KR20120113060A - Instrument tranformer type wide range voltage divider and current divider, measuring device including the divider - Google Patents

Abstract

PURPOSE: A current conversion alternating current depressor for instruments applied to power frequency alternating current measuring device, an alternating current measuring device to which a voltage conversion alternating voltage potentiometer is applied, an alternating current measuring device to which the current conversion alternating current depressor is applied, and an alternating current/voltage measuring device are provided to use a voltage converting device and a current converting device for a power frequency alternating current/voltage measuring device having a maximum range of 2 kV/10A. CONSTITUTION: A primary voltage input terminal(11) is composed of primary windings to receive an AC(Alternating Current) input voltage. The primary windings are wound by a coil insulated against a core as many as the number of primary voltage windings. A secondary voltage output terminal(12) is composed of a secondary windings to partially press the AC input voltage into a suitable size for the input of a digital AC voltage measurement circuit(30). The secondary windings are wound by the coil insulated against the core as many as the number of secondary voltage windings less than the number of the primary voltage windings.

Description

Instrument voltage transformer type AC voltage divider applied to AC voltage current measuring device and AC transformer current transformer having AC current divider type, AC voltage divider and AC current drop current divider, measuring device including the divider}

The present invention relates to an AC voltage divider type for an AC voltage current measuring device and an AC voltage divider for an AC current divider type and an AC voltage current measuring device having an AC voltage divider and an AC current drop, and a measuring method thereof. More specifically, a voltage transformer (PT), which is a wide-range AC voltage divider, and a current transformer, which is a current drop, can be applied to an AC voltage current measuring device having a measuring range of up to 2 kV and 10 A at a commercial frequency. transformer, CT) and its application technology. That is, the voltage transformer (PT) and the current transformer (CT) of the current transformer (PT) and the current transformer (CT) that can be applied to the AC voltage current measurement for measuring AC voltage and current having an AC voltage of up to 2 kV and an AC current range of up to 10 A at a commercial frequency It is about applied technology.

In the case of the AC effective voltage current measuring device, in order to measure AC input voltage of several thousand V, the voltage must be applied to the measurement circuit by dropping the voltage within several V within the effective input voltage range of the measuring circuit. In order to do this, it should be reduced to the range of several hundred mA which is the effective input current range of the measuring circuit and applied to the measuring circuit.

Currently, resistive voltage dividers and capacitive voltage dividers are used to reduce AC voltages of several thousand V to several V. In the case of resistive voltage divider, the stability is excellent, but it is necessary to connect several resistors with a large rated voltage in series. When several high resistances are connected in series, the size of the resistive voltage divider is increased and the high resistance element with excellent stability can be easily There is a disadvantage that cannot be obtained. In addition, the capacitive voltage divider also has the inconvenience of using a large high voltage capacitor device in order to make a capacitive voltage divider having a rated voltage of several thousand V.

In addition, a resistive current shunt can be used to reduce AC current of several tens of amps to several hundred mA, but resistance elements for classifiers with excellent stability cannot be easily obtained. There is a difficulty in accurately evaluating the resistance change due to the heating effect, and also, a precision resistive classifier having excellent stability has a disadvantage in that it cannot be attached to the inside of the measuring instrument due to its large size, for example, to attach a heat sink.

In addition, in the case of the resistive voltage divider, the capacitive voltage divider, and the resistance current divider, it is difficult to miniaturize and there is a problem that is greatly affected by temperature and humidity.

Therefore, there is a need for an AC measuring device using an AC voltage divider for an instrument voltage transformer with a small effect on temperature and humidity and an AC current drop for an instrument current transformer type.

Accordingly, the present invention has been made to solve the above problems, according to an embodiment of the present invention to a voltage transformer (PT) as a wide range AC voltage divider that can be applied to the AC voltage current measuring device to reduce the AC current. By using a current transformer (CT), it is possible to provide an AC voltage current measuring device and a measuring method which have excellent stability and can be manufactured in a small size with little influence of temperature and humidity.

Other objects, specific advantages and novel features of the present invention will become more apparent from the following detailed description and preferred embodiments in conjunction with the accompanying drawings.

