JP6305728B2 - Coil unit and power transmission system - Google Patents

Description

  The present invention relates to a technical field of a coil unit used for non-contact power transmission and a power transmission system including the coil unit.

  As this type of coil unit, for example, a coil unit including a plurality of coils in order to reduce a leakage magnetic field, and one coil among the plurality of coils and another coil among the plurality of coils are There has been proposed a coil unit arranged so that the generated magnetic field has an opposite phase (see Patent Document 1).

  A technique has been proposed in which a plurality of transformers having a double-sided H-shaped core structure are connected to increase the capacity of the transformer (see Non-Patent Document 1).

Japanese Patent No. 5139469

Toru Fujita, Tomohiro Nakayama, Hiroyoshi Kaneko, Shigeru Abe, Tomio Yasuda, Akira Suzuki: “High-capacity non-contact power transformer for electric vehicles with multiple modules”, 2012 IEEJ Conference on Industrial Applications, No . 4-9, pp. IV111-IV114 (2012, 8, 23)

  In the coil unit described in Patent Document 1 or a circular coil (circular core one-side winding structure), a technical problem that power transmission efficiency is reduced unless the central axes of coils opposed to each other are coaxial. There is. When this type of coil unit is used in, for example, a battery charging system mounted on an electric vehicle, the alignment accuracy of the coil unit greatly depends on the driving skill of the vehicle driver. Then, there is a possibility that the above technical problem appears remarkably.

  The present invention has been made in view of the above-described problems, for example, and it is an object to provide a coil unit and a power transmission system that can suppress a decrease in power transmission efficiency due to a positional shift between the coil units. To do.

In order to solve the above problems, the coil unit of the present invention is part of a power transmission system capable of receiving power in a non-contact manner from one coil unit, and is electrically connected to a load having an impedance Z. A first coil having a central axis along one direction and a magnetic field opposite to a magnetic field formed by the first coil when the coil unit is operated; A second coil electrically connected to the first coil and arranged coaxially with the central axis, and coaxial with the central axis and the first coil and the second coil. And a third coil that is not electrically connected to any of the first coil and the second coil, and a coupling coefficient between the coil unit and the one coil unit. K, resonance circumference As the number omega, combined inductance value L2 of the first coil and the second coil is configured so as to satisfy the formula 1.

In order to solve the above problems, a power transmission system of the present invention is a non-contact power transmission system including a power feeding device and a power receiving device that can perform non-contact power transmission, and the power feeding device includes a power feeding coil unit. And a power supply unit that is electrically connected to the power supply coil unit and supplies power of a predetermined frequency to the power supply coil unit, and the power reception device is disposed opposite to the power supply coil unit. A coil unit; and a load electrically connected to the power receiving coil unit, wherein the power feeding coil unit includes a first power feeding coil having a first central axis along one direction, and the power feeding coil. When the unit is in operation, it is electrically connected to the first feeding coil so as to form a magnetic field opposite to the magnetic field formed by the first feeding coil. A second feeding coil that is disposed on a first center axis and coaxially to said first center axis and coaxially, and, between the first feed coil and the second feed coil And a third power supply coil that is not electrically connected to any of the first power supply coil and the second power supply coil, and the third power supply coil includes the third power supply coil. The resonance point of the power feeding coil is configured to coincide with the driving frequency of the power supply means, and the power receiving coil unit has a second center different from the first central axis along the one direction. The first power receiving coil is electrically connected to the first power receiving coil so as to form a magnetic field opposite to the magnetic field formed by the first power receiving coil when the power receiving coil unit is operated. Connected to the second central axis and arranged coaxially with the second central axis. A second power-receiving coil, the second central axis coaxial with, and, disposed between said first receiving coil the second receiving coil, said first receiving coil and a second A third power receiving coil that is not electrically connected to any one of the power receiving coils, wherein the third power receiving coil has a resonance point of the third power receiving coil to drive the power supply means. The first power receiving unit is configured such that the driving frequency of the power supply unit is fs, the impedance of the load is Z, and the coupling coefficient between the power feeding coil unit and the power receiving coil unit is k. The combined inductance value L2 of the coil and the second power receiving coil is configured to satisfy Formula 2.

  The effect | action and other gain of this invention are clarified from the form for implementing demonstrated below.

