CN217956809U - Fractional slot winding structure and fractional slot motor - Google Patents

Abstract

The utility model provides a fractional slot winding structure, it includes: 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 including two leg portions, a connection end, and two free ends, the plurality of U-shaped wires all being inserted into the slots in the same direction such that the connection ends are all located at a first side of the core and the free ends are all located at a second side of the core. The groove spans between two leg portions of each U-shaped conductor are not uniform, the groove spans between two adjacent leg portions respectively belonging to any two adjacent U-shaped conductors among the plurality of U-shaped conductors are equal, and the two adjacent leg portions are conductively connected to each other by free ends extending therefrom. The utility model discloses still provide a fraction groove motor. With the aid of the utility model discloses, fractional slot winding structure's tip structure can be simplified.

Description

Fractional slot winding structure and fractional slot motor

Technical Field

The utility model relates to a motor field especially relates to a fractional slot winding structure and a fractional slot motor generally.

Background

With the increasing demands on the power density and efficiency of electric motors, the hairpin windings are increasingly used in electric motors, in particular in drive motors for electric vehicles. In many applications, the motor is required to provide a smooth torque output. For this reason, a fractional slot motor may be employed in order to reduce cogging torque.

However, at present, the hairpin winding is generally applied to an integer slot motor, because in a fractional slot motor, the welding end of the hairpin winding tends to be complicated in structure, large in volume, and require a complicated manufacturing process, and it is difficult to realize mass automated production.

It is therefore desirable to provide an improved fractional slot winding structure to overcome at least one of the above disadvantages.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to provide a modified fractional slot winding structure and corresponding fractional slot motor to simplify the tip structure of fractional slot winding structure.

According to the utility model discloses an aspect provides a fractional slot winding structure, it includes: a core provided with a plurality of slots arranged in a circumferential direction around a central axis of the fractional-slot winding structure, the slots penetrating from a first side of the core to a second side opposite to the first side; and a fractional slot winding including a plurality of preformed U-shaped wires, each U-shaped wire including two legs, a connection end connecting the two legs, and two free ends extending from the two legs to a direction away from the connection end, the plurality of U-shaped wires all being inserted into the slots in the same direction such that the connection ends are all located at a first side of the core and the free ends are all located at a second side of the core. The groove spans between the two legs of each U-shaped wire are not uniform, the groove spans between two adjacent legs belonging respectively to any two adjacent U-shaped wires of the plurality of U-shaped wires are equal, and the two adjacent legs are conductively connected to each other by free ends extending therefrom.

This can simplify the end structure of the fractional-slot winding structure. Under the condition that the fractional slot winding is formed by utilizing the U-shaped wires, according to a conventional wiring mode, the free ends of the U-shaped wires need to span different slot numbers, so that the free ends of the U-shaped wires form a more complex end structure with a larger volume together. According to the utility model discloses, can be under the inconsistent condition of groove span between two shanks of each U type wire, realize belonging to respectively groove span between two adjacent shanks of two arbitrary adjacent U type wires in a plurality of U type wires all equals. Therefore, the free ends of the plurality of U-shaped wires can have an orderly regular arrangement structure. This is advantageous for reducing the end volume of the fractional slot winding structure.

In one exemplary embodiment, the fractional slot winding may be arranged in a multi-layer winding such that the free ends of the plurality of U-shaped wires are arranged in at least two layers around the central axis, wherein the free ends in odd-numbered ones of the at least two layers that are radially outward ordered are all twisted in a first circumferential direction and span the same angle about the central axis, and the free ends in even-numbered ones of the at least two layers that are radially outward ordered are all twisted in a second circumferential direction and span the same angle about the central axis, wherein the first circumferential direction is one of a clockwise direction and a counterclockwise direction as viewed from the second side to the first side, and the second circumferential direction is the other of the clockwise direction and the counterclockwise direction as viewed from the second side to the first side. Therefore, during the twisting operation of the free ends of the U-shaped wires, the free ends located in the same layer can be simultaneously twisted, and the twisting tool used can have a simpler structure. This is particularly advantageous for automated mass production at low cost.

