JP2016081750A - Power transmission device, non-contact power supply device and induction heating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a voltage increase of an output terminal relative to an input terminal of a high-frequency cable more than in the conventional way.SOLUTION: The power transmission device, transmitting an output of an AC power supply to a load through a high-frequency cable, includes a current suppression circuit that is a multi-tap transformer capable of changing a winding ratio for suppressing a power supply current and provided between the output of the AC power supply and an input terminal of the high-frequency cable.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power transmission device, a non-contact power feeding device, and an induction heating device.

  For example, when AC power (high frequency power) of several hundred kHz to several hundred MHz is transmitted from a high frequency power source to a load, a high frequency cable is used. This high-frequency cable is generally a coaxial cable having a predetermined characteristic impedance (for example, 50Ω). Moreover, there exist a non-contact electric power feeder and an induction heating apparatus as an electric power transmission apparatus which uses such a high frequency cable.

For example, in the case of a non-contact power supply device, a high-frequency power source and a power supply coil are connected by a high-frequency cable, and high-frequency power is supplied from the high-frequency power source to the power supply coil via the high-frequency cable. High frequency power is transmitted in a non-contact manner. Patent Document 1 below discloses an example of a non-contact power feeding device using a vehicle.
In the case of the induction heating device, the high frequency power source and the heating coil are connected by a high frequency cable, and high frequency power is supplied from the high frequency power source to the heating coil via the high frequency cable, so that the heating coil is adjacent to the heating coil. The object to be heated is induction heated.

JP 2013-219971 A

  By the way, in the transmission of high frequency power using the high frequency cable, the voltage at the output end (feed coil side end) of the high frequency cable is changed to the voltage at the input end (high frequency power source side end) of the high frequency cable due to the influence of the impedance of the high frequency cable. Bigger than. It is known that this voltage increase increases as the impedance of the high-frequency cable increases, that is, as the high-frequency cable becomes longer.

  Therefore, as the power supply coil connected to the output end of the high-frequency cable, it is necessary to employ a high-voltage resonance circuit component (coil, capacitor) as the length of the high-frequency cable increases. It is a factor that limits the length of the.

  This invention is made | formed in view of the situation mentioned above, and aims at suppressing the voltage rise of the output terminal with respect to the input terminal of a high frequency cable rather than before.

  In order to achieve the above object, in the present invention, as a first solving means related to a power transmission device, a power transmission device that transmits an output of an AC power source to a load via a high frequency cable, the output of the AC power source is provided. A means is provided that includes a current suppression circuit that suppresses transmission current between the end and the input end of the high-frequency cable.

  In the present invention, as a second solving means relating to the power transmission device, a means is adopted in which, in the first solving means, the current suppression circuit is a transformer.

  In the present invention, as a third solving means relating to the power transmission device, in the second solving means, a means is adopted in which the transformer is a multi-tap transformer whose winding ratio can be freely changed.

  In the present invention, as means for solving the contactless power feeding device, means for supplying AC power to the power feeding coil as the load using any one of the first to third power transmission devices is employed.

  In the present invention, as a first solving means related to the induction heating apparatus, means is adopted in which AC power is supplied to the heating coil as the load using any one of the first to third power transmission apparatuses. To do.

  According to the present invention, since the transmission current is suppressed by the current suppression circuit, it is possible to suppress the voltage increase at the output end with respect to the input end of the high-frequency cable as compared with the conventional case.

It is a block diagram which shows the function structure of the electric power transmission apparatus which concerns on one Embodiment of this invention, and a non-contact electric power supply. It is a block diagram which shows the modification of the electric power transmission apparatus which concerns on one Embodiment of this invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the contactless power supply device according to the present embodiment includes a rectifier circuit 1, an inverter circuit 2, a switching control unit 3, a current suppression transformer 4 (current suppression circuit), a high-frequency cable 5, and a power supply coil 6. ing. Among the components constituting these non-contact power feeding devices, the rectifier circuit 1, the inverter circuit 2, and the switching control unit 3 constitute a high frequency power source D (AC power source).

  In addition, the power transmission device according to the present embodiment functions by being incorporated in a non-contact power feeding device, and includes a current suppression transformer 4 and a high-frequency cable 5. The power transmission device and the non-contact power supply device configured as described above are fixedly arranged in a power supply facility provided on the ground, and AC power having a predetermined frequency is supplied to a power reception device provided in a power supply target (for example, a moving body). It is a device that supplies power without contact.

