CN-115906740-B - Double E-type variable inductance design method based on coupling index

CN115906740BCN 115906740 BCN115906740 BCN 115906740BCN-115906740-B

Abstract

The invention discloses a double E-type variable inductance design method based on coupling indexes, which comprises 1) carrying out magnetic coupling analysis on the coupling problem of a main winding and a control winding of a double E-type variable inductance, defining a coupling index reflecting the coupling degree of the double E-type variable inductance according to an analysis result, 2) designing the number of turns of the main winding according to the maximum alternating current magnetic flux density and the maximum inductance value of the double E-type variable inductance by combining the coupling index, 3) establishing an improved Brauer magnetization curve model, adopting a piecewise function to improve the precision near the knee point of the Brauer magnetization curve model, determining the relation between the minimum equivalent magnetic permeability and the maximum magnetic field intensity, combining the minimum value of the inductance to design the control winding, and 4) evaluating the coupling degree of the design result according to the coupling index, ensuring that the coupling degree is positioned in an acceptable range, and completing the double E-type variable inductance design. The invention solves the problem that the existing design method does not consider that the variable inductance has winding coupling in practical application.

Inventors

DU GUIPING
WU MINGTAO
WANG XUEYI
CHEN YU

Assignees

华南理工大学

Dates

Publication Date: 20260508
Application Date: 20221208

Claims (4)

1. The double E-type variable inductance design method based on the coupling index is characterized by comprising the following steps of: 1) Performing magnetic coupling analysis on the coupling problem of the main winding and the control winding of the double-E-type variable inductor, and defining a coupling index reflecting the coupling degree of the double-E-type variable inductor according to an analysis result, wherein the magnetic coupling analysis comprises the following steps: 1.1 A double E-type variable inductance magnetic coupling model is established, alternating current in the main winding generates alternating current magnetic flux in the magnetic core, and induced electromotive forces with opposite directions are generated on the control windings at two sides: ; where e i is the induced electromotive force generated by one control winding, Is the number of turns of the actual control winding on one side, phi i is the alternating magnetic flux acting on the control winding on one side, t is time, i=1 is the control winding on the left side, i=2 is the control winding on the right side; the control winding turns are asymmetric due to the nonlinear characteristic of the magnetic core magnetization curve and the technical problem, and the control winding has induced electromotive force, so that coupling current exists, and the induced electromotive force meets the following conditions by combining the magnetic circuit law and the fundamental wave analysis method: ; Wherein e 1 is the induced electromotive force generated by the left control winding, e 2 is the induced electromotive force generated by the right control winding, N DC1 is the number of turns of the left actual control winding, N DC2 is the number of turns of the right actual control winding, I r is the alternating current amplitude, ω is the alternating current angular frequency, μ AC is the equivalent permeability of the core center post, A e is the core equivalent area, and l e is the core equivalent magnetic path length; 1.2 Defining a coupling index according to the double E-type variable inductance magnetic coupling analysis result: ; Wherein N DC is the number of turns of the control winding, N AC is the number of turns of the main winding, and f s is the working frequency; 2) According to the maximum alternating current magnetic flux density and the maximum inductance value of the double E-type variable inductor, the number of turns of the main winding is designed by combining a coupling index; 3) An improved Brauer magnetization curve model is established, precision near knee points of the Brauer magnetization curve model is improved by adopting a piecewise function, the relation between the minimum equivalent magnetic permeability and the maximum magnetic field strength is determined, and the number of turns of a control winding is designed by combining the minimum value of inductance; 4) And (3) evaluating the coupling degree of the design result according to the coupling index, ensuring that the design result is positioned in an acceptable range, and completing the double E-type variable inductance design.
2. The method for designing a double E-type variable inductance based on a coupling index according to claim 1, wherein in step 2), the number of turns of the main winding is designed, comprising the steps of: 2.1 Selecting a proper magnetic core model and confirming basic parameters thereof; 2.2 To achieve the maximum inductance value of the variable inductance, the number of turns of the main winding needs to satisfy: ; wherein L max is the maximum inductance value of the variable inductance, and R m is the magnetic core reluctance; 2.3 To prevent saturation of the variable inductance, an ac magnetic flux density upper limit value B M is set, and the number of turns of the main winding needs to satisfy: ; 2.4 According to the coupling index, the number of turns of the main winding is as small as possible, and therefore, the number of turns of the main winding is determined as follows: 。
3. The method for designing a double E-type variable inductance based on a coupling index according to claim 2, wherein in step 3), the number of turns of the control winding is designed, comprising the steps of: 3.1 When the inductance value of the variable inductance is reduced to the minimum value, the equivalent magnetic permeability of the magnetic core is minimum, and the required minimum equivalent magnetic permeability mu min is determined according to the minimum inductance value and the maximum inductance value of the variable inductance: ; Wherein mu i is the initial magnetic permeability of the magnetic core, mu 0 is the vacuum magnetic permeability, R o is the magnetic resistance of the outer magnetic arm of the magnetic core, L min is the minimum inductance value of the variable inductance, R g is the air gap magnetic resistance of the magnetic core, and R c is the magnetic resistance of the middle column of the magnetic core; 3.2 Improving the Brauer magnetization curve model, and improving the precision near the knee point of the magnetization curve model by adopting a piecewise function to obtain the relationship between the direct current magnetic field intensity and the direct current magnetic flux density: ; Wherein B is the direct current magnetic flux density, H (B) is a function of the direct current magnetic field strength H with respect to B, and c 1 、c 2 、c 3 is the Brauer magnetization curve model coefficient; 3.3 Deriving an improved Brauer magnetization curve model to obtain the relationship between the equivalent magnetic permeability and the direct current magnetic flux density: ; Wherein μ is equivalent permeability; Thus, the maximum direct current magnetic flux density B max can be determined from the minimum equivalent magnetic permeability μ min ; 3.4 Combining with the improved Brauer magnetization curve model, the maximum magnetic field strength H max can be determined according to the maximum direct current magnetic flux density B max , and the number of turns of the control winding is determined according to Maxwell equation: ; Where l o is the magnetic path length of the outer magnetic arm of the magnetic core, and I DC is the direct current control current.
4. The method for designing a double E-type variable inductance based on a coupling index according to claim 3, wherein in step 4), the degree of coupling of the design result is evaluated, comprising the steps of: And (2) calculating the coupling index of the current design result, if the coupling index is smaller than 1000, considering that the coupling degree of the design result is in an acceptable range to finish the variable inductance design, if the coupling index is larger than or equal to 1000, considering that the coupling degree of the design result is in an unacceptable range, returning to the step (2), and reselecting the proper magnetic core until the coupling degree of the design result is in the acceptable range to finish the variable inductance design.

