Rotor for separately excited synchronous machine and separately excited synchronous machine

Abstract

Rotor (12) for a separately excited synchronous machine (10), comprising a laminated core (18) arranged on a shaft (14) with a plurality of winding slots (20), wherein an excitation winding (22) is inserted in each winding slot (20), wherein the laminated core (18) has a recess (24) for generating a torque based on a reluctance force for the separately excited synchronous machine (10), characterized in that the rotor (12) further comprises a non-magnetic power transmission element (26), wherein the power transmission element (26) has a web (30) with two end-face flanges (32), wherein the power transmission element (26) is positively engaged with the respective flange (32) for power transmission in the circumferential direction in a respective partial opening (34) in the laminated core (18) on two opposite sides (28) of the recess (24), wherein the power transmission element (26) has a further bridge (42) perpendicular to the bridge (30),wherein the further web (42) abuts the web (30) at one end face and has a further flange (44) on an end face opposite the end face for fixing it to the shaft (16).

Description

[0001] The invention relates to a rotor for a separately excited synchronous machine. Furthermore, the invention relates to a separately excited synchronous machine with such a rotor.

[0002] The rotor of a separately excited synchronous machine comprises a laminated core mounted on a shaft. This core can be designed, for example, as a rotor yoke that encircles the shaft. Along its circumference, the core features a multitude of rotor poles, each of which can be configured as an armature, an inductor, or a pole shoe. These poles can correspond to a number of excitation windings arranged in winding slots. Thus, each winding slot can contain an excitation winding, and each excitation winding can be supplied with an electrical current from an external power source to generate an excitation field for the rotor. This electrical supply can be implemented, for example, using a slip ring and a carbon brush or, brushlessly, using a rotating diode rectifier.Such a separately excited synchronous machine can, for example, be used in a motor vehicle that is at least partially electrically powered.

[0003] To achieve low-loss and reliable operation of the separately excited synchronous machine, and in particular to increase its efficiency, it is known from the prior art to generate a reluctance-based torque in the rotor in addition to the excitation field generated by the excitation windings. For this purpose, the rotor's laminated core can have a recess (air gap) that impedes magnetic flux through the core, creating a pole gap between the rotor poles when the excitation windings are energized. Due to the recess in the laminated core, the rotor's mechanical strength, for example against centrifugal force, may be reduced compared to a core without a recess. The recess can be achieved, for example, by segmenting the laminated core.

[0004] The generic EP 2 991 194 A1 discloses a rotor for a current-excited synchronous machine.

[0005] For example, DE 10 2018 201 591 A1 discloses a rotor of an electric machine, which has a laminated core surrounding a shaft, comprising a first laminated core section extending in an axial direction and a second laminated core section extending in the axial direction.

[0006] Against this background, the object of the present invention is to provide an improved concept of a rotor of the type described above for a separately excited synchronous machine, which has high mechanical strength.

[0007] The problem is solved by the subject matter of the independent patent claims. Advantageous embodiments of the invention are described by the dependent patent claims, the following description, and the figures.

[0008] The improved concept is based on the understanding that while creating a recess in the lamination stack of a rotor for a separately excited synchronous machine can generate an additional torque on the rotor based on a reluctance force, the recess also mechanically weakens the rotor. This can, for example, limit or reduce the rotor speed, such as from 20,000 rpm to 15,000 rpm, thereby limiting the achievable efficiency of the separately excited synchronous machine. The improved concept counteracts this effect.

[0009] The improved design provides a rotor for a separately excited synchronous machine. Preferably, the rotor is of the type described above. The rotor comprises a laminated core arranged on a shaft with a plurality of winding slots. An excitation winding is placed in each winding slot. Furthermore, the laminated core has a recess for generating a reluctance-based torque for the separately excited synchronous machine. Thus, the rotor, which can also be referred to as a rotor, comprises the shaft, the laminated core with the winding slots and the recess, as well as the excitation winding of each winding slot.

[0010] The shaft can be made of or contain a metal (for example, steel). The shaft can be cylindrical and mounted on a rotating bearing. If it is necessary to reduce the shaft's weight, it can have a hollow body instead of a solid one, thus being designed as a hollow shaft. The shaft can protrude through a central opening in the laminated core. To provide a rotationally fixed connection between the shaft and the laminated core, the core can be heat-shrink-fitted to the shaft. Alternatively or additionally, the laminated core can be fixed to the shaft with a fastener. To reduce eddy current losses in the rotor, the laminated core can comprise several insulated laminations. The laminated core has several winding slots for arranging the respective excitation windings, as well as a recess.In particular, two of the winding slots can be arranged tangentially on two opposite sides of a respective rotor pole of the rotor.

