KR20230068464A - Transformer using Leakage Inductance And Design Method Therefor - Google Patents

Abstract

A transformer using leakage inductance, which can satisfy insulation performance, have minimal loss, and remove an external inductor from an existing DAB converter, and a design method therefor are disclosed. According to one aspect of the present disclosure, provided is a semiconductor transformer, which is a semiconductor transformer including an AC/DC converter and a DC/DC converter, wherein the DC/DC converter comprises: a high-frequency transformer including a core, primary winding and secondary winding; a first bridge circuit connected between the AC/DC converter and the primary winding, and converting direct current voltage into high frequency alternating current; and a second bridge circuit connected between the secondary winding and a first output terminal, and outputting direct current voltage, wherein the secondary winding comprises a secondary upper winding wound on one side of the primary winding and a secondary lower winding wound on the other side of the primary winding.

Description

Transformer using Leakage Inductance And Design Method Therefor}

The present disclosure relates to a transformer using leakage inductance and a design method thereof.

The information described in this section simply provides background information on the present invention and does not constitute prior art.

In a conventional railway vehicle, power conversion consisting of a main transformer, an AC/DC converter, and a DC/AC inverter that steps down high-voltage AC power supplied through a trolley line and converts it into low-voltage AC power. system has been used. Since the main transformer operates at a low frequency of 50 Hz to 60 Hz, the value of inductance required for impedance matching is large, so there is a problem in that the weight and volume are large due to the need to wind many transformer windings or use many iron cores.

To solve this problem, a semiconductor composed of an AC/DC converter that rectifies the high-voltage AC power supplied from the catenary line and a DC/DC converter that converts the rectified DC power into high-frequency AC power and then generates low-voltage DC power. A solid-state transformer is being developed.

A DC/DC converter must satisfy insulation performance between high voltage and low voltage, and to this end, the insulation design of a high-frequency transformer provided in the DC/DC converter is very important. For example, a semiconductor transformer used in a high-speed rail vehicle receives voltage through a 25 kV/60 Hz catenary line, and at this time, the voltage of the catenary line can rise to 29 kV. In this case, the high-frequency transformer must be designed to satisfy the insulation performance of 60 kV between the high voltage and the low voltage in consideration of the double margin factor. In addition, the high-frequency transformer must be designed to minimize core loss and winding loss so as to have thermal stability even when driven for a long time.

Meanwhile, as a DC/DC converter, a dual active bridge (DAB) converter including a magnetic component composed of a high frequency transformer and an external inductor is widely used. Here, the external inductor serves to deliver input/output power, and the high-frequency transformer serves to secure a voltage ratio through a turn ratio while securing insulation between high voltage and low voltage. However, the conventional DAB converter has a disadvantage in that the size of the magnetic component increases due to the external inductor.

The main object of the present disclosure is to provide a high-frequency transformer that satisfies tens of kV class insulation performance and has minimum loss while removing an external inductor from an existing DAB converter and a design method thereof.

The problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

According to one aspect of the present disclosure, in a semiconductor transformer including an AC/DC converter and a DC/DC converter, the DC/DC converter includes a core, a primary winding, and a secondary winding. A high-frequency transformer including; a first bridge circuit connected between an AC/DC converter and the primary side winding and converting a direct current voltage into a high frequency alternating current; and a second bridge circuit connected between the secondary winding and the first output terminal and outputting a DC voltage, wherein the secondary winding includes a secondary upper winding wound on one side of the primary winding; and a secondary-side lower winding wound on the other side of the primary-side winding.

According to another aspect of the present disclosure, it includes a core, a primary winding, and a secondary winding, wherein the secondary winding includes a secondary upper winding wound on one side of the primary winding and two windings wound on the other side of the primary winding. A method of designing a high frequency transformer composed of a secondary lower winding, comprising: selecting a size of the core based on a size of a space in which the high frequency transformer can be disposed; selecting the number of turns of the primary winding and the secondary winding so that the leakage inductance and turn ratio of the high frequency transformer satisfy predetermined conditions; and determining the thicknesses of the primary winding and the secondary winding.

As described above, according to the exemplary embodiment of the present disclosure, it is possible to reduce the size of the magnetic component by removing the external inductor while satisfying the insulation performance of several tens of kV and having minimum loss.

