JP7370164B2 - Current sensor and energy meter - Google Patents

Description

The present invention relates to a current sensor and a power meter that can detect abnormalities due to heat generation with a simple configuration.

Conventionally used current sensors include a current transformer (CT), a configuration in which a magnetoelectric conversion element such as a Hall element is placed in the gap of the magnetic collecting core, There are configurations that include a wire-wound coil or an element with a coil pattern formed on a dielectric substrate. In particular, the method of arranging a magnetoelectric conversion element such as a Hall element or an element with a coil pattern formed on a substrate in the gap of the magnetic collecting core is electrically separated from the circuit through which the primary current flows, which is the object of measurement. This makes it possible to measure current accurately without affecting the circuit on the primary current side. Furthermore, the method of arranging elements formed with coil patterns has excellent linearity and temperature characteristics, and has a feature that the number of parts is small and manufacturing is easy (see Patent Document 1).

In the current sensor described in Patent Document 1, a current bar is passed through the central opening of an annular magnetic collecting core, and a substrate with a coil pattern is placed in the gap of the magnetic collecting core. When a current flows through the current bar, a magnetic flux is generated around the current path that is proportional to the magnitude of the current flowing through the current bar. The generated magnetic flux is collected by a magnetic collecting core. When the current is a periodic current, the generated magnetic flux also changes periodically according to the period. As a result, an induced voltage corresponding to the magnitude and frequency of the current is generated in the detection coil having the coil pattern, and this induced voltage is used as a detection signal for the current flowing through the current bar.

Japanese Patent Application Publication No. 2010-48755

By the way, current sensors that place magnetoelectric transducers in the gap of the magnetic collecting core can measure current, but cannot detect temperature, so abnormal heat generation may occur in the current bar or terminal due to poor contact. In this case, there was a problem that this abnormality could not be detected. On the other hand, although it is possible to separately provide a temperature sensor to detect abnormalities due to heat generation, it is costly to separately install an additional temperature sensor.

The present invention has been made in view of the above, and an object of the present invention is to provide a current sensor and a power meter that can detect abnormalities due to heat generation with a simple configuration.

In order to solve the above problems and achieve the objects, the current sensor according to the present invention includes: a current bar through which a current to be detected flows; a magnetic detection coil that detects magnetism corresponding to the current as an induced voltage; A current sensor having a measurement unit that measures the current based on an induced voltage generated in a magnetic detection coil, the current sensor having a temperature detection unit that detects temperature on a substrate on which the magnetic detection coil is arranged. It is characterized by

Further, in the current sensor according to the present invention, in the above invention, the temperature detection section forms a pattern of a resistance temperature detector on the substrate, and detects the temperature based on a change in the resistance value of the pattern. It is characterized by

Moreover, the current sensor according to the present invention is characterized in that, in the above invention, the magnetic detection coil is a coil pattern formed on the substrate.

Furthermore, the current sensor according to the present invention is characterized in that, in the above invention, the pattern of the temperature measuring resistor is arranged in the same area as the arrangement area of the magnetic detection coil, but in a different layer.

Further, in the current sensor according to the present invention, in the above invention, the temperature detection section applies a DC current or a frequency lower than the frequency of the current flowing through the current bar to the temperature sensing resistor to detect the temperature. It is characterized by doing.

Further, in the current sensor according to the present invention, in the above invention, the magnetic detection coil is arranged in one or more gaps formed in a magnetic collecting core formed so as to surround the current bar. do.

Further, the watt-hour meter according to the present invention calculates the amount of electric power flowing through the current bar based on the current signal detected by the current sensor described in any one of the above inventions and the voltage signal detected by the voltage sensor. It is characterized by calculating.

According to the present invention, an abnormality due to heat generation can be detected with a simple configuration.

FIG. 1 is a perspective view showing the general configuration of a current sensor according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing the structure of the substrate. FIG. 3 is a diagram showing the temperature dependence of the resistance value of a resistance temperature sensor. FIG. 4 is an explanatory diagram illustrating the structure of a substrate according to modification 1. FIG. 5 is an explanatory diagram illustrating the structure of a substrate according to modification 2. FIG. 6 is an explanatory diagram illustrating the structure of a substrate according to modification 3. FIG. 7 is a perspective view showing the general configuration of a current sensor according to the fourth modification. FIG. 8 is a schematic diagram of the current sensor shown in FIG. 7 viewed from the axial direction of the current bar. FIG. 9 is a block diagram showing an example of a power meter using the current sensor shown in the embodiment and modification. FIG. 10 is a vector diagram between three-phase currents and three-phase voltages.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a perspective view showing the general configuration of a current sensor 10 according to an embodiment of the present invention. Further, FIG. 2 is a schematic diagram showing the configuration of the substrate 3. As shown in FIG. As shown in FIG. 1, the current sensor 10 includes a magnetic flux collecting core 1 and a substrate 3 formed to surround a current bar 2 through which current flows. The substrate 3 also includes a magnetic detection coil 4 that is interposed in the gap 1a of the magnetic collecting core 1 and performs magnetic detection, a temperature sensing resistor 5 whose resistance value changes depending on temperature, and an induced voltage generated in the magnetic detection coil 4. It has a measuring section 6 which measures the current and also measures the temperature based on the change in the resistance value of the resistance temperature detector 5.

