Method and device for determining equivalent thermal conductivity of secondary transposed Litz line

Abstract

The present invention provides a method and device for determining the equivalent thermal conductivity of a secondary transposed Litz line. The method comprises: constructing a first parallel thermal resistance model along the length direction of the secondary transposed Litz line, a second series thermal resistance model and a second parallel thermal resistance model along the width direction, and a third series thermal resistance model and a third parallel thermal resistance model along the thickness direction; determining a first equivalent thermal conductivity of the secondary transposed Litz line along the length direction based on the first parallel thermal resistance model; determining a second equivalent thermal conductivity of the secondary transposed Litz line along the width direction based on the second series thermal resistance model and the second parallel thermal resistance model; and determining a third equivalent thermal conductivity of the secondary transposed Litz line along the width direction based on the third series thermal resistance model and the third parallel thermal resistance model. The present invention takes into account the combined effects of both series thermal diffusion and parallel thermal diffusion on the equivalent thermal conductivity, thereby improving the accuracy of the determined equivalent thermal conductivity.

Description

Technical Field

[0001] The present invention relates to the technical field of temperature field analysis, and in particular to a method and device for determining the equivalent thermal conductivity of a secondary transposed Litz line. Background Art

[0002] For certain specialized motors (such as high-speed motors and those with high magnetic loads) or power transformers, winding with Litz transposed conductors can significantly reduce circulating and eddy current losses, improving operational reliability and lifespan. Thermal analysis of these specialized motors often requires predicting their heat load capacity and maximum temperature rise. This requires accurate input of material thermal parameters, making the evaluation of Litz transposed conductor thermal parameters particularly important.

[0003] Many methods have been used to estimate the equivalent thermal conductivity of Litz-transposed conductors, including experimental measurements, simulation analysis, and equivalent analysis methods. Equivalent analysis methods typically provide a time- and resource-efficient way to evaluate the thermal conductivity of Litz conductors. However, their accuracy depends on the simplified model used. Existing physical models are mostly simplified to simple parallel or series models. However, heat flow within Litz-transposed conductors involves both series and parallel thermal diffusion between different materials. Therefore, the equivalent parameters derived using simple parallel or series models cannot reflect the actual structure, affecting the accuracy of simulation analysis results.

[0004] Therefore, it is urgent to provide a method and device for determining the equivalent thermal conductivity of a secondary transposed Litz wire, taking into account the joint influence of series and parallel conditions on the thermal conductivity, and improving the accuracy of thermal simulation of the secondary transposed Litz wire. Summary of the Invention

[0005] In view of this, it is necessary to provide a method and device for determining the equivalent thermal conductivity of a secondary transposed Litz wire to solve the technical problem in the prior art that only a single series or parallel model is considered to derive the equivalent thermal conductivity, resulting in inaccurate equivalence of the thermal conductivity of the secondary transposed Litz wire.

[0006] On the one hand, in order to solve the above technical problems, the present invention provides a method for determining the equivalent thermal conductivity of a secondary transposed Litz line, comprising:

[0007] Constructing a first parallel thermal resistance model along the length direction, a second series thermal resistance model and a second parallel thermal resistance model along the width direction, and a third series thermal resistance model and a third parallel thermal resistance model along the thickness direction of the secondary transposed Litz line;

[0008] Determine a first equivalent thermal conductivity of the secondary transposed Litz line along the length direction based on the first parallel thermal resistance model;

[0009] Determining a second series thermal conductivity and a second parallel thermal conductivity of the secondary transposed Litz line along the width direction based on the second series thermal resistance model and the second parallel thermal resistance model, respectively, and taking a weighted sum of the second series thermal conductivity and the second parallel thermal conductivity as a second equivalent thermal conductivity of the secondary transposed Litz line along the width direction;

[0010] A third series thermal conductivity and a third parallel thermal conductivity of the secondary transposed Litz line along the thickness direction are respectively determined based on the third series thermal resistance model and the third parallel thermal resistance model, and a weighted sum of the third series thermal conductivity and the third parallel thermal conductivity is used as the third equivalent thermal conductivity of the secondary transposed Litz line along the thickness direction.

[0011] In a possible implementation, the preparation process of the secondary transposed Litz wire is as follows:

[0012] Treating the round copper wire with an insulating paint film to obtain an enameled round copper wire;

[0013] Transposing a plurality of enameled round copper wires, performing vacuum pressure impregnation on the transposed plurality of enameled round copper wires to obtain a single-transposed Litz wire, and wrapping a first polyimide film around the single-transposed Litz wire;

[0014] The primary transposed Litz wire wrapped with the first polyimide film is subjected to secondary transposition to obtain a secondary transposed Litz wire, a second polyimide film is wrapped around the secondary transposed Litz wire, and the secondary transposed Litz wire wrapped with the second polyimide film is subjected to vacuum pressure impregnation.