The effects of the present disclosure are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description below.

1 is a diagram illustrating a power conversion system using a semiconductor transformer according to an embodiment of the present disclosure.
2 is a schematic configuration diagram of a semiconductor transformer according to an exemplary embodiment of the present disclosure.
3 is a schematic circuit diagram of a power conversion module according to an embodiment of the present disclosure.
4A and 4B are exemplary diagrams schematically showing the structure of a high frequency transformer according to an embodiment of the present disclosure.
5 is an equivalent circuit diagram of a high frequency transformer according to an embodiment of the present disclosure.
6 is an exemplary diagram schematically illustrating a geometric structure of a high frequency transformer according to an embodiment of the present disclosure.
7 is an exemplary view schematically illustrating a winding arrangement structure of a high frequency transformer according to an embodiment of the present disclosure and a magnetomotive force for each position.
8 is an exemplary diagram schematically illustrating an insulation structure of windings of a high frequency transformer according to an embodiment of the present disclosure.
9 is a flowchart illustrating a method of designing a high frequency transformer according to an embodiment of the present disclosure.
10 is an exemplary diagram for explaining an arrangement space of a high frequency transformer according to an embodiment of the present disclosure.
11 is an exemplary diagram for explaining operating conditions of a high frequency transformer according to an embodiment of the present disclosure.
12 is an exemplary diagram schematically illustrating a simulation model for a high frequency transformer according to an embodiment of the present disclosure.
13 to 19 are exemplary diagrams illustrating simulation results of a high frequency transformer according to an embodiment of the present disclosure.

Hereinafter, some embodiments of the present disclosure will be described in detail through exemplary drawings. In adding reference numerals to components of each drawing, it should be noted that the same components have the same numerals as much as possible even if they are displayed on different drawings. In addition, in describing the present disclosure, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present disclosure, the detailed description will be omitted.

Also, terms such as first, second, A, B, (a), and (b) may be used in describing the components of the present disclosure. These terms are only used to distinguish the component from other components, and the nature, order, or order of the corresponding component is not limited by the term. Throughout the specification, when a part 'includes' or 'includes' a certain component, it means that it may further include other components without excluding other components unless otherwise stated. . In addition, the '... Terms such as 'unit' and 'module' refer to a unit that processes at least one function or operation, and may be implemented as hardware, software, or a combination of hardware and software.

The detailed description set forth below in conjunction with the accompanying drawings is intended to describe exemplary embodiments of the present disclosure, and is not intended to represent the only embodiments in which the present disclosure may be practiced.

1 is a diagram illustrating a power conversion system using a semiconductor transformer according to an embodiment of the present disclosure.

As shown in FIG. 1 , the power conversion system according to an embodiment of the present disclosure may include all or part of a semiconductor transformer 100 and an inverter 110 for driving a motor. Meanwhile, although FIG. 1 shows an example in which the power conversion system according to an embodiment of the present disclosure is applied to a railroad car, it is not limited thereto and the power conversion system can be applied to various environments.

The semiconductor transformer 100 includes an AC/DC converter 102 for rectifying high-voltage AC power and at least one DC/DC converter 104 for generating low-voltage DC power after converting the rectified DC power into high-frequency AC power. can include

2 is a circuit diagram schematically illustrating a semiconductor transformer according to an exemplary embodiment of the present disclosure.

As shown in FIG. 2, the semiconductor transformer 100 according to an embodiment of the present disclosure includes a plurality of power conversion modules 200, 210, and 220, and each power conversion module 200, 210, and 220 is AC /DC converter 202 and DC/DC converter 204 may be included.

The plurality of power conversion modules 200, 210, and 220 have input terminals connected in series to share and receive the voltage of high-voltage AC power supplied from the catenary line, thereby reducing voltage stress applied to the power semiconductor.

The plurality of power conversion modules 200, 210, and 220 have output terminals connected in parallel to share and output power required by the railway vehicle, thereby reducing current stress.

3 is a schematic circuit diagram of a power conversion module according to an embodiment of the present disclosure.

