Symmetrical four-branch connection method for short-pitch wave winding with integer-slot and odd-numbered pole pairs

Abstract

This invention discloses a symmetrical four-branch connection method for short-pitch wave windings with an odd number of pole pairs. S1: Divide all slots into basic phase band slots and short-pitch phase band slots; S2: Divide both basic phase band slots and short-pitch phase band slots into three phases: A, B, and C; S3: Alternately construct two slot number branches using p slot number units for each of the 2p slots under each phase; S4: Alternately connect the upper and lower conductors in each slot number branch with a pitch of 3q to form two winding loops. The slot number branches form four winding circuits; S5, open one point of each of the four winding circuits as a terminal and connect them in parallel to form a parallel four-branch winding; the front and rear structural pitches of the windings are equal and have a short-pitch ratio that can weaken high-order harmonics. Each branch is composed of a basic phase band and a short-pitch phase band with electrical short-pitch effect. The four branches of the windings in parallel are completely symmetrical, balanced and without circulating current; breaking through the limitation of traditional motor winding theory that there is no short-pitch symmetrical four-branch when the number of pole pairs is odd.

Description

Technical Field

[0001] This invention relates to the field of three-phase AC motor windings, and more particularly to a symmetrical four-branch connection method for short-pitch wave windings with an odd number of pole pairs in integer slots. Background Technology

[0002] Generally speaking, for a three-phase motor, i.e., a double-layer wave winding with 3 phases, p pole pairs, and Z stator slots, when the number of slots per pole per phase is q = Z / (m × 2p) = an integer, according to the traditional winding design method, a coil is always composed of an upper side and a lower side. Taking the coil as the design unit and dividing the phase zone with 6 × 60° electrical angles, when using short pitch, i.e., the slot pitch y1 between the upper and lower sides of the coil is ≠ 3q, the number of possible parallel branches a of the winding must be a factor of the number of poles 2p to achieve branch symmetry and balance. Therefore, if p is an odd number, then 2p does not contain the factor 4, so there is no symmetrical balanced branch with a = 4. For large-capacity hydro-generator sets, many applications involve large odd numbers of pole pairs, such as p = 7, 11, 13, and 17. Therefore, when designing short-pitch windings, choosing only branches with a = 1, 2, p, and 2p can result in either excessively large or insufficient branch currents. To make the motor design more economical and reasonable, a scheme with a = 4 is often preferred in practical designs. On the other hand, theoretically, for integer-slot motors, if designed using coils as units, only full-pitch windings with y1 = 3q can achieve a parallel four-branch winding with a = 4 when the number of pole pairs p is odd. However, due to the full-pitch nature of the windings, higher harmonics cannot be weakened; for example, the winding coefficients for the 5th and 7th harmonics reach 15%–20% of the fundamental frequency. Alternatively, an asymmetrical balanced four-branch design can achieve short pitch to reduce higher harmonics, but the parallel four-branch design suffers from the disadvantage of circulating fundamental and harmonic currents. Summary of the Invention

[0003] To address the problem in existing technologies where the 5th and 7th harmonics cannot be weakened or there is circulating current in the fundamental and harmonics in parallel four-branch windings, this invention provides a symmetrical four-branch wiring method for short-pitch wave windings with an odd number of pole pairs. Each branch is composed of a basic phase band and a short-pitch phase band with electrical short-pitch effect, and the four branches of the windings connected in parallel are completely symmetrical, balanced, and free of circulating current.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] The symmetrical four-branch connection method for short-pitch wave windings with an odd number of pole pairs includes the following steps:

[0006] S1. Divide all slots into basic phase zone slots and short-pitch phase zone slots;

[0007] S2. Divide the basic phase belt slots and short-pitch phase belt slots into three phases: A, B, and C.

[0008] S3. For each phase, the slots are used as units within a range of p pole pitches to alternately construct two slot number branches.

[0009] S4. Connect the upper and lower conductors in each slot of each branch with an alternating series connection of 3q to form two winding loops. The two slot branches together form four winding loops.

[0010] S5. Open one point in each of the four winding circuits as a terminal and connect them in parallel to form a parallel four-branch winding. The front and rear structural pitches of the windings are equal. It can realize the basic phase band and short-pitch phase band with electrical short-pitch effect in each branch. The four branches of the windings connected in parallel are completely symmetrical, balanced and without circulating current.

