Iron core air gap structure and high temperature superconducting toroidal transformer

Abstract

The application relates to the technical field of power equipment, in particular to an iron core air gap structure and a high-temperature superconducting toroidal transformer. The iron core air gap structure comprises a toroidal iron core, a coil winding and an air gap. The coil winding is sleeved on the toroidal iron core, the air gap is arranged in the radial direction of the toroidal iron core, the air gaps are symmetrically distributed on the toroidal iron core, and the air gap cross section profile is any structure except a non-rectangular structure. In this way, by changing the spatial geometric shape of the air gap cross section and the spatial distribution of the air gap, the length of the magnetic flux path or the air gap cross section area is continuously modulated, the magnetic line distribution state is effectively improved, the leakage magnetic flux caused by the air gap edge effect is reduced, and the uniformity of the magnetic induction intensity distribution in the iron core is improved, so that the problems of concentrated magnetic pressure drop, serious leakage magnetic flux and reduced critical current performance of superconducting tapes of the existing high-temperature superconducting toroidal transformer in use are solved.

Description

Technical Field

[0001] This invention relates to the field of power equipment technology, and in particular to a core air gap structure and a high-temperature superconducting toroidal transformer. Background Technology

[0002] Existing high-temperature superconducting toroidal transformers typically employ a planar truncated air-gap structure to adjust the equivalent inductance and prevent core magnetic saturation. However, this type of structure presents the following problems in practical applications: First, when the air-gap end face is planar, the magnetic reluctance of the magnetic circuit undergoes a step change within an extremely short distance, leading to a concentrated magnetic voltage drop. Second, magnetic lines of force bend and escape at the air-gap edge, forming a strong leakage flux. Third, local distortion of the magnetic induction intensity within the core increases the risk of local saturation. Fourth, the vertical magnetic field component generated at the air-gap edge reduces the critical current performance of the superconducting tape.

[0003] There is an urgent need for a novel air gap structure that can reduce magnetoresistance abrupt changes, suppress edge effects, and improve magnetic field uniformity in order to solve the problems of concentrated magnetic voltage drop, severe magnetic leakage, and reduced critical current performance of superconducting tapes that occur in the use of existing high-temperature superconducting toroidal transformers. Summary of the Invention

[0004] The purpose of this invention is to propose a core air gap structure and a high-temperature superconducting toroidal transformer to solve the problems of concentrated magnetic voltage drop, severe magnetic leakage, and reduced critical current performance of superconducting tapes that occur in the use of existing high-temperature superconducting toroidal transformers.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] This application proposes a core air gap structure in its first aspect, comprising:

[0007] toroidal iron core;

[0008] The coil winding is looped around the toroidal iron core.

[0009] The air gap is opened radially through the toroidal core. The air gaps are symmetrically distributed on the toroidal core. The cross-sectional profile of the air gap can be any structure other than a rectangular structure, so that the equivalent magnetic reluctance of the air gap region changes continuously along the magnetic flux path.

[0010] Preferably, the cross-sectional profile of the air gap is any one of a stepped opening structure, a continuous periodic curved surface opening structure, and a fan-shaped opening structure.

[0011] Preferably, if the cross-sectional profile of the air gap is a stepped opening structure, then the air gap has multiple steps, and the width and height of the steps in the same level satisfy a preset proportional relationship.

[0012]

[0013] Where α is the angle between the straight line connecting the beginning and end of the step and the horizontal plane of the step, 0≤α≤45; k takes the value of 1-1.4, and the larger k is, the higher the step height h is.

[0014] Preferably, the number of steps in the air gap is n≥2, and each step has a different height along the magnetic flux direction.

[0015] Preferably, if the cross-sectional profile of the air gap is a continuous periodic curved surface opening structure, then the air gap trajectory satisfies the following relationship expression, which is:

[0016]

[0017] Where l(x) is the air gap trajectory; a is the waveform amplitude; g is the air gap height; and λ is the wavelength.

[0018] Preferably, the air gap of the continuous periodic curved surface opening structure varies periodically along the radial direction of the annular iron core, and the continuous periodic curved surface opening structure is either a sine curved surface structure or a cosine curved surface structure.

[0019] Preferably, if the cross-sectional profile of the air gap is a fan-shaped opening structure, then the angle between the air gap cross-section and the magnetic flux direction satisfies the following relationship expression:

[0020]

[0021] Where θ is the angle between the air gap cross section and the magnetic flux direction.