As shown in Figure 3, the power conversion module 200 according to an embodiment of the present disclosure may include an AC / DC converter 202 and a DC / DC converter 204, to reduce the voltage stress of the switching element To this end, the DC/DC converter 204 may have a stack structure of the first DC/DC converter 300 and the second DC/DC converter 310 .

The first DC/DC converter 300 and the second DC/DC converter 310 may include all or part of the first bridge circuit 302, the high frequency transformer 304, and the second bridge circuit 306, respectively. . According to embodiments, the first bridge circuit 302 may have a half-bridge structure and the second bridge circuit 306 may have a full-bridge structure, but is not limited thereto. .

The high frequency transformer 304 may include a primary winding and a secondary winding, and the turn ratio between the primary winding and the secondary winding is N ₁ :N ₂ Or it can be expressed as n _a : 1. The high frequency transformer 304 may have a leakage inductance (Ld).

Input terminals of the first DC/DC converter 300 and the second DC/DC converter 310, that is, inputs of the first bridge circuits 302 may be connected in series. Output terminals of the first DC/DC converter 300 and the second DC/DC converter 310, that is, the outputs of the second bridge circuits 306 may be connected in series or parallel.

The first bridge circuit 302 is connected between the AC/DC converter 202 and the primary winding of the high-frequency transformer 304, and converts the DC voltage (V _{dcH_m} or V _{dcL_m} ) received from the AC/DC converter 202 to Converts to high-frequency alternating current (i _{pH _m} or i _{pL _m} ).

The second bridge circuit 306 is connected to the secondary winding of the high frequency transformer 304, and generates a DC voltage (V _{LH _m} or V _{LL_m} ) from the AC current (i _{sH _m} or i _{sL_m} ) applied through the high frequency transformer 304. ) to create

According to embodiments, the first bridge circuit 302 and the second bridge circuit 306 may implement a Dual Active Bridge (DAB) topology in which power is transferred through a phase difference between the two bridges. Accordingly, the DC voltage (V _{LH _m} or V _{LL_m} ) is the phase control between the first bridge circuit 302 and the second bridge circuit 306 and the turn ratio between the primary winding and the secondary winding (N ₁ :N ₂ ) can be determined according to

4A and 4B are exemplary diagrams schematically showing the structure of a high frequency transformer according to an embodiment of the present disclosure.

4A and 4B, a high frequency transformer 304 according to an embodiment of the present disclosure includes a shell-type core 400, a primary winding 410, and a secondary winding 420. can include At this time, the primary side winding 410 may be molded with an epoxy insulator 430 to secure insulation.

According to an embodiment of the present disclosure, the secondary winding 420 may have a structure separated from the primary winding 410 as a center. In other words, a secondary upper winding 422 wound on one side of the primary winding 410 of the secondary winding 420 according to an embodiment of the present disclosure and winding on the other side of the primary winding 410 A secondary lower winding 424 may be included. Meanwhile, in the present disclosure, the terms 'upper' and 'lower' are only for distinguishing the relative positions of different secondary windings 420 with respect to the primary winding 410, and the absolute position of the secondary winding 420. does not limit

Since the high frequency transformer 304 according to an embodiment of the present disclosure has a structure in which a secondary winding is separated, it is possible to secure a larger leakage inductance than a conventional winding arrangement structure and improve core loss.

5 is an equivalent circuit diagram of a high frequency transformer according to an embodiment of the present disclosure.

Referring to Figure 5, r _c,p and r _c,s represent the copper loss resistance of the primary and secondary side, respectively, L _l,p and L _l,s represent the leakage inductance of the primary and secondary side, respectively, and L _m is the magnetization Indicates the inductance (magnetizing inductance).

Here, the equivalent inductance viewed from the secondary side can be expressed as Equation 1.

Assuming that the voltage drop due to the primary side winding loss resistance (r _c,p ) is negligible, the magnetizing current ( _im ) can be expressed as in Equation 2.

Here, w _s of the DAB converter is the switching frequency.

Assuming that the leakage magnetic field is much smaller than the magnetizing magnetic field (L _m >> L _l,p ), the magnetic flux density (B _c ) of the core can be calculated as in Equation 3 .

Here, N _p is the number of turns of the primary winding, and A _c is the magnetic path area of the core.

