A connection method of a 324-slot 18-pole symmetrical four-branch double-layer three-phase winding

Abstract

The application discloses a connection method of a 324-slot 18-pole symmetrical four-branch double-layer three-phase winding, and belongs to the technical field of three-phase double-layer winding connection, which comprises the following steps: considering 648 wire bars as potential vectors, dividing the wire bars into six phase bands of A, Z, B, X, C and Y by using 60-degree standard phase bands, and dividing the potential vectors of the corresponding phase bands of the same phase into four parts to form four branches; the wire bars of the same phase are connected in series at the heads and connected in series at the tails, and the four branches of each phase are connected in parallel to form U, V and W three-phase symmetrical four-branch double-layer windings. The application adopts short-distance coils to naturally connect the upper and lower wire bars, and cross-connects partial branches to realize the symmetry of branch potential; controllable micro circulation is introduced through the overlapping winding to concentrate the winding, the electromagnetic stiffness of the motor is reduced, the rotor eccentricity is inhibited, the dynamic stability of the unit is improved, the potential waveform is optimized, and the operation requirement of a 320MW-level pumped storage unit at high altitude is adapted.

Description

Technical Field

[0001] This invention relates to the field of three-phase double-layer symmetrical winding connection, and more particularly to a connection method for a 324-slot, 18-pole symmetrical four-branch double-layer three-phase winding. Background Technology

[0002] Pumped storage power stations have functions such as peak shaving and valley filling, phase regulation, frequency regulation, and emergency backup. Pumped storage motors operate in both generating and motoring modes, characterized by frequent start-stop cycles, bidirectional rotation, and high speeds, making their design challenging. The superior performance of the pump-turbine in a 320MW pumped storage unit with a speed of 333.3 r / min (18 poles) has led to its widespread application. However, for 18-pole motors, when the stator windings are connected in a conventional integer slot symmetrical configuration, the number of available branches is limited to 1, 2, 3, 6, 9, and 18. For some power stations at altitudes exceeding 3500m, when the rated voltage of the unit is selected to be above 18kV, the stator corona protection voltage after altitude correction approaches 28kV. Currently, there is no domestic experience in the application of 28kV voltage-level corona protection motors; therefore, the stator voltage of this type of generator is generally controlled at 18kV or below. When the motor capacity reaches 320MW, selecting 1 or 2 branches results in stator slot currents far exceeding the maximum limits of existing air-cooled technology; selecting 6, 9, or 18 branches results in excessively low stator slot currents; and selecting 3 branches results in a stator slot current of approximately 7603A, also exceeding the conventional hydropower stator slot current limit of 7500A. Furthermore, the ventilation conditions deteriorate at high altitudes, making it crucial to control the stator slot current within a reasonable range. Using 4 branches, the stator slot current is comparable to that of most existing pumped storage units, ensuring unit operating performance while reducing motor performance and power plant construction costs.

[0003] In existing technologies, the connection of three-phase double-layer windings typically involves first calculating the number of unit motors and winding cycles, and then drawing a star diagram. The potential vectors of the star diagram are divided into six phase bands, and the composite vectors of each phase band differ by 120° before drawing the stator winding connection diagram. However, for a 324-slot, 18-pole motor, the conventional star diagram drawing method can only yield 9 layers of potential vectors, with only 18 overlapping vectors per phase. This makes it impossible to evenly divide the circuit into 4 groups of symmetrical branches, making it difficult to directly achieve a symmetrical four-branch connection.

[0004] Chinese invention patent application CN119051318A (publication date: November 29, 2024), entitled "Wiring Method of 264-Slot 22-Pole Symmetrical Four-Branch Double-Layer Three-Phase Winding," discloses a method to achieve symmetrical windings with specific slot-pole combinations through special wiring. However, it uses integer slot full-pitch coil wiring, resulting in high potential waveform distortion and poor power quality. To improve power quality, there are also solutions using short-pitch connections, such as Chinese invention patent application CN115395696A (publication date: November 25, 2022), entitled "A Standard Phase Integer Slot Short-Pitch Wave Winding 4-Branch Wiring Method." This solution uses a wave winding connection method, with distributed windings. Each branch is distributed along the entire circumference of the stator, and there is an overlapping area between the coil positions of each branch. While this structure makes the induced electromotive forces of each branch similar when the rotor is eccentric, and makes it less likely to generate harmful circulating currents caused by branch asymmetry, it also brings new problems: the lack of potential difference between branches makes it impossible to form a controllable micro-circulating current that actively counteracts the unevenness of the air gap, and the electromagnetic stiffness is high; when the rotor is initially eccentric, the unbalanced magnetic pull cannot be effectively suppressed at the electrical level, and may instead exacerbate the degree of eccentricity, leading to an increase in generator swing and a decrease in dynamic stability.

