Fractional slot winding structure and fractional slot motor

Abstract

The present invention provides a fractional slot winding structure including a core provided with a plurality of slots arranged circumferentially around a central axis, the slots penetrating from a first side to a second side of the core, and a fractional slot winding including a plurality of preformed U-shaped wires, each U-shaped wire having two legs, a connected end and two free ends, and the U-shaped wires are inserted into the slots in the same direction so that all of the connected ends are located on the first side of the core and all of the free ends are located on the second side of the core. The slots extend between the two legs of each U-shaped wire, but are not uniform. The slots extend between two adjacent legs of any two adjacent U-shaped wires of the plurality of U-shaped wires, and the two adjacent legs are electrically connected to each other by the free ends extending therefrom. The present invention also provides a fractional slot motor. This invention can simplify the end structure of the fractional slot winding structure.

Description

[Technical Field]

[0001] The present invention relates generally to the field of motors, and more particularly to fractional slot winding structures and fractional slot motors. [Background technology]

[0002] As demands for motor power density and efficiency increase, hairpin windings are increasingly being applied to motors, especially electric vehicle drive motors. Many applications require motors to provide smooth torque output. To this end, fractional slot motors can be used to reduce cogging torque.

[0003] However, at present, for fractional slot motors, the welded ends of the hairpin winding are often complex in structure and large in volume, so the hairpin winding is generally used in integer slot motors, which requires a complex manufacturing process and makes it difficult to achieve automated mass production.

[0004] Therefore, it would be desirable to provide an improved fractional slot winding structure to overcome at least one of the above-mentioned drawbacks.

[0005] Summary of the Invention SUMMARY OF THE INVENTION The present invention aims to provide an improved fractional slot winding structure and a corresponding fractional slot motor in order to simplify the end structure of the fractional slot winding structure.

[0006] According to a first aspect of the present invention, there is provided a fractional slot winding structure comprising: an iron core having a plurality of slots arranged circumferentially around a central axis of the fractional slot winding structure, the slots penetrating from a first side of the iron core to a second side opposite the first side; and a fractional slot winding made of a plurality of preformed U-shaped wires, each U-shaped wire having two legs, a connecting end connecting the two legs, and two free ends extending from the two legs in a direction away from the connecting end, the plurality of U-shaped wires being inserted into the slots in the same direction so that all the connecting ends are located on the first side of the iron core and all the free ends are located on the second side of the iron core. The slot spans between the two legs of each U-shaped wire are unequal, and the slot spans between two adjacent legs belonging to any two adjacent U-shaped wires of the plurality of U-shaped wires are equal, and the two adjacent legs extending from the free ends are electrically connected to each other.

[0007] This simplifies the end structure of the fractional slot winding structure. When forming a fractional slot winding using U-shaped wires, the free ends of the U-shaped wires must span different slot numbers according to conventional wiring methods. Combining the free ends of multiple U-shaped wires results in a complex, bulky, and large end structure. According to the present invention, it is possible to ensure that the slots between any two adjacent legs of a plurality of U-shaped wires are equal, provided that the slot spans between the two legs of each U-shaped wire are not consistent. Therefore, the free ends of the multiple U-shaped wires can have a neat and regular arrangement, which is beneficial for reducing the end volume of the fractional slot winding structure.

[0008] In an exemplary embodiment of the present invention, a fractional slot winding may be arranged as a multi-layer winding such that the free ends of multiple U-shaped wires are arranged in at least two layers around a central axis, with the free ends located in odd-numbered layers in a radially outward order in the at least two layers twisted in a first circumferential direction across the same angle around the central axis, and the free ends located in even-numbered layers in a radially outward order in the at least two layers twisted in a second circumferential direction across the same angle around the central axis, with the first circumferential direction being one of a clockwise direction and a counterclockwise direction when viewed from the second side to the first side, and the second circumferential direction being the other of a clockwise direction and a counterclockwise direction when viewed from the second side to the first side. Therefore, in the process of twisting the free ends of the U-shaped wires, the free ends located in the same layer can be twisted synchronously, and the twisting tool used can have a simpler structure. This is particularly beneficial for automated mass production at low cost.

