Methods for Optimizing Variable Cross-Section End-Transposition Windings in Additive Manufacturing

Abstract

This invention discloses a variable cross-section end-transposed winding for additive manufacturing and its optimization method, belonging to the field of motor winding design optimization. Based on a traditional flat wire winding with a uniform cross-section, a variable cross-section and end-transposed design were implemented, optimizing the conductor cross-sectional height and the spacing between conductors. Based on an analytical model of AC copper loss and considering the distribution of magnetic flux density within the slots, an optimization model for eddy current and DC losses of the winding was established, neglecting circulating current losses, thus obtaining the conductor cross-sectional height parameter. The two-layer transposed structure of the variable cross-section winding balances the potential difference in the branches, reducing circulating current losses. The conductor spacing was optimized, and finite element analysis and comparison were performed between the variable cross-section end-transposed winding and the uniform cross-section end-transposed winding. The variable cross-section transposed structure of this invention can effectively suppress high-frequency AC copper losses in electrically excited doubly salient pole motors operating under high-speed conditions, and has broad application prospects.

Description

Technical Field

[0001] This invention relates to the field of motor winding design optimization technology, and in particular to a variable cross-section end-transposed winding for additive manufacturing and its optimization method. Background Technology

[0002] Aircraft electrification is a crucial development direction for the future of aviation and a significant application of new energy technologies in the field. One major type of motor is the electrically excited doubly salient pole brushless DC generator (DSBLDCG), which offers advantages such as convenient magnetic adjustment and reliable structure. However, due to its high magnetic field frequency and high harmonic content, the windings suffer from high-frequency AC losses, reducing efficiency and causing significant heat generation. Commonly used windings include flat wire, Lobel wire, shaped windings, and Litz windings. Flat wire offers advantages such as high slot fill factor and high torque density, but suffers from significant AC losses. Lobel wire, with its transposed rectangular solid strands, reduces circulating currents but has significant eddy current losses, making it unsuitable for small and medium-sized motors. Multi-strand parallel shaped windings reduce eddy current losses but exhibit inter-strand circulating currents, reducing slot fill factor. Litz windings, made of fine copper wire, are widely used in many high-speed applications; under complete transposition, AC losses can be significantly reduced, but they have low slot fill factor and poor heat dissipation.

[0003] Therefore, how to improve the winding method in electrically excited doubly salient brushless DC generators so as to effectively suppress the AC loss of the windings while ensuring the slot fill factor has become a research topic. Summary of the Invention

[0004] The embodiments of the present invention provide a variable cross-section end-transformed winding for additive manufacturing and its optimization method, which can effectively suppress the AC loss of the winding while ensuring the slot fill factor.

[0005] To achieve the above objectives, the embodiments of the present invention adopt the following technical solutions:

[0006] A method for optimizing variable cross-section end-transformed windings used in additive manufacturing, such as... Figure 12 As shown, it includes:

[0007] S1. Obtain the initial information of the end transposed winding to be optimized, and establish an analytical model of the winding AC loss based on the initial information; wherein, before the cross-sectional height optimization, the end of the initial winding has not been transposed, and is not transposed at this time. The end transposition optimization is performed after the height optimization.

[0008] S2. Based on the analytical model of the winding AC loss and the distribution of magnetic flux density in the slot, a first optimization model is established. The output of the optimization model includes the height of the optimized conductor cross section.

[0009] S3. Establish a second optimization model. The output of the second optimization model includes the optimized spacing value between the winding conductors.

[0010] S4. The output results of the first optimization model and the second optimization model are transmitted to the additive manufacturing equipment, which is used to manufacture the end transposed winding of the electrically excited doubly salient pole motor. The transposition is performed at the ends of the winding, and the additive manufacturing equipment manufactures the entire variable cross-section winding as a whole. The ends of the final manufactured variable cross-section winding have undergone transposition optimization.