[0005] Therefore, it is necessary to provide a wiring method that can achieve symmetrical four-branch wiring with 324 slots and 18 poles, while taking into account the potential waveform quality and branch symmetry. Summary of the Invention

[0006] To address the issues of high waveform distortion in full-pitch windings and high electromagnetic stiffness in short-pitch windings (which, while improving waveform, lack controllable circulating current), this invention provides a wiring method for a 324-slot, 18-pole symmetrical four-branch double-layer three-phase winding. By employing a lap-wound concentrated winding structure, not only is a symmetrical four-branch wiring of the 324-slot, 18-pole winding achieved, but also, through the concentrated arrangement of branches along the stator circumference, potential differences naturally arise in each branch when the rotor is eccentric. This actively introduces controllable micro-circulating currents, reducing the motor's electromagnetic stiffness while ensuring waveform quality, achieving self-suppression of rotor eccentricity, and improving the dynamic stability of the unit.

[0007] To achieve the above-mentioned objectives, the technical solution of the present invention is as follows: A wiring method for a 324-slot, 18-pole symmetrical four-branch double-layer three-phase winding includes the following steps: S1. The potential vectors of the 648 stator winding bars are considered as separate vectors; S2. Divide all potential vectors into six phase zones: A, Z, B, X, C, and Y, according to the 60° standard phase zone. S3. Divide the potential vectors contained in the corresponding phase bands A and X, B and Y, C and Z of the same phase into 4 equal parts. Each part is added in series to form a branch of potential vector combination, so that each phase gets 4 branches. Since each phase has a total of 36 layers of overlapping potential vectors, after being divided into 4 branches, each branch is allocated an average of 9 layers of overlapping potential vectors. S4. Using short-pitch coils, 8 of the 9 layers of overlapping potential vectors in each branch are naturally connected to the upper and lower layers of wire bars according to the winding pitch, and the remaining 1 layer is connected by special electrical angle crossing. S5. Connect the bars in the corresponding phases A and X, B and Y, C and Z in the same direction by connecting the head to the tail and the tail to the head, to ensure that the potentials of the bars are added together. S6. Connect the four branches of each phase in parallel to form a U, V, W three-phase symmetrical four-branch double-layer three-phase winding.

[0008] Furthermore, in step S3, each phase and each branch is allocated an average of 9 layers of overlapping potential vectors, with each phase carrying six corresponding electrical angles.

[0009] Furthermore, the special connection of the electrical angle crossing includes: each phase with a first electrical angle upper layer bar connected to a second electrical angle lower layer bar, and the second electrical angle upper layer bar connected to the first electrical angle lower layer bar; the third, fourth, fifth, and sixth electrical angle upper layer bars are naturally connected to their respective lower layer bars of the same electrical angle; the first electrical angle is connected, the second electrical angle lower layer bar is connected to the third electrical angle upper layer bar, and then the third electrical angle lower layer bar is connected to the sixth electrical angle upper layer bar, and a branch is formed together with the 8 layers of overlapping potentials naturally connected in this branch; the second electrical angle upper layer bar is connected, the first electrical angle lower layer bar is connected to the fourth electrical angle upper layer bar, and then the fourth electrical angle lower layer bar is connected to the fifth electrical angle upper layer bar, and a branch is formed together with the 8 layers of overlapping potentials naturally connected in this branch.

[0010] Furthermore, the short-pitch coefficient of the short-pitch coil is 0.833, and the winding pitch is 15 slots.

[0011] Furthermore, when wiring, in the case of cross-mechanical angle connection, open the upper and lower layer bars at the same position at the lower end and add a diagonal joint or short cross-connection.

[0012] Furthermore, the magnitudes of the combined vectors of corresponding phase bands A and X, B and Y, and C and Z are equal. The combined vectors of phase band A and phase band X are U, the combined vectors of phase band B and phase band Y are V, and the combined vectors of phase band C and phase band Z are W. The vectors of the three phases U, V, and W differ from each other by 120°.

