Design method of low-alternating-current-loss flat wire winding

Abstract

The invention provides a low-alternating-current-loss flat wire winding design method which comprises the following steps: taking the number of conductor layers and the height of a first-layer conductor as parametric variables, modeling the height of each layer of conductor by using a geometric-progression flat wire conductor, and on the premise of ensuring that the slot fullness rate is unchanged, taking the minimum alternating-current loss of a motor as an optimization target, and calculating the winding height of each layer of conductor; under the constraint of conductor current density limit and process feasibility, value optimization is carried out on the conductor size, and a mixed flat wire winding structure is designed; according to a rule for restraining parallel branch loop current, a weak-symmetry winding arrangement scheme and a strong-symmetry winding arrangement scheme are designed on the basis of a mixed flat wire winding structure, and the positions of a wire inserting end and a welding end of a Hairpin winding in the designed parallel branch winding arrangement connection mode in the circumferential direction of the motor are changed, so that the symmetry of each parallel branch conductor in the circumferential direction of the motor is ensured, and the reliability of the motor is improved. And the wire plugging end is kept unchanged in the radial position of the motor so as to ensure that the sizes of the single-turn hairpin windings are consistent.

Description

Technical Field

[0001] The invention belongs to the field of motor optimization design, and specifically relates to reducing the AC copper loss of a flat wire motor and reducing the circulating current between parallel branches of a flat wire winding, and can be used for the design of a high-efficiency flat wire winding permanent magnet synchronous motor. Background Art

[0002] Permanent magnet synchronous motors (PMSMs) are widely used in electric vehicles, industrial drives, and household appliances due to their high efficiency, high power density, and good control performance. With the increasing requirements for motor performance in various fields, flat wire windings have gradually become an important choice for high-efficiency permanent magnet synchronous motors due to their advantages such as high slot fill rate, good thermal conductivity, and low vibration and noise. However, due to the skin effect and proximity effect, the AC loss of flat wire windings is greater than that of round wire windings, and circulating currents will be generated between the parallel branches, which limits the further improvement of the speed and power density of flat wire winding permanent magnet synchronous motors. Therefore, how to design a high-performance flat wire winding permanent magnet synchronous motor with high speed and low loss is the focus and difficulty of current research in the field of motor design.

[0003] In recent years, domestic and foreign scholars have conducted a lot of research on the design of flat wire winding structure and arrangement connection. Some scholars have proposed methods such as increasing the number of conductor layers and keeping the conductor away from the slot. Although these methods avoid the influence of slot leakage, they sacrifice the slot fill rate, which is not conducive to the improvement of motor power density. In addition, there is a method of cutting the conductor close to the slot to suppress the AC effect of the conductor at the slot, but this method will generate circulation between the strands of wire and increase the difficulty of manufacturing. As for the method of changing the asymmetric conductor cross-sectional area of ​​the conductor height in the slot, although it can effectively reduce the AC loss, due to the limitation of the traditional connection rules between conductors, it only stays in the design of one group of cross-sectional area for every two layers of conductors, which reduces the degree of freedom of design and limits the degree of suppression of AC loss. In response to the problem of circulating current between multiple parallel branches, some studies have proposed conductor arrangement design rules to minimize the circulating current between different parallel branches, but these rules cannot completely avoid circulating current. Summary of the invention

[0004] Purpose of the invention: The present invention proposes a novel low AC loss flat wire winding design method, namely, a hybrid flat wire winding structure. This method is based on the research of asymmetric conductor cross-sectional area method. Under the premise of ensuring that the total cross-sectional area remains unchanged, different heights are designed for each layer of conductors in the motor slot, and the conductor height increases from the slot mouth to the slot bottom. In addition, a novel weakly symmetrical and strongly symmetrical winding arrangement scheme for reducing branch circulating current is designed for this structure, which effectively reduces the AC loss of the motor, suppresses the circulating current between the parallel branches, and improves the efficiency of the flat wire motor. The technical scheme is as follows:

[0005] A method for designing a low AC loss flat wire winding comprises the following steps:

[0006] (3) The number of conductor layers and the height of the first conductor layer are used as parameter variables. The height of each conductor layer is modeled using a geometric series of flat wire conductors. Under the premise of ensuring that the slot fill rate remains unchanged, the motor AC loss is minimized as the optimization goal. Under the constraints of the conductor current density limit and process feasibility, the conductor size is optimized to design a hybrid flat wire winding structure.

[0007] (4) According to the rules for suppressing the circulating current of the parallel branches, weakly symmetrical and strongly symmetrical winding arrangement schemes are designed on the basis of the hybrid flat wire winding structure. The plug-in end and the welding end of the Hairpin winding of the designed parallel branch winding arrangement connection method change in the circumferential position of the motor to ensure the symmetry of each parallel branch conductor in the circumferential direction of the motor. The plug-in end remains in the radial position of the motor to ensure the consistent size of the single-turn hairpin winding; the welding end changes in the radial position of the motor to connect conductors of different sizes to ensure the symmetry of each parallel branch conductor in the radial direction of the motor.