[0011] In this context, a recess describes an opening in the laminated core, which may be at least partially bounded by the laminated core. Preferably, the recess is arranged at the respective rotor pole of the laminated core. In particular, the recess may be enclosed by the laminated core or by the laminated core and the shaft. The laminated core may, in particular, have several identical recesses. In a cross-section of the recess perpendicular to an axis of rotation of the shaft, for example, the length of the recess extending radially around the axis of rotation of the shaft may be greater than the width of the recess perpendicular to its length. Furthermore, the width of the recess may be variable, at least section by section, along its length and, for example, be maximal on one side of the recess adjacent to the shaft and minimal on the opposite side.In particular, the recess can extend along an axis of symmetry of the rotor pole. Alternatively or additionally, the rotor pole can have two recesses, which can be axially symmetric to each other. In particular, the two recesses can be arranged at least partially parallel to the axis of symmetry.

[0012] To increase or maintain the mechanical strength of the rotor, it is provided that the rotor also includes a non-magnetic power transmission element. The power transmission element has a web with two end flanges and is positively engaged with each flange in a partial opening in the lamination stack on two opposite sides of the recess. The power transmission element is thus a component designed to transmit a force and / or torque between the two sides of the recess. The power transmission element is made of a non-magnetic material, in particular a non-ferromagnetic material, so that any interaction of the power transmission element with a magnetic field generated by the excitation windings can be neglected in the design of the rotor and / or the separately excited synchronous machine.For example, the material of the power transmission element comprises a plastic (e.g., polypropylene), stainless steel, and / or aluminum. In particular, the material of the power transmission element exhibits high thermal resistance, high mechanical strength, and / or a permeability coefficient of less than 1. The power transmission element can be designed, in particular, as a three-legged profile (e.g., I-profile, U-profile, Z-profile) which, when installed in the rotor as intended, runs perpendicular to the axis of rotation of the shaft. The two opposing flanges can be connected to each other via the web and be parallel to each other. The web width perpendicular to a longitudinal direction of the web and parallel to the flanges can be, for example, between 10% and 90%, and in particular between 20% and 35%, of the respective flange width.To accommodate the force transmission element, two partial openings are provided on opposite sides of the recess. Each partial opening and each flange is designed to interlock during assembly. Thus, each partial opening can form a negative of its corresponding flange.

[0013] The force transmission element thus advantageously increases the mechanical strength of the rotor. This can, for example, prevent or limit relative movement within the laminated core caused by centrifugal force during rotor rotation, particularly in the area of ​​the recess. A rotor designed in this way can, for example, have a rotational speed of 18,000 rpm to 22,000 rpm, and the power output of the separately excited synchronous machine incorporating this rotor can be between 175 kW (kilowatts) and 225 kW. Furthermore, the two partial openings of the laminated core, into which the non-magnetic force transmission element is inserted, together with the recess in the laminated core, can increase the total reluctance force acting on the rotor and the resulting total torque.

[0014] The power transmission element is designed to have a further web perpendicular to the main web. This further web abuts the main web at one end and has a further flange on the opposite end for fixing it to the shaft. Thus, the power transmission element can be directly attached to the shaft by means of the further flange of the additional web. Advantageously, this connects the power transmission element to the laminated core on two sides via the two flanges and to the shaft via the additional flange. In particular, the additional web can be arranged radially to the axis of rotation of the shaft. Furthermore, the main web and the additional web can form a T-profile, with the main web projecting from the additional web on both sides.

[0015] An advantageous embodiment provides that each partial opening of the sheet metal stack is additionally enclosed by a boundary section of the web of the force transmission element adjacent to the respective flange, and that the web is arranged in the recess with a central section that differs from the two boundary sections. In other words, the central section of the web connects the two opposite sides of the recess. The boundary sections adjacent to the central section of the web on both sides, as well as the flanges arranged thereon, each project into the respective partial opening. Thus, the central section of the web can be enclosed on two opposite sides by the two boundary sections. The length ratio of the respective boundary section to the central section perpendicular to the two flanges can, for example, be between 1:1 and 1:10.The additional boundary sections of the web arranged in each partial opening allow the partial opening to be initially narrow on the respective side of the recess to accommodate the boundary section of the web, and only widen in a region of the respective flange. This advantageously makes it more difficult for the flanges to break out and minimizes any weakening of the sheet metal stack caused by the partial openings.