[0009] In a typical embodiment of the present invention, the plurality of slots is 96 slots, the number of poles of the fractional slot winding is 44, the fractional slot winding is formed into a three-phase winding, the slot span between two adjacent legs of any two adjacent U-shaped wires of the plurality of U-shaped wires is 2, and the plurality of U-shaped wires is composed of a first U-shaped wire with a slot span between its two legs of 2, a second U-shaped wire with a slot span between its two legs of 3, and a third U-shaped wire with a slot span between its two legs of 7. This fractional slot winding structure is particularly advantageous because it has the advantages of low cogging torque and low noise. Those skilled in the art would not adopt a 96-slot, 44-pole, 3-phase parameter configuration for a fractional slot winding structure based on conventional wiring because such a parameter configuration would make the end structure of the fractional slot winding structure very complicated and difficult to automate. However, in the present invention, a fractional slot winding structure having a parameter configuration of 96 slots, 44 poles, and 3 phases can have a simpler end structure. Additionally, fractional slot windings, which can have 96 slot, 44 pole, and 3 phase parameter configurations, can be provided in an automated manufacturing format.

[0010] According to a second aspect of the present invention, there is provided a fractional slot motor, comprising a rotor and a stator, the stator comprising a fractional slot winding structure according to the present invention. [Brief explanation of the drawings]

[0011] The principles, features, and advantages of the present invention may be better understood by reading the following detailed description of the invention when taken in conjunction with the accompanying drawings. [Figure 1] FIG. 1 illustrates a schematic representation of a fractional slot winding configuration of a motor according to an exemplary embodiment of the present invention. [Figure 2] 2A and 2B schematically illustrate a U-shaped wire for use in a fractional slot winding structure, according to an exemplary embodiment of the present invention. [Figure 3] 3A, 3B, and 3C respectively illustrate three different shapes of U-shaped wires. [Figure 4] FIG. 4 schematically illustrates a U-shaped wire arrangement for a fractional slot winding, according to an exemplary embodiment of the present invention. [Figure 5] FIG. 5 schematically illustrates the U-shaped wire arrangement of the U-phase winding of the fractional slot winding configuration shown in FIG.

[0012] Explanation of symbols 1 iron core 11 slots 12 First Aspect 13 The Second Aspect 2 Fractional slot winding 20 U-shaped wire 210 legs 211 First Leg 212 Second Leg 220 Connection end 230 Free end 231 first free end 232 second free end 21 First U-shaped wire 22 Second U-shaped wire 23 Third U-shaped wire 30 Lead Line 40 Lead wire L center axis DETAILED DESCRIPTION OF THE INVENTION

[0013] In order to make the technical problem, as well as the technical solution and beneficial technical effects more clearly understandable, the present invention will be further described in detail in combination with the accompanying drawings and several exemplary embodiments. It should be understood that the specific examples described herein are only intended to illustrate the present invention and do not limit the protection scope of the present invention.

[0014] The principle of the present invention will be described in detail by taking the fractional slot winding structure of a motor, especially a permanent magnet motor, as an example. However, those skilled in the art should understand that the fractional slot winding structure described in the present invention is not only applicable to motors, but also to other devices such as transformers.

[0015] FIG. 1 schematically illustrates a fractional slot winding structure according to an exemplary embodiment of the present invention. The fractional slot winding structure may be used in smaller numbers in a motor, for example, as a stator or rotor of the motor. The motor may be, for example, a motor or a generator. The fractional slot winding structure may particularly be a stator winding structure of the motor.

[0016] As shown in FIG. 1 , an exemplary embodiment of a fractional slot winding structure includes an iron core 1 and a fractional slot winding 2. The iron core 1 may be made of, for example, silicon steel and formed in a generally cylindrical shape. The iron core 1 is provided with a plurality of slots 11 arranged circumferentially around a central axis L of the fractional slot winding structure. The slots 11 penetrate from a first side 12 of the iron core 1 to a second side 13 opposite the first side 12. The fractional slot winding 2 is a winding having a fractional number of slots per pole and phase. The fractional slot winding 2 includes a plurality of pre-formed U-shaped wires 20 (e.g., hairpin wires).

[0017] 2A and 2B schematically illustrate U-shaped wires 20 for use in a fractional slot winding structure in accordance with an exemplary embodiment of the present invention. As shown, each U-shaped wire 20 includes two legs 210, a connection end 220 connecting the two legs 210, and two free ends 230 extending from the two legs 210 in a direction away from the connection end 220. The two legs 210 include a first leg 211 and a second leg 212. The two free ends 230 include a first free end 231 and a second free end 232. The first free end 231 extends outward from the first leg 211, and the second free end 232 extends outward from the second leg 212.