[0008] Furthermore, the steps of designing the winding structure in step (1) are as follows:

[0009] Assign the height of each layer of conductor to ensure that the total height of the winding is fixed, and realize the orderly increase or decrease of the height of each layer. The height of each layer of conductor of the flat wire winding is designed according to the geometric series distribution. Let the height of the kth layer conductor be h k , then its height relationship satisfies the following formula:

[0010] h k =h 1 ·r k-1 (1)

[0011] In the formula, h 1 is the reference height of the first layer of conductors, r is the common ratio, which is used to control the increment or decrement of each layer height. 1 and r, the height of each layer of conductor forms a geometric series distribution.

[0012] To meet the design requirement of constant slot filling rate, the layer height and total height are related, and the total height is set as H, which satisfies the following conditions:

[0013]

[0014] Taking the minimum AC loss of the motor as the optimization goal, the conductor size is optimized under the constraints of the conductor current density limit and process feasibility, and the optimal size of the hybrid flat wire winding structure with the conductor height gradually increasing from the slot mouth to the slot bottom is obtained.

[0015] Furthermore, the optimization goal is to minimize the AC loss of the motor. The optimization goals are as follows:

[0016] f(x)=min(Wc ) (3)

[0017] Where f is the objective function, x is the design variable related to the conductor size, and W c is the AC loss at the corresponding conductor height.

[0018] Furthermore, considering the process feasibility and current density, the constraints are determined as follows:

[0019] g 1 (x) = 0.5-min(h 1 ~h 4 )≤0 (4)

[0020] g 2 (x) = 10-max(J 1 ~J 4 )≥0 (5)

[0021] Where g 1 and g 2 are the constraints for the manufacturable conductor height and current density, J k is the current density of the kth layer conductor, unit: A, layer height h k , k=1, 2, 3, 4, unit: millimeter.

[0022] Furthermore, in step (2), the method for designing the winding arrangement connection is as follows: the motor winding equipped with a hybrid flat wire winding structure is phase-separated, and is divided into two types: full-pitch winding and short-pitch winding according to different winding arrangement methods: the full-pitch winding adopts the same-slot and same-phase arrangement, and the same-phase winding is arranged in each slot, and the winding is arranged at 60°.

[0023] Phase allocation is carried out according to the arrangement principle of phase belts; the short-pitch winding consists of two types of slots: in-phase slots and out-of-phase slots. The same-phase windings are arranged in the in-phase slots, and the same number of two-phase windings are arranged in the out-of-phase slots. The current phases of the different-phase windings in the out-of-phase slots differ by 60° to reduce the leakage magnetic amplitude in the slots; on the basis of the full-pitch winding, the short-pitch winding further optimizes the magnetic field distribution and motor performance by moving half of the conductors in the slots by one slot in the same direction.

[0024] Furthermore, under the premise of considering the hairpin end connection, a parallel branch winding arrangement connection method that is not completely symmetrical in the radial and circumferential directions of the motor is designed for full-pitch windings and short-pitch windings, that is, a weakly symmetrical arrangement; on this basis, adjustments are made to achieve a parallel branch winding arrangement method that is completely symmetrical in the radial and circumferential directions of the motor, that is, a strongly symmetrical arrangement; in the weakly symmetrical arrangement of the full-pitch winding, the plug-in end of the Hairpin winding only performs a full-pitch slot change connection in the circumferential direction of the motor, and the radial position remains unchanged to connect conductors of the same layer in different slots, and the welding end performs a full-pitch slot change connection in the circumferential direction of the motor, and only performs a long-pitch or short-pitch cross-slot connection when winding between layers 1 and 2 and layers 3 and 4, and at the same time, the welding end also needs to perform layer-changing welding in the radial direction to connect conductors of different slots and different layers; in the strongly symmetrical arrangement of the full-pitch winding, the plug-in end of the Hairpin winding only performs a long-pitch and short-pitch alternating cross-slot connection in the circumferential direction of the motor, and the radial position remains unchanged to connect conductors of different slots and different layers. For conductors in the same slot and the same layer, all welding ends are only connected by full-pitch slot change in the circumferential direction of the motor, and layer change welding is performed in the radial direction to connect conductors in different slots and different layers; in the weakly symmetrical arrangement of short-pitch windings, the plug-in end of the Hairpin winding is only connected by full-pitch slot change in the circumferential direction of the motor, and the radial position remains unchanged to connect conductors in different slots and the same layer, and the welding end is connected by alternating long and short pitch slot change in the circumferential direction of the motor, and layer change welding is performed in the radial direction to connect conductors in different slots and different layers; in the strongly symmetrical arrangement of short-pitch windings, the plug-in end of the Hairpin winding is only connected by alternating long and short pitch cross-slot connection in the circumferential direction of the motor, and the radial position remains unchanged to connect conductors in different slots and the same layer, and the welding end is connected by full-pitch slot change in the circumferential direction of the motor, and a long or short pitch cross-slot connection is only performed once when winding layers 1 and 2 or 3 and 4, and layer change welding is also required at the welding end to connect conductors in different slots and different layers.

