JP6695054B2 - Magnetization prevention device and current detection device using the same - Google Patents

Description

  The present invention relates to a magnetization prevention device and a current detection device using the same.

  As a conventional current detection device, for example, a current detection device using a flux gate type magnetic flux detection method is known (see Patent Document 1).

  The current detection device disclosed in Patent Document 1 includes a magnetic circuit unit including a magnetic core and a coil, and an excitation circuit that applies a voltage that magnetically saturates the magnetic core to the coil. In the current detection device, current flows through the coil with the voltage applied by the excitation circuit. The magnetic field generated by the magnetic core changes according to the change in the current flowing through the conductor whose current is to be detected. When the magnetic field changes, the current flowing through the coil also changes. The current detection device detects the current flowing through the conductor by detecting the change in the current flowing through the coil.

WO2014 / 010187

  In the conventional current detecting device, when a large current flows through the conductor, the magnetic core may be magnetized, and there is a problem that accurate detection cannot be performed in the subsequent current detection.

  The present invention has been made in view of the above problems, and provides a magnetization prevention device and a current detection device using the same, which can reduce the possibility of magnetizing a magnetic core even when a large current flows through a conductor. The purpose is to do.

An anti-magnetization device according to an aspect of the present invention is configured such that a winding wound around a magnetic core through which a conductor is inserted and a winding connected to both ends of the winding, and the induced electromotive voltage generated in the winding, A switch device for opening or closing both ends of the winding, wherein the switch device opens the both ends of the winding when an induced electromotive voltage generated in the winding is less than or equal to a predetermined value. When the induced electromotive voltage is larger than the predetermined value, both ends of the winding are closed, and the magnetic core is used for detection of a current flowing through a conductor, and the first winding as the winding is used. A second winding different from the wire is wound, and the direction of the magnetic flux generated in the first winding when the switch device is in the closed state is the direction of the magnetic flux generated in the second winding. On the other hand, it is characterized by the opposite direction .

  Further, a current detection device according to one aspect of the present invention includes the above-described magnetization prevention device and a current detection unit that detects a current flowing through the conductor by a flux gate method using the magnetic core. To do.

  According to the present invention, it is possible to reduce the possibility of magnetizing the magnetic core even when a large current flows through the conductor.

FIG. 1 is a block diagram illustrating the configuration of the current detection device according to the first embodiment of the present invention. FIG. 2 is a diagram showing an example of a usage pattern of the above current detection device. FIG. 3 is a block diagram illustrating a configuration of a magnetization prevention device included in the above current detection device. FIG. 4 is a block diagram illustrating the configuration of the current detection device according to the second embodiment of the present invention. FIG. 5 is a block diagram illustrating the configuration of the current detection device according to the third embodiment of the present invention. FIG. 6 is a block diagram illustrating a configuration of a current detection device which is a modified example of the current detection device according to the first exemplary embodiment of the present invention. FIG. 7 is a block diagram illustrating a configuration of a current detection device which is another modification of the current detection device according to the first exemplary embodiment of the present invention.

  The following embodiments generally relate to a magnetization prevention device and a current detection device, and more particularly to a magnetization prevention device for a current detection device that detects a measured current flowing through a conductor and a current detection device using the same.

(Embodiment 1)
Hereinafter, the flux gate type current detection device (hereinafter, current detection device) 10 of the present embodiment will be described. FIG. 1 is a diagram for explaining the configuration of the current detection device 10 of the present embodiment, and FIG. 2 is a diagram for explaining the usage of the current detection device 10.

  The current detection device 10 is used in a charging system that charges a storage battery of the electric vehicle 3, as shown in FIG. The electric vehicle 3 is, for example, an electric vehicle or a plug-in hybrid vehicle. Specifically, in the charging system, a commercial system 1 that supplies a commercial power source and an electric vehicle 3 are electrically connected via a conversion device 2. The current detection device 10 is provided on the conductor 30 that connects the commercial system 1 and the conversion device 2, and detects the measured current (unbalanced direct current) flowing through the conductor 30 to thereby drive the commercial system 1 and the electric system. An electric leak between the vehicle 3 and the vehicle 3 is detected. The conversion device 2 has a function of converting an AC power supply into a DC power supply and a function of converting a DC power supply into an AC power supply. Here, the conductor 30 includes a first conducting wire through which a current flows from the commercial system 1 toward the electric vehicle 3, and a second conducting wire through which a current flows from the electric vehicle 3 toward the commercial system 1. When the leakage does not occur, the amount of current flowing through the first conducting wire is the same as the amount of current flowing through the second conducting wire, so that the measured current (unbalanced current) does not occur. However, when the leakage occurs, the measured current is generated because the amount of current flowing through the first conducting wire is different from the amount of current flowing through the second conducting wire. The current detection device 10 can detect electric leakage between the commercial system 1 and the electric vehicle 3 by detecting the measured current.

