CN114864251A - Double-framework common-winding current transformer structure and design method thereof - Google Patents
Double-framework common-winding current transformer structure and design method thereof Download PDFInfo
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Abstract
The current transformer structure comprises an ultra-microcrystalline iron core and a silicon steel sheet iron core, wherein the ultra-microcrystalline iron core is a closed iron core, and an air gap is formed in the silicon steel sheet iron core. In the structural design of the current transformer, when the excitation current and the iron core error are solved, the two conditions of the closed iron core and the air gap iron core are respectively solved. This current transformer adopts the design of two iron core frameworks, wherein the air gap has been opened to the iron core of mainly used protection, can effectively avoid the adverse effect that the protection brought, can realize measurement function when the undercurrent, when electric power system breaks down and has great current, the closed iron core of measuring usefulness reaches the saturation, the electric current flows through from the air gap iron core, because the magnetic resistance of air gap iron core will be far more than closed iron core magnetic resistance, can not have the saturation phenomenon under the heavy current condition, so can realize the monitoring of heavy current, in order to reach the effect of protection.
Description
Technical Field
The invention belongs to the technical field of current transformers, and particularly relates to a double-framework common-winding current transformer structure and a design method thereof.
Background
The current transformer is an important device for power measurement, fault diagnosis and power system state monitoring, and is widely applied to substations and power plants. The iron core structure of the traditional current transformer generally adopts a closed-loop design, the design enables the iron core to have only extremely small magnetic impedance, when a large current component appears on a primary side, the iron core is easy to saturate, and for the current transformer for measurement, the iron core saturation can cause the current transformer to have measurement errors; for a current transformer for protection, the iron core is saturated to make the current transformer lose the protection margin, so that when a power system fails, the current transformer cannot monitor and identify large current and loses the protection effect. And the existing closed iron core material for measurement is easy to saturate, and the problems of large occupied area and high cost exist in independent installation for measurement and protection. Such as: in the traditional closed iron core material, a magnetic circuit formed in a loop has very small magnetic impedance, and when a large current appears on the primary side of a transformer, very high direct current magnetic flux is formed in the closed magnetic circuit, so that a BH working point in an iron core moves from a linear working area to a saturation area to reach saturation.
In recent decades, intellectualization and miniaturization gradually become the new development characteristics of the automation technology of the power system, the traditional current sensor is often separately and independently installed according to functions, two windings and two coils are adopted to realize the functions, and the defects of high cost, large volume, poor transient characteristics, small dynamic range and the like exist, so that the traditional independent sensor is difficult to meet the requirement of further development of the power system.
Disclosure of Invention
In order to solve the technical problems, the invention provides a double-framework common-winding current transformer structure and a design method thereof, the invention combines the characteristics of high precision and saturation resistance of a protection type current transformer of the traditional measurement type current transformer, designs a double-framework common-winding technology of the current transformer based on ultracrystalline and notched silicon steel sheets, and can increase excitation shunt by respectively calculating double-iron-core magnetic resistance and verifying that the air gap magnetic resistance is far greater than the closed iron-core magnetic resistance, and the technology can effectively reduce measurement errors. Meanwhile, the design method analyzes the electromagnetic characteristics of the iron core coil under different currents, optimizes the proportion and the thickness of the framework, respectively calculates the ratio difference and the angle difference of the iron core coil when the height of the framework changes, determines the optimal proportion of the framework by combining the actual production and the size of the iron core, and replaces the traditional air gap fit based on the ultra-microcrystal, thereby improving the anti-saturation point.
The technical scheme adopted by the invention is as follows:
the double-framework common-winding current transformer structure comprises an ultracrystalline iron core and a silicon steel sheet iron core, wherein the ultracrystalline iron core is a closed iron core, and an air gap is formed in the silicon steel sheet iron core.
The ultra-microcrystalline iron core and the silicon steel sheet iron core are stacked together.
The inner and outer radiuses of the ultracrystalline iron core and the silicon steel sheet iron core are consistent.
The height of the ultracrystalline iron core is h1, the height of the silicon steel sheet iron core is h2, and the length of the air gap is L δ 。
The structural design method of the double-framework common-winding current transformer comprises the following steps:
step 1: determining the size of the magnetic resistance Rm according to the sizes of the ultracrystalline iron core and the silicon steel sheet iron core and the magnetic conductivity;
step 2: the height of the ultra-microcrystalline iron core is h1, the height of the silicon steel sheet iron core is h2, and when the calculated height of h1 and h2 is respectively changed within 1-10mm, the double-iron-core coil error is detected.