In one exemplary embodiment, the plurality of slots is 96 slots; the pole number of the fractional slot winding is 44; the fractional slot winding is formed into a three-phase winding; the groove span between two adjacent legs of any two adjacent U-shaped wires in the plurality of U-shaped wires is 2; the plurality of U-shaped wires include: a first U-shaped wire with a slot span between two legs of 2, a second U-shaped wire with a slot span between two legs of 3, and a third U-shaped wire with a slot span between two legs of 7. Such a fractional slot winding structure is particularly advantageous, having the advantages of low cogging torque, low noise, etc. According to the conventional wiring method, a parameter configuration of 96-slot 44-pole 3-phase in the fractional-slot winding structure is not adopted by the technical personnel, because the parameter configuration causes the end structure of the fractional-slot winding structure to be very complicated and difficult to realize automatic production. However, in the present invention, the fractional-slot winding structure adopting the parameter configuration of the 96-slot 44 pole 3 phase can be made to have a simpler end structure. In addition, a fractional slot winding configuration employing a 96 slot 44 pole 3 phase parametric configuration can be provided in an automated production manner.

According to a second aspect of the present invention, a fractional slot motor is provided, wherein the fractional slot motor comprises a rotor and a stator, the stator comprising a fractional slot winding structure according to the present invention.

Drawings

The principles, features and advantages of the present invention may be better understood by describing the invention in more detail below with reference to the accompanying drawings. The drawings comprise:

fig. 1 schematically shows a fractional slot winding structure for an electrical machine according to an exemplary embodiment of the present invention;

fig. 2A and 2B schematically illustrate U-shaped wires used in a fractional slot winding structure according to an exemplary embodiment of the invention;

FIGS. 3A, 3B and 3C schematically illustrate three different shapes of U-shaped conductors, respectively;

fig. 4 schematically shows a layout of U-shaped wires of a fractional slot winding structure according to an exemplary embodiment of the invention; and

fig. 5 schematically shows a layout of U-shaped wires of the U-phase winding of the fractional-slot winding structure shown in fig. 4.

List of reference numerals:

1. iron core

11. Trough

12. First side

13. Second side

2. Fractional slot winding

20 U-shaped conducting wire

210. Leg part

211. First leg part

212. Second leg part

220. Connecting end

230. Free end

231. First free end

232. Second free end

21. No. 1U-shaped lead

22. No. 2U-shaped lead

23. No. 3U-shaped lead

30. Lead-in wire

40. Lead-out wire

L central axis

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings and a plurality of exemplary embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the scope of the invention.

The principles of the present invention will be described in detail below, taking as an example a fractional slot winding structure for an electric machine, in particular a permanent magnet machine. However, it should be understood by those skilled in the art that the fractional-slot winding structure of the present invention is not only applicable to motors, but also applicable to other devices, such as transformers, etc.

Fig. 1 schematically shows a fractional slot winding structure according to an exemplary embodiment of the present invention. The fractional-slot winding structure may be used, for example, in an electric machine as at least a portion of a stator or a rotor of the electric machine. The electrical machine is for example an electric motor or a generator. The fractional-slot winding structure may be, in particular, a stator winding structure of an electric machine.

As shown in fig. 1, the fractional-slot winding structure includes a core 1 and a fractional-slot winding 2. The iron core 1 may be made of silicon steel, for example, and formed in a substantially cylindrical shape. The core 1 is provided with a plurality of slots 11 arranged in a circumferential direction around the central axis L of the fractional-slot winding structure. The slot 11 extends from a first side 12 of the core 1 to a second side 13 opposite the first side 12. Fractional slot winding 2 refers to a winding in which the number of slots per phase per pole is a fraction. The fractional-slot winding 2 comprises a preformed plurality of U-shaped wires 20 (e.g. Hairpin wires, hairpins).

Fig. 2A and 2B schematically illustrate a U-shaped wire 20 for use in a fractional slot winding structure according to an exemplary embodiment of the invention. It can be seen that each U-shaped wire 20 comprises two legs 210, a connecting end 220 connecting the two legs 210, and two free ends 230 extending from the two legs 210 in a direction away from the connecting 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 outwardly from the first leg 211 and the second free end 232 extends outwardly from the second leg 212.