[0025] The advantages and positive effects of the present invention are as follows: the present invention proposes a new hybrid flat wire winding structure design method, provides a design method for the height of each layer of conductors and a winding arrangement and connection method for reducing the circulating current between branches. It aims to utilize the conductor structure with different cross-sectional areas in each layer and the specific parallel branch winding arrangement and connection method to effectively weaken the AC loss of the flat wire motor winding and suppress the circulating current between the parallel branches of the motor using a hybrid flat wire winding structure. Finite element results show that the new low AC loss flat wire winding design method proposed in the present invention successfully suppresses the AC effect of the flat wire winding under high-frequency conditions, and significantly reduces the AC loss of the winding and the circulating current between parallel branches. At the same time, this method effectively improves the problem of uneven loss distribution, thereby avoiding the risk of local overheating of the winding. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the hybrid flat wire winding structure.

[0027] Figure 2 Comparison of AC losses of three flat wire winding design methods

[0028] Figure 3 The diagram is a full-pitch arrangement connection diagram of a hybrid flat wire winding structure motor. (a) is a full-pitch weakly symmetrical arrangement connection diagram of a hybrid flat wire winding structure motor. (b) is a full-pitch strongly symmetrical arrangement connection diagram of a hybrid flat wire winding structure motor.

[0029] Figure 4 These are the short-pitch connection diagrams of a hybrid flat wire winding structure motor. (a) is the short-pitch weakly symmetrical connection diagram of a hybrid flat wire winding structure motor. (b) is the short-pitch strongly symmetrical connection diagram of a hybrid flat wire winding structure motor.

[0030] Figure 5 The figures are comparison diagrams of the motor models of a conventional motor with 8-pole 48-slot flat wire winding and an embodiment of the present invention, (a) is a motor model diagram of a conventional motor with 8-pole 48-slot flat wire winding; (b) is a motor model diagram of a full-pole 48-slot hybrid flat wire winding structure; and (c) is a motor model diagram of a short-pole 48-slot hybrid flat wire winding structure.

[0031] Figure 6 This is a comparison chart of the AC copper loss of three motors with different winding structures and weak symmetry.

[0032] Figure 7 This is a comparison chart of the circulating current between branches of a hybrid winding structure motor with full-pitch and short-pitch weakly symmetrical arrangements.

[0033] Figure 8 This is a comparison chart of the circulating current between branches of a hybrid winding structure motor with full-pitch and short-pitch strongly symmetrical arrangements. DETAILED DESCRIPTION

[0034] The following is a detailed description of the implementation of the present invention using an 8p / 48s motor as a design basis. The parameters of the designed motor are shown in Table 1.

[0035] Table 1 Parameters of traditional dual three-phase surface-mount motor

[0036]

[0037]

[0038] (1) Design of hybrid flat wire winding structure. A hybrid flat wire winding structure design method based on geometric series is proposed. This method ensures that the total height of the winding is fixed by reasonably distributing the height of each layer of conductor, while achieving orderly increase or decrease in the height of each layer. The height of each layer of the flat wire winding is designed according to the geometric series distribution. Let the height of the kth layer of conductor be h k , then its height relationship satisfies the following formula:

[0039] h k =h 1 ·r k-1 (1)

[0040] In the formula, h 1 is the reference height of the first layer of conductors, r is the common ratio, which is used to control the increment or decrement of each layer height. 1 and r, the height of each layer of conductor can form a geometric series distribution.

[0041] In order to ensure the overall height of the winding is constant and meet the design requirement of constant slot filling rate, the layer height and the total height can be associated. If the total height is H, the condition is satisfied:

[0042]

[0043] Under the condition of meeting the total height limit, the height of each layer of conductor can be increased or decreased layer by layer by adjusting the value of r, so as to effectively realize the design of different layer heights. In order to minimize the AC loss, the model needs to be optimized, and the optimization objectives are as follows:

[0044] f(x)=min(W c ) (3)

[0045] Where f is the objective function, x is the design variable related to the conductor size, and W c is the AC loss at the corresponding conductor height. Considering process feasibility and current density, determine the constraints. Based on current manufacturing technology, in order to ensure production consistency and qualified rate, the minimum conductor in actual mass production is usually set at around 0.5 mm. Under normal circumstances, in order to ensure the performance and life of the motor, the current density of the flat wire should not exceed 10A / mm 2 . Therefore, the constraints can be defined as follows:

[0046] g 1 (x) = 0.5-min(h 1 ~h 4 )≤0 (4)

[0047] g 2 (x) = 10-max(J 1 ~J 4 )≥0 (5)

[0048] Where g 1 and g 2 are the constraints for the manufacturable conductor height and current density, J kis the current density of the k-th layer conductor. Taking the minimum AC loss of the motor as the optimization goal, the conductor size is optimized under the constraints of slot fill rate, manufacturability and conductor current density limit, and finally the value is obtained, for example Figure 1 The optimal size of the hybrid flat wire winding structure with conductor height increasing gradually from the slot to the slot bottom. The same method is used to design the size of the asymmetric conductor structure with only two conductor heights, and the AC copper loss of the motor at various speeds of the three design schemes of traditional flat wire structure, asymmetric conductor structure and hybrid flat wire winding structure is compared. Figure 2 The results show that the hybrid flat wire winding structure can significantly reduce the AC copper loss at high frequencies compared with the other two design methods, and the reduction effect is more obvious as the speed increases.