As shown in FIG. 2, the magnetic detection coil 4 is arranged in the gap region E of the gap 1a, and the resistance temperature detector 5 and the measuring section 6 are arranged outside the gap region E. The same coil pattern is formed in the magnetic detection coil 4 and the temperature measuring resistor 5. Each coil pattern is made of copper, for example.

The measurement section 6 includes a current measurement section 7 and a temperature measurement section 8. The current measurement unit 7 measures the current flowing through the current bar 2 based on the induced voltage input from the terminals 4 a and 4 b of the magnetic detection coil 4 . The temperature measurement unit 8 applies a current to the resistance temperature sensor 5 via the terminals 5 a and 5 b of the resistance temperature sensor 5 and measures the temperature based on a change in the resistance value of the resistance temperature sensor 5 . Note that the magnetic detection coil 4 and the current measurement section 7 are the current detection section 11 , and the resistance temperature detector 5 and the temperature measurement section 8 are the temperature detection section 12 . The measurement unit 6 outputs the current measured by the current measurement unit 7 and the temperature measured by the temperature measurement unit 8 to the outside via a terminal 9.

For example, as shown in FIG. 3, the temperature measurement unit 8 measures the temperature from the measured resistance value based on the temperature dependence of the resistance value of the resistance temperature detector 5. For example, when the resistance value is 16Ω, the temperature measurement unit 8 measures the temperature at 20°C. Then, an external device (not shown) determines that an abnormality has occurred when the temperature exceeds 80°C. That is, the temperature detection unit 12 can detect a temperature rise of the current bar 2 or the terminal connection portion of the current bar 2.

Since the temperature measuring resistor 5 is arranged outside the gap region E, the current applied by the temperature measurement unit 8 to the temperature measuring resistor 5 may be an alternating current, and has a frequency lower than the frequency of the current flowing through the current bar 2. It may be a low frequency. Application of alternating current to the resistance temperature detector 5 can reduce power loss during temperature measurement. Note that the current applied to the temperature sensing resistor 5 may be direct current.

In addition, in order to reduce resistance value measurement errors due to the wiring length between the terminals 5a, 5b and the resistance temperature sensor 5, the temperature detection unit 12 can perform temperature measurement using a four-conductor method instead of a three-conductor method, for example. good.

In this embodiment, since the temperature detection section 12 is provided on the substrate 3 on which the current detection section 11 is disposed, there is no need to separately install the temperature detection section 12, so the temperature detection can be performed with a simple configuration. A possible current sensor 10 can be realized. Further, since the magnetic detection coil 4 and the temperature sensing resistor 5 have the same pattern, the design and manufacture of the substrate 3 are also facilitated.

<Modification 1>
FIG. 4 is an explanatory diagram illustrating the configuration of the substrate 13 according to the first modification. In Modification 1, the substrate 13 corresponding to the substrate 3 is a multilayer substrate having a four-layer structure. The substrate 13 is a multilayer substrate consisting of four layers of substrates 13-1 to 13-4. The magnetic detection coils 14-1 to 14-4 corresponding to the magnetic detection coil 4 have a four-layer structure in the gap region E, and the resistance temperature detectors 15-1 and 15-2 correspond to the resistance temperature detector 5. has a two-layer structure. Note that the temperature sensing resistors 15-1 and 15-2 are not coil-shaped but have a zigzag meander pattern. A magnetic detection coil 14-1 and a temperature sensing resistor 15-1 are formed on the first layer substrate 13-1. A magnetic detection coil 14-2 and a temperature sensing resistor 15-2 are formed on the second layer substrate 13-2. A magnetic detection coil 14-3 is formed on the third layer substrate 13-3. A magnetic detection coil 14-4 is formed on the fourth layer substrate 13-4.

In the first layer substrate 13-1, the magnetic detection coil 14-1 is connected to the via b1 connected to the terminal 4a. The magnetic detection coil 14-1 is connected to the magnetic detection coil 14-2 formed on the second layer substrate 13-2 via a via b2. Further, the magnetic detection coil 14-2 is connected to the magnetic detection coil 14-3 formed on the third layer substrate 13-3 via a via b3. Further, the magnetic detection coil 14-3 is connected to a magnetic detection coil 14-4 formed on the fourth layer substrate 13-4 via a via b4. The magnetic detection coil 14-4 is connected to the first layer wiring 14a via a via b5, and further connected to the terminal 4b via a via b6. That is, in the magnetic detection coil of Modification 1, the magnetic detection coils 14-1 to 14-4 are arranged in multiple layers in the gap region E. Thereby, magnetic detection sensitivity can be improved even in a narrow area.

