JP2010169565A - Current measuring device, and current measurement system using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To heighten measurement accuracy, in a current measuring device installed on a distribution board or the like, for measuring a system current, and transmitting it by radio to an output part provided outside. <P>SOLUTION: A high-frequency current is sent into system wiring 12 through a plug socket 16 by a high-frequency power source 3, and the current is taken out by using a measuring current transformer 11 in the current measuring device 1, and a measuring current is separated from the high-frequency current by a filter circuit 18. Then, amplitude amplification is performed in a resonance circuit 19, and a resonance current is rectified and smoothed by a rectifying/smoothing circuit 20, and then applied to a control circuit 22 including a CPU or the like. Consequently, a stable power source can be secured, and highly accurate measurement to a low currnt can be performed, without exerting an influence on a commercial-frequency current to be measured, and without exerting an influence on a supply voltage generated in a commercial-frequency current quantity. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a current measuring apparatus and a current measuring system using the same, and more particularly to an apparatus for measuring an alternating current flowing through a system electric wire by a measuring apparatus installed in a distribution board or a distribution board.

  In the current measuring device as described above, the magnetic core of the current transformer is arranged so as to have magnetic coupling with the system electric wire, and the AC current flowing through the system electric wire by the electromagnetic winding applied to the magnetic body core In the case where the electric wire is taken out in a non-contact manner and the measuring unit is configured to measure the alternating current, a configuration in which the power source of the measuring device is also taken from the system electric wire has been conventionally used.

  As a representative of such a configuration, in Patent Document 1, the output of a common current transformer is branched into two, and a smoothing capacitor is provided in each full-wave rectifier circuit for stabilization. On the measurement circuit side, the terminal voltage of the load resistor provided in parallel with the smoothing capacitor is read by an arithmetic / output circuit that receives power supply from the power supply circuit. The two circuits are switched by a switch.

JP 2000-65887 A

  In the above-mentioned conventional technology, it is not necessary to provide a separate power source such as a battery, the power source can be taken in from the system wire side, and the power source can be taken in by a current transformer used for measurement, thereby reducing the size of the measuring device. Can be achieved. However, since the power supply voltage varies depending on the amount of current flowing through the system electric wire, there is a problem that it is not stable. In addition, when the measurement device outputs the measurement result to the outside wirelessly, it consumes a large amount of power (especially a transmission amplifier). Each time the wireless transmission is performed, the power supply voltage is reduced and the impedance of the current transformer changes. There's a problem. For this reason, current measurement cannot be performed with high accuracy in the prior art.

  An object of the present invention is to provide a current measuring device capable of measuring current with high accuracy up to a low current even when a current transformer for current measurement is shared for a power supply, and a current measuring system using the current measuring device. .

  The current measuring device according to the present invention includes a current transformer and a measuring unit, the current transformer takes out an alternating current flowing in the grid wire in a non-contact manner, and the measuring unit measures the alternating current. In the apparatus, a filter circuit that extracts a high-frequency current superimposed on the system electric wire connected thereto from a commercial power supply terminal via the current transformer, and a resonance circuit that performs amplitude amplification of the high-frequency current extracted by the filter circuit And a rectifying / smoothing circuit that rectifies and smoothes the resonance current from the resonance circuit and supplies power to each circuit in the measuring device.

  According to the above configuration, in the current measuring device that is installed in a distribution board, a distribution board, or the like and that measures an alternating current flowing through a system electric wire, the measuring device has a magnetic core that magnetically couples to the system electric wire. A current transformer that is arranged so as to have an AC current flowing through the system wire by an electromagnetic winding applied to the magnetic core in a non-contact manner with the system wire is provided with a measurement unit that measures the AC current If so, the power supply of the measuring device is also taken from the system power line.

  Specifically, from the commercial power supply terminal (outlet) side, a high-frequency current flows into the system wire connected thereto, and on the measurement device side, a filter circuit that extracts the high-frequency current from the electromagnetic winding, A resonance circuit that performs amplitude amplification of the high-frequency current extracted by the filter circuit; and a rectification / smoothing circuit that rectifies and smoothes the resonance current from the resonance circuit and supplies power to each circuit in the measurement device; Is further provided.