It is a conceptual diagram which shows the outline | summary of the electric power transmission system which concerns on 1st Example. It is a perspective view which shows the coil unit which concerns on 1st Example. It is a characteristic view which shows an example of the relationship between the air gap of the coil unit which concerns on 1st Example, and a coupling coefficient. It is a characteristic view which shows an example of the relationship between the inductance of a receiving coil, and transmission efficiency. It is a conceptual diagram which shows an example of the magnetic field when position shift arises in a power transmission coil and a receiving coil. It is a characteristic view which shows an example of the relationship between position shift and a coupling coefficient. It is a characteristic view which shows an example of a radiation magnetic field. It is a conceptual diagram which shows the outline | summary of the electric power transmission system which concerns on 2nd Example. It is a perspective view which shows the coil unit which concerns on 2nd Example. It is a conceptual diagram which shows the other example of a magnetic field when position shift arises in a power transmission coil and a receiving coil. It is a characteristic view which shows an example of the relationship between the position shift to a X direction, and a coupling coefficient.

  Embodiments according to the coil unit and the power transmission system of the present invention will be described.

(Coil unit)
The coil unit according to the embodiment is a coil unit that constitutes a part of a power transmission system capable of receiving power in a non-contact manner from one coil unit and is electrically connected to a load having an impedance Z.

  The coil unit forms a first coil having a central axis along one direction and a magnetic field opposite to the magnetic field formed by the first coil during operation of the coil unit. A second coil electrically connected to the first coil and disposed coaxially with the central axis.

  Particularly in this embodiment, the combined inductance value L2 of the first coil and the second coil is configured to satisfy the following relational expression.

ここで、“ｋ”は当該コイルユニット及び一のコイルユニット間の結合係数であり、“ω”は共振周波数である。

Here, “k” is a coupling coefficient between the coil unit and one coil unit, and “ω” is a resonance frequency.

  The coil unit according to the present embodiment includes a first coil having a central axis along one direction, and a second coil arranged coaxially with the central axis. . The first coil and the second coil are configured and electrically connected to each other so as to form opposite magnetic fields when the coil unit operates.

  Here, the first coil and the second coil according to the present embodiment are so-called double-sided coils. This so-called double-sided coil is less susceptible to positional displacement in the direction intersecting with the direction in which the central axis extends than the so-called single-sided coil.

  In addition, when the combined inductance value L2 satisfies the above relational expression, it has been found by the inventor's research that the power transmission efficiency between the coil unit and one coil unit is relatively high. In addition, as described above, during the operation of the coil unit, the direction of the magnetic field generated around the first coil and the direction of the magnetic field generated around the second coil are opposite to each other. The radiation magnetic field to the surroundings of the

  By configuring the first coil and the second coil to have the same shape and the same inductance, the effect of reducing the radiation magnetic field can be further increased.

  In one aspect of the coil unit according to the embodiment, the coil unit is disposed coaxially with the central axis of the first coil and between the first coil and the second coil. A third coil that is not electrically connected to either the coil or the second coil is further provided.

  According to this aspect, compared to the case of only the first coil and the second coil, it is possible to reduce the influence of the positional deviation in the direction in which the central axis of the coil unit extends, which is very advantageous in practice. is there.

  In this aspect, the third coil is configured to resonate with the first coil and the second coil during the operation of the coil unit.

  If comprised in this way, even if it is a case where the said coil unit has shifted | deviated to the direction where a central axis extends with respect to said one coil unit, since the 3rd coil functions as reflection amplification, the said coil unit And a reduction in power transmission efficiency between the one coil unit can be suppressed.

(Power transmission system)
The power transmission system according to the embodiment is a non-contact power transmission system including a power feeding device and a power receiving device capable of non-contact power transmission.

  The power supply apparatus includes a power supply coil unit and power supply means that is electrically connected to the power supply coil unit and supplies power of a predetermined frequency to the power supply coil unit.

  The feeding coil unit has a first feeding coil having a first central axis along one direction, and a magnetic field opposite to the magnetic field formed by the first feeding coil during operation of the feeding coil unit. And a second power supply coil that is electrically connected to the first power supply coil and disposed coaxially with the first central axis.

  The power receiving apparatus includes a power receiving coil unit disposed to face the power feeding coil unit, and a load electrically connected to the power receiving coil unit.

  The power receiving coil unit is formed by a first power receiving coil having a second central axis that is different from the first central axis along one direction, and the first power receiving coil during operation of the power receiving coil unit. A second power receiving coil that is electrically connected to the first power receiving coil and disposed coaxially with the second central axis so as to form a magnetic field opposite to the magnetic field.

  In this embodiment, in particular, the combined inductance value L2 of the first power receiving coil and the second power receiving coil is configured to satisfy the following relational expression.

