Stator, method for producing a stator, and electric machine

Abstract

The invention relates to a stator (1) for an electric machine (2), said stator comprising an energizable stator winding (3), wherein a three-phase common-mode choke (4) is integrated in and / or on the stator (1).

Description

[0001] Stator, method for manufacturing a stator and electrical machine

[0002] The present invention relates to a stator for an electric machine, comprising an energizable stator winding. The invention further relates to a method for manufacturing a stator and an electric machine.

[0003] Electric drives powered by an inverter typically experience negative parasitic interactions that can impair both the performance and reliability of the drive systems. A significant parasitic interaction is increased electromagnetic interference. This interference can disrupt the functionality of electronic devices and systems in the vicinity of the drive system. Such interference can impair the proper functioning of the affected equipment and lead to significant operational problems.

[0004] Another significant problem caused by these parasitic effects is increased bearing currents. These currents arise from capacitive coupling and rapid switching operations in the inverter and can cause considerable damage to the bearings of electrical machines. The damage induced by increased bearing currents leads to premature bearing failures, which in turn shortens the service life of the entire drive systems and can result in unexpected and costly downtime in industrial applications.

[0005] These negative parasitic effects therefore pose a serious challenge that must be addressed through appropriate measures and components to ensure the reliability and efficiency of electric drives.

[0006] In industrial drives, particularly in production environments, drive systems with very long cable runs between the electric motor and inverter are frequently used. These systems are especially susceptible to increased EMC problems and bearing currents caused by the long cables. To address these issues, so-called motor chokes or higher-order sine wave filters are often employed. These components contain a current-compensated common-mode choke as their core element. These components must be designed for the defined rated current of the application, which makes them relatively large. In a production environment, this is generally not a problem.

[0007] The aforementioned parasitic problems, however, do not only occur in systems with long cables, but are also highly dependent on the design of the electrical machines and the hardware and software characteristics of the inverters. These problems are increasingly prevalent in mobile systems, such as high-voltage automotive drive systems or the latest generation of railway drives, which utilize extremely fast-switching wide-bandgap semiconductors. In these space-sensitive applications, standardized components for interference suppression cannot usually be used due to space constraints. A suitable three-phase common-mode choke can, in such cases, be as large as the electrical machine itself.

[0008] The object of the invention is therefore to provide a stator that eliminates or at least reduces radiated and conducted EMC problems and the associated malfunctions in the environment of an electric machine. Furthermore, the invention aims to provide a compact stator that can be used in both industrial and mobile drive systems. Finally, the invention aims to realize an optimized method for manufacturing a stator and an optimized electric machine.

[0009] This task is solved by a stator for an electric machine comprising a currentable stator winding, wherein a three-phase common-mode choke is integrated in and / or on the stator.

[0010] This allows for a more compact design of the electric machine, as no additional space is required for the separate housing of the choke. Furthermore, manufacturing can be made more efficient, since the same production technology used for winding the stator winding can also be applied to winding the three-phase common-mode choke. This leads to a reduction in production costs and a simplification of the manufacturing processes.

[0011] stator

[0012] For the purposes of this patent application, a stator is the stationary component of an electric machine, which typically comprises a current-carrying stator winding. Together with the rotor, the moving part of the machine, the stator forms the "heart" of the electric motor or generator. The stator's function is to guide and amplify the magnetic field generated by the stator winding. This is achieved by arranging the windings on a ferromagnetic core, which increases the magnetic conductivity. The interaction of the rotor and stator enables the electric machine to be driven by the mutual influence of their magnetic fields.

[0013] The stator assembly typically comprises the following components: the stator winding, the stator core, and the stator housing. The stator winding consists of conductors through which electric current flows. These conductors can be made of copper or aluminum and are wound, for example, onto a stator core. The stator core preferably consists of thin, insulated iron sheets that are laminated and stacked into a core. It serves to reduce eddy current losses and increase the machine's efficiency. The stator housing protects the internal components and provides structural support. It can be made of various materials such as aluminum, steel, or composite materials.

[0014] Advantageously, the stator can also include additional components such as an integrated cooling device to effectively dissipate the heat generated during operation. This is particularly important for high-performance applications or compact designs, such as those used in the automotive industry.

[0015] Special stator designs include those for axial flux machines, where the magnetic field runs parallel to the axis of rotation, and for radial flux machines, where the magnetic field runs radially to the axis of rotation.