  Therefore, it is not necessary to separately provide a power source such as a battery in the measuring device, and the power source can be taken in from the system electric wire side. In addition, a power source can be taken in with one current transformer (magnetic coupling block) using a magnetic core or electromagnetic winding used for measurement, and the power source can be reduced in size. Furthermore, even if the power is taken in using the current transformer used for the measurement as described above, the power is supplied at a completely different high frequency from the commercial frequency of the system, which affects the current of the commercial frequency to be measured. In addition, a stable power source can be secured without being affected by the power source voltage generated in the current amount of the commercial frequency, and high-precision measurement can be performed up to a low current.

  The current measuring device according to the present invention further includes an output unit, wherein the measuring unit wirelessly transmits a measurement result to the output unit, and performs wireless transmission and current measurement in a time division manner.

  According to said structure, when the output part which outputs a measurement result to the exterior of the said distribution board or a distribution board is provided, and a measurement part transmits a measurement result to the output part wirelessly, the wireless transmission which consumes big electric power and In addition, since the measurement unit has a function of sharing work with current measurement jobs, voltage fluctuations can be suppressed even if the power supply taken in using the current transformer used for measurement as described above is weak, It is possible to suppress fluctuations in the impedance of the measurement unit due to fluctuations in the amount of power taken in, make it possible to measure current with a constant impedance, and further improve measurement accuracy.

  Furthermore, the current measurement system of the present invention further includes a high-frequency power source that superimposes the high-frequency current from the commercial power supply terminal to the system electric wire in the current measurement device, and the high-frequency power source is configured to overlap the high-frequency current by the superposition of the high-frequency current. The current measuring device is turned on / off.

  According to the above configuration, when necessary, when necessary, it is possible to perform measurement by using high frequency current injection from a high frequency power supply as a trigger, and when the output unit communicates with the measurement unit wirelessly, The measurement results of a plurality of systems can be selectively output using a single output unit.

  As described above, the current measuring device according to the present invention is installed in a distribution board, a distribution board, and the like, and in the current measuring apparatus configured to measure an alternating current flowing through a system electric wire, the measuring device is used as a current transformer. When configured to include a measurement unit, a high-frequency current is supplied from the commercial power supply terminal (outlet) side to the system electric wire connected thereto, and the measurement device side includes the electromagnetic winding of the current transformer. A filter circuit that extracts a high-frequency current, a resonance circuit that performs amplitude amplification of the high-frequency current extracted by the filter circuit, and rectifies and smoothes the resonance current from the resonance circuit to each circuit in the measurement apparatus main body. A rectifying / smoothing circuit for supplying power is further provided.

  Therefore, it is not necessary to separately provide a power source such as a battery in the measuring device, and the power source can be taken in from the system electric wire side. Moreover, a power supply can be taken in using the current transformer used for measurement, and the power supply can be reduced in size. Furthermore, even if the power is taken in using the current transformer used for the measurement as described above, the power is supplied at a completely different high frequency from the commercial frequency of the system, which affects the current of the commercial frequency to be measured. In addition, a stable power source can be secured without being affected by the power source voltage generated in the current amount of the commercial frequency, and high-precision measurement can be performed up to a low current.

It is a figure showing the whole current measuring system composition concerning one embodiment of the present invention. It is a timing chart for demonstrating operation | movement of an electric current measurement apparatus.

  FIG. 1 is a diagram showing an overall configuration of a current measurement system according to an embodiment of the present invention. This current measurement system includes a current measurement device 1, an output unit 2 that wirelessly transmits a measurement result, and displays and outputs it to a user, and a high-frequency power source 3 that will be described later. The output unit 2 is optional for the method of transmitting the measurement result to and from the current measuring device 1 such as displaying the result of the measurement by the current measuring device 1 taken out with a memory card or the like. It can be realized by a receiving terminal or a personal computer equipped with a wireless LAN.

