Electric transformer and method for manufacturing transformer

Abstract

This invention relates to an electric transformer and a method for manufacturing the transformer. The electric transformer includes a magnetic core and a primary coil forming a primary circuit, and a secondary coil forming a secondary circuit. The electric transformer is configured such that a first inductance value L is measured on the primary circuit when the secondary circuit is disconnected. 1so The value of the second inductance L is measured on the primary circuit when the secondary circuit is short-circuited. 1ss And measuring the value of the third inductance L on the secondary circuit with the primary circuit disconnected. 2po , such that: where A is a real number greater than 10.

Description

Technical Field

[0001] This invention relates to an electric transformer, for example, integrated in a resonant voltage converter or in any other type of power converter, and a method for manufacturing the transformer. The invention is particularly aimed at enabling control over the leakage inductance distribution in the electric transformer. Background Technology

[0002] Electric transformers enable the transfer of electrical energy from primary circuits to secondary circuits.

[0003] As is well known, in an electric transformer, a magnetic core and coils are used, in which a circulating current generates a magnetic field that allows electrical energy to be transferred from the primary circuit to the secondary circuit. More precisely, in an electric transformer, especially in a magnetized inductor converter or a resonant converter, there are primary and secondary coils formed by winding around a magnetic core, between which electrical energy is transferred.

[0004] All electric transformers have leakage inductance, which results in efficiency loss because a portion of the magnetic flux generated in the primary circuit is not captured by the windings of the secondary circuit. Furthermore, additional losses may occur in the windings. In the case of non-resonant voltage converters, overvoltage may further occur. The geometry of the transformer coils (in the same manner as the selection of the magnetic material for the core) or, alternatively, the geometry of the core, is specifically configured to comply with specific electrical and magnetic standards. One objective of transformer sizing is, in particular, to control the leakage inductance value of the transformer.

[0005] As is well known, in an electric transformer, the resonant inductor can be connected in series with the primary coil in the primary circuit.

[0006] Regardless of the intended application, the resonant inductor is obviously sized as a discrete component, operating in conjunction with an electrical transformer, which is itself sized as a discrete component. However, such an electrical transformer can be configured to minimize magnetic flux leakage, or to integrate the resonant inductor as a leakage inductor into the electrical transformer, thereby eliminating discrete electronic power components and thus reducing the cost and size of the corresponding circuit.

[0007] Therefore, the selection of integrating the resonant inductance in the transformer while utilizing its leakage inductance is a technical problem; this actually assumes that the distribution of the leakage inductance value between the primary and secondary circuits of the transformer is controlled.

[0008] As an example Figure 1 It shows an input voltage V SqFHA Output voltage V OutFHA and output resistance R FHAThe equivalent electrical diagram of a perfect LLC resonant converter is shown. The resonant capacitor Cs and the resonant inductor Ls are connected in series, and the magnetizing inductor Lp is parallel to the output terminal of the LLC resonant converter. Generally, in an LLC resonant converter, the resonant inductor Ls needs to be placed on the primary circuit.

[0009] exist Figure 2 The equivalent electrical diagram of the resonant converter LLC2 with non-negligible leakage inductance in the secondary circuit is presented based on the imperfect transformer model, where n is the turns ratio of the LLC2 resonant converter.

[0010] Here, in the absence of discrete electronic components Ls, the resonant inductor is integrated into the resonant converter LLC2. The leakage inductance of the transformer ensures the function of the resonant inductor and includes the primary circuit L. LK1 On the components and secondary circuits L LK2 Components on.

[0011] To make the imperfect model of the electric transformer as consistent as possible Figure 1 The equivalent circuit of the perfect resonant circuit LLC presented in the figure, the primary circuit L LK1 The value of the leakage inductance must be close to the value of the resonant inductance Ls, while ensuring that the secondary circuit L... LK2 The leakage inductance on the primary circuit L is compared to LK1 The leakage inductance of the secondary circuit L can be ignored in this way. LK2 The leakage inductance of the secondary circuit L should be minimized. In other words, it is desirable to minimize the leakage inductance of the secondary circuit L. LK2 The leakage inductance value on the circuit is less than that of the primary circuit L. LK1 The leakage inductance value on the circuit or even compared to the primary circuit L LK1 The leakage inductance value can be ignored.

