JP2009210406A - Current sensor and watthour meter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a current sensor and a watthour meter for suppressing an increase in a circuit scale, and improving the current measurement accuracy in a wide measurement range. <P>SOLUTION: A magnetic field collecting core 1 is provided in the current sensor 10, and annularly formed so as to circumferentially surround a current bar 2. A magnetic field detecting coil 3 is disposed in the gap 55 formed in the magnetic field collecting core 1, and detects a magnetic flux generated in the magnetic field collecting core 1. An integrator 4 is connected to the magnetic field detecting coil 3, and integrates an induced voltage generated in the magnetic field detecting coil 3. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a current sensor and a watt-hour meter, and is particularly suitable for application to a method of detecting a current flowing in a current bar by detecting a magnetic flux generated in a gap of a magnetic core by a current using a coil.

  In the watt-hour meter and the electronic watt-hour meter, a current transformer (CT: current transformer) is widely used as a current sensor for detecting the current flowing through the current bar. As this current transformer, there is one in which a secondary winding is applied to a magnetic core, and when a current flows through the secondary winding by passing a current bar through the magnetic core, the current is detected. Thus, when measuring the current to be measured changes the current, the change in the magnetic flux density of the magnetic core caused by the change can be offset (Patent Document 1).

In addition to current transformers, there are also current sensors that use magnetoelectric conversion elements such as Hall elements (Patent Documents 2 and 3). In this current sensor, a measured current can be measured by arranging a magnetoelectric conversion element at a gap position of the magnetic collecting core and detecting the magnetic flux density generated in the magnetic collecting core by the measured current by the magnetoelectric conversion element. it can.
Alternatively, the Rogowski coil method or the like is known as a method for mainly measuring a large current (Patent Document 1). In this method, a large number of air-core coils are arranged in a ring, and when the current passing through the air-core coil changes, the voltage generated by the change in magnetic flux passing through the air-core coil is integrated to measure the measured current. can do.

As another current sensor, there is a sensor that measures a current to be measured based on an equilibrium current that always cancels a magnetic flux in a gap of a magnetic core (Patent Document 4).
This current sensor includes a C-shaped magnetic core having a gap, a feedback coil wound around the magnetic core, and a signal processing that gives the feedback coil a balanced current that generates a reverse magnetic flux that cancels the magnetic flux generated in the magnetic core. A magnetic sensor is provided that is disposed within the gap between the circuit and the magnetic core and measures the magnetic flux of the magnetic core.

When a current to be measured flows through a conductor (current path) that penetrates the inside of the magnetic core, a magnetic flux proportional to the current is formed around the current path in the magnetic core, and is disposed in the gap of the magnetic core. The magnetic sensor outputs an electrical signal corresponding to the amount of magnetic flux generated in the magnetic core. The signal processing circuit generates a balanced current based on the electrical signal output from the magnetic sensor, and applies this balanced current to the feedback coil, thereby achieving a magnetic balanced state in which the magnetic flux in the gap of the magnetic core is always canceled. And can be varied while the equilibrium current is correlated to the current to be measured.
Japanese Patent Laid-Open No. 6-18568 JP 2006-78255 A JP 2002-214278 A JP 2003-149273 A

  However, in a current transformer in which the secondary winding is applied to the magnetic core, there is a problem that magnetic saturation is likely to occur, and current measurement errors increase. If current negative feedback is performed in order to eliminate current measurement errors, the negative feedback winding must be several thousand turns in order to suppress the drive current to about 100 mA, which is a current-carrying limit of a general semiconductor element. In addition, there is a problem that the magnetic core becomes larger and the cost increases.

In addition, in the method using the magnetoelectric conversion element, measurement errors occur due to the non-linearity and temperature characteristics of the magnetoelectric conversion element in addition to the magnetic characteristics of the magnetic collecting core, and the AC measurement accuracy is inferior to that of the current transformer. there were. In addition to the large sensitivity variation of the magnetoelectric conversion element, there is a problem that the sensitivity variation as a current sensor increases due to the relative position shift between the magnetism collecting core and the magnetoelectric conversion element.
Further, the Rogowski coil method has a problem that it is difficult to produce a coil because it is affected by an external magnetic field due to slight winding unevenness.