[0022] In its second aspect, this application proposes a high-temperature superconducting toroidal transformer, wherein a core air gap structure is applied to the high-temperature superconducting toroidal transformer.

[0023] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0024] This invention involves encircling a coil winding around a toroidal core, with an air gap extending radially through the core. The air gaps are symmetrically distributed across the core, and their cross-sectional profiles can be any structure other than a rectangle. By altering the spatial geometry and distribution of the air gap cross-section, continuous modulation of the magnetic flux path length or air gap cross-sectional area is achieved. This also effectively improves the magnetic field distribution, reduces leakage flux caused by air gap edge effects, and enhances the uniformity of magnetic induction intensity distribution within the core. This addresses the problems of concentrated magnetic voltage drop, severe leakage flux, and reduced critical current performance of superconducting strips in existing high-temperature superconducting toroidal transformers. Attached Figure Description

[0025] Figure 1This is a schematic diagram of the overall air gap structure of the present invention.

[0026] Figure 2 This is a schematic diagram of the integration of the annular iron core and the air gap in this invention.

[0027] Figure 3 This is a schematic diagram of the cross-sectional profile of the annular iron core in this invention.

[0028] Figure 4 This is a schematic cross-sectional view of the annular iron core in this invention.

[0029] Figure 5 These are schematic cross-sectional views of different cross-sectional profiles of the air gap in this invention (A, schematic diagram of a rectangular air gap structure; B, schematic diagram of a slanted air gap structure; C, schematic diagram of a continuous periodic curved surface opening structure air gap structure; D, schematic diagram of a stepped air gap structure).

[0030] Figure 6 Comparison of magnetic flux density distribution for different air gap structures.

[0031] Table 1: Basic parameters of transformers.

[0032] Table 2: Basic parameters of toroidal core.

[0033] Table 3: Comparison of different cross-sectional profiles of the air gap.

[0034] Table 4: Comparison of electromagnetic properties of different air gap structures.

[0035] Table 5: Comparison of magnetic flux leakage suppression effects.

[0036] In the diagram, 1-toroidal iron core, 2-coil winding, 3-air gap, 4-stepped opening structure, 5-continuous periodic curved surface opening structure, 6-fan-shaped opening structure, 7-step, 8-reduction, 9-opening. Detailed Implementation

[0037] like Figure 1-6 As shown, to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0038] Example 1

[0039] This embodiment provides a basic introduction to an air gap structure for an iron core, such as... Figure 1-4As shown, an air gap structure for an iron core includes an annular iron core 1, a coil winding 2, and an air gap 3; the coil winding 2 is looped around the annular iron core 1; the air gap 3 is opened radially through the annular iron core 1, and the air gap 3 is symmetrically distributed on the annular iron core 1. The cross-sectional profile of the air gap 3 is any structure other than a rectangular structure, so that the equivalent magnetic reluctance of the air gap 3 region changes continuously along the magnetic flux path.

[0040] Among them, the material of the toroidal core 1 can be silicon steel; the material of the coil winding 2 can be REBCO superconducting tape; at least two air gaps 3 are opened on the toroidal core 1; the cross-sectional profile of the air gap 3 can be any structure other than a rectangular structure, that is, the cross-sectional profile of the air gap 3 can be a stepped opening structure 4, a continuous periodic curved surface opening structure 5, and a fan-shaped opening structure 6.

[0041] In this technical solution, the coil winding 2 is looped around the toroidal core 1; the air gap 3 is opened radially through the toroidal core 1, and the air gap 3 is symmetrically distributed on the toroidal core 1. The cross-sectional profile of the air gap 3 can be any structure other than a rectangular structure. In this way, by changing the spatial geometry of the air gap cross-section and the spatial distribution of the air gap 3, not only can the continuous modulation of the magnetic flux path length or the air gap cross-sectional area be achieved, but also the magnetic field line distribution state can be effectively improved and the leakage flux caused by the air gap edge effect can be reduced. In addition, the uniformity of the magnetic induction intensity distribution inside the core can be improved, so as to solve the problems of concentrated magnetic voltage drop, serious leakage flux and reduced critical current performance of superconducting strips that occur in the use of existing high-temperature superconducting toroidal transformers.

[0042] It should be noted that the magnetic reluctance of a toroidal iron core having any one of the following cross-sectional profiles: stepped open air gap 3 structure, continuous periodic curved surface open air gap 3 structure, and fan-shaped open air gap 3 structure, can be calculated using the following expression:

[0043]

[0044] Among them, R g Total magnetic reluctance; l i denoted as , where is the path of the magnetic field lines; A(l) is the equivalent cross-sectional area varying along the magnetic field path; μ0 is the permeability of free space.