[0012] Therefore, it is noteworthy that the operating point of the resonant converter LLC2, like any transformer, its cutoff frequency, and thus its losses, are related to the distribution of the leakage inductance between the primary and secondary circuits. Poor distribution of the leakage inductance can cause a significant shift in the transformer's operating point relative to its defined optimal operating point, potentially leading to overheating risks or even damage to the transformer's electronic power components.

[0013] Specifically, in some applications, the distribution of leakage inductance between the primary and secondary circuits of the control transformer is of considerable importance. For example, any type of resonant converter (including LC, LLC, or CLLC topologies) requires leakage inductance concentrated on the primary circuit. However, for certain applications of reversible converters (such as dual active bridge (DAB) type converters), a non-negligible leakage inductance may be required on the secondary circuit.

[0014] However, in many applications, it is particularly advantageous to find the main portion of the leakage inductance value on the primary circuit in order to ensure the resonant inductance function of the transformer in a resonant circuit of the LC, LLC or CLLC type.

[0015] This invention is particularly capable of determining the distribution of leakage inductance values ​​between the leakage inductance in the primary circuit and the leakage inductance in the secondary circuit of an electric transformer. This invention may also be capable of determining the magnetizing inductance value of an electric transformer.

[0016] Subsequently, the present invention is particularly likely to produce electric transformers with the desired leakage inductance (especially concentrated in the primary circuit). Summary of the Invention

[0017] More precisely, the present invention relates to an electric transformer comprising a magnetic core and a primary coil forming a primary circuit, and a secondary coil forming a secondary circuit, the electric transformer being configured such that:

[0018] With the secondary circuit disconnected, measure the value of the first inductance L on the primary circuit. 1so ,

[0019] Measure the value of the second inductance L on the primary circuit when the secondary circuit is short-circuited. 1ss ,as well as

[0020] Measure the value of the third inductance L in the secondary circuit with the primary circuit disconnected. 2po ,

[0021] Make:

[0022] [Mathematical Expression 1]

[0023]

[0024] in

[0025] [Mathematical Expression 2]

[0026]

[0027] Where A is a real number greater than 10.

[0028] Where A is a real number greater than 10.

[0029] According to one embodiment, A is a real number greater than or equal to 50.

[0030] According to one embodiment, A is a real number less than or equal to 100.

[0031] The present invention also relates to a method for manufacturing a transformer, the transformer having a magnetic core, a primary circuit, and a secondary circuit, the method comprising the following steps:

[0032] Select the core geometry for the electric transformer to be manufactured;

[0033] Determine the thickness of the air gap corresponding to the required magnetizing inductance value of the transformer to be manufactured;

[0034] The secondary winding is wound onto a magnetic core having a selected geometry and air gap thickness in order to cover the air gap;

[0035] The leakage magnetic resistance value of the transformer varies with the ratio between the required leakage inductance value on the primary circuit of the transformer to be manufactured and the required magnetizing inductance value of the transformer to be manufactured.

[0036] Determine the distance h between the primary winding and the secondary winding, which varies with the leakage magnetic resistance value, wherein the primary winding is configured to form the primary circuit of the transformer to be manufactured.

[0037] The primary winding is wound onto the core of the transformer at a distance h from the secondary winding.

[0038] According to one embodiment, the magnetic core is selected from type E or type EI.

[0039] According to one embodiment, the following equations are implemented:

[0040] [Mathematical Expression 3]

[0041]

[0042] Where N1 is the number of windings in the primary circuit, μ0 is the electromagnetic permeability of air, and S is the effective magnetic cross-sectional area of ​​the transformer.

[0043] To determine the corresponding magnetization inductance value L M The required thickness e of the air gap.

[0044] According to one embodiment, the following equations are implemented:

[0045] [Mathematical Expression 4]

[0046]

[0047] Where Rgap is the air gap reluctance of the transformer, μ0 is the electromagnetic permeability of air, e is the thickness of the air gap of the transformer, and S is the effective magnetic cross-sectional area of ​​the transformer.