[0016] Another advantageous embodiment provides that the force transmission element additionally has a section adjacent to the web for completely filling the recess in the laminated core. Thus, the web can be at least partially enclosed, i.e., encased, by the adjacent section. This allows not only a portion of the recess occupied by the web of the force transmission element, but also a further portion of the recess to be filled by the section of the force transmission element adjacent to the web. In particular, the entire recess is filled by the force transmission element. Alternatively or additionally, the force transmission element can occupy at least part of the recess. For example, during rotor assembly, the web with the two flanges is first mounted, and then the adjacent section is cast.Alternatively, the recess can be filled in a single manufacturing step, for example by injecting an epoxy resin. Completely filling the recess can further improve the mechanical strength of the rotor.

[0017] An advantageous embodiment provides that the additional web has a first web width in a first web section adjacent to the web, tangential to the axis of rotation of the shaft, and a second web section adjacent to the additional flange has a second web width, reduced in size compared to the first web width, tangential to the axis of rotation of the shaft. In other words, the additional web comprises two different web widths tangential to the axis of rotation. In particular, a first web width can be essentially equal to a flange width of the additional flange. The first web width of the first web section, which is larger than the second web width, advantageously allows for a particularly large-area connection of the additional web to the web, so that the connection between the web and the additional web can be particularly robust.Due to the comparatively smaller web width of the second web section, the shaft opening for attaching the power transmission element can initially be narrow to accommodate the second web section and only widen in a region of the further flange. This advantageously makes it more difficult for the further flange to break out and minimizes mechanical weakening of the shaft.

[0018] Another advantageous embodiment provides that the outer contour of each flange of the power transmission element has only rounded edges to reduce stress concentrations. Thus, the surface of the power transmission element in the section encompassing both flanges is edgeless. At the outer contour, two abutting surface sections of the outer contour on each flange therefore do not form an edge. Rather, the outer contour of each flange includes at least one curved section, which can be concave and / or convex. This advantageously prevents or reduces stress concentrations at the respective flange during mechanical stress on the power transmission element. This also advantageously minimizes local stress concentrations, particularly at the transition from the underside to the top of the respective flange.Alternatively or additionally, another transition from the bridge to the respective flange can also have rounded edges.

[0019] Another advantageous embodiment provides that the power transmission element is a separate component. This allows the laminated core and the shaft to be designed and manufactured independently of the power transmission element. Furthermore, the power transmission element, designed as a separate component, is particularly easy to replace or exchange. In an unclaimed alternative, the power transmission element is formed integrally with the shaft. Thus, the shaft incorporates the power transmission element. This one-piece design also allows for a particularly reliable attachment of the laminated core to the shaft.

[0020] An unclaimed embodiment provides that, in a one-piece design of the power transmission element as part of the shaft, the shaft is designed as a hollow shaft and the power transmission element projects from a cylindrical surface of the shaft. Thus, the power transmission element is part of the hollow shaft and projects from a circumference of the shaft. In particular, the power transmission element can project radially from the shaft. The hollow shaft allows for a particularly lightweight rotor. Since the power transmission element projecting from the hollow shaft is already integrated into the shaft, separate manufacturing and subsequent attachment of the power transmission element are unnecessary.

[0021] Another advantageous embodiment provides that the web connects the two opposite sides of the recess perpendicularly. Thus, the web is arranged at right angles to both sides of the recess. This allows the force and / or torque to be transmitted particularly evenly by means of the force transmission element. The two sides of the recess are parallel to each other, so that the web is oriented parallel to a perpendicular distance between the two sides.

[0022] Furthermore, the improved concept provides a separately excited synchronous machine with a stator and a rotor. Preferably, the rotor is an embodiment of the rotor according to the improved concept.

[0023] The invention also includes further developments of the separately excited synchronous machine according to the invention, which have features already described in connection with the further developments of the rotor according to the invention, and vice versa. For this reason, the corresponding further developments of the separately excited synchronous machine according to the invention are not described again here.

[0024] The invention also includes combinations of the features of the described embodiments.

[0025] The following are exemplary embodiments of the invention described. This is illustrated by: Fig. 1 a schematic representation of a first exemplary embodiment of a separately excited synchronous machine according to the improved concept; Fig. 2 a schematic representation of a second exemplary embodiment of the separately excited synchronous machine according to the improved concept; Fig. 3 a schematic representation of a third exemplary embodiment of the separately excited synchronous machine according to the improved concept; Fig. 4 a schematic representation of a fourth exemplary embodiment of the separately excited synchronous machine according to the improved concept; and Fig. 5 a schematic representation of a fifth exemplary embodiment of the separately excited synchronous machine according to the improved concept.