In addition, in the method of measuring the current to be measured based on the balanced current, it is necessary to accurately generate the balanced current equivalent to the current to be measured, so that an elaborate signal processing circuit is required, and the circuit of the signal processing circuit There was a problem that the power consumption was large as the scale increased. In addition, the measurement range as a current sensor is limited by the range of the equilibrium current, and the desired measurement range cannot be obtained. In addition to the magnetic characteristics of the magnetic core, the nonlinearity and temperature characteristics of the magnetic sensor, and the influence of external magnetic fields There was a problem that the measurement accuracy decreased.
Accordingly, an object of the present invention is to provide a current sensor and a watt hour meter capable of improving current measurement accuracy over a wide measurement range while suppressing an increase in circuit scale.

  In order to solve the above-described problem, according to the current sensor according to claim 1, the current to be measured is detected by the current to be measured flowing through the conductor through the magnetic flux generated in the magnetic collecting core surrounding the conductor. In the current sensor, a gap formed in the magnetic flux collecting core, a magnetic flux detection coil for detecting a magnetic flux generated in the magnetic flux collecting core in the gap, and an integration for integrating an induced voltage generated in the magnetic flux detection coil Means.

According to the current sensor of claim 2, the gap is a first gap and a second gap provided at different locations of the magnetic flux collecting core, and the front magnetic flux detection coil is connected to the magnetic flux collecting core. A first magnetic flux detection coil for detecting the generated magnetic flux in the first gap; and a second magnetic flux detection coil for detecting the magnetic flux generated in the magnetic flux collecting core in the second gap; The integrating means integrates induced voltages generated in the first and second magnetic flux detecting coils.
According to the current sensor of claim 3, the first magnetic flux detection coil and the second magnetic flux detection coil have an induced voltage of the same polarity with respect to the magnetic flux circulating through the magnetic flux collecting core. It is generated and connected to generate an induced voltage having a reverse polarity with respect to the external magnetic field.

According to a fourth aspect of the present invention, the magnetic flux detection coil includes a coil pattern formed on a dielectric substrate, and is arranged so that the magnetic flux generated in the gap penetrates the dielectric substrate. It is characterized by that.
According to a fifth aspect of the present invention, the integration means is disposed on the dielectric substrate.
According to a watt-hour meter described in claim 6, current measurement is performed using the current sensor described in any one of claims 1 to 5.

  As described above, according to the present invention, magnetic saturation can be made difficult to occur by detecting the magnetic flux generated in the magnetic collecting core by the current through the magnetic flux detection coil in the gap, It is possible to eliminate influences such as non-linearity and temperature characteristics when detecting magnetic flux, and it is possible to improve current measurement accuracy over a wide measurement range while suppressing an increase in circuit scale.

In addition, by detecting the magnetic flux generated in the magnetic flux collecting core by the current in the gaps formed at different locations, it is possible to cancel the influence of the external magnetic field and make it difficult to cause magnetic saturation and to detect the magnetic flux. It becomes possible to eliminate the influence of time non-linearity, temperature characteristics, etc., and to further improve the current measurement accuracy over a wide measurement range.
In addition, by performing current measurement using the current sensor according to the present invention for a watt-hour meter, a watt-hour meter capable of improving current measurement accuracy over a wide measurement range while suppressing an increase in circuit scale is provided. Can be configured.

Hereinafter, a current sensor according to an embodiment of the present invention will be described with reference to the drawings.
1A is a perspective view showing a schematic configuration of the current sensor according to the first embodiment of the present invention, and FIG. 1B is a current detection coil in the current sensor of FIG. It is a top view which shows schematic structure of these.
In FIG. 1A, the current sensor 10 is provided with a magnetic collecting core 1 configured in an annular shape so that the current bar 2 is surrounded in the circumferential direction, and a gap 5 is formed in the magnetic collecting core 1. Yes. In addition, the magnetic flux collecting core 1 can be configured by using a single piece of a plate-like piece formed by shearing permalloy, a silicon steel plate, iron, or the like. Alternatively, in order to improve the saturation amount of the magnetic flux, a plurality of plate-like pieces formed by shearing permalloy, silicon steel plate, iron or the like may be laminated. A magnetic flux detection coil 3 for detecting the magnetic flux generated in the magnetic flux collecting core 1 is disposed in the gap 5, and the magnetic flux detection coil 3 is integrated to integrate the induced voltage generated in the magnetic flux detection coil 3. Device 4 is connected,
Here, as shown in FIG. 1B, the magnetic flux detection coil 3 can be constituted by a coil pattern 3b formed on a printed circuit board 3a which is a dielectric substrate, and the magnetic flux generated in the gap 5 is printed. It can arrange | position so that the board | substrate 3a may be penetrated.