The step2 comprises the following steps:
step1, calculating the sectional area of the iron core, the average magnetic path length and the average turn length according to the size of the iron core;
obtaining the sectional area of the iron core:
wherein S1 represents the sectional area of the ultracrystalline core, D 1 Is an ultra-microcrystalline core outer diameter, d 1 Is the inner diameter h of the ultra-microcrystalline iron core 1 Is ultra-microcrystalline iron core height, K H1 The lamination coefficient of the ultracrystalline iron core is shown;
S 2 showing the sectional area of the core of silicon steel sheet, D 2 Is the outer diameter of the silicon steel sheet iron core, d 2 Is the inner diameter h of a silicon steel sheet iron core 2 Is the height of the silicon steel sheet iron core, K H2 The lamination coefficient of the silicon steel sheet iron core;
average magnetic path length L c ：
D is the outer diameter of the double iron cores, and D is the inner diameter of the double iron cores;
calculating the average turn length l co ：
Wherein D is the outer diameter of the double iron cores, D is the inner diameter of the double iron cores, and H is the total height of the double iron cores.
Step2, determining the length of the lead according to the average turn length and the number of turns of the secondary winding, calculating the sectional area of the lead according to the diameter of the lead, and further solving the resistance of the lead;
length of wire L:
L＝l co ×N 2 ；
wherein N is 2 The number of secondary winding turns.
Cross section area S of wire L ：
Wherein phi is Guide rail Is the wire diameter.
Wire resistance:
where ρ is 0.02(Ω imm) 2 )/m；
Step3, calculating secondary current according to the relation between the current ratio and the turn ratio, and further calculating the sum of secondary induced electromotive force by combining secondary impedance;
secondary current I 2 ：
Wherein, I 1 Is a primary current, N 1 Is at a timeNumber of turns, N 2 The number of turns is two times;
secondary induced electromotive force E 2 ：
E 2 ＝Z 2 ×I 2 ；
Wherein, Z 2 Is the total impedance of the secondary coil, E 2 For secondary induced electromotive force, I 2 Is a secondary current, S 1 Is an ultra-microcrystalline core cross-sectional area, N 2 For the second order turns, f is the frequency 50 hz. B is m The magnetic flux density is shown.
Step4, because the two iron core materials are different, the magnetization curve (B-H curve) and the loss angle curve (H-phi curve) are different, and the unit length excitation magnetic potential H and the loss angle phi obtained by table lookup are different. Therefore, when the excitation current and the iron core error are solved, the two conditions of the closed iron core and the air gap iron core are required to be solved respectively;
the table lookup is based on the above B m Firstly, looking up a data table of corresponding curves according to a magnetization curve (B-H curve) of an iron core material to obtain a value B of a unit length excitation magnetic potential H corresponding to Bm, wherein each B corresponds to one H; and secondly, checking a data table of a corresponding curve according to the loss angle curve (H-phi curve), wherein each B corresponds to one H, and obtaining the loss angle phi value corresponding to the H value.
a. Solving the excitation current and the iron core error by closing the iron core;
calculating the exciting current I 01 ：
I 01 ＝K F ×H×L c ；
K F The process coefficient is generally 1 to 1.1.
Calculating a core error, comprising:
the ratio difference is as follows:
the angular difference is as follows:
where α is the secondary coil impedance angle.
3438' refers to: the unit of angular difference is converted, radian is made into angle, the formula is radian, the radian is made into angle, x 180 ÷ pi is needed for radian making into angle, the angular difference is expressed by ' here, the relation between degree and minute ' is that one degree is equal to 60 minutes ', namely the angular difference is divided, and also x 60 is needed on the basis of x 180 ÷ pi, the calculator is used for calculating 3437.749, and the rounding is 3438.
b. Solving the exciting current and the iron core error by the air gap iron core:
air gap core exciting current:
I 02 ＝K F ×H×L c
wherein, K F Generally 1.1-1.2, here 1.1.
Calculating the active component and the reactive component of the exciting current:
the flux density of the air-gap portion is equal to that of the non-air-gap portion of the core, and therefore, the magnetic field strength of the air-gap portion:
H a denotes the magnetic field strength of the air gap portion, B m Denotes the magnetic flux density, μ, of the air gap portion a Shows the permeability of the air gap portion, also the vacuum permeability μ 0 ，L a Indicating the air gap length.
The excitation current of the air gap portion can be considered as a reactive component.
I 0eq,re ＝I 02,re
I 0eq,im ＝I 02,im +I 02 ′
I 0eq,re Representing the active component of the exciting current after the equivalent of the iron core with the air gap;
I 0eq,im representing the equivalent exciting current reactive component of the iron core with air gap;
I 0eq representing the equivalent exciting current of the iron core with the air gap;
Calculating a core error, comprising:
the ratio difference is as follows:
f L2 representing the ratio difference of the air gap iron core;
I 0eq representing the equivalent exciting current of the iron core with the air gap;
alpha is the secondary coil impedance angle;
I 1 representing the primary current.
The angular difference is as follows:
where α is the secondary coil impedance angle.
δ 2 Representing the angular difference of the air gap core;
I 0eq representing the equivalent exciting current of the iron core with the air gap;
alpha is the secondary coil impedance angle;
I 1 representing the primary current.