ここで、“ｆｓ”は電力供給手段の駆動周波数であり、“Ｚ”は負荷のインピーダンスであり、“ｋ”は給電コイルユニット及び受電コイルユニット間の結合係数である。

Here, “fs” is the driving frequency of the power supply means, “Z” is the impedance of the load, and “k” is the coupling coefficient between the feeding coil unit and the receiving coil unit.

  When the combined inductance value L2 satisfies the above relational expression, the input resistance Rin of the feeding coil unit is expressed by the following approximate expression.

ここで、“Ｌ１”は、第１の給電コイル及び第２の給電コイルの合成インダクタンス値である。また、“ω＝２π・ｆｓ”である。合成インダクタンス値Ｌ１は、当該電力伝送システムに望まれる電力伝送量と、電力供給手段の電圧とに応じて、適切に設定されることが望ましい。合成インダクタンス値Ｌ１が適切に設定されることにより、電力伝送効率を向上させることができる。

Here, “L1” is a combined inductance value of the first feeding coil and the second feeding coil. Further, “ω = 2π · fs”. The combined inductance value L1 is desirably set appropriately according to the amount of power transmission desired for the power transmission system and the voltage of the power supply means. By appropriately setting the combined inductance value L1, the power transmission efficiency can be improved.

  According to the power transmission system according to the embodiment, similarly to the coil unit according to the above-described embodiment, it is possible to suppress a decrease in power transmission efficiency due to the positional deviation between the power feeding coil unit and the power receiving coil unit, and to the surroundings. The radiation magnetic field can be reduced.

  In one aspect of the power transmission system according to the embodiment, the feeding coil unit is disposed coaxially with the first central axis and between the first feeding coil and the second feeding coil. A third feeding coil that is not electrically connected to any of the feeding coil and the second feeding coil is further included. The third feeding coil is configured such that the resonance point of the third feeding coil matches the drive frequency of the power supply means.

  The power receiving coil unit is disposed coaxially with the second central axis and between the first power receiving coil and the second power receiving coil, and is provided for both the first power receiving coil and the second power receiving coil. A third power receiving coil that is not electrically connected is further included. The third power receiving coil is configured such that the resonance point of the third power receiving coil matches the drive frequency of the power supply means.

  According to this aspect, even when the power feeding coil unit is displaced relative to the power receiving coil unit in the extending direction of the first central axis, the power transmission efficiency between the power feeding coil unit and the power receiving coil unit. Can be suitably suppressed.

  An embodiment relating to a power transmission system including a coil unit according to the present invention will be described with reference to the drawings. In the following embodiments, the case where the power transmission system is used as a charging system for a battery mounted on a vehicle such as an electric vehicle is taken as an example.

<First embodiment>
A first embodiment of the power transmission system will be described with reference to FIGS.

  First, the configuration of the power transmission system according to the present embodiment will be described with reference to FIG. FIG. 1 is a conceptual diagram showing an outline of the power transmission system according to the first embodiment.

  In FIG. 1, an electric power transmission system includes an AC power supply 10, a power supply device having a power transmission circuit 100 electrically connected to the AC power supply 10, a load 20 that is a battery mounted on a vehicle, and a load 20 And a power receiving device having a power receiving circuit 200 electrically connected thereto.

  The power transmission circuit 100 includes a rectifier 110, a PFC (Power Factor Correction) circuit 120, an inverter 130, a resonance capacitor 140, and a power transmission coil 150.

  During operation of the power supply apparatus, for example, an AC voltage output from an AC power supply 10 such as a commercial power supply is converted into a DC voltage by the rectifier 110 and the PFC circuit 120. The converted DC voltage is converted into a high-frequency AC voltage by the inverter 130. When a high-frequency AC voltage is applied to the resonance capacitor 140, a high-frequency magnetic field is generated around the power transmission coil 150.

  The power receiving circuit 200 includes a rectifier 210, a resonance capacitor 220, and a power receiving coil 230.

  When the power receiving coil 230 is disposed opposite to the power transmitting coil 150 and a high frequency magnetic field is generated around the power transmitting coil 150, the high frequency magnetic field received by the power receiving coil 230 is converted into a high frequency AC voltage by the action of the power receiving coil 230 and the resonance capacitor 220. Is converted to The high-frequency AC voltage is converted into a DC voltage by the rectifier 210 and supplied to the load 20.

