Anti-DC magnetic bias double-iron-core current transformer and preparation and simulation verification method thereof

Abstract

The invention relates to the technical field of current transformers, in particular to an anti-direct-current magnetic bias double-iron-core current transformer and a preparation and simulation verification method of the anti-direct-current magnetic bias double-iron-core current transformer. According to the preparation method of the anti-DC magnetic bias double-iron-core current transformer, the size parameters of the double iron cores are determined firstly, the first iron core and the second iron core are obtained according to the size parameters, the air gap size is determined according to the electrical performance index of the current transformer, and the air gap is formed in the preset position of the first iron core; a first coil is wound on a first iron core provided with an air gap, a second coil is wound on a second iron core, the first coil and the second coil are arranged in parallel, and the first iron core and the second iron core are stacked in the preset direction. The magnetic saturation phenomenon of the current transformer can be improved, the linearity difference of the current transformer is avoided, and the precision of the current transformer is greatly improved.

Description

Technical Field

[0001] The present application relates to the technical field of current transformers, and in particular to a DC bias-resistant double-core current transformer and a preparation and simulation verification method thereof. Background Art

[0002] A current transformer is a device used to measure the current in an AC circuit. It makes current measurement safer and more convenient by converting high current into a lower, easier-to-handle current. Current transformers are widely used in power systems, industrial control, instrumentation, and other fields.

[0003] In order to prevent the current transformer from magnetic saturation, which leads to increased measurement errors, the current transformer is set to a double-core type and an air gap is set on the core. Improper setting of the air gap not only fails to improve the magnetic saturation phenomenon of the current transformer, but also leads to poor linearity of the current transformer, seriously affecting the measurement accuracy of the current transformer. Therefore, how to set the air gap size to meet the measurement accuracy of the current transformer has become an urgent problem to be solved. Summary of the invention

[0004] In view of this, the embodiments of the present application provide a double-core current transformer resistant to DC bias and a preparation and simulation verification method thereof, which can effectively solve the problem of improper air gap setting in the existing solution, resulting in poor linearity of the current transformer and seriously affecting the measurement accuracy of the current transformer.

[0005] In a first aspect, an embodiment of the present application provides a method for preparing a DC bias resistant dual-core current transformer, comprising: determining size parameters of the dual cores to obtain a first core and a second core;

[0006] Determining the size of the air gap according to the electrical performance index of the current transformer, and setting the air gap at a preset position of the first iron core;

[0007] Winding a first coil on the first iron core provided with the air gap, winding a second coil on the second iron core, and connecting the first coil and the second coil in series;

[0008] The first iron core and the second iron core are stacked along a preset direction.

[0009] In some embodiments, determining the air gap size according to the electrical performance index of the current transformer includes:

[0010] Selecting the initial air gap size according to the preset ratio of the equivalent length of the magnetic circuit of the core;

[0011] Calculating the initial DC magnetic bias current and the initial sinusoidal half-wave current of the double-core current transformer after the core is gapped according to the selected initial air gap size;

[0012] If the initial DC bias current is not within the preset bias current range and / or the initial sinusoidal half-wave current is not within the preset half-wave current range, increasing the air gap size;

[0013] Calculate the current DC magnetic bias current and the current half-sine wave current according to the increased air gap size;

[0014] If the current DC bias current is not within the preset bias current range and / or the current sinusoidal half-wave current is not within the preset half-wave current range, increase the air gap size again until the newly increased air gap size satisfies the corresponding calculated DC bias current within the preset bias current range and / or the sinusoidal half-wave current within the preset half-wave current range.

[0015] In some embodiments, after determining the air gap size according to the electrical performance index of the current transformer, the preparation method further includes:

[0016] Calculating the error, phase angle difference and ratio difference of the double-core current transformer after the core is air-gapped according to the newly increased air gap size;

[0017] After stacking the first iron core and the second iron core along a preset direction, the preparation method further includes:

[0018] The phase angle difference and ratio difference of the current transformer are tested by using a testing device.

[0019] In some embodiments, determining the size parameters of the dual core to obtain the first core and the second core includes:

[0020] Obtaining a minimum cross-sectional area of ​​the first core according to electrical performance requirements of the current transformer;

[0021] Determining a cross-sectional area of ​​the first core according to the minimum cross-sectional area and a space size limitation of the current transformer;

[0022] The minimum cross-sectional area is obtained by the following formula:

[0023]

[0024] Where: k 2z represents the winding impedance coefficient of the first core, I 2n Represents the rated secondary current of the current transformer; Z 2n represents the rated secondary load of the current transformer; f represents the rated operating frequency of the current transformer; N 2 Indicates the number of turns of the secondary winding of the current transformer; B n represents the rated magnetic flux density of the first core.

[0025] In some embodiments, the half-sine wave current is obtained by the following formula:

[0026]

[0027] Where: I hw I represents the half-wave sinusoidal current of the current transformer; dc represents the DC magnetic bias current of the current transformer;

[0028] The DC bias current is obtained by the following formula:

[0029]

[0030] Where: H am represents the saturation magnetic field intensity of the first core after the air gap is opened; N 1 Indicates the number of turns of the secondary winding of the current transformer; l a represents the equivalent length of the magnetic circuit of the first core;

[0031] The saturation magnetic field intensity of the first core after the air gap is opened is obtained by the following formula:

[0032]

[0033] Among them: B m represents the saturation magnetic field density of the first core; μ a represents the equivalent relative magnetic permeability of the first core after the air gap is opened; μ 0 Indicates the magnetic permeability of air;

[0034] The equivalent relative magnetic permeability of the first iron core after the air gap is opened is obtained by the following formula:

[0035]

[0036] Where: μ Fe represents the relative magnetic permeability of the first core; l g represents the initial air gap size.

