KR102685954B1 - Multilevel wireless power transmission system and manufacturing method thereof - Google Patents

Abstract

In the multi-level wireless power transmission system, an excitation coil connected to an AC power source, a power supply coil arranged to be magnetically coupled to the excitation coil, a current collection coil spaced a certain distance from the power supply coil and having magnetic coupling, and an empty space inside. It is formed and includes a ferrite core on one side of which the winding of the excitation coil is wound, and a molding portion in which the winding of the excitation coil and the ferrite core are treated with epoxy molding.

Description

Multilevel wireless power transmission system and manufacturing method thereof {MULTILEVEL WIRELESS POWER TRANSMISSION SYSTEM AND MANUFACTURING METHOD THEREOF}

The present invention relates to a multi-level wireless power transmission system and a method of manufacturing the same.

Wireless power transmission technology is a method of easily transmitting energy wirelessly to transportation such as cars, buses, or trains, just as computers and smartphones exchange data through Wi-Fi or Bluetooth.

1 is a multi-level wireless power transmission system according to the prior art. Referring to FIG. 1, the conventional wireless power transmission system 10 converts 60Hz AC voltage (current) into DC voltage (current) using a plurality of rectifiers (10).

The conventional wireless power transmission system 10 connects the converted DC voltage to a resonance inverter 20, and magnetically combines the excitation coil 30 and the power supply coil 40 connected to each output terminal of the resonance inverter 20. Power is transmitted using.

Specifically, when a current of the same magnitude and phase is passed through the resonance inverter 20 to the plurality of excitation coils 30, a magnetic field is generated in the plurality of excitation coils 30. The magnetic field generated through the plurality of excitation coils 30 generates large induced voltage and current through the feeding coil 40, which is strongly magnetically coupled. The power supply coil 40 generates a magnetic field again, and finally transfers the magnetic field to the current collection coil 50, which is weakly magnetically coupled to a certain distance apart.

In the conventional wireless power transmission system 10, for example, when connected to a medium voltage system of 22.9 kV or 25 kV, the potential difference between the excitation coil 30 and the power supply coil 40 is limited to a maximum of 40 kV or more. However, in order to prevent dielectric breakdown between the excitation coil 30 and the power supply coil 40 and ensure safety, it is necessary to secure an dielectric strength of 70 kV or more.

Korean Patent Publication No. 10-2021-0149197 (published on December 8, 2021) Korean Patent Publication No. 10-2018-0052026 (published May 17, 2018)

The present invention is intended to solve the problems of the prior art described above, and seeks to provide an excitation coil that can stably secure an effectively improved dielectric strength compared to the prior art.

However, the technical challenges that this embodiment aims to achieve are not limited to the technical challenges described above, and other technical challenges may exist.

As a means for achieving the above-mentioned technical problem, an embodiment of the present invention provides a multi-level wireless power transmission system, comprising: an excitation coil connected to an AC power source; a power supply coil arranged to be magnetically coupled to the excitation coil; a current collecting coil that is spaced a certain distance from the power supply coil and has magnetic coupling; a ferrite core that forms an empty space inside, and on one side of which the winding of the excitation coil is wound; and a molding portion in which epoxy molding is applied to the winding of the excitation coil and the ferrite core.

The ferrite core includes a core housing in the shape of a rectangular parallelepiped forming the empty space, and the core housing is composed of a lower surface, an upper surface, and a side wall, and an air gap may exist between the upper surface and the side wall.

Additionally, the gap may be made of acrylic material coated with conductive paint and may be inserted between the upper surface and the side wall to a thickness less than a preset maximum thickness.

In addition, the molding unit processes the ferrite core with primary epoxy molding, winds the winding of the excitation coil around the ferrite core treated with the primary epoxy molding, and coils 2 on the winding of the excitation coil wound around the ferrite core. It may be characterized as being manufactured by processing car epoxy molding.

Additionally, the molding unit may be characterized in that it creates a vacuum state between the winding of the excitation coil and the ferrite core.

Another embodiment of the present invention is a method of manufacturing a multi-level wireless power transmission system, wherein a power supply coil is arranged to be magnetically coupled to an excitation coil connected to an AC power source, and a current collection coil is magnetically coupled to the power supply coil. Arranging them to be spaced a certain distance apart, winding the winding of the excitation coil around one side of a ferrite core forming an empty space therein, and processing the winding of the excitation coil and the ferrite core with epoxy molding; may include.

Processing the winding of the excitation coil and the ferrite core with epoxy molding may include processing the ferrite core with primary epoxy molding; Winding the winding of the excitation coil around the ferrite core treated with the primary epoxy molding; and processing secondary epoxy molding on the winding of the excitation coil wound around the ferrite core.