  As a result, the current detection device 10 leaks an AC current flowing between the commercial system 1 and the converter 2, a high-frequency current flowing through the converter 2, and a DC current flowing between the converter 2 and the electric vehicle 3. Can be detected. The conversion device 2 may be provided in the electric vehicle 3. Further, in the present embodiment, the power supply source is the commercial system 1, but the power supply source is not limited to this. The power source may be a distributed power source such as solar power generation.

  Hereinafter, each component of the current detection device 10 according to the present embodiment will be described.

  As shown in FIG. 1, the current detection device 10 includes a current detection unit 10a and a magnetization prevention device 10b.

  The current detection unit 10a includes a power supply unit 11, an excitation unit 12, a magnetic core 13, an excitation coil 14, a detection resistor 15 (conversion unit), a reference voltage generation unit 16, and a detection unit 17, and a flux gate. The current is detected by the method.

  The power supply unit 11 is configured by a single power supply, and supplies the power supply voltage V0 to the excitation unit 12, the reference voltage generation unit 16 and the detection unit 17.

  The exciting unit 12 is supplied with the power supply voltage V0 and generates an exciting voltage V1 oscillated at a predetermined frequency. The exciting unit 12 applies the generated exciting voltage V1 to the exciting coil 14. Specifically, the excitation unit 12 includes an oscillation circuit that oscillates at a predetermined frequency. The excitation unit 12 amplifies the excitation clock generated by the oscillation circuit, generates a square wave signal (excitation voltage V1) having a predetermined voltage amplitude, and outputs it to the excitation coil 14. As a result, the exciting voltage V1 is applied to the exciting coil 14.

  The magnetic core 13 is, for example, a magnetic core, and is formed in an annular shape having an opening through which the conductor 30 is inserted. The exciting coil 14 is a coil wound around the magnetic core 13.

  One end of the detection resistor 15 is electrically connected to the exciting coil 14, and the other end thereof is electrically connected to the reference voltage generator 16. The detection resistor 15 converts the exciting current I output from the exciting coil 14 into a detection voltage V2.

  The reference voltage generation unit 16 receives the supply of the power supply voltage V0, generates a reference voltage V3 (for example, V3 = V1 / 2), and outputs the reference voltage V3 to the excitation unit 12 and the detection unit 17.

  The detection unit 17 detects the presence or absence of a current (unbalanced current) in the conductor 30 using the detection voltage V2 and the reference voltage V3. For example, when the absolute value of the difference between the average value of the detected voltage V2 and the reference voltage V3 is greater than or equal to a predetermined value, the detection unit 17 has a leakage current between the commercial system 1 and the electric vehicle 3. To detect that. When the difference is less than the predetermined value, detection unit 17 detects that there is no electric leakage between commercial system 1 and electric vehicle 3. The detection unit 17 outputs the detection result. For example, the detection unit 17 outputs the detection result to the display device and causes the display device to display the detection result.

  Next, the configuration of the magnetization prevention device 10b will be described.

  As shown in FIG. 1, the magnetization prevention device 10b includes a coil 21 (winding) and a switch device 22.

  The coil 21 is wound around the magnetic core 13. An induced electromotive voltage is generated in the coil 21 depending on the amount of current flowing through the conductor 30. The coil 21 is wound around the magnetic core 13 so as to generate a magnetic flux (canceling magnetic flux) opposite to the direction of the magnetic flux (exciting magnetic flux) generated in the exciting coil 14 by the induced electromotive voltage. The number of turns of the coil 21 may be one or more.

  The switch device 22 is connected between both ends of the coil 21, and switches between both ends of the coil 21 to an open state or a closed state according to an induced electromotive voltage generated in the coil 21. Specifically, the switch device 22 opens both ends of the coil 21 when the induced electromotive voltage generated in the coil 21 is equal to or lower than a predetermined value, and when the induced electromotive voltage is higher than the predetermined value, the switching device 22 is closed. Close both ends. Here, the predetermined value is 0.7 V, for example. Note that this numerical value is an example, and there is no intention to limit the numerical value.