[0037] In some embodiments, the error of the current transformer is obtained by the following formula:

[0038]

[0039] Where: i represents the error of the current transformer; Z 2n Represents the rated secondary load of the current transformer; Z 2rrepresents the secondary winding impedance of the current transformer, j represents the phase difference; ω represents the rated angular frequency; N 2 Represents the number of turns of the secondary winding of the current transformer; π a represents the equivalent relative magnetic permeability of the first core after the air gap is opened; π 0 Represents the magnetic permeability of air; S a represents the cross-sectional area of ​​the first core; S c represents the cross-sectional area of ​​the second core; l a represents the equivalent length of the magnetic circuit of the first core; l c represents the equivalent length of the magnetic circuit of the second core;

[0040] The ratio difference and the phase angle difference are obtained by the following formula:

[0041]

[0042] Wherein: ξ represents the ratio difference of the current transformer; α represents the impedance angle between the secondary winding of the current transformer and the load; θ represents the iron loss angle of the current transformer; δ represents the phase angle difference of the current transformer.

[0043] In a second aspect, an embodiment of the present application provides a simulation verification method for a DC bias resistant double-core current transformer, after obtaining the DC bias resistant double-core current transformer using at least one preparation method described in the first aspect, the DC bias resistant double-core current transformer is simulated and verified, including:

[0044] Constructing a three-dimensional geometric model of the current transformer;

[0045] Importing the three-dimensional geometric model into electromagnetic field finite element software;

[0046] Based on the relevant configuration parameters in the electromagnetic field finite element software, simulation verification is carried out.

[0047] In some embodiments, the three-dimensional geometric model includes: a primary conductor of the current transformer, a first core of the current transformer, a secondary core of the current transformer, a secondary winding of the current transformer, and an insulation structure of the current transformer.

[0048] In some embodiments, based on relevant configuration parameters in the electromagnetic field finite element software, performing simulation verification includes:

[0049] Setting the boundary conditions of the current transformer in the transient magnetic field module of the electromagnetic field finite element software;

[0050] Dividing the grid of the three-dimensional geometric model;

[0051] Set up time-varying excitation, coil parameters, and core magnetization curve;

[0052] Defining the resistive and inductive loads of the current transformer in the circuit module of the electromagnetic field finite element software;

[0053] Arranging two inductance elements in the circuit module, and connecting the two inductance elements to the relevant circuit;

[0054] Set simulation parameters and run the simulation.

[0055] In a third aspect, an embodiment of the present application provides a double-core current transformer that is resistant to DC bias, and the double-core current transformer that is resistant to DC bias is obtained by using at least one of the preparation methods described in the first aspect; wherein, the double-core current transformer that is resistant to DC bias includes: a first core and a second core, an air gap is provided at a preset position of the first core, and the length of the air gap is determined according to the electrical performance indicators of the current transformer, a first coil is wound on the first core, and a second coil is wound on the second core, the first coil and the second coil are connected in series, and the first core and the second core are stacked along a preset direction.

[0056] The embodiments of the present application have the following beneficial effects:

[0057] The preparation method of the DC bias resistant double-core current transformer of the present application first confirms the size parameters of the double cores, obtains the first core and the second core according to the size parameters, determines the air gap size according to the electrical performance indicators of the current transformer, and sets the air gap at a preset position of the first core, winds the first coil on the first core with the air gap, winds the second coil on the second core, and sets the first coil and the second coil in parallel, and stacks the first core and the second core in a preset direction. The preparation method of the present application confirms the air gap size according to the electrical performance indicators of the current transformer, which can not only improve the magnetic saturation phenomenon of the current transformer, but also avoid the poor linearity of the current transformer, thereby greatly improving the accuracy of the current transformer. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0059] Figure 1 A first process diagram of a method for preparing a DC bias-resistant dual-core current transformer according to an embodiment of the present application is shown;

[0060] Figure 2A second process diagram of the method for preparing a DC bias resistant double-core current transformer according to an embodiment of the present application is shown;

[0061] Figure 3 A third process diagram of the method for preparing a DC bias resistant double-core current transformer according to an embodiment of the present application is shown;

[0062] Figure 4 A fourth process diagram of the method for preparing a DC bias resistant double-core current transformer according to an embodiment of the present application is shown;

[0063] Figure 5 A first flow chart of a simulation verification method for a DC bias-resistant dual-core current transformer according to an embodiment of the present application is shown;

[0064] Figure 6 A second flow chart of the simulation verification method of the DC bias-resistant dual-core current transformer according to an embodiment of the present application is shown;

[0065] Figure 7 A schematic diagram of the winding of a first coil and a second coil on a double core of a double core current transformer resistant to DC bias magnetic field according to an embodiment of the present application is shown.

[0066] Description of main component symbols:

[0067] 10: first iron core; 20: second iron core; 101: air gap; 102: first coil; 201: second coil. DETAILED DESCRIPTION

[0068] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments.

[0069] The components of the embodiments of the present application generally described and shown in the drawings herein may be arranged and designed in various configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application.