The invention discloses a double-framework common-winding current transformer structure and a design method thereof, and the technical effects are as follows:
1) the current transformer adopts a double-iron-core framework design, wherein the silicon steel sheet iron core mainly used for protection is provided with an air gap, so that the adverse effect caused by protection can be effectively avoided, the measurement function can be realized at the time of small current, when a power system has a fault and has larger current, the ultracrystalline iron core for measurement is saturated, the current flows through the air gap iron core, and as the magnetic resistance of the air gap iron core is far greater than that of a closed iron core, the saturation phenomenon can not occur under the condition of large current, the large current monitoring can be realized, so that the protection effect can be achieved.
2) The ultra-microcrystalline alloy of the ultra-microcrystalline iron core has the characteristics of low current and high permeability, and the cut silicon steel sheet of the silicon steel sheet iron core has the characteristic of large current and difficulty in saturation; the silicon steel sheet iron core has strong anti-saturation capacity, and the cut silicon steel sheet with the air gap has strong anti-saturation capacity, so that the loss of action in the case of heavy current can be avoided. The device can simultaneously meet the measurement requirement under the condition of small current and the protection requirement under the condition of high current when a fault occurs, so that the precision is higher.
3) The invention provides a structural design method of a double-framework common-winding current transformer. The proportion relation of double framework materials is optimally designed, the advantages of the two materials are complementary, the electromagnetic characteristics of the materials under different currents are analyzed, the framework proportion and the thickness are optimized, the proportion difference and the angle difference of an iron core coil when the height of the framework changes are respectively calculated, the optimal framework proportion is determined by combining actual production and the size of the iron core, and the traditional air gap conjunction is replaced on the basis of ultracrystallite, so that the anti-saturation point is improved.
4) The invention adopts theoretical analysis calculation to model the current transformer, carries out structural optimization on the designed model through analysis and comparison, verifies that the air gap magnetic resistance is far greater than the closed iron core magnetic resistance through respectively calculating the double-framework iron core magnetic resistance, increases excitation shunting, reduces measurement errors, effectively saves cost and improves the micro-measurement design.
5) The invention provides a current transformer framework structure based on an ultracrystalline and silicon steel sheet dual material for the first time. The method is characterized in that a fusion model of the ultra-microcrystalline alloy low-current high-permeability characteristic and the silicon steel sheet high-current non-saturation characteristic is established, a bi-material framework structure which simultaneously meets the measurement requirements and protection application is designed, when a small current passes through an iron core winding, the technology implements a small-current measurement function corresponding to a closed iron core, and when a fault large current passes through the iron core winding, the technology implements a protection function of high-current anti-saturation capacity corresponding to an air gap iron core, so that the measurement error can be reduced, and the equipment reliability can be improved. Through theoretical analysis and calculation, the measurement precision can reach the 0.2-level requirement, and the actual precision is higher.
Drawings
Fig. 1 is a schematic structural diagram of a double-framework common-winding current transformer.
Fig. 2 is a schematic diagram of an air gap core.
FIG. 3(1) is a graph of closed core ratio difference versus height;
fig. 3(2) is a graph of closed core angle difference versus height.
FIG. 4(1) is a graph of air gap core ratio difference as a function of height;
fig. 4(2) is a graph of air gap core angle difference versus height.
Fig. 5(1) is a graph showing that when h2 is 1mm, the iron core comprehensive ratio difference changes with h 1;
fig. 5(2) is a graph showing that when h2 is 2mm, the iron core comprehensive ratio difference changes with h 1;
fig. 5(3) is a graph showing that when h2 is 3mm, the iron core comprehensive ratio difference changes with h 1;
fig. 5(4) is a graph showing that when h2 is 4mm, the iron core comprehensive ratio difference changes with h 1;
fig. 5(5) is a graph showing that when h2 is 5mm, the iron core comprehensive ratio difference changes with h 1;
fig. 5(6) is a graph in which the iron core comprehensive ratio difference changes with h1 when h2 is 6 mm;
fig. 5(7) is a graph showing that when h2 is 7mm, the iron core comprehensive ratio difference changes with h 1;
fig. 5(8) is a graph in which the iron core comprehensive ratio difference changes with h1 when h2 is 8 mm;
fig. 5(9) is a graph in which the iron core comprehensive ratio difference changes with h1 when h2 is 9 mm;
fig. 5(10) is a graph showing that when h2 is 10mm, the iron core comprehensive ratio difference changes with h 1.