[0016] The stator is specifically designed for use in an electric machine within the powertrain of a motor vehicle. The electric machine is specifically designed for use within the powertrain of a hybrid or fully electric motor vehicle. In particular, the electric machine is dimensioned to enable vehicle speeds greater than 50 km / h, preferably greater than 80 km / h, and especially greater than 100 km / h. The electric machine preferably has a power output greater than 30 kW, preferably greater than 50 kW, and especially greater than 70 kW. It is further preferred that the electric machine provides rotational speeds greater than 5,000 rpm, particularly preferably greater than 10,000 rpm, and most preferably greater than 12,500 rpm.

[0017] The stator according to the invention can be designed for use in a radial flux machine. A stator for a radial flux machine is typically cylindrical and generally consists of electrically insulated and layered electrical steel sheets stacked into laminations. Slots are cut into the electrical steel sheet around its circumference, running essentially parallel to the rotor shaft, to accommodate the stator winding or parts thereof. The stator slots preferably have a substantially U-shaped cross-sectional contour. Depending on the surface design, the slots can be closed with locking elements, such as locking wedges or covers, to prevent the stator winding from being removed.

[0018] There are several different winding technologies known for the stator of an electric machine.

[0019] For the purposes of this patent application, a stator winding is an arrangement of electrical conductors in the stator of an electric machine, designed to generate a magnetic field when current flows through it. This magnetic field interacts with the rotor, enabling the conversion of electrical energy into mechanical energy or vice versa. The function of the stator winding is therefore to generate a magnetic field that sets the rotor in motion. The controlled flow of current through the windings creates a magnetic field that is coupled into the ferromagnetic core of the stator. This field generates the necessary forces to drive the rotor, thus producing the desired mechanical motion or generating electricity.

[0020] The stator winding consists of several turns of conductive material mounted on or within a stator lamination stack. These conductors are advantageously made of copper. Alternatively, aluminum can be used as the conductive material to reduce costs. The turns are advantageously insulated to prevent short circuits between the individual conductors and to ensure electrical safety. For insulating the electrical conductors of a stator winding, mica paper, which may be reinforced with a fiberglass backing for mechanical reasons, can be wound in tape form around one or more electrical conductors of the stator winding, impregnated with a curing resin. It is also possible, in principle, to use a curable lacquer coating without mica paper to insulate an electrical conductor of a stator winding.

[0021] A stator winding typically comprises a plurality of electrically conductive conductors whose length is significantly greater than their diameter. An electrical conductor in a stator winding can, in principle, have any cross-sectional shape. Rectangular cross-sectional shapes are preferred because they allow for high packing densities and, consequently, high power densities. A stator winding made of copper is particularly preferred.

[0022] For the purposes of this patent application, stator cooling is a system or device for dissipating the heat generated in the stator of an electric machine during operation. The function of stator cooling is to effectively dissipate the heat generated by electrical losses in the stator.

[0023] The stator cooling system can comprise various components, including cooling channels, coolant pumps, and heat transfer elements. These components work together to remove heat from the hot spots of the stator and dissipate it to the environment or an external cooling system. The cooling channels are integrated into or attached to the stator and carry the coolant through it. The coolant circulating through the cooling channels absorbs the heat and transports it, for example, to a heat exchanger, where the heat is released.

[0024] Regarding the design of the stator cooling system, various constructions and materials are conceivable. One advantageous design is air cooling, in which air is passed through the stator to dissipate the heat. This method is simple and cost-effective, but is primarily suitable for machines with lower power requirements.

[0025] Another advantageous embodiment is water cooling, in which water is used as a coolant. This method offers higher cooling performance and is particularly suitable for high-performance machines. Water cooling can be implemented through integrated cooling channels in the stator or through external water jackets. In this case, the water is circulated by pumps, and the dissipated heat is transferred to an external heat exchanger.

[0026] An advanced form of stator cooling is oil cooling, which enables even more efficient heat dissipation. Oil cooling systems utilize the high thermal conductivity of oil and are particularly advantageous in compact, high-performance machines. The oil is pumped through special cooling channels or oil jackets within the stator, transporting the heat to an external cooling system. Combinations of these cooling methods can also be used to further increase efficiency. For example, water cooling can be used in conjunction with air cooling to optimize heat dissipation.

[0027] The coolant in the stator serves to dissipate heat as efficiently as possible from areas of the stator that heat up, thus preventing unwanted overheating of these areas. In addition to this primary function, the coolant also provides lubrication and corrosion protection for moving parts and the metal surfaces of the electric machine's cooling system. Furthermore, it can remove contaminants (such as abrasion particles), water, and air. The hydraulic fluid is preferably a liquid, and in particular, an oil. However, it is also conceivable to use aqueous hydraulic fluids, such as emulsions like water-glycol mixtures.