[0011] The additively manufactured variable cross-section end-transposed winding of the electrically excited doubly salient pole motor includes: a 6-turn series coil, each turn having 3 parallel-wound conductors distributed at different positions within the slot. The conductor cross-section is rectangular, and the variable cross-section refers to the different cross-sectional heights of the conductors at different positions within the slot and the varying spacing between the conductors. All windings are two-layer transposed structures. The design principle is as follows: based on the analytical model of the winding's AC losses, combined with the distribution of magnetic flux density within the slot, and neglecting circulating current losses, an optimization model for the winding's eddy current and DC losses is established to obtain the conductor cross-sectional height parameters. The two-layer transposed structure of the variable cross-section winding is designed to balance the potential difference in the branches and reduce circulating current losses. Finally, an optimization algorithm is designed to optimize the conductor spacing, and finite element analysis and comparison are performed between the variable cross-section end-transposed winding and the constant cross-section end-transposed winding.

[0012] Specifically, in S1, the analytical model for winding AC losses includes: P Cu =P Cu_dc +P eddy +P cir , where P Cu P represents the AC loss of the winding. Cu_dc P represents the DC loss of the winding. eddy P represents the eddy current loss of the winding. cir This represents the circulating current loss of the winding; where,

[0013] The initial information includes the number of winding turns N and the effective value of the winding current I. rms The resistance R of the winding, the axial length l of the winding, the resistivity ρ of the conductor, the length a1 and width h1 of the rectangular winding, and the components B of the magnetic flux density along the x and y axes through each rectangular winding cross section. x and B y .

[0014] Conductors at different positions in the slot generate different induced electromotive forces due to varying magnetic field environments, resulting in circulating current losses between the strands. These circulating current losses can be obtained through methods including:

[0015] Where s is the differential operator, L is the matrix of the three layers of self-inductance and mutual inductance of the winding, E1 is the unit row vector, and E2 is the unit column vector.

[0016] P cir =i 1cir 2 R1+i 2cir 2 R2+i 3cir 2 R3, where u1~u3 and i1~i3 are the induced voltage and current of the three parallel-wound wires, respectively, and L j,j For the self-induction of the j-th layer, L i,j For the mutual inductance between the i-th layer and the j-th layer, R j Let t be the resistance of the j-th layer, and t be time.

[0017] Specifically, in S2, the conductor cross-sectional parameters are optimized: the eddy current loss of a rectangular conductor is positively correlated with its area. As the distance from the conductor to the slot opening increases, the magnetic flux density of the conductor decreases. Compared to dB... x / dt, dB y The effect of / dt on eddy current losses is small and can be ignored. Changing the conductor cross-sectional area only requires changing the conductor height. To design different conductor heights within the slot to minimize eddy current losses in the winding, a single-objective programming calculation model was established, ignoring circulating current losses in the winding. The first optimization model includes:

[0018] Where z is the sum of eddy current losses and DC losses in the winding, and a and h i B represents the length and width of the rectangular conductor, respectively. ix Let d be the magnetic flux density along the x-axis on the cross-section of each rectangular conductor, and h be the distance between adjacent conductors. τ h is the total height of the winding. min Let i be the minimum allowable thickness of the conductor due to limitations in additive manufacturing technology, i is a positive integer representing the number of the rectangular conductor, n is the total number of conductors in the slot, and I is the effective value of the winding current. According to Ampere's circuital law, the magnetic flux density of all conductors in the same slot can be considered linear. The magnetic flux density at the geometric center of the conductor at the bottom of the slot can be obtained using a finite element model, and substituting it into the calculation model yields the cross-sectional width of the winding.

[0019] Specifically, a two-layer transposition structure is adopted in the additive manufacturing process of the end-transformed winding. Optimization of the end-transformation structure for the variable cross-section winding: Considering the limitations of additive manufacturing processes, a two-layer transposition structure for the winding was designed. The inductance and voltage data of the winding can be extracted from the finite element model.

[0020] Specifically, in S3, the second optimization model includes: changing the cross-sectional height of the bottom conductor while keeping the total height of the winding constant, thereby increasing the induced electromotive force in the conductor of the branch with smaller current, thus reducing the circulating current loss caused by the potential difference between strands; selecting the optimized spacing position based on equal spacing, combined with the optimal transposition structure and initial current waveform; selecting the proportion of reducing the cross-sectional height of the bottom winding, and limiting the maximum spacing that can be increased between conductors in combination with the process; and the conductor voltage before and after changing the spacing. The conductor voltage before and after changing the spacing satisfies the following conditions: Among them, U i ,U' i These represent the voltages of the conductors before and after changing the spacing, where U0 is the voltage of the conductor at the bottom of the slot, and h... i d represents the distance between the geometric center of the conductor and the bottom conductor of the trench, and d represents the increased spacing.

