Stator assembly and motor

Abstract

The stator assembly comprises a stator core and an M-phase stator winding, the stator core is provided with N slots, the stator winding is formed by winding a plurality of hairpin coils into L layers in the slots, each phase of stator winding comprises two sub-windings, each sub-winding is provided with a plurality of hairpin coils, the plurality of hairpin coils are distributed in L different layers of the N slots, the plurality of hairpin coils of each sub-winding comprise a first hairpin coil positioned on the first layer, a second hairpin coil positioned on the Lth layer and a middle hairpin coil positioned between the first layer and the Lth layer; the first hairpin coils of the two sub-windings are short-distance hairpin coils, and the second hairpin coils of the two sub-windings are long-distance hairpin coils; the total number of the middle hairpin coils of the two sub-windings is the same, the pitch types of the middle hairpin coils are the same, and the distribution of the pitch types is the same. The counter electromotive force, the resistance and the inductance of each sub-winding are the same, and the assembly efficiency of the winding is improved.

Description

A stator assembly and a motor

[0001] This application is a divisional application of application number 202010925693.0, with the parent application filed on September 4, 2020, and the invention title is: A stator assembly and a motor. Technical Field

[0002] This invention relates to the field of motor technology, and in particular to a stator assembly and a motor. Background Technology

[0003] The peak power density of drive motors for new energy vehicles needs to reach 4kW / kg. Currently, the peak power density of motors is between 3.2-3.3kW / kg, leaving considerable room for improvement. To achieve this increase in power density, flat-wire motors represent the future development direction for automotive drive motors. Compared to round-wire motors, flat-wire motors have a higher slot fill factor, shorter winding ends, higher power density, and stronger heat dissipation capabilities, making them particularly suitable for the miniaturization and weight reduction requirements of automotive drive motors.

[0004] However, existing flat-wire motors suffer from more severe skin effect and lower assembly efficiency compared to round-wire motors. To mitigate the skin effect, flat-wire motors typically increase the number of conductor layers in the slots and reduce the thickness of the flat wire. As the number of flat wire layers increases, the winding connection methods also increase. Inappropriate connection methods can lead to winding inductance imbalance, resulting in winding circulating current, increased additional copper losses in the windings, and inconvenience in assembling flat-wire windings. Summary of the Invention

[0005] The main objective of this invention is to provide a stator assembly and motor that makes the back EMF, resistance, and inductance of each parallel sub-winding of the stator winding the same, and the current through each parallel sub-winding is also the same. This avoids additional losses caused by circulating currents between parallel sub-windings, thereby improving motor efficiency, reducing winding temperature rise, improving NVH performance, and increasing assembly efficiency.

[0006] To achieve the above objectives, this invention proposes a stator assembly for an M-phase motor with a rotor pole number of 2p, comprising a stator core and an M-phase stator winding. The inner periphery of the stator core has N slots spaced apart and extending radially along the stator core. The M-phase stator winding is formed by winding multiple hairpin coils into L layers within the slots. The slots are sequentially arranged into layers from the first to the Lth layer along the radial direction of the stator core. M is a positive integer, and L is an even number greater than or equal to 4. Each phase of the stator winding includes two sub-windings connected in parallel or series. Each sub-winding has multiple hairpin coils. The hairpin coils are distributed in L different layers of the N slots, such that the plurality of hairpin coils in each sub-winding include a first hairpin coil located in the first layer of the slot, a second hairpin coil located in the Lth layer of the slot, and an intermediate hairpin coil located between the first layer and the Lth layer of the slot; wherein, the first hairpin coils of the two sub-windings are short-pitch hairpin coils, and the second hairpin coils of the two sub-windings are long-pitch hairpin coils; the total number of intermediate hairpin coils in the two sub-windings is the same, and the intermediate hairpin coils of the two sub-windings correspond to the same pitch type, and the distribution of each pitch type is also the same.

[0007] Optionally, in the first layer of the slot, the short-pitch hairpin coils distributed on the two sub-windings are arranged in pairs, and the two short-pitch hairpin coils are spaced apart by one slot; and / or, in the Lth layer of the slot, the long-pitch hairpin coils distributed on the two sub-windings are arranged in pairs, and the two long-pitch hairpin coils are arranged intersecting by one slot.

[0008] Optionally, the intermediate hairpin coil includes a full-pitch hairpin coil with a pitch of N / (2P); or, the intermediate hairpin coil includes a long-pitch hairpin coil and a short-pitch hairpin coil with a pitch of N / (2P)+1 and a pitch of N / (2P)-1.

[0009] Optionally, the hairpin coil includes two parallel straight segments and a connecting segment connecting the two straight segments, where L=6. The plurality of intermediate hairpin coils include: a first intermediate hairpin coil, distributed in the second and third layers of the slot, wherein the two straight segments of the first intermediate hairpin coil are respectively located in the second and third layers of the slot; and a second intermediate hairpin coil, distributed in the fourth and fifth layers of the slot, wherein the two straight segments of the second intermediate hairpin coil are respectively located in the fourth and fifth layers of the slot. The total number of the first intermediate hairpin coils in the two sub-windings is equal, and the total number of the second intermediate hairpin coils is also equal.

[0010] Optionally, both the first intermediate hairpin coil and the second intermediate hairpin coil are full-pitch hairpin coils. The full-pitch hairpin coil of the first intermediate hairpin coil is a first full-pitch hairpin coil, and the full-pitch hairpin coil of the second intermediate hairpin coil is a second full-pitch hairpin coil. The total number of the first full-pitch hairpin coils in the two sub-windings is equal, and the total number of the second full-pitch hairpin coils is also equal.

[0011] Optionally, one of the first intermediate hairpin coils of the two sub-windings is a long-pitch hairpin coil, and the other is a short-pitch hairpin coil. The long-pitch hairpin coil and the short-pitch hairpin coil distributed on the two sub-windings are arranged in pairs, and the long-pitch hairpin coil is sleeved outside the short-pitch hairpin coil. Similarly, one of the second intermediate hairpin coils of the two sub-windings is a long-pitch hairpin coil, and the other is a short-pitch hairpin coil. The long-pitch hairpin coil and the short-pitch hairpin coil distributed on the two sub-windings are arranged in pairs, and the long-pitch hairpin coil is sleeved outside the short-pitch hairpin coil.