[0011] Furthermore, S1 includes an odd number of pole pairs p, an integer number of slots per pole per phase, and 3q slots within a 180° electrical angle range are divided into basic phase band slots and short-pitch phase band slots according to a certain pattern. The first slot of the short-pitch phase band is offset from the first slot of the basic phase band by s slots. This results in an electrical short-pitch effect.

[0012] Furthermore, the motor has Z slots and m = 3 phases, using a 60° electrical angle phase-to-phase configuration. With three phases at a 180° electrical angle, there are a total of 3q slots, with q slots per phase. Each slot has 2p sub-slots, and each sub-slot has two conductors. Therefore, each phase has q × 2p × 2 = 4pq conductors. Since 4pq is an integer and a multiple of 4, theoretically, it is possible to achieve a parallel four-branch winding connection with pq conductors per branch.

[0013] Furthermore, the q slots available for each phase are first divided into two groups of slots with mutual electrical short-pitch effects. The q slots for each phase are further divided into j basic phase band slots and k short-pitch phase band slots. If the calculated slot number exceeds 3q, 3q is subtracted, and the electrical short-pitch is taken as an odd number. Specifically, q is defined as q = j + k, where j and k are integers, and j ≥ k, jk ≤ 1. The q slots for each phase are divided into j basic phase band slots and k short-pitch phase band slots, denoted as J... X and K X The "X" can be replaced by "A", "B", or "C" to represent the phase slot of any one of the three phases A, B, and C. The J of each phase... X Slot number by Calculate, where P X They are: Phase A and Phase P A =0, B phase P B =2q, C phase P C =q. K of each phase X Slot number by and The calculation is performed, where s is the electrical short-range component, and s takes the form of an odd number.

[0014] Furthermore, S3 includes dividing the slots under each slot number of each phase into two equal parts, taking the slots within a range of p consecutive pole pitches as units, and forming slot number branches with the same markings, thus forming two slot number branches in total.

[0015] Furthermore, S4 includes two conductors in each slot: an upper conductor and a lower conductor. The slots in each slot-numbered branch are connected sequentially from the first slot number to the last slot in an alternating pattern of "upper conductor—lower conductor—upper conductor—lower conductor…", then bridging back to the first slot number (closed) to form a winding loop. A second winding loop is then formed starting from the first slot number in an alternating pattern of "lower conductor—upper conductor—lower conductor—upper conductor…". Two slot-numbered branches form a total of four winding loops using the same pattern. Slots under the same slot number are connected with a pitch of 3q, while slots under different slot numbers are connected with bridging wires or skewed connections.

[0016] Furthermore, S5 includes opening the four winding loops at any suitable connection point and connecting the terminals of the same polarity in parallel to form four branch windings. This ensures that the four branch windings are completely identical in fundamental potential and magnetomotive force, preventing the formation of circulating currents, achieving symmetrical balance, and effectively reducing higher harmonics due to the electrical short-pitch component in the phase band formed by the windings.

[0017] The present invention has the following advantages:

[0018] (1) The front and rear structural pitches of the winding are equal. Each branch is composed of a basic phase band and a short-pitch phase band with electrical short-pitch effect. Therefore, it has a short-pitch ratio that can weaken high-order harmonics. The four branches of the winding in parallel are completely symmetrical and balanced without circulating current. (2) It breaks through the limitation of the traditional motor winding theory that there are no short-pitch symmetrical four branches when the number of pole pairs is odd. It expands the motor optimization design path. In particular, it solves the mismatch problem of the salient pole synchronous motor for pumped storage under large capacity, high voltage and speed (number of poles), so that the performance index and economic index of the motor can be optimized. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in this invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without any creative effort.

[0020] Figure 1 This refers to the distribution of slot numbers and the assignment of slot numbers for basic phase bands and short-distance phase bands in the first embodiment when the number of slots per pole per phase is q=6.

[0021] Figure 2This is the slot layout diagram, phase band division of phase A, and configuration of the A-phase slot number branch when 2p poles, Z slots, and q=6 are shown in the first embodiment.

[0022] Figure 3 This is the phase band slot diagram in the second embodiment.