Fig. 6(1) is a graph showing that when h1 is 1mm, the iron core comprehensive ratio difference changes with h 2;
fig. 6(2) is a graph showing that when h1 is 2mm, the iron core comprehensive ratio difference changes with h 2;
fig. 6(3) is a graph showing that when h1 is 3mm, the iron core comprehensive ratio difference changes with h 2;
fig. 6(4) is a graph showing that when h1 is 4mm, the iron core comprehensive ratio difference changes with h 2;
fig. 6(5) is a graph showing that when h1 is 5mm, the iron core comprehensive ratio difference changes with h 2;
fig. 6(6) is a graph showing that when h1 is 6mm, the iron core comprehensive ratio difference changes with h 2;
fig. 6(7) is a graph showing that when h1 is 7mm, the iron core comprehensive ratio difference changes with h 2;
fig. 6(8) is a graph showing that when h1 is 8mm, the iron core comprehensive ratio difference changes with h 2;
fig. 6(9) is a graph showing that when h1 is 9mm, the iron core comprehensive ratio difference changes with h 2;
fig. 6(10) is a graph showing that when h1 is 10mm, the iron core comprehensive ratio difference changes with h 2.
Fig. 7(1) is a graph showing that when h2 is 1mm, the iron core comprehensive angle difference changes with h 1;
fig. 7(2) is a graph showing that when h2 is 2mm, the iron core comprehensive angle difference changes with h 1;
fig. 7(3) is a graph showing that when h2 is 3mm, the iron core comprehensive angle difference changes with h 1;
fig. 7(4) is a graph showing that the iron core comprehensive angle difference changes with h1 when h2 is 4 mm;
fig. 7(5) is a graph showing that when h2 is 5mm, the iron core comprehensive angle difference changes with h 1;
fig. 7(6) is a graph showing that when h2 is 6mm, the iron core comprehensive angle difference changes with h 1;
fig. 7(7) is a graph showing that when h2 is 7mm, the iron core comprehensive angle difference changes with h 1;
fig. 7(8) is a graph showing that when h2 is 8mm, the iron core comprehensive angle difference changes with h 1;
fig. 7(9) is a graph showing that when h2 is 9mm, the iron core comprehensive angle difference changes with h 1;
fig. 7(10) is a graph showing the variation of the core angle integral difference with h1 when h2 is 10 mm.
Fig. 8(1) is a graph showing that when h1 is 1mm, the iron core comprehensive ratio difference changes with h 2;
fig. 8(2) is a graph showing that when h1 is 2mm, the iron core comprehensive ratio difference changes with h 2;
fig. 8(3) is a graph showing that when h1 is 3mm, the iron core comprehensive ratio difference changes with h 2;
fig. 8(4) is a graph showing that when h1 is 4mm, the iron core comprehensive ratio difference changes with h 2;
fig. 8(5) is a graph showing that when h1 is 5mm, the iron core comprehensive ratio difference changes with h 2;
fig. 8(6) is a graph showing that when h1 is 6mm, the iron core comprehensive ratio difference changes with h 2;
fig. 8(7) is a graph showing that when h1 is 7mm, the iron core comprehensive ratio difference changes with h 2;
fig. 8(8) is a graph showing that when h1 is 8mm, the iron core comprehensive ratio difference changes with h 2;
fig. 8(9) is a graph showing that when h1 is 9mm, the iron core comprehensive ratio difference changes with h 2;
fig. 8(10) is a graph showing that when h1 is 10mm, the iron core total ratio difference changes with h 2.
Detailed Description
The invention is described in further detail below with reference to the accompanying drawings:
the double-framework common-winding current transformer structure comprises an ultra-microcrystalline iron core 1 and a silicon steel sheet iron core 2, wherein the ultra-microcrystalline iron core 1 is a closed iron core, and an air gap 3 is formed in the silicon steel sheet iron core 2.
The layout of the ultra-microcrystalline iron core 1 and the silicon steel sheet iron core 2 is that the ultra-microcrystalline iron core and the silicon steel sheet iron core are stacked together in parallel from top to bottom.
The inner and outer radiuses of the ultracrystalline iron core 1 and the silicon steel sheet iron core 2 are consistent. When the windings are wound together, the redundant edge magnetic flux can be prevented from being generated, and the performance of the current transformer is influenced.
The height of the ultra-microcrystalline iron core 1 is h1, the height of the silicon steel sheet iron core 2 is h2, and the length of the air gap 3 is L δ The schematic diagram of the air gap structure is shown in fig. 2.
According to the magnetic field distribution of the silicon steel sheet framework of the silicon steel sheet iron core 2, the measurement error can be reduced by adopting the multi-layer co-winding technology of the notch edge.
Regarding the magnetic field distribution of the silicon steel sheet skeleton, as can be seen from the schematic diagram of the air-gap iron core shown in fig. 2, the magnetic path of the silicon steel sheet iron core 2 is schematically illustrated, and the magnetic path length is divided into an air-gap portion L air And a non-air gap portion length L iron The magnetic field distribution and the appearance of the closed iron core at the air gap part are different, and the magnetic field cannot be seen by naked eyes even when the closed iron core is electrified, so the specific distribution cannot be drawn by hands. It can only be theoretically analyzed that the presence of an air gap can change the uniform distribution of the original closed-loop magnetic field, and fringing magnetic flux can exist around the air gap magnetic field, which can be described as the magnetic field distribution at the air gap is no longer uniform.