[0045] Example 2

[0046] This example provides a more detailed description of each cross-sectional profile of the air gap 3 and the performance characteristics of each cross-sectional profile.

[0047] like Figure 5If the cross-sectional profile of the air gap 3 is a stepped opening structure 4, then the air gap 3 has multiple steps 7, and the number of steps 7 in the air gap 3 is n≥2. Each step 7 has a different height along the magnetic flux direction, that is, the arrangement direction of the steps 7 can be from low to high from the inner wall of the annular iron core 1 to the outer wall of the annular iron core 1. Among them, the width and height of the steps 7 of the same level meet a preset proportional relationship so that the magnetic reluctance of the air gap region changes continuously in segments along the magnetic flux path. The expression of the preset proportional relationship is as follows:

[0048]

[0049] Where α is the angle between the straight line connecting the beginning and end of the step and the horizontal plane of the step, 0≤α≤45; k takes the value of 1-1.4, and the larger k is, the higher the step height h is.

[0050] In the case where the cross-sectional profile of the air gap 3 is a stepped opening structure 4, the total magnetic reluctance in the stepped air gap 3 structure can be calculated using the following expression:

[0051]

[0052] Among them, R g Total magnetic reluctance; l i Path of magnetic field lines; A i denoted as the equivalent cross-sectional area that varies along the magnetic path; μ0 is the free permeability.

[0053] It should be noted that this annular iron core with a stepped opening structure 4 in the cross-section of the air gap 3 reduces the edge concentration effect of the iron core through segmented magnetic reluctance variation.

[0054] like Figure 5 If the cross-sectional profile of the air gap 3 is a continuous periodic curved surface opening structure 5, the periodic curved surface air gap 3 structure 5 changes periodically along the radial direction of the annular iron core 1, and the continuous periodic curved surface opening structure 5 is either a sine curved surface structure or a cosine curved surface structure.

[0055] In the case where the cross-sectional profile of air gap 3 is a continuous periodic curved surface opening structure 4, the trajectory of air gap 3 satisfies the following relationship expression:

[0056]

[0057] Where l(x) is the air gap trajectory; a is the waveform amplitude; g is the air gap height; and λ is the wavelength.

[0058] This annular iron core with a cross-sectional profile of air gap 3 as a continuous periodic curved surface opening structure 5 can achieve a continuous and smooth change in magnetic reluctance, thereby significantly reducing leakage flux.

[0059] In the case where the cross-sectional profile of the air gap 3 is a stepped opening structure 4, the number of air gaps is at least 2 to 6, and the air gaps are symmetrically distributed along the circumference of the annular iron core.

[0060] In the case where the cross-sectional profile of air gap 3 is a stepped opening structure 4, the following explanation is provided regarding how the number of air gaps is calculated in relation to the total air gap length, magnetomotive force, air gap magnetic reluctance, leakage flux ratio, excitation current, magnetic field uniformity, and magnetic field uniformity coefficient:

[0061] The total air gap length can be calculated using the following expression:

[0062]

[0063] Where g is the total air gap length; g i The length of each air gap.

[0064] The magnetomotive force can be calculated using the following expression:

[0065]

[0066] Where F is the magnetomotive force; Φ is the main magnetic flux; and R is the total magnetic reluctance of the magnetic circuit.

[0067] The air gap reluctance can be calculated using the following expression:

[0068]

[0069] Where g is the total air gap length; k e is the edge effect correction coefficient; A is the air gap cross-sectional area, that is, the contact area between the air gap and the iron core, which is also equal to the iron core cross-sectional area; μ0 is the vacuum permeability.

[0070] The leakage flux ratio can be calculated using the following expression:

[0071]

[0072] Among them, W l Leakage magnetic field energy (stored in the air region V) a (Magnetic field energy in the middle); W t The total magnetic field energy (the entire solution domain V) t (Magnetic field energy in V); B is magnetic flux density, unit T; V a V is the volume of the air region. t Let V be the total solution domain volume.

[0073] The excitation current can be calculated using the following expression:

[0074]

[0075] Where, ΔI m I is the excitation current; m0 The reference value for a rectangular air gap; I m This represents the excitation current corresponding to each type of air gap.