[0023] Figure 4 This is a schematic diagram of the method steps of the present invention. Detailed Implementation

[0024] The following specific embodiments illustrate the implementation of the present invention. Obviously, the described embodiments are only a part of, and not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0025] In a preferred embodiment, the present invention discloses a symmetrical four-branch connection method for short-pitch wave windings with an odd number of pole pairs, where the number of pole pairs p is odd, the number of slots Z, and the number of phases m = 3. The number of slots per pole per phase q = Z / (2pm) is an integer. Since the electrical angle α between adjacent slots is 360° × p / Z = 360° × p / (2pmq) = 60° / q, and each phase occupies qα = q × 60° / q = 60°, when each phase has a 60° electrical angle phase, the three phases have a total of 3q slots at a 180° electrical angle. Therefore, each phase occupies q slots, each slot has 2p slots, and each slot has two conductors (double-layer winding), so each phase has q × 2p × 2 = 4pq conductors. Since 4pq is an integer and a multiple of 4, a parallel four-branch winding connection with pq conductors per branch is achieved.

[0026] like Figure 4 As shown, it includes the following steps:

[0027] S1. Divide all slots into basic phase zone slots and short-pitch phase zone slots;

[0028] First, the q slots available for each phase are divided into two groups of slots with mutual electrical short-pitch effects. Specifically, q is defined as q = j + k, where j and k are integers, and j ≥ k, jk ≤ 1. The q slots for each phase are then divided into j basic phase band slots and k short-pitch phase band slots, denoted as J0, J1, J2, J3, J4, J5, J6, J7, J8, J9, J10, J11, J21, J9, J11, J2 ... X and K X The "X" can be replaced by "A", "B" or "C" to represent the phase slot of any one of the three phases A, B, and C.

[0029] S2. Divide the basic phase belt slots and short-pitch phase belt slots into three phases: A, B, and C.

[0030] J of each phase X Slot number by Calculate, where P X They are: Phase A and Phase P A =0, B phase P B =2q, C phase P C =q. K of each phase X Slot number by and The calculation involves taking 's' as the electrical short-pitch component, where 's' is an odd number. When the calculated slot number exceeds 3q, the calculated value must be subtracted by 3q. For ease of understanding, let's take q = 6 as an example. Within a 180° electrical angle range, there are 3q = 3 × 6 = 18 slots. Slots 1# to 18# are... Figure 1 The allocation of slot numbers for each phase is calculated as follows: The j and k values ​​that satisfy j+k=6, and j≥k, jk≤1 are j=k=3; P A =0, P B =2q=12, P C =q=6. The basic phase band slot number J of phase A. Ai =P A +2i-1, (i = 1, 2, ..., j). P A Substituting =0 and j=3, J Ai =2i-1, (i=1,2,3), that is, i=1, J A1 =2×1-1=1; i=2, J A2 =2×2-1=3; i=3, J A3 =2×3-1=5, J of phase A A The phase band slot number is denoted as J. A1,2,3 =1,3,5; using the same calculation method, the basic phase zone slot number J of phase B is... Bi =P B +2i-1, (i=1,2,…,j), substitute into P B =12, j=3, J Bi =12+2i-1, (i=1,2,3), calculate J B1,2,3 =13,15,17; Similarly, the basic phase band slot number J of phase C can be obtained. Ci =6 + 2i - 1, (i = 1, 2, 3), that is, J C1,2,3 =7,9,11. Taking the electrical short distance s = 3, i.e., the short distance ratio = 1 - s / (3q) = 1 - 3 / 18 = 0.833, the short distance phase band slot number is calculated using phase B as an example. The short distance phase band slot number for phase B is K. Bi =J Bi +s, (i=1,2) and K Bi =J Bi +s+jk, (i=3), that is, K B1 =J B1 +s=13+3=16,K B2=J B2 +s=15+3=18,K B3 =J B3 +s+jk=17+3+3-3=20, because 20>3q=18, therefore K B3 =20-3q=20-18=2. That is, the short-pitch phase band slot number for phase B is K. B1,2,3 =16,18,2, and the same method can be used to obtain K for phase A. A1,2,3 =4,6,8, K of phase C C1,2,3 =10,12,14.

[0031] S3. For each phase, the slots are used as units within a range of p pole pitches to alternately construct two slot number branches.