The above-described means for solving the problem are merely illustrative and should not be construed as intended to limit the present invention. In addition to the exemplary embodiments described above, there may be additional embodiments described in the drawings and detailed description of the invention.

According to one of the means for solving the problems of the present invention described above, securing an dielectric strength of 70 kV or more between the excitation coil and the power supply coil to enable stable operation in the medium voltage system, that is, preventing insulation breakdown between the excitation coil and the power supply coil, and A multi-level wireless power transmission system that can ensure safety can be provided.

Therefore, 55kV dielectric strength can be secured to apply a multi-level wireless power transmission system to the 22.9kV and 25kV medium voltage systems.

In addition, since epoxy is applied only to the upper part of the exciting coil and core, molding work is easy, which has the advantage of simple assembly and manufacturing.

Additionally, since the power supply coil is not molded, it can have a structure that is advantageous for cooling the power supply coil through which a large current flows.

Therefore, the excitation coil can be designed quickly using the excitation coil insulation model, and maintenance in case of failure can be simple.

1 is a wireless power transmission system according to the prior art.
Figure 2 is a plan view of a multi-level wireless power transmission system according to an embodiment of the present invention.
Figure 3 is an exemplary cross-sectional view for explaining an excitation coil core according to an embodiment of the present invention.
Figure 4 is an exemplary diagram for explaining how a power supply coil and an excitation coil are installed in an excitation coil core according to an embodiment of the present invention.
Figure 5 shows a weak insulation breakdown path of an excitation coil insulation structure according to an embodiment of the present invention.
Figure 6 is an equivalent circuit diagram of an excitation coil insulation structure according to an embodiment of the present invention.
Figure 7 shows an insulation analysis model of an excitation coil insulation structure according to an embodiment of the present invention.
FIG. 8 graphically shows the intensity of the electric field in the weak insulation breakdown path obtained with an insulation analysis model according to an embodiment of the present invention.
Figure 9 is an exemplary diagram for explaining simulation results of electric field intensity distribution according to an embodiment of the present invention.

Below, with reference to the attached drawings, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein. In order to clearly explain the present invention in the drawings, parts unrelated to the description are omitted, and similar parts are given similar reference numerals throughout the specification.

Throughout the specification, when a part is said to “include” a certain element, this means that it may further include other elements rather than excluding other elements, unless specifically stated to the contrary. In addition, when a part is said to be "connected" to another part throughout the specification, this means not only when it is directly connected, but also when it is connected through another member in the middle, or electrically between other elements in the middle. This also includes cases where they are connected. Furthermore, throughout the specification of the present application, when a member is said to be located “on” another member, this includes not only the case where a member is in contact with another member, but also the case where another member exists between the two members.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the attached drawings.

Figure 2 is a plan view of a multi-level wireless power transmission system according to an embodiment of the present invention. Referring to FIG. 2, the multi-level wireless power transmission system 200 may include a plurality of AC power sources 210 and 220, a plurality of excitation coils 230, a power supply coil 240, and a plurality of current collection coils 250. You can.

As shown in FIG. 2, the multi-level wireless power transmission system 200 may include a plurality of current collecting coils 250. For example, the multi-level wireless power transmission system 200 can transmit power from one power supply coil 240 to a plurality of current collection coils 250 at the same time.

At this time, in the process of transferring power from one power supply coil 240 to a plurality of current collection coils 250, the amount of power delivered to each current collection coil 250 may be different depending on the load.

Even with such load uncertainty, the voltages of the plurality of rectifiers 210 in the plurality of AC power sources 210 and 220 must all be the same, and to this end, the outputs of the plurality of inverters 220 must all be the same to enable stable operation of the system.

Therefore, the multi-level wireless power transmission system 200 according to the present invention can eliminate load uncertainty by using a plurality of exciting coils 230, one feeding coil 240, and a plurality of current collecting coils 250. .

In the multi-level wireless power transmission system 200, the plurality of inverters 220 are each connected to the excitation coil 230 and connected to the current collection coil 250 and the load via the power supply coil 240, so that the plurality of inverters (220) can output the same current regardless of the number or status of loads.

Hereinafter, with reference to FIGS. 3 to 8, the configuration of the multi-level wireless power transmission system 200 will be looked at in more detail. FIG. 3 shows an insulating structure of an excitation coil included in the multi-level wireless power transmission system 200 according to an embodiment.