[0049] The geometric series conductor modeling method can quickly adjust the height relationship between layers through the common ratio r. The common ratio provides a strong degree of adjustment freedom, which is conducive to achieving symmetrical or asymmetrical height distribution. It has clear formulas and rules, is simple to calculate, and is easy to implement.

[0050] (2) Design the winding arrangement and connection method. The flat wire hairpin winding structure of the present invention includes a three-phase hairpin winding, and the three-phase hairpin winding includes an inlet end, an outlet end, a plug-in end, a welding end, and a conductor in a slot between the plug-in end and the welding end. In order to unify the description, the three-phase winding in the present invention is described using ABC phases. And in order to more clearly describe the winding path of the present invention, Figure 3 to Figure 4 All branch coil groups involved are A-phase coils, and all drawings do not involve B-phase and C-phase coils. The winding method of B-phase and C-phase coils is the same as that of the A-phase coil group. The only difference is that the slot number positions of the input and output ends are different, so they will not be given as examples one by one.

[0051] The coil of each phase of the motor includes four branch windings connected in parallel, the number of stator slots of each phase winding is 2pq, the number of stator slots is 6pq, p is the number of motor pole pairs, q is the number of slots per pole per phase of the flat wire winding; the number of conductor layers of the stator slot is 2M layers, and the span of the coil connecting the conductors of each slot includes three types:

[0052]

[0053] The p, q and M are all positive integers; the inlet and outlet terminals of each phase and each branch are located at the bottom or the slot opening of the stator slot. Figures 2 to 4 In this example, a motor with p=4, q=2, and M=2 is used as an example for explanation.

[0054] First, according to the number of pole pairs p and the number of slots s of the motor, calculate the winding pitch y, usually y = s / 2p, to ensure that the winding adapts to the distribution requirements of the 60° phase belt. Then, evenly distribute the slots to the three phases A, B, and C, so that each phase winding is arranged at an electrical angle of 120°. Taking the full pitch of phase A as an example, the conductor of phase A is arranged in slots 1, 2, 7, and 8 under a pair of poles of the motor, and the conductor arrangement under other pairs of poles is the same. Next, assign the conductor direction in each slot, and specify the polarity of the conductor in the slot according to the star diagram of the motor winding, that is, the conductor directions in slots 1 and 2 and slots 7 and 8 in phase A are opposite, to ensure the generation of symmetrical magnetomotive force, and finally complete the arrangement design of 60° phase belt phase separation.