The minimum value of the number of turns (N _p ) of the primary winding that satisfies the condition that the magnetic flux density (B _c ) of the core is less than the preset magnetic saturation level at the point where the magnetizing current is maximum is It can be calculated as in Equation 4.

Hereinafter, a process of deriving leakage inductance and loss of a high frequency transformer according to an embodiment of the present disclosure will be described with reference to FIGS. 6 and 7 .

6 is an exemplary diagram schematically illustrating a geometric structure of a high frequency transformer according to an embodiment of the present disclosure.

7 is an exemplary view schematically illustrating a winding arrangement structure of a high frequency transformer according to an embodiment of the present disclosure and a magnetomotive force for each position.

Referring to FIG. 6 , under a given geometric structure, an effective magnetic flux distance (l _e ) and a magnetic flux cross-sectional area (A _c ) of a core according to an embodiment of the present disclosure may be defined as in Equation 5.

From Equation 5, the magnetization inductance (L _m ) can be calculated as Equation 6.

Here, L _p is the total inductance of the primary side.

When the primary winding and the secondary winding constitute a plurality of winding layers as shown in FIG. 7 , the number of turns of the primary winding and the secondary winding may be expressed as in Equation 7. Meanwhile, in FIG. 7, a winding marked with '⊙' represents a primary winding, and a winding marked with 'ⓧ' represents a secondary winding.

Here, m _p is the number of winding layers of the primary winding, n _p,j is the number of turns of each layer of the primary winding, m _s is the number of winding layers of the secondary winding, and n _s,j is the turns of each layer of the secondary winding It is a number.

The magnetic field strength at an arbitrary ampere-turn within a window area through which the primary and secondary windings pass may be defined as in Equation 8.

Here, h is the thickness of the winding wire.

When the magneto-motive-force (mmf) at each position in the window area is the same as in FIG. 7 , the magnetic field strength at the position where the primary winding exists can be calculated as in Equation 9.

Here, h _p is the thickness of the primary side winding, and h _po is the spacing between the primary side windings.

Next, the magnetic field strength between the primary windings can be calculated as shown in Equation 10.

Next, the magnetic field strength between the primary winding and the secondary winding can be calculated as shown in Equation 11.

Here, h _d is the distance between primary winding and secondary winding.

Meanwhile, in Equations 9 and 10, only the magnetic field strength at the position of the primary winding is shown, but it is obvious that the same can be applied to the secondary winding. In this case, the thickness of the secondary winding may be referred to as h _s , and the interval between the secondary windings may be referred to as h _so .

Using the magnetic field strength calculated according to Equations 9 to 11, the total energy E _t stored through the leakage inductance can be derived as shown in Equation 12. In this case, the primary side leakage inductance and the secondary side leakage inductance may be expressed as a function of H(z).

Here, l _m is the mean length in each turn.

Equal spacing between windings (h _po = h _so = h _d ≡ h _n ), equal number of winding layers (m _p = m _s = m _n ), equal primary and secondary ampere-turns (N _p Assuming that I _p = N _s I _s ), the total energy E _t can be simplified as in Equation 13.

As described above, using Equations 9 to 13, the primary side leakage inductance (L _l,p ) and the secondary side leakage inductance (L _l,s ) can be derived under given conditions.

On the other hand, transformer loss is largely composed of core loss and winding loss.

There are various techniques for calculating the core loss of a high-frequency transformer. Since the DAB converter has a non-sinusoidal current waveform, in the present disclosure, IGSE (Improved Generalized Steinmetz Equation) considering the non-sinusoidal characteristic is used. At this time, the core loss (P _co ) may be calculated as in Equations 14 and 15.

Here, Cm, α, and β are parameters determined according to magnetic characteristics, and U _C is the total volume of the nose.

Meanwhile, the winding loss (P _cp ) can be expressed as the product of the square of the current and the AC resistance component as shown in Equation 15. At this time, the resistance component (r _{c, p} and r _c,s ) may be calculated based on the geometrical information and switching frequency of the winding.

Finally, the total transformer loss (P _ct ) can be expressed as the sum of core loss (P _co ) and winding loss (P _cp ).

8 is an exemplary diagram schematically illustrating an insulation structure of windings of a high frequency transformer according to an embodiment of the present disclosure.