On the other hand, in the first layer substrate 13-1, a meandering patterned resistance temperature detector 15-1 is connected to a via b11 connected to the terminal 5a. The resistance temperature detector 15-1 is connected to the second layer resistance temperature detector 15-2 via the via b12. Furthermore, the temperature sensing resistor 15-2 is connected to the terminal 5b connected to the first layer via the via b13. That is, in the resistance temperature detector of Modification 1, the resistance temperature detectors 15-1 and 15-2 in a meandering pattern are arranged in multiple layers outside the gap region E. Note that the temperature sensing resistors 15-1 and 15-2 may be arranged in more layers, or may be arranged in other layers. Thereby, even in a narrow area, it is possible to increase the change in the resistance value of the temperature measuring resistor, and it is possible to improve the accuracy of temperature measurement.

<Modification 2>
FIG. 5 is an explanatory diagram illustrating the configuration of the substrate 23 according to the second modification. In the present modification example 2, the substrate 23 has a six-layer structure consisting of substrates 23-1 to 23-6, and the resistance temperature detectors 25-1 and 25-2 corresponding to the resistance temperature detectors 15-1 and 15-2 in modification example 1 are used. 25-2 are formed on the fifth layer substrates 23-5 and 23-6, respectively. Note that the same magnetic detection coils 14-1 to 14-4 as in the first modification are formed on the substrates 23-1 to 23-4 from the first layer to the fourth layer. The magnetic detection coils 14-1 to 14-4 and the resistance temperature detectors 25-1 and 25-2 are all arranged in a multilayered manner within the gap region E. However, the meandering length of the central portion of the resistance temperature detectors 25-1 and 25-2 is shorter than that of the resistance temperature detectors 15-1 and 15-2 due to the presence of the vias b2 and b4.

In the second modification, the temperature detection section 12 can be incorporated into the current sensor 10 without increasing the size of the board. Note that since the resistance temperature detectors 25-1 and 25-2 are arranged within the gap region E, the current applied to the resistance temperature detectors 25-1 and 25-2 is applied to the magnetic detection coils 14-1 to 14-2. In order to eliminate the influence on 14-4, direct current will be applied.

<Modification 3>
FIG. 6 is an explanatory diagram illustrating the configuration of the substrate 33 according to the third modification. In Modifications 1 and 2, an example using a multilayer board was shown, but the board 33, which is a multilayer board in Modification 3, is not multilayered by a semiconductor process or the like, but is made by bonding two substrates 33a and 33b. form one substrate. For example, the substrate 33a is a substrate with multilayered magnetic detection coils, and the substrate 33b is a substrate with multilayered temperature sensing resistors.

<Modification 4>
In the above-described embodiment and modifications 1 to 3, it was assumed that the substrates 3, 13, 23, and 33 were arranged in the gap 1a of the magnetic flux collecting core 1, but in the present modification 4, This is applied to a current sensor in which a substrate is arranged around a current bar 2.

FIG. 7 is a perspective view showing a general configuration of a current sensor 43 which is the fourth modification. 8 is a schematic diagram of the current sensor 43 shown in FIG. 7 viewed from the axial direction of the current bar 2. As shown in FIG. 7 and 8, the current sensor 43 detects the current flowing through the current bar 2 by measuring the magnetic field formed around the current bar 2 through which the current flows. In the current sensor 43, two pairs of substrates 43a, 43c, 43b, and 43d on which the same coil pattern is formed are arranged symmetrically with respect to the axis C of the current bar 2, respectively. The four substrates 43a to 43d are provided around the current bar 2 at equal angular intervals and at 90 degree intervals around the axis C of the current bar 2. The substrates 43a to 43d are provided so that the angle between the coil pattern surface on which the coil pattern is formed and the magnetic flux φ to be measured is a right angle.

The coil patterns formed on each of the substrates 43a to 43d are connected in series by a connecting wire 42 so that the induced voltages generated by the magnetic flux φ are sequentially added from the terminal 4a. A return line 41 from the substrate 43d on the terminal end side of the connection line 42 is connected to the terminal 4b on the start end side of the connection line 42 along the connection line 42.

That is, the coil patterns formed on each of the substrates 43a to 43d are formed so that the induced voltages are all in the same winding direction when viewed from the direction of the magnetic flux φ, and are added together, and the induced voltages due to the connection wire 42 and the return wire 41 are I'm trying to cancel out the effects of that.