Regarding the notch edge multi-layer co-winding technology, when winding is performed, two iron cores are co-wound, that is, one winding is used to wind 2 layers of iron cores, the technology of co-winding two iron cores inside the structure is described, and the technology of co-winding iron cores can also be directly described.
The double-framework refers to an iron core of the current transformer, which is composed of 2 iron cores made of different materials, namely the double iron core.
The common winding means that the structure of the current transformer designed by the invention is that two materials jointly form the iron core of the transformer, and the same winding is wound on the double frameworks of the iron core, so that the iron cores made of the two materials structurally have the common winding, and the common winding is combined and called as the common winding in the invention.
The closed iron core of the invention refers to an ultra-microcrystalline iron core 1; the air gap iron core of the invention refers to a silicon steel sheet iron core 2.
The structural design of the double-framework common-winding current transformer comprises the following steps of:
1) determining the size of the magnetic resistance Rm according to the size of the iron core and the magnetic conductivity:
the initial permeability of the materials selected for the double iron cores are different, the requirement of the initial permeability of the ultracrystalline material used for the closed iron core is more than 8000, the requirement of the initial permeability of the silicon steel sheet material used for the air-gap iron core is more than 7000, and when the magnetic resistance Rm1 and the magnetic resistance Rm2 of the double iron cores are respectively calculated, the initial permeability mu of the iron core materials is calculated r1 8000 and μ r2 The calculation is performed 7000. The closed iron core magnetic resistance Rm1 is 178k omega, and the closed iron core magnetic resistance Rm2 is 2116k omega. According to the two numerical values, the magnetic resistance of the air gap iron core is far greater than that of the closed iron core, so that the excitation shunt can be increased, and the measurement error is reduced.
2) Calculating the height h1 of the iron core: h2 ═ 1: and 5, the calculation method of the error of current shunt is as follows:
firstly, calculating the sectional area of an iron core:
wherein S1 represents the sectional area of the ultracrystalline core, D 1 Is an ultra-microcrystalline core outer diameter, d 1 Is the inner diameter h of the ultra-microcrystalline iron core 1 Is ultra-microcrystalline core height, K H1 The lamination coefficient of the ultracrystalline iron core is shown;
S 2 showing the sectional area of the core of silicon steel sheet, D 2 Is the outer diameter of the silicon steel sheet iron core, d 2 Inner diameter of iron core made of silicon steel sheet h 2 Is the height of the silicon steel sheet iron core, K H2 The lamination coefficient of the silicon steel sheet iron core;
secondly, calculating the average magnetic path length Lc:
d is the outer diameter of the iron core, and D is the inner diameter of the iron core;
thirdly, calculating the average turn length l co ：
Wherein D is the iron core external diameter, D is the iron core internal diameter, and H is two iron core overall heights.
Length of wire L:
L＝l co ×N 2
wherein l co Is the average turn length, N 2 The number of secondary winding turns.
Cross section area S of wire L ：
Wherein phi is Guide tube Is the wire diameter.
Wire resistance:
where ρ is 0.02(Ω · mm) 2 ) (ii)/m; rho is the wire resistivity and is determined according to the material, the secondary wire in the structural design of the invention is a copper wire, and the wire resistivity of copper at normal temperature is 0.02 (omega mm) 2 )/m。
Fourthly, calculating secondary current I 2 ：
Wherein, I 1 Is a primary current, N 1 Number of turns at one time, N 2 The number of turns is twice;
the design is based on a small current transformer with a primary side current of 1A or 5A, the secondary side current is in mA level, the secondary turn number of the mA level current transformer is not lower than 1000 turns and not higher than 3000 turns, in order to ensure that the designed current transformer has good performance, the secondary current is as small as possible, the secondary turn number is as large as possible, theoretical analysis is combined with actual production, continuous debugging is carried out during manufacturing, and the secondary turn number is finally selected to be 2850.
Fifthly, calculating secondary induced electromotive force E 2 ：
E 2 ＝Z 2 ×I 2 ；
Wherein Z is 2 Is the total impedance of the secondary coil, E 2 For secondary induced electromotive force, I 2 Is a secondary current, S 1 Is an ultra-microcrystalline core cross-sectional area, N 2 For the second order turns, f is the frequency 50 hz.
According to the magnetization curve and loss angle curve of iron core finding out excitation magnetic potential H and loss angle of unit length
Because the two iron cores are made of different materials and have different magnetization curves and different loss angle curves, the unit length excitation magnetic potential H and the loss angle obtained by looking up the table are different
Different. Therefore, when the excitation current and the iron core error are solved, the two conditions of the closed iron core and the air gap iron core are required to be solved respectively.
a. Closed iron core exciting current:
sixthly, calculating the exciting current I 01 ：
I 01 ＝K F ×H×L c ；
And seventhly, calculating the error of the iron core:
the ratio difference is as follows:
the angular difference is as follows:
where α is the secondary coil impedance angle.
b. Air gap core exciting current:
I 02 ＝K F ×H×L c ；
wherein, K F Generally 1.1-1.2, here 1.1.