[0015] In one possible implementation, the second series thermal resistance model includes the enameled copper round wire series thermal resistance model, the first transposition series thermal resistance model of the first transposition Litz wire, and the second transposition series thermal resistance model of the transposition Litz wire; determining the second series thermal conductivity of the second transposition Litz wire along the width direction based on the second series thermal resistance model includes:

[0016] Determining the enameled series equivalent thermal resistance of the enameled round copper wire based on the enameled series thermal resistance model, and determining the enameled round copper wire equivalent series thermal conductivity based on the enameled series equivalent thermal resistance and the size parameters of the enameled round copper wire;

[0017] Determine the first transposition series equivalent thermal resistance of the first transposition Litz wire based on the first transposition series thermal resistance model and the enameled series equivalent thermal resistance, and determine the first transposition equivalent series thermal conductivity based on the first transposition series equivalent thermal resistance and the size parameters of the first transposition Litz wire;

[0018] The secondary transposition series equivalent thermal resistance of the secondary transposition Litz line is determined based on the secondary transposition series thermal resistance model and the primary transposition series equivalent thermal resistance, and the second series thermal conductivity is determined based on the secondary transposition series equivalent thermal resistance and the size parameters of the secondary transposition Litz line.

[0019] In a possible implementation, the second series thermal conductivity is:

[0020]

[0021] Where, is the second series thermal conductivity; is the equivalent thermal resistance of the secondary transposition series connection; w is the width of a transposed Litz line; b is the thickness of the Litz line of a single transposition; t 3 is the double-sided thickness of the first polyimide film; t 4 is the bilateral thickness of the resin layer in the secondary transposition Litz line; t 5 is the thickness of the second polyimide film; dl It is the length of a single enameled round copper wire along the longitudinal direction.

[0022] In one possible implementation, the second parallel thermal resistance model includes the enameled copper round wire parallel thermal resistance model, the first transposition parallel thermal resistance model of the first transposition Litz wire, and the second transposition parallel thermal resistance model of the transposition Litz wire; determining the second parallel thermal conductivity of the second transposition Litz wire along the width direction based on the second parallel thermal resistance model includes:

[0023] Determining the enameled parallel equivalent thermal resistance of the enameled round copper wire based on the enameled round copper wire parallel thermal resistance model, and determining the enameled round copper wire equivalent parallel thermal conductivity based on the parallel equivalent thermal resistance and the dimensional parameters of the enameled round copper wire;

[0024] Determining the first-transposition parallel equivalent thermal resistance of the first-transposition Litz wire based on the first-transposition parallel thermal resistance model and the equivalent parallel thermal conductivity of the enameled copper round wire, and determining the first-transposition equivalent parallel thermal conductivity based on the first-transposition parallel equivalent thermal resistance and the size parameters of the first-transposition Litz wire;

[0025] The secondary transposition parallel equivalent thermal resistance of the secondary transposition Litz line is determined based on the secondary transposition parallel thermal resistance model and the primary transposition series equivalent thermal resistance, and the second parallel thermal conductivity is determined based on the secondary transposition parallel equivalent thermal resistance and the size parameters of the secondary transposition Litz line.

[0026] In a possible implementation, the second parallel thermal conductivity is:

[0027]

[0028] Where, is the second parallel thermal conductivity; is the secondary transposition parallel equivalent thermal resistance; w is the width of a transposed Litz line; b is the thickness of the Litz line of a single transposition; t 3 is the double-sided thickness of the first polyimide film; t 4 is the bilateral thickness of the resin layer in the secondary transposition Litz line; t 5 is the thickness of the second polyimide film; dl It is the length of a single enameled round copper wire along the longitudinal direction.

[0029] In a possible implementation, the method further includes:

[0030] Obtaining the diameter of the round copper wire and the thickness of the insulating paint film;

[0031] determining a volume fraction of the copper round wire based on the diameter and the paint film thickness, and determining a first weight of the second series thermal conductivity and a second weight of the third series thermal conductivity based on the volume fraction;

[0032] The second equivalent thermal conductivity and the third equivalent thermal conductivity are determined based on the first weight, the second weight, the second series thermal conductivity, the second parallel thermal conductivity, the third series thermal conductivity, and the third parallel thermal conductivity.

[0033] In a possible implementation, the second equivalent thermal conductivity is:

[0034]

[0035]

[0036] Where, is the second equivalent thermal conductivity; is the first weight; V m is the volume fraction of copper round wire.

[0037] In a possible implementation, the third equivalent thermal conductivity is:

[0038]

[0039]

[0040] Where, is the second equivalent thermal conductivity; is the second weight; V m is the volume fraction of copper round wire.

[0041] On the other hand, the present invention also provides a device for determining the equivalent thermal conductivity of a secondary transposed Litz line, comprising:

[0042] A series-parallel thermal resistance model construction unit is used to construct a first parallel thermal resistance model along the length direction, a second series thermal resistance model and a second parallel thermal resistance model along the width direction, and a third series thermal resistance model and a third parallel thermal resistance model along the thickness direction of the secondary transposed Litz line;

[0043] a first equivalent thermal conductivity determining unit, configured to determine a first equivalent thermal conductivity of the secondary transposed Litz line along a length direction based on the first parallel thermal resistance model;

[0044] a second equivalent thermal conductivity determining unit, configured to determine a second series thermal conductivity and a second parallel thermal conductivity of the secondary transposed Litz line along the width direction based on the second series thermal resistance model and the second parallel thermal resistance model, respectively, and take a weighted sum of the second series thermal conductivity and the second parallel thermal conductivity as the second equivalent thermal conductivity of the secondary transposed Litz line along the width direction;

[0045] a third equivalent thermal conductivity determining unit, configured to determine, based on the third series thermal resistance model and the third parallel thermal resistance model, respectively, a third series thermal conductivity and a third parallel thermal conductivity of the secondary transposed Litz line along the thickness direction, and take a weighted sum of the third series thermal conductivity and the third parallel thermal conductivity as the third equivalent thermal conductivity of the secondary transposed Litz line along the thickness direction.