  Here, a specific configuration of the switch device 22 will be described with reference to FIG.

  The switch device 22 has two series circuits in which one or more diodes are connected in series so that the currents flow in the same direction. The two series circuits are connected in parallel so that the currents flow in different directions (in opposite directions). Note that, here, a circuit configured by one diode is also included in the concept of the series circuit. Based on this concept, the first diode 23 and the second diode 24 shown in FIG. 3 respectively form a series circuit. The first diode 23 and the second diode 24 are connected in parallel so that the direction in which the current flows in the first diode 23 and the direction in which the current flows in the second diode 24 are opposite to each other, and the switch device 22 is connected. I am configuring. By configuring the switch device 22 in this way, when the induced electromotive voltage generated in the coil 21 is equal to or lower than a predetermined value (forward voltage value of the diode), both ends are opened, and the induced electromotive voltage is lower than the predetermined value. When it is large, both ends of the coil 21 can be closed. In addition, in this embodiment, the configuration is such that one diode forms a series circuit, but the configuration is not limited to this. A series circuit may be formed by two or more diodes. By changing the number of diodes forming the series circuit, the above-mentioned predetermined value can be changed.

  When a large current due to an unbalanced current flows through the conductor 30, an induced electromotive voltage larger than a predetermined value is generated in the coil 21. Therefore, both ends of the coil 21 are closed, a magnetic field is generated by the coil 21, and this magnetic field cancels the magnetic field generated in the exciting coil 14. This can reduce the possibility that the magnetic core 13 will be magnetized even when a large current flows through the conductor 30.

  When a large current due to an unbalanced current does not flow in the conductor 30, an induced electromotive voltage of a predetermined value or less is generated in the coil 21. At this time, since both ends of the coil 21 are open, no magnetic field is generated by the coil 21, and only a magnetic field is generated by the exciting coil 14. Therefore, when a large current does not flow through the conductor 30, the current detection unit 10a can detect the current.

  The exciting unit 12 in the present embodiment may be configured to self-oscillate.

  Further, the power supply unit 11 of the present embodiment is described as having a single power supply configuration, but the configuration is not limited to this. The power supply unit 11 may have a dual power supply configuration.

  Although the switch device 22 is configured to include the first diode 23 and the second diode 24, the switch device 22 is not limited to this configuration. The switch device 22 may include a CPU (Central Processing Unit) and a switch connected between both ends of the coil 21. In this case, the CPU determines whether the induced electromotive voltage of the coil 21 is equal to or lower than a predetermined value. When determining that the induced electromotive force is equal to or lower than the predetermined value, the CPU controls the switch so that both ends of the coil 21 are opened. When determining that the induced electromotive voltage is larger than the predetermined value, the CPU controls the switch so that both ends of the coil 21 are closed.

  As described above, the magnetization prevention device 10b of the present embodiment includes the coil 21 (winding) and the switch device 22. The coil 21 is wound around the magnetic core 13 through which the conductor 30 is inserted. The switch device 22 is connected between both ends of the coil 21, and opens or closes both ends of the coil 21 according to an induced electromotive voltage generated in the coil 21. The switch device 22 opens both ends of the coil 21 when the induced electromotive force generated in the coil 21 is less than or equal to a predetermined value, and closes both ends of the coil 21 when the induced electromotive voltage is greater than the predetermined value. And

  When a large current due to an unbalanced current flows through the conductor 30, an induced electromotive voltage larger than a predetermined value is generated in the coil 21. Therefore, according to this configuration, the magnetization preventing device 10b generates a magnetic field by the coil 21 by closing both ends of the coil 21, and a large current due to the unbalanced current flows through the conductor 30 to cause the magnetic core 13 to move. The generated magnetic flux can be canceled. Therefore, the magnetization prevention device 10b can reduce the possibility that the magnetic core 13 will be magnetized even when a large current due to an unbalanced current flows through the conductor 30.

  Here, the switch device 22 has two series circuits (first diode 23, second diode 24) in which one or more diodes are connected in series so that the directions of current flow are the same. It is preferable that the two series circuits (the first diode 23 and the second diode 24) are connected in parallel so that the currents flow in different directions.

  With this configuration, the magnetization prevention device 10b can be realized with a simple circuit configuration without requiring a complicated circuit configuration. Further, by changing the number of diodes forming the series circuit, it is possible to change the predetermined value of the voltage for switching between the closed state and the open state between both ends of the coil 21.