[0055] Then, combine Figure 3 (a) The connection method of the A-phase branch conductors under the two pairs of poles with a weak symmetry arrangement of the whole pitch is explained. The connection method of the coils under the other two pairs of poles is symmetrical with it. For the sake of unified expression, the k-th layer conductor of slot i is recorded as SiLk. Phase A includes four parallel branches, namely branch 1, branch 2, branch 3 and branch 4. Branch 1 is introduced by the first layer conductor of slot 1, namely S1L1. From S1L1, it is connected to S7L1 without changing layers from the plug-in end with a whole pitch y. At the other end of the motor, from S7L1, it is connected to S13L2 by changing layers from the welding end with a whole pitch y. Then, from S13L2, it is connected to S19L2 by the plug-in end with a whole pitch y without changing layers. After winding around the motor once, it is connected by changing layers. From S19L2, it is connected by a long pitch y 2 The welding end of S2L3 is connected to S2L3 by changing layers, and then S2L3 is connected to S8L3 by the plug-in end of the full pitch y without changing layers, and then S8L3 is connected to S14L4 by changing layers by the welding end of the full pitch y, and then S14L4 is connected to S20L4 by the plug-in end of the full pitch y without changing layers, and finally led out from S20L4; branch 2 is introduced by the first layer conductor of slot 2, that is, S2L1, and is connected to S8L1 from S2L1 by the plug-in end of the full pitch y without changing layers. At the other end of the motor, S8L1 is connected to S14L2 by the welding end of the full pitch y, and then S14L2 is connected to S20L2 by the plug-in end of the full pitch y without changing layers. After wrapping around the motor once, the layer connection is changed, and S20L2 is connected to S8L1 by the short pitch y 1 The welding end of S1L3 is connected to S1L3 by changing layers, and then S1L3 is connected to S7L3 by the plug-in end of the full pitch y without changing layers, and then S7L3 is connected to S13L4 by changing layers by the welding end of the full pitch y, and then S13L4 is connected to S19L4 by the plug-in end of the full pitch y without changing layers, and finally led out from S19L4; branch 3 is introduced by the second layer conductor of slot 1, that is, S1L2, and is connected to S19L1 by changing layers from S1L2 by the welding end of the full pitch y. At the other end of the motor, S19L1 is connected to S13L1 by the plug-in end of the full pitch y without changing layers, and then S13L1 is connected to S7L2 by changing layers by the welding end of the full pitch y, and after wrapping around the motor once, the layer connection is changed, and S7L2 is connected to S19L1 by the short pitch y1 The welding end of S2L4 is connected to S20L3 by changing layers from S2L4 through the welding end of the whole pitch y, and then S20L3 is connected to S14L3 by the plug-in end of the whole pitch y without changing layers, and then S14L3 is connected to S8L4 by changing layers from the welding end of the whole pitch y, and finally led out from S8L4; branch 4 is introduced by the second layer conductor of slot 2, that is, S2L2, and is connected to S20L1 by changing layers from S2L2 through the welding end of the whole pitch y, and at the other end of the motor, S20L1 is connected to S14L1 by the plug-in end of the whole pitch y without changing layers, and then S14L1 is connected to S8L2 by changing layers from the welding end of the whole pitch y, and after winding around the motor once, the layer connection is changed, and S8L2 is connected to S14L1 by the long pitch y from S14L1. 1 The welding end of the hybrid flat wire winding is connected to S1L4 by changing the layer, and then the welding end of S1L4 is connected to S19L3 by changing the layer, and then the plug-in end of S19L3 is connected to S13L3 by changing the layer without changing the layer, and then the welding end of S13L3 is connected to S7L4 by changing the layer, and finally it is led out from S7L4. This example is a hybrid flat wire winding A-phase branch with a weak symmetrical arrangement of full pitch. The four branches are not completely symmetrical in the radial and circumferential directions of the motor, which will generate a certain amount of circulating current. However, this arrangement and connection scheme only requires y when the 1st and 2nd layers are wound in layers with the 3rd and 4th layers. 1 or 2 The winding connection is of pitch, and the other times it is y-pitch winding connection, which has a simple structure.

[0056] Combination Figure 3 (b) The connection method of the A-phase branch conductors under the two pairs of poles is described in a strongly symmetrical arrangement. The connection method of the coils under the other two pairs of poles is symmetrical. For the sake of unified description, the k-th conductor of slot i is recorded as SiLk. Phase A contains four parallel branches, namely branch 1, branch 2, branch 3, and branch 4. Branch 1 is introduced by the first layer conductor of slot 1, namely S1L1. From S1L1, there is a long pitch y 2 The plug-in end of the motor is connected to S8L1 without changing layers. At the other end of the motor, the soldering end of S8L1 with a full pitch y is connected to S14L2, and then the soldering end of S14L2 with a short pitch y is connected to S14L2. 1 The plug-in end of the wire is connected to S19L2 without changing layers. After wrapping around the motor once, it is connected to S19L2 by changing layers from the welding end of the full pitch y to S1L3, and then from S1L3 by the long pitch y 2 The plug-in end is connected to S8L3 without changing layers, and then the whole pitch y welding end of S8L3 is connected to S14L4, and then the short pitch y welding end of S14L4 is connected to S8L3. 1 The plug-in end is connected to S19L4 without changing layers, and finally led out from S19L4; branch 2 is introduced by the first layer conductor of slot 2, that is, S2L1, and from S2L1 by the short pitch y 1The plug-in end of the motor is connected to S7L1 without changing layers. At the other end of the motor, the soldered end of S7L1 with a full pitch y is connected to S13L2, and then the soldered end of S13L2 with a long pitch y is connected to S13L2. 2 The plug-in end of the wire is connected to S20L2 without changing layers. After wrapping around the motor once, it is connected to S20L2 by changing layers from the welding end of the full pitch y to S2L3, and then from S2L3 by the short pitch y 1 The plug-in end is connected to S7L3 without changing layers, and then the whole pitch y welding end of S7L3 is connected to S13L4, and then the long pitch y welding end of S13L4 is connected to S13L4. 2 The plug-in end is connected to S20L4 without changing layers, and finally led out from S20L4; branch 3 is introduced by the second layer conductor of slot 1, that is, S1L2, and is connected to S19L1 from S1L2 by changing layers from the welding end of the full pitch y, and at the other end of the motor from S19L1 by the short pitch y 1 The plug-in end of the wire is connected to S14L1 without changing layers, and then S14L1 is connected to S8L2 by changing layers through the welding end of the full pitch y. After wrapping around the motor once, change layers and connect from S8L2 to S2L4 by changing layers through the welding end of the full pitch y, and then S2L4 is connected to S20L3 by changing layers through the welding end of the full pitch y, and then S20L3 is connected to S8L2 by changing layers through the welding end of the full pitch y. 2 The plug-in end is connected to S13L3 without changing layers, and then connected to S7L4 from S13L3 by changing layers through the full pitch y welding end, and finally led out from S7L4; branch 4 is introduced by the second layer conductor of slot 2, that is, S1L2, and connected to S20L1 from S1L2 by changing layers through the full pitch y welding end, and at the other end of the motor from S20L1 by the short pitch y 1 The plug-in end of the wire is connected to S13L1 without changing layers, and then S13L1 is connected to S7L2 by changing layers from the welding end of the full pitch y. After wrapping around the motor once, change layers and connect from S7L2 to S1L4 by changing layers from the welding end of the full pitch y, and then S1L4 is connected to S19L3 by changing layers from the welding end of the full pitch y, and then S19L3 is connected to S19L3 by the long pitch y. 2 The plug-in end is connected to S14L3 without changing layers, and then connected to S8L4 by changing layers from S14L3 through the full pitch y welding end, and finally led out from S8L4. This example is a hybrid flat wire winding A-phase branch with full pitch strong symmetrical arrangement connection. The four branches are completely symmetrical in the radial and circumferential directions of the motor, and the motor end needs y 1 , y, and y 2 The pitch windings are connected alternately, and the structure is complex, but the circulating current can be completely eliminated.