Referring to FIG. 8 , windings applied to a high-frequency transformer according to an embodiment of the present disclosure include a plurality of copper wires (800), a first wrapping and fixing a plurality of copper wires so as to secure their own insulation performance. It may be composed of an insulation material 810 , a second insulation material 820 surrounding the first insulation material 810 , and a third insulation material 830 surrounding the second insulation material 820 .

The copper wire 800 may preferably be implemented as a Litz wire capable of minimizing high-frequency resistance, but is not limited thereto. The thickness of the copper wire 800 may be determined in consideration of the current capacity.

The first insulating material 810 serves to fix the shape of the plurality of copper wires 800 while satisfying insulation and heat resistance characteristics inside the winding wire. The first insulating material 810 may preferably be implemented as Kapton tape having high insulation and heat resistance, but is not limited thereto.

The second insulating material 820 may preferably be implemented as a flexible silicone tube using a rubber elastomer having a flexible, well-bent property, but is not limited thereto.

The third insulating material 830 may preferably be implemented as a non-halogenated ethylene propylene insulation tube having high insulating properties, but is not limited thereto.

The flexible silicone tube used as the second insulating material 820 has elasticity but is expensive, and the non-concentrated ethylene propylene insulating tube used as the third insulating material 830 is inexpensive but has low elasticity. . In the present disclosure, by using the second insulating material 820 and the third insulating material 830 together, it is possible to have elasticity while satisfying high-voltage and low-voltage insulating properties at low cost.

Hereinafter, a design method of a high frequency transformer according to an embodiment of the present disclosure will be described with reference to FIGS. 9 to 11 .

9 is a flowchart illustrating a method of designing a high frequency transformer according to an embodiment of the present disclosure.

10 is an exemplary diagram for explaining an arrangement space of a high frequency transformer according to an embodiment of the present disclosure.

11 is an exemplary view showing simulation results of operating conditions of a high frequency transformer according to an embodiment of the present disclosure.

In step S900, the size of a space in which a high frequency transformer can be placed is checked, and a core is selected based on this.

The size of the space in which the semiconductor transformer 100 can be mounted on the lower part of the railway vehicle is predetermined, and one AC/DC converter 202 and two first bridges for each power conversion module 200, 210, and 220 After disposing a high voltage stack composed of the circuit 302 and a low voltage stack composed of the two second bridge circuits 306, the high frequency transformer 304 may be placed in the remaining space. there is. For example, referring to FIG. 10 , in one embodiment of the present disclosure, the maximum size of a space in which the high frequency transformer 304 can be placed is 330 mm × 460 mm × 700 mm. Next, a core that can be applied within the dispositionable space of the high frequency transformer 304 is selected. For example, in one embodiment of the present disclosure, 16 U-type cores having a size of 140 mm × 145 mm × 40 mm may be used.

In step S910, the number of turns satisfying preset leakage inductance and turn ratio conditions is calculated.

First, in order to calculate the number of turns of the high frequency transformer 304, an operating condition of the DAB converter must be determined prior to this. A semiconductor transformer 100 according to an embodiment of the present disclosure is composed of 10 power conversion modules 200, 210, and 220 as shown in FIG. 10, and the total maximum power of the semiconductor transformer 100 is Assuming 3 MW, one power conversion module (200, 210 and 220) must be driven with 300 kW, and each high frequency transformer (304) must be driven with 150 kW. Referring to FIG. 11 , it can be seen that the primary and secondary currents (i _p and is _s ) are 180 A and 240 A, respectively, at this operating point. Here, power (P _L ) and primary-side and secondary-side currents (i _p and is _s ) of the high-frequency transformer can be obtained as Equations 18 and 19, respectively.

In addition, operating conditions of the DAB converter applied to an embodiment of the present disclosure are shown in Table 1.

parameters values parameters values parameters values V _p 1,062V φ _v 42 ^o ~ 60 ^o f _s 10 kHz V _s 750V n _a 1.2 to 1.5 L _d 35.0 µH

Referring to Table 1, in an embodiment of the present disclosure, the number of turns such that the leakage inductance of the high frequency transformer 304 satisfies 35.0 μH and the turns ratio has a value between 1.2 and 1.5 is calculated.