[0070] Hereinafter, the terms "including", "having" and their cognates that can be used in various embodiments of the present application are intended only to indicate specific features, numbers, steps, operations, elements, components or a combination of the foregoing items, and should not be understood as first excluding the existence of one or more other features, numbers, steps, operations, elements, components or a combination of the foregoing items or increasing the possibility of one or more features, numbers, steps, operations, elements, components or a combination of the foregoing items. In addition, the terms "first", "second", "third" and the like are only used to distinguish descriptions and cannot be understood as indicating or implying relative importance.

[0071] Unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meanings as those generally understood by those skilled in the art to which the various embodiments of the present application belong. The terms (such as those defined in generally used dictionaries) will be interpreted as having the same meanings as the contextual meanings in the relevant technical field and will not be interpreted as having idealized meanings or overly formal meanings unless clearly defined in the various embodiments of the present application.

[0072] In conjunction with the accompanying drawings, some embodiments of the present application are described in detail below. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0073] Taking into account the problems in the prior art such as poor linearity of the current transformer due to improper air gap setting, which seriously affects the measurement accuracy of the current transformer, the present application provides a DC bias-resistant double-core current transformer and a preparation and simulation verification method thereof. The preparation method of the present application determines the air gap size according to the electrical performance indicators of the current transformer, which can not only improve the magnetic saturation phenomenon of the current transformer, but also avoid the poor linearity of the current transformer, thereby greatly improving the accuracy of the current transformer.

[0074] The preparation method of the DC bias resistant double-core current transformer is described below in conjunction with some specific embodiments.

[0075] Figure 1 A schematic flow chart of a method for preparing a DC bias-resistant dual-core current transformer according to an embodiment of the present application is shown. Exemplarily, the preparation method includes steps S101-S104:

[0076] Step S101: Determine the size parameters of the dual core to obtain a first core and a second core.

[0077] Specifically, the size parameters of the double core can be determined according to the electrical performance requirements of the current transformer; the size parameters of the double core can also be determined according to the spatial size limitations of the current transformer; the size parameters of the double core can also be confirmed according to the electrical performance requirements and spatial size limitations of the current transformer.

[0078] The materials of the first iron core and the second iron core can be set according to actual application conditions. Exemplarily, the first iron core is a silicon steel core, and the second iron core is an alloy iron core.

[0079] Step S102: determining the size of the air gap according to the electrical performance index of the current transformer, and setting the air gap at a preset position of the first iron core.

[0080] The air gap size can be directly calculated based on the electrical performance indicators of the current transformer, or an initial air gap size can be selected first, and then the influence of the air gap on the electrical performance indicators is confirmed by calculation, and the initial air gap size is adjusted according to the influence to meet the requirements of the electrical performance indicators of the current transformer.

[0081] It is understandable that the electrical performance index of the current transformer may include the current of the current transformer, the electrical performance index of the current transformer may also include the magnetic permeability of the current transformer, and the electrical performance index of the current transformer may also include the phase angle difference and ratio difference of the current transformer.

[0082] The preset position of the first iron core can be set according to actual application conditions. Two air gaps can be set on the first iron core, and the size of each of the two air gaps is half of the total air gap size. Four air gaps can also be set on the first iron core, and the size of each of the four air gaps is one quarter of the total air gap size.

[0083] Step S103: Winding a first coil on a first iron core with an air gap, winding a second coil on a second iron core, and connecting the first coil and the second coil in series.

[0084] It can be understood that the first coil includes a primary side coil wound around the first iron core and a secondary side coil wound around the first iron core, the second coil includes a primary side coil wound around the second iron core and a secondary side coil wound around the second iron core, the primary side coil of the first iron core and the primary side coil of the second iron core are connected in series, and the secondary side coil of the first iron core and the secondary side coil of the second iron core are connected in series, and the length of the coil can be set according to actual application conditions.

[0085] As another implementation, the first iron core and the second iron core may be stacked along the thickness direction of the iron core and then wound with a coil.

[0086] Step S104: stacking the first iron core and the second iron core along a preset direction.

[0087] It can be understood that the preset direction is the thickness direction of the core.

[0088] In this embodiment, the current transformer is configured as a double-core type, and an air gap is provided on one of the cores. The air gap size is determined according to the electrical performance index of the current transformer. The air gap is utilized to prevent magnetic saturation of the core, thereby improving the linear operating current range of the current transformer. By optimizing the air gap size, the error of the transformer in the transient process can be reduced, thereby improving the accuracy and reliability of the measurement.

[0089] In one embodiment, Figure 2 Another schematic flow chart of a method for preparing a DC bias-resistant dual-core current transformer according to an embodiment of the present application is shown. Based on the above embodiment, step S101 includes:

[0090] Step S201: Obtain the minimum cross-sectional area of ​​the first core according to the electrical performance requirements of the current transformer.

[0091] The electrical properties of the current transformer may include the current of the current transformer, the electrical properties of the current transformer may also include the frequency of the current transformer, and the electrical properties of the current transformer may also include the magnetic permeability of the current transformer.

[0092] For example, the minimum cross-sectional area can be obtained using the following formula:

[0093]

[0094] Where: k 2z Represents the winding impedance coefficient of the first core, I 2n Indicates the rated secondary current of the current transformer; Z 2n represents the rated secondary load of the current transformer; f represents the rated operating frequency of the current transformer; N 2 Indicates the number of turns of the secondary winding of the current transformer; B n Indicates the rated magnetic flux density of the first core.