[0057] Combination Figure 4(a) The short-distance weakly symmetrical arrangement and connection of the A-phase branch conductors under the two pairs of poles is described. The connection of the coils under the other two pairs of poles is symmetrical to it. For the sake of unified description, the k-th layer conductor of slot i is recorded as SiLk. Phase A contains four parallel branches, namely branch 1, branch 2, branch 3, and branch 4. Branch 1 is introduced by the first layer conductor of slot 1, namely S1L1. From S1L1, it is connected to S7L1 without changing layers from the plug-in end of the full pitch y. At the other end of the motor, it is connected from S7L1 to the long pitch y 2 The soldering end of S14L2 is connected to S14L2 by changing layers, and then the plug-in end of S14L2 is connected to S20L2 without changing layers by the plug-in end of the full pitch y. After wrapping around the motor once, the connection is changed layers. The soldering end of S20L2 is connected to S2L3 by changing layers by the soldering end of the full pitch y, and then the plug-in end of S2L3 is connected to S8L3 without changing layers, and then the plug-in end of S8L3 is connected to S20L2 by the plug-in end of the full pitch y. 2 The welding end is connected to S15L4 by changing layers, and then connected to S21L4 by the plug-in end of the full pitch y without changing layers from S15L4, and finally led out from S21L4; branch 2 is introduced by the second layer conductor of slot 2, that is, S2L1, and connected to S8L1 by the plug-in end of the full pitch y without changing layers from S2L1. At the other end of the motor, it is connected to S8L1 by the short pitch y 1 The soldered end of the motor is connected to S13L2 by changing the layer, and then the plug-in end of the full pitch y from S13L2 is connected to S19L2 without changing the layer. After wrapping around the motor once, the layer connection is changed. From S19L2, the long pitch y 2 The soldering end of +1 is connected to S3L3 by changing layers, and then the plug-in end of S3L3 with full pitch y is connected to S9L3 without changing layers, and then the short pitch y is connected to S9L3 by S9L3. 1 The welding end is connected to S14L4 by changing the layer, and then connected to S20L4 by the full pitch y plug-in end from S14L4 without changing the layer, and finally led out from S20L4; branch 3 is introduced by the second layer conductor of slot 1, that is, S1L2, and is led from S1L2 by the short pitch y 1 The soldered end of the motor is connected to S20L1 by changing layers, and the other end of the motor is connected to S14L1 by the plug-in end of the full pitch y without changing layers, and then from S14L1 to the long pitch y 2 The soldered end of the motor is connected to S7L2 by changing the layer. After wrapping around the motor once, the layer connection is changed. From S7L2, the short pitch y 1 The soldering end of S2L4 is connected to S2L4 by changing the layer, and then the soldering end of S2L4 with short pitch y is connected to S21L3 by changing the layer, and then the plug-in end of S21L3 with full pitch y is connected to S15L3 without changing the layer, and then the soldering end of S13L3 with long pitch y is connected to S21L3 by changing the layer. 1 The welding end is connected to S8L4 in a layer-by-layer manner and finally led out from S8L4; branch 4 is introduced from the second layer conductor of slot 2, i.e. S1L2, and is led from S1L2 by the long pitch y 2The soldered end of the motor is connected to S19L1 by changing the layer, and the other end of the motor is connected to S13L1 by the plug-in end of the full pitch y without changing the layer, and then from S13L1 to the short pitch y 1 The welding end of the motor is connected to S8L2 by changing the layer. After wrapping around the motor once, the layer connection is changed. From S8L2, the short pitch y 1 The welding end of the layer is connected to S3L4, and then from S3L4 to the long pitch y 2 The soldering end of the S20L3 is connected to S20L3 by changing the layer, and then the full pitch y plug-in end of S20L3 is connected to S14L3 without changing the layer, and then the short pitch y plug-in end of S14L3 is connected to S14L3 by changing the layer. 1 The welding end is connected to S9L4 in a layer-by-layer manner and finally led out from S9L4. This example is a short-distance weakly symmetrical arrangement connection of the hybrid flat wire winding A-phase branch. The four branches are not completely symmetrical in the radial and circumferential directions of the motor, and due to the presence of out-of-phase slots, a large circulating current will be generated between the branches. 1 , y, and y 2 The pitch windings are connected alternately.