[0012] Optionally, L=4, the hairpin coil includes two parallel straight segments and a connecting segment connecting the two straight segments, the plurality of intermediate hairpin coils include: full-pitch hairpin coils, distributed in the second and third layers of the slot, the two straight segments of the full-pitch hairpin coils are respectively located in the second and third layers of the slot, and the total number of full-pitch hairpin coils in the two sub-windings is equal.

[0013] Optionally, L=4, the hairpin coil includes two parallel straight segments and a connecting segment connecting the two straight segments, the intermediate hairpin coil includes: a third intermediate hairpin coil, distributed in the second and third layers of the slot, the two straight segments of the third intermediate hairpin coil are respectively located in the second and third layers of the slot, the total number of the third intermediate hairpin coils in the two sub-windings is equal; one of the third intermediate hairpin coils in the two sub-windings is a long-pitch hairpin coil, and the other is a short-pitch hairpin coil, and the long-pitch hairpin coil and the short-pitch hairpin coil distributed on the two sub-windings are arranged in pairs, the long-pitch hairpin coil is sleeved outside the short-pitch hairpin coil.

[0014] Optionally, the voltage lead and neutral lead of each sub-winding are simultaneously located in the first layer or the Lth layer of the slot; or, the voltage lead and neutral lead of each sub-winding are respectively located in the second layer and the third layer of the slot; or, the voltage lead and neutral lead of each sub-winding are respectively located in the second layer and the first layer of the slot; or, the hairpin coil includes a U-shaped hairpin coil and an I-shaped hairpin coil; or, the phases of the M-phase stator winding are connected in a star or delta configuration.

[0015] The present invention further proposes an electric motor, characterized in that it includes a stator assembly as described above.

[0016] In the technical solution of this invention, a stator assembly is designed, in which L (L is an even number greater than or equal to 4) layers of conductors are distributed in each slot of the stator core. Two sub-windings are connected in series or parallel. Each sub-winding includes a long-pitch hairpin coil and a short-pitch hairpin coil respectively disposed in the first and Lth layers of the slot, as well as an intermediate hairpin coil. The total number of intermediate hairpin coils in the two sub-windings is the same, the pitch type of the intermediate hairpin coils is the same, and the distribution of each pitch type is also the same, so that the positions of the two sub-windings in the slots correspond, thereby making the back EMF, resistance, and inductance of the two sub-windings equal. The current flowing through the two sub-windings is the same, which avoids circulating current between the two sub-windings, thereby significantly reducing additional AC copper losses at high frequencies, improving motor efficiency during high-speed operation, and preventing local overheating of the windings, thus extending the motor's lifespan. On the other hand, it suppresses electromagnetic noise of the motor and improves NVH performance. Furthermore, it reduces the number of manufacturing molds, lowers costs, and improves processing and manufacturing efficiency. The positions of the voltage lead and neutral lead of each sub-winding are not restricted and can be flexibly set as needed, which facilitates improved welding and assembly efficiency. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0018] Figure 1 is a schematic diagram of an embodiment of the motor provided by the present invention; Figure 2 is an enlarged view of A shown in Figure 1; Figure 3 is a connection schematic diagram of the first embodiment of the connection of each phase of the M-phase stator winding shown in Figure 1; Figure 4 is a connection schematic diagram of the second embodiment of the connection of each phase of the M-phase stator winding shown in Figure 1; Figure 5 is a structural schematic diagram of the first embodiment of the hairpin coil shown in Figure 2; Figure 6 is a structural schematic diagram of the second embodiment of the hairpin coil shown in Figure 2; Figure 7 is a structural schematic diagram of the third embodiment of the hairpin coil shown in Figure 2; Figure 8 is a structural schematic diagram of the fourth embodiment of the hairpin coil shown in Figure 2; Figure 9 is a cross-sectional view along section BB of the first embodiment shown in Figure 1; Figure 10 is a cross-sectional view along section BB of the second embodiment shown in Figure 1; Figure 11 is a cross-sectional view along section BB of the third embodiment shown in Figure 1; Figure 12 is a cross-sectional view along section BB of the fourth embodiment shown in Figure 1; Figure 13 is a cross-sectional view along section BB of the fifth embodiment shown in Figure 1.

[0019] Explanation of icon numbers:

[0020] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, outside, inside, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0023] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the meaning of "and / or" throughout the text includes three parallel solutions; for example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0024] Existing flat-wire motors exhibit a more severe skin effect than round-wire motors. To mitigate this effect, flat-wire motors typically increase the number of conductor layers within the slots and reduce the thickness of the flat wire. As the number of flat wire layers increases, so do the winding connection methods. Inappropriate connection methods can lead to winding inductance imbalance, resulting in winding circulating current and increased additional copper losses in the windings.

[0025] In view of this, the present invention proposes a stator assembly and a motor, which aims to make the back EMF, resistance and inductance of each parallel sub-winding of the stator winding the same, and the current through each parallel sub-winding the same, so as to avoid additional losses caused by circulating current between parallel sub-windings, thereby improving motor efficiency and reducing winding temperature rise, and improving NVH performance.

[0026] Figure 1 is a schematic diagram of an embodiment of the motor provided by the present invention; Figure 2 is an enlarged view of A shown in Figure 1; Figure 3 is a connection schematic diagram of the first embodiment of the connection of each phase of the M-phase stator winding shown in Figure 1; Figure 4 is a connection schematic diagram of the second embodiment of the connection of each phase of the M-phase stator winding shown in Figure 1; Figure 5 is a structural schematic diagram of the first embodiment of the hairpin coil shown in Figure 2; Figure 6 is a structural schematic diagram of the second embodiment of the hairpin coil shown in Figure 2; Figure 7 is a structural schematic diagram of the third embodiment of the hairpin coil shown in Figure 2; Figure 8 is a structural schematic diagram of the fourth embodiment of the hairpin coil shown in Figure 2; Figure 9 is a cross-sectional view along section BB of the first embodiment shown in Figure 1; Figure 10 is a cross-sectional view along section BB of the second embodiment shown in Figure 1; Figure 11 is a cross-sectional view along section BB of the third embodiment shown in Figure 1; Figure 12 is a cross-sectional view along section BB of the fourth embodiment shown in Figure 1; Figure 13 is a cross-sectional view along section BB of the fifth embodiment shown in Figure 1.

[0027] As shown in Figures 1-2, the motor provided in this embodiment of the invention is a three-phase motor, i.e., M=3, which is composed of an annular rotor assembly 1 and an annular stator assembly 2. The rotor assembly 1 includes a rotor core and a shaft 7 made of silicon steel sheets. The number of rotor poles is 8, i.e., P=4. Various rotor magnetic circuit structures can be applied to the high-density hairpin stator of this invention, such as surface-mounted rotor, built-in radial rotor (I type), built-in tangential rotor (Spoke type), multi-layer magnet rotor, hybrid magnetic circuit rotor ("V", "V+I", "V+V", etc.), and Halbach array and other rotor structures.