[0026] The exemplary embodiments described below are preferred embodiments of the invention. In these exemplary embodiments, the described components each represent individual features of the invention, which can be considered independently of one another and each further develops the invention independently. Therefore, the disclosure is intended to include combinations of features of the embodiments other than those shown. Furthermore, the described embodiments can also be supplemented by further features of the invention already described.

[0027] In the figures, identical reference symbols denote functionally equivalent elements. For clarity, multiple functionally equivalent and, in particular, mirror-symmetrical elements are only marked with a corresponding reference symbol once.

[0028] The Fig. Figure 1 shows a section of a separately excited synchronous machine 10 in a first exemplary embodiment. The synchronous machine 10 comprises a rotor 12 and a stator 14.

[0029] The rotor 12 has a laminated core 18 arranged on a shaft 16, the shaft being rotatably mounted about an axis of rotation A. A rotor pole of the laminated core 18, as shown, comprises two winding slots 20, with an excitation winding 22 inserted in each winding slot 20. Furthermore, the laminated core 18 has a radial recess 24 for generating a torque based on a reluctance force for the separately excited synchronous machine 10.

[0030] To increase the mechanical strength of the rotor 12, a non-magnetic power transmission element 26 is provided, which is inserted perpendicularly on two opposite sides 28 of the recess 24. This is the element shown in the Fig. Figure 1 shows a force transmission element 26, a component separate from the shaft 16 and the laminated core 18. The force transmission element 26, shown enlarged, comprises a web 30 with two end flanges 32, wherein the force transmission element 26 is positively engaged with each flange 32 in a respective partial opening 34 in the laminated core 18. Each partial opening 34 of the laminated core 18 additionally encloses a boundary section 36 of the web 30 adjacent to the respective flange 32. The web 30 is arranged in the recess 24 with a central section 38 that differs from the two boundary sections 36. An outer contour 40 of the force transmission element 26 has rounded edges in the area of ​​the flanges 32 to reduce stress concentrations.

[0031] The Fig. 2 shows, with reference to the connection with the in the Fig. Figure 1 shows and describes a second exemplary embodiment of the separately excited synchronous machine 10. The power transmission element 26 in the region of the rotor pole shown has a further web 42 perpendicular to the web 30. The further web 42 abuts the web 30 at one end face and has a further flange 44 on an end face opposite this end face for fixing it to the shaft 16. A first web width 48a in a first web section 46a of the further web 42, which abuts the web 30 in a tangential direction to the axis of rotation A of the shaft 16, is less than a second web width 48b of a second web section 46b, which abuts the further flange 44 in a tangential direction to the axis of rotation A of the shaft 16.

[0032] The following Fig. 3, Fig. 4 and Fig. The figures 5 serve only to illustrate the invention and are therefore not part of the scope of protection.

[0033] The Fig. 3 shows, with reference to the information related to the information in the Fig. 1 to Fig. The components shown and described in section 2 represent a third exemplary embodiment of the separately excited synchronous machine 10. The power transmission element 26 in the area of ​​the rotor pole shown is formed in one piece with the shaft 16, which is designed as a hollow shaft 50, and projects from a lateral surface 52 of the shaft 16.

[0034] The Fig. 4 shows, with reference to the information related to the information in the Fig. 1 to Fig. The components shown and described in section 3 represent a fourth exemplary embodiment of the separately excited synchronous machine 10. The laminated core 18 of the rotor 12 has four recesses 24 in the region of the rotor pole shown, with each pair of recesses 24 being axially symmetrical to each other. Furthermore, the power transmission element 26 is arranged in each of two of the axially symmetrical recesses 24.

[0035] The Fig. 5 shows, with reference to the information related to the information in the Fig. 1 to Fig.The components shown and described in section 4 represent a fifth exemplary embodiment of the separately excited synchronous machine 10. The laminated core 18 of the rotor 12 has two axially symmetrical recesses 24 in the region of the rotor pole shown. In each of the two recesses 24, the respective power transmission element 26 completely fills each recess 24. For this purpose, each power transmission element 26 additionally comprises a section 54 adjacent to the web 30, as shown enlarged in section for one of the two recesses 24.

[0036] The improved concept is based on the understanding that the conventionally designed rotor 12 of the separately excited synchronous machine 10, i.e., without the recess 24, generally exhibits good mechanical strength, since an electrical steel sheet (laminate stack 18) of the rotor 12 is manufactured as a single unit, thus eliminating the need for segmentation of the electrical steel sheet. Furthermore, the absence of a permanent magnet allows the rotor 12 to exhibit good thermal overload capacity, enabling operation at high temperatures without increasing the risk of demagnetization. However, the torque of the separately excited synchronous machine 10 is limited by this design.

