Distributed double Litz wire winding in an open slot

Abstract

An electric machine having a stator with a plurality of open slots accommodating two layers of distributed winding with conductors transposed in the end winding regions, the conductors being Litz wire conductors, and the end winding portions of the conductors not twisted or rotated about the axis of the conductors.

Description

Technical Field

[0001] The present invention relates to an electromechanical machine (motor / generator) having a two-layer distributed winding according to the preamble of claim 1.

[0002] More specifically, it relates to an electromechanical machine having a two-layer distributed winding arranged in an open slot.

Background Art

[0003] When designing an electromechanical machine, it is desirable to have a slot design such that the electrical losses in the conductors are as low as possible, and at the same time, the heat conduction from all the conductors in the slot to the stator core has several paths with low thermal resistance. These two goals often conflict with each other.

[0004] This conflict is even stronger in electromechanical machines with open slots operating at frequencies higher than 50 Hz. This is because the high-frequency pulsed magnetic field passing through the slot opening causes additional losses in the conductors.

[0005] To reduce the thermal resistance to the heat flow from the slot, especially the central part of the slot area, it is necessary to make the slot-fill factor (SFF) of the winding as high as possible. This means occupying as much of the slot area as possible with copper or other conductive materials and minimizing the area occupied by the insulator. Copper is an excellent heat conductor but has poor insulation properties.

[0006] A conventional method for achieving high slot filling densities (SFF) is to use solid conductors with a rectangular cross-section. This allows for SFF of 80-85%. However, a challenge with solid conductors is the non-uniform current distribution within individual conductors and within the slot region, especially when supplying high frequencies to the machine and particularly due to pulsed magnetic fields at the slot openings. This results in higher electrical losses at low frequencies and compared to those common in machines with closed or partially closed slots. The reasons for the non-uniform current distribution are the well-known skin effect and proximity effect.

[0007] Two measures are known and widely applied to reduce the skin effect and proximity effect. First, reduce the cross-sectional area of ​​the conductor, and above all, reduce their height, and second, change the order of the conductors. Place This involves using [a specific method]. The latter means that the conductor changes its position within the slot after passing through the end winding region.

[0008] For example, U.S. Patent US7759834 B2 uses a solid conductor. In this case, as shown in Figure 1a, the conductor height is low, and the conductor's position is changed after passing through the end winding region corresponding to the toothed coil. This solution can provide a high slot filling ratio (SFF) value, but at the same time, it is too expensive to manufacture. This is because several different lengths of conductors need to be available depending on the machine design, and furthermore, it requires bending a solid conductor, which is not easy in practice.

[0009] In many cases, order transpose The need for this results in the conductor being twisted or rotated in the end winding region. This is realized in so-called hairpin windings or diamond windings. Examples exist in U.S. Patent Application Publication US2014015348 A1 and U.S. Patent US6894417 B2. The latter solution is reproduced in Figure 1b. This method results in longer end windings, increased losses, and longer machine lengths. Furthermore, twisting the conductor negatively affects insulation and increases the probability of electrical dielectric breakdown.

[0010] Another known solution is to use stranded wire, as in, for example, U.S. Patent US8946965 B2. The solution is reproduced in Figure 1c. However, this requires rotating the stranded conductor in the end winding region, complicating the manufacturing process.

[0011] Another known solution to this problem is the use of a Roebel bar. In International Patent Application Publication WO2009000837 A2, the individual coil sides are arranged relative to each other so that the coil sides define a Roebel bar. transpose It contains multiple stranded wires (Figure 1d). The stranded wires are arranged 180 degrees apart by the length of each slot. transpose The coil is a so-called diamond-shaped coil. This solution helps reduce electrical losses, but the label bar is expensive to manufacture and does not offer high SFF (Single-Frequency Filtration).

[0012] Litz wire can be used to reduce electrical losses due to the skin effect and proximity effect. Although Litz wire has long been known in the field of electromechanics, its applications have been limited to high-end applications characterized by very high frequencies. While the slot filling density (SFF) that can be achieved with Litz wire can reach 60-65%, it comes with a relatively high price, which has always been cited as a drawback of this type of conductor, and its application has been limited to the aforementioned areas.

[0013] To summarize the above, in most types of windings, the order transpose It is known that this is desirable, and the order transpose A common method to achieve this is to use hairpin (rotated or twisted) end windings. Another common method is to use stranded wires and solid conductors in distributed windings.