  The power receiving device is a device that receives high-frequency power output from the non-contact power feeding device according to the present embodiment. As shown in FIG. 1, the power receiving coil 7, the rectifier circuit 8, the charging circuit 9, the battery 10, and the like. It has.

  The rectifier circuit 1 in the non-contact power supply device is, for example, a diode bridge and a smoothing circuit, and full-wave rectifies commercial power (for example, single phase 200 volts, 50 Hz) supplied from an external commercial power source and outputs it to the inverter circuit 2. . When the switching operation is controlled by the switching control unit 3, the inverter circuit 2 converts the DC power supplied from the rectifier circuit 1 into AC power having a predetermined frequency f and outputs the AC power to the current suppression transformer 4. The AC power is high-frequency power on the order of several hundred kHz, for example.

  The switching control unit 3 controls the operation of the inverter circuit 2 by outputting a switching signal such as a PWM (Pulse Width Modulation) signal to the inverter circuit 2. That is, the switching control unit 3 controls the amplitude and frequency of the high frequency power output from the inverter circuit 2 to be a predetermined target value. Such a switching control unit 3 temporarily stores a CPU (Central Processing Unit) that functions as an arithmetic circuit, a ROM (Read Only Memory) that stores a control program processed by the CPU, a calculation result of the CPU, and the like. A RAM (Random Access Memory) and an interface circuit with the inverter circuit 2 are provided.

  The current suppression transformer 4 is a transformer provided between the output terminal of the inverter circuit 2, that is, the output terminal of the high frequency power supply (AC power supply) and the input terminal 5 a of the high frequency cable 5. The current suppression transformer 4 is provided to suppress a high-frequency current (transmission current) flowing in the subsequent high-frequency cable 5.

  In other words, the current suppression transformer 4 is a step-up transformer in which the number of secondary windings is larger than the number of primary windings, and the high-frequency power input from the output terminal of the inverter circuit 2 to the primary winding is reduced. The voltage is boosted at a boosting ratio corresponding to the winding ratio of the primary winding and the secondary winding and output from the secondary winding to the high-frequency cable 5. The high-frequency current (secondary current) output from the secondary winding to the input terminal 5a of the high-frequency cable 5 by the step-up function of the current suppressing transformer 4 is a high-frequency current (secondary current) output from the inverter circuit 2 to the primary winding ( Smaller than the primary current) by the inverse of the step-up ratio.

  Note that the current suppression transformer 4 is preferably a multi-tap transformer having one or a plurality of intermediate taps in the secondary winding, rather than a corresponding transformer without an intermediate tap. That is, when a multi-tap transformer is employed, the ratio of the secondary current to the primary current (current ratio) can be easily optimized because the winding ratio can be changed freely (easy). .

  The high-frequency cable 5 is a power cable in which the input end 5 a is connected to the output end (secondary winding) of the current suppression transformer 4 and the output end 5 b is connected to the input end of the power feeding coil 6. The high-frequency cable 5 is a coaxial cable having a predetermined impedance, and transmits high-frequency power input from the current suppression transformer 4 to the feeding coil 6. The high-frequency cable 5 is not limited to a coaxial cable, and may be, for example, a stranded cable, a parallel two-wire cable, or a bus bar.

  Here, the power supply coil 6 in the non-contact power supply device is provided in a state of being close to a power supply target such as a moving body in order to improve power supply efficiency as much as possible. On the other hand, the high-frequency power source (AC power source) is disposed at a position separated from the feeding coil 6 because, for example, it is necessary to ensure stable operation. That is, since the design conditions differ between the high frequency power supply and the feeding coil 6, it must be placed in different environments, and for this reason, the high frequency power supply and the feeding coil 6 must be connected by the high frequency cable 5.

  In the conventional non-contact power supply apparatus, the high-frequency power source and the power supply coil are directly connected using a high-frequency cable. However, in the non-contact power supply apparatus according to the present embodiment, as described above, the output end of the inverter circuit 2, that is, the alternating current A current suppression transformer 4 is provided between the output end of the power source and the input end 5 a of the high-frequency cable 5. That is, the non-contact power feeding device according to the present embodiment includes a power transmission device including the current suppression transformer 4 and the high frequency cable 5.