As can be seen in fig. 1, the plurality of U-shaped wires 20 are inserted into the plurality of slots 11 in the same direction. The U-shaped conductors 20 are here inserted into the slots 11, for example all in a direction from the first side 12 to the second side 13 of the core 1, so that the connection ends 220 of the U-shaped conductors 20 are all located at the first side 12 of the core 1 and the free ends 230 of the U-shaped conductors 20 are all located at the second side 13 of the core 1. The leg 210 of the U-shaped wire 20 is received in the slot 11, thereby forming an effective edge. The slot spans between the two leg portions 210 of the respective U-shaped wires 20 are not uniform, i.e., the number of slots spanned by the connection end 220 of the respective U-shaped wire 20 on the first side 12 of the core 1 is not uniform, or the number of slots between the two leg portions 210 of the respective U-shaped wires 20 is not uniform. The groove spans between two adjacent leg portions 210 respectively belonging to any two adjacent U-shaped wires 20 among the plurality of U-shaped wires 20 are equal. The two adjacent leg portions 210 are conductively connected to each other by a free end 230 extending therefrom. The term "adjacent" as used herein means adjacent in a circuit connection relationship, not adjacent in a physical location.

This can simplify the end structure of the fractional-slot winding structure. In the case of forming the fractional-slot winding 2 using the U-shaped wires 20, the free ends 230 of the respective U-shaped wires 20 need to cross over different slot numbers according to a conventional wiring manner, so that the free ends 230 of the plurality of U-shaped wires 20 together form a more complicated end structure. According to the utility model discloses, can be under the inconsistent condition of groove span between two shank 210 of each U type wire 20, realize belonging to respectively groove span between two adjacent shank 210 of two arbitrary adjacent U type wires 20 in a plurality of U type wires 20 all equals. Therefore, although the connection ends 220 of the plurality of U-shaped wires 20 have a somewhat complicated arrangement structure compared to the conventional wiring manner, the free ends 230 of the plurality of U-shaped wires 20 can have an orderly regular arrangement structure. This facilitates reducing the end volume of the fractional slot winding structure as a whole.

Such a fractional slot winding structure is particularly convenient to manufacture. Specifically, after the respective U-shaped wires 20 are sequentially arranged and inserted into the slot 11 according to the wiring rule according to the present invention, the free ends 230 of the U-shaped wires 20 need to be twisted so that the free ends 230 of adjacent U-shaped wires 20 are adjacent to each other in order to form an electrically conductive connection between the free ends 230 of adjacent U-shaped wires 20. The conductive connection may be achieved, for example, by welding the free ends 230 of adjacent U-shaped wires 20 together, the free ends 230 also being referred to as welded ends. Fig. 2A schematically shows the U-shaped wire 20 before the twisting operation, and fig. 2B schematically shows the U-shaped wire 20 after the twisting operation. The twisting step in the manufacturing process of the fractional-slot winding structure can be particularly simplified by having a neat regular arrangement of the free ends 230 of the U-shaped wires 20. The arrangement structure with regular regularity can also simplify the welding operation and avoid the complex motion track of the welding tool. Therefore, such a fractional slot winding structure contributes to automated mass production.

It should be understood that in the present invention, "the groove span between the two legs of each U-shaped wire is not uniform" means that the groove spans between the two legs of each U-shaped wire are not identical. That is, a slot span between two legs of any one of the plurality of U-shaped wires is not equal to a slot span between two legs of at least one other of the plurality of U-shaped wires. Alternatively, the plurality of U-shaped conductors includes a plurality of U-shaped conductors having different spans between two legs. The slot span between the two legs refers to the slot span in the same circumferential direction (clockwise or counterclockwise).

Preferably, the fractional-slot winding 2 may be arranged in a multilayer winding such that the free ends 230 of the plurality of U-shaped wires 20 are arranged in at least two layers around the central axis L. The multilayer windings are arranged radially along a circumference around a central axis L. As shown in fig. 1, the free ends 230 of the plurality of U-shaped wires 20 are arranged in 4 layers around the central axis L. The free ends 230 in the odd numbered layers in the radially outward sequence are all twisted in a first circumferential direction and span the same angle about the central axis L, and the free ends 230 in the even numbered layers in the radially outward sequence are all twisted in a second circumferential direction and span the same angle about the central axis L. Here, the first circumferential direction is a counterclockwise direction when viewed from the second side 13 to the first side 12, and the second circumferential direction is a clockwise direction when viewed from the second side 13 to the first side 12. In another embodiment, the first circumferential direction may be a clockwise direction when viewed from the second side 13 to the first side 12, and the second circumferential direction may be a counterclockwise direction when viewed from the second side 13 to the first side 12.