Calculating the active component and the reactive component of the exciting current:
the flux density of the air-gap portion is equal to that of the non-air-gap portion of the core, and therefore, the magnetic field strength of the air-gap portion:
the excitation current of the air gap portion can be considered as a reactive component.
And eighthly, calculating an iron core error:
the ratio difference is as follows:
the angular difference is as follows:
where α is the secondary coil impedance angle.
According to the calculation process, the specific difference angle difference data of the closed iron core and the air gap iron core can be respectively calculated.
(1) When the height h1 of the closed iron core (ultra-microcrystal) is changed from 1mm to 10mm, the ratio difference and angle difference data obtained according to the calculation steps are shown in the following table 1.
TABLE 1 closed core error calculation
| h1(mm) | B(T) | H(A/cm) | Φ(°) | Specific difference f L1 (％) | Angular difference delta 1 (’) |
| 1 | 0.2236 | 0.0194 | 36.01 | -0.02 | 0.618 |
| 2 | 0.112 | 0.0093 | 42.65 | -0.01 | 0.256 |
| 3 | 0.11 | 0.0062 | 36.79 | -0.0064 | 0.194 |
| 4 | 0.056 | 0.0047 | 27.12 | -0.004 | 0.174 |
| 5 | 0.044 | 0.0037 | 13.84 | -0.002 | 0.158 |
| 6 | 0.037 | 0.0031 | 12.79 | -0.0018 | 0.134 |
| 7 | 0.032 | 0.0027 | 9.48 | -0.0014 | 0.12 |
| 8 | 0.028 | 0.0023 | 7.44 | -0.0011 | 0.103 |
| 9 | 0.025 | 0.0021 | 5.71 | -0.0009 | 0.095 |
| 10 | 0.022 | 0.0018 | 4.35 | -0.0007 | 0.082 |
According to the calculation steps, firstly, the exciting current of the closed iron core is calculated, and then the calculated exciting current value is substituted into the specific difference f of the closed iron core L1 Angle difference delta of sum 1 The numerical value is calculated by the formula (2). F of closed iron core when h1 is changed within 1-10mm L1 And delta 1 The relationship with h1 is shown in FIG. 3(1) and FIG. 3 (2). As shown in FIGS. 3(1) and 3(2), after h1 > 5mm, f L1 And delta 1 The rate of decrease gradually moderates.
(2) When the height h2 of the air gap iron core (cut silicon steel sheet) is changed from 1mm to 10mm, the data of the ratio difference and the angle difference obtained according to the calculation steps are shown in table 2.
TABLE 2 air gap core coil error calculation results
| H2(mm) | B(T) | H(A/cm) | Φ(°) | Specific difference f L2 (％) | Angular difference delta 2 (’) |
| 1 | 0.1062 | 3.7 | 6.89 | -5.01 | -35.16 |
| 2 | 0.05612 | 1.393 | 17.52 | 1.719 | 29.86 |
| 3 | 0.03944 | 0.849 | 25.52 | -1.14 | -9.39 |
| 4 | 0.0311 | 0.577 | 33.19 | -0.79 | 3.76 |
| 5 | 0.02612 | 0.447 | 39.76 | -0.61 | -3.03 |
| 6 | 0.02278 | 0.366 | 45.71 | -0.501 | -2.26 |
| 7 | 0.0204 | 0.31 | 50.46 | -0.418 | -3.17 |
| 8 | 0.01862 | 0.271 | 54.3 | 0.356 | 3.98 |
| 9 | 0.01724 | 0.24 | 57.47 | -0.328 | -1.608 |
| 10 | 0.01614 | 0.218 | 58.97 | -0.298 | -1.435 |
Since the magnetic flux density of the air gap part is equal to that of the non-air gap part, in order to facilitate calculation, when calculating the exciting current, the air gap iron core is equivalent to a closed iron core, and then calculation is performed, and the exciting current of the air gap iron core is calculated firstly according to the calculation steps. Secondly, substituting the equivalent exciting current into the specific difference f of the closed iron core L2 Angle difference delta of sum 2 The numerical value is calculated by the formula (2). F of closed iron core when h2 is changed within 1-10mm L2 And delta 2 The relationship with h1 is shown in FIG. 4(1) and FIG. 4 (2). As shown in FIGS. 4(1) and 4(2), when h2 is 5mm, f L2 And delta 2 The change trend of (1) is gradually stable, and when h2 is 10mm, f L2 And delta 2 The value of (a) is close to 0.