[0048] and

[0049] [Mathematical Expression 5]

[0050]

[0051] Where Rleakage is the leakage magnetic reluctance of the transformer, Lf1 is the leakage inductance in the primary circuit of the transformer, and L M For the magnetizing inductance of an electric transformer,

[0052] To determine the leakage magnetic resistance value of the transformer.

[0053] According to one embodiment, the following equations are implemented:

[0054] [Mathematical Expression 6]

[0055]

[0056] Wherein corresponds to the distance between the outer and central legs of the core separating type E or type EI, Rleakage is the leakage magnetic reluctance of the transformer, μ0 is the electromagnetic permeability of air, m is the core depth of the transformer, and l is the width of the electromagnetic leakage region between the primary and secondary windings.

[0057] To determine the value of the distance h between the primary winding and the secondary winding. Attached Figure Description

[0058] The invention will be better understood by reading the following description, given only as examples and by referring to the accompanying drawings, given as non-limiting examples, wherein like references are given to similar objects, and wherein:

[0059] Figure 1 : Figure 1 (As described) Presents the equivalent circuit of a perfect resonant converter.

[0060] Figure 2 : Figure 2 (As described) Presents the equivalent circuit of an imperfect resonant converter.

[0061] Figure 3 : Figure 3 Present the equivalent magnetic circuit of an electric transformer with a given geometry.

[0062] Figure 4 : Figure 4 A diagram showing an electric transformer according to an exemplary embodiment of the present invention is provided.

[0063] Figure 5 : Figure 5 A block diagram illustrating the steps of implementing a method for manufacturing an electric transformer according to an embodiment of the present invention is presented.

[0064] It should be noted that the accompanying drawings illustrate the invention in a detailed manner for carrying out the invention, and these drawings are obviously useful for better defining the invention when necessary.

[0065] Explanation of icon numbers

[0066] 1: Primary winding;

[0067] 2: Secondary winding;

[0068] Cs: Resonant capacitor;

[0069] e: thickness;

[0070] E1, E2, E3, E4, E5, E6, E7: Steps;

[0071] F: Magnetic core;

[0072] flux_leak1, flux_leak2, flux_sec: magnetic flux;

[0073] flux_pri: Primary flux;

[0074] flux_total: Total magnetic flux;

[0075] G: Air gap;

[0076] h: distance;

[0077] l: width;

[0078] L 1so First inductance value;

[0079] L 1ss Second inductance value;

[0080] L 2po Third inductance value;

[0081] Lf1: Leakage inductance value;

[0082] L LK1 Primary circuit;

[0083] L LK2 Secondary circuit;

[0084] L M : Magnetizing inductance value;

[0085] Lp: Magnetizing inductance;

[0086] Ls: Resonant inductance;

[0087] R1, R2, R3, R4: Equivalent magnetic reluctance;

[0088] R FHA Output resistance;

[0089] Rleakage: Leakage magnetic resistance value;

[0090] S1, S2: Leakage zone;

[0091] V1: Voltage;

[0092] V OutFHA Output voltage;

[0093] V SqFHA Input voltage. Detailed Implementation

[0094] This invention may determine the leakage inductance values ​​in the primary circuit and the secondary circuit of an electric transformer.

[0095] A derivative objective is to adapt the geometry of the electric transformer so that the leakage inductance in the primary circuit and the leakage inductance in the secondary circuit match the desired inductance values ​​in the primary and secondary circuits, respectively. Specifically, when the electric transformer is supplied only in the primary circuit, magnetic flux not connected to the secondary circuit leaks into the primary circuit. This situation corresponds to, for example... Figure 3 The equivalent magnetic circuit presented in the figure.

[0096] It is noteworthy that, as previously indicated, it may be necessary to locate the major portion of the leakage inductance value of the transformer in the primary circuit. In other words, in this case, the aim is to minimize the leakage inductance value in the secondary circuit. Subsequently, the leakage inductance value in the secondary circuit needs to be smaller than the inductance value in the primary circuit, for example, at least ten times smaller, preferably 50 to 100 times smaller.