[0028] The stator assembly 2 includes a stator core 5 and an M-phase stator winding 4. The inner periphery of the stator core has N slots 3 spaced apart and extending radially along the stator core. The M-phase stator winding consists of three-phase stator coils 4 wound on the stator core. Each slot 3 is formed between an adjacent pair of stator teeth 6, with the slot opening being semi-closed. The three-phase stator coils 4 are respectively arranged in each slot 3, and the coils in each slot 3 are arranged in L layers from the inside to the outside along the radial direction of the motor, where L is an even number greater than or equal to 4. In this embodiment of the invention, N=48, L=6 or 4. Taking L=6 as an example, please refer to Figure 2. The coils are arranged in layers 1 to 6 from the outside to the inside along the radial direction of the stator core. Each layer is a straight segment of a hairpin coil 8, which will be described in detail below.

[0029] It should be noted that in the embodiments of the present invention, each phase of the three-phase stator coil includes two sub-windings connected in series or in parallel. Two sub-windings connected in series constitute one branch, and two connected in parallel constitute two branches. The following embodiments will only be described using two branches in parallel as an example. Embodiments with one branch are not illustrated. The present invention does not limit the connection method between the three phases. In one embodiment of the present invention, please refer to Figure 3. The three-phase connection method is a star connection. Specifically, the three phases are phase U, phase V, and phase W. Phase U includes two sub-windings U1 and U2 connected in parallel, phase V includes two sub-windings V1 and V2 connected in parallel, and phase W includes two sub-windings W1 and W2 connected in parallel. The three phases are connected together at one end to form a node N.

[0030] In another embodiment of the present invention, referring to FIG4, the three phases are U phase, V phase and W phase respectively. The U phase includes two parallel sub-windings U1 and U2, the V phase includes two parallel sub-windings V1 and V2, and the W phase includes two parallel sub-windings W1 and W2. The end of each phase is connected to the front end of the subsequent phase, and then the terminal wires are led out from the three connection points.

[0031] The stator assembly proposed in this invention is used for an M-phase motor with a rotor pole number of 2p. It includes a stator core and an M-phase stator winding. The inner periphery of the stator core has N slots that are spaced apart and extend radially along the stator core. The M-phase stator winding is formed by winding multiple hairpin coils in the slots to form L layers. M is a positive integer and L is an even number greater than or equal to 4. In the embodiment of this invention, P=4, M=3, N=48, and L=4 or 6.

[0032] Each phase stator winding includes two sub-windings. For example, in a three-phase system, the sub-windings are U-phase, V-phase, and W-phase. The U-phase includes two parallel or series-connected sub-windings, U1 and U2. The V-phase includes two parallel-connected sub-windings, V1 and V2. The W-phase includes two parallel-connected sub-windings, W1 and W2. Each sub-winding has multiple hairpin coils, which are distributed in L different layers of N slots. The multiple hairpin coils of each sub-winding include a first hairpin coil located in the first layer of the slot, a second hairpin coil located in the Lth layer of the slot, and an intermediate hairpin coil located between the first and Lth layers of the slot. The first hairpin coils of the two sub-windings are short-pitch hairpin coils, and the second hairpin coils of the two sub-windings are long-pitch hairpin coils. The total number of intermediate hairpin coils in the two sub-windings is the same, and the pitch type of the intermediate hairpin coils in the two sub-windings is the same, and their distribution in each pitch type is also the same.

[0033] In the technical solution of this invention, a stator assembly is designed, in which L layers of conductors (L is an even number greater than or equal to 4) are distributed in each slot of the stator core. Two sub-windings are connected in series or in parallel. The first hairpin coil of the two sub-windings is a short-pitch hairpin coil, and the second hairpin coil of the two sub-windings is a long-pitch hairpin coil, so that the hairpin coils of the first layer and the Lth layer correspond to each other. The total number of intermediate hairpin coils of the two sub-windings is the same, the pitch type of the intermediate hairpin coils is the same, and the distribution of each pitch type is also the same, so that the positions of the two sub-windings in the slots correspond, thereby making the back EMF, resistance and inductance of the two sub-windings the same, and the current through the two sub-windings is also the same. In this way, on the one hand, the circulating current generated between the two sub-windings is avoided, thereby significantly reducing the additional AC copper loss at high frequencies, improving the motor efficiency at high speeds, and avoiding local overheating of the windings, thus extending the life of the motor. On the other hand, the electromagnetic noise of the motor is suppressed, the NVH performance is improved, and the motor is more suitable for high-speed applications without increasing the inverter capacity.

[0034] In this embodiment of the invention, multiple hairpin coils of each sub-winding are distributed in L different layers of N slots. The hairpin coils are interconnected to form a sub-winding. Please refer to Figures 5 to 8. According to their shape, hairpin coils can be divided into U-shaped hairpin coils and I-shaped hairpin coils.

[0035] Figure 5 shows an embodiment of a U-shaped hairpin coil. The first U-shaped hairpin coil 12 includes two straight segments 16, a connecting segment 13, a left end 141, and a right end 142, forming an overall U-shape. The two straight segments 16 are inserted into adjacent layers of two slots 3. The left end 141 and right end 142 of the first U-shaped hairpin coil are bent in opposite directions. The first U-shaped hairpin coil 12 is connected to the ends of other hairpin coils by welding on the opposite side of the stator core 5 insertion side.

[0036] Figure 6 shows another embodiment of the U-shaped hairpin coil, the second U-shaped hairpin coil 21, which includes two straight segments 25 of the second U-shaped hairpin coil, a connecting segment 22 of the second U-shaped hairpin coil connecting the two straight segments 25, a left end 231 of the second U-shaped hairpin coil, and a right end 232 of the second U-shaped hairpin coil, forming an overall U-shape. The two straight segments 25 of the second U-shaped hairpin coil are respectively inserted into the same layer of the two slots 3. The left end 231 and the right end 232 of the second U-shaped hairpin coil are bent in the same direction. The first U-shaped hairpin coil 12 is connected to the ends of other hairpin coils by welding on the opposite side of the stator core 5 insertion side.