  The power feeding coil 6 is provided at a position facing a predetermined location (a location where the power receiving coil 7 is provided) to be fed such as the moving body. The feeding coil 6 generates a high-frequency magnetic field around the high-frequency power supplied from the high-frequency cable 5. That is, the feeding coil 6 is coupled to the power receiving coil 7 with a predetermined coupling coefficient by the high frequency magnetic field, and transmits high frequency power to the power receiving coil 7 in a non-contact manner. In addition, about such a feeding coil 6, it is good also as a series resonance circuit or a parallel resonance circuit by providing a capacitor | condenser in series or in parallel. In this case, the resonance frequency of the series resonance circuit and the parallel resonance circuit is set to be the same as the frequency of the high frequency power.

  On the other hand, the power receiving coil 7 in the power receiving device is provided on a power supply target such as a moving body, and receives the high frequency power by being electromagnetically coupled to the power feeding coil 6 and outputs it to the rectifier circuit 8. The high frequency power received by the power receiving coil 7 from the power feeding coil 6 is a coupling coefficient (1 or less) between the power feeding coil 6 and the power receiving coil 7 to the high frequency power supplied from the high frequency power source to the power feeding coil 6 via the power transmission device. The power multiplied by a constant).

  The rectifier circuit 8 is composed of, for example, a diode bridge and a smoothing circuit, and full-wave rectifies and smoothes the high-frequency power input from the power receiving coil 7 and outputs it to the charging circuit 9. The charging circuit 9 is a circuit that charges the battery 10 with the DC power input from the rectifying circuit 8. That is, the charging circuit 9 sets the battery 10 to a fully charged state by adjusting the charging current or the charging voltage according to the charging state (charging rate) of the battery 10.

  The battery 10 is a secondary battery such as a lithium ion battery, and charges and stores DC power supplied from the charging circuit 9. Moreover, although not shown in figure, this battery 10 supplies required electric power to the electric power demand part (for example, motor and various electric circuits) with which electric power feeding objects, such as a moving body, were equipped.

  Next, operations of the power transmission device and the non-contact power feeding device configured as described above will be described in detail.

  In the contactless power supply device according to the present embodiment, the high-frequency power source D transmits the high-frequency power generated based on the commercial power supplied from the external commercial power source to the power supply coil 6 that is a direct load. That is, the inverter circuit 2 and the switching control unit 3 convert the DC power generated from the commercial power (AC power) by the rectifier circuit 1 into high-frequency power, and the power transmission device transmits the high-frequency power to the feeding coil 6.

  The power supply coil 6 supplies high-frequency power to the power receiving device, which is a load of the non-contact power supply device, in a contactless manner. That is, in the power receiving device, the power receiving coil 7 electromagnetically coupled to the power feeding coil 6 receives the high frequency power and outputs it to the rectifier circuit 8, and the rectifier circuit 8 rectifies the high frequency power (alternating current power) to generate direct current. It is converted into electric power and output to the charging circuit 9. The charging circuit 9 is charged by supplying the DC power to the battery 10 while adjusting the DC power according to the charging rate of the battery 10.

  The above is the overall operation of the power transmission device and the non-contact power feeding device according to the present embodiment. In the power transmission device according to the present embodiment, the current suppression transformer 4 boosts the high-frequency power input from the inverter circuit 2. Therefore, because of the nature of the known transformer as an electrical element (the input power and the output power are equal when the inherent loss is ignored), the input end 5a of the high-frequency cable 5 is output to the high-frequency cable 5. The high-frequency current (secondary current) output to is smaller than the high-frequency current (primary current) output from the inverter circuit 2 to the current suppression transformer 4.

For example, when the step-up ratio of the current suppression transformer 4 is “n”, the input voltage of the current suppression transformer 4 is “V ₁ ”, and the input current of the current suppression transformer 4 is “I ₁ ”, the input end 5a of the high-frequency cable 5 , That is, the output voltage V ₂ of the current suppression transformer 4 is n times the input voltage V ₁ , while the output current I ₂ of the current suppression transformer 4 (the input terminal current of the high-frequency cable 5) is equal to the input current I ₁ . 1 / n.