[0014] Nevertheless, better machine designs are needed, especially for machines designed to operate at high frequencies. Improvements would undoubtedly lead to better manufacturability, higher efficiency, and greater reliability.

[0015] Using open slots can lead to better manufacturability. With machines featuring semi-closed slots, it can take hours to complete the insertion of windings into the stator.

[0016] Higher efficiency can be achieved by reducing electrical losses due to the skin and proximity effects.

[0017] By avoiding rotation and twisting of the conductor, the risk of shock to the conductor insulation and dielectric breakdown can be reduced, potentially leading to higher reliability. [Overview of the project] [Problems that the invention aims to solve]

[0018] The main objective of the present invention is to provide an electromachine that partially or completely solves the aforementioned drawbacks and deficiencies of the prior art.

[0019] Furthermore, an object of the present invention is to provide an electrical machine that improves manufacturability by shortening the time required to insert windings into the stator.

[0020] The objective of the present invention is to provide an electrical machine with improved efficiency by reducing electrical losses.

[0021] The object of the present invention is to provide electrical machinery with higher reliability by avoiding rotation and twisting of conductors and reducing the risk of impact and dielectric breakdown to conductor insulation.

[0022] Further objectives will become clear from the following description, claims, and accompanying drawings. [Means for solving the problem]

[0023] An electrical machine according to the present invention is disclosed in claim 1. Preferred features of the electrical machine according to the present invention are disclosed in the dependent claims.

[0024] The present invention relates to improvements in electrical machines, particularly improvements in the arrangement of windings in the stator of an electrical machine.

[0025] The present invention is based on utilizing the inherent characteristics of Litz wire. First, the winding design according to the present invention utilizes the inherent order of the fine strands within the Litz wire, thereby avoiding the need to twist the strands in the end winding region. Second, the mechanical flexibility of the Litz wire enables the end windings to be made shorter and more compact without sacrificing reliability. transpose When designing an electrical machine using a shaped solid conductor, the designer aims for a high SFF (slot fill factor) to make the slots smaller. However, relatively high losses due to the skin effect and proximity effect require larger slot peripheral dimensions for efficient heat removal, thus limiting the extent to which the slot area can be reduced.

[0026] According to the present invention, a lower SFF (slot fill factor) is acceptable due to better current distribution and lower electrical losses within the slots, thereby making heat removal easier by applying Litz wire. This alternative approach results in slot sizes comparable to conventional designs.

[0027] Therefore, in the present invention, the coils are made of shaped Litz wire and are formed before being placed in the empty slots of the stator. Coils belonging to different phases form an overlapping structure like the windings of a conventional distributed winding, with the coil side faces of each coil being arranged one above the other along the height of the slot.

[0028] The result is a compact and short end winding. An additional advantage is higher reliability due to no twisting of the conductors. Also, it is easy to arrange phase insulation between the end windings, preventing phase short circuits.

[0029]

[0030] ​Litz wire is not as expensive as, for example, curved solid conductors or Label bars of varying lengths. Therefore, electrical machinery that is highly efficient due to its low losses does not come at a very high cost.

[0031] Accordingly, according to the present invention, the stator is provided with a plurality of slots extending laterally from the stator, the slots being open, and the coil according to the present invention is disposed within the slots. The coil according to the present invention includes first and second coil side portions consisting of several conductors of Litz wire arranged in a row successively along the slot height, as described above, and the end winding region connects the first and second coil side portions outside the slots.

[0032] According to the present invention, the number of conductors on the side surface of the coil can be any two or more.

[0033] According to the present invention, the first and second coil side portions of each coil are arranged in separate, non-adjacent slots, the first coil side portion of each coil is arranged in one of the slots near the bottom of the slots, and the second coil side portion of each coil is arranged in one of the non-adjacent slots near the opening of the slots.

[0034] According to the present invention, some or all of the conductors are arranged in the end winding region of each of the coils. transpose This changes their vertical positions on multiple coil sides. The end winding region of the Litz wire conductor is not twisted or rotated around the conductor axis. Depending on the number of conductors, the arrangement of conductors on the first and second coil sides differs. This will be explained in detail in the following example.

[0035] As described above, when the two coil sides of two different coils based on two different phases enter the same slot, the coil sides are arranged one after the other along the slot height, forming a two-layer structure.

[0036] According to one embodiment of the present invention, the conductor is pre-formed to have a substantially square or rectangular shape.

[0037] In a further embodiment of the present invention, the opening of the open slot is covered with a magnetic, semimagnetic, or nonmagnetic slot wedge.