[0046] The beneficial effects of the present invention are as follows: the method for determining the equivalent thermal conductivity of a secondary transposed Litz line provided by the present invention constructs a second series thermal resistance model, a second parallel thermal resistance model, a third series thermal resistance model, and a third parallel thermal resistance model in the width and thickness directions of the secondary transposed Litz line, respectively, takes into account both the series thermal diffusion and the parallel thermal diffusion between different materials in the heat flow within the secondary transposed Litz line, takes into account the joint influence of the series thermal diffusion and the parallel thermal diffusion on the equivalent thermal conductivity, and improves the accuracy of the determined equivalent thermal conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. 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 work.

[0048] Figure 1 A schematic flow chart of an embodiment of a method for determining the equivalent thermal conductivity of a secondary transposed Litz line provided by the present invention;

[0049] Figure 2 A schematic structural diagram of an embodiment of a secondary transposed Litz line provided by the present invention;

[0050] Figure 3 A schematic diagram of the three-dimensional structure of the secondary transposed Litz line provided by the present invention;

[0051] Figure 4 This is a schematic flow chart of an embodiment of determining the second series thermal conductivity coefficient in step S103 of the present invention;

[0052] Figure 5 (a) is a schematic structural diagram of an embodiment of the present invention providing an enameled round copper wire;

[0053] Figure 5 (b) A schematic diagram of an embodiment of a model for dividing the thermal resistance of enameled round copper wires in series provided by the present invention;

[0054] Figure 5 (c) A schematic diagram of an embodiment of the present invention providing a structural diagram of a series thermal resistance model of enameled copper round wires;

[0055] Figure 6 (a) is a schematic structural diagram of an embodiment of a single-transposition Litz line provided by the present invention;

[0056] Figure 6 (b) is a schematic structural diagram of an embodiment of the single-transposition Litz line series thermal resistance partitioning model provided by the present invention;

[0057] Figure 6 (c) is a schematic structural diagram of an embodiment of the single-transposition Litz line series thermal resistance model provided by the present invention;

[0058] Figure 7 A schematic structural diagram of an embodiment of the secondary transposed Litz line series thermal resistance partitioning model provided by the present invention;

[0059] Figure 8 A schematic structural diagram of an embodiment of the two-transposed Litz line series thermal resistance model provided by the present invention;

[0060] Figure 9 A schematic diagram of an embodiment of a flow chart for determining the second parallel thermal conductivity in step S103 provided by the present invention;

[0061] Figure 10 (a) is a schematic diagram of an embodiment of a parallel thermal resistance partitioning model for enameled round copper wires provided by the present invention;

[0062] Figure 10 (b) A schematic diagram of an embodiment of the present invention providing a parallel thermal resistance model of enameled round copper wires;

[0063] Figure 11 (a) is a schematic structural diagram of an embodiment of the single-transposition Litz line parallel thermal resistance partitioning model provided by the present invention;

[0064] Figure 11 (b) is a schematic structural diagram of an embodiment of the single-transposition Litz line parallel thermal resistance model provided by the present invention;

[0065] Figure 12 A schematic structural diagram of an embodiment of the quadratic transposed Litz line parallel thermal resistance partitioning model provided by the present invention;

[0066] Figure 13 A schematic structural diagram of an embodiment of the two-transposed Litz line parallel thermal resistance model provided by the present invention;

[0067] Figure 14 A schematic structural diagram of an embodiment of determining the weighted equivalent thermal conductivity provided by the present invention;

[0068] Figure 15 This is a schematic structural diagram of an embodiment of a device for determining the equivalent thermal conductivity of a secondary transposed Litz line provided by the present invention. DETAILED DESCRIPTION

[0069] The following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0070] It should be understood that the schematic drawings are not drawn to scale. The flowcharts used in the present invention illustrate operations implemented according to some embodiments of the present invention. It should be understood that the operations of the flowcharts can be implemented out of sequence, and steps that have no logical contextual relationship can be reversed in order or implemented simultaneously. In addition, those skilled in the art, guided by the content of the present invention, can add one or more other operations to the flowcharts or remove one or more operations from the flowcharts. Some of the block diagrams shown in the accompanying drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented in the form of software, or in one or more hardware modules or integrated circuits, or in different networks and / or processor systems and / or microcontroller systems.

[0071] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present invention. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute a separate or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0072] The present invention provides a method and device for determining the equivalent thermal conductivity of a secondary transposed Litz line, which are described below.

