Fluxgate DC current sensor having magnetic return circuit

Abstract

The present invention relates to a fluxgate DC current sensor having a magnetic return circuit, wherein a conventional fluxgate current sensor driven in an analog manner is configured as a magnetic return circuit capable of digital processing, whereby various information, for example, about whether the sensor is abnormal, the oscillation frequency supplied to the coil of a core, and the current being output can be displayed or monitored in real time.

Description

Fluxgate DC current sensor with magnetic recovery circuit

[0001] The present invention relates to a fluxgate DC current sensor having a magnetic recovery circuit capable of displaying or monitoring in real time various information such as whether the sensor is abnormal, the oscillation frequency supplied to the coil of the core, and the current being output, by configuring a conventional analog-driven fluxgate current sensor with a magnetic recovery circuit capable of digital processing.

[0002] There are two methods for measuring the current flowing in a conductor: a direct measurement method in which a current meter is directly electrically connected to the conductor and measured; and an indirect measurement method in which the current in the conductor is measured by detecting the electromagnetic field generated in the surrounding area by the current meter.

[0003] Here, since the direct measurement method has limitations such as being cumbersome and difficult to connect the measuring instrument and not being able to be separated in circuit, indirect measurement methods have recently emerged to overcome the limitations of the direct measurement method.

[0004] A representative example of an indirect measurement method is a method using the Flux Gate method. According to this current measurement method using the Flux Gate method, an AC current is applied to two cores so that the AC magnetization directions are opposite to each other, and the change in electromotive force generated in the coils wound on each of the two cores is detected to detect the DC magnetic flux caused by the current flowing in the conductor. In addition, the AC magnetic flux caused by the current in the conductor is detected using a separate coil, and a current corresponding to the detected DC magnetic flux and AC magnetic flux is applied to cancel out the electromagnetic field caused by the current flowing in the conductor, thereby measuring the current flowing in the conductor by detecting the applied current.

[0005] As conventional techniques for measuring current using the flux gate method, there are registered utility model no. 20-0283971, public patent no. 10-2010-0001504, public patent no. 10-2004-0001535, etc. According to these conventional techniques, by applying a current oscillated in a square wave or a sinusoidal wave and magnetizing two cores in opposite directions, the distortion occurring in the two cores due to the influence of the electromagnetic field caused by the measured current of the conductor is detected as a voltage signal to detect the direct current component, and the alternating current component is detected by a separate core or a separate circuit configuration. Then, magnetic flux is applied as a compensation current corresponding to the detected component to cancel out the magnetic flux caused by the measured current, and the compensation current is converged, and the measured current is measured.

[0006] However, the flux gate type current measuring devices according to the above-mentioned conventional technologies have a configuration that generates a sine wave or square wave oscillation signal separately from the coil wound around the core, and the oscillation signal according to the configuration is simultaneously applied to the winding coils of both cores. Accordingly, the time constant varies depending on the magnetic characteristics of the core, and ultimately, by applying an oscillation signal of a fixed frequency that does not reflect the magnetic characteristics of the core, the core is incompletely magnetized, which appears to be a factor that reduces the accuracy of current measurement. In order to eliminate this factor, an oscillation signal that matches the magnetic characteristics of the core must be generated, but since the error rate of the core is greatly deviated in the manufacturing of the current measuring device, it is very difficult to match the circuit element that generates the oscillation signal to the core, and it is also very cumbersome to match it individually for each measuring device produced, which has caused problems such as reduced productivity and reduced performance.

[0007] Moreover, the above-mentioned conventional technologies have a problem in that the coils are connected in series (in parallel when viewed from the connection point for inputting the oscillation signal) so that the two cores on both sides have opposite polarities, and then the oscillation signal is applied to the serial connection point of the two coils to magnetize the two cores on both sides in opposite directions.

[0008] Meanwhile, in the above-mentioned conventional technologies, since the cores on both sides that are to be magnetized by the oscillation signal are also magnetized by the measured current flowing in the conductor, if the measured current is large, the cores become saturated at the beginning of the measurement and oscillate at a high frequency much higher than the frequency of the oscillation signal, so there was also a problem that detection of the DC component using the flux gate method became impossible.