[0032] Taking the number of slots per pole per phase as q=6 as an example, the following is constructed: Figure 2 The slot layout shown is a 3q×2p = 18×2p grid, with slot numbers from 1 to Z arranged in order. Figure 1 As shown, fill in the slots as follows: In the first row (pole 1), fill in 18 slot numbers (=3q) in the order of 1, 2, 3, ... 18. In the second row (pole 2), start from the last slot number of the previous row and continue filling in the slots sequentially. Continue filling in both rows until all slots are filled. Figure 2 As shown, Figure 2 The slot numbers begin in the third line and are abbreviated. The slot number corresponding to phase A is J. A Slot number (1#, 3#, 5#) and K A The slots under slot numbers (4#, 6#, 8#) are all classified as phase A. That is, phase A includes the slots under slot numbers 1#, 3#, 4#, 5#, 6#, and 8#. Figure 2 The areas are indicated by a thick border. Phase B includes slots numbered 13#, 15#, 16#, 17#, 18#, and 2#, while Phase C includes slots numbered 7#, 9#, 10#, 11#, 12#, and 14#. Figure 2 In the slot layout diagram, the abbreviated "○", "△", and "□" represent slot numbers for phases A, C, and B, respectively. Taking phase A as an example, the slots under each slot number of phase A are divided into two equal parts, with each part consisting of a range of p consecutive pole pitches. Again, using q=6 as an example, ... Figure 2 The filled and unfilled cells enclosed by the medium-thick border are grouped into two slot number branches based on their color. Figure 2 The solid and dashed lines in the diagram are shown.

[0033] S4. Connect the upper and lower conductors in each slot of each branch with an alternating series connection of 3q to form two winding loops. The two slot branches together form four winding loops.

[0034] Two winding loops are formed based on each slot number branch, resulting in a total of four winding loops per phase. Specifically, each slot has two conductors: an upper conductor and a lower conductor. The slots in each slot number branch, starting from the first slot number, are connected to the last slot in an alternating pattern of "upper conductor—lower conductor—upper conductor—lower conductor…" before bridging back to the first slot number (closing) to form one winding loop. Then, starting from the first slot number, a second winding loop is formed in an alternating pattern of "lower conductor—upper conductor—lower conductor—upper conductor…". The two slot number branches form a total of four winding loops using the same pattern. Slots under the same slot number are connected with a pitch of 3q, while slots under different slot numbers are connected with bridging wires or skewed connections.

[0035] S5. Open one point in each of the four winding circuits as a terminal and connect them in parallel to form a parallel four-branch winding. The front and rear structural pitches of the windings are equal. The four winding circuits formed are opened at any suitable connection point, and the terminals of the same polarity are connected in parallel to form a four-branch winding. The four-branch windings formed are completely identical in fundamental potential and magnetomotive force, and will not form circulating current (symmetrical balance). Moreover, because the phase band formed by the windings contains electrical short-pitch components, it can effectively weaken higher harmonics.

[0036] For the possible number of slots q per pole and per phase to achieve a parallel branch number a=4 when the pole pair number p is odd, the distribution of the basic phase band and short-pitch phase band of any phase is shown in the table below when the electrical short-pitch component is s=3. In the table, "○" represents the basic phase band composed of 2p slots, and "●" represents the short-pitch phase band composed of 2p slots. The range is 4≤q≤8. When the electrical short-pitch component s=1, the parallel four-branch winding is completely equivalent to the conventionally designed full-pitch winding in terms of electrical performance.

[0037] The phase distribution pattern is independent of the number of poles 2p, and only depends on the number of slots q per pole per phase and the electrical short-pitch component s. When q is odd, the winding leads need to be arranged at both ends of the motor; when q is even, the leads are arranged at only one end.

[0038] Table 1. Phase band table

[0039]

[0040] In the second embodiment, taking a 300MW-class generator motor with a voltage level of 15.75-18kV and a pole number of 2p=14, which is common in the field of pumped storage, as an example, the specific implementation method with a branch number of a=4 is as follows.