[0095] For example, the winding impedance coefficient of the first core of this embodiment is in the range of 1.1-1.5, which can be set according to the actual application situation. The rated secondary current of the current transformer is 5A, the rated secondary load is 0.2Ω, the rated frequency is 50Hz, the number of turns of the secondary winding is 60 turns, and the rated magnetic flux density of the first core can be set according to the actual application situation. For example, the value range is 0.1-0.2T. Substituting the parameters of the above example into the formula, S a =5.63(cm 2 ).

[0096] Step S202: Determine the cross-sectional area of ​​the first core according to the minimum cross-sectional area and the space size limitation of the current transformer.

[0097] For example, according to the size limit of the current transformer in actual application, the outer diameter of the iron core is selected to be 8.5 cm, the inner diameter of the iron core is 5.5 cm, and the height of the iron core is 4 cm. For example, the size of the second iron core is the same as that of the first iron core. According to the parameters of the above example, the cross-sectional area of ​​the first iron core is 5.76 (cm 2 ).

[0098] In this embodiment, the minimum cross-sectional area of ​​the first iron core is obtained according to the electrical performance of the current transformer, and the cross-sectional area of ​​the first iron core is confirmed according to the minimum cross-sectional area and the spatial size limitation of the current transformer, which can ensure that the electrical performance of the current transformer meets the predetermined electrical performance requirements. Confirming the cross-sectional area of ​​the first iron core according to the spatial size limitation can ensure that the current transformer can be installed smoothly and adapt to the specific installation environment.

[0099] In one embodiment, Figure 3 Another schematic flow chart of the method for preparing a DC bias-resistant dual-core current transformer according to an embodiment of the present application is shown. Based on the above embodiment, determining the air gap size according to the electrical performance index of the current transformer in step S102 includes:

[0100] Step S301: selecting an initial air gap size according to a preset ratio of the equivalent length of the core magnetic circuit.

[0101] The size of the preset ratio can be set according to the actual application situation. The initial air gap size can be 0.01% of the equivalent length of the iron core magnetic circuit; the initial air gap size can also be 0.02% of the equivalent length of the iron core magnetic circuit; the initial air gap size can also be 0.1% of the equivalent length of the iron core magnetic circuit. Exemplarily, the initial air gap size is 0.02%-0.5% of the equivalent length of the iron core magnetic circuit.

[0102] For example, the equivalent length of the core magnetic circuit is calculated by the following formula:

[0103] l a =π(r o +r i );

[0104] Where: l a Represents the equivalent length of the core magnetic circuit of the current transformer; r o Represents the outer radius of the current transformer core; r i Represents the inner radius of the current transformer core. The inner radius and outer radius of the current transformer core are obtained according to the inner diameter and outer diameter of the current transformer core. Substituting the inner radius and outer radius of the example into the formula, the equivalent length of the core magnetic circuit is 21.99 (cm) and the initial air gap size is 0.1 mm.

[0105] Step S302: Calculate the initial DC magnetic bias current and initial sinusoidal half-wave current of the double-core current transformer after the core is gapped according to the selected initial air gap size.

[0106] Specifically, the equivalent relative magnetic permeability of the first iron core after the air gap is opened is calculated according to the selected initial air gap size, the saturation magnetic field strength of the first iron core after the air gap is opened is calculated according to the equivalent relative magnetic permeability of the first iron core after the air gap is opened, the DC bias current is calculated according to the saturation magnetic field strength of the first iron core after the air gap is opened, and the sinusoidal half-wave rectification is calculated according to the DC bias current.

[0107] For example, the equivalent relative magnetic permeability of the first core after the air gap is opened is obtained by the following formula:

[0108]

[0109] Where: μ Fe represents the relative magnetic permeability of the first core; l g represents the initial air gap size; l a represents the equivalent length of the magnetic circuit of the first core. Specifically, μ Fe It represents the relative permeability of the first core in the linear region of the initial magnetization curve. For example, μ Fe is 28000, and μ Fe Substituting the parameters of the above example into the formula, we get μ a It is 1931.5.

[0110] The saturation magnetic field intensity of the first core after the air gap is opened is obtained by the following formula:

[0111]

[0112] Among them: B m represents the saturation magnetic field density of the first core; μ a Indicates the equivalent relative permeability of the first core after the air gap is opened; μ 0 Indicates the magnetic permeability of air; for example, μ 0 is the magnetic permeability of air, μ 0 =4π×10 -7 H / m, Substituting the parameters of the above example into the above formula, we get H am It is 741.6 (A / m).

[0113] The DC bias current is obtained by the following formula:

[0114]

[0115] Where: N 1 Indicates the number of turns of the secondary winding of the current transformer; N 1Example 1, substitute the parameters of the above example, and get I dc =163.1(A).

[0116] The half-sine wave current is obtained by the following formula:

[0117]

[0118] Where: I hw represents the sinusoidal half-wave current of the current transformer; Substituting the parameters of the above example into the above formula, we get I hw is 256.2(A).

[0119] Step S303: If the initial DC bias current is not within the preset bias current range and / or the initial sinusoidal half-wave current is not within the preset half-wave current range, then increase the air gap size.

