JP2006279214A - Signal-injecting/extracting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem wherein a signal-injection/extraction efficiency is deteriorated, by arranging gaps though the gaps are often arranged in cores, in order to prevent a magnetic saturation due to the large electric current of an electricity distribution line concerning a system for injecting/extracting a signal from winding wire which is wound around the ferromagnetic body cores, arranged in the circumference of the electricity distribution line in order to exchange the signal with a power line in power line communication for superimposing a high-frequency signal on the electricity distribution line, so as to transmit the signal. <P>SOLUTION: The ferromagnetic body cores 3 for injecting/extracting the signal to/from the electricity distribution line 1 include gaps 4, in order to prevent the magnetic saturation due to the electric current flowing in the electricity distribution line 1. The injection/extraction efficiency is improved, by changing the number of turns of the signal injection/extraction winding wire 2, in response to the length of the gaps 4. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a signal injection / extraction apparatus for injecting / extracting a high frequency signal in the MHz band to a distribution line.

The development of so-called power line carrier communication (also referred to as PLC) for transmitting a signal by superimposing a high-frequency signal on a distribution line for supplying electric power has been developed, and various techniques for that purpose have been disclosed. In particular, the distribution line has an unclear high-frequency characteristic and is supplied with a commercial frequency high voltage and large current power. Therefore, a very weak MHz band (1 to 30 MHz) carrier wave can be efficiently used, that is, the commercial frequency. A technique for injecting / extracting only a high-frequency signal without receiving the noise is important.
Conventionally, an apparatus shown in Patent Document 1 is disclosed as an apparatus for injecting a MHz band signal into a distribution line or extracting a signal from the distribution line. The device of Patent Document 1 uses a device having a structure similar to CT (Current Transformer) using a ferromagnetic core coupled to a distribution line. In this case, the magnetic core generated by the commercial frequency current flowing through the distribution line will saturate the ferromagnetic core.Therefore, a short-circuit winding for canceling the magnetic field due to the current flowing through the distribution line is used as the core. A power supply device that winds or winds a canceling winding around a core and applies a canceling current to the canceling winding must be used. The cancellation current is not easy because it needs to have the same ampere turn as the commercial line ampere turn and in reverse phase.
As a technique for reducing the magnetic saturation of the ferromagnetic material, in addition to the above, for example, as disclosed in Patent Document 2, the core is divided and a gap is provided between the divided cores to prevent magnetic saturation. The method is known. However, in this case, the magnetic field of the core due to the high-frequency signal is also reduced, which causes a problem that the signal transmission efficiency is lowered.
Japanese Patent Laid-Open No. 2001-319815 “Signal Injection / Extraction Device” Japanese Patent Application Laid-Open No. 11-345715 “Small Electrical Winding Parts”

In conventional signal injection and extraction devices for distribution lines, a shorted winding to prevent magnetic saturation of the ferromagnetic core is wound, or a current is passed through the cancellation winding and the cancellation winding. However, there is a problem that the power supply device is required and the device becomes complicated and the cost is increased.
Further, in the method of providing a gap in the ferromagnetic core, since the signal injection / extraction efficiency is lowered, measures such as increasing the capacity of the core are required, and there is a problem that the cost is also increased.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a signal injection / extraction apparatus that can improve signal injection efficiency and extraction efficiency with a simple structure.

The signal injecting / extracting device according to the present invention holds a plurality of arc-shaped ferromagnets, and each arc-shaped ferromagnet with a predetermined gap therebetween so that a hole through which a conductor can pass is formed. Holding means,
A winding wound around the arc-shaped ferromagnetic material a predetermined number of times;
A signal transmission cable having a characteristic impedance Z ₀ connected to the winding;
The predetermined number of times of the winding is the number of times that the impedance of the winding is ½ or more and twice or less of Z ₀ in a state where the conductor is penetrated and the gap interval is set to a predetermined value. It has been adjusted to.

  According to the signal injection / extraction apparatus of the present invention, it is possible to obtain high signal injection / extraction efficiency with an extremely simple structure.

