electrical machine. [15] Electric machine according to any one of claims 11 to 14, – in which the control system suspends the control of at least one transformer if the magnetic circuit is heavily or completely utilized by the electrical machine; – where the control system activates at least one transformer if the electrical machine operates with low torque or not at all as a motor and / or generator. [16] Method for operating the electric machine according to any one of the preceding claims. [17] Motor vehicle comprising at least one electric machine according to any one of claims 1 to 15.

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