[0058] Figure 4 (b) is the connection diagram of the short-distance strong symmetrical arrangement of the A-phase branch of the hybrid flat wire winding structure, which is slightly different from the full-distance strong symmetrical arrangement, that is, the layer-changing winding increases the pitch of one slot when the branch changes between the 1st and 2nd layers and the 3rd and 4th layers, so that the conductors of the 3rd and 4th layers are shifted to the right by one slot as a whole, so that one semiconductor under each phase is distributed in the out-of-phase slot, the purpose is to reduce the slot leakage magnetic amplitude and thus reduce the AC loss. This example makes each parallel branch winding symmetrically distributed in the same-phase slot and the out-of-phase slot on the basis of the short-distance arrangement, which can completely avoid the circulation between the branches.

[0059] It can be seen from the four examples that in order to ensure the symmetry of the arrangement, the branches 3 and 4 of the two arrangement methods require two I-pin conductors as layer-changing windings to perform layer-changing welding connection on the hairpin conductors at both ends of the 1st and 2nd layers and the 3rd and 4th layers of the branch.

[0060] (3) Finite element simulation verification. Based on steps (1) and (2), the finite element simulation model of the flat wire motor with a new hybrid flat wire winding structure and a full-pitch and short-pitch weak and strong symmetrical arrangement and the flat wire motor with a traditional winding structure is obtained. Figure 5 As shown in the figure. The AC loss of the motor with three different weakly symmetrical winding structures at a speed of 15000r / min is obtained through simulation, as shown in the figure. Figure 6As shown in the figure, compared with the traditional flat wire winding structure, the AC loss of the motor with hybrid flat wire winding structure is significantly reduced at both full and short pitches. In addition, due to the fact that the out-of-phase slots reduce the slot leakage magnetic amplitude, the short-pitch arrangement has lower AC loss than the full-pitch arrangement, thus verifying the effectiveness of the hybrid flat wire winding structure. However, due to the different distribution of leakage magnetic in the out-of-phase slots and the same-phase slots in the short-pitch arrangement, the circulating current generated by the weakly symmetrical branch arrangement is higher than that of the full-pitch arrangement. The branch circulating currents of the full-pitch and short-pitch weakly symmetrical arrangements are shown in the figure below. Figure 7 As shown in , this will cause local overheating of the branch winding, so a completely symmetrical strong symmetrical arrangement connection scheme is required to suppress the circulating current. The branch circulating current of the full-span and short-span strong symmetrical arrangement is shown in Figure 8 As shown in Table 2, this arrangement can completely eliminate the branch circulation, thus verifying the effectiveness of the strong symmetrical arrangement of the branches. Finally, the electromagnetic performance parameters of the five motors were sorted out, as shown in Table 2:

[0061] Table 2 Performance comparison of flat wire permanent magnet synchronous motor

[0062]

[0063] The results show that the hybrid winding structure design method can suppress the AC effect of flat wire conductors at high frequencies and effectively reduce the AC loss of motor windings. At the same time, the hybrid winding structure design method uses weakly symmetrical and strongly symmetrical winding arrangement and connection methods to achieve the symmetry of each parallel branch in the radial and tangential directions of the motor, suppress the circulating current between branches on the basis of reducing AC loss, balance the AC loss of each parallel branch, and improve the efficiency of the flat wire permanent magnet synchronous motor.

Claims

1. A method for designing a low AC loss flat wire winding, comprising the following steps: (1) The number of conductor layers and the height of the first conductor layer are used as parameter variables. The height of each conductor layer is modeled using a geometric series of flat wire conductors. Under the premise of ensuring that the slot fill rate remains unchanged, the motor AC loss is minimized as the optimization goal. Under the constraints of the conductor current density limit and process feasibility, the conductor size is optimized to design a hybrid flat wire winding structure. (2) According to the rules for suppressing the circulating current of the parallel branch, a weakly symmetrical and strongly symmetrical winding arrangement scheme is designed on the basis of the hybrid flat wire winding structure. The plug-in end and the welding end of the Hairpin winding of the designed parallel branch winding arrangement connection method change in the circumferential position of the motor to ensure the symmetry of each parallel branch conductor in the circumferential direction of the motor. The plug-in end remains unchanged in the radial position of the motor to ensure the consistent size of the single-turn hairpin winding. The radial position of the welding end in the motor will change to connect conductors of different sizes and ensure the symmetry of the conductors of each parallel branch in the radial direction of the motor.