[0013] Furthermore, the U phase is composed of four branches U1 to U4 connected in parallel, the V phase is composed of four branches V1 to V4 connected in parallel, and the W phase is composed of four branches W1 to W4 connected in parallel. Each branch consists of 27 coils connected in series via slanted parallel connectors, parallel connectors, and connecting lines.

[0014] Furthermore, before wiring, the 324 upper layer bars and 324 lower layer bars of the stator winding are numbered respectively, and the upper and lower layer bars are arranged alternately in the wiring block diagram or star diagram.

[0015] In summary, the present invention has the following advantages: 1. This invention achieves symmetrical four-branch wiring through a 324-slot 18-pole motor, making the stator slot current comparable to that of most existing pumped storage units. Compared with the conventional three-branch scheme, it effectively reduces the stator heat load and ventilation and heat dissipation pressure, providing a feasible electrical solution for high-altitude 320MW pumped storage units.

[0016] 2. This invention uses short-pitch coils (short-pitch coefficient 0.833) and effectively reduces low-order harmonics through potential cross-compensation between coils with different electrical angles. The line voltage waveform distortion rate is significantly improved compared with the full-pitch scheme, making it particularly suitable for pumped storage power generation motors with high power quality requirements.

[0017] 3. This invention employs a lap-wound concentrated winding structure, with each of the four branches in each phase concentrated in a specific area of ​​the stator circumference, and no overlap between branches. When rotor eccentricity occurs, the induced electromotive force (EMF) of the branches closer to the rotor increases relatively, while the induced EMF of the branches farther away decreases relatively, naturally forming a small circulating current between the branches. The demagnetizing armature reaction generated by this circulating current can actively counteract part of the unbalanced magnetic pull. Its macroscopic mechanical effect manifests as a reduction in the equivalent electromagnetic stiffness of the motor, thereby suppressing further rotor eccentricity, reducing the runout values ​​of various parts of the generator, and significantly improving the dynamic stability of the shaft system under high altitude and variable load conditions.

[0018] 4. This invention, through vector equalization and special cross-connection, improves the waveform using short-pitch coils while ensuring strict symmetry of the potential of the four branches in each phase. During load operation, the deviation between the current in each branch and the average current in the phase branches is effectively controlled, avoiding additional copper losses and localized overheating caused by circulating current, thus ensuring long-term reliable operation of the generator.

[0019] 5. The present invention adopts a 60° standard phase band combined with a short-pitch coefficient of 0.833, resulting in a high winding utilization coefficient; at the same time, the slot-pole combination of 324 slots / 18 poles makes the number of slots per pole per phase 6, which is an integer slot winding, making it easy to manufacture and insert. Attached Figure Description

[0020] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments, wherein: Figure 1 This is a schematic diagram of the phase band and branch division of the four-branch symmetrical double-layer winding of the present invention; Figure 2 This is a block diagram of the U-phase four-branch symmetrical double-layer concentrated winding connection of the present invention; Figure 3 This is a block diagram of the V-phase four-branch symmetrical double-layer concentrated winding connection of the present invention; Figure 4 This is a block diagram of the W-phase four-branch symmetrical double-layer concentrated winding connection of the present invention; Figure 5 This is a comparative schematic diagram of traditional short-pitch wiring and the special short-pitch wiring of this invention; wherein, Figure 5 (a) is the method of connecting the conductors in the same branch in a single electrical angle sequence in traditional short-distance wiring. Figure 5 (b) shows the wiring method of the special electrical angle cross connection adopted in this invention, where m and n are schematic electrical angle layer numbers; In the diagram, the number in the upper right corner without an apostrophe represents the upper layer bar slot number, while the number in the upper right corner with an apostrophe represents the lower layer bar slot number. Detailed Implementation

[0021] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments and accompanying drawings, further clarifies the invention. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.