[0073] Figure 1 A flow chart of an embodiment of a method for determining the equivalent thermal conductivity of a secondary transposed Litz line provided by the present invention is shown in FIG. Figure 1 As shown in Figure 2, the method for determining the equivalent thermal conductivity of the secondary transposed Litz line includes:

[0074] S101, constructing a first parallel thermal resistance model along the length direction, a second series thermal resistance model and a second parallel thermal resistance model along the width direction, and a third series thermal resistance model and a third parallel thermal resistance model along the thickness direction of the secondary transposed Litz line;

[0075] S102, determining a first equivalent thermal conductivity of the secondary transposed Litz line along the length direction based on the first parallel thermal resistance model;

[0076] S103, determining a second series thermal conductivity and a second parallel thermal conductivity of the secondary transposed Litz line along the width direction based on the second series thermal resistance model and the second parallel thermal resistance model, respectively, and taking a weighted sum of the second series thermal conductivity and the second parallel thermal conductivity as a second equivalent thermal conductivity of the secondary transposed Litz line along the width direction;

[0077] S104. Determine a third series thermal conductivity and a third parallel thermal conductivity of the secondary transposed Litz line along the thickness direction based on the third series thermal resistance model and the third parallel thermal resistance model, respectively, and use a weighted sum of the third series thermal conductivity and the third parallel thermal conductivity as a third equivalent thermal conductivity of the secondary transposed Litz line along the thickness direction.

[0078] In a specific embodiment of the present invention, Figure 2 As shown in Figure 2, the preparation process of the secondary transposed Litz line is as follows:

[0079] First, a copper round wire with a diameter of d (radius of r) is treated with an insulating paint film (with a double-sided thickness of t1mm) to obtain an enameled copper round wire with a diameter of d1; secondly, n1 enameled copper round wires with a diameter of d1 are transposed and vacuum pressure impregnated to obtain a wmm×bmm primary transposed Litz wire, and after vacuum pressure impregnation, the enameled copper round wire is attached with a resin layer with a double-sided thickness of t2mm; then, a first polyimide film with a double-sided thickness of t3mm is wrapped around the wmm×bmm primary transposed Litz wire; thirdly, n2 wmm×bmm primary transposed Litz wires are subjected to a secondary transposition to obtain a wmm×Bmm secondary transposed Litz wire, and the secondary transposed Litz includes a resin layer with a double-sided thickness of t4mm; then, a second polyimide film with a double-sided thickness of t5mm is wrapped around the secondary transposed Litz wire, and finally, the entire secondary transposed Litz wire is vacuum pressure impregnated.

[0080] Among them, the length direction, width direction and thickness direction of the secondary transposed Litz line are as follows Figure 3 shown.

[0081] It should be noted that: in order to simplify the analysis, the enameled copper round wire is extruded into a square in the process of preparing the first transposition Litz wire, that is, the enameled copper round wire is approximately simplified into a square, and the length of the square is determined according to the principle of equal area. For example: when the radius of the copper round wire is r, the length of the simplified square is .

[0082] Since there is no heat diffusion between series and parallel connections along the length direction of the secondary transposed Litz line, its equivalent thermal conductivity along the length direction is derived according to the parallel model, which will not be elaborated here.

[0083] Compared with the prior art, the method for determining the equivalent thermal conductivity of a secondary transposed Litz line provided in an embodiment of the present invention constructs a second series thermal resistance model, a second parallel thermal resistance model, a third series thermal resistance model, and a third parallel thermal resistance model in the width and thickness directions of the secondary transposed Litz line, respectively. This method considers both series thermal diffusion and parallel thermal diffusion between different materials in the heat flow within the secondary transposed Litz line, and takes into account the combined influence of both series and parallel thermal diffusion on the equivalent thermal conductivity, thereby improving the accuracy of the determined equivalent thermal conductivity.

[0084] The preparation process of the secondary transposed Litz wire can be seen as follows: copper round wire - primary transposed Litz wire - secondary transposed Litz wire. Therefore, in some embodiments of the present invention, the process of determining the equivalent thermal conductivity of the secondary transposed Litz wire is also carried out according to this process. Specifically, the second series thermal resistance model includes the series thermal resistance model of the enameled copper round wire, the primary transposed series thermal resistance model of the primary transposed Litz wire, and the secondary transposed series thermal resistance model of the transposed Litz wire; then, Figure 4 As shown, determining the second series thermal conductivity of the secondary transposed Litz line along the width direction based on the second series thermal resistance model in step S103 includes:

[0085] S401, determining the enameled series equivalent thermal resistance of the enameled round copper wire based on the enameled round copper wire series thermal resistance model, and determining the enameled round copper wire equivalent series thermal conductivity based on the enameled series equivalent thermal resistance and the size parameters of the enameled round copper wire;

[0086] S402, determining the first-transposition series equivalent thermal resistance of the first-transposition Litz wire based on the first-transposition series thermal resistance model and the enameled series equivalent thermal resistance, and determining the first-transposition equivalent series thermal conductivity based on the first-transposition series equivalent thermal resistance and the size parameters of the first-transposition Litz wire;

[0087] S403: Determine the secondary transposition series equivalent thermal resistance of the secondary transposition Litz line based on the secondary transposition series thermal resistance model and the primary transposition series equivalent thermal resistance, and determine the second series thermal conductivity based on the secondary transposition series equivalent thermal resistance and the size parameters of the secondary transposition Litz line.