[0021] The second optimization model is loaded using a MATLAB program to obtain the minimum circulation loss and the corresponding spacing value.

[0022] In a preferred embodiment, the end transposed windings of the electrically excited doubly salient pole motor are integrally manufactured using additive manufacturing equipment. The conductor material in the windings is copper.

[0023] This invention provides a variable cross-section end-transposed winding for additive manufacturing and its optimization method. Based on a traditional uniform cross-section flat wire winding, it incorporates a variable cross-section and end-transposition design, optimizing the conductor cross-sectional height and conductor spacing. The winding comprises 6-turn series coils, each with 3 parallel-wound conductors distributed at different positions within the slot. The conductor cross-section is rectangular, and the variable cross-section refers to the varying cross-sectional height of the conductors at different positions within the slot, as well as the different conductor spacings. Based on an AC copper loss analytical model and considering the magnetic flux density distribution within the slot, an optimization model for eddy current and DC losses of the winding is established, neglecting circulating current losses, yielding the conductor cross-sectional height parameter. The invention also explores a two-layer transposition structure for the variable cross-section winding to balance the potential difference in the branches and reduce circulating current losses. Specifically, a novel optimization method is used to optimize the conductor spacing, and finite element analysis and comparison are performed between the variable cross-section end-transposed winding and the uniform cross-section end-transposed winding. Compared with traditional uniform cross-section rectangular windings, the variable cross-section transposition structure of this invention can effectively suppress high-frequency AC copper losses in electrically excited doubly salient pole motors operating at high speeds. Thus, it can effectively suppress AC losses of the windings while ensuring slot fill factor, and has broad application prospects. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 The three-layer winding structure and circuit diagram with variable cross-section and two-layer transposition provided in the embodiments of the present invention;

[0026] Figure 2 The optimized cross-sectional height of the conductor in the slot and the magnetic flux density map at the geometric midpoint of the conductor are provided for embodiments of the present invention.

[0027] Figure 3 This is a schematic diagram showing the positional distribution of each conductor within the groove, provided in an embodiment of the present invention.

[0028] Figure 4 The loss of each conductor of a three-layer winding with equal cross-section provided in an embodiment of the present invention under the conditions of motor speed of 12000 r / min, excitation current of 6A, and output voltage of 60V;

[0029] Figure 5 The loss of each conductor of the variable cross-section three-layer winding provided in the embodiment of the present invention under the conditions of motor speed of 12000r / min, excitation current of 6A, and output voltage of 60V;

[0030] Figure 6 The optimal two-layer transposition circuit diagram and current waveform diagram of the equal cross-section winding provided in the embodiments of the present invention;

[0031] Figure 7 The optimal two-layer transposition circuit diagram and current waveform diagram of the variable cross-section winding provided in the embodiments of the present invention;

[0032] Figure 8 A loss comparison diagram between a variable cross-section two-layer transposed winding and a constant cross-section two-layer transposed winding provided in an embodiment of the present invention;

[0033] Figure 9 The present invention provides a flowchart for optimizing conductor spacing and a diagram for optimizing the spacing of variable cross-section transposed windings.

[0034] Figure 10 This is a schematic diagram of the optimized winding cross-section provided in an embodiment of the present invention;

[0035] Figure 11 The current waveform diagram of the variable cross-section transposed winding with optimized spacing provided in the embodiment of the present invention.