[0022] The following describes in detail, with reference to the accompanying drawings, a wiring method for a 324-slot, 18-pole symmetrical four-branch double-layer three-phase winding according to the present invention. In this embodiment, the stator has 324 slots, 18 poles, and 3 phases, with q=6 slots per pole and per phase, a winding pitch y=15 slots, and a short-pitch coefficient of 0.833 (pole pitch τ=324 / 18=18 slots, y / τ=15 / 18=0.833). For ease of description, the bar numbering rule is as follows: 1 to 324 represent upper-layer bars, 1' to 324' represent lower-layer bars, and upper and lower-layer bars with the same number are located in the same slot. The term "coil" in the following branch wiring refers to a short-pitch coil formed by connecting upper and lower-layer bars according to a winding pitch of 15 slots; the connection methods include conventional parallel connection, oblique parallel connection, and short-span connection. Among them, the oblique parallel connection is mainly used for connecting the upper and lower layers of bar at the same position at the bottom when connecting adjacent slots across mechanical angles; the short crossover connection refers to using an independent short wire to crossover the ends of two bar that need to be connected between the ends of bar that span multiple slots.

[0023] This invention does not synthesize the potential vectors of the upper and lower sides of the same coil, but considers them separately, directly plotting both upper and lower potential vectors in the star diagram. Since the upper and lower bars of the same slot are at the same position on the circumference, their induced potential vectors have the same direction and magnitude. Therefore, the number of potential vectors on each circumference of the star diagram from the inside out is completely consistent with the existing star diagram, but the number of circumference layers is doubled, meaning the number of overlapping potential vectors on the star diagram from the inside out is doubled. For the stator winding of a 324-slot, 18-pole motor, its star diagram has 18 overlapping potential vectors from the inside out; each phase has 36 overlapping potential vectors (18 for the positive phase and 18 for the negative phase), which are connected in symmetrical 4 branches, each branch occupying 9 overlapping potential vectors.

[0024] like Figure 1 As shown, the star diagram containing the potential vectors of the upper and lower layers of bars has 18 overlapping potential vectors from the inside out, divided into 6 equal parts. Each part is a phase band, represented by A, Z, B, X, C, and Y. Each phase band has 18 overlapping potential vectors from the inside out. In the diagram, numbers without apostrophes represent the slot numbers of the upper layer bars, and numbers with apostrophes represent the slot numbers of the lower layer bars. The A and X phase bands are 180° apart to form the U phase, the B and Y phase bands are 180° apart to form the V phase, and the C and Z phase bands are 180° apart to form the W phase. The A, B, and C phases are 120° apart, satisfying three-phase symmetry. Each pair of phase bands is divided into four equal parts, each containing 9 overlapping potential vectors, for a total of 54 potential vectors, forming a branch. Each of A, Z, B, X, C, and Y contains 2 branches, and the potential vectors in the 4 branches of each phase have the same composite vector, satisfying branch symmetry.

[0025] The key wiring feature of this invention lies in its special electrical angle cross connection. For example... Figure 5 As shown in (b), for each branch, after 8 of the 9 overlapping potential vectors are naturally connected from the upper layer bar to the lower layer bar according to the winding pitch (15 slots), the remaining 1 layer adopts the following special connection method with electric angle crossing: (1) The upper layer bar of the first electrical angle of each phase is connected to the lower layer bar of the second electrical angle, and the upper layer bar of the second electrical angle is connected to the lower layer bar of the first electrical angle, so as to realize the cross-interchange between the first two electrical angles; (2) After the upper bar of the third electrical angle and the upper bar of the sixth electrical angle are naturally connected to the lower bar according to the winding pitch, the lower bar of the third electrical angle is connected to the upper bar of the sixth electrical angle to form a cross connection between the third and sixth electrical angles. (3) After the upper layer bar of the fourth electrical angle and the upper layer bar of the fifth electrical angle are naturally connected to the lower layer bar according to the winding pitch, the lower layer bar of the fourth electrical angle is connected to the upper layer bar of the fifth electrical angle to form a cross connection between the fourth and fifth electrical angles. (4) After the upper bar of the first electrical angle is connected to the lower bar of the second electrical angle, it is then connected to the upper bar of the third electrical angle to form a branch; after the upper bar of the second electrical angle is connected to the lower bar of the first electrical angle, it is then connected to the upper bar of the fourth electrical angle to form another branch. The remaining branches are formed in the same way, for a total of 4 branches.