[0038] Further preferred features and advantageous details of the present invention are disclosed in the following exemplary description, claims, and accompanying drawings.

[0039] The present invention will be described in more detail with reference to the following drawings. [Brief explanation of the drawing]

[0040] [Figure 1a] This figure shows one conventional technique in winding design. [Figure 1b] This diagram shows another conventional technique in winding design. [Figure 1c] This figure shows yet another conventional technique in winding design. [Figure 1d] This figure shows other conventional techniques in winding design. [Figure 2a] This diagram shows the transposed order of the windings of the same coil within a slot. [Figure 2b] This diagram shows the sequential transposition of windings within the same coil within a slot, and in particular, the sequential transposition of two conductors in the end winding region. [Figure 2c] This diagram shows the sequential transposition of windings within the same coil within a slot, and in particular, the sequential transposition of all conductors in the end winding region. [Figure 2d] This diagram shows the sequential transposition of windings within the same coil within a slot, and in particular, the sequential transposition of conductors. [Figure 3a] This diagram shows the windings and end windings of the two coils, and in particular, how the two coils are positioned within the slot. [Figure 3b] This diagram shows the windings and end windings of two coils. [Figure 4a] This is a schematic diagram of a coil, showing its three-dimensional appearance. [Figure 4b] This is a schematic diagram of a coil, showing the coil as viewed from the tangential direction. [Figure 4c] This is a schematic diagram of one coil design, showing its axial appearance as seen from the end winding side. [Figure 4d] This is a schematic diagram of one of the coils, showing the coil according to the present invention as viewed from above. [Figure 5] This is a 3D view of the end windings inserted into the stator slots. [Modes for carrying out the invention]

[0041] Refer first to Figures 1a-d. These illustrate the four prior art winding designs described above, which the present invention aims to improve upon.

[0042] Refer to Figures 2a to 2d. These are schematic diagrams illustrating the principle of winding design for an electromechanical stator according to the present invention. According to the present invention, the stator is formed by a stator armature 100 (for example, an iron core or similar) having a plurality of open slots 110 extending laterally. Here, the open slots 110 have a bottom 111 at one end and an opening 112 at the other end.

[0043] Figure 2a shows one embodiment, in which the coil 10 (as shown in detail in Figures 4a-d) includes a first coil side portion 11 and a second coil side portion 12, which are separately arranged in a plurality of non-adjacent open slots 110 of the stator armature 100. The first coil side portion 11 and the second coil side portion 12 each consist of several conductors 20A-D arranged in a row successively along the height of the slot 110, and an end winding region 30 (see Figures 2b-c) connects the first coil side portion 11 and the second coil side portion 12. The conductors 20A-D are Litz wire conductors according to the present invention. According to one embodiment of the present invention, the Litz wire conductor is pre-formed to have a substantially square or rectangular shape, and its width corresponds to the width of the open slot 110.

[0044] As the conductors pass through the end winding region 30 (as shown in Figures 2b-c), some or all of the conductors 20A-D change their positions along the height of the slot 110, altering their positions on the first coil side portion 11 and the second coil side portion 12. transpose Figure 2b shows how conductors 20B and 20C change their positions on the first coil side surface 11 and the second coil side surface 12: The conductor 20C second closest to the slot opening 112 in the first coil side portion 11 is sequential in the end winding region 30. transpose This brings it second closest to the slot bottom 111 on the second coil side portion 12; The conductor 20B that is second closest to the slot bottom 111 in the first coil side portion 11 is sequential in the end winding region 30. transpose This brings it second closest to the slot opening 112 in the second coil side portion 12.

[0045] Figure 2b shows the order of the two conductors 20B and 20C in the end winding region 30. transpose Figure 2c shows what it looks like, and the order of all conductors 20A to D in the end winding region 30. transpose This shows what it looks like.

[0046] Refer to Figure 2d here. Figure 2d shows how conductor 20A is arranged transpose This indicates whether it is done. The conductor 20A closest to the slot bottom 111 of the first coil side portion 11 is sequential along the coil height in the end winding region 30. transpose This brings it closest to the slot opening 112 of the second coil side portion 12. This conductor 20A has the longest end winding region.

[0047] Furthermore, in this shown embodiment, the second closest conductor 20B to the slot bottom 111 of the first coil side portion 11 is sequential along the coil height in the end winding region 30. transpose The conductor 20C that is second closest to the slot opening 112 in the second coil side portion 12 is then aligned with the coil height of the end winding region 30. transpose This brings it second closest to the slot bottom 111 of the second coil side portion 12.