2. The method for designing a low AC loss flat wire winding according to claim 1, characterized in that: Step (1) The steps for designing the winding structure are as follows: Assign the height of each layer of conductor to ensure that the total height of the winding is fixed, and realize the orderly increase or decrease of the height of each layer. The height of each layer of conductor of the flat wire winding is designed according to the geometric series distribution. Let the height of the kth layer conductor be h k , then its height relationship satisfies the following formula: h k =h1·r k-1 (1) In the formula, h1 is the reference height of the first layer of conductors, and r is the common ratio, which is used to control the increasing or decreasing amplitude of the height of each layer. By selecting h1 and r, the height of each layer of conductors forms a geometric series distribution. To meet the design requirement of constant slot filling rate, the layer height and total height are related, and the total height is set as H, which satisfies the following conditions: Taking the minimum AC loss of the motor as the optimization goal, the conductor size is optimized under the constraints of the conductor current density limit and process feasibility, and the optimal size of the hybrid flat wire winding structure with the conductor height gradually increasing from the slot mouth to the slot bottom is obtained.

3. The method for designing a low AC loss flat wire winding according to claim 1, characterized in that: The optimization goal is to minimize the AC loss of the motor. The optimization goals are as follows: f(x)=min(W c ) (3) Where f is the objective function, x is the design variable related to the conductor size, and W c is the AC loss at the corresponding conductor height.

4. The method for designing a low AC loss flat wire winding according to claim 3, characterized in that: Considering process feasibility and current density, the constraints are determined as follows: g1(x)=0.5-min(h1~h4)≤0 (4) g2(x)=10-max(J1~J4)≥0 (5) Where g1 and g2 are the constraints for the conductor height and current density that can be manufactured, respectively, and J k is the current density of the kth layer conductor, unit: A, layer height h k , k=1, 2, 3, 4, unit: millimeter.

5. The method for designing a low AC loss flat wire winding according to claim 1, characterized in that: In step (2), the method for designing the winding arrangement connection is as follows: the motor winding equipped with a hybrid flat wire winding structure is phase-split, and is divided into two types: full-pitch winding and short-pitch winding according to different winding arrangement methods: the full-pitch winding adopts the same-slot and same-phase arrangement, and the same-phase winding is arranged in each slot, and the phase is allocated according to the arrangement principle of the 60° phase band; the short-pitch winding is composed of two types of slots: the same-phase slot and the different-phase slot, wherein the same-phase winding is arranged in the same-phase slot, and the same number of two-phase windings are arranged in the different-phase slot, and the current phases of the different-phase windings in the different-phase slots differ by 60° to reduce the amplitude of the magnetic leakage in the slot; Based on the full-pitch winding, the short-pitch winding further optimizes the magnetic field distribution and motor performance by moving half of the conductors in the slot by one slot in the same direction.

6. The method for designing a low AC loss flat wire winding according to claim 1, characterized in that: Under the premise of considering the hairpin end connection, a parallel branch winding arrangement connection method that is not completely symmetrical in the radial and circumferential directions of the motor is designed for full-pitch windings and short-pitch windings, namely a weakly symmetrical arrangement; on this basis, adjustments are made to achieve a parallel branch winding arrangement method that is completely symmetrical in the radial and circumferential directions of the motor, namely a strongly symmetrical arrangement; in the weakly symmetrical arrangement of the full-pitch winding, the plug-in end of the Hairpin winding is only connected by a full-pitch slot change in the circumferential direction of the motor, and the radial position remains unchanged to connect conductors of the same layer in different slots, and the welding end is connected by a full-pitch slot change in the circumferential direction of the motor, and only a long-pitch or short-pitch cross-slot connection is performed when winding between layers 1 and 2 and layers 3 and 4, and the welding end also needs to be layer-changed in the radial direction. In the strong symmetrical arrangement of full-pitch windings, the plug-in end of the Hairpin winding only performs cross-slot connections with alternating long pitches and short pitches in the circumferential direction of the motor, and the radial position remains unchanged to connect conductors in different slots and the same layer. All welding ends only perform full-pitch slot-changing connections in the circumferential direction of the motor, and perform layer-changing welding in the radial direction to connect conductors in different slots and different layers. In the weak symmetrical arrangement of short-pitch windings, the plug-in end of the Hairpin winding only performs full-pitch slot-changing connections in the circumferential direction of the motor, and the radial position remains unchanged to connect conductors in different slots and the same layer. The welding end performs long-pitch and short-pitch slot-changing connections in the circumferential direction of the motor, and performs layer-changing welding in the radial direction to connect conductors in different slots and different layers. In the strongly symmetrical arrangement of short-pitch windings, the wire end of the Hairpin winding only performs alternating long-pitch and short-pitch cross-slot connections in the circumferential direction of the motor, and the radial position remains unchanged to connect conductors of the same layer in different slots. The welding end performs full-pitch slot-changing connections in the circumferential direction of the motor, and only performs a long-pitch or short-pitch cross-slot connection when the winding is switched between layers 1 and 2 and layers 3 and 4. At the same time, the welding end also needs to perform layer-changing welding in the radial direction to connect conductors of different layers in different slots.

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