In step S920, based on the calculated number of turns, it is checked whether the magnetic flux density (B _c ) of the core is less than a predetermined magnetic saturation level (B _sat ). For example, the magnetic flux density (B _c ) of the core may be confirmed through the above-described equation or finite element method (FEM) simulation. When the magnetic flux density (B _c ) of the core does not satisfy a predetermined condition, the size of the core and/or the number of turns of the primary and secondary windings may be reselected.

In step S930, it is checked whether the core of the high frequency transformer 304 satisfies a preset temperature performance. For example, through simulation, it may be determined whether the temperature increase (ΔT _co ) of the core is less than a preset threshold value. At this time, the threshold may be set to 110 °C in consideration of the temperature (150 °C) affecting the winding insulation coating.

In step S940, the thicknesses (D _t ) of the primary and secondary windings are determined.

First, considering the coil current, the thickness of the copper wire 800 is selected. In one embodiment of the present disclosure, considering that the primary current (I _p ) and the secondary current (I _s ) are 180 A and 240 A, respectively, the thickness of the copper wire 800 included in the primary winding and the secondary winding can be selected as 44 mm ² and 52 mm ² , respectively.

Next, in consideration of required insulation performance, the diameter (D _c ) of the first insulating material 810 and the thicknesses (D _i ) of the second insulating material 820 and the third insulating material 830 are determined, and Determine the molding size of the epoxy insulator 430 to be applied. In one embodiment of the present disclosure, for 60 kV class insulation, the thicknesses of the primary and secondary windings determined in consideration of the insulation margin are shown in Table 2.

Primary [mm] Secondary D _c D _i D _t D _c D _i D _t 13 7 27 15 7 29

In step S950, it is checked whether the primary winding and the secondary winding can be mounted within the window area of the core. When the primary and secondary windings are not mounted within the window area of the core, the thicknesses of the primary and secondary windings may be re-selected.

In step S960, it is checked whether the winding of the high frequency transformer 304 satisfies a preset temperature performance. For example, through simulation, it may be confirmed whether the temperature increase (ΔT _cp ) of the winding is less than a preset threshold. At this time, the threshold may be set to 110 °C in consideration of the temperature (150 °C) affecting the winding insulation coating.

In step S970, it is checked whether the high frequency transformer 304 satisfies a predetermined insulation performance. For example, through simulation, it may be confirmed whether the electric field of the high frequency transformer 304 is less than a preset threshold value. At this time, considering the air dielectric breakdown electric field, the threshold value may be set to 20 kV/mm. When the high frequency transformer 304 does not satisfy the predetermined insulation performance, the thickness D _i of the second insulation material 820 and the third insulation material 830 may be increased to improve insulation performance.

Meanwhile, the method for designing the high frequency transformer according to FIG. 9 is performed by a design device, and the design device may be executed on a computing device. The design device may include a computer readable storage having instructions stored therein connected to the processor and performing each function by one or more processors available to the computing device.

Hereinafter, an experimental example for confirming the performance of the high frequency transformer 304 according to an embodiment of the present disclosure will be described with reference to FIGS. 12 to 19 . In the experimental example, parameters according to Tables 1 and 2 were applied.

12 is an exemplary diagram schematically illustrating a simulation model for a high frequency transformer according to an embodiment of the present disclosure.

13 to 19 are exemplary diagrams illustrating simulation results of a high frequency transformer according to an embodiment of the present disclosure.

12 shows various combinations of the number of turns of the primary winding and the number of turns of the secondary winding having a turn ratio between 1.2 and 1.5. In FIG. 12 , a winding marked in red represents a primary-side winding, and a winding marked in blue represents a secondary-side winding. In the experimental example, 3D finite element method (FEM) simulation was performed using the simulation model shown in FIG. 12 to confirm the results shown in Equations 1 to 17.

13 shows simulation results for leakage inductance (L _d ) according to the number of turns (N _p ) of the primary side winding and derivation results using equations. In the experimental example, it can be confirmed that the number of turns (N _p ) of the primary winding closest to the required leakage inductance condition (Ld = 35.0 μH) is 8. Referring to FIG. 12 , the corresponding number of turns (N _s ) of the secondary winding is 6.