[0088] In a specific embodiment of the present invention, Figure 5 As shown in (a), the enameled copper round wire series thermal resistance partition model is constructed based on the copper round wire, insulating paint film and resin layer. Since this structure is symmetrical, half of it is taken for analysis, and its thermal resistance network is as follows Figure 5 As shown in (b), this structure is divided into three regions from left to right along the series direction. The first region includes the first thermal resistance R of the resin from top to bottom. 1i , the first thermal resistance of the insulating paint film R 1p , Copper round wire thermal resistance R1c , the first thermal resistance of the insulating paint film R 1p , resin first thermal resistance R 1i The second area includes the second thermal resistance R of the resin from top to bottom 2i , the second thermal resistance of the insulating paint film R 2p 、Resin second thermal resistance R 2i , the third region includes the third resin thermal resistance R 3i .

[0089] Based on the thermal resistance analysis of the above structure, we can get the following Figure 5 (c) Enameled copper wire series thermal resistance model. Figure 5 (c) The enameled copper wire series thermal resistance model can be used to obtain the enameled series equivalent thermal resistance for:

[0090]

[0091] Then the equivalent series thermal conductivity of enameled copper round wire is for:

[0092]

[0093] Where r is the radius of the round copper wire; t1 is the double-sided thickness of the insulating paint film; t2 is the double-sided thickness of the resin layer covering the enameled round copper wire; dl It is the length of a single enameled round copper wire along the longitudinal direction.

[0094] In a specific embodiment of the present invention, a single-transposition Litz wire is prepared from 23 enameled round copper wires. The structure of the single-transposition Litz wire is as follows: Figure 6 As shown in (a), similarly, due to its symmetry, the general structure is analyzed, and its thermal resistance division model is as follows Figure 6 As shown in (b), this structure is divided into two regions from left to right along the series direction. The first region includes the fourth thermal resistor R 4n , enameled round copper wire thermal resistance R 4c , polyimide fourth thermal resistance R 4n , the second region includes a fifth thermal resistance R of polyimide 5n .

[0095] Based on the thermal resistance analysis of the above structure, we can get the following Figure 6 (c) The single-transposition Litz line series thermal resistance model is based on Figure 6 (c) The single-transposition series thermal resistance model can be used to obtain the single-transposition series equivalent thermal resistance R q2 for:

[0096]

[0097] Then the equivalent series thermal conductivity of one-time transposition is λ q2 for:

[0098]

[0099] Wherein, w is the width of the single-transposition Litz line; t3 is the double-sided thickness of the polyimide film coated with the single-transposition Litz line.

[0100] In a specific embodiment of the present invention, Figure 7 This is the thermal resistance division model of the secondary transposition Litz wire, which consists of 9 primary transposition Litz wires and a coated resin layer. The thermal resistance network is divided into four areas from left to right along the series direction. The first area is the seventh thermal resistance R of polyimide. 7n , the second area includes the seventh resin thermal resistance R in parallel from top to bottom 7p The equivalent thermal resistance R of the seventh series transposition 7c 、Four sixth-order transposition series equivalent thermal resistance R 6c and polyimide eighth thermal resistance R 8n , the third region includes the eighth resin thermal resistance R in parallel from top to bottom 8p And the eighth first transposition series equivalent thermal resistance R 8c 、Four sixth-order transposition series equivalent thermal resistance R 6c and polyimide eighth thermal resistance R 8n , the fourth area is the seventh thermal resistance R of polyimide 7n .

[0101] Based on the above thermal resistance structure, we can get Figure 8 The secondary transposed Litz line series thermal resistance model is based on Figure 8 The secondary transposition series thermal resistance model can be obtained by R eq2 for:

[0102]

[0103] Then the second series thermal conductivity is:

[0104]

[0105] Where, is the second series thermal conductivity.

[0106] Similarly, the second parallel thermal resistance model includes the parallel thermal resistance model of the enameled copper round wire, the first-transposition parallel thermal resistance model of the first-transposition Litz wire, and the second-transposition parallel thermal resistance model of the transposition Litz wire; then Figure 9As shown, determining the second parallel thermal conductivity of the secondary transposed Litz line along the width direction based on the second parallel thermal resistance model in step S103 includes:

[0107] S901. Determine the enameled parallel equivalent thermal resistance of the enameled round copper wire based on the enameled parallel thermal resistance model, and determine the equivalent parallel thermal conductivity of the enameled round copper wire based on the enameled parallel equivalent thermal resistance and the dimensional parameters of the enameled round copper wire.

[0108] S902. Determine the first-transposition parallel equivalent thermal resistance of the first-transposition Litz wire based on the first-transposition parallel thermal resistance model and the equivalent parallel thermal conductivity of the enameled copper round wire, and determine the first-transposition equivalent parallel thermal conductivity based on the first-transposition parallel equivalent thermal resistance and the size parameters of the first-transposition Litz wire;

[0109] S903. Determine the secondary transposition parallel equivalent thermal resistance of the secondary transposition Litz line based on the secondary transposition parallel thermal resistance model and the primary transposition series equivalent thermal resistance, and determine the second parallel thermal conductivity based on the secondary transposition parallel equivalent thermal resistance and the size parameters of the secondary transposition Litz line.

[0110] In a specific embodiment of the present invention, the parallel thermal resistance division model of the enameled round copper wire is as follows: Figure 10 As shown in (a), it is divided into five areas from top to bottom along the parallel direction. The first area is the third parallel resin thermal resistance , the second region includes the second parallel film thermal resistance in series and the second parallel resin thermal resistance , the third area includes the first parallel copper round wire thermal resistance in series , first parallel paint film thermal resistance and the first parallel resin thermal resistance , the fourth region includes the second parallel film thermal resistance in series and the second parallel resin thermal resistance , the fifth area is the third parallel resin thermal resistance .