[0120] The preset bias current and the preset half-wave current can be set according to the actual application situation. Schematically, the preset bias current is the standard limit value of the bias current, and the preset half-wave current is the standard limit value of the half-wave current. It can be understood that the air gap size can be adjusted only according to the DC bias current, that is, when the initial DC bias current is not within the preset bias current range, the air gap size is increased; the air gap size can also be adjusted only according to the sinusoidal half-wave current, that is, when the initial sinusoidal half-wave current is not within the preset half-wave current range, the air gap size is adjusted; the air gap size can also be adjusted according to the DC bias current and the sinusoidal half-wave current, that is, when the initial DC bias current is not within the preset bias current range and the initial sinusoidal half-wave current is not within the preset half-wave current range, the air gap size is increased.

[0121] The increase of the air gap size can be set according to actual application conditions. The air gap size can be increased according to a certain ratio, or the air gap size can be increased randomly. Exemplarily, the air gap size can be increased by 0.1 percent of the initial air gap size each time.

[0122] Step S304: Calculate the current DC bias current and the current half-sine wave current according to the increased air gap size.

[0123] According to the increased air gap size and the above formula, the DC bias current and the sinusoidal half-wave current are recalculated. It can be understood that if the calculated DC bias current is within the preset bias current range and\or the sinusoidal half-wave current is within the preset half-wave current range, the increased air gap size is set to the final air gap size.

[0124] Step S305: If the current DC bias current is not within the preset bias current range and / or the current sinusoidal half-wave current is not within the preset half-wave current range, increase the air gap size again until the newly increased air gap size satisfies the corresponding calculated DC bias current within the preset bias current range and / or the sinusoidal half-wave current within the preset half-wave current range.

[0125] If the current DC bias current is not within the preset bias current range and / or the current sinusoidal half-wave current is not within the preset half-wave current range, increase the air gap size by 0.1 percent of the initial air gap size, and recalculate the sinusoidal half-wave current and DC bias current based on the increased air gap size and the above formula until the adjusted air gap size satisfies the DC bias current being within the preset bias current range and / or the sinusoidal half-wave current being within the preset half-wave current range.

[0126] In this embodiment, the initial air gap size is first selected according to the preset ratio of the equivalent length of the iron core magnetic circuit, so that a relatively reasonable magnetic circuit structure can be established in the early stage of design, and the DC bias current and sinusoidal half-wave current of the current transformer are calculated according to the selected initial air gap size, and the calculated DC bias current and sinusoidal half-wave current are judged. If the DC bias current is not within the preset bias current range and / or the sinusoidal half-wave current is not within the preset half-wave current range, the air gap size is adjusted until the latest increased air gap size satisfies the corresponding calculated DC bias current within the preset bias current range and / or the sinusoidal half-wave current is within the preset half-wave current range. The magnetic circuit parameters can be further refined to ensure that the current transformer can accurately reflect the changes in the measured current during the measurement process. The current transformer of the present application, taking into account the influence of the DC bias current and the sinusoidal half-wave current on the current transformer, can effectively ensure the measurement accuracy of the current transformer under DC bias conditions and improve the stability and reliability of the current transformer under complex conditions.

[0127] In one embodiment, Figure 4 Another schematic flow chart of the method for preparing a DC bias-resistant dual-core current transformer according to an embodiment of the present application is shown. Based on the above embodiment, after determining the air gap size according to the electrical performance index of the current transformer in step S102, the preparation method further includes:

[0128] Step S401: Calculate the error, phase angle difference and ratio difference of the double-core current transformer after the core is gapped according to the newly increased air gap size.

[0129] For example, the error of the current transformer is obtained by the following formula:

[0130]

[0131] Where: iRepresents the error of the current transformer; Z 2n Indicates the rated secondary load of the current transformer; Z 2r represents the secondary winding impedance of the current transformer, j represents the phase difference; ω represents the rated angular frequency; N 2 Indicates the number of turns of the secondary winding of the current transformer; μ a Indicates the equivalent relative permeability of the first core after the air gap is opened; μ 0 Represents the magnetic permeability of air; S a represents the cross-sectional area of ​​the first core; S c represents the cross-sectional area of ​​the second core; l a Represents the equivalent length of the magnetic circuit of the first core; l c It represents the equivalent length of the magnetic circuit of the second core. Specifically, ω=2πf.

[0132] Furthermore, if the error calculated according to the above formula is greater than the standard limit of the error, the newly increased air gap size can be adaptively adjusted to meet the requirements of both the error and the current.

[0133] The ratio difference and phase angle difference are obtained by the following formula:

[0134]

[0135] Where: ξ represents the ratio difference of the current transformer; α represents the impedance angle of the secondary winding of the current transformer and the load; θ represents the iron loss angle of the current transformer; δ represents the phase angle difference of the current transformer. For example, the impedance angle of the secondary winding of the current transformer and the load is calculated using the following formula:

[0136]

[0137] Where: Im(Z 2n +Z 2r ) represents the total imaginary impedance of the secondary side of the current transformer; Re(Z 2n +Z 2r ) represents the real part of the total impedance on the secondary side of the current transformer.

[0138] After stacking the first iron core and the second iron core along a preset direction, the preparation method further includes:

[0139] Step S402: using a testing device to test the phase angle difference and ratio difference of the current transformer.

[0140] The phase angle difference can be measured using a phase bridge or a vector analyzer. Furthermore, the actual ratio difference and phase angle difference measured at different current values ​​of the current transformer can be compared with the ratio difference and phase angle difference calculated theoretically to verify the current transformer.

[0141] In this embodiment, the air gap size is further adjusted by calculating the error, ratio difference and phase angle difference, and the phase angle difference and ratio difference of the current transformer are tested using a test device. The test results are compared with the calculated results to further verify the accuracy of the current transformer, ensure that the current transformer complies with the requirements of relevant standards and regulations, and ensure the quality of the current transformer.