  This current measuring device 1 is provided in a central distribution board 4 or an arbitrary place of the system wiring 12 in a house or office, and an alternating current flowing through the system wiring 12 from the distribution board 4 to the outlet 16 at the terminal is obtained. It is to be measured. The measurement can confirm to which system the load to be additionally connected should be connected, and prevent overcurrent interruption of the circuit breaker 5 of the switchboard 4 due to overload. Therefore, the current measuring device 1 is provided for confirming the load state in advance when the load is added or the like, and the distribution board 4 does not involve complicated wiring work for the existing wiring. The power is not drawn in from the side or the outlet 16 or the like. The output unit 2 is provided outside the switchboard 4. In FIG. 1, the pull-in from the commercial power source 6 is shown by a single-phase three-wire system.

  In the current measuring device 1, the current transformer 11 takes out an alternating current flowing in the system wiring 12 without contact, the measuring unit 13 measures the alternating current, and wirelessly transmits the measurement result to the output unit 3. The current transformer 11 is arranged so that the magnetic core 14 has magnetic coupling to the system wiring 12, and an alternating current flowing through the system wiring 12 is supplied to the system wiring by an electromagnetic winding 15 applied to the magnetic core 14. 12 is removed without contact. Examples of the material of the magnetic core 14 include ferrite, a silicon steel plate, and permalloy.

  It should be noted that the current measuring device 1 according to the present embodiment further includes the high-frequency power source 3 that superimposes a high-frequency current from a commercial power supply terminal, that is, the outlet 16, to the system wiring 12 connected thereto, and corresponds to this. The measurement unit 13 includes a filter circuit 18 that extracts the high-frequency current from the current transformer 11, a resonance circuit 19 that performs amplitude amplification of the high-frequency current extracted by the filter circuit 18, and the resonance circuit 19. And a rectifying / smoothing circuit 20 for supplying power to each circuit in the current measuring device 1 by rectifying and smoothing the resonance current. The high-frequency current is injected into the system wiring 12 using an existing and widely used tool such as a so-called wiring checker, and is injected twice, for example, as a 20 mA signal at 5 kHz.

  In the measurement unit 13, the resonance circuit 19 and the rectifying / smoothing circuit 20 have a high-frequency configuration, and the measurement unit 13 has a configuration provided in a conventional current measurement device as a low-frequency configuration. A rectifying / smoothing circuit 21, a control circuit 22, a memory 23, and a transmission circuit 24 are provided. Note that it is practically difficult to use resonance at a commercial frequency because the frequency is too low, and this low frequency configuration is not provided with a component corresponding to the resonance circuit 19. The control circuit 22 operates in response to power supply from the rectifying / smoothing circuit 20, performs current measurement, stores the measurement result in the memory 23 sequentially, and stores the average value from the stored contents of the memory 23. Arithmetic processing such as peak value and peak value is performed, power is supplied to the transmission circuit 24, and the arithmetic processing result is transmitted to the output unit 3.

  With this configuration, by providing the high frequency power source 3 at an arbitrary outlet 16 on the system wiring 12, it is not necessary to separately provide a power source such as a battery for the current measuring device 1, and the power source is supplied from the system wiring 12 side. Will be able to capture. Further, the power can be taken in by the current transformer (magnetic coupling block) 11 used for measurement, and the power supply can be reduced in size. Furthermore, even if the current transformer 11 used for the measurement is used to take in the power, the power is supplied at a completely different high frequency from the commercial frequency of the system, which affects the current of the commercial frequency to be measured. A stable power supply can be ensured without giving any influence and the power supply voltage generated in the current amount of the commercial frequency is not affected, and highly accurate measurement can be performed up to a low current. Furthermore, using the injection of high-frequency current as a trigger, it is possible to measure only the necessary system when necessary, and selectively output the measurement results of a plurality of systems using the single output unit 2. You can also

  Also, it should be noted that in the current measuring device 1 of the present embodiment, the control circuit 22 performs current measurement and other operations, particularly wireless transmission to the output unit 2 in a time-sharing manner. . FIG. 2 is a timing chart for explaining the operation. The control circuit 22 composed of a CPU has a job sharing function by controlling energization to the transmission circuit 24 in particular. The job means CPU driving, calculation of measurement data, writing / reading to / from the memory 23, wireless transmission / reception, and the like.