[0111] Based on the above thermal resistance analysis, we can get Figure 10 (b) The parallel thermal resistance model of enameled copper round wire. Based on this parallel thermal resistance model of enameled copper round wire, the equivalent parallel thermal conductivity of enameled copper round wire can be obtained. R e2 0 for:

[0112]

[0113] Then the equivalent series thermal conductivity of enameled copper round wire is λ e2 0 for:

[0114]

[0115] In a specific embodiment of the present invention, a single-transposition Litz wire is prepared from 23 enameled round copper wires, and its thermal resistance network is as follows: Figure 11 As shown in (a), this structure is divided into three regions from top to bottom along the parallel direction. The first region is the fourth thermal resistor of the polyimide parallel , the second area includes the parallel enameled copper round wire thermal resistance connected in series from left to right And the fourth thermal resistance in parallel with polyimide , the third area is the fourth thermal resistance of polyimide in parallel .

[0116] Based on the thermal resistance analysis of the above structure, we can get the following Figure 11 (b) The single-transposition Litz line series thermal resistance model is based on Figure 11 (b) The single-transposition series thermal resistance model can be used to obtain the single-transposition parallel equivalent thermal resistance R q2 0 for:

[0117]

[0118] Then the equivalent thermal conductivity of the parallel connection is λ q2 0 for:

[0119]

[0120] In a specific embodiment of the present invention, Figure 12 It is a parallel thermal resistance network of secondary transposed Litz wires, which consists of 9 primary transposed Litz wires. The parallel thermal resistance network is divided into seven areas from top to bottom along the parallel direction. The first area is the eighth thermal resistance of the parallel polyimide. , the second region includes the seventh thermal resistor of the parallel polyimide in series from left to right , parallel seventh resin thermal resistance , parallel sixth first transposition series equivalent thermal resistance , parallel eighth resin thermal resistance and parallel polyimide seventh thermal resistance , the third region, the fourth region, the fifth region and the sixth region all include parallel polyimide seventh thermal resistance , two parallel sixth-order transposition series equivalent thermal resistance And parallel polyimide seventh thermal resistance , the seventh area is the eighth thermal resistance of parallel polyimide .

[0121] Based on the above thermal resistance structure, we can get Figure 13 The single-position Litz line parallel thermal resistance model is based on Figure 13 The secondary transposition parallel thermal resistance model can be obtained by R eq2 for:

[0122]

[0123] Then the second parallel thermal conductivity is:

[0124]

[0125] in, is the second parallel thermal conductivity.

[0126] It should be understood that the derivation process of the third series thermal conductivity and the third parallel thermal conductivity is based on the same principle as the derivation process of the second series thermal conductivity and the second parallel thermal conductivity, and will not be elaborated here.

[0127] Since the second equivalent thermal conductivity in the embodiment of the present invention is the weighted sum of the second series thermal conductivity and the second parallel thermal conductivity, and the third equivalent thermal conductivity is the weighted sum of the third series thermal conductivity and the third parallel thermal conductivity, that is, the weight distribution is crucial to the accuracy of the equivalent thermal conductivity. Therefore, in some embodiments of the present invention, such as Figure 14 As shown, the method for determining the equivalent thermal conductivity of the secondary transposed Litz line also includes:

[0128] S1401. Obtain the diameter of the round copper wire and the thickness of the insulating paint film;

[0129] S1402: Determine a volume fraction of the copper round wire based on the diameter and the paint film thickness, and determine a first weight of the second series thermal conductivity and a second weight of the third series thermal conductivity based on the volume fraction;

[0130] S1403 : Determine a second equivalent thermal conductivity and a third equivalent thermal conductivity based on the first weight, the second weight, the second series thermal conductivity, the second parallel thermal conductivity, the third series thermal conductivity, and the third parallel thermal conductivity.

[0131] Specifically, the second equivalent thermal conductivity is:

[0132]

[0133]

[0134] Where, is the second equivalent thermal conductivity; is the first weight; V mis the volume fraction of copper round wire.

[0135] The third equivalent thermal conductivity is:

[0136]

[0137]

[0138] Where, is the second equivalent thermal conductivity; is the second weight.

[0139] The embodiment of the present invention can further improve the accuracy of the determined equivalent thermal conductivity by assigning different series-parallel weights along the width and thickness directions of the secondary transposed Litz line.

[0140] Specifically, experimental verification shows that the relative error between the equivalent thermal conductivity determined by the traditional method and the test value is 6%, while the relative error between the equivalent thermal conductivity determined by the method proposed in the embodiment of the present invention and the test value is within 3.12%, and the accuracy is improved by 1.9 times.