[0018] As can be seen in relation to FIG. 1 , the multiple U-shaped wires 20 are inserted into the multiple slots 11 in the same direction. Here, the U-shaped wires 20 are inserted into the multiple slots 11 in a direction from the first side 12 to the second side 13 of the iron core 1, for example, so that the connection ends 220 of the U-shaped wires 20 are all located on the first side 12 of the iron core 1 and the free ends 230 of the U-shaped wires 20 are all located on the second side 13 of the iron core 1. The legs 210 of the U-shaped wires 20 are received in the slots 11 to form active edges. The number of slots spanned by the two legs 210 of each U-shaped wire 20 does not match, i.e., the number of slots spanned by the connection ends 220 of each U-shaped wire 20 on the first side 12 of the iron core 1 does not match, or the number of slots spanned by the two legs 210 of each U-shaped wire 20 does not match. The slot spans between two adjacent legs 210 belonging to any two adjacent U-shaped wires 20 of the multiple U-shaped wires 20 are equal. Two adjacent legs 210 are electrically connected to each other by free ends 230 extending therefrom. The terms referred to herein refer to proximity in circuit connection, not physical location.

[0019] Therefore, the end structure of the fractional slot winding structure can be simplified. When a fractional slot winding 2 is formed using U-shaped wires 20, the free ends 230 of each U-shaped wire 20 must span different numbers of slots in conventional wiring. Instead, the free ends 230 of multiple U-shaped wires 20 join together to form a more complex end structure. According to the present invention, even if the slot spans between the two legs 210 of each U-shaped wire 20 are inconsistent, the slot spans between any two adjacent legs 210 of the multiple U-shaped wires 20 are equal. Therefore, while the connection ends 220 of the multiple U-shaped wires 20 have a somewhat more complex arrangement than conventional wiring, the free ends 230 of the multiple U-shaped wires 20 can have a neat and regular arrangement. This is beneficial to the overall reduction in the end volume of the fractional slot winding structure.

[0020] This fractional slot winding structure is particularly easy to manufacture. In particular, after each U-shaped wire 20 is sequentially positioned and inserted into the slot 11 according to the wiring rules of the present invention, the free ends 230 of adjacent U-shaped wires 20 need to be twisted so that they are adjacent to each other to facilitate the formation of a conductive connection between them. This conductive connection can be implemented, for example, by welding the free ends 230 of adjacent U-shaped wires 20 together. The free ends 230 may also be referred to as welded ends. FIG. 2A schematically illustrates the U-shaped wire 20 before the twisting operation. FIG. 2B schematically illustrates the U-shaped wire 20 after the twisting operation. In particular, the twisting step in the manufacturing process of the fractional slot winding structure can be simplified by providing a neat and regular arrangement of the free ends 230 of the U-shaped wires 20. This pure and regular arrangement also simplifies the welding operation and avoids complex movement trajectories of the welding tool. This fractional slot winding structure therefore facilitates automated mass production.

[0021] In the present invention, "the slot spans between the two legs of each U-shaped wire are unequal" should be understood to mean that the slot spans between the two legs of each U-shaped wire are not identical. That is, the slot span between the two legs of any U-shaped wire in the plurality of U-shaped wires is not equal to the slot span between the two legs of at least one other U-shaped wire in the plurality of U-shaped wires. Alternatively, the plurality of U-shaped wires includes multiple U-shaped wires having different spans between their two legs. The slot spans between the two legs are the same circumferential (clockwise or counterclockwise) slot spans.

[0022] Preferably, the fractional slot winding 2 may be arranged as a multi-layer winding such that the free ends 230 of the multiple U-shaped wires 20 are arranged in at least two layers around the central axis L. The multi-layer winding is arranged radially around the central axis L. As shown in FIG. 1 , the free ends 230 of the multiple U-shaped wires 20 are arranged in four layers around the central axis L. The free ends 230 in the odd-numbered layers are all twisted in a first circumferential direction in a radially outward order, spanning the same angle around the central axis L, while the free ends 230 in the even-numbered layers, which are radially outward, are all twisted in a second circumferential direction, spanning the same angle around the central axis L. Here, the first circumferential direction is a counterclockwise direction when viewed from the second side surface 13 to the first side surface 12, and the second circumferential direction is a clockwise direction when viewed from the second side surface 13 toward the first side surface 12. In other embodiments, the first circumferential direction can be clockwise from the second side 13 to the first side 12, and the second circumferential direction can be counterclockwise from the second side 13 to the first side 12.