[0097] For a particular transformer with a specific geometry, the present invention may determine the leakage inductance in the primary circuit, the leakage inductance in the secondary circuit, and the magnetizing inductance.

[0098] For this purpose, three inductance measurements were performed on the aforementioned transformer.

[0099] With the secondary circuit disconnected, the first inductance measurement L is performed on the primary circuit. 1so .

[0100] In the case of a short circuit in the secondary circuit, a second inductance measurement L is performed on the primary circuit. 1ss .

[0101] With the primary circuit disconnected, a third inductance measurement L is performed on the secondary circuit. 2po .

[0102] Next, solve the following system of equations:

[0103] [Mathematical Expression 7]

[0104] L 1sO =L Lk1 +L M

[0105] [Mathematical Expression 8]

[0106]

[0107] [Mathematical Expression 9]

[0108]

[0109] Therefore, the primary L is determined Lk1 The leakage inductance value on the upper side, the secondary L Lk2 The leakage inductance value and the magnetizing inductance value L of the transformer. M .

[0110] With the help of knowing the primary circuit L Lk1 The leakage inductance value of the upper circuit, the secondary circuit L Lk2 The leakage inductance and magnetizing inductance L on the surface M Given the desired leakage inductance values ​​on the primary circuit and the secondary circuit, the geometry of the transformer is adjusted to approximate the desired values.

[0111] Specifically, in order to concentrate the leakage inductance value of the transformer on the primary circuit, the ratio between the leakage inductance on the primary circuit and the leakage inductance on the secondary circuit is greater than 10, especially between 10 and 100, and especially between 50 and 100.

[0112] In other words, according to the present invention, the transformer is preferably configured such that a first inductance measurement L is performed on the primary circuit. 1so The second inductance L of the primary circuit is measured. 1ss Furthermore, with the primary circuit disconnected, the third inductance L is measured on the secondary circuit. 2po , so that:

[0113] [Mathematical Expression 10]

[0114]

[0115] in

[0116] [Mathematical Expression 11]

[0117]

[0118] Where A is a real number greater than 10, especially greater than 50, and especially less than or equal to 100, and N is the transformer ratio.

[0119] Therefore, one object of the present invention is to manufacture an electric transformer by configuring the leakage inductance distribution of the electric transformer as needed (especially by concentrating the leakage inductance on the primary circuit). For this purpose, a transformer is manufactured as follows... Figure 3The equivalent magnetic circuit of the electric transformer, which varies with its geometry, is presented in the diagram. Therefore, Figure 3 The equivalent magnetic circuit presented corresponds to a given geometry of an electric transformer supplied with voltage V1. The electric transformer is considered using the values ​​of equivalent electronic components (especially equivalent reluctance R1, equivalent reluctance R2, equivalent reluctance R3, and equivalent reluctance R4) based on the positioning of the primary and secondary coils, the transformation ratio, the number and size of the core legs, and the location of the air gap. These values ​​are not easily measured, but their distribution can be affected by modifying the geometry of the electric transformer.

[0120] refer to Figure 3 Therefore, the total magnetic flux is flux_total, of which a portion flux_sec is transferred to the secondary circuit, while two other portions, flux_leak1 and flux_leak2, correspond to the magnetic flux leaking into the primary circuit.

[0121] from Figure 3 Starting with the equivalent magnetic diagram, and with the help of knowledge of the primary circuit L... LK1 The required values ​​for the magnetizing inductance and leakage inductance, and the secondary circuit L. LK2 The desired values ​​of magnetizing inductance and leakage inductance (especially determined according to the invention and corresponding to the transformer under consideration or to be manufactured due to the type of geometry) make it possible to determine the geometric specifications of the transformer, particularly the thickness of the air gap and the relative positioning of the primary and secondary coils.