14 shows simulation results of the magnetic flux density (B _c ) of the core according to the number of turns (N _p ) of the primary winding and derivation results using equations. In the experimental example, when the number of turns (N _p ) of the primary winding is less than 5, the core is saturated, and when the number of turns (N _p ) of the primary winding is 8, the magnetic flux density (B _c ) of the core is preset It can be seen that it is smaller than the core saturation level (B _sat = 0.3 T).

15 shows the magnetic field strength for each position calculated according to Equations 9 to 11 and simulation results thereof. Referring to FIG. 15 , it can be seen that the magnetic field strength for each position calculated according to Equations 9 to 11 agrees well with the simulation result.

16A and 16B show simulation results of core loss of a high frequency transformer according to a comparative embodiment and a high frequency transformer according to an embodiment of the present disclosure. Since the high frequency transformer according to an embodiment of the present disclosure has a structure in which a secondary winding is separated, a primary magnetic field inside the core can be effectively canceled by a secondary magnetic field. In this simulation, the core loss of the high frequency transformer according to an embodiment of the present disclosure was 95.1 W, which was improved by about 7.7% compared to the core loss of 103.0 W of the high frequency transformer according to the comparative embodiment.

FIG. 17 shows simulation results of loss of a high-frequency transformer according to the number of turns (N _p ) of a primary winding and derivation results using equations. Referring to FIG. 17 , it can be seen that as the number of turns (N _p ) of the primary winding increases, the core loss decreases while the winding loss increases. In the experimental example, the number of turns (N _p ) of the primary winding that minimizes the loss of the high frequency transformer is 8, and the number of turns (N _s ) of the secondary winding corresponding to this is 6.

18A and 18B show simulation results of temperature characteristics of a high-frequency transformer at an optimum number of turns. In this simulation, the maximum temperatures of the core and winding were analyzed to be 116.6 °C and 95.2 °C, respectively.

19 shows simulation results of electric field characteristics of a high-frequency transformer at an optimum number of turns. In this simulation, when 60 kV is applied to the primary side and 0 V (GND) is applied to the secondary side and the core, it can be confirmed that the electric field becomes 20 kV/mm or less at all points.

The above description is merely an example of the technical idea of the present embodiment, and various modifications and variations can be made to those skilled in the art without departing from the essential characteristics of the present embodiment. Therefore, the present embodiments are not intended to limit the technical idea of the present embodiment, but to explain, and the scope of the technical idea of the present embodiment is not limited by these embodiments. The scope of protection of this embodiment should be construed according to the claims below, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of rights of this embodiment.

100: semiconductor transformer
102 AC/DC converter 104 DC/DC converter
110: inverter for motor driving
200, 210 and 220: power conversion module
202 AC/DC converter 204 DC/DC converter
300: first DC / DC converter 310: second DC / DC converter
302 first bridge circuit 304 high frequency transformer
306: second bridge circuit
400: core 410: primary side winding
420: secondary side winding 422: secondary side upper winding
424: secondary side lower winding 430: epoxy insulator

Claims (12)

In a semiconductor transformer including an AC / DC converter and a DC / DC converter,
The DC/DC converter,
A high frequency transformer including a core, a primary side winding and a secondary side winding;
a first bridge circuit connected between an AC/DC converter and the primary side winding and converting a direct current voltage into a high frequency alternating current; and
A second bridge circuit connected between the secondary side winding and the first output terminal and outputting a DC voltage;
The secondary winding,
a secondary-side upper winding wound around one side of the primary-side winding; and
Characterized in that, a semiconductor transformer comprising a secondary-side lower winding wound on the other side of the primary-side winding. According to claim 1,
The number of turns of the primary winding and secondary winding is
A semiconductor transformer, characterized in that the leakage inductance and turn ratio of the high frequency transformer are selected to satisfy predetermined conditions. According to claim 2,
The primary side winding and the secondary side winding each constitute a plurality of winding layers,
The number of turns of the primary winding and secondary winding is
A semiconductor transformer characterized in that the leakage inductance of the high frequency transformer is selected based on the following equation to satisfy a predetermined condition.