  Next, the coil unit according to the present embodiment will be described with reference to FIG. FIG. 2 is a perspective view showing the coil unit according to the first embodiment. Although only the power transmission coil 150 is illustrated in FIG. 2, the power reception coil 230 has the same configuration as the power transmission coil 150.

  In FIG. 2, the power transmission coil 150 includes a coil 1 and a coil 2. As shown in FIG. 2, the coil 1 and the coil 2 are so-called square core double-sided coils.

  Here, in particular, the coil 1 and the coil 2 are configured and electrically connected so as to form magnetic fields opposite to each other during operation of the power feeding device. In FIG. 2, the coil 1 and the coil 2 are electrically connected in series, and the winding direction of the conducting wire constituting the coil 1 and the winding direction of the conducting wire constituting the coil 2 are opposite to each other. .

  Typically, the coil 1 and the coil 2 have the same outer shape and the same characteristic (inductance value) so that the strength of the generated magnetic field becomes equal. In addition, the central axis of the coil 1 and the central axis of the coil 2 are arranged on the same axis.

  It is desirable that a slight air gap is provided between the magnetic core of the coil 1 and the magnetic core of the coil 2. The reason for this is that, as shown in FIG. 3, when a slight air gap is provided (in FIG. 3, the air gap is “d”), the coupling coefficient between the power transmission coil 150 and the power reception coil 230 is maximum. (Note that the distance between the power transmission coil 150 and the power reception coil 230 remains unchanged). FIG. 3 is a characteristic diagram illustrating an example of the relationship between the air gap and the coupling coefficient of the coil unit according to the first embodiment.

  The air gap is not essential, and the conducting wire constituting the coil 1 and the conducting wire constituting the coil 2 may be wound around the same magnetic core, and both the coil 1 and the coil 2 are air-core coils. May be. Further, a shielding plate such as an aluminum plate may be disposed on the opposite side of the power transmission coil 150 from the side facing the power receiving coil 230. With this configuration, it is possible to increase the coupling coefficient, reduce the radiated magnetic field to the surrounding environment, and the like, which is very advantageous in practice.

  The configuration of the power receiving coil 230 is the same as that of the power transmitting coil 150 described above. However, the size of the power transmission coil 150 and the size of the power reception coil 230 may be different from each other. Specifically, for example, the size of the power receiving coil 230 may be smaller than the size of the power transmitting coil 150. If comprised in this way, the weight of a vehicle can be reduced, for example, the fuel consumption improvement of this vehicle, etc. can be aimed at.

  Even when the size of the power transmission coil 150 and the size of the power reception coil 230 are different from each other, it is desirable that the air gap in the power transmission coil 150 and the air gap in the power reception coil 230 be approximately the same.

  The combined inductance L2 of the coil 1 and the coil 2 (not shown) of the power receiving coil 230 preferably satisfies the following relational expression (1).

ここで、“ｋ”は結合係数であり、“Ｚ”は負荷２０のインピーダンスである。係数ω＝２πｆｓである。“ｆｓ”はインバータ１３０の駆動周波数である。

Here, “k” is a coupling coefficient, and “Z” is the impedance of the load 20. The coefficient ω = 2πfs. “Fs” is the drive frequency of the inverter 130.

  An example of the relationship between the left side of the relational expression (1) and the power transmission efficiency is shown in FIG. As can be seen from FIG. 4, when the combined inductance L2 satisfies the relational expression (1), a relatively high power transmission efficiency can be obtained. FIG. 4 is a characteristic diagram illustrating an example of the relationship between the inductance of the power receiving coil and the transmission efficiency.

  The power transmission coil 150 and the power reception coil 230 of the present embodiment are configured to include a plurality of so-called square core double-sided coils (see, for example, FIG. 5A). For this reason, even if the power transmission coil 150 is displaced relative to the power reception coil 230 in the Y direction in FIG. 5A, the interlinkage magnetic flux decreases and does not become zero. That is, it can be said that the power transmission coil 150 and the power reception coil 230 are not easily affected by the positional shift in the Y direction in FIG. 5A (see FIG. 6B).

  On the other hand, when the power transmission coil 150 is displaced relative to the power reception coil 230 in the X direction of FIG. 5A (see, for example, FIG. 5C), the magnetic field interlinked with the coil 1 of the power reception coil 230. Will be offset. That is, it can be said that the power transmission coil 150 and the power reception coil 230 are easily affected by the positional deviation in the X direction in FIG. 5A (see FIG. 6B).