[0037] Figure 7 shows an embodiment of a type I hairpin coil. The first type I hairpin coil 17 includes a straight section 19, an upper end 18, and a lower end 20, forming an overall I shape. The straight section 19 is inserted into a layer of the slot 3. The upper end 18 and the lower end 20 are bent in opposite directions. The lower end 20 is connected to other hairpin coil ends by welding on the opposite side of the stator core 5 insertion side.

[0038] Figure 8 shows another embodiment of the type I hairpin coil, a second type I hairpin coil 26, which includes a straight section 28, an upper end 27, and a lower end 29, forming an overall I shape. The straight section 28 is inserted into a layer of the slot 3. The upper end 27 and the lower end 29 are bent in the same direction. On the opposite side of the stator core 5 insertion side, the lower end 20 of the straight section 28 of the first type I hairpin coil is connected to the ends of other hairpin coils by welding. In this embodiment, the type I hairpin coil is located at the end of the coil and connected to the lead wire.

[0039] It should be noted that in Figures 5 and 6, reference numerals 15 and 24 represent the pitches of the first and second U-shaped hairpin coils, respectively, indicating the distance between the two straight segments of the hairpin coil, i.e., the number of slots the hairpin coil spans—the pitch. In the stator assembly described above, each sub-winding of each phase stator winding contains coils with three pitches: a full-pitch hairpin coil with a pitch of N / (2P), a long-pitch hairpin coil with a pitch of N / (2P)+1, and a short-pitch hairpin coil with a pitch of N / (2P)-1. In this embodiment of the invention, the total number of intermediate hairpin coils in the two sub-windings is the same, the pitch type of the intermediate hairpin coils is the same, and the distribution of each pitch type is also the same. This indicates that the number, pitch type, and distribution of the hairpin coils used in the intermediate hairpin coils of the two sub-windings are the same. Through the above arrangement, switching between adjacent slots under the same rotor magnetic pole can be achieved, eliminating the phase difference caused by a slot pitch.

[0040] Furthermore, in this embodiment of the invention, referring to Figures 9 to 12, preferably, in the first layer of the slot, the short-pitch hairpin coils distributed on the two sub-windings are arranged in pairs, and the two short-pitch hairpin coils are arranged with a slot between them.

[0041] Similarly, in the Lth layer of the slot, the long-pitch hairpin coils distributed on the two sub-windings are arranged in pairs, and the two long-pitch hairpin coils are arranged to cross one slot.

[0042] The present invention does not limit the form of the intermediate hairpin coil, as long as the total number of intermediate hairpin coils of the two sub-windings is the same, the pitch type of the intermediate hairpin coils is the same, and the distribution of each pitch type is also the same. Preferably, the intermediate hairpin coil may include a full-pitch hairpin coil; the intermediate hairpin coil may also include a long-pitch hairpin coil and a short-pitch hairpin coil.

[0043] Taking L=6 as an example, the distribution of the intermediate hairpin coils is explained below. The multiple intermediate hairpin coils include: a first intermediate hairpin coil, distributed in the second and third layers of the slot, with the two straight segments of the first intermediate hairpin coil located in the second and third layers of the slot respectively; and a second intermediate hairpin coil, distributed in the fourth and fifth layers of the slot, with the two straight segments of the second intermediate hairpin coil located in the fourth and fifth layers of the slot respectively. The total number of the first intermediate hairpin coils in the two sub-windings is equal, and the total number of the second intermediate hairpin coils is also equal.

[0044] In the first embodiment of the intermediate hairpin coil of the present invention, i.e., when the intermediate hairpin coil includes a long-pitch hairpin coil and a short-pitch hairpin coil, please refer to FIG9. One of the first intermediate hairpin coils of the two sub-windings is a long-pitch hairpin coil and the other is a short-pitch hairpin coil. The long-pitch hairpin coil and the short-pitch hairpin coil distributed on the two sub-windings are arranged in pairs, with the long-pitch hairpin coil wrapped around the short-pitch hairpin coil. One of the second intermediate hairpin coils of the two sub-windings is a corresponding long-pitch hairpin coil and the other is a short-pitch hairpin coil. The long-pitch hairpin coil and the short-pitch hairpin coil distributed on the two sub-windings are arranged in pairs, with the long-pitch hairpin coil wrapped around the short-pitch hairpin coil.

[0045] Specifically, taking the U phase as an example, please refer to Figure 9. 48 slots are formed at intervals on the inner periphery of the stator core 5 and extend radially along the stator core, i.e., N=48. The reference numerals 1, 2, 3...47, 48 in Figure 9 indicate the slot numbers.