[0122] Other geometrical factors (such as the location of the air gap, the number and size of the core legs) can be considered within the context of implementing a method for manufacturing an electric transformer according to an embodiment of the invention to influence the distribution of equivalent reluctance R1, equivalent reluctance R2, and equivalent reluctance R3 in order to obtain the desired distribution of leakage inductance in the electric transformer. For example, it can be compared with... Figure 4 The corresponding analysis of the transformer diagram. Figure 3 The equivalent magnetic circuit. Subsequently, in Figure 3 In the equivalent magnetic circuit, reluctance R1 and reluctance R3 represent the corresponding Figure 4 The leakage magnetic resistance in leakage regions S1 and S2 is given. Magnetic resistance R2 represents the air gap magnetic resistance G, which is composed of… Figure 4 The secondary winding 2 is covered. Therefore, by reducing the values ​​of leakage reluctance R1 and leakage reluctance R3 relative to reluctance R2, the magnetic flux across the region separating the primary and secondary windings increases, and thus the value of leakage inductance in the primary circuit increases. This reduction in the values ​​of leakage reluctance R1 and leakage reluctance R2 can be achieved, in particular, by separating the primary and secondary windings.

[0123] In order to make the secondary circuit L LK2Minimizing leakage inductance requires selecting a core geometry that allows the air gap to be surrounded on both sides by windings from the secondary coil. This is achieved through analysis in the "opposite" sense. Figure 3 The equivalent magnetic circuit is constructed, and by shifting the voltage source V1 to the secondary flux flux_sec side, the magnetic reluctances R1 and R3, which are 100 times larger than the magnetic reluctance R4 of the magnetic circuit, prevent any intersection of magnetic leakage fluxes. Therefore, all magnetic fluxes will pass through the primary flux flux_pri with minimized leakage flux.

[0124] refer to Figure 4 and Figure 5 The following details a method for manufacturing an electric transformer based on previously proposed equations and principles, which relates to the distribution of leakage inductance between the primary and secondary circuits of the electric transformer.

[0125] More specifically, the examples detailed below involve electric transformers with an integrated leakage inductance (with a magnetic core F of type E or type EI) concentrated on the primary circuit.

[0126] In order to manufacture an inductance value L with the desired magnetization value M With the required leakage inductance value and the electric transformer concentrated in the primary circuit, the equations developed below are implemented.

[0127] [Mathematical Expression 12]

[0128]

[0129] in:

[0130] N1 is the number of primary windings;

[0131] μ0 is the magnetic permeability of air;

[0132] S is the effective magnetic cross-sectional area of ​​the transformer;

[0133] e represents the thickness of the air gap G in the transformer.

[0134] [Mathematical Expression 13]

[0135]

[0136] Where R gap Let G be the air gap magnetoresistance.

[0137] [Mathematical Expression 14]

[0138]

[0139] in:

[0140] Rleakage is the leakage magnetic resistance of an electric transformer;

[0141] Lf1 is the required leakage inductance value of the transformer in the primary circuit;

[0142] L M This is the required magnetizing inductance value for the electric transformer.

[0143] The leakage magnetic resistance Rleakage between the primary winding 1 and the secondary winding 2 involves regions S1 and S2 between the primary winding 1 and the secondary winding 2.

[0144] Subsequently, for an electric transformer with a core F of type E or type EI (where the core depth is indicated in m), the leakage magnetic resistance Rleakage can be estimated using the following equation:

[0145] [Mathematical Expression 15]

[0146]

[0147] Where h is the distance separating the primary winding 1 and the secondary winding 2, and l is the width of region S1 and region S2, as shown below. Figure 4 As indicated in the diagram. Therefore, the width l corresponds to the width of the electromagnetic leakage region between the primary winding 1 and the secondary winding 2, and thus corresponds to the distance between the outer and center feet of the magnetic core F separating type E or type EI.

[0148] Certain electrical transformers (especially those with PQ-type magnetic cores) contain a core depth that is not constant. In such cases, the estimated root mean square value of the core depth can be used to implement a method for manufacturing an electrical transformer according to an example of the invention.

[0149] For another geometry of the transformer (in which the windings of the primary circuit are distributed on two upper and lower portions on both sides of the secondary winding), the calculated distance h can be calculated as the sum of two corresponding distances between each portion of the primary circuit winding (distributed symmetrically) and each portion of the secondary circuit winding.