[0026] For ease of understanding, Figure 5 (a) shows a traditional short-distance wiring method (the conductors in the same branch are connected in a single electrical angle sequence). Figure 5 The core difference between the wiring method of the present invention shown in (b) and this method lies in the fact that, through potential cross-compensation between bars with different electrical angles, low-order harmonics are effectively reduced and the potential waveform is improved while ensuring that the combined potential of each branch is equal. Simultaneously, due to the use of lap-wound concentrated windings, each branch is arranged in a concentrated manner along the stator circumference (e.g., Figures 2 to 4 As shown in the figure, there is no overlapping area between the branches. When the rotor becomes eccentric, the induced electromotive force of each branch will naturally produce a slight difference, forming a controllable circulating current.

[0027] Calculations show that the maximum deviation between the load branch current and the average current of the phase branch in the traditional short-pitch scheme (y1=15) is 53.79A, approximately 2.01% of the rated branch current. In contrast, the maximum deviation between the load branch current and the average current of the phase branch in the special short-pitch scheme (y1=15) of this invention is only 18.07A, approximately 0.68% of the rated branch current. This demonstrates that while using short-pitch coils to improve the waveform, this invention controls the branch imbalance to a level far superior to that of traditional short-pitch connections. During normal operation, the circulating current between stator branches accounts for less than 1%, avoiding additional copper losses and localized overheating caused by circulating currents, thus ensuring long-term reliable generator operation.

[0028] When forming the windings, the upper layer bars are naturally connected to the lower layer bars according to the winding pitch. When connecting across mechanical angles, the upper and lower layer bars at the same position at the lower end are opened to increase the oblique parallel connection. The bars of phases A and X, B and Y, and C and Z are connected by "head-to-head" and "tail-to-tail" connections respectively to ensure that the potentials of the bars are added together.

[0029] like Figure 2 As shown, it is according to Figure 1 The U-phase wiring block diagram obtained by the phase band and branch division method shown.

[0030] The 24 short-pitch coils belonging to phase U are: 39'-24, 38'-23, 37'-22, 36'-21, 35'-20, 34'-19, 1-16', 2-17', 3-18', 4-19', 5-20', 6-21', 75'-60, 74'-59, 73'-58, 72'-57, 71'-56, 70'-55, 37-52', 38-53', 39-54', 40-55', 41-56', and 42-57', along with coils 3'-313 connected by parallel connectors, angled parallel connectors, and connecting wires. 324'-309 and 323'-307 are connected in series to form branch U1 by adding their potentials; 73-88', 74-89', 75-90', 76-91', 77-92', 78-93', 111'-96, 110'-95, 109'-94, 108'-93, 107'-92, 106'-91, 109-124', 110-125', 111-126', 112-127', 113-128', 114-129', 147'-132, and 146, which belong to phase U, are connected in series to form branch U1. '-131, 145'-130, 144'-129, 143'-128, 142'-127, a total of 24 short-pitch coils, and 146-160', 148-163', 149-164' connected by parallel joints, oblique parallel joints, and connecting wires, are connected in series to form branch U2 by adding potentials; 217-232', 218-233', 219-234', 220-235', 221-236', 222-237', 219'-204, 218'-203, 217'-202, 216, belonging to phase U, are connected in series by adding potentials. '-201, 215'-200, 214'-199, 181-196', 182-197', 183-198', 184-199', 185-200', 186-201', 183'-168, 182'-167, 181'-166, 180'-165, 179'-164, 178'-163, a total of 24 short-pitch coils, and 145-161', 147-162', 150-165' connected by parallel connectors, oblique parallel connectors and connecting wires, are connected in series to form branch U3 by adding potentials;The following ranges belong to phase U: 255'-240, 254'-239, 253'-238, 252'-237, 251'-236, 250'-235, 253-268', 254-269', 255-270', 256-271', 257-272', 258-273', 291'-276, 290'-275, 289'-274. Twenty-four short-pitch coils (288'-273, 287'-272, 286'-271, 289-304', 290-305', 291-306', 292-307', 293-308', and 294-309'), connected in series with parallel connectors, oblique connectors, and connecting wires (2'-312, 1'-310, 322'-308) by adding their potentials, form branch U4.

[0031] The U-phase winding is formed by four branches, U1, U2, U3, and U4, connected in parallel.

[0032] like Figure 3 As shown, it is according to Figure 1 The block diagram of V-phase wiring obtained by the phase band and branch division method shown.