[0009] As a prior art patent for solving this problem, Korean Patent No. 10-1329240 relates to a non-contact current measuring device that measures the measured current by measuring the compensation current, wherein, as shown in FIGS. 2a and 2b, a first core (M1) wound with a first coil (W1), a second core (M2) wound with a second coil (W2), and a third core (M3) wound with a third coil (W3) are passed through a conductor (W0) through which a measured current flows, a fourth coil (W4) is wound simultaneously on the first, second, and third cores (M1, M2, M3), and a current of the first and second coils (W1, W2) oscillating with opposite polarities and a current induced in the third coil (W3) are applied to the fourth coil (W4), and a capacitor (C1) is connected to the first coil (W1) to measure the measured current. A non-contact current measuring device of a flux gate type is disclosed, characterized in that it comprises an oscillation unit (10) that applies a current to the first coil (W1) by LC oscillation by the inductance of the coil (W1) and the capacitance of the capacitor (C1), and applies a current that reverses the voltage polarity of the current applied to the first coil (W1) to the second coil (W2), thereby causing the magnetization of the first core (M1) and the second core (M2) due to the current application to have opposite polarities; a compensation current generating unit (20) that applies a compensation current corresponding to the sum voltage signal of the first coil (W1) and the second coil (W2) and the voltage signal induced in the third coil (W3) to the fourth coil (W4); and a detection unit (40) that measures the compensation current flowing in the fourth coil (W4) to obtain a measured current.

[0010] The present invention has been made to solve the problems of the prior art, and the purpose of the present invention is to provide a fluxgate DC current sensor having a magnetic recovery circuit capable of displaying or monitoring in real time various information such as whether the sensor is abnormal, the oscillation frequency supplied to the coil of the core, and the current being output, by configuring a conventional fluxgate current sensor driven by an analog method with a magnetic recovery circuit capable of digital processing.

[0011] The problems to be solved by the present invention are not limited to those mentioned above, and other problems not mentioned can be clearly understood by those skilled in the art from the description below.

[0012] In order to achieve the above object, a fluxgate DC current sensor equipped with a magnetic recovery circuit according to the present invention comprises three magnetic cores (T1, T2, T3) for measuring a primary current Ip flowing in a conductor, a current flowing through Ip generates magnetic flux in the magnetic cores, a pulse current is input to the copper windings (Na2, Na3) of the cores (T2, T3), a transformed current is measured through a peak detector, and this is again generated through a power amplifier through an Ns winding in the opposite direction of the magnetic flux generated by Ip, and the magnitude of the current of Ip is measured by canceling the magnetic flux in the opposite direction generated in the core; a magnetic recovery circuit for detecting whether the fluxgate DC current measurement module is abnormal and controlling the magnetic cores (T1, T2, T3) to recover magnetically when they are magnetically saturated; wherein the magnetic recovery circuit comprises: a saturation detection unit for detecting whether the magnetic cores (T1, T2, T3) are saturated; It is characterized by including a saturation prevention output unit that inputs a square wave to the power amplifier to remove saturated magnetic flux in the magnetic cores (T1, T2, T3); a microcontroller unit (MCU) that receives feedback on the output of the saturation detection unit and the DC current measurement module, determines whether the magnetic cores (T1, T2, T3) are abnormal based on a signal input through an A / D converter, and outputs a command signal to the saturation prevention output unit to remove saturated magnetic flux through a D / A converter when it is determined that the magnetic cores (T1, T2, T3) are saturated.

[0013] In addition, the fluxgate DC current sensor equipped with a magnetic recovery circuit according to the present invention is characterized by further including a sensor status display and monitoring unit that displays or monitors the status of the DC current measurement module, the oscillation frequency supplied to the coil of the core, and the current being output; and a communication unit that transmits data output from the sensor status display and monitoring unit to the outside.

[0014] According to the fluxgate DC current sensor equipped with a magnetic recovery circuit according to the present invention, by configuring a conventional analog-driven fluxgate current sensor with a magnetic recovery circuit capable of digital processing, there is an effect of being able to display or monitor in real time various information regarding the presence or absence of a sensor abnormality, the oscillation frequency supplied to the coil of the core, the current being output, etc.