[0046] Please refer to Figure 9 for the first winding U1 of phase U, which includes coil groups U11, U12, U14, U16, U15, and U13 distributed in layers 1, 2, 4, 6, 5, and 3, totaling 24 series-connected coils. Each coil group contains 4 coils. The lead U1+ of the first winding U1 is located in layer 1, and the neutral lead U1- is also located in layer 1. The first winding U1 includes an I-type hairpin coil 111 inserted into slot 1 of the first layer, a coil 121 inserted into slot 7 of the second layer and slot 14 of the third layer, a coil 141 inserted into slot 20 of the fourth layer and slot 25 of the fifth layer, a coil 161 inserted into slot 31 of the sixth layer and slot 38 of the sixth layer, a coil 151 inserted into slot 32 of the fifth layer and slot 25 of the fourth layer, and a coil 131 inserted into slot 19 of the third layer and slot 14 of the second layer. Coil 112 is inserted into slot 8 and slot 13 of layer 1; coil 122 is inserted into slot 19 of layer 2 and slot 26 of layer 3; coil 142 is inserted into slot 32 of layer 4 and slot 37 of layer 5; coil 162 is inserted into slot 43 and slot 2 of layer 6; coil 152 is inserted into slot 44 of layer 5 and slot 37 of layer 4; coil 132 is inserted into slot 31 of layer 3 and slot 26 of layer 2; coil 112 is inserted into slot 1... Coil 113, inserted into slot 20 of layer 1 and slot 25 of layer 1; coil 123, inserted into slot 31 of layer 2 and slot 38 of layer 3; coil 143, inserted into slot 44 of layer 4 and slot 1 of layer 5; coil 163, inserted into slot 7 of layer 6 and slot 14 of layer 6; coil 153, inserted into slot 8 of layer 5 and slot 1 of layer 4; coil 133, inserted into slot 43 of layer 3 and slot 38 of layer 2; coil 143, inserted into slot 32 of layer 1 and slot 25 of layer 6; coil 123, inserted into slot 31 of layer 2 and slot 38 of layer 3; coil 123, inserted into slot 44 of layer 4 and slot 1 of layer 5; coil 143, inserted into slot 7 of layer 6 and slot 14 of layer 6; coil 153, inserted into slot 8 of layer 5 and slot 1 of layer 4; coil 133, inserted into slot 43 of layer 3 and slot 38 of layer 2; coil 143, inserted into slot 32 of layer 1 and slot 25 of layer 6; coil 153, inserted into slot 8 of layer 5 and slot 1 of layer 4; coil 163, inserted into slot 44 of layer 6 and slot 14 of layer 6; coil 153, inserted into slot 8 of layer 5 and slot 1 of layer 4; coil 163, inserted into slot 43 of layer 3 and slot 38 of layer 2; coil 163, inserted into slot 32 of layer 1 and slot 25 of layer 6; coil 163, inserted into slot 7 of layer 6 and slot 14 of layer 6; coil 163, inserted into slot 7 of layer 6 and slot 14 of layer 6; coil 16 Coil 114 is inserted into slot 37 of layer 1; coil 124 is inserted into slot 43 of layer 2 and slot 2 of layer 3; coil 144 is inserted into slot 8 of layer 4 and slot 13 of layer 5; coil 164 is inserted into slot 19 of layer 6 and slot 26 of layer 6; coil 154 is inserted into slot 20 of layer 5 and slot 13 of layer 4; coil 134 is inserted into slot 7 of layer 3 and slot 2 of layer 2; and I-shaped coil 115 is inserted into slot 44 of layer 1. All I-shaped and U-shaped coils are connected together by welding at the ends, forming winding U1. Please refer to the second winding U2 of phase U in Figure 9, which includes coil groups U21, U22, U24, U26, U25, and U23 distributed in layers 1, 2, 4, 6, 5, and 3, totaling 24 series-connected coils. Each coil group contains 4 coils. The second winding U2 lead U2+ is located in the first layer, and the neutral lead U2- is located in the first layer.The second winding U2 includes an I-type hairpin coil 211 inserted into slot 2 of layer 1, a coil 221 inserted into slot 8 of layer 2 and slot 13 of layer 3, a coil 241 inserted into slot 19 of layer 4 and slot 26 of layer 5, a coil 261 inserted into slot 32 of layer 6 and slot 25 of layer 6, a coil 251 inserted into slot 19 of layer 5 and slot 14 of layer 4, and a coil 231 inserted into slot 8 of layer 3 and slot 1 of layer 2. Coil 212 is inserted into slot 43 and slot 38 of layer 1; coil 222 is inserted into slot 44 of layer 2 and slot 1 of layer 3; coil 242 is inserted into slot 7 of layer 4 and slot 14 of layer 5; coil 262 is inserted into slot 20 and slot 13 of layer 6; coil 252 is inserted into slot 7 of layer 5 and slot 2 of layer 4; coil 232 is inserted into slot 44 of layer 3 and slot 37 of layer 2; coil 212 is inserted into slot 31 of layer 1. Coil 213 is inserted into slot 213 of layer 1 and slot 26 of layer 2; coil 223 is inserted into slot 32 of layer 2 and slot 37 of layer 3; coil 243 is inserted into slot 43 of layer 4 and slot 2 of layer 5; coil 263 is inserted into slot 8 of layer 6 and slot 1 of layer 6; coil 253 is inserted into slot 43 of layer 5 and slot 38 of layer 4; coil 233 is inserted into slot 32 of layer 3 and slot 25 of layer 2; and coil 233 is inserted into slot 19 of layer 1 and slot 1 of layer 1. Coil 214 in slot 4, coil 224 in slot 20 of layer 2 and slot 25 of layer 3, coil 244 in slot 31 of layer 4 and slot 38 of layer 5, coil 264 in slot 44 of layer 6 and slot 37 of layer 6, coil 254 in slot 31 of layer 5 and slot 26 of layer 4, coil 234 in slot 20 of layer 3 and slot 13 of layer 2, and I-shaped coil 215 in slot 7 of layer 1. All I-shaped and U-shaped coils are connected together by welding their ends, forming winding U2 in series.

[0047] The aforementioned end welding can be performed using single-end welding, double-end welding, or continuous beading (without welding).

[0048] In the above embodiment, the total number of long-pitch hairpin coils and the total number of short-pitch hairpin coils in the middle hairpin coils of the two sub-windings are equal. Since the total number of long-pitch hairpin coils in the first layer and the Lth layer of the two sub-windings are equal, and the total number of short-pitch hairpin coils are also equal, the total number of long-pitch hairpin coils and the total number of short-pitch hairpin coils in the two sub-windings are equal, making the positions of the two sub-windings correspond in the slots. Consequently, the back EMF, resistance, and inductance of the two sub-windings are the same, and the current through the two sub-windings is also the same.

[0049] The present invention does not restrict the position of the voltage lead and neutral lead of each sub-winding. In this embodiment, the voltage lead and neutral lead of each sub-winding are located in the first layer of the slot at the same time. For example, the voltage lead U1+ and neutral lead U1- of U1 are both in the first layer. In other embodiments, it is obvious that the voltage lead and neutral lead of each sub-winding are located in the Lth layer of the slot at the same time, which facilitates wiring.

[0050] Furthermore, in the second embodiment of the intermediate hairpin coil, referring to Figure 10, in another embodiment, the voltage lead and neutral lead of each sub-winding are located in the second and third layers of the slot, respectively. That is, the voltage lead U1+ is located in slot 14 of the third layer, the neutral lead U1- is located in slot 7 of the second layer, the voltage lead U2+ is located in slot 13 of the third layer, and the neutral lead U2- is located in slot 8 of the second layer.

[0051] In the fifth embodiment of the intermediate hairpin coil, as shown in Figure 13, the voltage lead and neutral lead of each sub-winding are located in the second layer and the first layer of the slot, respectively.

[0052] Similarly, in the third type of U-phase input / output connection, the voltage lead U1+ is located in slot 26 of layer 5, the neutral lead U1- is located in slot 19 of layer 4, the voltage lead U2+ is located in slot 25 of layer 5, and the neutral lead U2- is located in slot 20 of layer 4.

[0053] It should be noted that each phase stator winding of the present invention includes two sub-windings. The two sub-windings can be connected in series to form one path or connected in parallel to form two paths. When connected in series, the U1- lead wire and the U2+ lead wire are connected to each other. Therefore, the U-phase lead wires are U1+ and U2-, realizing the case of one path. The structure is simple and highly flexible.