According to the calculation results of the iron cores made of the two materials, because the ratio difference and the angle difference dimension obtained by the iron cores are the same, the data in the tables 1 and 2 are processed by a mode of alternately obtaining the average values of the two ratio differences to obtain the results of the comprehensive ratio differences in different heights in the following table 3, and when the comprehensive ratio difference is made to be different from h2 in the table 3, the comprehensive ratio difference of the iron cores changes with the height h1 of the ultracrystalline, as shown in fig. 5(1) to 5(10) of fig. 5(1) to 5(10), it can be known from fig. 5(1) to 5(10) that the overall change trend of the comprehensive ratio difference is the same when the height h2 is different, the error is gradually reduced, and after the height h1 is more than 5mm, the slope of the curve is reduced, and the trend of the curve tends to be stable.
When the h1 is different, the comprehensive ratio difference of the iron core is changed along with the height h2 of the notched silicon steel sheet, as shown in fig. 6(1) to 6(10), and as can be seen from fig. 6(1) to 6(10), when the h1 is different, the whole change trend of the comprehensive ratio difference is the same, and when the height h2 of the notched silicon steel sheet is 10mm, the change curve tends to be gentle, and the value is close to 0.
Table 3 integrated ratio difference results units at different heights: is based on
The data in the above tables 1 and 2 are processed by cross-calculating two kinds of angle difference mean values, and the results of the different height integrated angle differences in the following table 4 are obtained.
Table 4 different altitude composite angle difference results units: '
When different h2 is drawn according to table 4, the curve of the iron core comprehensive angle difference along with the ultracrystallite height h1 is shown in fig. 7(1) to fig. 7(10), and as can be seen from fig. 7(1) to fig. 7(10), the overall change trend of the comprehensive angle difference is the same when the h2 is different, the error is gradually reduced, and the curve trend is stable after the ultracrystallite height h1 is more than 3 mm.
When the height h2 of the notched silicon steel sheet is 10mm, the change curve of the integrated angle difference of the iron core tends to be gentle, and the value of the change curve is close to 0, as shown in fig. 8(1) to 8(10) and fig. 8(1) to 8(10) that the integrated angle difference of the iron core changes with the height h2 of the notched silicon steel sheet, when the height h1 of the notched silicon steel sheet is different from h 1.
The above-mentioned single analysis and the integrated analysis to the double-skeleton common winding current transformer iron core error are synthesized to and the iron core size: the outer diameter D is 25mm, the inner diameter D is 15mm, and the final determined framework heights of the double-framework co-winding current transformer are as follows by combining the practical production: the height h1 of the closed iron core is 5mm, the height h2 of the air gap iron core is 10mm, and the framework ratio is 1: 2. These parameters are reasonable in accordance with theoretical calculation results.
Claims (6)
1. Double-framework co-winding current transformer structure, including ultracrystalline iron core (1), silicon steel sheet iron core (2), its characterized in that: the ultra-microcrystalline iron core (1) is a closed iron core, and an air gap (3) is formed in the silicon steel sheet iron core (2).
2. The dual-bobbin co-winding current transformer structure of claim 1, wherein: the ultra-microcrystalline iron core (1) and the silicon steel sheet iron core (2) are stacked together.
3. The dual-skeleton co-winding current transformer structure of claim 1 or 2, wherein: the inner and outer radiuses of the ultracrystalline iron core (1) and the silicon steel sheet iron core (2) are consistent.
4. The dual-skeleton co-winding current transformer structure of claim 1 or 2, wherein: the height of the ultra-microcrystalline iron core (1) is h1, the height of the silicon steel sheet iron core (2) is h2, and the length of the air gap (3) is L δ 。
5. The structural design method of the double-framework common-winding current transformer is characterized by comprising the following steps of:
step 1: determining the size of the magnetic resistance Rm according to the sizes and the magnetic conductivity of the ultra-microcrystalline iron core (1) and the silicon steel sheet iron core (2);
step 2: the height of the ultra-microcrystalline iron core (1) is h1, the height of the silicon steel sheet iron core (2) is h2, and when h1 and h2 are calculated, the coil error of the double iron cores is calculated.