Embodiment 1 FIG.
FIG. 1 is a structural perspective view showing a signal injection / extraction apparatus according to Embodiment 1 of the present invention, and FIG. 2 is a sectional view of FIG. The arc-shaped or rod-shaped ferromagnetic core 3 arranged so as to surround the distribution line 1 (that is, an annular shape having a hole that can penetrate the conductive wire inside) has a commercial frequency current flowing through the distribution line 1. In order to prevent magnetic saturation caused by the above, a gap 4 is provided, which can be divided into two or more. That is, the ferromagnetic core 3 includes an upper core 3x and a lower core 3y (may be further divided into a large number). In FIG. 2, description will be made assuming that the upper core 3x and the lower core 3y have the same shape. Those different in shape from each other will be described in Embodiment 3. The size of the gap 4 is determined by the magnitude of the commercial frequency current flowing through the distribution line 1. That is, the distance of the gap 4 is increased as the current is increased. The gap 4 can be held at an arbitrary value by holding means (not shown). The ferromagnetic core 3 desirably has a high magnetic permeability at a signal frequency (for example, 5 to 30 MHz) and a low loss. A signal injection / extraction winding 2 is wound around the ferromagnetic core 3. When a high frequency signal is sent to the signal injection / extraction winding 2 from an external transmission device (not shown), a magnetic field is generated inside the core 3 by the signal current. As a result, a signal current proportional to the magnetic field strength and the magnetic permeability of the ferromagnetic core 3 is induced in the distribution line 1.
When extracting the high-frequency signal transmitted through the distribution line 1, a magnetic field is generated in the core 3 by the signal current flowing through the distribution line 1, as in the case of the signal injection, and the signal injection / extraction winding 2 is extracted. In addition, a signal current proportional to the magnetic field strength and the magnetic permeability of the core 3 is induced.

FIG. 3 is a diagram illustrating a method for measuring various characteristics of the apparatus described below. A sufficiently long distribution line 1 has one end connected to a commercial power source (not shown) and the other end connected to a load (not shown), so that a large current flows. A signal injection winding 2A and an extraction winding 2B are wound around two ferromagnetic cores 3A and 3B arranged sufficiently apart from each other (which means that the two cores are not directly magnetically coupled). It is. The ferromagnetic cores 3A and 3B have the same structure and dimensions.
The number of windings is 1 or 2 or 3 turns, and the network analyzer 10 measures injection / extraction efficiency (hereinafter simply referred to as injection efficiency) by changing the gap length. FIG. 3 shows only one turn for convenience of illustration.
The network analyzer 10 includes a transmission circuit 10A and a reception circuit 10B that transmit a high-frequency signal having a weak variable frequency, and can measure a transmission loss between the transmission signal power and the reception signal power.
The transmission circuit 10A of the network analyzer 10 is connected to the signal injection winding 2A of the core 3A, and the reception circuit 10B is connected to the signal extraction winding 2B of the core 3B.

The measurement results are shown in FIGS. Practically, the signal frequency used is often 5-30 MHz, so this frequency range was measured.
4-7, the relative transmission loss between the signal injection winding 2A and the signal extraction winding 2B when the distance of the gap 4 is varied is measured by changing the number of turns of the winding and the measurement frequency. FIG. The vertical axis in the figure represents transmission loss, and the loss becomes larger in the downward direction of the figure.
FIG. 4 shows the characteristics when the distance of the gap 4 is 0 mm, that is, when there is no gap.
FIG. 5 shows the characteristics when the distance of the gap 4 is 1 mm.
FIG. 6 shows the characteristics when the distance of the gap 4 is 5 mm.
FIG. 7 shows the characteristics when the distance of the gap 4 is 10 mm.
In each figure, the number of turns was measured in three types of 1, 2, and 3 turns, and the frequencies were measured in 6, 10, 15, 20, 25, and 30 MHz.