Description

Double E-type variable inductance design method based on coupling index Technical Field The invention relates to the technical field of variable inductance parameter design, in particular to a double E-type variable inductance design method based on coupling indexes. Background The variable inductance has the characteristic of continuously adjustable and controllable inductance value, attracts a great deal of researchers to carry out research work deeply, and is widely applied to the fields of LED power supplies, resonant converters and the like. According to different structures, the variable inductor can be divided into a double E type, a triple E type, a four U type, a voltage-controlled type and the like, wherein the double E type variable inductor has application advantages compared with other variable inductors due to the characteristics of simple structure, small volume, unchanged saturation degree and the like. Although the double-E type variable inductance adopts a symmetrical control winding structure, the induced voltage generated by the main winding on the control winding is counteracted theoretically, but the control winding turns are asymmetric due to the nonlinear characteristic of the magnetic core magnetization curve and the technical problem, and the induced voltage still exists in the control winding in practice, namely the main winding and the control winding are coupled. The serious coupling problem can cause the oscillation of the variable inductance control current, which can cause negative feedback failure, increase the equivalent alternating current resistance of the main winding to cause the reduction of the system efficiency, and cause the distortion of the alternating current flowing through the main winding to cause the reduction of the reliability and the like. At present, the design method of the double-E type variable inductor does not consider the coupling problem, so how to reduce the coupling degree of the double-E type variable inductor is a main problem to be solved nowadays. Disclosure of Invention The invention aims to overcome the defects and shortcomings of the existing double-E-type variable inductance design method, provides the double-E-type variable inductance design method based on the coupling index, and solves the problem that the existing design method does not consider that the variable inductance has winding coupling in practical application. According to the method, a coupling index is defined according to magnetic coupling analysis, the coupling degree of the variable inductance is effectively reflected, an improved Brauer magnetization curve model is provided, the number of turns of the main winding is determined according to the coupling index, the number of turns of the control winding is determined, and a brand new double-E type variable inductance design method is provided based on the coupling index, so that the coupling degree of the variable inductance is in an acceptable range. In order to achieve the above purpose, the technical scheme provided by the invention is that the double E-type variable inductance design method based on the coupling index comprises the following steps: 1) Performing magnetic coupling analysis on the coupling problem of the main winding and the control winding of the double-E-type variable inductor, and defining a coupling index reflecting the coupling degree of the double-E-type variable inductor according to an analysis result; 2) According to the maximum alternating current magnetic flux density and the maximum inductance value of the double E-type variable inductor, the number of turns of the main winding is designed by combining a coupling index; 3) An improved Brauer magnetization curve model is established, precision near knee points of the Brauer magnetization curve model is improved by adopting a piecewise function, the relation between the minimum equivalent magnetic permeability and the maximum magnetic field strength is determined, and the number of turns of a control winding is designed by combining the minimum value of inductance; 4) And (3) evaluating the coupling degree of the design result according to the coupling index, ensuring that the design result is positioned in an acceptable range, and completing the double E-type variable inductance design. Further, in step 1), the magnetic coupling analysis is performed on the double-E-type variable inductance and a coupling index is defined, including the steps of: 1.1 A double E-type variable inductance magnetic coupling model is established, alternating current in the main winding generates alternating current magnetic flux in the magnetic core, and induced electromotive forces with opposite directions are generated on the control windings at two sides: Wherein e i is an induced electromotive force generated by a control winding on a certain side, N DCi is the number of turns of an actual control winding on a certain side, phi i is an alternating magnetic f