[0033] The following ranges belong to phase V: 51'-36, 50'-35, 49'-34, 48'-33, 47'-32, 46'-31, 13-28', 14-29', 15-30', 16-31', 17-32', 18-33', 87'-72, 86'-71, 85'-70, 84'-69, 83'-68, 82'-67, 49-64', 50-65', 51-66', 52-67', 53-68'. The 24 short-pitch coils (54-69') and the coils (15'-324, 12'-321, 11'-319) connected by parallel, oblique parallel, and connecting wires are connected in series to form the V1 branch by adding their potentials; the coils belonging to phase V (85-100', 86-101', 87-102', 88-103', 89-104', 90-105', 123'-108', 122'-107', 121'-106', 120'-105', 119'-104', 118'-103', 121-136', 122-137', 123-138', 124-139', 125-140', 126-141', 159'-144', 158'-143', 1... 24 short-pitch coils, 57'-142, 156'-141, 155'-140, and 154'-139, and coils 158-172', 160-175', and 161-176' connected by parallel connectors, oblique connectors, and connecting wires, are connected in series to form the V2 branch by adding potentials; coils 229-244', 230-245', 231-246', and 232-247' are connected in series. 24 short-pitch coils (233-248', 234-249', 231'-216, 230'-215, 229'-214, 228'-213, 227'-212, 226'-211, 193-208', 194-209', 195-210', 196-211', 197-212', 198-213', 195'-180, 194'-179, 193'-178, 192'-177, 191'-176, 190'-175) and 157-173', 159-174', 162-177' belonging to phase V, connected by parallel, oblique parallel and connecting wires, are connected in series to form branch V3 by adding potentials;The following ranges belong to phase V: 267'-252, 266'-251, 265'-250, 264'-249, 263'-248, 262'-247, 265-280', 266-281', 267-282', 268-283', 269-284', 270-285', 303'-288, 302'-287, 301'-286, 300'-285, 299'-284, 298'-283, 301-316', 302-317', 303-318', 304-319', 305-320'. The 24 short-pitch coils (306-321') and coils (14'-323, 13'-322, 10'-320) connected by parallel connectors, oblique connectors, and connecting wires are connected in series to form a V4 branch by adding their potentials.

[0034] The V-phase winding is formed by four branches, V1, V2, V3, and V4, connected in parallel.

[0035] like Figure 4 As shown, it is according to Figure 1 The diagram shows the W-phase wiring block diagram obtained by dividing the phase bands and branches as shown.

[0036] Set the following positions: 27'-12, 26'-11, 25'-10, 24'-9, 23'-8, 22'-7, 25-40', 26-41', 27-42', 28-43', 29-44', 30-45', 63'-48, 62'-47, 61'-46, 60'-45, 59'-44, 58'-43, 61-76', 62-77', 63-78', 64-79', 65-80'. The 24 short-pitch coils (66-81') and the coils belonging to phase W (315'-300, 312'-297, 311'-295) connected in parallel, oblique parallel, and connecting wires are connected in series to form branch W1 by adding their potentials; the coils belonging to phase W (97-112', 98-113', 99-114', 100-115', 101-116') are connected in series. 102-117', 99'-84', 98'-83', 97'-82', 96'-81', 95'-80', 94'-79', 133-148', 134-149', 135-150', 136-151', 137-152', 138-153', 135'-120', 134'-119', 133'-118', 132'-117', 131'-116', 130'-115' (a total of 24 short-pitch coils), and 170-184' and 172-187'' connected by parallel connectors, angled parallel connectors, and connecting wires. 173-188' are connected in series to form branch W2 by adding their potentials; 241-256', 242-257', 243-258', 244-259', and 245-260', which belong to phase W, are connected in series. 24 short-pitch coils, 246-261', 207'-192, 206'-191, 205'-190, 204'-189, 203'-188, 202'-187, 205-220', 206-221', 207-222', 208-223', 209-224', 210-225', 171'-156, 170'-155, 169'-154, 168'-153, 167'-152, and 166'-151, and 169-185', 171-186', and 174-189' connected by parallel, oblique parallel, and connecting wires, are connected in series to form branch W3 by adding potentials;The following lines belong to phase W: 243'-228, 242'-227, 241'-226, 240'-225, 239'-224, 238'-223, 277-292', 278-293', 279-294', 280-295', 281-296', 282-297', 279'-264, 278'-263, 277'-262, 276'-261, 275'-260, 274'-259, 313-4', 314-5', 315-6', 316-7', 317-8'. The 24 short-pitch coils (318-9') and coils (314'-299, 313'-298, and 310'-296) connected by parallel connectors, oblique connectors, and connecting wires are connected in series to form branch W4 by adding their potentials.