[0076] The homogeneity of a magnetic field can be characterized by the standard deviation of the magnetic induction intensity, and its expression is:

[0077]

[0078] Where σ represents the uniformity of the magnetic field; B represents the magnetic flux density; B a V represents the average magnetic flux density within the evaluation area; V is the volume of the evaluation area, which is the volume of all calculated areas except for the iron core and coil during simulation.

[0079] The magnetic field homogeneity coefficient can be calculated using the following expression:

[0080]

[0081] Where k is the magnetic field homogeneity coefficient; B a The average value of the magnetic induction intensity within the region is used to evaluate the magnetic field uniformity.

[0082] It should be noted that the vertical magnetic field component is the peak value of the magnetic field component perpendicular to the strip surface in the vicinity of the air gap; the reduction of the vertical magnetic field component is beneficial to improving the critical current performance and operational stability of the superconducting strip, and is used to compare the suppression effect of leakage flux at the air gap.

[0083] like Figure 5 If the cross-sectional profile of the air gap 3 is a fan-shaped opening structure 6, the constriction 8 of the fan-shaped opening structure 6 faces the inner wall of the annular iron core 1, and the opening 9 of the fan-shaped opening structure 8 faces the outer wall of the annular iron core 1.

[0084] When the cross-sectional profile of the air gap 3 is a fan-shaped opening structure 6, the angle between the cross-section of the air gap 3 and the magnetic flux direction satisfies the following relationship expression:

[0085]

[0086] Where θ is the angle between the air gap cross section and the magnetic flux direction.

[0087] When the cross-sectional profile of the air gap 3 is a fan-shaped opening structure 6, the equivalent magnetic circuit length can be calculated by the following expression:

[0088]

[0089] Among them, l eqθ is the effective magnetic path length; g is the total air gap length; θ is the angle between the air gap cross section and the magnetic flux direction.

[0090] The cross-sectional profile of the air gap 3 is a fan-shaped opening structure 6, which increases the magnetic flux path length and thus achieves a gradual change in magnetic resistance.

[0091] The above introduces the toroidal core with stepped opening air gap 3 structure, the toroidal core with continuous periodic curved surface opening structure air gap 3 structure, and the toroidal core with fan-shaped opening structure. Based on the above calculations, the electromagnetic performance and leakage magnetic field suppression effect of the toroidal core with rectangular air gap 3 structure, the toroidal core with stepped opening air gap 3 structure, the toroidal core with continuous periodic curved surface opening structure air gap 3 structure, and the toroidal core with fan-shaped opening structure are tested (among which, the magnetic field distribution map and the magnetic induction intensity contour map are obtained based on finite element electromagnetic field simulation, that is, under the same model size, material parameters and boundaries, and the winding is excited by the rated voltage, and the secondary winding is in the open circuit state, the comparison analysis is performed). The specific steps are as follows (1)-(5):

[0092] (1) Design a single-phase high-temperature superconducting toroidal transformer with silicon steel core and REBCO superconducting tape winding material. The parameters are shown in Table 1.

[0093] Table 1 shows the basic parameters of the transformer.

[0094]

[0095] (2) Based on the basic parameters of the transformer, determine the basic parameters of the toroidal core, as shown in Table 2:

[0096] Table 2 shows the basic parameters of the toroidal core.

[0097]

[0098] (3) An air gap is set in the annular iron core. The number of air gaps is 2, the air gaps are symmetrically distributed, and the total length of the air gaps is 5mm. The comparison of the annular iron core with rectangular air gap 3 structure, stepped opening air gap 3 structure, continuous periodic curved surface opening structure air gap 3 structure and fan-shaped opening structure is shown in Table 3 as follows:

[0099] Table 3 Comparison of different cross-sectional profiles of the air gap

[0100]

[0101] (4) Using the finite element method, a comparative analysis was conducted under the same excitation conditions. Specifically, the following operations were performed: extracting the magnetic induction intensity distribution; calculating the leakage flux ratio; and calculating the excitation current. The electromagnetic performance of different air gap structures was compared in Table 4 below.

[0102] Table 4 compares the electromagnetic performance of different air gap structures.

[0103]

[0104] As shown in Table 4, compared with the traditional rectangular air gap structure, all non-planar air gap structures can effectively reduce the leakage flux ratio; among them, the leakage flux ratio of the sinusoidal air gap structure is reduced to 6.96%, a decrease of 7.3%; the magnetic field uniformity coefficient is significantly reduced, indicating that the magnetic induction intensity distribution is more uniform; the vertical magnetic field component is significantly reduced, which is beneficial to improving the operational stability of the superconducting tape; at the same time, the excitation current is reduced.