Specifically, Figure 3 shows an exciting coil insulation structure for securing medium voltage insulation strength. Since the operating frequency of the multi-level wireless power transmission system 200 is high, tens of KHz or more, the windings of the excitation coil 230 and the power supply coil 240 can be made using Litz-wire. This Litz-wire can be wrapped with Teflon or urethane coating with a thickness of 0.5 to 1 mm. Additionally, a ferrite core 231 was used to strengthen the magnetic coupling between the excitation coil 230 and the power supply coil 240. In the ferrite core 231 shown in FIG. 3, the part located close to the excitation coil 230 is called the upper ferrite core 231a, and the part opposite to it is called the lower ferrite core 231b. This ferrite core 231 requires an air gap 232 having a low permeability to prevent magnetic saturation. This gap may be made of a material such as acrylic and may be inserted between the upper ferrite core 231a and the lower ferrite core 231b to a thickness of several mm or less.

However, when a non-conductive material such as acrylic is inserted between the cores 231, a large potential difference occurs between the upper ferrite core 231a and the lower ferrite core 231b when a high voltage is applied to the excitation coil 230. As a result, insulation breakdown may occur in the voids 232a and 232b, so conductive paint can be applied to acrylic to prevent this. The cavity 232, which is made of acrylic with conductive paint applied, becomes a conductor with a resistance of hundreds of ohms (conducted pain coated acrylic plate), so it is insulated by reducing the potential difference between the upper ferrite core 231a and the lower ferrite core 231b. Destruction can be prevented.

If air exists between the winding of the exciting coil 230 and the core 231, when a high voltage is applied to the exciting coil 230, insulation is broken down in the air, so the winding of the exciting coil 230 and the core 231 ) and includes an epoxy molding part 234 to create a vacuum state between them.

Here, the epoxy molding part 234 may be performed twice. First, epoxy molding is initially performed on the core 231 to increase the distance between the core 231 and the winding. Next, the winding is wound on it, and then secondary epoxy molding is performed. Therefore, a vacuum state can be created around the winding.

In this case, since there should be no physical contact between the core 231 and the power supply coil 240, a bobbin 236 made of ABS printed with a 3D printer can be used to support the core of the power supply coil outside the core. For this, please refer to Figure 4.

Figure 4 is an exemplary diagram for explaining how a power supply coil and an excitation coil are installed in an excitation coil core. Referring to FIG. 4, it can be seen that the power supply coil 240 passes through the center of the empty space inside the core 231. As a result, the power supply coil 240 and the core 231 can be formed into a structure in which the power supply coil 240 and the core 231 are spaced several centimeters or more apart through air without physical contact.

Figure 5 shows a weak insulation breakdown path of an excitation coil insulation structure according to an embodiment.

Since insulation breakdown occurs through the weakest path, sufficient dielectric strength must be ensured in all paths.

For example, the first path (path1) refers to a path leading from the excitation coil 230 to the power supply coil 240 by going around the upper ferrite coil 231a, the air gap 232a, and the lower ferrite coil 231b. .

The second path (path2) is a path that leads from the excitation coil 230 to the power supply coil 240 through the upper ferrite coil 231a, the air gap 232a, and a part of the lower ferrite coil 231b.

The third path (path3) is a path directly leading from the excitation coil 230 to the power supply coil 240.

Accordingly, the excitation coil insulating structures of FIGS. 2 and 3 are designed to ensure sufficient dielectric strength in all of the first to third paths, so that the power supply coil 240 travels several cm or more through the air without physical contact with the core 231. An excitation coil insulating structure formed in a spaced apart structure can be provided.

Next, Figure 6 shows the equivalent circuit of the excitation coil insulation structure.

A medium voltage is applied between the excitation coil 230 and the power supply coil 240, and the connection between each material can be expressed as capacitive coupling. The insulation analysis model of Figure 7 was developed to calculate the electric field strength and lead strength by applying Gauss's law to this equivalent circuit.

In the cylindrical coordinate system, the winding (copper EX) of the excitation coil 230 and the winding (copper TX) of the power supply coil 240, which are two conductors to which voltage is applied, are combined at the central Z axis. Afterwards, adjacent materials are arranged in the ρ direction in the order of proximity to the conductors (copper).

Specifically, as shown in Figure 7, when two materials, epoxy and air, are placed outside the Teflon (EX, TX) sheath, air, which has weaker dielectric strength, is placed inside, and epoxy is placed outside it. can do.

Once the arrangement is complete, the intensity of the electric field can be calculated by applying a high voltage to the centralmost conductor and 0V to the outermost ferrite.

To calculate the intensity of the electric field in the cylindrical coordinate system insulation model of FIG. 7, the total charge Q of the model is first calculated using <Equation 1> below.

<Formula 1>

Afterwards, using the total charge Q calculated through <Equation 1>, for By calculating , the strength of the electric field in each material can be calculated. Therefore, when the calculated electric field strength exceeds the dielectric strength of each material, it can be determined that dielectric breakdown has occurred.