[0048] The conductor 20D closest to the slot opening 112 of the first coil side portion 11 is ordered along the coil height of the end winding region 30 so that it is closest to the slot bottom 111 of the second coil side portion 12. transpose It will be done.

[0049] Therefore, the order of conductors 20A to D is reversed at the second coil side surface 12 relative to the first coil side surface 11.

[0050] According to the present invention, none of the conductors 20A to D are twisted or rotated around their respective axes.

[0051] Next, refer to Figure 3a. Figure 3a shows how two coils (solid lines indicate conductors 20A to D of the first coil, and dotted lines indicate conductors 20E to H of the second coil) are arranged successively within the slot 110. The first coil and the second coil are shown having the first coil side portion 11 and the second coil side portion 12 as described above. The first coil side portion 11 and the second coil side portion 12 each consist of several conductors 20E to H arranged in a row successively along the height of the slot 110, similar to the first coil.

[0052] Refer to Figure 3b. In the present invention, when the first coil side portion 11 and the second coil side portion 12 of different coils 10a to n based on different phases enter the same slot 110, the respective first coil side portion 11 or second coil side portion 12 of the different coils 10a to n are positioned one after the other along the height of the slot 110, forming a two-layer structure. In Figure 3b, this situation is shown for coils 10d and 10n, where the first coil side portion 11 of coil 10d and the second coil side portion 12 of coil 10n fall into the same slot 110, with the coil side portion 11 positioned closest to the bottom 111 of the slot 110 and the coil side portion 12 positioned closest to the opening 112.

[0053] The connected coil series according to the present invention provides a two-layer distributed winding to the stator armature 100. As can be seen from Figure 3b, this makes the end winding region 30 very compact.

[0054] Now, refer to Figures 4a to 4d. These figures show details of what the coil 10 according to the present invention looks like.

[0055] Figure 4a shows the three-dimensional (3D) appearance of the coil 10, Figure 4b shows the coil 10 viewed from the tangential direction, Figure 4c shows the axial appearance viewed from the end winding region 30 side, and Figure 4d shows the coil 10 according to the present invention viewed from above.

[0056] Refer to Figure 5 here. A 3D view of the end winding region 30 is presented, showing the compact structure of the end winding region 30 made possible by the flexibility of the end winding made of Litz wire. Note that a hairpin end winding or a torsion-free solution in the end winding region 30 can only be achieved by the flexibility of Litz wire.

[0057] Changes This type of winding can be applied to AC machines such as synchronous machines and induction machines.

[0058] In some embodiments, a wedge may be present to cover the opening of the open slot. The wedge may be nonmagnetic, semimagnetic, or magnetic.

[0059] The number of conductors on the side of the coil can be arbitrary (two or more). For example, if the number of conductors on the side of the coil is three, the order transpose It proceeds as follows: The first conductor, positioned closest to the bottom of the slot on the side of the first coil, is aligned along the coil height of the end winding region to the position closest to the slot opening on the side of the second coil. transpose To be done; The second conductor, located closest to the slot opening on the side of the first coil, is positioned along the coil height of the end winding region, closest to the bottom of the slot on the side of the second coil. transpose To be done; • The third conductor between the first and second conductors is in order transpose It will not be done.

[0060] order transpose The same principle applies to a different number of conductors. [Explanation of symbols]

[0061] 10 coils 10a~n Coil 1~n Coil 11. Side surface of the first coil 12. Second coil side section 20A First conductor of the first coil 20B Second conductor of the first coil 20C Third conductor of the first coil 20D Fourth conductor of the first coil 20E First conductor of the second coil 20F Second conductor of the second coil 20G Third conductor of the second coil 20H Second coil's fourth conductor 30 End winding 100 Stator armature 110 Stator armature open slot 111 Bottom of slot 110 112 Opening of slot 110