[0041] The motor has 3 phases (m = 3), 2p poles (2p = 14), and 7 pole pairs (p = 7). The number of slots is Z = 252. Therefore, the number of slots per pole per phase is q = Z / (m × 2p) = 252 / (3 × 14) = 6, and 3q = 18. This means there are 3q = 18 slots within a 180° electrical angle range. Phase A occupies 18 / m = 18 / 3 = 6 slots. q = j + k = 6. The j and k values ​​satisfying j ≥ k and jk ≤ 1 are j = 3 and k = 3. The basic phase number of phase A is J. Ai =2i-1, i=1,2,3, that is, J A1,2,3 =1,3,5; Since j=k, jk=0, so the calculation of its short-distance phase zone slot number is reduced to K. Ai =J Ai +s, i=1,2,3, taking the electrical short-range component s=3, then K A1,2,3 =1+3,3+3,5+3, that is, K A1,2,3 = 4, 6, 8. Therefore, the total phase zone slot numbers for phase A are 1#, 3#, 4#, 5#, 6#, 8#. A 3×60° phase zone slot diagram is constructed as follows: Figure 3 As shown in the diagram, the slot numbers under slots 1#, 3#, 4#, 5#, 6#, and 8# are marked with thick outlines as the phase band of phase A, and slot number branches A1 and A2 are constructed as units within 7 (=p) consecutive pole pitches under each slot. The slot numbers under the first slot number branch are: A1 = {1, 19, 37, 55, 73, 91, 109}, {129, 147, 165, 183, 201, 219, 237}, {4, 22, 40, 58, 76, 94, 112}, {131, 149, 167, 185, 203, 221, 239}, {6, 24, 42, 60, 78, 96, 114}, {134, 152, 170, 188, 206, 224, 242}, a total of 42 slot numbers. The slot number within each {} is a slot number unit within p pole pitches.

[0042] The slot numbers under the second slot number branch are: A2 = {127, 145, 163, 181, 199, 217, 235}, {3, 21, 39, 57, 75, 93, 111}, {130, 148, 166, 184, 202, 220, 238}, {5, 23, 41, 59, 77, 95, 113}, {132, 150, 168, 186, 204, 222, 240}, {8, 26, 44, 62, 80, 98, 116}, a total of 42 slot numbers.

[0043] The first winding circuit A11 and the second winding circuit A12 are formed by the first slot branch A1; the third winding circuit A21 and the fourth winding circuit A22 are formed by the second slot branch A2.

[0044] Winding circuit A11, number 1: 上 -19 下 -37 上 -55 下 -73 上 -91 下 -109 上 →129 下 -147 上 -165 下 -183 上 -201 下 -219 上 -237 下 →4 上 -twenty two 下 -40 上 -58 下 -76 上 -94 下 -112 上 →131 下 -149 上 -167 下 -185 上 -203 下 -221 上 -239 下 →6 上 -twenty four 下 -42 上 -60 下 -78 上 -96 下 -114 上 →134 下 -152 上 -170 下 -188 上 -206 下 -224 上 -242 下 →(1 上 (Closed), the superscript "upper" and "lower" of the slot number refer to the upper and lower conductors of that slot. "-" indicates that the upper and lower conductors are connected normally according to the structural pitch of 3q=18 slots, and "→" indicates a jumper or skewed slot connection, the same below.

[0045] Second winding circuit A12: 1 下 -19 上 -37 下 -55 上 -73 下 -91 上 -109 下 →129 上 -147 下 -165 上 -183下 -201 上 -219 下 -237 上 →4 下 -twenty two 上 -40 下 -58 上 -76 下 -94 上 -112 下 →131 上 -149 下 -167 上 -185 下 -203 上 -221 下 -239 上 →6 下 -twenty four 上 -42 下 -60 上 -78 下 -96 上 -114 下 →134 上 -152 下 -170 上 -188 下 -206 上 -224 下 -242 上 →(1 下 closure).

[0046] The slot numbers of the first and second winding circuits are exactly the same, only the superscripts "upper" and "lower" are reversed.

[0047] Third winding circuit A21:127 上 -145 下 -163 上 -…-235 上 →3 下 -twenty one 上 …-111 下 →130 上 -…-238 上 →5 下 -…-113 下 →132 上 -…-240 上 →8 下 -…-116 下 →(127 上 closure)

[0048] 4th winding circuit A22: 127 下 -145 上 -163下 -…-235 下 →3 上 -twenty one 下 …-111 上 →130 下 -…-238 下 →5 上 -…-113 上 →132 下 -…-240 下 →8 上 -…-116 上 →(127 下 closure)

[0049] The final step in completing the parallel four-branch winding is to open any connection point on the terminal side of the above-mentioned winding circuits 1, 2, 3, and 4, and connect the ends with the same polarity in parallel to form the parallel four-branch winding.