[0037] The four branches W1, W2, W3, and W4 are connected in parallel to form the W-phase winding.

[0038] The U-phase, V-phase, and W-phase windings together constitute a 60° phase zone four-branch symmetrical double-layer lap winding.

[0039] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A wiring method for a 324-slot, 18-pole symmetrical four-branch double-layer three-phase winding, characterized in that, Includes the following steps: S1. The potential vectors of the 648 stator winding bars are considered as individual vectors; S2. Divide all potential vectors into six phase zones: A, Z, B, X, C, and Y, according to the 60° standard phase zone. S3. Divide the potential vectors contained in the corresponding phase bands A and X, B and Y, C and Z of the same phase into 4 equal parts. Each part is added in series to form a branch of potential vector combination, so that each phase gets 4 branches and each branch is equally distributed with 9 layers of overlapping potential vectors. S4. Using short-pitch coils, 8 of the 9 layers of overlapping potential vectors in each branch are naturally connected to the upper and lower layers of wire bars according to the winding pitch, and the remaining 1 layer is connected by special electrical angle crossing. S5. Connect the bars in the corresponding phases A and X, B and Y, C and Z in the same direction by connecting the head to the tail and the tail to the head, to ensure that the potentials of the bars are added together; S6. Connect the four branches of each phase in parallel to form a U, V, W three-phase symmetrical four-branch double-layer three-phase winding.

2. The wiring method for a 324-slot, 18-pole symmetrical four-branch double-layer three-phase winding according to claim 1, characterized in that, The special connection of the electrical angle crossing includes: each phase with a first electrical angle upper layer bar connected to a second electrical angle lower layer bar, and the second electrical angle upper layer bar connected to the first electrical angle lower layer bar; the third, fourth, fifth, and sixth electrical angle upper layer bars are naturally connected to their respective lower layer bars of the same electrical angle; the first electrical angle is connected, the second electrical angle lower layer bar is connected to the third electrical angle upper layer bar, and then the third electrical angle lower layer bar is connected to the sixth electrical angle upper layer bar, and a branch is formed together with the 8 layers of overlapping potentials naturally connected in this branch; the second electrical angle upper layer bar is connected, the first electrical angle lower layer bar is connected to the fourth electrical angle upper layer bar, and then the fourth electrical angle lower layer bar is connected to the fifth electrical angle upper layer bar, and a branch is formed together with the 8 layers of overlapping potentials naturally connected in this branch.

3. The wiring method for a 324-slot, 18-pole symmetrical four-branch double-layer three-phase winding according to claim 1, characterized in that, The short-pitch coefficient of the short-pitch coil is 0.833, and the winding pitch is 15 slots.

4. The wiring method for a 324-slot, 18-pole symmetrical four-branch double-layer three-phase winding according to claim 1, characterized in that, When wiring, in the case of connecting across mechanical angles, open the upper and lower layers of wires at the same position at the lower end and add a diagonal joint or short crossover connection.

5. The wiring method for a 324-slot, 18-pole symmetrical four-branch double-layer three-phase winding according to claim 1, characterized in that, The magnitudes of the combined vectors of corresponding phase bands A and X, B and Y, and C and Z are equal. The combined vectors of phase band A and X are U, the combined vectors of phase band B and Y are V, and the combined vectors of phase band C and Z are W. The vectors of the three phases U, V, and W differ by 120°.

6. The wiring method for a 324-slot, 18-pole symmetrical four-branch double-layer three-phase winding according to claim 1, characterized in that, The U phase consists of four branches U1 to U4 connected in parallel, the V phase consists of four branches V1 to V4 connected in parallel, and the W phase consists of four branches W1 to W4 connected in parallel. Each branch consists of 27 coils connected in series via slanted parallel connectors, parallel connectors, and connecting lines.

7. The wiring method for a 324-slot, 18-pole symmetrical four-branch double-layer three-phase winding according to claim 1, characterized in that, Before wiring, number the 324 upper layer bars and 324 lower layer bars of the stator winding, and arrange the upper and lower layer bars alternately in the wiring block diagram or star diagram.

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