Claims

1. It is an electrical machine, A stator formed by a stator armature (100) having a plurality of slots (110), wherein each slot has a height and an open end, and extends laterally to the stator armature (100), A plurality of continuous coils (10, 10a to n) are arranged within each of the aforementioned slots (110), Includes, Each of the aforementioned continuous coils (10, 10a to n) The first coil side portion (11) and the second coil side portion (12), Several conductors (20A to D, 20E to H) are arranged in a line one after another along the height of the aforementioned slot (110), Includes, Each of the aforementioned conductors The axis and An end winding region (30) is provided outside each slot (110) that connects the first coil side portion (11) and the second coil side portion (12) on both sides, Define, The first coil side portion (11) and the second coil side portion (12) of each of the consecutive coils (10, 10a to n) are arranged in separate, non-adjacent slots (110). The first coil side portion (11) of each of the consecutive coils (10, 10a to n) is positioned close to the bottom portion (111) of one of the slots (110) in the set of slots (110), and the second coil side portion (12) of each of the consecutive coils (10, 10a to n) is positioned close to the opening (112) of a slot (110) in a non-adjacent slot (110). Each of the conductors in each of the aforementioned consecutive coils (10, 10a to n) is a Litz wire conductor. The order of some or all of the conductors (20A to D, 20E to H) in the second coil side portion (12) is transposed in reverse order to the order of each of the consecutive coils (10, 10a to n) in the first coil side portion (11), and each of the consecutive coils (10, 10a to n) is arranged such that the reversal of the order and the change in the vertical position within each of the slots (110) in each of the coil side portions (11, 12) occur in the end winding region (30) of each of the consecutive coils (10, 10a to n). The above-mentioned electrical machine, The portions of the end winding regions on both sides of each of the aforementioned conductors (20A-D, 20E-H) are not twisted or rotated around the axis of each of the aforementioned conductors (20A-D, 20E-H), and The portions of the end winding region (30) on both sides of the first conductor (20D, 20H) are positioned closest in the axial direction to the coil side portions (11, 12) of each of the continuous coils (10, 10a to n) formed by the first coil side portion (11) and the second coil side portion (12), Regarding the remaining conductor portions (20C to A, 20G to E) of each of the continuous coils (10, 10a to n) in each of the end winding regions, The portions of the first conductors (20D, 20H) in each of the end winding regions continue adjacent to each other, The first conductor (20D, 20H) is positioned adjacent to the coil side portions (11, 12) of the continuous coils (10, 10a to n) so as to be further outward in the axial direction from the coil side portions (11, 12). The aforementioned electrical machinery.

2. The electrical machine according to claim 1, wherein when the side portions (11, 12) of each coil (10, 10a to n) with different phases are placed in a common slot (110), the side portions (11, 12) of each coil are successively arranged on top of each other along the height of the slot (110), forming a two-layer structure.

3. The electrical machine according to claim 1, wherein the conductors (20A to D, 20E to H) are pre-formed to have a substantially square or rectangular shape.

4. The electromachine according to claim 1, wherein each opening (112) of each of the open slots (110) is covered with a magnetic, semimagnetic, or nonmagnetic slot wedge.

5. The number of each conductor (20A to D, 20E to H) in each coil side portion (11, 12) is 4. The first conductor (20A-D, 20E-H), the second conductor (20A-D, 20E-H), the third conductor (20A-D, 20E-H), and the fourth conductor (20A-D, 20E-H) are transposed in reverse order along the height of each of the continuous coils (10, 10a-n) in the end winding region (30). The first conductors (20A to D, 20E to H) are closest to the bottom (111) of the slot in the first coil side portion (11) and closest to the opening (112) of the slot in the second coil side portion (12). The second conductors (20A to D, 20E to H) are second closest to the bottom (111) of the slot in the first coil side portion (11) and second closest to the opening (112) of the slot in the second coil side portion (12). The third conductors (20A-D, 20E-H) are second closest to the opening (112) of the slot in the first coil side portion (11), and second closest to the bottom (111) of the slot in the second coil side portion (12), and The electrical machine according to claim 1, wherein the fourth conductor (20A to D, 20E to H) is closest to the opening (112) of the slot in the first coil side portion (11) and closest to the bottom (111) of the slot in the second coil side portion (12).

6. The number of each conductor (20A to D, 20E to H) in each coil side portion (11, 12) is 3. The first conductors (20A-D, 20E-H) and the second conductors (20A-D, 20E-H) are transposed in reverse order along the height of each of the continuous coils (10, 10a-n) in the end winding region (30). The first conductors (20A to D, 20E to H) are positioned closest to the bottom (111) of the slot on the first coil side portion (11) and closest to the opening (112) of the slot on the second coil side portion (12). The second conductors (20A to D, 20E to H) are positioned closest to the opening (112) of the slot in the first coil side portion (11) and closest to the bottom (111) of the slot in the second coil side portion (12). On the other hand, the third conductor (20A to D, 20 to E-H) located between the first and second conductors (20A to D, 20E to H) is not transposed in the reverse order, as described in claim 1.

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