The first object of the present invention is a voltage transformer type AC voltage divider for an instrument applied to a commercial frequency AC voltage measuring device. In order to receive an AC input voltage, a coil insulated from an iron core core is wound by the number of primary voltage turns. A primary voltage input stage consisting of a primary winding; And a secondary winding wound with a coil insulated from the same iron core core with a secondary voltage winding less than the primary voltage winding to divide the AC input voltage into a size suitable for the input of the digital AC voltage measuring circuit. It can be achieved as a voltage transformer type AC voltage divider for an instrument applied to a commercial frequency AC voltage measuring device comprising a secondary voltage output stage.

The AC input voltage may range from 2 V to 2000 V, and the output voltage may range from 1 mV to 2 V.

The rated voltage conversion ratio, which is the ratio of the AC input voltage to the output voltage, may be determined by Equation 1 below.

(1)

(V ₁ is AC input voltage, V ₂ is output voltage, N _p1 is primary voltage winding and N _p2 is secondary voltage winding)

The primary side winding may be wound with a coil insulated from an iron core, and the secondary side winding may be wound with a coil insulated from the same core core to be manufactured by molding.

The second object of the present invention, in the current transformer type AC current drop applied to the commercial frequency AC current measuring device, in order to receive the AC input current, wound by the number of primary windings with a coil insulated from the iron core core A primary current input stage consisting of a primary winding; A secondary current output stage consisting of secondary windings wound with more secondary windings than the primary windings in order to drop to a size suitable for a digital alternating current measurement circuit; And a load resistor having a function of converting an AC output current into an AC voltage. It can be achieved as a current transformer type AC current drop for an instrument applied to a commercial frequency AC current measuring device.

The AC input current may range from 10 mA to 10 A, and the output current may range from 0.1 mV to 100 mA.

The ratio of the AC input current to the output current may be determined by Equation 2 below.

(2)

(Where I ₁ is the input current, I ₂ is the output current, N _c1 is the number of primary current turns and N _c2 is the number of secondary current turns)

The primary side winding may be wound with a coil insulated at one end of the iron core core, and the secondary side winding may be wound with a coil insulated at the same core core to be manufactured by molding.

The third object of the present invention is a transformer transformer AC voltage divider applied to a commercial frequency voltage current measuring device, characterized in that it includes the aforementioned voltage transformer transformer AC voltage divider and the instrument current transformer transformer AC current drop. And AC current drop.

A fourth object of the present invention is an AC voltage measuring device to which a voltage transformer type AC voltage divider for an instrument is applied, the AC voltage divider described above; A step of outputting a dropped voltage according to the rated voltage conversion ratio of an AC voltage divider and an effective value / direct current converter that converts an AC voltage output from the AC voltage divider into a DC voltage, and converts it into a digital voltage by receiving an analog DC voltage. The present invention can be achieved as an AC voltage measuring device using an AC voltage divider for an instrument comprising a voltage measuring circuit configured to provide an analog / digital converter and supplying the voltage input unit of a digital AC voltage measuring circuit.

A fifth object of the present invention is to provide an alternating current measuring device to which an instrument current transformer current drop is applied, wherein the instrument current transformer type current drop; Outputting a current dropped according to the rated current conversion ratio of the AC current dropper; A current / voltage conversion step of converting an AC current output from the AC current drop into a voltage at a resistor connected to the secondary side of the AC current drop; An effective value / direct current conversion step of converting an AC effective value voltage converted on the secondary side of the current drop into a DC voltage, and an analog / digital converter that converts an analog DC voltage to a digital voltage to form a current in a digital AC voltage measuring circuit. It can be achieved as an AC current measuring device applying the current transformer type current drop for the instrument, characterized in that it comprises a current measuring circuit through the step of supplying to the input unit.

A sixth object of the present invention can be achieved as an AC voltage current measuring device comprising the above AC flow voltage measuring device and the above AC current measuring device.

Therefore, according to one embodiment of the present invention as described, by using a voltage transformer (PT) and a current transformer (CT) for a commercial frequency AC voltage current measuring device having a maximum range of 2 kV / 10 A, 1 V As a result of dividing a 60 Hz AC input voltage in the range of ~ 2 kV with a voltage transformer, an output voltage accuracy of -0.17% to -0.03% can be obtained in the range of 1 mV to 2 V.