[0054] Furthermore, since the stator assembly is annular, the distribution of the hairpin coils in different slots essentially spans different radii. Therefore, the distance between the two straight segments of the hairpin coils at different positions will be different. That is, the distance between the two straight segments of the long-pitch hairpin coils distributed between the second and third layers is different from that of the long-pitch hairpin coils distributed between the fourth and fifth layers; similarly, the distance between the two straight segments of the short-pitch hairpin coils distributed between the second and third layers is different from that of the short-pitch hairpin coils distributed between the fourth and fifth layers.

[0055] In this embodiment of the invention, the first intermediate hairpin coil includes a first long-pitch hairpin coil and a first short-pitch hairpin coil, and the second intermediate hairpin coil includes a second long-pitch hairpin coil and a second short-pitch hairpin coil. Both the first and second long-pitch hairpin coils are long-pitch coils, and both the first and second short-pitch hairpin coils are short-pitch coils. The total number of the first long-pitch hairpin coil, the first short-pitch hairpin coil, the second long-pitch hairpin coil, and the second short-pitch hairpin coil in both sub-windings is equal. That is, in this invention, the intermediate layer uses (N-2) / 2 types of long-pitch hairpin coils and (N-2) / 2 types of short-pitch hairpin coils. In this embodiment, the intermediate layer uses two types of long-pitch hairpin coils and two types of short-pitch hairpin coils, which can further eliminate the differences between the two sub-windings and achieve identical back EMF, resistance, and inductance between the two sub-windings.

[0056] In the third embodiment of the intermediate hairpin coil of the present invention, that is, when the intermediate hairpin coil includes a full-pitch hairpin coil, please refer to FIG11. The first intermediate hairpin coil and the second intermediate hairpin coil are both full-pitch hairpin coils, and the total number of full-pitch hairpin coils in the two sub-windings is equal.

[0057] Specifically, taking the U phase as an example, 48 slots are formed at intervals on the inner periphery of the stator core 5 and extend radially along the stator core, i.e., N=48. The reference numerals 1, 2, 3...47, 48 in Figure 11 indicate the slot numbers.

[0058] Referring to Figure 11, the first winding U1 includes coil groups U11, U12, U14, U16, U15, and U13; the second winding U2 includes coil groups U21, U22, U24, U26, U25, and U23. The U-phase first sub-winding U1 lead U1+ is located in the first layer, and the neutral lead U1- is also located in the first layer. The first winding U1 includes hairpin coils 111, 121, 141, 161, 151, 131, 112, 122, 142, 162, 152, 132, 113, 123, 143, 163, 153, 133, 114, 124, 144, 164, 154, 134, and 115. Each type I coil and type U coil is connected together by welding at the ends of the coils, forming a series winding U1.

[0059] Referring to Figure 11, the U-phase second sub-winding U2's lead U2+ is located on the first layer, and the neutral lead U2- is also located on the first layer. The second winding U2 includes hairpin coils 211, 221, 241, 261, 251, 231, 212, 222, 242, 262, 252, 232, 213, 223, 243, 263, 253, 233, 214, 224, 244, 264, 254, 234, and 215. All I-type and U-type coils are connected together by welding at their ends, forming winding U2 in series.

[0060] In the above embodiments, the total number of full-pitch hairpin coils in the intermediate hairpin coils of the two sub-windings is equal. Since the total number of long-pitch hairpin coils in the first and Lth layers of the two sub-windings is equal, and the total number of short-pitch hairpin coils is also equal, the total number of hairpin coils in the two sub-windings is equal. This ensures that the total number of hairpin coils in the two sub-windings is the same, the corresponding pitch type is the same, and the distribution of each pitch type is also the same. This makes the positions of the two sub-windings correspond in the slots, resulting in the same back EMF, resistance, and inductance of the two sub-windings, and the same current flowing through the two sub-windings. Furthermore, since the hairpin coils in the intermediate layer are all full-pitch hairpin coils, the number of pitch types of U-shaped hairpin coils used is reduced, the number of manufacturing molds is reduced, costs are lowered, and manufacturing efficiency is improved.

[0061] Furthermore, since the stator assembly is annular, the distribution of the hairpin coils in different slots essentially spans different radii. Therefore, the distance between the two straight segments of the full-pitch hairpin coils will be different at different positions. That is, the distance between the two straight segments of the full-pitch hairpin coils distributed between the second and third layers is different from that of the full-pitch hairpin coils distributed between the fourth and fifth layers.

[0062] In this embodiment, the full-pitch hairpin coil of the first intermediate hairpin coil is a first full-pitch hairpin coil, and the full-pitch hairpin coil of the second intermediate hairpin coil is a second full-pitch hairpin coil. The total number of first full-pitch hairpin coils in both sub-windings is equal, and the total number of second full-pitch hairpin coils is also equal. That is, in this invention, the intermediate layer uses (N-2) / 2 types of full-pitch hairpin coils, i.e., in this embodiment, the intermediate layer uses two types of full-pitch hairpin coils, which can further eliminate the differences between the two sub-windings and achieve the same back EMF, resistance, and inductance in the two sub-windings.

[0063] In the fourth embodiment of the intermediate hairpin coil of the present invention, please refer to Figure 12, L=4, the plurality of intermediate hairpin coils include: full-pitch hairpin coils, distributed in the second and third layers of the slot, the two straight segments of the full-pitch hairpin coils are respectively located in the second and third layers of the slot, and the total number of full-pitch hairpin coils in the two sub-windings is equal.

[0064] Specifically, taking the U phase as an example, please refer to Figure 12. 48 slots are formed at intervals on the inner periphery of the stator core 5 and extend radially along the stator core, i.e., N=48. The reference numerals 1, 2, 3...47, 48 in Figure 12 indicate the slot numbers.

[0065] Specifically, referring to Figure 12, each slot contains four conductor layers. The first winding U1 includes coil groups U11, U12, U14, and U13; the second winding U2 includes coil groups U21, U22, U24, and U23. The U-phase first sub-winding U1 lead U1+ is located on the third layer, and the neutral lead U1- is located on the second layer. The first winding U1 includes hairpin coils 131, 141, 132, 111, 121, 142, 133, 112, 122, 143, 134, 113, 123, 144, 135, 114, and 124. The various I-type and U-type coils are connected together by welding at their ends, forming winding U1 in series.