  In this embodiment, each of the power transmission coil 150 and the power reception coil 230 is installed so that the X direction in FIG. 5A corresponds to the longitudinal direction of the vehicle and the Y direction in FIG. 5A corresponds to the lateral direction of the vehicle. (See FIG. 6A). And if the parking position of a vehicle is restrict | limited by a vehicle stop, the position shift to the front-back direction (namely, X direction) of a vehicle can be suppressed. Therefore, according to the power transmission system according to the present embodiment, it is possible to suitably suppress a decrease in power transmission efficiency due to the positional deviation between the power transmission coil 150 and the power reception coil 230.

  In addition, as described above, the coil 1 and the coil 2 constituting the power transmission coil 150 are configured and electrically connected so as to form magnetic fields opposite to each other during operation of the power feeding device. For this reason, compared with the case where a power transmission coil is comprised from a single coil, the radiation magnetic field to the surrounding environment of the power transmission coil 150 can be suppressed significantly (refer FIG. 7).

<Second embodiment>
A first embodiment of the power transmission system will be described with reference to FIGS. The second embodiment is the same as the configuration of the first embodiment described above except that the configurations of the power transmitting coil and the power receiving coil are partially different. Therefore, the description overlapping with the first embodiment is omitted as appropriate and on the drawing. The same reference numerals are given to the same parts in FIG. 8, and fundamentally different parts from the first embodiment will be described with reference to FIGS.

  The configuration of the power transmission system according to the present embodiment will be described with reference to FIG. FIG. 8 is a conceptual diagram showing an outline of the power transmission system according to the second embodiment having the same concept as in FIG. 1.

  In FIG. 8, the power transmission circuit 101 includes a rectifier 110, a PFC circuit 120, an inverter 130, a resonance capacitor 140, and a power transmission coil 151.

  The power transmission coil 151 is not electrically connected to the coil 1 and the coil 2 (see FIG. 9) that are electrically connected to the inverter 130 via the resonance capacitor 140, and neither the coil 1 nor the coil 2 is connected. And a coil 3 (see FIG. 9).

  The coil 1 and the coil 2 constituting the power transmission coil 151 have the same configuration as the coil 1 and the coil 2 constituting the power transmission coil 150 according to the first embodiment described above. The coil 3 constituting the power transmission coil 151 is a so-called square core double-sided coil. The coil 3 is disposed between the coil 1 and the coil 2 so that the central axis thereof is on the same axis as the central axis of the coil 1.

  Both ends of the coil 3 are electrically connected to the capacitor 151c (see FIG. 8). Here, in particular, the resonance point between the inductance L3 of the coil 3 and the capacitance C3 of the capacitor 151c is set to be substantially equal to the operating frequency Fs of the inverter 130. That is, the inductance L3 and the capacitance C3 are set so as to satisfy the following relational expression (2).

  The capacitor 151c may be a parasitic capacitance if possible. Further, the inductance L3 may be different from the inductance values of the coils 1 and 2 respectively.

  The power receiving circuit 201 includes a rectifier 210, a resonance capacitor 220, and a power receiving coil 231. Similarly to the power transmission coil 151, the power reception coil 231 is also electrically connected to the coil 1 and the coil 2 that are electrically connected to the rectifier 210 via the resonance capacitor 220, and to both the coil 1 and the coil 2. The coil 3 is not provided.

  Both ends of the coil 3 of the power receiving coil 231 are electrically connected to the capacitor 231c (see FIG. 8). The inductance related to the coil 3 of the power receiving coil 231 and the capacitor related to the capacitor 231c are also set so as to satisfy the relational expression (2).

  As described above, the power transmission coil 150 and the power reception coil 230 according to the first embodiment are easily affected by the positional deviation in the X direction. On the other hand, since the power transmission coil 151 and the power reception coil 231 according to the present embodiment include the coil 3, the influence of the positional deviation in the X direction can be suppressed.

  The effect of the present embodiment will be specifically described with reference to FIGS. FIG. 10 is a conceptual diagram illustrating another example of a magnetic field when a positional deviation occurs between the power transmission coil and the power reception coil. FIG. 11 is a characteristic diagram illustrating an example of a relationship between a positional shift in the X direction and a coupling coefficient.

  As shown in FIG. 10A, when there is no displacement between the power transmission coil 151 and the power reception coil 231, between the coil 1 of the power transmission coil 151 and the coil 1 of the power reception coil 231, and the power transmission coil 151. Electric power is transferred between the coil 2 and the coil 2 of the power receiving coil 231. In this case, no induced electromotive force is generated in the coil 3 of the power transmission coil 151 and the coil 3 of the power reception coil 231.