[0015] The effects of the present invention are not limited to those mentioned above, and other effects not mentioned can be clearly understood by those skilled in the art from the description below.

[0016] FIG. 1 is a schematic diagram showing the overall structure of a fluxgate DC current sensor equipped with a magnetic recovery circuit according to the present invention.

[0017] Figures 2a and 2b are drawings showing the structure of a conventional flux gate type non-contact current meter.

[0018] Hereinafter, a preferred embodiment of the present invention will be described in detail.

[0019] In describing the present invention, detailed descriptions of related known functions or configurations will be omitted if they are deemed to unnecessarily obscure the gist of the invention. Furthermore, the terms described below are defined based on their functions within the present invention and may vary depending on the intent of the user or operator, precedent, etc. Therefore, their definitions should be based on the overall content of this specification.

[0020] FIG. 1 is a schematic diagram showing the overall structure of a fluxgate DC current sensor equipped with a magnetic recovery circuit according to the present invention.

[0021] Referring to FIG. 1, a fluxgate DC current sensor equipped with a magnetic recovery circuit according to the present invention can be largely configured to include a fluxgate DC current measurement module and a magnetic recovery circuit.

[0022] The above fluxgate DC current measurement module has three magnetic cores (T1, T2, T3) for measuring the primary current Ip flowing in the conductor, and the current flowing through Ip generates magnetic flux in the magnetic core, and inputs a pulse current to the copper windings (Na2, Na3) of the cores (T2, T3) to measure the transformed current through a peak detector, and generates magnetic flux in the opposite direction of the magnetic flux generated as Ip through the Ns winding again through a power amplifier, and measures the current size of Ip by canceling out the magnetic flux in the opposite direction generated in the core.

[0023] When a current exceeding the rated current is applied to the Ip of a typical fluxgate DC current sensor, the magnetic core configured inside the sensor saturates, thereby losing its function as a current sensor. Therefore, typical fluxgate DC current sensors have a saturation recovery unit configured as an analog circuit and are designed to prevent saturation of the magnetic core. However, this analog saturation recovery unit makes it difficult to monitor the status of the sensor, whether magnetic saturation is present, or the current output current.

[0024] In contrast, in the present invention, by configuring the self-recovery circuit digitally, the current current output through the external communication port can be monitored and the status of the sensor can be monitored.

[0025] In addition, the oscillation frequency supplied to the coils of the T1 and T2 cores can be monitored, and the sensor status, i.e. normal operation status, overcurrent input, saturation status, current current value, etc. can be displayed through a 'status display' consisting of an LED or LCD.

[0026] The magnetic recovery circuit of the present invention can be largely configured to include a saturation detection unit, a saturation prevention output unit, and a microcontroller unit (MCU), as shown in FIG. 1.

[0027] The above saturation detection unit serves to detect whether the magnetic core (T1, T2, T3) is saturated.

[0028] The above saturation prevention output section serves to input a square wave to the power amplifier to remove the saturated magnetic flux in the magnetic core (T1, T2, T3).

[0029] An A / D converter is installed between the above microcontroller unit (MCU) and the saturation detection unit, and a D / A converter is installed between the above microcontroller unit (MCU) and the saturation prevention output unit.

[0030] The above microcontroller unit (MCU) receives the output of the saturation detection unit and the DC current measurement module as feedback and determines whether the magnetic core (T1, T2, T3) is abnormal based on a signal input through an A / D converter. When it is determined that the magnetic core (T1, T2, T3) is saturated, it transmits a command signal to the saturation prevention output unit to remove the saturated magnetic flux through the D / A converter.

[0031] Meanwhile, the present invention may further include a sensor status display and monitoring unit connected to a microcontroller unit (MCU) and a communication unit.

[0032] The above sensor status display and monitoring unit, as described above, displays or monitors the status of the DC current measurement module, the oscillation frequency supplied to the coil of the core, and the current being output.

[0033] The above communication unit serves to display the sensor status and transmit data output from the monitoring unit to the outside.

[0034] Below, we will examine the process of operating the magnetic recovery circuit according to the present invention.