[0066] The U-phase second winding U2's lead-out line U2+ is located on the third layer, and the neutral lead-out line U2- is located on the second layer. The second winding U2 includes hairpin coils 231, 241, 232, 211, 221, 242, 233, 212, 222, 243, 234, 213, 223, 244, 235, 214, and 224. All I-type and U-type coils are connected together in series via welding at their ends to form winding U2.

[0067] In the above embodiments, the total number of full-pitch hairpin coils in the intermediate hairpin coils of the two sub-windings is equal. Since the total number of long-pitch hairpin coils in the first and Lth layers of the two sub-windings is equal, and the total number of short-pitch hairpin coils is also equal, the total number of hairpin coils in the two sub-windings is equal. This ensures that the total number of hairpin coils in the two sub-windings is the same, the corresponding pitch type is the same, and the distribution of each pitch type is also the same. This makes the positions of the two sub-windings correspond in the slots, resulting in the same back EMF, resistance, and inductance of the two sub-windings, and the same current flowing through the two sub-windings. Furthermore, since the hairpin coils in the intermediate layer are all full-pitch hairpin coils, the number of pitch types of U-shaped hairpin coils used is reduced, the number of manufacturing molds is reduced, costs are lowered, and manufacturing efficiency is improved.

[0068] In the fifth embodiment of the intermediate hairpin coil of the present invention, please refer to Figure 13, L=4, the plurality of intermediate hairpin coils include: full-pitch hairpin coils, distributed in the second and third layers of the slot, the two straight segments of the full-pitch hairpin coils are respectively located in the second and third layers of the slot, and the total number of full-pitch hairpin coils in the two sub-windings is equal.

[0069] Specifically, taking the U phase as an example, please refer to Figure 13. 48 slots are formed at intervals on the inner periphery of the stator core 5 and extend radially along the stator core, i.e., N=48. The reference numerals 1, 2, 3...47, 48 in Figure 13 indicate the slot numbers.

[0070] Specifically, referring to Figure 13, each slot contains four conductor layers. The first winding U1 includes coil groups U11, U12, U14, and U13; the second winding U2 includes coil groups U21, U22, U24, and U23. The U-phase first sub-winding U1 lead U1+ is located on the second layer, and the neutral lead U1- is located on the first layer. The axial position of lead U1+ is opposite to the U-shaped hairpin coil connection section, and the axial position of neutral lead U1- is also opposite to the U-shaped hairpin coil connection section. Therefore, the wire output method in this embodiment eliminates the use of the I-type hairpin coil, reducing the types of wires, decreasing the number of manufacturing molds, lowering costs, and improving processing and manufacturing efficiency. The first winding U1 includes hairpin coil 121, coil 141, coil 131, coil 111, coil 122, coil 142, coil 132, coil 112, coil 123, coil 143, coil 133, coil 113, coil 124, coil 144, coil 134, and coil 114. The individual U-shaped coils are connected together in series via welding at their ends to form winding U1.

[0071] The second set of sub-windings U2 of phase U2 has its lead U2+ located on the second layer, and its neutral lead U2- located on the first layer. The second set of windings U2 includes hairpin coils 221, 241, 231, 211, 222, 242, 232, 212, 223, 243, 233, 213, 224, 244, 234, and 214. These U-shaped coils are connected together by welding their ends, forming winding U2 in series.

[0072] In the fourth and fifth embodiments of the intermediate hairpin coil of this invention, the first layer of the slot uses a short-pitch hairpin coil, the second and third layers use a full-pitch hairpin coil, and each phase occupies two adjacent slots, such as slots 7 and 8. The winding pitch factor is 1, which can output greater torque. The fourth layer uses a long-pitch hairpin coil. There are three types of U-shaped hairpin coils with short end heights, resulting in a small motor size. The number of parallel branches per phase is one or two. When there are two parallel branches, the combination of short-pitch and long-pitch hairpin coils enables switching between adjacent slots under the same rotor magnetic pole, eliminating the phase difference caused by a slot pitch, avoiding circulating current between the two branches, and preventing excessive local temperature rise. When there are two parallel branches, the number of series turns per phase is lower, which is suitable for low-voltage, high-current, and high-speed applications. When there is one parallel branch per phase, the number of series turns per phase is higher, which is suitable for high-voltage, low-current, and low-speed applications.

[0073] Furthermore, when L=4, the intermediate hairpin coil can also be a long-pitch hairpin coil and a short-pitch hairpin coil. Specifically, the intermediate hairpin coil includes a third intermediate hairpin coil, which is distributed in the second and third layers of the slot. The two straight segments of the third intermediate hairpin coil are located in the second and third layers of the slot, respectively. The total number of the third intermediate hairpin coils in the two sub-windings is equal. One of the third intermediate hairpin coils in the two sub-windings is a long-pitch hairpin coil, and the other is a short-pitch hairpin coil. The long-pitch hairpin coils and short-pitch hairpin coils distributed on the two sub-windings are arranged in pairs, with the long-pitch hairpin coil wrapped around the short-pitch hairpin coil.

[0074] One of the third intermediate hairpin coils in the two sub-windings is a long-pitch hairpin coil, and the other is a short-pitch hairpin coil. The long-pitch and short-pitch hairpin coils distributed on the two sub-windings are arranged in pairs, with the long-pitch hairpin coil wrapped around the short-pitch hairpin coil. That is, in this invention, the intermediate layer uses (N-2) / 2 types of long-pitch hairpin coils and (N-2) / 2 types of short-pitch hairpin coils. In this embodiment, the intermediate layer uses one type of long-pitch hairpin coil and one type of short-pitch hairpin coil, which can further eliminate the differences between the two sub-windings and achieve identical back EMF, resistance, and inductance between the two sub-windings.

[0075] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A stator assembly, characterized in that, An M-phase motor with 2p rotor poles includes a stator core and an M-phase stator winding. The inner periphery of the stator core has N slots spaced apart and extending radially along the stator core. The M-phase stator winding is formed by multiple hairpin coils wound in the slots to form L layers. The slots are arranged sequentially from the first layer to the Lth layer along the radial direction of the stator core. M is a positive integer, and L is an even number greater than or equal to 4. Each phase of the stator winding includes two sub-windings connected in parallel or in series. Each sub-winding has multiple hairpin coils. The multiple hairpin coils of each sub-winding are distributed in L different layers of the N slots, such that the multiple hairpin coils of each sub-winding include a first hairpin coil located in the first layer of the slot, a second hairpin coil located in the Lth layer of the slot, and an intermediate hairpin coil located between the first layer and the Lth layer of the slot. Wherein, the first hairpin coil of the two sub-windings is a short-pitch hairpin coil, and the second hairpin coil of the two sub-windings is a long-pitch hairpin coil; the total number of the intermediate hairpin coils of the two sub-windings is the same, and the pitch type of the intermediate hairpin coils of the two sub-windings is the same, and the distribution of each pitch type is also the same; the total number of the hairpin coils of the two sub-windings is the same, and the pitch type of the hairpin coils of the two sub-windings is the same, so that the positions of the two sub-windings in the slots correspond; the hairpin coil includes a straight segment inserted into the slot, the straight segment of the two hairpin coils connected is located in two adjacent layers of different slots, and the span of the straight segment of the two hairpin coils connected in the plurality of hairpin coils is the same, the span being the number of slots crossed by the straight segment of the two connected hairpin coils.