[0036] Figure 12 This is a schematic diagram of the method flow provided in an embodiment of the present invention. Detailed Implementation

[0037] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Embodiments of the present invention will be described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in the specification of the present invention means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. It should be understood that when we say an element is “connected” or “coupled” to another element, it can be directly connected or coupled to the other element, or there may be intermediate elements. Furthermore, “connected” or “coupled” as used herein can include wireless connections or couplings. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the meaning consistent with their meaning in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0038] This invention provides a method for optimizing variable cross-section end-transformed windings used in additive manufacturing. Figure 1 The method includes: a three-layer winding structure and circuit diagram with variable cross-section two-layer transposition;

[0039] (1) Establish an analytical model for winding AC losses: Winding AC losses include circulating current losses, eddy current losses, and DC losses, which can be calculated using formula (1). The DC losses and eddy current losses of the windings can be calculated using formulas (2) and (3).

[0040] P Cu =P Cu_dc +P eddy +P cir (1)

[0041]

[0042]

[0043] Where N is the number of turns in the winding, I rms R is the effective value of the winding current, l is the winding resistance, l is the axial length of the winding, ρ is the conductor resistivity, a1 and h1 are the length and width of the rectangular winding, respectively, and B x and B y It is the component of the magnetic flux density along the x-axis and y-axis of each rectangular winding cross section.

[0044] The conductors at different positions in the slot generate different induced electromotive forces due to the different magnetic field environments they are in, resulting in circulating current losses between the strands. These losses can be calculated using formula (4-5).

[0045]

[0046]

[0047] Where u and i are the induced voltage and current of the three-strand parallel wire, respectively, and L j,j For the self-induction of the j-th layer, L i,j For the mutual inductance between the i-th layer and the j-th layer, R j Let E1 be the resistance of the j-th layer, E2 be the unit row vector, and E1 be the unit column vector.

[0048] (2) Optimization of conductor cross-sectional parameters: The eddy current loss of a rectangular conductor is positively correlated with its area. As the distance between the conductor and the slot opening increases, the magnetic flux density of the conductor decreases. Compared to dB... x / dt, dB y The effect of / dt on eddy current losses is small and can be ignored. To change the cross-sectional area of ​​the conductor, only the height of the conductor cross-section needs to be changed. In order to design the height of different conductors in the slot to minimize eddy current losses in the winding, a single-objective programming calculation model was established under the premise of ignoring the circulating current losses in the winding, as shown in formulas (6) and (7).

[0049]

[0050]

[0051] Where z is the sum of eddy current losses and DC losses in the winding, l is the axial length of the conductor, ρ is the conductor resistivity, and a and h i B represents the length and width of the rectangular conductor, respectively. ix Let d be the magnetic flux density along the x-axis on the cross-section of each rectangular conductor, and h be the distance between adjacent conductors. τ h is the total height of the winding. min This refers to the minimum allowable thickness of the conductor due to limitations in additive manufacturing technology.

[0052] According to Ampere's circuital law, the magnetic flux density of all conductors in the same slot can be considered linear. Using a finite element model, the magnetic flux density at the geometric center of the conductor at the bottom of the slot can be obtained; substituting this density into the calculation model yields the cross-sectional width of the winding.

[0053] (3) Optimization of the transposition structure at the ends of the variable cross-section winding: Considering the limitations of additive manufacturing, a two-layer transposition structure for the winding was designed. The inductance and voltage data of the winding can be extracted from the finite element model. Based on formula (4-7), the optimal transposition structure of the winding can be obtained.

[0054] (4) Optimization design of conductor spacing in variable cross-section windings: By reducing the cross-sectional height of the thicker conductor at the bottom of the slot, while keeping the total height of the winding constant, the spacing between the selected conductors is increased, thereby increasing the induced electromotive force in the conductors of the branch with smaller current, and further reducing the circulating current loss caused by the potential difference between strands. Based on equal spacing, the optimal spacing position is selected by combining the optimal transposition structure and the initial current waveform; the proportion of the cross-sectional height of the winding at the bottom of the slot is selected, and the maximum spacing that can be increased between conductors is limited by the process; the voltage of the conductors before and after changing the spacing can be simplified as shown in (8):

[0055]

[0056] Among them, U i ,U' i These represent the voltages of the conductors before and after changing the spacing, where U0 is the voltage of the conductor at the bottom of the slot, and h... i d represents the distance between the geometric center of the conductor and the bottom conductor of the trench, and d represents the increased spacing.