[0142] It is worth noting that the values ​​of the above parameters are only examples and can be adaptively adjusted according to specific circumstances.

[0143] The present application also provides a simulation verification method for a DC bias-resistant double-core current transformer. Figure 5 A flow chart of a simulation verification method for a DC bias-resistant dual-core current transformer according to an embodiment of the present application is shown. After obtaining a DC bias-resistant dual-core current transformer using the above-mentioned preparation method, a simulation verification is performed on the DC bias-resistant dual-core current transformer, including:

[0144] Step S501: construct a three-dimensional geometric model of a current transformer.

[0145] Specifically, the three-dimensional geometric model can be created using software, such as SolidWorks, AutoCAD, CATIA, etc., or electromagnetic field limited software.

[0146] It can be understood that the three-dimensional geometric model includes the primary conductor of the current transformer, the first iron core of the current transformer, the secondary iron core of the current transformer, the secondary winding of the current transformer and the insulation structure of the current transformer. Furthermore, the three-dimensional geometric model also includes the supporting structure of the current transformer, the casing of the current transformer and the terminal blocks of the current transformer, the shielding layer of the current transformer, etc.

[0147] Step S502: Import the three-dimensional geometric model into electromagnetic field finite element software.

[0148] It can be understood that the electromagnetic field finite element software of the present application can be any electromagnetic field finite element software, the electromagnetic field finite element software can be ANSYS Maxwell, the electromagnetic field finite element software can also be COMSOL Multiphysics, the electromagnetic field finite element software can also be CST Studio Suite, the electromagnetic field finite element software can also be Opera, etc., exemplary, the electromagnetic field finite element software is ANSYS Maxwell.

[0149] Step S503: Perform simulation verification based on relevant configuration parameters in the electromagnetic field finite element software.

[0150] Electromagnetic field finite element software is used to perform simulation verification based on the parameters of the current transformer. For demonstration, parameter scanning is performed according to different proportions of the rated current to simulate the output of the current transformer at different excitation currents.

[0151] In this embodiment, by constructing a three-dimensional geometric model of the current transformer, the electromagnetic field distribution of the transformer in a real working environment can be accurately simulated, and then the three-dimensional geometric model is imported into the electromagnetic field finite element software, and verification simulation is performed according to the relevant configuration parameters in the electromagnetic field finite element software. The electromagnetic field finite element software can simulate the electromagnetic characteristics of the current transformer under different working conditions. Through the simulation results, the performance of the current transformer can be comprehensively evaluated. Furthermore, the design parameters of the current transformer can be adjusted in a targeted manner, greatly improving the accuracy and reliability of the current transformer design.

[0152] In one embodiment, based on the above embodiment, the three-dimensional geometric model in step S501 includes: a primary conductor of the current transformer, a first iron core of the current transformer, a secondary iron core of the current transformer, a secondary winding of the current transformer and an insulation structure of the current transformer.

[0153] Specifically, the primary conductor of the current transformer is the wire on the primary side of the current transformer, the secondary conductor of the current transformer is the output wire of the current transformer, and the insulation structure of the current transformer is a solid insulating material used to isolate the primary conductor, the secondary winding and the iron core.

[0154] In this embodiment, the three-dimensional geometric model includes various components of the current transformer, can accurately reproduce the actual structure of the current transformer, and can more accurately simulate the electromagnetic field distribution of the transformer in a real working environment.

[0155] In one embodiment, Figure 6 Another schematic flow chart of a simulation verification method for a DC bias-resistant dual-core current transformer according to an embodiment of the present application is shown. Based on the above embodiment, step S503 includes:

[0156] Step S601: setting boundary conditions of the current transformer in the transient magnetic field module of the electromagnetic field finite element software.

[0157] Exemplarily, the electromagnetic field finite element software is ANSYS Maxwell. After the three-dimensional geometric model is imported, the electromagnetic field finite element software can first define the materials of each module in the model.

[0158] It can be set according to the actual application situation, and can be set as a symmetric surface boundary condition or a far-field boundary condition.

[0159] Step S602: Divide the grid of the three-dimensional geometric model.

[0160] Specifically, adaptive meshing may be performed, or manual meshing may be performed. Exemplarily, adaptive meshing is performed first, and then manual refinement is performed.

[0161] Step S603: setting time-varying excitation, coil parameters and core magnetization curve.

[0162] Specifically, the excitation is set to a sinusoidal DC bias or a sinusoidal half wave, the coil parameters are set to be connected to the load, the iron core is selected, and the magnetization curve is set.

[0163] Step S604: defining the resistive and inductive loads of the current transformer in the circuit module of the electromagnetic field finite element software.

[0164] Add resistance or inductance elements to the circuit module to represent the secondary side load of the current transformer, i.e. the load.

[0165] Step S605: two inductance elements are arranged in the circuit module, and the two inductance elements are connected to the relevant circuit.

[0166] Two inductance elements are added to the circuit module, representing the equivalent inductance of the first iron core and the second iron core respectively. The two inductance elements are connected in series and in parallel with the secondary side load.

[0167] Step S606: Set simulation parameters and run the simulation.

[0168] According to the actual application situation, a suitable solution step size and solution time range are set in the solver. Demonstratively, the solver is a transient field-circuit coupling solver, and the parametric scan is set according to different proportions of the rated current. Demonstratively, the different proportions of the rated current are 1%, 2%, 5%, 10%, 20%, 50%, 100%, 120% and 150%.