  Further, the current detection device 10 of the present embodiment includes the above-described magnetization prevention device 10b and the current detection unit 10a. The current detector 10a uses the magnetic core 13 to detect the current flowing through the conductor 30 by the flux gate method.

  With this configuration, the current detection device 10 can reduce the possibility that the magnetic core 13 will be magnetized when the current is detected by the flux gate method.

(Embodiment 2)
In this embodiment, the configuration of the switch device 22 is different from that of the switch device 22 of the first embodiment.

  Hereinafter, different points will be mainly described. The same components as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted as appropriate.

  The switch device 22 of the present embodiment has a first diode 23, a second diode 24, and an adjustment resistor 25.

  Similar to the first embodiment, the first diode 23 and the second diode 24 are connected in parallel so that the currents flow in different directions, and form a parallel circuit.

  The adjustment resistance 25 is a resistance of about several Ω (for example, 1 Ω) and is connected to one end of the parallel circuit described above. The resistance value of the adjusting resistor 25 is an example, and the present invention is not limited to this resistance value. The adjusting resistance 25 divides the electromotive voltage.

  Therefore, the magnetization prevention device 10b can adjust the predetermined value of the voltage for switching the both ends of the coil 21 to the closed state or the open state by providing the adjustment resistor 25.

  As described above, the switch device 22 according to the present embodiment is for adjusting the voltage of the parallel circuit in which the two series circuits (the first diode 23 and the second diode 24) are connected in parallel and the voltage of the parallel circuit. It is preferable that the adjusting resistor 25 and the adjusting resistor 25 are connected in series.

  According to this configuration, the magnetization prevention device 10b can adjust the predetermined value of the voltage for switching the both ends of the coil 21 to the closed state or the open state. Therefore, in order to prevent the magnetic core 13 from being magnetized, the magnetization prevention device 10b switches between both ends of the coil 21 to a closed state or an open state according to the amount of large current that is considered to flow through the conductor 30. The predetermined value of the voltage of can be set.

(Embodiment 3)
The present embodiment differs from the first embodiment in that the magnetization prevention device 10b further includes a shield 26.

  Hereinafter, different points will be mainly described. The same components as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted as appropriate.

  The shield 26 of the anti-magnetization device 10b is made of a magnetic material. The magnetic material forming the shield is, for example, ferrite. As shown in FIG. 5, the shield 26 forms a magnetic loop and covers the entire magnetic core 13 and the exciting coil 14.

  The coil 21 is wound around the shield 26.

  When a large current due to an unbalanced current flows through the conductor 30, the coil 21 is wound around the shield 26, so that the magnetic resistance becomes smaller than in the case where the shield 26 is not provided, so that a stronger canceling magnetic flux is generated. You can Therefore, the effect of canceling the exciting magnetic flux is increased.

  In the present embodiment, the shield 26 is configured to cover the entire magnetic core 13 and the exciting coil 14, but the configuration is not limited to this. The shield 26 may have a structure that forms a magnetic loop and covers at least a part of the magnetic core 13 and the exciting coil 14.

  Further, the present embodiment and the second embodiment may be combined.

  As described above, the magnetization prevention device 10b of the present embodiment preferably further includes the shield 26 that covers a part or all of the magnetic core 13 and forms a magnetic loop. The coil 21 is preferably wound around the magnetic core 13 and the shield 26.

  According to this configuration, the magnetization prevention device 10b can generate a stronger canceling magnetic flux as compared with the case where the shield 26 is not provided. Therefore, the magnetization prevention device 10b can further reduce the possibility that the magnetic core 13 is magnetized.

(Modification 1)
Although the current detection device 10 of the first embodiment performs the current detection by the fluxgate method, the current detection may be performed by another method.

  The current detection device 10 may perform current output by an open loop type magnetic sensor system. The configuration of the current detection device 10 in this case will be described with reference to FIG. Hereinafter, the points different from the first embodiment will be mainly described. The same components as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted as appropriate.

  As shown in FIG. 6, the current detection device 10 according to the present modification includes a current detection unit 10a and a magnetization prevention device 10b.

  As shown in FIG. 6, the current detector 10a includes a magnetic core 13a, a Hall element 100, and an amplifier 101.

  The magnetic core 13a is formed in a C shape. The magnetic core 13a generates a magnetic field proportional to the current flowing through the conductor 30.