[0057] Combining formulas (4-5) and (8), the minimum circulating loss and the corresponding spacing value at the selected location can be obtained by traversing the MATLAB program.

[0058] Figure 2 This diagram shows the positional distribution of each conductor within the slot. The conductors in the slot on the left are labeled AP1 to AP9 from the bottom to the top, and the conductors in the slot on the right are labeled AN1 to AN9 from the bottom to the top.

[0059] Figure 3 The optimized cross-sectional height of the conductor in the slot and the magnetic flux density map at the geometric midpoint of the conductor are shown. The optimized cross-sectional height, untransposed three-layer winding is applied to an electrically excited doubly salient pole motor for simulation, and the magnetic flux density at the geometric midpoint of all windings is extracted for verification. Figures 1-9 correspond to... Figure 2 In the diagram, the conductor designations are as follows: AN_H represents the conductor height within the AN slot, and AN_dBx / dt represents the magnetic flux density at the geometric center of the conductor within the AN slot. The same logic applies to AP. It can be seen that the magnetic flux density at the geometric center of the conductor within the slot is linear, and the cross-sectional height gradually narrows from the bottom to the opening of the slot.

[0060] Figure 4 The figure shows the losses of each conductor in a three-layer winding with uniform cross-section under the conditions of motor speed 12000 r / min, excitation current 6A, and output voltage 60V. The losses of this three-layer winding with uniform cross-section represent AC losses neglecting circulating currents. As can be seen from the figure, the DC losses of all conductors are the same, and the eddy current losses increase closer to the slot opening. The total AC loss of this winding with uniform cross-section is 72.39W, of which the eddy current losses and DC losses are 36.40W and 35.99W, respectively.

[0061] Figure 5 This paper describes the losses of each conductor in a variable cross-section three-layer winding under the conditions of a motor speed of 12000 r / min, excitation current of 6A, and output voltage of 60V. This three-layer variable cross-section winding is untransposed, with only conductor height optimization, and the losses represent AC losses neglecting circulating current. The figure shows that the DC loss of the conductor increases closer to the slot opening, mainly due to the change in conductor resistance caused by the change in conductor cross-section. Eddy current losses are generally evenly distributed among the conductors within the slots, with larger eddy current losses at the slot opening. The total AC loss of this variable cross-section winding is 61.64W, of which eddy current loss is 18.14W and DC loss is 43.50W. After the variable cross-section structural design, the eddy current loss of the winding decreased by 50.16%, while the DC loss increased by 20.88%. Therefore, the variable cross-section structure has a good suppressive effect on the AC loss of the winding.

[0062] Figure 6 , Figure 7 The figures show the optimal two-layer transposition circuit diagrams and current waveforms for both a constant cross-section winding and a variable cross-section winding. This winding is a three-layer winding; due to limitations in additive manufacturing, two layers were optimized through transposition. The inductance and voltage data of the winding can be extracted using a finite element model. Based on formula (4-7), the optimal transposition structure of the winding can be obtained. The current waveforms clearly show that the current difference in the variable cross-section two-layer transposition winding is smaller than that in the constant cross-section two-layer transposition winding.

[0063] Figure 8 This image shows a loss comparison between a variable cross-section two-layer transposed winding and a constant cross-section two-layer transposed winding. The winding was simulated and analyzed using a finite element model. Figure 7 , 8The windings shown are illustrated. It can be seen that in the variable cross-section winding, although DC losses increase slightly, eddy current losses and circulating losses are significantly reduced. The total AC losses of the three-layer winding before and after the cross-section change are 84.59W and 62.25W, respectively. After changing the cross-section, the eddy current loss of the three-layer winding decreased by 48.9%. The change in winding cross-section also reduced the circulating current loss; the circulating current loss of the constant cross-section winding was 13.51W, while that of the variable cross-section winding was 4.71W, a reduction of 65.13%. The results indicate that the variable cross-section winding not only suppresses eddy current losses but also effectively suppresses circulating current losses. This may be because the variable cross-section structure affects the conductor's potential, changing the conductor's resistance and reducing the potential difference between the strands.