[0141] In order to better implement the method for determining the equivalent thermal conductivity of a secondary transposed Litz line in an embodiment of the present invention, based on the method for determining the equivalent thermal conductivity of a secondary transposed Litz line, an embodiment of the present invention further provides a device for determining the equivalent thermal conductivity of a secondary transposed Litz line, such as Figure 5 As shown, the equivalent thermal conductivity determination device 1500 of the secondary transposed Litz line includes:

[0142] A series-parallel thermal resistance model construction unit 1501 is used to construct a first parallel thermal resistance model along the length direction, a second series thermal resistance model and a second parallel thermal resistance model along the width direction, and a third series thermal resistance model and a third parallel thermal resistance model along the thickness direction of the secondary transposed Litz line;

[0143] A first equivalent thermal conductivity determining unit 1502 is configured to determine a first equivalent thermal conductivity of a quadratic transposed Litz line along its length based on a first parallel thermal resistance model;

[0144] A second equivalent thermal conductivity determining unit 1503 is configured to determine a second series thermal conductivity and a second parallel thermal conductivity of the secondary transposed Litz line along the width direction based on the second series thermal resistance model and the second parallel thermal resistance model, respectively, and take a weighted sum of the second series thermal conductivity and the second parallel thermal conductivity as the second equivalent thermal conductivity of the secondary transposed Litz line along the width direction;

[0145] The third equivalent thermal conductivity determining unit 1504 is configured to determine a third series thermal conductivity and a third parallel thermal conductivity of the second-transposed Litz line along the thickness direction based on the third series thermal resistance model and the third parallel thermal resistance model, respectively, and use the weighted sum of the third series thermal conductivity and the third parallel thermal conductivity as the third equivalent thermal conductivity of the second-transposed Litz line along the thickness direction.

[0146] The device 1500 for determining the equivalent thermal conductivity of a secondary transposed Litz wire provided in the above embodiment can implement the technical solution described in the embodiment of the method for determining the equivalent thermal conductivity of a secondary transposed Litz wire. The specific implementation principles of each of the above modules or units can be found in the corresponding content of the embodiment of the method for determining the equivalent thermal conductivity of a secondary transposed Litz wire, and will not be repeated here.

[0147] Those skilled in the art will appreciate that all or part of the process flow of the above-described method embodiment can be implemented by instructing related hardware (such as a processor, controller, etc.) through a computer program, and the computer program can be stored in a computer-readable storage medium. The computer-readable storage medium may be a magnetic disk, an optical disk, a read-only memory, or a random access memory.

[0148] The above is a detailed introduction to the method and device for determining the equivalent thermal conductivity of a secondary transposed Litz wire provided by the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only intended to help understand the method and core concept of the present invention. At the same time, for those skilled in the art, according to the concept of the present invention, there may be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for determining the equivalent thermal conductivity of a secondary transposed Litz line, characterized in that: include: Constructing a first parallel thermal resistance model along the length direction, a second series thermal resistance model and a second parallel thermal resistance model along the width direction, and a third series thermal resistance model and a third parallel thermal resistance model along the thickness direction of the secondary transposed Litz line; Determine a first equivalent thermal conductivity of the secondary transposed Litz line along the length direction based on the first parallel thermal resistance model; Determining a second series thermal conductivity and a second parallel thermal conductivity of the secondary transposed Litz line along the width direction based on the second series thermal resistance model and the second parallel thermal resistance model, respectively, and taking a weighted sum of the second series thermal conductivity and the second parallel thermal conductivity as a second equivalent thermal conductivity of the secondary transposed Litz line along the width direction; determining a third series thermal conductivity and a third parallel thermal conductivity of the secondary transposed Litz line along the thickness direction based on the third series thermal resistance model and the third parallel thermal resistance model, respectively, and taking a weighted sum of the third series thermal conductivity and the third parallel thermal conductivity as a third equivalent thermal conductivity of the secondary transposed Litz line along the thickness direction; The second series thermal conductivity is: The second parallel thermal conductivity is: The second equivalent thermal conductivity is: Where, is the second series thermal conductivity; is the equivalent thermal resistance of the secondary transposition series connection; w is the width of a transposed Litz line; b is the thickness of the Litz line of a single transposition; t 3 is the double-sided thickness of the first polyimide film; t 4 is the bilateral thickness of the resin layer in the secondary transposition Litz line; t 5 is the double-sided thickness of the second polyimide film; dl It is the length of a single enameled round copper wire along the length direction; is the second parallel thermal conductivity; is the secondary transposition parallel equivalent thermal resistance; is the second equivalent thermal conductivity; is the first weight; V m is the volume fraction of copper round wire.

2. The method for determining the equivalent thermal conductivity of a secondary transposed Litz line according to claim 1, wherein: The preparation process of the secondary transposed Litz wire is as follows: Treating the round copper wire with an insulating paint film to obtain an enameled round copper wire; Transposing a plurality of enameled round copper wires, performing vacuum pressure impregnation on the transposed plurality of enameled round copper wires to obtain a single-transposed Litz wire, and wrapping a first polyimide film around the single-transposed Litz wire; The primary transposed Litz wire wrapped with the first polyimide film is subjected to secondary transposition to obtain a secondary transposed Litz wire, a second polyimide film is wrapped around the secondary transposed Litz wire, and the secondary transposed Litz wire wrapped with the second polyimide film is subjected to vacuum pressure impregnation.