  As shown in FIG. 10B, when the power transmission coil 151 is displaced relative to the power reception coil 231 in the X direction, slight induction due to the coupling between the coil 2 of the power transmission coil 151 and the coil 2 of the power reception coil 231. An induced current flows through the power receiving coil 231 due to the electromotive force. A magnetic field is generated around the coil 1 of the power receiving coil 231 due to the induced current. The magnetic field generated around the coil 1 is amplified by the coil 3 of the power transmission coil 151 (that is, reflected and amplified by the coil 3 of the power transmission coil 151), and the coupling between the power transmission coil 151 and the power reception coil 231 is strengthened. The coil 3 of the power receiving coil 231 also functions in the same manner as the coil 3 of the power transmitting coil 151.

  As a result, as shown in FIG. 11, it is assumed that the configuration according to the present embodiment is displaced in the X direction between the power transmission coil 151 and the power reception coil 231 as compared with the configuration according to the first embodiment described above. Also, it is possible to suppress a decrease in the coupling coefficient.

  The present invention is not limited to the above-described embodiments, and can be appropriately changed without departing from the spirit or idea of the invention that can be read from the claims and the entire specification. A power transmission system is also included in the technical scope of the present invention.

  DESCRIPTION OF SYMBOLS 10 ... AC power supply, 20 ... Load, 100, 101 ... Power transmission circuit, 110, 210 ... Rectifier, 120 ... PFC circuit, 130 ... Inverter, 140, 220 ... Resonance capacitor, 150, 151 ... Power transmission coil, 200, 201 ... Power receiving circuit, 230, 231 ... Power receiving coil

Claims (3)

A coil unit that forms part of a power transmission system capable of receiving power in a non-contact manner from one coil unit and is electrically connected to a load of impedance Z,
A first coil having a central axis along one direction;
When the coil unit is in operation, it is electrically connected to the first coil so as to form a magnetic field opposite to the magnetic field formed by the first coil, and is arranged coaxially with the central axis. A second coil,
The first coil is disposed coaxially with the central axis and between the first coil and the second coil, and is not electrically connected to any of the first coil and the second coil. 3 coils,
With
The combined inductance value L2 of the first coil and the second coil is configured to satisfy Formula 1 where k is the coupling coefficient between the coil unit and the one coil unit, and ω is the resonance frequency. A coil unit characterized by that.

2. The coil unit according to claim 1 , wherein the third coil is configured to resonate with the first coil and the second coil during operation of the coil unit. A non-contact power transmission system comprising a power feeding device and a power receiving device capable of mutual non-contact power transmission,
The power supply device
A feeding coil unit;
A power supply means that is electrically connected to the power supply coil unit and supplies power of a predetermined frequency to the power supply coil unit;
With
The power receiving device is:
A power receiving coil unit disposed opposite to the power feeding coil unit;
A load electrically connected to the power receiving coil unit;
With
The feeding coil unit is
A first feeding coil having a first central axis along one direction;
The first central axis is electrically connected to the first power supply coil so as to form a magnetic field opposite to the magnetic field formed by the first power supply coil during operation of the power supply coil unit. A second feeding coil disposed coaxially with the second feeding coil;
It is disposed coaxially with the first central axis and between the first power supply coil and the second power supply coil, and is electrically connected to both the first power supply coil and the second power supply coil. A third feeding coil that is not connected electrically,
Have
The third feeding coil is configured such that a resonance point of the third feeding coil coincides with a driving frequency of the power supply unit,
The power receiving coil unit is:
A first power receiving coil having a second central axis along the one direction and different from the first central axis;
During operation of the power receiving coil unit, the second central axis is electrically connected to the first power receiving coil so as to form a magnetic field opposite to the magnetic field formed by the first power receiving coil. A second power receiving coil arranged coaxially with
It is arranged coaxially with the second central axis and between the first power receiving coil and the second power receiving coil, and both the first power receiving coil and the second power receiving coil are electrically connected. A third power receiving coil that is not electrically connected;
Have
The third power receiving coil is configured such that a resonance point of the third power receiving coil matches a driving frequency of the power supply means,
The combined inductance of the first power receiving coil and the second power receiving coil, where fs is the driving frequency of the power supply means, Z is the impedance of the load, and k is the coupling coefficient between the power feeding coil unit and the power receiving coil unit. The non-contact power transmission system, wherein the value L2 is configured to satisfy Formula 2.

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