FIG. 2 is a circuit diagram showing a schematic configuration of the integrator in the current sensor of FIG.
In FIG. 2, the integrator 4 is provided with an operational amplifier 14, a resistor 11 is connected to the inverting input terminal of the operational amplifier 14, and a capacitor 12 and a resistor are connected between the inverting input terminal and the output terminal of the operational amplifier 14. 13 are connected in parallel.
In FIG. 1, when the current to be measured flows through the current bar 2, a magnetic flux proportional to the current to be measured is generated in the magnetic collecting core 1, and the magnetic flux leaks out from the gap 5. Pierce. When the magnetic flux passing through the magnetic flux detection coil 3 changes, an induced voltage is generated in the magnetic flux detection coil 3, and a voltage signal proportional to the time change of the current to be measured is extracted from the induced voltage. The current to be measured can be measured by integrating the voltage signal by the integrator 4.

  Thereby, the magnetic flux generated in the magnetic flux collecting core 1 by the current can be detected via the magnetic flux detection coil 3 in the gap 5, and it becomes possible to make magnetic saturation difficult to occur and use a magnetoelectric conversion element. This eliminates the need to eliminate the effects of non-linearity and temperature characteristics when detecting magnetic flux, and it is possible to improve current measurement accuracy over a wide measurement range while suppressing an increase in circuit scale. It becomes possible.

  Further, if the relative position between the current bar 2 and the magnetic collecting core 1 and the arrangement position of the printed circuit board 3a are accurately determined, the magnetic flux penetrating the magnetic collecting core 1 can be uniquely determined by the current to be measured. Since the external magnetic flux is small, the current measurement accuracy can be maintained even when the magnetic flux detection coil 3 has some winding unevenness. Further, since the distribution of the magnetic flux penetrating the magnetic flux collecting core 1 by the external magnetic field is also limited to the vicinity of the magnetic flux collecting core 1, by appropriately designing the magnetic flux collecting core 1 and the magnetic flux detection coil 3, it is caused by the external magnetic field. Noise can be reduced.

3 is a cross-sectional view showing a schematic configuration of a current sensor according to a second embodiment of the present invention, and FIG. 4 is a plan view showing a schematic configuration of a magnetic flux detection coil when viewed from the A direction in the current sensor of FIG. FIG.
In FIG. 3, the current sensor 20 is provided with a magnetic flux collecting core 21 configured in an annular shape so that the current bar 22 is surrounded in the circumferential direction, and the magnetic flux collecting core 21 has gaps 26 a and 26 b at a plurality of locations. Is formed. The gaps 26a and 26b are preferably formed in the magnetic flux collecting core 21 so as to be arranged on the same plane. Further, the magnetic flux collecting core 21 can be configured by using a single piece of a plate-like piece formed by shearing permalloy, a silicon steel plate, iron, or the like. Alternatively, in order to improve the saturation amount of the magnetic flux, a plurality of plate-like pieces formed by shearing permalloy, silicon steel plate, iron or the like may be laminated.

In the gaps 26a and 26b, magnetic flux detection coils 23a and 23b that respectively detect magnetic fluxes generated in the magnetic flux collecting core 21 are arranged. The magnetic flux detection coils 23a and 23b include magnetic flux detection coils 23a and 23b, respectively. Integrating means 24 for integrating the induced voltage generated at is connected. Here, the magnetic flux detection coils 23a and 23b generate an induced voltage having the same polarity with respect to the magnetic flux F1 circulating through the magnetic collecting core, and generate an induced voltage having the opposite polarity with respect to the external magnetic field F2. As shown in FIG. 4, one end of the magnetic flux detection coil 23a and one end of the magnetic flux detection coil 23b are connected as shown in FIG. 4, and the other end of the magnetic flux detection coil 23a and the other magnetic flux detection coil 23b are connected. The ends can be connected to the integrating means 24.
Note that the magnetic flux detection coils 23 a and 23 b can be configured by a coil pattern formed on the printed circuit board 25, and can be arranged so that the magnetic flux generated in the gaps 26 a and 26 b penetrates the printed circuit board 25.