[0150] Known simulation tools can be further implemented to analyze the leakage magnetoresistance (Rleakage) of the transformer to be manufactured.

[0151] In order to design and manufacture the electric transformer according to the present invention, especially the electric transformer in which the leakage inductance value is concentrated on the primary circuit, the following reference is made. Figure 5 Therefore, the steps are reasonable.

[0152] First, (step E1) define the required values ​​of the leakage inductance Lf1 and the magnetizing inductance L of the transformer to be manufactured. M Next, select, for example, according to the requirements of the manufacturer, the transformer to be manufactured. Figure 4The core geometry (step E2) of the example (core of type E) is reasonable. Thereafter, the required value L corresponding to the magnetizing inductance is calculated using the equation [Mathematical Formula 12] above. M The required thickness e of the air gap G is determined (step E3). Subsequently, the secondary winding 2 is wound onto the magnetic core F in a manner corresponding to the selected geometry and the calculated thickness of the air gap G (step E4), so that the air gap G is completely covered by the secondary winding 2. Using equations [Mathematical Formula 13] and [Mathematical Formula 14], the required value Lf1 of the leakage inductance on the primary circuit (which preferably concentrates the leakage inductance of the transformer) and the required value L of the magnetizing inductance of the transformer are calculated. M The leakage magnetic resistance value Rleakage varies with the ratio between the two windings (step E5). The distance h between the primary winding 1 and the secondary winding 2 is calculated using equation [Mathematical Formula 15] (step E6). Subsequently, the primary winding 1 is wound around the core of the transformer to conform to the distance h (step E7).

[0153] If necessary, the arrangement of the primary winding 1 and / or the secondary winding 2 can be adjusted according to the actual measurements of the resulting leakage inductance and magnetizing inductance on the transformer. These complementary measurements allow for fine adjustment of the distance h, thereby achieving the desired leakage inductance value on the primary winding in a more precise manner.

Claims

1. A method for manufacturing an electric transformer, the electric transformer having a magnetic core, a primary circuit, and a secondary circuit, the method comprising the following steps: Select the core geometry for the electric transformer to be manufactured; Determine the thickness of the air gap corresponding to the required magnetizing inductance value of the transformer to be manufactured; The secondary winding is wound around a magnetic core of a selected geometry and thickness with an air gap in order to cover the air gap; The leakage magnetoresistance value of the transformer is determined as a ratio between the desired leakage inductance value on the primary circuit of the transformer to be manufactured and the desired magnetization inductance value of the transformer to be manufactured. Determine the distance h between the primary winding and the secondary winding, which varies with the leakage magnetic resistance value, wherein the primary winding is configured to form the primary circuit of the transformer to be manufactured; The primary winding is wound onto the core of the transformer at a distance h from the secondary winding. The following equations are implemented in the method: Where N1 is the number of windings in the primary circuit, μ0 is the electromagnetic permeability of air, and S is the effective magnetic cross-sectional area of ​​the transformer. To determine the corresponding desired magnetization inductance value L M The required thickness e of the air gap.

2. The method of claim 1, wherein the magnetic core is selected from type E or type EI.

3. The method according to claim 1 or 2, wherein the following equation is implemented: Where R gap Let μ0 be the air gap reluctance of the transformer, μ0 be the electromagnetic permeability of air, e be the thickness of the air gap of the transformer, and S be the effective magnetic cross-sectional area of ​​the transformer. and Where Rleakage is the leakage magnetic reluctance of the transformer, Lf1 is the leakage inductance in the primary circuit of the transformer, and L M The magnetizing inductance of the aforementioned transformer, To determine the leakage magnetic resistance value of the electric transformer.

4. The method of claim 2, wherein the following equation is implemented: Wherein, Rleakage corresponds to the distance between the outer and central legs of the core separating type E or type EI, Rleakage is the leakage magnetic reluctance of the transformer, μ0 is the electromagnetic permeability of air, m is the core depth of the transformer, and l is the width of the electromagnetic leakage region between the primary winding and the secondary winding. To determine the value of the distance h between the primary winding and the secondary winding.

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