[0023] Therefore, in the process of twisting the free ends 230 of the U-shaped wires 20, the free ends 230 located in the same layer can be twisted synchronously, and the twisting tool used can have a simpler structure, which is particularly advantageous for automated mass production at low cost.

[0024] In an exemplary embodiment of the present invention, the free ends 230 extending from two adjacent legs 210 may be twisted toward each other in opposite directions, span the same angle around the central axis L, and be electrically connected to each other. This is particularly beneficial for the orderly and regular arrangement of the free ends 230 of the U-shaped wire 20. In this example, the free ends 230 extending from two adjacent legs 210 each span 50% of the slot between the two adjacent legs 210. In other examples, the free ends 230 extending from two adjacent legs 210 may also be twisted in opposite circumferential directions relative to each other and span different angles around the central axis L. For example, one of the two free ends 230 extending from two adjacent legs 210 may span 25% of the slot span between the two adjacent legs 210, and the other of the two free ends 230 may span 75% of the slot span between the two adjacent legs 210. Alternatively, one of the free ends 230 extending from two adjacent legs 210 may span one-third of the slot span between the two adjacent legs 210, while the other of the two free ends 230 may span one-third of the slot span between the two adjacent legs 210.

[0025] The confluent slots extending between the two legs 210 of each U-shaped wire 20 can be conveniently achieved by forming the U-shaped wire 20 into different shapes. In an exemplary embodiment of the present invention, the plurality of U-shaped wires 20 includes U-shaped wires 20 of at least three different shapes. The different shapes of the U-shaped wires 20 have different slot spans between the two legs 210. That is, the connection ends 220 of any two of the differently shaped U-shaped wires 20 span different numbers of slots on the first side 12 of the core 1, or the number of slots between the two legs 210 of the differently shaped U-shaped wires 20 is mismatched. By utilizing at least three different shapes of the U-shaped wire 20 to provide a neat and regular arrangement of the free ends 230 of the U-shaped wires 20, the number of slots and the number of poles of a fractional slot winding structure can be selected within a wider range.

[0026] 3A, 3B, and 3C show three different shapes of U-shaped wire 20, respectively. These three different shapes of U-shaped wire 20 can be inserted into slots 11 of the same iron core 1 to form fractional slot windings 2. As can be seen, the configurations of these three differently shaped U-shaped wires 20 are similar, but the spacing between their legs 210 is different from one another. Therefore, when the three differently shaped U-shaped wires 20 are inserted into slots 11 of the iron core 1, the number of slots opened by their connection ends is also different from one another accordingly.

[0027] The U-shaped wire 20 is preferably a flat wire. The U-shaped wire 20 may have a generally rectangular cross section. This can increase the slot-filling speed and reduce the resistance of the fractional slot winding 2, increasing the motor's power density and improving heat dissipation. Exemplary embodiments of the present invention fully incorporate the advantages of flat wire winding and fractional slot winding, particularly with the goal of achieving this combination at low cost and in high-volume production.

[0028] FIG. 4 schematically illustrates a U-shaped wire arrangement for a fractional slot winding structure, according to an exemplary embodiment of the present invention.

[0029] Here, the fractional slot winding 2 is formed as a three-phase winding including, for example, a U-phase winding, a V-phase winding, and a W-phase winding. In Fig. 4, windings with different phases are shown without color. In other embodiments, the fractional slot winding 2 may also be formed as a single-phase winding, a two-phase winding, or the like.