Therefore, during the twisting operation of the free end 230 of the U-shaped wire 20, the free end 230 located in the same layer can be simultaneously twisted, and the twisting tool used can have a simpler structure. This is particularly advantageous for automated mass production at low cost.

In an exemplary embodiment, the free ends 230 extending from the two adjacent leg portions 210 may be twisted in opposite directions toward each other and span the same angle about the central axis L, respectively, so as to be conductively connected to each other. This further facilitates a neat and regular arrangement of the free ends 230 of the U-shaped wires 20. In this embodiment, the free ends 230 extending from the two adjacent legs 210 span 50% of the slot span between the two adjacent legs 210, respectively. In further 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 span different angles about the central axis L, respectively. For example, one of the two free ends 230 extending from the two adjacent legs 210 may span 25% of the slot span between the two adjacent legs 210, while the respective other spans 75% of the slot span between the two adjacent legs 210. Alternatively, one of the free ends 230 extending from the two adjacent legs 210 may span 1/3 of the slot span between the two adjacent legs 210, while the corresponding other spans 2/3 of the slot span between the two adjacent legs 210.

Making the slot pitch between the two legs 210 of each U-shaped wire 20 non-uniform can be conveniently achieved by pre-forming the U-shaped wires 20 to have different shapes. In an exemplary embodiment, the plurality of U-shaped wires 20 includes at least three differently shaped U-shaped wires 20. In U-shaped wires 20 of different shapes, the slot spans between the two legs 210 are different from each other. That is, the connecting ends 220 of any two of the U-shaped wires 20 of different shapes cross different slots on the first side 12 of the core 1, or the number of slots between the two leg portions 210 of the U-shaped wires 20 of different shapes is not the same. The use of U-shaped conductors 20 of at least three different shapes helps to provide a neat and regular arrangement of the free ends 230 of the U-shaped conductors 20, enabling a wider range of selection of slot and pole numbers for fractional slot winding configurations.

By way of example, fig. 3A, 3B and 3C show three different shapes of U-shaped wires 20, respectively. The three differently shaped U-shaped wires 20 may be inserted into the slots 11 of the same core 1 to form the fractional-slot winding 2. It can be seen that the three differently shaped U-shaped conductors 20 are of similar configuration but have different spacings between their legs 210 so that when the three differently shaped U-shaped conductors 20 are inserted into the slots 11 of the core 1, the number of slots spanned by their connecting ends 220 is correspondingly different from one another.

Preferably, the U-shaped wire 20 is a flat wire. The U-shaped wire 20 may have a generally rectangular cross-section. From this, can improve the groove full rate, reduce fractional slot winding 2's resistance, promote the power density of motor and improve the heat dissipation. Through the exemplary embodiments of the present invention, the advantages of fractional slot windings and flat wire windings can be fully combined, and in particular, such a combination can be achieved in mass production at a lower cost.

Fig. 4 schematically shows a layout of U-shaped wires of a fractional slot winding structure according to an exemplary embodiment of the invention.

The fractional-slot winding 2 is formed here as a three-phase winding, which includes, for example, a U-phase winding, a V-phase winding, and a W-phase winding. In fig. 4, windings of different phases are shown in different colors. In further embodiments, the fractional-slot winding 2 may also be formed as a single-phase winding, a two-phase winding, or the like.

In this embodiment, the core 1 may be provided with 96 slots 11, said 96 slots 11 being arranged in circumferential direction around the central axis L of the fractional-slot winding structure (see fig. 1). For clarity, the 96 slots 11 are schematically shown in fig. 4 divided into upper and lower portions in an expanded manner to fully illustrate the 96 slots 11 of the fractional-slot winding structure. As described above, the fractional-slot winding 2 includes a preformed plurality of U-shaped wires 20, each U-shaped wire 20 including two leg portions 210, a connection end 220, and two free ends 230. The plurality of U-shaped wires 20 are all inserted into the slot 11 in the same direction. The free ends 230 of the U-shaped wires 20 are twisted to form an electrically conductive connection between the free ends 230 of adjacent U-shaped wires 20. The conductive connection may be achieved, for example, by welding the free ends 230 of adjacent U-shaped wires 20 together. In fig. 4, the leg portions 210 are indicated by dots, the connecting ends 220 are indicated by solid lines, the free ends 230 are indicated by broken lines, and the broken line between two adjacent leg portions 210 indicates two free ends 230 extending from the two leg portions 210. For clarity, the weld between adjacent free ends 230 is not shown in fig. 4. The fractional-slot winding 2 has a pole number of 44. Here, the least common multiple of the number of slots and the number of poles of the fractional-slot winding 2 is 1056. Preferably, the least common multiple of the number of slots and the number of poles of the fractional-slot winding 2 is at least 1056. Specifically, the ratio of the number of grooves to the least common multiple of the number of grooves and the number of poles is 1/11 or less. This is advantageous in reducing cogging torque and reducing noise. The greatest common divisor of the number of slots and the number of poles of the fractional-slot winding 2 is 4. In particular, the greatest common divisor of the number of slots and the number of poles of the fractional-slot winding 2 may be 4 or more, which is also advantageous in reducing noise of the motor. It is therefore particularly advantageous for the fractional-slot winding 2 to be provided as a 96-slot 44-pole winding.