Here, for example, a substrate 45 on which a temperature-measuring resistor is formed is adhered to the substrate 43a to form one substrate. Note that a current measuring unit 7 is provided in the substrate 43a to measure the current based on the induced voltage from the terminals 4a and 4b, and a temperature is measured in the substrate 45 based on the resistance value obtained from the terminals 5a and 5b. A temperature measuring section 8 may also be provided. Note that a direct current is applied to the temperature measuring resistor in the substrate 45.

Note that the current sensor 43 includes a support case 100 that mainly supports each of the substrates 43a to 43d and 45 around the current bar 2. This support case 100 is formed of an insulating material.

<Power meter>
FIG. 9 is a block diagram showing an example of a power meter 200 using the current sensor shown in the embodiment and modifications 1 to 4. This watt-hour meter 200 measures the three-phase power amount between the power supply SP and the load LD, and calculates it by the two-wattmeter method. Note that FIG. 10 shows a vector diagram between the three-phase currents IR, IS, and IT and the three-phase voltages VR, VS, and VT.

As shown in FIG. 9, the watt-hour meter 200 includes current sensors 10a and 10b, voltage sensors 201a and 201b, a watt-hour calculation unit 202, an output 203. Current sensor 10a detects an R-phase current signal. Current sensor 10b detects a T-phase current signal. Further, the voltage sensor 201a detects a voltage signal between the R phase and the S phase. Voltage sensor 201b detects a voltage signal between the T phase and the S phase.

The power calculation unit 202 multiplies the current signal of the current sensor 10a and the voltage signal of the voltage sensor 201a to generate an instantaneous power signal, smoothes this with a low-pass filter to obtain active power, and calculates the current of the current sensor 10b. The signal is multiplied by the voltage signal of the voltage sensor 201b to generate an instantaneous power signal, which is smoothed by a low-pass filter to obtain active power, and the active power obtained by adding each active power is calculated as the amount of power. The output unit 203 displays or outputs the calculated power amount to the outside.

In addition, the three-phase power P obtained by the two-wattmeter method is
P=VRS・IR+VTS・IT
=(VR-VS)・IR+(VT-VS)・IT
=VR・IR+VS・(-IR-IT)+VT・IT
=VR・IR+VS・IS+VT・IT
This is the same as finding the power that is the sum of the power of each phase.

Note that in the above embodiments and modifications, the temperature is measured using a resistance temperature sensor, but the present invention is not limited to this; for example, a thermocouple may be formed on the substrate to measure the temperature. It's okay.

Moreover, each structure illustrated in the above-described embodiments and modified examples is functionally schematic, and does not necessarily need to be physically configured as illustrated. In other words, the form of dispersion/integration of each device and component is not limited to the one shown in the diagram, but all or part of it may be functionally or physically dispersed/integrated in arbitrary units depending on various usage conditions. It can be configured as follows.

1 Magnetic collecting core 1a Gap 2 Current bar 3, 13, 13-1 to 13-4, 23, 23-1 to 23-6, 33, 33a, 33b, 43a to 43d, 45 Board 4, 14-1 to 14 -4 Magnetic detection coil 4a, 4b, 5a, 5b, 9 Terminal 5, 15-1, 15-2, 25-1, 25-2 RTD 6 Measuring section 7 Current measuring section 8 Temperature measuring section 10, 10a , 10b, 43 Current sensor 11 Current detection section 12 Temperature detection section 14a Wiring 41 Return line 42 Connection line 100 Support case 200 Energy meter 201a, 201b Voltage sensor 202 Energy calculation section 203 Output section b1 to b6, b11 to b13 Via C axis E gap area IR, IS, IT three-phase current LD load P three-phase power SP power supply VR, VS, VT three-phase voltage φ magnetic flux

Claims (3)

a current bar through which the current to be detected flows;
a magnetic detection coil that detects magnetism corresponding to the current as an induced voltage;
A current sensor comprising a measurement unit that measures the current based on the induced voltage generated in the magnetic detection coil,
A temperature detection unit for detecting temperature is provided on a substrate on which the magnetic detection coil is arranged,
The magnetic detection coil is a coil pattern formed on the substrate,
The temperature detection unit forms a temperature sensing resistor pattern on the substrate, which is electrically separated from the coil pattern, and detects the temperature based on a change in the resistance value of the pattern ,
A current sensor characterized in that the pattern of the temperature sensing resistor is arranged in the same area as the arrangement area of the magnetic detection coil and on a different layer of the substrate. 2. The current sensor according to claim 1 , wherein the magnetic detection coil is disposed in one or more gaps formed in a magnetic collecting core formed to surround the current bar. A power meter, characterized in that the amount of power flowing through the current bar is calculated based on a current signal detected by the current sensor according to claim 1 or 2 and a voltage signal detected by a voltage sensor.

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