Figure 8 shows the intensity of the electric field in the weak insulation breakdown path calculated with the insulation analysis model.

The first path (path1) refers to a path from the excitation coil 230 around the upper ferrite coil 231a, the air gap 232a, and the lower ferrite coil 231b to the power supply coil 240, Figure 8 It is shown as the intensity of the electric field of Path#1.

The second path (path2) refers to a path leading from the excitation coil 230 to the power supply coil 240 through the upper ferrite coil 231a, the air gap 232a, and a portion of the lower ferrite coil 231b, It is shown as the intensity of the electric field of Path #2 in FIG. 8.

The third path (path3) refers to a path directly leading from the excitation coil 230 to the power supply coil 240, and is shown as the electric field strength of Path#3.

Figure 9 is an exemplary diagram for explaining simulation results of electric field intensity distribution according to an embodiment of the present invention. Referring to FIG. 9, the electric field intensity distribution of the multi-level wireless power transmission system 100 can be confirmed.

The simulation results shown in Figure 9 show that the potential difference between the power supply coil and the excitation coil is In this case, the electric field intensity distribution around the power supply coil and the excitation coil is. The maximum electric field intensity is Below, it can be confirmed that since it is smaller than the dielectric breakdown strength of air, the dielectric strength required for the wireless power transmission system of the medium voltage system can be secured.

The description of the present invention described above is for illustrative purposes, and those skilled in the art will understand that the present invention can be easily modified into other specific forms without changing the technical idea or essential features of the present invention. will be. Therefore, the embodiments described above should be understood in all respects as illustrative and not restrictive. For example, each component described as single may be implemented in a distributed manner, and similarly, components described as distributed may also be implemented in a combined form.

The scope of the present invention is indicated by the claims described below rather than the detailed description above, and all changes or modified forms derived from the meaning and scope of the claims and their equivalent concepts should be construed as being included in the scope of the present invention. do.

100: Multilevel wireless power transmission system
230: female coil
231: Ferrite coil
231a: upper ferrite coil
231b: lower ferrite coil
232a, 232b: void
240: power supply coil
234: Epoxy molding part

Claims (8)

In a multi-level wireless power transmission system,
Excitation coil connected to AC power;
a power supply coil arranged to be magnetically coupled to the excitation coil;
a current collecting coil that is spaced a certain distance from the power supply coil and has magnetic coupling;
a ferrite core that forms an empty space inside, and on one side of which the winding of the excitation coil is wound; and
a molding portion in which epoxy molding is applied to the winding of the excitation coil and the ferrite core; A multi-level wireless power transmission system comprising:
According to claim 1,
The ferrite core is,
It includes a core housing in the shape of a rectangular parallelepiped forming the empty space,
The core housing is,
It consists of a lower surface, a top surface, and a side wall,
A multi-level wireless power transmission system wherein an air gap exists between the top surface and the side wall.
According to claim 2,
The air gap is made of acrylic material coated with conductive paint and is inserted between the upper surface and the side wall to a thickness less than a preset maximum thickness.
According to claim 1,
The molding part,
Processing the ferrite core with primary epoxy molding, winding the winding of the exciting coil around the ferrite core treated with the primary epoxy molding, and treating the winding of the exciting coil wound around the ferrite core with secondary epoxy molding. A multilevel wireless power transmission system, characterized in that manufactured.
According to claim 4,
The molding part,
A multi-level wireless power transmission system, characterized in that creating a vacuum state between the winding of the excitation coil and the ferrite core.
In a method of manufacturing a multi-level wireless power transmission system,
Arrange the power supply coil so that it is magnetically coupled to the excitation coil connected to the AC power source,
Arranging a current collecting coil having magnetic coupling with the power supply coil to be spaced a certain distance apart,
The winding of the excitation coil is wound around one side of the ferrite core forming an empty space inside,
Processing the winding of the excitation coil and the ferrite core with epoxy molding; Method for manufacturing a multi-level wireless power transmission system comprising a.
According to claim 6,
The ferrite core is,
It includes a core housing in the shape of a rectangular parallelepiped forming the empty space,
The core housing is,
It consists of a lower surface, a top surface, and a side wall,
A method of manufacturing a multi-level wireless power transmission system, characterized in that an air gap exists between the upper surface and the side wall.
According to claim 7,
The step of processing the winding of the excitation coil and the ferrite core with epoxy molding,
Processing the ferrite core with primary epoxy molding;
Winding the winding of the excitation coil around the ferrite core treated with the primary epoxy molding; and
Processing secondary epoxy molding on the winding of the excitation coil wound around the ferrite core; A method of manufacturing a multi-level wireless power transmission system comprising a.

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