[0169] In this embodiment, by setting the boundary conditions, grid division, time-varying excitation, coil parameters and core magnetization curve of the current transformer, and setting parameterized scanning according to different proportions of the rated current, the performance of the current transformer can be systematically analyzed and optimized, providing a reliable theoretical basis and technical support for its design, manufacture and use.

[0170] The present application also provides a DC bias resistant double-core current transformer. Figure 7A schematic diagram of the winding of a first coil and a second coil on a double core of a double core current transformer resistant to DC bias is shown in an embodiment of the present application. By way of example, the double core current transformer resistant to DC bias is obtained by the above-mentioned preparation method, wherein the double core current transformer resistant to DC bias comprises: a first core 10 and a second core 20, an air gap 101 is provided at a preset position of the first core 10, and the length of the air gap 101 is determined according to the electrical performance index of the current transformer, a first coil 102 is wound on the first core 10, a second coil 201 is wound on the second core 20, the first coil 102 and the second coil 201 are connected in series, and the first core 10 and the second core 20 are stacked along a preset direction.

[0171] It is understandable that the preset direction is the thickness direction of the core. The size parameters and materials of the first core 10 and the second core 20 can be set according to the actual application. The materials of the first core 10 and the second core 20 can be the same, or the materials of the first core 10 and the second core 20 can be different. Exemplarily, the first core 10 is a silicon steel core, and the second core 20 is an alloy core.

[0172] The size of the air gap 101 can be directly calculated according to the electrical performance index of the current transformer, or an initial size of the air gap 101 can be selected first, and then the influence of the air gap 101 on the electrical performance index is confirmed by calculation, and the initial size of the air gap 101 is adjusted according to the influence to meet the requirements of the electrical performance index of the current transformer.

[0173] The preset position of the first iron core 10 can be set according to the actual application situation. Two air gaps 101 can be set on the first iron core 10, and the size of each of the two air gaps 101 is half of the total air gap size. Four air gaps 101 can also be set on the first iron core 10, and the size of each of the four air gaps 101 is one quarter of the total air gap size. Exemplarily, two air gaps 101 are set on the first iron core 10.

[0174] Specifically, the first coil 102 includes a primary side coil wound around the first iron core 10 and a secondary side coil wound around the first iron core, the second coil 201 includes a primary side coil wound around the second iron core and a secondary side coil wound around the second iron core, the primary side coil of the first iron core 10 and the primary side coil of the second iron core 20 are connected in series, and the secondary side coil of the first iron core 10 and the secondary side coil of the second iron core 20 are connected in series, and the length of the coil can be set according to actual application conditions.

[0175] The DC bias resistant double-core current transformer of the embodiment of the present embodiment is a double-core type, and an air gap 101 is provided on one of the cores. The air gap 101 is utilized to prevent magnetic saturation of the core, thereby improving the linear operating current range of the current transformer. The size of the air gap 101 is determined according to the electrical performance index of the current transformer. By optimizing the size of the air gap 101, the error of the transformer in the transient process can be reduced, thereby improving the accuracy and reliability of the measurement.

[0176] In several embodiments provided in the present application, it should be understood that the disclosed devices and methods can also be implemented in other ways. The device embodiments described above are merely schematic. For example, the flowcharts and structure diagrams in the accompanying drawings show the possible architecture, functions and operations of the devices, methods and computer program products according to multiple embodiments of the present application. In this regard, each box in the flowchart or block diagram can represent a module, a program segment or a part of a code, and the module, a program segment or a part of a code contains one or more executable instructions for implementing the specified logical function. It should also be noted that in an alternative implementation, the functions marked in the box can also occur in a different order from the order marked in the accompanying drawings. For example, two consecutive boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the structure diagram and / or the flow diagram, and the combination of boxes in the structure diagram and / or the flow diagram, can be implemented with a dedicated hardware-based system that performs a specified function or action, or can be implemented with a combination of dedicated hardware and computer instructions.

[0177] In addition, the functional modules or units in the various embodiments of the present application may be integrated together to form an independent part, or each module may exist separately, or two or more modules may be integrated to form an independent part.

[0178] If the functions are implemented in the form of software function modules and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for a computer device (which can be a smart phone, a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in the various embodiments of the present application.

[0179] The above description is only a specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application.

Claims

1. A method for preparing a double-core current transformer with DC bias resistance, characterized in that: include: Determine the size parameters of the double core to obtain a first core and a second core; Determining the size of the air gap according to the electrical performance index of the current transformer, and setting the air gap at a preset position of the first iron core; Winding a first coil on the first iron core provided with the air gap, winding a second coil on the second iron core, and connecting the first coil and the second coil in series; The first iron core and the second iron core are stacked along a preset direction.

2. The method for preparing the DC bias resistant double-core current transformer according to claim 1, characterized in that: Determining the air gap size according to the electrical performance index of the current transformer comprises: Selecting the initial air gap size according to the preset ratio of the equivalent length of the magnetic circuit of the core; Calculating the initial DC magnetic bias current and the initial sinusoidal half-wave current of the double-core current transformer after the core is gapped according to the selected initial air gap size; If the initial DC bias current is not within the preset bias current range and / or the initial sinusoidal half-wave current is not within the preset half-wave current range, increasing the air gap size; Calculate the current DC magnetic bias current and the current half-sine wave current according to the increased air gap size; If the current DC bias current is not within the preset bias current range and / or the current sinusoidal half-wave current is not within the preset half-wave current range, increase the air gap size again until the newly increased air gap size satisfies the corresponding calculated DC bias current within the preset bias current range and / or the sinusoidal half-wave current within the preset half-wave current range.