4 and 5, the transmission loss is minimized when the number of turns is 1 at most frequencies used at gaps of 0 mm and 1 mm, but the transmission loss is minimized when the number of turns is 2 at gaps of 5 mm and 10 mm. In order to show this with more objective data, the average transmission loss for each number of turns for each gap in FIGS. 4 to 7 was obtained and shown in FIG.
The above consideration is correct, for example, in the case of FIG. 7 where the gap for a relatively large current is 10 mm. By making two turns at this time, the transmission efficiency is about 8 dB compared to the case of one turn at 10 MHz. This is supported by the improvement.
That is, it can be seen that the optimum number of turns varies depending on the length of the gap 4.

The characteristics obtained from the above experiment will be logically described.
The magnetic resistance Rm of the core 3 when there is no gap 4 is expressed by the equation (1), and the magnetic resistance Rm when there is the gap 4 is expressed by the equation (2).

Here, b: core magnetic path length, μ: core permeability, μ ₀ : gap permeability, S: core cross-sectional area, δ: length of gap 4.
In general, when there is a gap 4, since μ ₀ in Equation (2) is small, the binomial becomes a very large value, and the magnetic resistance Rm increases. On the other hand, the self-inductance L of the core + winding is expressed by Equation (3) where N is the number of turns, so that the self-inductance L decreases as the magnetic resistance Rm increases. That is, L decreases in inverse proportion to the length of the gap 4.

The signal transmission efficiency is greatly influenced by the characteristic impedance (Z0) of the signal transmission cable 5 and the impedance Z of the core + winding portion shown in the equation (4). ω = 2πf,
If k: coupling coefficient, Q = μ ′ / μ ″ (permeability μ = μ ′ + jμ ″), the real part of the impedance is Q and L of the magnetic material, the coupling coefficient as shown in equation (4) It depends on k. That is, the impedance Z of the core + winding part is proportional to L in both the real part and the imaginary part.
Here, FIGS. 9 to 12 show measured values of the impedance Z when the number of turns of the winding 2 is 1, 2, and 3 when the length of the gap 4 is changed. The result shows that the impedance Z decreases as the gap length increases.
Therefore, in order to increase the impedance Z, which has become smaller as the gap length becomes longer, it is necessary to increase the number of turns so that the inductance L shown in Expression (3) increases.

In the results of FIGS. 4 to 7, the loss is reduced when the number of turns is increased when the gap length is increased. The generated magnetic field is determined by the value of the current flowing through the winding 2. and the impedance Z of the core + the winding section, this reduces reflection by impedance matching the characteristic impedance Z ₀ of the connected signal transmission cable 5 can take, since the signal current flows becomes cheaper correspondingly winding 2, Overall transmission loss is reduced.
The reflection coefficient (S11) at the connection point between the winding 2 and the signal transmission cable 5 is expressed by Equation (5). The reflection coefficient values for the signal transmission cable 5 (here, a 200Ω reference line is used) with the impedance shown in FIGS. 9 to 12 are shown in FIGS. 13 to 16. As the gap length is increased, the number of turns is increased. It can be seen that the reflection decreases with increasing.

最終的にはコイルを見た見かけのインピーダンスＺは、
（１／２）Ｚ_０＜Ｚ＜２Ｚ_０とするのが好ましい。

Ultimately, the apparent impedance Z when looking at the coil is
(1/2) Z ₀ <Z <2Z ₀ is preferable.

Embodiment 2. FIG.
3, the number of turns of the signal injection / extraction windings 2A, 2B is fixed, and the characteristic impedance of the signal transmission cable 5 is the impedance of the signal injection / extraction windings 2A, 2B + ferromagnetic cores 3A, 3B. A cable having a value close to Z, for example, a differential feeder line (characteristic impedance 200Ω) is used.
With this configuration, since the reflection between the signal transmission cable 5 and the signal injection / extraction windings 2A and 2B + the ferromagnetic cores 3A and 3B is reduced, the transmission efficiency is improved.
The winding 2 may be used by picking out a tap every half turn and selecting and using the most efficient terminal.