6. The structural design method of the double-framework common-winding current transformer according to claim 5, characterized in that: the step2 comprises the following steps:
step1, calculating the sectional area of the iron core, the average magnetic path length and the average turn length according to the size of the iron core;
obtaining the sectional area of the iron core:
wherein S1 represents the sectional area of the ultracrystalline core, D 1 Is an ultra-microcrystalline core outer diameter, d 1 Is the inner diameter h of the ultra-microcrystalline iron core 1 Is ultra-microcrystalline iron core height, K H1 The lamination coefficient of the ultracrystalline iron core is shown;
S 2 showing the sectional area of the core of silicon steel sheet, D 2 Is the outer diameter of the silicon steel sheet iron core, d 2 Is the inner diameter h of a silicon steel sheet iron core 2 Is the height of the silicon steel sheet iron core, K H2 The lamination coefficient of the silicon steel sheet iron core;
average magnetic path length L c ：
D is the outer diameter of the double iron cores, and D is the inner diameter of the double iron cores;
calculating the average turn length l co ：
D is the outer diameter of the double iron cores, D is the inner diameter of the double iron cores, and H is the total height of the double iron cores;
step2, determining the length of the lead according to the average turn length and the number of turns of the secondary winding, calculating the sectional area of the lead according to the diameter of the lead, and further solving the resistance of the lead;
length of wire L:
L＝l co ×N 2 ；
wherein N is 2 The number of turns of the secondary winding;
cross section area S of wire L ：
Wherein phi is Guide tube Is the wire diameter;
wire resistance:
step3, calculating secondary current according to the relation between the current ratio and the turn ratio, and further calculating the sum of secondary induced electromotive force by combining secondary impedance;
secondary current I 2 ：
Wherein, I 1 Is a primary current, N 1 Number of turns at one time, N 2 The number of turns is twice;
secondary induced electromotive force E 2 ：
E 2 ＝Z 2 ×I 2 ；
Wherein Z is 2 Is the total impedance of the secondary coil, E 2 For secondary induced electromotive force, I 2 Is a secondary current, S 1 Is an ultra-microcrystalline core cross-sectional area, N 2 The number of turns is twice, and f is frequency; b is m Represents the magnetic flux density;
step4, because the two iron cores are made of different materials, the magnetization curve and the loss angle curve are different, the excitation magnetic potential H and the loss angle phi in unit length are different, and when solving the excitation current and the iron core error, the two conditions of the closed iron core and the air gap iron core are required to be solved respectively;
a. solving the excitation current and the iron core error by closing the iron core;
calculating the exciting current I 01 ：
I 01 ＝K F ×H×L c ；
K F Representing a process coefficient;
calculating a core error, comprising:
the ratio difference is as follows:
the angular difference is as follows:
wherein, alpha is the impedance angle of the secondary coil;
b. solving the exciting current and the iron core error by the air gap iron core:
air gap core exciting current:
I 02 ＝K F ×H×L c
wherein, K F Taking 1.1-1.2;
calculating the active component and the reactive component of the exciting current:
the flux density of the air-gap portion is equal to that of the non-air-gap portion of the core, and therefore, the magnetic field strength of the air-gap portion:
H a denotes the magnetic field strength of the air gap portion, B m Denotes the magnetic flux density, μ, of the air gap portion a Shows the permeability of the air gap portion, also the vacuum permeability μ 0 ，L a Represents the air gap length;
the excitation current of the air gap portion can be considered as a reactive component;
I 0eq,r e＝I 02,re
I 0eq,im ＝I 02,im +I 02 ′
I 0eq,re representing the active component of the exciting current after the equivalent of the iron core with the air gap;
I 0eq,im representing the equivalent exciting current reactive component of the iron core with the air gap;
I 0eq representing the equivalent exciting current of the iron core with the air gap;
calculating a core error, comprising:
the ratio difference is as follows:
f L2 represents the ratio difference of the air gap iron core;
I 0eq representing the equivalent exciting current of the iron core with the air gap;
alpha is the secondary coil impedance angle;
I 1 represents the primary current;
the angular difference is as follows:
wherein, alpha is the impedance angle of the secondary coil;
δ 2 representing the angular difference of the air gap core;
I 0eq representing the equivalent exciting current of the iron core with the air gap;
alpha is the secondary coil impedance angle;
I 1 representing the primary current.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102800463A (en) * | 2012-09-07 | 2012-11-28 | 沧州供电公司 | Current transformer |
| US20170076858A1 (en) * | 2014-05-26 | 2017-03-16 | China Railway Corporation | Rolled iron core traction transformer |
| CN209312584U (en) * | 2019-02-27 | 2019-08-27 | 中国电力科学研究院有限公司 | A kind of anti-DC current transformer |
| WO2021088200A1 (en) * | 2019-11-05 | 2021-05-14 | 中国电力科学研究院有限公司 | Dual-stage magnetic excitation high-voltage proportional standard apparatus and error compensation method |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102800463A (en) * | 2012-09-07 | 2012-11-28 | 沧州供电公司 | Current transformer |
| US20170076858A1 (en) * | 2014-05-26 | 2017-03-16 | China Railway Corporation | Rolled iron core traction transformer |
| CN209312584U (en) * | 2019-02-27 | 2019-08-27 | 中国电力科学研究院有限公司 | A kind of anti-DC current transformer |
| WO2021088200A1 (en) * | 2019-11-05 | 2021-05-14 | 中国电力科学研究院有限公司 | Dual-stage magnetic excitation high-voltage proportional standard apparatus and error compensation method |
Non-Patent Citations (1)
| Title |
|---|
| 熊魁;岳长喜;李登云;朱凯;李智成;: "高磁导率比双铁芯电流互感器原理和误差性能研究", 电测与仪表, no. 17, 10 September 2018 (2018-09-10) * |
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