3. The method for preparing the DC bias resistant double-core current transformer according to claim 2, characterized in that: After determining the air gap size according to the electrical performance index of the current transformer, the preparation method further comprises: Calculating the error, phase angle difference and ratio difference of the double-core current transformer after the core is air-gapped according to the newly increased air gap size; After stacking the first iron core and the second iron core along a preset direction, the preparation method further includes: The phase angle difference and ratio difference of the current transformer are tested by using a testing device.

4. The method for preparing a DC bias resistant double-core current transformer according to claim 1, characterized in that: Determining the size parameters of the dual core to obtain the first core and the second core includes: Obtaining a minimum cross-sectional area of ​​the first core according to electrical performance requirements of the current transformer; Determining a cross-sectional area of ​​the first core according to the minimum cross-sectional area and a space size limitation of the current transformer; The minimum cross-sectional area is obtained by the following formula: Where: k 2z represents the winding impedance coefficient of the first core, I 2n Represents the rated secondary current of the current transformer; Z 2n represents the rated secondary load of the current transformer; f represents the rated operating frequency of the current transformer; N2 represents the number of turns of the secondary winding of the current transformer; B n represents the rated magnetic flux density of the first core.

5. The method for preparing the DC bias resistant double-core current transformer according to claim 2, characterized in that: The half-sine wave current is obtained by the following formula: Where: I hw I represents the half-wave sinusoidal current of the current transformer; dc represents the DC magnetic bias current of the current transformer; The DC bias current is obtained by the following formula: Where: H am represents the saturation magnetic field intensity of the first iron core after the air gap is opened; N1 represents the number of turns of the secondary winding of the current transformer; l a represents the equivalent length of the magnetic circuit of the first core; The saturation magnetic field intensity of the first core after the air gap is opened is obtained by the following formula: Among them: B m represents the saturation magnetic field density of the first core; μ a represents the equivalent relative magnetic permeability of the first core after the air gap is opened; μ0 represents the magnetic permeability of air; The equivalent relative magnetic permeability of the first iron core after the air gap is opened is obtained by the following formula: Where: μ Fe represents the relative magnetic permeability of the first core; l g represents the initial air gap size.

6. The method for preparing the DC bias resistant double-core current transformer according to claim 3, characterized in that: The error of the current transformer is obtained by the following formula: Where: i represents the error of the current transformer; Z 2n Represents the rated secondary load of the current transformer; Z 2r represents the secondary winding impedance of the current transformer, j represents the phase difference; ω represents the rated angular frequency; N2 represents the number of turns of the secondary winding of the current transformer; μ a represents the equivalent relative magnetic permeability of the first core after the air gap is opened; μ0 represents the magnetic permeability of air; S a represents the cross-sectional area of ​​the first core; S c represents the cross-sectional area of ​​the second core; l a represents the equivalent length of the magnetic circuit of the first core; l c represents the equivalent length of the magnetic circuit of the second core; The ratio difference and the phase angle difference are obtained by the following formula: Wherein: ξ represents the ratio difference of the current transformer; α represents the impedance angle between the secondary winding of the current transformer and the load; θ represents the iron loss angle of the current transformer; δ represents the phase angle difference of the current transformer.

7. A simulation verification method for a DC bias-resistant double-core current transformer, characterized in that: After obtaining the DC bias resistant double-core current transformer by the preparation method according to any one of claims 1 to 6, simulation verification is performed on the DC bias resistant double-core current transformer, including: Constructing a three-dimensional geometric model of the current transformer; Importing the three-dimensional geometric model into electromagnetic field finite element software; Based on the relevant configuration parameters in the electromagnetic field finite element software, simulation verification is carried out.

8. The simulation verification method of the DC bias-resistant double-core current transformer according to claim 7, characterized in that: The three-dimensional geometric model includes: a primary conductor of the current transformer, a first iron core of the current transformer, a secondary iron core of the current transformer, a secondary winding of the current transformer and an insulation structure of the current transformer.

9. The simulation verification method of the DC bias-resistant double-core current transformer according to claim 7, characterized in that: Based on the relevant configuration parameters in the electromagnetic field finite element software, the simulation verification includes: Setting the boundary conditions of the current transformer in the transient magnetic field module of the electromagnetic field finite element software; Dividing the grid of the three-dimensional geometric model; Set up time-varying excitation, coil parameters, and core magnetization curve; Defining the resistive and inductive loads of the current transformer in the circuit module of the electromagnetic field finite element software; Arranging two inductance elements in the circuit module, and connecting the two inductance elements to the relevant circuit; Set simulation parameters and run the simulation.

10. A DC bias resistant double core current transformer, characterized in that: The DC bias-resistant double-core current transformer is obtained by the preparation method described in any one of claims 1 to 6; Among them, the DC bias-resistant double-core current transformer includes: a first core and a second core, an air gap is arranged at a preset position of the first core, the length of the air gap is determined according to the electrical performance index of the current transformer, a first coil is wound on the first core, a second coil is wound on the second core, the first coil is connected in series with the second coil, and the first core and the second core are stacked along a preset direction.

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