[0030] In this embodiment, the core 1 may be provided with 96 slots 11 arranged circumferentially around the central axis L of the fractional slot winding structure (see FIG. 1 ). For clarity, these 96 slots 11 are shown schematically in FIG. 4 in an expanded format with upper and lower portions to fully illustrate the 96 slots 11 of the fractional slot winding structure. As described above, the fractional slot winding 2 comprises a plurality of preformed U-shaped wires 20, each U-shaped wire 20 having two legs 210, a connection end 220, and two free ends 230. The U-shaped wires 20 are inserted into the slots 11 in the same direction. The free ends 230 of the U-shaped wires 20 are twisted to form a conductive connection between the free ends 230 of adjacent U-shaped wires 20. This conductive connection may be implemented, for example, by welding the free ends of adjacent U-shaped wires 20 together. In FIG. 4 , the legs 210 are represented by dots, the connecting ends 220 are represented by solid lines, and the free ends 230 are represented by dashed lines. The dashed lines between two adjacent legs 210 represent the two free ends 230 extending from these legs 210. For clarity, the welded joints between the adjacent free ends 230 are not shown in FIG. 4 . The number of poles of the fractional slot winding 2 is 44. Here, the least common multiple of the number of slots and the number of poles of the fractional slot winding 2 is 1056. The ratio of the number of slots to the least common multiple of the number of slots and the number of poles is preferably less than 1 / 11. This helps reduce cogging torque and noise. Furthermore, the greatest common divisor between the number of slots and the number of poles of the fractional slot winding 2 is 4. In particular, the greatest common divisor between the number of slots and the number of poles of the fractional slot winding 2 may be greater than 4, which also reduces motor noise. It is therefore particularly advantageous to configure the fractional slot winding 2 as a 96 slot 44 pole winding.

[0031] It can be seen that the number of slots per pole and phase of this fractional slot winding 2 is not an integer. In particular, the product of the number of slots per pole and phase of the fractional slot winding structure and 2 is not an integer. In this case, with conventional wiring, the free ends 230 of the fractional slot winding 2 have a complex structure and a large volume. In particular, when the fractional slot winding 2 is configured as a 96-slot, 44-pole, three-phase winding, conventional wiring causes the slot span of the free ends 230 of each U-shaped wire 20 to vary significantly. Therefore, the end structure of the fractional slot winding 2 has a complex structure and a large volume, which complicates the twisting operation of the free ends 230 or even makes it difficult to automate the twisting operation. Furthermore, subsequent manufacturing processes, such as welding, become more difficult.

[0032] 1 and 4, the U-shaped wire 20 may be arranged in multiple radial loops around the central axis L, with the U-shaped wire 20 belonging to the same phase winding in series with each other in different loops. In particular, the number of slots per pole and phase of the fractional slot winding structure and the number of turns of the U-shaped wire 20 are not integer numbers.

[0033] As shown in FIG. 4, the U-shaped wire 20 is arranged in two turns to form four layers of wire radially from the inside to the outside, namely L1, L2, L3, and L4.

[0034] The free ends 230 located in the first and third layers are both twisted in a first circumferential direction and extend at the same angle around the central axis L, and the free ends 230 located in the second and fourth layers are both twisted in a second circumferential direction and extend at the same angle around the central axis L. Here, the free end 230 of each U-shaped wire 20 spans a slot 11 or slot span 1 in the second side 13 of the iron core 1. In this embodiment, for two adjacent legs 210 belonging to any two adjacent U wires 20 of the plurality of U wires 20, it can be seen that the free ends 230 extending from the two adjacent legs 210 form the same angle around the central axis L and each span 50% of the slot between the two adjacent legs 210. In other embodiments, the free ends 230 extending from the two adjacent legs 210 may also be twisted in opposite circumferential directions relative to each other and may span different angles around the central axis L. For example, in an exemplary embodiment similar to the example shown in FIG. 4 , all of the free ends 230 located in the first layer may be twisted in a first circumferential direction and span 0.5 slots around the central axis L, i.e., subtending an angle corresponding to 0.5 slots, and all of the free ends 230 located in the second layer may be twisted in a second circumferential direction and span 1.5 slots around the central axis L, i.e., subtending an angle corresponding to 1.5 slots. In this case, the free ends 230 located in the third layer, like the free ends 230 located in the first layer, may be twisted in a first circumferential direction and span 0.5 slots around the central axis L, i.e., subtending an angle corresponding to 0.5 slots, and the free ends 230 located in the fourth layer may be twisted in a second circumferential direction and span 1.5 slots around the central axis L, like the free ends 230 located in the second layer, i.e., subtending an angle corresponding to 1.5 slots. Thus, all free ends 230 located in odd-numbered layers in the radially outward direction are twisted in a first circumferential direction and span the same angle around the central axis L, and all free ends 230 located in even-numbered layers in the radially outward direction are twisted in a second circumferential direction and span the same angle around the central axis L.Alternatively, the free ends 230 located in the third layer may be made to extend around the central axis L at a different angle than the free ends 230 located in the first layer, for example, spanning an angle corresponding to one slot, and the free ends 230 located in the fourth layer may extend around the central axis L at a different angle than the free ends 230 located in the second layer, for example, spanning an angle corresponding to one slot.