Embodiment 3 FIG.
In FIGS. 1 and 2 of the first embodiment, an example in which the gap 4 is provided at two places is shown, but it may be one place or two or more places. Further, although the upper core 3X and the lower core 3Y are illustrated as symmetrical shapes, they are not necessarily symmetrical. For example, the upper core 3X is U-shaped and the lower core is I-shaped. But it ’s okay.

  The signal injection / extraction device of the present invention is used in, for example, a telemetry device that transmits measurement data of watt-hour meters, water meters, and gas meters to affiliated companies, and a system that transmits data of household appliances used in the home. can do.

It is a perspective view which shows the structure of the signal injection | pouring and extraction apparatus by Embodiment 1 of this invention. It is sectional drawing of the thing of FIG. It is a figure which shows the structure of the measurement in Embodiment 1 of this invention. It is a characteristic view which shows the measurement result of gap 0mm and the number of turns 1, 2, 3 in the structure of FIG. It is a characteristic view which shows the measurement result of gap 1mm and turn number 1,2,3. It is a characteristic view which shows the measurement result of gap 5mm and the number of turns 1, 2, and 3. It is a characteristic view which shows the measurement result of gap 10mm and the number of turns 1, 2, and 3. FIG. FIG. 8 is a characteristic diagram illustrating the transmission loss average value of FIGS. 4 to 7 with respect to a change in gap. It is a figure which shows the impedance measurement result of the signal injection / extraction apparatus of gap 0mm and turn number 1,2,3. It is a figure which shows the impedance measurement result of the signal injection / extraction apparatus of gap 1mm and the number of turns 1, 2, and 3. It is a figure which shows the impedance measurement result of the signal injection / extraction apparatus of gap 5mm, number of turns 1, 2, and 3. It is a figure which shows the impedance measurement result of the signal injection / extraction apparatus of gap 10mm and the number of turns 1, 2, and 3. It is a figure which shows the reflection coefficient (S11) with respect to the reference line in the impedance shown in FIG. It is a figure which shows the reflection coefficient (S11) with respect to the reference line in the impedance shown in FIG. It is a figure which shows the reflection coefficient (S11) with respect to the reference line in the impedance in FIG. It is a figure which shows the reflection coefficient (S11) with respect to the reference line in the impedance in FIG.

Explanation of symbols

1 Distribution line, 2, 2A, 2B Signal injection / extraction winding,
3, 3A, 3B ferromagnetic core, 4 gap,
5 Signal transmission cable, 10 Network analyzer,

Claims (5)

A plurality of arc-shaped ferromagnets, holding means for holding each arc-shaped ferromagnet with a predetermined gap therebetween so that a hole through which a conductor can pass is formed inside;
A winding wound around the arc-shaped ferromagnetic material a predetermined number of times;
A signal transmission cable having a characteristic impedance Z ₀ connected to the winding;
The predetermined number of times of the winding is the number of times that the impedance of the winding is ½ or more and twice or less of Z ₀ in a state where the conductor is penetrated and the gap interval is set to a predetermined value. A signal injection / extraction device characterized by being adjusted to. A plurality of rod-shaped ferromagnets, holding means for holding each of these rod-shaped ferromagnets spaced apart from each other so as to form a hole through which a conductor can pass;
A winding wound around the rod-shaped ferromagnetic body a predetermined number of times;
A signal transmission cable having a characteristic impedance Z ₀ connected to the winding;
The predetermined number of times of the winding is the number of times that the impedance of the winding is ½ or more and twice or less of Z ₀ in a state where the conductor is penetrated and the gap interval is set to a predetermined value. A signal injection / extraction device characterized by being adjusted to.   The signal injecting / extracting device according to claim 1, wherein the conducting wire is a distribution line connected to a commercial power source.   The signal injection / extraction device according to claim 3, wherein the winding includes a plurality of intermediate taps.   5. The signal injection / extraction apparatus according to claim 4, wherein the intermediate tap is provided every 0.5 turns.

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