[0037] To increase the torque, the electrical steel sheet of the rotor 12 can have at least one hole (reluctance hole or recess 24) to generate a reluctance torque. However, this can reduce the mechanical strength of the rotor 12, which may result in the rotor 12 being too strong at high speeds to withstand the resulting centrifugal force, or may necessitate a reduction in the maximum speed of the rotor 12.

[0038] One objective of the improved concept is to reduce the strength-reducing weakening of the rotor 12 caused by the at least one reluctance hole. For this purpose, a puzzle-shaped positive locking element (force transmission element 26) made of a non-magnetizable material can be provided. This puzzle-shaped positive locking element can hold two segments of the lamination stack 18 of the rotor 12 together or, alternatively or additionally, fasten the lamination stack 18 to the shaft 16. The positive locking element and the corresponding partial openings 34 in the lamination stack 18 have a special contour, each of which can have a "neck" (web 30) and "head" (flange 32). The positive locking element can be designed to absorb a force (for example, a tensile force or a torsional force) in order to increase the overall strength of the rotor 12.With this positive-locking component, the rotor 12 can be designed for a comparatively higher centrifugal force, thereby enabling a higher maximum rotational speed of the rotor 12 and a higher maximum power output of the separately excited synchronous machine 10. This can, for example, involve a torque-to-volume ratio or a higher power density of the separately excited synchronous machine 10. Simultaneously, from a magnetic perspective, the positive-locking component can behave like air (permeability coefficient or relative permeability of 1) or as part of the at least one reluctance hole. Furthermore, the positive-locking component does not cause any "leakage flow" (compared to, for example, a sheet metal web) and can support the at least one reluctance hole when generating the reluctance torque.

[0039] The interlocking component can be made of, for example, a plastic (e.g., epoxy resin), a stainless steel (e.g., non-magnetic steel), and / or aluminum. Alternatively or additionally, the entire reluctance hole, or at least one of them, can be filled with the interlocking component, particularly the plastic. After the interlocking component has been manufactured (e.g., after the plastic has cured), the sheet metal stack 18 can be held together over a large area.

[0040] Overall, the examples show how a mechanically rigid structure of the rotor 12 for the separately excited synchronous machine 10 with reluctance torque can be provided by means of force-transmitting positive locking elements (force transmission elements 26).

Claims

[1] Rotor (12) for a separately excited synchronous machine (10), comprising a laminated core (18) arranged on a shaft (14) with a plurality of winding slots (20), wherein an excitation winding (22) is inserted in each winding slot (20), wherein the laminated core (18) has a recess (24) for generating a torque based on a reluctance force for the separately excited synchronous machine (10), characterized by, that the rotor (12) further comprises a non-magnetic power transmission element (26), wherein the power transmission element (26) has a web (30) with two end-face flanges (32), wherein the power transmission element (26) with the respective flange (32) is positively inserted for power transmission in the circumferential direction in a respective partial opening (34) in the lamination stack (18) on two opposite sides (28) of the recess (24), wherein the power transmission element (26) has a further web (42) perpendicular to the web (30), wherein the further web (42) adjoins the web (30) at one end face and has a further flange (44) for fixing to the shaft (16) at one end face opposite the end face. [2] Rotor (12) according to claim 1, wherein the respective partial opening (34) of the lamination stack (18) additionally includes a respective boundary section (36) of the web (30) of the power transmission element (26) adjacent to the respective flange (32), and the web (30) is arranged in the recess (24) with a central section (38) that differs from the two boundary sections (36). [3] Rotor (12) according to one of the preceding claims, wherein the power transmission element (26) additionally has a section (54) adjacent to the web (30) for completely filling the recess (24) of the lamination stack (18). [4] Rotor (12) according to one of the preceding claims, wherein the further web (42) has a first web section (46a) adjacent to the web (30) in a first web section (46a) in a tangential direction to an axis of rotation (A) of the shaft (16) and in a second web section (46b) adjacent to the further flange (44) a second web section (46b) reduced in the tangential direction to the axis of rotation (A) of the shaft (16). [5] Rotor (12) according to one of the preceding claims, wherein an outer contour (40) of each flange (32) of the power transmission element (26) has only rounded edges to reduce a stress peak. [6] Rotor (12) according to one of the preceding claims, wherein the power transmission element (26) is a separate component. [7] Rotor (12) according to one of the preceding claims, wherein the web (30) connects the two opposite sides (28) of the recess (24) perpendicularly to each other. [8] Externally excited synchronous machine (10) with a stator (14) and a rotor (12), wherein the rotor (12) is designed according to one of the preceding claims.

Images