[0105] (5) Results analysis, as shown in Table 5:

[0106] Table 5 shows the comparison of leakage flux suppression effects.

[0107]

[0108] The experimental results above show that the present invention, through nonlinear magnetoresistive modulation, transforms the magnetoresistive distribution in the magnetic circuit from abrupt change to continuous change, thereby achieving synergistic optimization of leakage flux suppression and magnetic field uniformity improvement without significantly increasing the excitation current. In addition, the nonlinear air gap structure can significantly reduce leakage flux; the sinusoidal structure has the best effect; the magnetic field distribution is more uniform; and the excitation current change is controllable.

[0109] Therefore, by changing the spatial geometry of the air gap cross-section and the spatial distribution of the air gap, this invention not only achieves continuous modulation of the magnetic flux path length or the air gap cross-sectional area, but also effectively improves the magnetic field line distribution and reduces leakage flux caused by air gap edge effects. Furthermore, it enhances the uniformity of magnetic induction intensity distribution within the core, thereby solving the problems of concentrated magnetic voltage drop, severe leakage flux, and reduced critical current performance of superconducting tapes that occur in existing high-temperature superconducting toroidal transformers during use.

[0110] Although the invention has been described herein with reference to several illustrative embodiments, it should be understood that many other modifications and implementations can be devised by those skilled in the art, which will fall within the scope and spirit of the principles disclosed herein. More specifically, various variations and modifications can be made to the components and / or layout of the subject matter arrangement within the scope of the disclosure, drawings, and claims. Besides variations and modifications to the components and / or layout, other uses will be apparent to those skilled in the art.

Claims

1. A core air gap structure, characterized in that: include: Annular iron core (1); Coil winding (2), the coil winding (2) is looped around the annular iron core (1); Air gap (3) is opened through the radial direction of the annular iron core (1). The air gap (3) is symmetrically distributed on the annular iron core (1). The cross-sectional profile of the air gap (3) is any structure other than a rectangular structure, so that the equivalent magnetic resistance of the air gap (3) region changes continuously along the magnetic flux path.

2. A core air gap structure according to claim 1, characterized in that: The cross-sectional profile of the air gap (3) is any one of the following: stepped opening structure (4), continuous periodic curved surface opening structure (5), and fan-shaped opening structure (6).

3. A core air gap structure according to claim 2, characterised in that: If the cross-sectional profile of the air gap (3) is a stepped opening structure (4), then the air gap (3) has multiple steps (7), and the width and height of the same step (7) satisfy a preset proportional relationship, the expression of which is as follows: ； Where α is the angle between the straight line connecting the beginning and end of the step and the horizontal plane of the step, 0≤α≤45; k takes the value of 1-1.4, and the larger k is, the higher the step height h is.

4. A core air gap structure according to claim 3, characterized in that: The number of steps (7) in the air gap (3) is n≥2, and each step (7) has a different height along the magnetic flux direction.

5. A core air gap structure as defined in claim 2, wherein: If the cross-sectional profile of the air gap (3) is a continuous periodic curved surface opening structure (5), then the trajectory of the air gap (3) satisfies the following relational expression, which is: ； Where l(x) is the air gap trajectory; a is the waveform amplitude; g is the air gap height; and λ is the wavelength.

6. A core air gap structure according to claim 5, characterized in that: The air gap (3) of the continuous periodic curved surface opening structure (5) varies periodically along the radial direction of the annular iron core (1), and the continuous periodic curved surface opening structure (5) is either a sine curved surface structure or a cosine curved surface structure.

7. A core air gap structure as defined in claim 2 wherein: If the cross-sectional profile of the air gap (3) is a fan-shaped opening structure (6), then the angle between the cross-section of the air gap (3) and the magnetic flux direction satisfies the following relationship expression: ； Where θ is the angle between the air gap cross section and the magnetic flux direction.

8. The air gap structure of the iron core according to claim 7, characterized in that: The fan-shaped opening structure (6) has a constriction (8) facing the inner wall of the annular iron core (1), and the fan-shaped opening structure (6) has an opening (9) facing the outer wall of the annular iron core (1).

9. A high-temperature superconducting toroidal transformer, characterized in that, The core air gap structure described in claims 1-8 is applied to a high-temperature superconducting toroidal transformer.

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