That is, the output terminal voltage V ₃ of the high frequency cable 5 in consideration also the boosting effect of the current suppressing transformer 4, when the impedance of the high frequency cable 5 and "Z" is represented by the following formula (1). In the right side of the equation (1), the first term is a term corresponding to the boosting effect of the current suppression transformer 4, and the second term is a term corresponding to the boosting effect due to the impedance Z of the high-frequency cable 5.
V ₃ = n · V ₁ + (1 / n) · Z · I ₁

As an _example, V 1 = 110 _[V], I 1 = 0.99 [A], n = 3, f = a 100 [kHz], also the impedance Z of the high-frequency cable 5 comprises only inductive reactance _{X L,} the inductance L = 5 [μH]. The output terminal voltage V _3, by substituting each value into the equation (1) is about 487 [V] as shown below.
V ₃ = 3 × 110 + (1/3) × 2π × 100 × 10 ³ × 5 × 10 ⁻⁶ × 150
= 330 + 157 = 487 [V]

On the other hand, the case where the current suppression transformer 4 is not provided (that is, the conventional case) is a case where n = 1 and I ₂ = I ₁ = 150 [A] in the above equation (1). Output voltage V ₃ in this case is approximately 581 [V] as shown below.
V ₃ = 1 × 110 + (1/1) × 2π × 100 × 10 ³ × 5 × 10 ⁻⁶ × 150
= 110 + 471 = 581 [V]

That is, the first term on the right side of Equation (1) is larger than the case where the current suppression transformer 4 is not provided by providing the current suppression transformer 4, but the first term on the right side of Equation (1) is The value is greatly reduced due to the effect of the reduction of the output current I ₂ by the current suppression transformer 4.

According to this embodiment, the output terminal voltage V ₃ of the high frequency cable 5 is reduced by providing the current suppression transformer 4 and suppressing the current flowing through the high frequency cable 5, that is, the output current I ₂ of the current suppression transformer 4. It is possible to suppress more than before. As a result, according to the present embodiment, it is possible to make the high-frequency cable 5 longer than before, or it is possible to suppress the high withstand voltage of the feeding coil 6 that is a load of the high-frequency cable 5.

In addition, this invention is not limited to the said embodiment, For example, the following modifications can be considered.
(1) Although the non-contact electric power feeder was demonstrated in the said embodiment, this invention is not limited to this. The power transmission device according to the present invention is applicable to various applications that transmit AC power using a high-frequency cable.

  The power transmission device according to the present invention is also applicable to an induction heating device as shown in FIG. The induction heating device includes a rectifier circuit 1, an inverter circuit 2, a switching control unit 3, a current suppression transformer 4, a high frequency cable 5, and a heating coil 11, and is formed around the heating coil 11 by a high frequency magnetic field. The heating object W is induction-heated. In FIG. 2, for the sake of convenience, components having the same functions as those of the contactless power supply device of FIG.

  In such an induction heating device, the load of the power transmission device is the heating coil 11, and the high-frequency cable 5 is made longer than the conventional one by performing the same operation as the case of the non-contact power feeding device described above. It is possible to suppress the increase in the withstand voltage of the heating coil 11 that is the load of the high-frequency cable 5.

(2) Although the current suppression transformer 4 is employed as the current suppression circuit of the present invention in the above embodiment, the present invention is not limited to this. The most important function necessary for the current suppression circuit is to suppress the high-frequency current output to the input end of the high-frequency cable, so that a circuit composed of a single or a plurality of circuit elements other than the current suppression transformer 4 (transformer) You may employ | adopt as a suppression circuit.

  For example, a resistor may be employed instead of the current suppression transformer 4. As is well known, the resistor is a circuit element with a power loss in principle, but can suppress a high-frequency current. When a resistor is employed, it is preferable to employ a variable resistor that can freely (easy) adjust the magnitude of the high-frequency current output to the high-frequency cable 5.

  DESCRIPTION OF SYMBOLS 1 ... Rectification circuit, 2 ... Inverter circuit, 3 ... Switching control part, 4 ... Current suppression transformer (current suppression circuit), 5 ... High frequency cable, 5a ... Input end, 5b ... Output end, 6 ... Feeding coil, 7 ... Power reception Coil, 8 ... Rectification circuit, 9 ... Charging circuit, 10 ... Battery, 11 ... Coil for heating, D ... High frequency power supply (AC power supply), W ... Object to be heated

Claims (5)

A power transmission device that transmits the output of an AC power source to a load via a high-frequency cable,
A power transmission device comprising a current suppression circuit for suppressing a transmission current between an output end of the AC power source and an input end of the high-frequency cable.   The power transmission device according to claim 1, wherein the current suppression circuit is a transformer.   The power transmission device according to claim 2, wherein the transformer is a multi-tap transformer whose winding ratio can be freely changed.   The non-contact electric power feeder which supplies alternating current power to the electric power feeding coil which is the said load using the electric power transmission apparatus as described in any one of Claims 1-3.   The induction heating apparatus which supplies alternating current power to the heating coil which is the said load using the electric power transmission apparatus as described in any one of Claims 1-3.

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