[0064] Figure 9 This document presents a flowchart for conductor spacing optimization and a diagram for optimizing the spacing of variable cross-section transposed windings. Variable cross-section structures involve changing the height of the cross-section and altering the conductor spacing. (Example:...) Figure 3 As shown, after variable cross-section optimization, the conductor at the bottom of the slot has a thicker cross-section, resulting in a very low magnetic density and lower eddy current losses. By reducing the conductor cross-section height at the bottom of the slot, while maintaining the total winding height, the spacing between the selected conductors is increased. This increases the induced electromotive force in the conductors of branches with lower currents, further reducing the circulating current losses caused by the inter-strand potential difference. For Figure 7 The optimization process for the three-layer variable cross-section two-layer transposed winding shown is as follows: First, based on... Figure 7 Based on the current waveforms shown, the branches requiring potential increases are identified. The current difference between branches AN1 and AN3 and AN2 is significant; therefore, the potential of branches AN1 and AN3 should be increased. Next, the conductor positions within these branches where potential can be increased are determined. Increasing the spacing will increase the potential of all conductors after the selected spacing relative to the conductors before that spacing, but only the potential difference within the turn containing the selected spacing changes; the potential difference within other turns remains unchanged. The circuit diagram on the right indicates the selectable spacing positions for the three-layer variable cross-section transposed winding. Increasing the spacing at positions 1 and 3 increases the potential of branch 3, only decreasing the current difference between branches 1 and 3; increasing the spacing at positions 5 and 6 increases the potential of branch 1, only decreasing the current difference between branches 1 and 2; increasing the spacing at positions 2 and 4 simultaneously increases the potential of branches 1 and 3, decreasing the current difference between branches 1 and 2 and between branches 2 and 3. The reduction ratio of the height of the bottom conductors AN1-3 and AP1-3 and the maximum possible spacing are determined as 2.6mm for AN slot and 1.4mm for AP slot, serving as constraints. Finally, by combining formulas (4-5) and (8) in MATLAB, the optimal value of the increased conductor spacing when the circulating loss is minimized is obtained.

[0065] Figure 10This is a schematic diagram of the optimized winding cross-section; after optimization, the spacing at position 3 becomes 2.6mm, and the spacing at position 4 becomes 1.4mm. The remaining spacings are all 0.2mm.

[0066] Figure 11 This is a current waveform diagram of the variable cross-section transposed winding after spacing optimization. Figure 7 In comparison, the current difference after spacing optimization was significantly suppressed. The total AC loss of the variable cross-section winding was 59.01W. By optimizing the spacing between adjacent conductors, it was reduced by 5.20%, DC loss increased by 5.04%, eddy current loss decreased by 12.61%, and circulating current loss decreased by 58.06%. Changing the conductor spacing reduces the potential difference between strands, thus reducing circulating current. While reducing the height of the bottom conductor in the slot can reduce eddy current loss, it also increases DC loss. In this example, the total loss is still reduced, but if the height of the bottom conductor is further reduced, DC loss may increase beyond the reduction in circulating current and eddy current, leading to a higher total loss. When applying this method to other situations, specific constraints need to be determined based on the actual motor operating conditions.

[0067] This invention proposes a design method for a variable cross-section end transposed winding, which optimizes the conductor cross-section height and spacing as well as the transposed structure. The optimized method, as verified by simulation, significantly reduces the AC loss of the winding and improves the problems of high motor loss and severe heat generation under high-speed conditions. The variable cross-section end transposed winding of the electrically excited doubly salient pole motor of this invention is integrally formed using additive manufacturing technology, which has a high degree of design freedom.