[0028] The three-phase common-mode choke can be connected to the stator cooling system by integrating it into the stator's cooling circuit. One option is to design the cooling channels so that they run through both the stator and the three-phase common-mode choke. This can be achieved by directly connecting the cooling channels to the choke windings, allowing the coolant to flow through the choke as well and absorb the heat generated.

[0029] Another option is to position the three-phase common-mode choke in close proximity to the stator's cooling channels, so that heat transfer occurs through thermal contact. This can be enhanced by using thermally conductive materials or thermal pastes to improve heat transfer between the choke and the cooling channels.

[0030] In liquid-cooled systems, the three-phase common-mode choke can be integrated into the cooling circuit by placing it in special cooling jackets or cooling chambers that are directly connected to the coolant flow. This directs the coolant precisely through the choke, enabling efficient heat dissipation.

[0031] For the purposes of this patent application, a three-phase common-mode choke is an electromagnetic component used to filter common-mode interference in three-phase electrical systems. It advantageously comprises a suitable ferrite ring with three identical windings that are magnetically coupled to one another. The winding orientation of the windings is such that the magnetic fields generated by the operating current cancel each other out in the ferrite ring, a phenomenon known as current compensation.

[0032] The function of the three-phase common-mode choke is, among other things, to filter out common-mode interference in the current signal and convert it into heat. This interference often arises from fast switching edges across parasitic capacitances and can negatively affect power electronics. The compensatory arrangement of the windings neutralizes the magnetic fields of the operating current, while the common-mode interference is effectively absorbed by the ferrite material and converted into heat. This contributes to improved signal quality and a reduction in electromagnetic interference.

[0033] The three-phase common-mode choke preferably comprises a ferrite ring and windings. The ferrite ring serves as a magnetic core and is made of a material suitable for high frequencies and strong magnetic fields. The three windings are wound evenly around the ferrite ring and arranged so that their magnetic fields cancel each other out during operation. The conductor cross-section of the windings is advantageously designed to match the magnitude of the operating current to ensure efficient current conduction.

[0034] Another advantageous embodiment involves integrating the three-phase common-mode choke into the cooling circuit of the stator or the electric machine. Here, the choke is either directly integrated into the stator's cooling channels or positioned in close proximity to them, allowing it to benefit from the existing cooling. This arrangement enables efficient heat dissipation, which is particularly advantageous at high currents and in compact designs. Additionally, the three-phase common-mode choke can be manufactured in various geometric shapes to better adapt to the specific requirements of the electric machine. For example, ring-shaped, toroidal, or flat designs can be implemented to allow for optimal integration into the stator.

[0035] Advantageous embodiments of the invention

[0036] According to an advantageous embodiment of the invention, the stator can be provided with fluidic stator cooling, and the three-phase common-mode choke is coupled to the stator cooling system, thus enabling it to be cooled during stator operation. Integrating the fluidic stator cooling system to cool the three-phase common-mode choke offers the advantage that the choke can be effectively cooled during operation. This is particularly important for higher power applications or compact automotive high-voltage systems where water- or oil-cooled motors / stators are used. By co-cooling the three-phase common-mode choke, the required installation space for the choke can be significantly reduced, which—in addition to the corresponding reduction in installation space—improves the overall efficiency of the electric machine and optimizes heat dissipation.

[0037] According to a further preferred embodiment of the invention, the stator may also comprise a stator housing, and the three-phase common-mode choke may be arranged at least partially, preferably completely, within the stator housing. Arranging the three-phase common-mode choke at least partially or completely within the stator housing has the advantage that the choke is optimally protected from external influences. This increases the service life and reliability of the choke, as it is less susceptible to mechanical damage or contamination. Furthermore, this arrangement contributes to the further compaction of the entire system, which is particularly advantageous in applications with limited installation space.

[0038] Furthermore, according to another advantageous embodiment of the invention, the three-phase common-mode choke can be arranged tangentially in and / or on the stator. According to a further particularly preferred embodiment of the invention, the three-phase common-mode choke can also be arranged radially in and / or on the stator.

[0039] For the purposes of this patent application, a tangential arrangement of the three-phase common-mode choke is a specific arrangement of the choke in or on the stator of an electrical machine, in which the three-phase common-mode choke is positioned tangentially to the circumferential direction of the stator. This arrangement enables a uniform distribution of the choke along the stator circumference and contributes to optimizing the spatial integration of the choke into the stator.