[0035] A fractional slot winding structure according to an exemplary embodiment of the present invention is further described below in conjunction with FIG. 5. FIG. 5 schematically illustrates the arrangement of U-shaped wires 20 for the U-phase winding of the fractional slot winding structure shown in FIG. 4, where legs 210 are indicated by dots and connection ends 220 are represented by solid lines. Free ends 230 are indicated by dashed lines. In this example, adjacent free ends 230 are welded, and the weld joints between the free ends 230 are schematically shown in FIG. 5 as squares, with the solid lines indicating that the connection ends 220 are at different spatial heights (perpendicular to the page) from the weld points.

[0036] The U-phase winding includes a lead-in wire 30, a lead-out wire 40, and at least one U-shaped wire 20 connected in series between the lead-in wire 30 and the lead-out wire 40. The U-phase winding may include the lead-in wire 30, the lead-out wire 40, and at least one U-shaped wire 20, thereby simplifying the manufacturing process.

[0037] The U-shaped wire 20 of the U-phase winding is arranged in substantially two turns about the central axis L and is formed radially from the inside to the outside into four wire layers, namely, L1, L2, L3, and L4.

[0038] The U-shaped wire 20 of the U-phase winding may include a first U-shaped wire, a second U-shaped wire, and a third U-shaped wire of a different shape. In some embodiments of the present invention, the slot span between the two legs 210 of the first U-shaped wire is 2, the slot span between the two legs 210 of the second U-shaped wire is 3, and the slot span between the two legs 210 of the third U-shaped wire is 7. It can be seen that for different shapes of the U-shaped wire 20, the slot spans two legs 210. For example, the slot between the two legs 210 of the third U-shaped wire is more than three times the slot span of the two legs 210 of the first U-shaped wire.

[0039] Take U-shaped wires 20 1 to 3 of the U-phase winding as an example. As shown in FIG. 5 , the first U-shaped wire 21 of the U-phase winding is a second U-shaped wire inserted into the third and sixth slots from the first side 12, the second U-shaped wire 22 of the U-phase winding is a first U-shaped wire inserted into the eighth and tenth slots from the first side 12, and the third U-shaped wire 23 of the U-phase winding is a third U-shaped wire inserted into the twelfth and nineteenth slots from the first side 12. A first free end 231 (shown in FIG. 2B ) of the first U-shaped wire 21 is twisted clockwise (i.e., leftward in FIG. 5 ) and spans one slot 11 to electrically connect with the lead-in wire 30.

[0040] The second free end 232 (shown in FIG. 2B ) of the first U-shaped wire 21 is twisted in a counterclockwise direction (i.e., to the right in FIG. 5 ) starting in the sixth slot, spanning one slot, and terminating in the seventh slot. The first free end 231 of the second U-shaped wire 22 is twisted in a clockwise direction starting in the eighth slot, spanning one slot, and terminating in the seventh slot. Thus, a conductive connection is formed between the second free end 232 of the U-shaped wire 21 of the first U-phase winding and the first free end 231 of the U-shaped wire 22 of the second U-phase winding. In particular, the second free end 232 of the U-shaped wire 21 of the first U-phase winding may be welded together with the first free end 231 of the U-shaped wire 22 of the second U-phase winding at the seventh slot. Similarly, the second free end 232 of the U-shaped wire 22 of the second U-phase winding is twisted counterclockwise, starting at the tenth slot, spanning one slot, and terminating at the eleventh slot. The first free end 231 of the third U-shaped wire 23 of the third U-phase winding is twisted clockwise, starting at the twelfth slot, spanning one slot, and terminating at the eleventh slot. Therefore, the second free end 232 of the U-shaped wire 22 of the second U-phase winding can be conveniently welded together with the first free end 231 of the U-shaped wire 23 of the adjacent third U-phase winding. The other U-shaped wires 20 of the U-phase winding are similarly arranged as shown in FIG. 5.

[0041] Referring again to FIG. 4, the V-phase winding and W-phase winding of the fractional slot winding 2 are arranged similarly to the U-phase winding, with the V-phase winding offset by 16 slots 11 from the U-phase winding, and the W-phase winding offset by 32 slots 11 from the U-phase winding.