[0068] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on its differences from other embodiments. In particular, the device embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments. The above descriptions are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An optimized method for additive manufacturing of variable cross-section end-transposed windings, characterized in that, include: S1. Obtain the initial information of the end transposed winding to be optimized, and establish an analytical model of the winding AC loss based on the initial information. S2. Based on the analytical model of the winding AC loss and the distribution of magnetic flux density in the slot, a first optimization model is established. The output of the optimization model includes the height of the optimized conductor cross section. S3. Establish a second optimization model. The output of the second optimization model includes the optimized spacing value between the winding conductors. S4. The output results of the first optimization model and the second optimization model are transmitted to the additive manufacturing equipment, which is used to manufacture the end transposed winding of the electrically excited doubly salient pole motor. In S1, the analytical model of winding AC loss includes: P Cu =P Cu_dc +P eddy +P cir , where P Cu P represents the AC loss of the winding. Cu_dc P represents the DC loss of the winding. eddy P represents the eddy current loss of the winding. cir This indicates the circulating current loss of the winding; in, The initial information includes the number of winding turns N and the effective value of the winding current I. rms The resistance R of the winding, the axial length l of the winding, the resistivity ρ of the conductor, the length a1 and width h1 of the rectangular winding, and the components B of the magnetic flux density along the x and y axes through each rectangular winding cross section. x and B y ; In S2, the first optimization model includes: Where z is the sum of eddy current losses and DC losses in the winding, and a and h i B represents the length and width of the rectangular conductor, respectively. ix Let d be the magnetic flux density along the x-axis on the cross-section of each rectangular conductor, and h be the distance between adjacent conductors. τ h is the total height of the winding. min The minimum allowable thickness of the conductor due to the limitations of additive manufacturing technology, i is a positive integer used to represent the number of the rectangular conductor, n is the total number of conductors in the slot, and I is the effective value of the winding current; In S3, the second optimization model includes: By changing the cross-sectional height of the bottom conductor and altering the spacing between conductors while keeping the total winding height constant, the induced electromotive force in the conductor of the branch with the smaller current increases, thereby reducing the circulating current loss caused by the inter-strand potential difference. The conductor voltages before and after changing the spacing satisfy the following conditions: Among them, U i ,U′ i These represent the voltages of the conductors before and after changing the spacing, where U0 is the voltage of the conductor at the bottom of the slot, and h... i The distance between the conductor and the geometric center point of the bottom conductor of the trench is d, where d is the increased spacing. The second optimization model is loaded using a MATLAB program to obtain the minimum circulation loss and the corresponding spacing value.

2. The optimized method for additive manufacturing of variable cross-section end-transposed windings according to claim 1, characterized in that, Methods for obtaining circulating current loss include: Where s is the differential operator, L is the matrix of the three layers of self-inductance and mutual inductance of the winding, E1 is the unit row vector, and E2 is the unit column vector. P cir =i 1cir 2 R1+i 2cir 2 R2+i 3cir 2 R3, where u1~u3 and i1~i3 are the induced voltage and current of the three parallel-wound wires, respectively, and L j,j For the self-induction of the j-th layer, L i,j For the mutual inductance between the i-th layer and the j-th layer, R j Let t be the resistance of the j-th layer, and t be time.

3. The optimized method for additive manufacturing of variable cross-section end-transposed windings according to claim 1, characterized in that, In the additive manufacturing process of the end-transformed winding, a two-layer transposition structure is adopted.

4. The optimized method for additive manufacturing of variable cross-section end-transposed windings according to claim 3, characterized in that, The end transposition winding includes: a 6-turn series coil, each turn of the coil having 3 strands of parallel wire distributed at different positions in the slot; The conductor has a rectangular cross-section, and the cross-sectional height and spacing between conductors vary at different positions within the slot.

5. The optimized method for additive manufacturing of variable cross-section end-transformed windings according to claim 1, characterized in that, The end transposed windings of the electrically excited doubly salient pole motor are manufactured in one piece using additive manufacturing equipment.

6. The optimized method for additive manufacturing of variable cross-section end-transposed windings according to claim 1, characterized in that, The conductor material in the winding is copper.

7. The optimized method for additive manufacturing of variable cross-section end-transformed windings according to any one of claims 1-6, characterized in that, The optimized variable cross-section end transposition winding for additive manufacturing, as described by the optimization method, includes: a 6-turn series coil, each turn of which has 3 strands of parallel-wound wire distributed at different positions in the slot, the cross-section of which is rectangular, the variable cross-section being the difference in the cross-sectional height of the conductors at different positions in the slot and the difference in the spacing between the conductors, and all windings are two-layer transposition structures.

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