Where, L _l,p is the primary leakage inductance, L _l,s is the secondary leakage inductance, I _p is the primary current, I _s is the secondary current, b _w is the width of the window area of the core, l _m is the average length in each turn, m _n is the number of winding layers of the primary and secondary windings, h _p is the thickness of the primary winding, h _s is the thickness of the secondary winding, h _n is the spacing between windings, n _{p ,j} is the number of turns for each layer of the primary winding, and n _s,j is the number of turns for each layer of the secondary winding. According to claim 2,
The number of turns of the primary winding and secondary winding is
Characterized in that, based on a predefined geometry of the core, the magnetic flux density of the core is selected to be less than a predetermined magnetic saturation level. According to claim 4,
The number of turns of the primary winding and secondary winding is
Based on the following equation, a semiconductor transformer characterized in that the magnetic flux density of the core is selected to be less than a predetermined magnetic saturation level.

Here, N _p is the number of turns of the primary winding, n _a is the turns ratio of the high frequency transformer, L _l,p is the primary leakage inductance, L _l,s is the secondary leakage inductance, V _p is the primary voltage, V _s is the secondary voltage, w _s is the switching frequency, B _sat is the magnetic saturation level, and A _c is the magnetic flux cross-section of the core. According to claim 1,
Each of the primary side winding and the secondary side winding,
a plurality of copper wires;
A first insulating material surrounding and fixing the plurality of copper wires;
a second insulating material surrounding the first insulating material; and
A third insulating material surrounding the second insulating material
Characterized in that, a semiconductor transformer comprising a. According to claim 6,
The second insulating material is a flexible silicon tube,
The third insulating material is a non-concentrated ethylene propylene insulating tube, characterized in that, a semiconductor transformer. A high frequency transformer including a core, a primary winding, and a secondary winding, wherein the secondary winding includes a secondary upper winding wound on one side of the primary winding and a secondary lower winding winding on the other side of the primary winding. As a design method of
selecting a size of the core based on a size of a space in which the high frequency transformer can be disposed;
selecting the number of turns of the primary winding and the secondary winding so that the leakage inductance and turn ratio of the high frequency transformer satisfy predetermined conditions; and
Process of determining the thickness of the primary side winding and the secondary side winding
A design method of a high-frequency transformer comprising a. According to claim 8,
The process of selecting the number of turns of the primary winding and the secondary winding,
A method for designing a high-frequency transformer, characterized in that the number of turns such that the leakage inductance of the high-frequency transformer satisfies a predetermined condition is selected based on the following equation.

Where, L _l,p is the primary leakage inductance, L _l,s is the secondary leakage inductance, I _p is the primary current, I _s is the secondary current, b _w is the width of the window area of the core, l _m is the average length in each turn, m _n is the number of winding layers of the primary and secondary windings, h _p is the thickness of the primary winding, h _s is the thickness of the secondary winding, h _n is the spacing between windings, n _{p ,j} is the number of turns for each layer of the primary winding, and n _s,j is the number of turns for each layer of the secondary winding. According to claim 8,
determining whether a magnetic flux density of the core is less than a predetermined magnetic saturation level, based on a predetermined geometry of the core; and
reselecting at least one of the size of the core and the number of turns of the primary winding and the secondary winding when it is determined that the magnetic flux density of the core is not less than a predetermined magnetic saturation level;
A design method of a high frequency transformer, characterized in that it further comprises. According to claim 10,
The verification process is
A method for designing a high-frequency transformer, characterized in that it is checked whether the magnetic flux density of the core is less than a predetermined magnetic saturation level based on the following equation.

Here, N _p is the number of turns of the primary winding, n _a is the turns ratio of the high frequency transformer, L _l,p is the primary leakage inductance, L _l,s is the secondary leakage inductance, V _p is the primary voltage, V _s is the secondary voltage, w _s is the switching frequency, B _sat is the magnetic saturation level, and A _c is the magnetic flux cross-section of the core. According to claim 8,
Each of the primary and secondary windings may include a plurality of copper wires, a first insulating material surrounding and fixing the plurality of copper wires, and a second insulating material surrounding the first insulating material; And a third insulating material surrounding the second insulating material,
The process of determining the thickness,
The thickness of the copper wire, the diameter of the first insulating material, and the thicknesses of the second insulating material and the third insulating material are determined based on the predetermined operating conditions of the transformer and the predetermined required insulation performance. design method.

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