  In FIG. 3, when the current to be measured flows through the current bar 22, a magnetic flux F1 proportional to the current to be measured is generated in the magnetic collecting core 21, and the magnetic flux leaks from the gaps 26a and 26b, thereby detecting the magnetic flux. The coils 23a and 23b are penetrated. When the magnetic flux passing through the magnetic flux detection coils 23a and 23b changes, an induced voltage is generated in the magnetic flux detection coils 23a and 23b, and the induced voltage is added and input to the integrating means 24, and in the same direction. When the external magnetic field F2 is applied to the magnetic flux detection coils 23a and 23b, the induced voltage generated in the magnetic flux detection coils 23a and 23b by the external magnetic field F2 is subtracted and input to the integrating means 24. Then, the current to be measured can be measured by integrating the voltage signal proportional to the time change of the current to be measured extracted from these induced voltages by the integrating means 24.

Thereby, by detecting the magnetic flux generated in the magnetic collecting core 21 by the current in the gaps 26a and 26b formed at different locations, it is possible to cancel the influence of the external magnetic field F2 and make it difficult to cause magnetic saturation. In addition, it becomes possible to eliminate the influence of non-linearity and temperature characteristics at the time of magnetic flux detection, and it is possible to further improve the current measurement accuracy over a wide measurement range.
As shown in FIG. 5, the integration means 31 that integrates the induced voltage generated in the magnetic flux detection coils 23 a and 23 b may be disposed on the printed circuit board 25.
Furthermore, the watt-hour meter which can improve a current measurement precision further over a wide measurement range using the current sensor in any one of Embodiments 1-3 is comprised.

FIG. 1A is a perspective view showing a schematic configuration of the current sensor according to the first embodiment of the present invention, and FIG. 1B shows a schematic configuration of a current detection coil in the current sensor of FIG. FIG. It is a circuit diagram which shows schematic structure of the integrator in the current sensor of Fig.1 (a). It is sectional drawing which shows schematic structure of the current sensor which concerns on 2nd Embodiment of this invention. It is a top view which shows schematic structure of the coil for magnetic flux detection when it sees from the A direction in the current sensor of FIG. It is sectional drawing which shows schematic structure of the current sensor which concerns on 3rd Embodiment of this invention.

Explanation of symbols

10, 20, 30 Current sensor 1, 21 Current collecting core 2, 22 Current bar 3, 23a, 23b Magnetic flux detection coil 3a Printed circuit board 3b Coil pattern 4 Integrator 5, 26a, 26b Gap 11, 13 Resistor 12 Capacitor 14 Operational amplifier 24, 31 Integration means 25 Printed circuit board

Claims (6)

In a current sensor for detecting the current to be measured via a magnetic flux generated in a magnetic collecting core surrounding the conductor by a current to be measured flowing in the conductor,
A gap formed in the magnetic flux collecting core;
A magnetic flux detection coil for detecting a magnetic flux generated in the magnetic flux collecting core in the gap;
An electric current sensor comprising: integrating means for integrating an induced voltage generated in the magnetic flux detecting coil. The gaps are first and second gaps provided at different locations of the magnetic core.
The front magnetic flux detection coil detects a magnetic flux generated in the magnetic flux collecting core in the first gap, and detects a magnetic flux generated in the magnetic flux collecting core in the second gap. And a second magnetic flux detecting coil
2. The current sensor according to claim 1, wherein the integrating means integrates induced voltages generated in the first and second magnetic flux detecting coils.   The first magnetic flux detection coil and the second magnetic flux detection coil generate an induced voltage of the same polarity for the magnetic flux circulating through the magnetic collecting core, and induce a reverse polarity for the external magnetic field. 3. The current sensor according to claim 2, wherein the current sensor is connected so as to generate a voltage.   4. The magnetic flux detection coil includes a coil pattern formed on a dielectric substrate, and is arranged so that a magnetic flux generated in the gap penetrates the dielectric substrate. The current sensor according to item 1.   5. The current sensor according to claim 4, wherein the integrating means is disposed on the dielectric substrate.   An electric energy meter that performs current measurement using the current sensor according to any one of claims 1 to 5.

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