It can be seen that the number of slots per pole per phase of the fractional-slot winding 2 is not an integer. In particular, the product of the number of slots per pole per phase and 2 of the fractional-slot winding structure is not an integer. In this case, the conventional wiring manner would make the free end 230 of the fractional-slot winding 2 have a complicated structure and a large volume. Especially in the case where the fractional-slot winding 2 is provided as a 96-slot 44-pole three-phase winding, the conventional wiring would cause the slot spans of the free ends 230 of the respective U-shaped wires 20 to differ greatly. This not only makes the end portion of the fractional-slot winding 2 complicated in structure and large in volume, but also makes the twisting operation of the free end 230 complicated, and even makes it difficult to achieve an automated twisting operation. In addition, the difficulty of subsequent manufacturing steps, such as welding operations, is increased.

As can be seen from fig. 1 and 4, the U-shaped wires 20 may be arranged in a plurality of turns in the radial direction around the central axis L, and the U-shaped wires 20 belonging to the same phase winding in different turns are connected in series with each other. In particular, the product of the number of slots per pole per phase of the fractional slot winding structure and the number of turns of the U-shaped conductor 20 is not an integer.

As shown in fig. 4, the U-shaped wire 20 is arranged in 2 turns to form 4 wire layers, i.e., a 1 st layer L1, a 2 nd layer L2, a 3 rd layer L3, and a 4 th layer L4 in the radial direction from the inside to the outside.

The free ends 230 located in layers 1 and 3 are both twisted in a first circumferential direction and span the same angle about the central axis L, and the free ends 230 located in layers 2 and 4 are both twisted in a second circumferential direction and span the same angle about the central axis L. The free ends 230 of the U-shaped conductors 20 each span 1 slot 11 or slot span 1 on the second side 13 of the core 1. It can be seen that, in this embodiment, for two adjacent leg portions 210 respectively belonging to any two adjacent U-shaped wires 20 of the plurality of U-shaped wires 20, the free ends 230 extending from the two adjacent leg portions 210 respectively span the same angle around the central axis L and respectively span 50% of the slot span between the two adjacent leg portions 210. In further 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 span different angles about the central axis L, respectively. For example, in an exemplary embodiment similar to the embodiment shown in FIG. 4, the free ends 230 located in layer 1 may both twist in a first circumferential direction and span 0.5 slots about the central axis L, i.e., span an angle corresponding to 0.5 slots, and the free ends 230 located in layer 2 may both twist in a second circumferential direction and span 1.5 slots about the central axis L, i.e., span an angle corresponding to 1.5 slots. In this case, the free ends 230 located in layer 3 may be twisted in the first circumferential direction and span 0.5 slots, i.e., span an angle corresponding to 0.5 slots, about the central axis L, like the free ends 230 located in layer 1, the free ends 230 located in layer 4 may be twisted in the second circumferential direction and span 1.5 slots, i.e., span an angle corresponding to 1.5 slots, about the central axis L, like the free ends 230 located in layer 2, thereby making it possible for the free ends 230 located in odd-numbered layers in the radially outward order to be twisted in the first circumferential direction and span the same angle about the central axis L, and for the free ends 230 located in even-numbered layers in the radially outward order to be twisted in the second circumferential direction and span the same angle about the central axis L. Alternatively, the free ends 230 located in layer 3 may span a different angle about the central axis L than the free ends 230 located in layer 1, for example, an angle corresponding to 1 slot, and the free ends 230 located in layer 4 may span a different angle about the central axis L than the free ends 230 located in layer 2, for example, an angle corresponding to 1 slot.