2. The stator assembly as claimed in claim 1, characterized in that, In the first layer of the slot, the short-pitch hairpin coils distributed on the two sub-windings are arranged in pairs, and the two short-pitch hairpin coils are spaced apart by one slot; and / or, in the Lth layer of the slot, the long-pitch hairpin coils distributed on the two sub-windings are arranged in pairs, and the two long-pitch hairpin coils are arranged intersecting by one slot.

3. The stator assembly as claimed in claim 1, characterized in that, The intermediate hairpin coil includes a short-pitch hairpin coil with a pitch of N / (2P)-1 and a span of N / (2P)-1 between the straight segments of two connected hairpin coils.

4. The stator assembly as claimed in claim 3, characterized in that, The L=4, the hairpin coil includes two parallel straight segments and a connecting segment connecting the two straight segments, the plurality of intermediate hairpin coils include: short-pitch hairpin coils, distributed in the second and third layers of the slot, the two straight segments of the short-pitch hairpin coils are respectively located in the second and third layers of the slot, the total number of short-pitch hairpin coils in the two sub-windings is equal; the straight segment of the first hairpin coil located in the first layer is connected to the straight segment of the intermediate hairpin coil located in the second layer, then the span between the two straight segments is N / (2P)-1; the straight segment of the second hairpin coil located in the fourth layer is connected to the straight segment of the intermediate hairpin coil located in the third layer, then the span between the two straight segments is N / (2P)-1.

5. The stator assembly as claimed in claim 3, characterized in that, The hairpin coil includes two parallel straight segments and a connecting segment connecting the two straight segments, where L=6. The plurality of intermediate hairpin coils include: a first short-pitch hairpin coil, distributed in the second and third layers of the slot, with the two straight segments of the first short-pitch hairpin coil located in the second and third layers of the slot, respectively; and a second short-pitch hairpin coil, distributed in the fourth and fifth layers of the slot, with the two straight segments of the second short-pitch hairpin coil located in the fourth and fifth layers of the slot, respectively. The total number of the first short-pitch hairpin coils in the two sub-windings is equal, and the total number of the second short-pitch hairpin coils is also equal. If the straight segment of the first hairpin coil in the first layer is connected to the straight segment of the first short-pitch hairpin coil in the second layer, then the span between the two straight segments is N / (2P)-1; if the straight segment of the first short-pitch hairpin coil in the third layer is connected to the straight segment of the second short-pitch hairpin coil in the fourth layer, then the span between the two straight segments is N / (2P)-1; if the straight segment of the second short-pitch hairpin coil in the fifth layer is connected to the straight segment of the second hairpin coil in the sixth layer, then the span between the two straight segments is N / (2P)-1.

6. The stator assembly as claimed in claim 3, characterized in that, The hairpin coil includes two parallel straight segments and a connecting segment connecting the two straight segments, where L=8. The plurality of intermediate hairpin coils include: a first short-pitch hairpin coil, distributed in the second and third layers of the slot, with its two straight segments located in the second and third layers of the slot respectively; a second short-pitch hairpin coil, distributed in the fourth and fifth layers of the slot, with its two straight segments located in the fourth and fifth layers of the slot respectively; and a third short-pitch hairpin coil, distributed in the sixth and seventh layers of the slot, with its two straight segments located in the sixth and seventh layers of the slot respectively. The total number of the first short-pitch hairpin coils in the two sub-windings is equal, the total number of the second short-pitch hairpin coils is equal, and the total number of the third short-pitch hairpin coils is also equal. If the straight segment of the first hairpin coil in the first layer is connected to the straight segment of the first short-pitch hairpin coil in the second layer, then the span between the two straight segments is N / (2P)-1; if the straight segment of the first short-pitch hairpin coil in the third layer is connected to the straight segment of the second short-pitch hairpin coil in the fourth layer, then the span between the two straight segments is N / (2P)-1; if the straight segment of the second short-pitch hairpin coil in the fifth layer is connected to the straight segment of the third short-pitch hairpin coil in the sixth layer, then the span between the two straight segments is N / (2P)-1; if the straight segment of the third short-pitch hairpin coil in the seventh layer is connected to the straight segment of the second hairpin coil in the eighth layer, then the span between the two straight segments is N / (2P)-1.

7. The stator assembly as claimed in claim 1, characterized in that, Each of the sub-windings has a plurality of connected U-shaped hairpin coils and two I-shaped hairpin coils connected to both ends of the plurality of U-shaped hairpin coils, with the two I-shaped hairpin coils respectively leading out a voltage lead and a neutral lead; or, each of the sub-windings has a plurality of connected U-shaped hairpin coils, with the two U-shaped hairpin coils located at both ends of the sub-winding respectively leading out a voltage lead and a neutral lead.

8. The stator assembly as claimed in claim 1 or 7, characterized in that, When two sub-windings are connected in series, each sub-winding has two U-shaped hairpin coils at both ends. One U-shaped hairpin coil on each sub-winding leads out a voltage lead, and the other U-shaped hairpin coil leads out a neutral lead. The voltage lead of one sub-winding is electrically connected to the neutral lead of the other sub-winding. When two sub-windings are connected in series, each sub-winding has two I-shaped hairpin coils at both ends. One I-shaped hairpin coil on each sub-winding leads out a voltage lead, and the other I-shaped hairpin coil leads out a neutral lead. The voltage lead of one sub-winding is electrically connected to the neutral lead of the other sub-winding. When two sub-windings are connected in series, one end of each sub-winding is connected by a U-shaped hairpin coil, and the other end of each sub-winding is provided with an I-shaped hairpin coil to lead out a voltage lead and a neutral lead, respectively.

9. An electric motor, characterized in that, Includes the stator assembly as described in any one of claims 1 to 8.

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