[0040] For the purposes of this patent application, a radial arrangement of the three-phase common-mode choke is a specific arrangement of the choke in or on the stator of an electric machine, in which the three-phase common-mode choke is positioned radially to the axis of the stator. This arrangement makes it possible to place the choke along the radial direction of the stator, which enables efficient integration and cooling.

[0041] Furthermore, the invention can also be further developed in such a way that the stator is configured for use in an axial flux machine or a radial flux machine.

[0042] The object of the invention can also be achieved by a method for manufacturing a stator of an electrical machine comprising the following steps:

[0043] - Provision of an initial winding plant;

[0044] - Provision of a stator;

[0045] - Provision of a first winding conductor;

[0046] - Provision of a second winding plant;

[0047] - Provision of a ferrite ring;

[0048] - Provision of a second winding conductor; a) Winding the stator with the first winding conductor to form a stator winding by the first winding system; b) Winding the ferrite ring with the second winding conductor to form a three-phase common-mode choke by the second winding system; c) Integrating the three-phase common-mode choke into and / or on the stator, wherein steps a) and b) can be carried out in any order.

[0049] It can also be advantageous to further develop the invention such that the first winding conductor and the second winding conductor are essentially identical. Using identical winding conductors for the stator winding and the three-phase common-mode choke offers the advantage of standardization and simplification of material procurement. This can lead to a reduction in inventory costs and increased cost efficiency. Furthermore, this facilitates the integration of the choke into the stator, as no different material properties need to be considered.

[0050] According to a further preferred embodiment of the invention, the first winding system and the second winding system can be identical. Using identical winding systems for the stator winding and the three-phase common-mode choke offers the advantage that no additional investments in different machines and tools are required. This reduces production costs and simplifies maintenance and personnel training, since only one uniform set of machines needs to be operated and maintained. If two winding systems are available, the winding of the stator and the three-phase common-mode choke can be carried out in parallel. In particular, it is also possible for the winding of the stator and the three-phase common-mode choke to be carried out sequentially on the same winding system.

[0051] Finally, the problem of the invention can also be solved by an electric machine comprising a stator according to any one of claims 1-6. The electric machine comprising a stator according to the preceding claims offers the advantage of combining the aforementioned benefits of integrating and cooling the three-phase common-mode choke, the flexible arrangement, and the optimized manufacturing technologies. This leads to improved performance, efficiency, and reliability of the electric machine, while simultaneously reducing production costs and optimizing the installation space.

[0052] The invention will now be explained in more detail with reference to figures, without limiting the general concept of the invention.

[0053] It shows:

[0054] Figure 1 shows an electrical circuit diagram of the stator,

[0055] Figure 2 shows a stator with a three-phase common-mode choke in a tangential arrangement,

[0056] Figure 3 shows a stator with a three-phase common-mode choke in radial arrangement.

[0057] Figure 1 shows a stator 1 for an electric machine 2, comprising a current-carrying stator winding 3, wherein a three-phase common-mode choke 4 connected upstream of the stator winding 3 is integrated in and / or on the stator 1. "Integrated" means that the three-phase common-mode choke 4 is either built into the stator 1 or attached to it.

[0058] This integration can be achieved in various ways. One possibility is to house the three-phase common-mode choke 4 completely or partially within the stator 1. In this case, the three-phase common-mode choke 4 is positioned in specially designed chambers or spaces within the stator 1, which allows for a compact design.

[0059] Another option is to attach the three-phase common-mode choke 4 to the outer surface of the stator 1. This arrangement simplifies maintenance and allows quick access to the three-phase common-mode choke 4 without having to disassemble the entire stator 1.

[0060] Furthermore, the three-phase common-mode choke 4 can be integrated into the cooling circuit of the stator 1. In this embodiment, the cooling channels of the stator 1 also surround or flow through the three-phase common-mode choke 4, thus ensuring efficient heat dissipation.

[0061] Integrating the three-phase common-mode choke 4 into and / or onto the stator 1 allows for efficient use of installation space and a more compact overall design of the electric machine. This integration also contributes to reducing electromagnetic interference and improves the electrical and thermal performance of the machine.

[0062] Figure 1 further shows that the stator 1 has a fluidic stator cooling system 5 and that the three-phase common-mode choke 4 is coupled to the stator cooling system 5, thus allowing it to be cooled during operation of the stator 1. In the example shown, the stator cooling system 5 is designed as a closed cooling circuit with a coolant pump 11 and a heat exchanger 9. A cooling oil is used as the coolant.