[0035] First, the current sensor of the Zero Fluxgate type of the present invention requires an external power source to input a pulse current to Na2 and Na3. However, if the primary current is applied before the external power source is supplied, the magnetic core inside the sensor is saturated, so when power is first supplied to the sensor, the sensor does not operate normally.

[0036] Therefore, since demagnetization is required to eliminate the magnetic flux of the magnetic core placed inside the sensor, when power is applied, a square wave is input to the Power Amplifier of the Fluxgate current sensor on the MCU board, and an initialization process is performed to eliminate the saturated magnetic flux in the magnetic core (T1, T2, T3) with the current output from the Power Amplifier.

[0037] Next, when the sensor is operating normally after initialization of the current sensor, if the primary current (Ip) exceeds the rated maximum current, the generated magnetic flux cannot be eliminated by offsetting it with the output of the power amplifier, so the power amplifier enters a state where it continuously outputs the maximum current it can output.

[0038] If this saturation state continues, the MCU receives feedback from the saturation detection unit and the sensor output, determines whether there is an abnormality with the signal input through the A / D, and inputs a square wave to the Power Amplifier of the Fluxgate current sensor on the MCU board to remove the saturated magnetic flux in the magnetic core (T1, T2, T3) with the current output from the Power Amplifier.

[0039] The above MCU controls the execution of these processes so that the magnetic core recovers from magnetic saturation in each case where an external power supply is applied or an overcurrent flows while the sensor is operating. In addition, since the above magnetic recovery circuit is configured to include an MCU, an A / D converter, and a D / A converter, it has the advantage of being able to display or monitor various information such as the presence or absence of a sensor abnormality, the oscillation frequency supplied to the coil of the core, and the current being output in real time from the outside through a status display unit and a wired / wireless communication unit.

[0040] The present invention described above is merely exemplary, and those skilled in the art will readily appreciate that various modifications and equivalent other embodiments are possible. Therefore, it will be readily understood that the present invention is not limited to the forms mentioned in the detailed description above. Accordingly, the true technical protection scope of the present invention should be defined by the technical spirit of the appended claims. Furthermore, the present invention should be understood to include all modifications, equivalents, and alternatives within the spirit and scope of the present invention as defined by the appended claims.

[0041]

[0042] The present invention configures a magnetic recovery circuit capable of digital processing of a fluxgate current sensor driven by an existing analog method, thereby enabling display or monitoring of various types of information in real time.

Claims

1. Equipped with three magnetic cores (T1, T2, T3) for measuring the primary current Ip flowing in the conductor, the current flowing through Ip generates magnetic flux in the magnetic core, and inputs a pulse current to the copper windings (Na2, Na3) of the cores (T2, T3) to measure the transformed current through a peak detector, and generates magnetic flux in the opposite direction of the magnetic flux generated as Ip through the Ns winding again through a power amplifier, and measures the current size of Ip by canceling out the magnetic flux in the opposite direction generated in the core; and a fluxgate DC current measurement module; A magnetic recovery circuit that detects whether the above fluxgate DC current measuring module is abnormal and controls the magnetic core (T1, T2, T3) to recover magnetically when it is magnetically saturated; The above self-recovery circuit is, A fluxgate DC current sensor equipped with a magnetic recovery circuit, characterized by comprising: a saturation detection unit for detecting whether the magnetic cores (T1, T2, T3) are saturated; a saturation prevention output unit for inputting a square wave to the power amplifier to remove saturated magnetic flux in the magnetic cores (T1, T2, T3); and a microcontroller unit (MCU) for receiving feedback on the outputs of the saturation detection unit and the DC current measurement module, determining whether the magnetic cores (T1, T2, T3) are abnormal through a signal input through an A / D converter, and outputting a command signal to the saturation prevention output unit to remove saturated magnetic flux through a D / A converter when it is determined that the magnetic cores (T1, T2, T3) are saturated.

2. In paragraph 1, A sensor status display and monitoring unit that displays or monitors the status of the DC current measurement module, the oscillation frequency supplied to the coil of the core, and the current being output; A fluxgate DC current sensor equipped with a magnetic recovery circuit, characterized in that it further includes a communication unit for transmitting data output from the sensor status display and monitoring unit to the outside.

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