3. The method for determining the equivalent thermal conductivity of a secondary transposed Litz line according to claim 2, wherein: The second series thermal resistance model includes the enameled copper round wire series thermal resistance model, the first transposition series thermal resistance model of the first transposition Litz wire, and the second transposition series thermal resistance model of the transposition Litz wire; determining the second series thermal conductivity of the second transposition Litz wire along the width direction based on the second series thermal resistance model includes: Determining the enameled series equivalent thermal resistance of the enameled round copper wire based on the enameled series thermal resistance model, and determining the enameled round copper wire equivalent series thermal conductivity based on the enameled series equivalent thermal resistance and the size parameters of the enameled round copper wire; Determining the first-transposition series equivalent thermal resistance of the first-transposition Litz wire based on the first-transposition series thermal resistance model and the equivalent series thermal conductivity of the enameled copper round wire, and determining the first-transposition equivalent series thermal conductivity based on the first-transposition series equivalent thermal resistance and the size parameters of the first-transposition Litz wire; The secondary transposition series equivalent thermal resistance of the secondary transposition Litz line is determined based on the secondary transposition series thermal resistance model and the primary transposition series equivalent thermal resistance, and the second series thermal conductivity is determined based on the secondary transposition series equivalent thermal resistance and the size parameters of the secondary transposition Litz line.

4. The method for determining the equivalent thermal conductivity of a secondary transposed Litz line according to claim 3, wherein: The second parallel thermal resistance model includes the enameled copper round wire parallel thermal resistance model, the first transposition parallel thermal resistance model of the first transposition Litz wire, and the second transposition parallel thermal resistance model of the transposition Litz wire; determining the second parallel thermal conductivity of the second transposition Litz wire along the width direction based on the second parallel thermal resistance model includes: Determining the enameled parallel equivalent thermal resistance of the enameled round copper wire based on the enameled parallel thermal resistance model, and determining the enameled round copper wire equivalent parallel thermal conductivity based on the enameled parallel equivalent thermal resistance and the dimensional parameters of the enameled round copper wire; Determining the first-transposition parallel equivalent thermal resistance of the first-transposition Litz wire based on the first-transposition parallel thermal resistance model and the equivalent parallel thermal conductivity of the enameled copper round wire, and determining the first-transposition equivalent parallel thermal conductivity based on the first-transposition parallel equivalent thermal resistance and the size parameters of the first-transposition Litz wire; The secondary transposition parallel equivalent thermal resistance of the secondary transposition Litz line is determined based on the secondary transposition parallel thermal resistance model and the primary transposition series equivalent thermal resistance, and the second parallel thermal conductivity is determined based on the secondary transposition parallel equivalent thermal resistance and the size parameters of the secondary transposition Litz line.

5. The method for determining the equivalent thermal conductivity of a secondary transposed Litz line according to claim 4, wherein: The method further comprises: Obtaining the diameter of the round copper wire and the thickness of the insulating paint film; determining a volume fraction of the copper round wire based on the diameter and the paint film thickness, and determining a first weight of the second series thermal conductivity and a second weight of the third series thermal conductivity based on the volume fraction; The second equivalent thermal conductivity and the third equivalent thermal conductivity are determined based on the first weight, the second weight, the second series thermal conductivity, the second parallel thermal conductivity, the third series thermal conductivity, and the third parallel thermal conductivity.

6. The method for determining the equivalent thermal conductivity of a secondary transposed Litz line according to claim 4, characterized in that: The third equivalent thermal conductivity is: Where, is the second equivalent thermal conductivity; is the second weight; V m is the volume fraction of copper round wire.

7. A device for determining the equivalent thermal conductivity of a secondary transposed Litz line, characterized in that: include: A series-parallel thermal resistance model construction unit is used to construct a first parallel thermal resistance model along the length direction, a second series thermal resistance model and a second parallel thermal resistance model along the width direction, and a third series thermal resistance model and a third parallel thermal resistance model along the thickness direction of the secondary transposed Litz line; a first equivalent thermal conductivity determining unit, configured to determine a first equivalent thermal conductivity of the secondary transposed Litz line along a length direction based on the first parallel thermal resistance model; a second equivalent thermal conductivity determining unit, configured to determine a second series thermal conductivity and a second parallel thermal conductivity of the secondary transposed Litz line along the width direction based on the second series thermal resistance model and the second parallel thermal resistance model, respectively, and take a weighted sum of the second series thermal conductivity and the second parallel thermal conductivity as the second equivalent thermal conductivity of the secondary transposed Litz line along the width direction; a third equivalent thermal conductivity determining unit, configured to determine a third series thermal conductivity and a third parallel thermal conductivity of the secondary transposed Litz line along the thickness direction based on the third series thermal resistance model and the third parallel thermal resistance model, respectively, and take a weighted sum of the third series thermal conductivity and the third parallel thermal conductivity as a third equivalent thermal conductivity of the secondary transposed Litz line along the thickness direction; The second series thermal conductivity is: The second parallel thermal conductivity is: The second equivalent thermal conductivity is: Where, is the second series thermal conductivity; is the equivalent thermal resistance of the secondary transposition series connection; w is the width of a transposed Litz line; b is the thickness of the Litz line of a single transposition; t 3 is the double-sided thickness of the first polyimide film; t 4 is the bilateral thickness of the resin layer in the secondary transposition Litz line; t 5 is the double-sided thickness of the second polyimide film; dl It is the length of a single enameled round copper wire along the length direction; is the second parallel thermal conductivity; is the secondary transposition parallel equivalent thermal resistance; is the second equivalent thermal conductivity; is the first weight; V m is the volume fraction of copper round wire.

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