The 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 shows a layout of U-shaped wires 20 of the U-phase winding of the fractional-slot winding structure shown in fig. 4. Here, the leg 210 is indicated by a dot, the connection end 220 is indicated by a solid line, and the free end 230 is indicated by a dotted line. In this embodiment, adjacent free ends 230 are, for example, welded together, the weld between the free ends 230 being schematically shown in block form in fig. 5, and the connecting end 220, shown in solid line, is located at a different height (in a direction perpendicular to the page) in space than the weld.

The U-phase winding includes a lead-in wire 30, a lead-out wire 40, and at least one U-shaped wire 20, the at least one U-shaped wire 20 being connected in series between the lead-in wire 30 and the lead-out wire 40. The U-phase winding may be composed of the lead-in wire 30, the lead-out wire 40, and the at least one U-shaped wire 20, thereby simplifying the manufacturing process.

The U-shaped wires 20 of the U-phase winding are arranged substantially in 2 turns around the central axis L, thereby forming 4 wire layers, i.e., the 1 st, 2 nd, 3 rd and 4 th layers L1, L2, L3 and L4 from the inside to the outside in the radial direction.

The U-shaped wires 20 of the U-phase winding may include first, second and third U-shaped wires of different shapes. In some embodiments, the slot span between the two legs 210 of a first U-shaped wire is 2, the slot span between the two legs 210 of a second U-shaped wire is 3, and the slot span between the two legs 210 of a third U-shaped wire is 7. It can be seen that the difference in slot spans of the two legs 210 is greater for differently shaped U-shaped conductors 20. For example, the slot span between the two legs 210 of the third U-shaped wire is greater than 3 times the slot span between the two legs 210 of the first U-shaped wire.

Take the 1 st to 3 rd U-shaped wires 20 of the U-phase winding as an example. As shown in fig. 5, the 1 st U-shaped wire 21 of the U-phase winding is a second U-shaped wire inserted into the 3 rd and 6 th slots from the first side 12. The 2 nd U-shaped wire 22 of the U-phase winding is the first U-shaped wire, which is inserted into the 8 th and 10 th slots from the first side 12. The 3 rd U-shaped wire 23 of the U-phase winding is a third U-shaped wire which is inserted into the 12 th and 19 th slots from the first side 12.

The first free end 231 (as viewed in fig. 2B) of the 1 st U-shaped wire 21 is twisted in a clockwise direction (i.e., in a leftward direction in fig. 5) and spans 1 slot 11 to be conductively connected to the lead-in wire 30. The second free end 232 (as shown in fig. 2B) of the 1 st U-shaped wire 21 twists in the counterclockwise direction (i.e., in the rightward direction in fig. 5) from the 6 th slot and spans the 1 slot, terminating at the 7 th slot. The first free end 231 of the 2 nd U-shaped wire 22 is twisted in a clockwise direction starting at the 8 th slot and spanning 1 slot and terminating at the 7 th slot. Thereby, it is facilitated to form an electrically conductive connection between the second free end 232 of the U-shaped wire 21 of the 1 st U-phase and the first free end 231 of the adjacent U-shaped wire 22 of the 2 nd U-phase. In particular, the second free end 232 of the 1 st U-phase U-shaped wire 21 and the first free end 231 of the 2 nd U-phase U-shaped wire 22 may be welded together at the 7 th slot. Similarly, the second free end 232 of the U-shaped conductor 22 of the 2 nd U-phase is twisted in the counterclockwise direction from the 10 th slot, and spans 1 slot and terminates at the 11 th slot. The first free end 231 of the 3 rd U-shaped wire 23 is twisted clockwise from the 12 th slot and spans 1 slot and terminates at the 11 th slot. Therefore, the second free end 232 of the U-shaped wire 22 of the 2 nd U-phase and the first free end 231 of the U-shaped wire 23 of the adjacent 3 rd U-phase can be easily welded together. The other U-shaped wires 20 of the U-phase winding are similarly arranged as shown in fig. 5.

Returning to fig. 4, the V-phase winding and the W-phase winding of the fractional-slot winding 2 are arranged similarly to the U-phase winding, with the V-phase winding being offset by 16 slots 11 with respect to the U-phase winding and the W-phase winding being offset by 32 slots 11 with respect to the U-phase winding.