[0050] The winding is characterized by: ① Three-phase symmetry, with the fundamental electromotive force and magnetomotive force of each of the four branches being identical in magnitude and phase, and no circulating current in the parallel branches; ② The bars in the same slot belong to the same phase, i.e., same slot same phase; ③ The front and rear structural pitches of the bars are equal, i.e., the first structural pitch of the winding is equal to the second structural pitch; ④ The phase bands constituting the winding branches contain electrical short-pitch components, and the winding has a short-pitch effect, which can weaken higher harmonics. In this embodiment, the winding coefficients of the 5th and 7th harmonics are only 6% and 5% of the fundamental winding coefficient, respectively.

[0051] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A symmetrical four-branch connection method for short-pitch wave windings with an odd number of pole pairs in integer slots, characterized in that, Includes the following steps: S1. Divide all slots into basic phase band slots and short-pitch phase band slots; divide the q slots that each phase can occupy into two groups of slots with mutual electrical short-pitch effects; divide the q slots of each phase into j basic phase band slots and k short-pitch phase band slots, denoted as J1, J2, J3, J4, J5, J6, J7, J8, J9, J10, J11, J21, J12, J13, J14, J15, J16, J17, J< x and K x , where x represents phases A, B, and C; S2. Divide the basic phase belt slots and short-pitch phase belt slots into three phases: A, B, and C; J of each phase... x Slot number is in J xi =P x +2i-1 calculation; K for each phase x Slot number in K xi =J xi +s and K xi =J xi The calculation is performed using +s+jk, where s is the electrical short-pitch component and s takes an odd number. S3. For each phase, two slot number branches are constructed alternately using slot numbers within a range of p pole pitches. p is the number of motor pole pairs, p is an odd number, Z is the number of motor slots, m is the number of phases, m equals 3, q ​​is the number of slots per pole per phase, q equals Z / (2pm), and q is an integer. S4. Connect the upper and lower conductors in each slot of each branch with an alternating series connection of 3q to form two winding loops. The two slot branches together form four winding loops. S5. Open one point in each of the four winding circuits as a terminal and connect them in parallel to form a parallel four-branch winding.

2. The symmetrical four-branch connection method for short-pitch wave windings with an odd number of pole pairs according to claim 1, characterized in that, S1 includes an odd number of pole pairs p and an integer number of slots per pole per phase. The 3q slots within a 180° electrical angle range are divided into basic phase band slots and short-pitch phase band slots according to a certain pattern. The first slot of the short-pitch phase band and the first slot of the basic phase band are offset by s slots.

3. The symmetrical four-branch connection method for short-pitch wave windings with an odd number of pole pairs according to claim 2, characterized in that, The motor has Z slots and m=3 phases. It adopts a 60° electrical angle phase belt for each phase. The three phases have a total of 3q slots at a 180° electrical angle. Each phase occupies q slots, and each slot has 2p slots. Each slot has two conductors.

4. The symmetrical four-branch connection method for short-pitch wave windings with an odd number of pole pairs according to claim 3, characterized in that, First, divide the q slots that each phase can occupy into two groups of slots with mutual electrical short-distance effects. Then, divide the q slots of each phase into j basic phase band slots and k short-distance phase band slots. If the calculated slot number exceeds 3q, subtract 3q and take an odd number for the electrical short distance.

5. The symmetrical four-branch connection method for short-pitch wave windings with an odd number of pole pairs according to claim 4, characterized in that, S3 includes dividing the slots under each slot number of each phase into two parts by taking the slots within a range of p consecutive pole pitches as units, and forming slot number branches with the same markings, thus forming two slot number branches in total.

6. The symmetrical four-branch connection method for short-pitch wave windings with an odd number of pole pairs according to claim 4, characterized in that, S4 includes two conductors in each slot, namely the upper conductor and the lower conductor. The slots in each slot number branch are alternately connected from the first slot number to the last slot and then bridging back to the first slot number to form two winding circuits respectively. Slots under the same slot number are connected with a pitch of 3q, while slots under different slot numbers are connected with bridging wires or skewed slots.

7. The symmetrical four-branch connection method for short-pitch wave windings with an odd number of pole pairs according to claim 6, characterized in that, S5 includes two slot number branches forming four winding loops in the same way. The four winding loops are opened at any suitable connection point and the terminals with the same polarity are connected in parallel to form the four branch windings.

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