[0042] It should be understood that expressions such as "first," "second," and the like are used herein for descriptive purposes only and should not be construed as indicating or implying relative importance or the number of technical features shown. Thus, features defining "first" and "second" may explicitly or implicitly include at least one of the features. As used herein, "plurality" means at least two, e.g., two, three, etc., unless expressly and specifically qualified otherwise. As used herein, "axial," "circumferential," and "radial" are all relative to the central axis of the fractional slot winding structure.

[0043] Although specific embodiments have been described above, even if only individual embodiments are described with respect to specific features, this does not intend to limit the scope of the novel disclosure. The examples of features provided in the present invention are illustrative and not intended to be limiting, unless otherwise specified. In a specific implementation, multiple features may be combined with each other according to actual requirements and where technically feasible. In particular, features of different embodiments may also be combined with each other. Various substitutions, changes, and modifications may be made without departing from the spirit and scope of the present disclosure.

Claims

1. A fractional slot winding structure, an iron core (1) having a plurality of slots (11) arranged circumferentially around a central axis (L) of the fractional slot winding structure, the slots (11) penetrating from a first side (12) of the iron core (1) to a second side (13) opposite the first side (12); a fractional slot winding (2) including a plurality of pre-formed U-shaped wires (20), each U-shaped wire (20) having two legs (210), a connection end (220) connecting the two legs (210), and two free ends (230) extending from the two legs (210) in a direction away from the connection end (220); Equipped with The U-shaped wires (20) are inserted into the slots (11) in the same direction so that the connection ends (220) are located on a first side (12) of the core (1) and the free ends (230) are located on a second side (13) of the core (1); The slot (11) is inconsistent and spans between two legs (210) of each U-shaped wire (20), and the slot (11) spans between two adjacent legs (210) belonging to any two adjacent U-shaped wires (20) among the plurality of U-shaped wires (20), and the two adjacent legs (210) are electrically connected to each other by free ends (230) extending therefrom.

2. 2. The fractional slot winding structure of claim 1, wherein the fractional slot winding is arranged as a multi-layer winding such that free ends of a plurality of U-shaped wires are arranged in at least two layers around a central axis, the free ends being located in odd-numbered layers in a radially outward order in the at least two layers, twisted in a first circumferential direction, and spanning the same angle around the central axis; the free ends being located in even-numbered layers in a radially outward order in the at least two layers, twisted in a second circumferential direction, and spanning the same angle around the central axis; the first circumferential direction being one of a clockwise direction and a counterclockwise direction when viewed from the second side surface to the first side surface; and the second circumferential direction being the other of the clockwise direction and the counterclockwise direction when viewed from the second side surface to the first side surface.

3. 3. The fractional slot winding structure of claim 1, wherein the free ends (230) extending from two adjacent legs (210) are twisted toward each other in opposite directions and span the same angle around the central axis (L) to which they are electrically connected.

4. 3. The fractional slot winding structure according to claim 1 or claim 2, wherein the plurality of U-shaped wires (20) comprises at least three U-shaped wires (20) of different shapes, and the slots extending between the two legs (210) are different from each other for the different shapes of the U-shaped wires (20).

5. The plurality of slots (11) is 96 slots (11), The number of poles of the fractional slot winding (2) is 44, The fractional slot winding (2) is formed into a three-phase winding, the slot span between two adjacent legs (210) of any two adjacent U-shaped wires (20) of the plurality of U-shaped wires (20) is 2; 3. The fractional slot winding structure of claim 1 or claim 2, wherein the plurality of U-shaped wires (20) comprises a first U-shaped wire (20) having a slot span of 2 between its two legs (210), a second U-shaped wire (20) having a slot span of 3 between its two legs (210), and a third U-shaped wire (20) having a slot span of 7 between its two legs (210).

6. the number of slots per pole and phase of said fractional slot winding structure and a product of 2 are not integers; and / or the U-shaped wire (20) is arranged in a plurality of radial turns about a central axis L, and the product of the number of slots per pole and phase of the fractional slot winding structure and the number of turns of the U-shaped wire (20) is not an integer; and / or 3. The fractional slot winding structure according to claim 1, wherein a ratio of the number of slots in the fractional slot winding structure to the least common multiple of the number of slots and the number of poles in the fractional slot winding structure is 1 / 11 or less.

7. The fractional slot winding structure according to claim 1 or claim 2, wherein the U-shaped wire (20) is a flat wire.

8. A fractional slot motor comprising a rotor and a stator, the stator comprising the fractional slot winding structure of any one of claims 1 to 7.

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