It is to be understood that in this document the expressions "first", "second" etc. are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or as implying a number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. As used herein, "plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise. In this context, "axial", "circumferential", "radial", "circumferential" are all relative to the central axis of the fractional slot winding structure.

While specific embodiments have been described above, these embodiments are not intended to limit the scope of the present disclosure, even where only a single embodiment is described with respect to a particular feature. The examples of features provided in the present disclosure are intended to be illustrative, not limiting, unless expressly stated otherwise. In the specific implementation, a plurality of features can be combined with each other according to actual needs, where technically feasible. In particular, features from different embodiments may also be combined with one another. Various substitutions, alterations, and modifications may be devised without departing from the spirit and scope of the present invention.

Claims (8)

1. A fractional-slot winding structure, wherein the fractional-slot winding structure comprises:

a core (1) provided with a plurality of slots (11) arranged in a circumferential direction around a central axis (L) of the fractional-slot winding structure, the slots (11) penetrating from a first side (12) of the core (1) to a second side (13) opposite to the first side (12); and

fractional slot winding (2) comprising a plurality of pre-formed U-shaped wires (20), each U-shaped wire (20) comprising 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 plurality of U-shaped wires (20) all being inserted into the slot (11) in the same direction such that the connection ends (220) are all located at a first side (12) of the core (1) and the free ends (230) are all located at a second side (13) of the core (1),

wherein the groove spans between the two leg portions (210) of each U-shaped wire (20) are not uniform, the groove spans between two adjacent leg portions (210) respectively belonging to any two adjacent U-shaped wires (20) of the plurality of U-shaped wires (20) are equal, and the two adjacent leg portions (210) are conductively connected to each other by free ends (230) extending therefrom.

2. The fractional-slot winding structure of claim 1,

the fractional-slot winding (2) is arranged in a multi-layer winding such that the free ends (230) of the plurality of U-shaped wires (20) are arranged in at least two layers around a central axis (L), wherein the free ends (230) in odd radially outward-ordered ones of the at least two layers are all twisted in a first circumferential direction and span the same angle around the central axis (L), and the free ends (230) in even radially outward-ordered ones of the at least two layers are all twisted in a second circumferential direction and span the same angle around the central axis (L), wherein the first circumferential direction is one of a clockwise direction and a counterclockwise direction as viewed from the second side (13) to the first side (12), and the second circumferential direction is the other of the clockwise direction and the counterclockwise direction as viewed from the second side (13) to the first side (12).

3. The fractional-slot winding structure of claim 1 or 2,

the free ends (230) extending from the two adjacent legs (210) are twisted in opposite directions toward each other and span the same angle about the central axis (L) to be conductively connected to each other, respectively.

4. The fractional-slot winding structure of claim 1 or 2,

the plurality of U-shaped wires (20) includes at least three different shapes of U-shaped wires (20), wherein the groove spans between the two legs (210) are different from each other for the different shapes of U-shaped wires (20).

5. The fractional-slot winding structure of claim 1 or 2,

the plurality of grooves (11) is 96 grooves (11);

the pole number of the fractional slot winding (2) is 44;

the fractional slot winding (2) is formed into a three-phase winding;

the groove span between two adjacent leg portions (210) of any two adjacent U-shaped wires (20) in the plurality of U-shaped wires (20) is 2;

the plurality of U-shaped wires (20) includes: a first U-shaped wire (20) having a slot span of 2 between the two legs (210), a second U-shaped wire (20) having a slot span of 3 between the two legs (210), and a third U-shaped wire (20) having a slot span of 7 between the two legs (210).

6. The fractional-slot winding structure of claim 1 or 2,

the product of the number of slots of each pole and 2 of each phase of the fractional-slot winding structure is not an integer; and/or

The U-shaped conducting wire (20) is arranged in a plurality of circles around the central axis (L) in the radial direction, and the product of the number of the slots of each pole and each phase of the fractional-slot winding structure and the number of the circles of the U-shaped conducting wire (20) is not an integer; and/or

The ratio of the number of slots of the fractional-slot winding structure to the least common multiple of the number of slots and the number of poles of the fractional-slot winding structure is 1/11 or less.

7. The fractional-slot winding structure of claim 1 or 2,

the U-shaped lead (20) is a flat wire.

8. A fractional slot electrical machine, wherein the fractional slot electrical machine comprises a rotor and a stator, the stator comprising a fractional slot winding structure according to any of claims 1-7.

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