  The Hall element 100 converts the magnetic field generated in the magnetic core 13a into a voltage.

  The amplifier 101 is connected to the hall element 100 and amplifies the voltage output from the hall element 100.

  The current detector 10a detects the current of the conductor 30 based on the amplified voltage, specifically, the voltage Va between the output voltage v1 of the amplifier 101 and the ground voltage v2.

  The current detection unit 10a of this modification may be applied to the current detection devices 10 of the second and third embodiments.

(Modification 2)
Further, the current detection device 10 may use a closed loop magnetic sensor system as another detection system. The configuration of the current detection device 10 in this case will be described with reference to FIG. 7. Hereinafter, the points different from the first embodiment will be mainly described. The same components as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted as appropriate.

  As shown in FIG. 7, the current detection device 10 of the present modified example includes a current detection unit 10a and a magnetization prevention device 10b.

  As shown in FIG. 7, the current detector 10a has a magnetic core 13b, a coil 14b, a Hall element 110, an amplifier 111, and a detection resistor 112.

Core 13 b is formed in a C-shape. Core 13 b generates a magnetic field by the current flowing in the conductor 30.

  The coil 14b is wound around the magnetic core 13b in a direction that cancels the magnetic field generated by the current flowing through the conductor 30.

Hall element 110 converts the magnetic field generated by the magnetic cores 13 b into a voltage signal.

  The amplifier 111 is a current amplification circuit, receives the voltage signal output from the Hall element 100 as an input signal, and converts the received voltage signal into a current. The amplifier 111 outputs the converted current to one end of the coil 14b.

  The magnetic field generated by the coil 14b due to the current output from the amplifier 111 and the magnetic field generated due to the current flowing through the conductor 30 cancel each other out, and the voltage output from the Hall element 110 is always zero.

  The current detection unit 10a detects the current of the conductor 30 based on the voltage Vb across the detection resistor 112 connected to the other end of the coil 14b.

  The current detection unit 10a of this modification may be applied to the current detection devices 10 of the second and third embodiments.

(Other modifications)
The current detection device 10 is assumed to perform the current detection by the flux gate method, the open loop type or the closed loop type magnetic sensor method in each of the embodiments, the first modification and the second modification. However, the method of current detection performed by the current detection device 10 is not limited to these methods. The current detection device 10 may perform current detection by a CT (Current Transformer) method.

  Further, in each of the above-described embodiments, the current detection device 10 has the power supply unit 11, but is not limited to this configuration. The current detection device 10 does not need to be configured to include the power supply unit 11. For example, the power supply unit 11 may be included in another device.

  In each of the above-described embodiments, the magnetic core 13 has a ring shape, but the shape is not limited to this. The magnetic core 13 may have any shape as long as it forms a magnetic loop.

10 Current Detection Device 10a Current Detection Unit 10b Magnetization Prevention Device 13, 13a, 13b Magnetic Core 21 Coil (winding)
22 Switching Device 23 First Diode 24 Second Diode 25 Adjustment Resistor 26 Shield 30 Conductor

Claims (5)

A winding wound around a magnetic core through which a conductor is inserted,
A switch device which is connected between both ends of the winding and which opens or closes both ends of the winding according to an induced electromotive voltage generated in the winding;
The switch device opens the both ends of the winding when the induced electromotive force generated in the winding is less than or equal to a predetermined value, and when the induced electromotive voltage is greater than the predetermined value, Close both ends ,
A second winding, which is used for detecting a current flowing through a conductor and is different from the first winding as the winding, is wound around the magnetic core,
The magnetization preventing device , wherein the direction of the magnetic flux generated in the first winding when the switching device is closed is opposite to the direction of the magnetic flux generated in the second winding. . The switch device has two series circuits in which one or more diodes are connected in series so that current flows in the same direction.
The magnetizing prevention device according to claim 1, wherein the two series circuits are connected in parallel so that currents flow in different directions. The switch device is
A parallel circuit in which the two series circuits are connected in parallel, and an adjustment resistor for adjusting the voltage of the parallel circuit are configured in a circuit connected in series. The magnetization prevention device described. A shield that covers a part or all of the magnetic core and forms a magnetic loop,
The magnetization prevention device according to any one of claims 1 to 3, wherein the winding is wound around the magnetic core and the shield. A magnetization preventing device according to any one of claims 1 to 4,
A current detecting device, which uses the magnetic core to detect a current flowing through the conductor by a flux gate method.

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