  When a high-frequency current is supplied from the high-frequency power source 3, a resonance current is generated in the resonance circuit 19 through the magnetic core 14, the electromagnetic winding 15, and the filter circuit 18, and rectification / smoothing is performed from the resonance current whose amplitude is expanded. A DC voltage is applied to the control circuit (CPU) 22 through the control circuit 20. As a result, the control circuit 22 starts its operation, and alternately performs current measurement and other operations, particularly wireless transmission, as shown in FIG.

  In the current measurement mode, as shown in FIG. 2 (c), the control circuit 22 sequentially takes in the voltage corresponding to the system current taken out by the rectifying / smoothing circuit 21 by analog / digital conversion and takes it in. The system current value is calculated by comparing the voltage with the table value stored in the memory 23, and further, if necessary, the average value or peak value within a certain time is calculated. Write to the memory 23 in the power supply mode. At this time, the control circuit 22 keeps the impedance of the configuration on the high frequency side (seeing the subsequent circuit from the electromagnetic winding 15) in a constant state by an internal circuit of the control circuit 22 or an external fixed resistor (not shown). At the same time, jobs other than the control circuit 22 are stopped (the power supply to the transmission circuit 24 is stopped or is set in a standby (sleep) state). As a result, the circuit impedance on the commercial frequency side during current measurement is stabilized at a high impedance, and the load (current drawn) of the high-frequency power source 3 is stabilized as shown in FIG. 2 (a). As shown, the input voltage to the control circuit 22 can be stabilized and the measurement accuracy can be improved.

  On the other hand, in other job modes, as shown in FIG. 2A, the load (current drawn) of the high-frequency power source 3 increases and sequentially fluctuates due to wireless transmission that consumes a large amount of power. Since the energy that can be taken from the system current using the transformer 11 is determined, the input voltage to the control circuit 22 and the like becomes unstable as shown in FIG. However, in other job modes, current measurement is not performed and no error occurs.

  In this way, by sharing jobs between current measurement and other operations, particularly wireless transmission, voltage fluctuations can be obtained even if the power source taken in using the current transformer 11 used for measurement is weak as described above. It is possible to suppress the fluctuation of the impedance of the measurement unit 13 due to the fluctuation of the amount of power taken in, and to make it possible to measure current with a constant impedance, and to further improve the measurement accuracy.

DESCRIPTION OF SYMBOLS 1 Current measuring device 2 Output part 3 High frequency power supply 4 Distribution board 5 Circuit breaker 6 Commercial power supply 11 Current transformer 12 System wiring 13 Measuring part 14 Magnetic body core 15 Electromagnetic winding 16 Outlet 18 Filter circuit 19 Resonance circuit 20, 21 Rectification / smoothing Circuit 22 Control circuit 23 Memory 24 Transmission circuit

Claims (3)

In a current measuring device comprising a current transformer and a measurement unit, wherein the current transformer takes out an alternating current flowing in the grid wire in a non-contact manner, and the measurement unit measures the alternating current,
A filter circuit for extracting a high-frequency current superimposed on the system electric wire connected thereto from a commercial power supply terminal via the current transformer;
A resonance circuit for performing amplitude amplification of the high-frequency current extracted by the filter circuit;
A current measuring device further comprising: a rectifying / smoothing circuit that rectifies and smoothes a resonance current from the resonance circuit and supplies power to each circuit in the measuring device.   The current measurement apparatus according to claim 1, further comprising an output unit, wherein the measurement unit wirelessly transmits a measurement result to the output unit, and performs wireless transmission and current measurement in a time-sharing manner.   The current measuring device according to claim 1 or 2, further comprising a high-frequency power source that superimposes the high-frequency current from the commercial power terminal to the system electric wire, and the high-frequency power source turns on the current measuring device by superimposing the high-frequency current. A current measurement system characterized by being turned off.

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