[0063] The stator winding 3 is configured in a star connection and is energized by a three-phase current via the motor terminals 10. In this configuration, the three winding strands of the stator winding 3 are connected to each other in a star configuration, with one end of each winding strand being joined at a common neutral point. The other ends of the winding strands are connected to the motor terminals 10, to which the three-phase current is applied. This arrangement enables a uniform distribution of current and voltage across the winding strands, resulting in efficient generation of the magnetic field in the stator 1.

[0064] Alternatively, the stator winding 3 can also be configured in a delta connection. In this configuration, the winding strands are connected such that the end of one winding strand is connected to the beginning of the next, forming a closed loop or triangle. The motor terminals 10 are located at the connection points between the winding strands, thereby supplying the three-phase current to the system. This type of connection allows for a higher voltage to be applied to the winding strands and can be advantageous in certain applications where higher motor power output is required.

[0065] Figure 1 also clearly shows that the stator 1 comprises a stator housing 6 and the three-phase common-mode choke 4 is arranged completely inside the stator housing 6.

[0066] In Figure 2, the three-phase common-mode choke 4 is arranged tangentially 7 in and / or on the stator 1, while in Figure 3 it is arranged radially 8 in and / or on the stator 1. Due to its design, the tangential arrangement 7 is particularly suitable for axial flux machines. The radial arrangement 8, on the other hand, is preferred for radial flux machines.

[0067] A method for manufacturing the stator 1 of the electric machine 2 may comprise the following steps: First, a first winding unit, a stator 1, a first winding conductor, a second winding unit, a ferrite ring, and a second winding conductor are provided. Then, the stator 1 is wound with the first winding conductor to form a stator winding 3 by the first winding unit, and the ferrite ring is wound with the second winding conductor to form a three-phase common-mode choke 4 by the second winding unit. Finally, the three-phase common-mode choke 4 is integrated into and / or onto the stator 1.

[0068] The invention is not limited to the embodiments illustrated in the figures. The foregoing description is therefore not to be considered limiting, but rather explanatory. The following claims are to be understood as meaning that a named feature is present in at least one embodiment of the invention. This does not preclude the presence of further features. Where the claims and the foregoing description define 'first' and 'second' features, this designation serves to distinguish between two similar features without establishing any hierarchy.

[0069] List of reference symbols: Stator, electric machine, stator winding, common-mode choke, stator cooling, stator housing, tangential arrangement, radial arrangement, heat exchanger, motor terminals, coolant pump

Claims

Claims 1. Stator (1 ) for an electric machine (2), comprising a currentable stator winding (3) characterized in that a three-phase common-mode choke (4) is integrated in and / or on the stator (1 ).

2. Stator (1 ) according to claim 1 , characterized in that the stator (1 ) has a fluidic stator cooling (5) and the three-phase common-mode choke (4) is coupled to the stator cooling (5), and is thereby coolable during operation of the stator (1 ).

3. Stator (1 ) according to claim 1 or 2, characterized in that the stator (1 ) comprises a stator housing (6) and the three-phase common-mode choke (4) is arranged at least partially, preferably completely, within the stator housing (6).

4. Stator (1 ) according to one of the preceding claims, characterized in that the three-phase common-mode choke (4) is arranged in a tangential arrangement (7) in and / or on the stator (1 ).

5. Stator (1 ) according to one of the preceding claims 1-4, characterized in that the three-phase common-mode choke (4) is arranged in a radial arrangement (8) in and / or on the stator (1 ).

6. Stator (1) according to one of the preceding claims, characterized in that the stator (1 ) is configured for use in an axial flux machine or a radial flux machine.

7. Method for manufacturing a stator (1 ) of an electrical machine (2) comprising the following steps: - Provision of an initial winding plant; - Provision of a stator (1 ); - Provision of a first winding conductor; - Provision of a second winding plant; - Provision of a ferrite ring; - Provision of a second winding conductor; a) Winding of the stator (1 ) with the first winding conductor to form a stator winding by the first winding system; b) Winding of the ferrite ring with the second winding conductor to form a three-phase common-mode choke (4) by the second winding system; c) Integrating the three-phase common-mode choke (4) into and / or on the stator (1 ), wherein steps a),b) can be carried out in any order.

8. Method according to claim 7, characterized in that the first winding conductor and the second winding conductor are essentially identical.

9. Method according to claim 7 or 8, characterized in that the first winding system and the second winding system are identical.

10. Electric machine (2) comprising a stator (1) according to one of the claims

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