The voltage divider having this accuracy is determined to be suitable for an input circuit of an AC voltage measuring device having a maximum measuring voltage of 2 kV and an accuracy of 3% or less. When the conventional resistance voltage divider or capacitive voltage divider is adopted, the voltage transformer is large in size and is not employed in a portable AC voltmeter. However, the voltage transformer applied to the present invention is easy to manufacture, small and light, and is movable in a wide range with one voltage transformer. It has the advantage that it can be applied to AC voltage measuring circuit.

In addition, according to an embodiment of the present invention as a result of dropping a 60 Hz AC input current in the range of 10 mA to 10 A with a current transformer (CT), output current in the range of -0.17% to -0.02% in the range of 0.1 mA to 0.1 A This has the effect of obtaining accuracy. The current transformer CT having such an accuracy has a maximum measurement current of 10 A and is determined to be suitable for an input circuit of an AC current meter having an accuracy of 3%.

Conventional resistive classifiers are larger in size when heat sinks are used and are not employed in mobile AC ammeters, while current transformers (CT) according to the present invention are easy to manufacture, compact, lightweight, and mobile CT in a wide range with one CT. The technology applicable to the measuring circuit is the biggest advantage of the present invention. The same advantage can be obtained when using a current transformer (CT) having a rated primary current of 10 A or more.

Although the present invention has been described in connection with the above-mentioned preferred embodiments, it will be appreciated by those skilled in the art that various other modifications and variations can be made without departing from the spirit and scope of the invention, All fall within the scope of the appended claims.

1 is a block diagram of an AC voltage current measuring device applying a voltage transformer and a current transformer according to an embodiment of the present invention;
2 is a circuit diagram of a voltage transformer according to an embodiment of the present invention;
3 is a circuit diagram of a current transformer according to an embodiment of the present invention;
4 is a flowchart of an AC voltage measuring method using an AC voltage transformer according to an embodiment of the present invention;
5 is a table showing the measured output voltage and the output voltage error with respect to the input voltage of the voltage transformer AC voltage divider according to an embodiment of the present invention,
6 is a graph of measurement output voltage and output voltage error with respect to an input voltage of a voltage transformer type AC voltage divider according to an embodiment of the present invention;
7 is a flowchart of an AC current measuring method using an AC current transformer according to an embodiment of the present invention;
8 is a table showing the measured output current and the output current error with respect to the input current of the current transformer type AC current drop according to an embodiment of the present invention.
9 is a graph illustrating a measurement output current and an output current error with respect to an input current of a current transformer-type AC current drop according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the detailed description of known functions and configurations incorporated herein will be omitted when it may unnecessarily obscure the subject matter of the present invention.

The same reference numerals are used for portions having similar functions and functions throughout the drawings. Throughout the specification, when a part is 'connected' to another part, this includes not only 'directly connected' but also 'indirectly connected' with another element in between. do. In addition, "including" a certain component does not exclude other components unless specifically stated otherwise, it means that may further include other components.

Hereinafter, an AC voltage in which a voltage transformer (PT, 10) and a current transformer (CT) 20 having a measurement range of up to 2 kV and 10 A of a commercial frequency according to an embodiment of the present invention are operated. The configuration and operation of the current measuring device 1 will be described. First, FIG. 1 is a block diagram showing the configuration of an AC voltage current measuring device 1 to which a voltage transformer 10 and a current transformer 20 according to an embodiment of the present invention are applied.

As shown in FIG. 1, the AC voltage measuring device 1 according to an embodiment of the present invention includes a voltage transformer 10, a current transformer 20, and an effective value / DC converter 31-1 and 31-2. And a measurement circuit 30 including the analog / digital converters 32-1 and 32-2 and the measurement circuit 33, and a DC power supply and a voltage stabilizer 40.

The AC voltage measuring device 1 according to the embodiment of the present invention divides an AC input voltage up to 2 kV by the voltage transformer 10 and outputs the output voltage, which is the effective voltage, to a DC voltage converter. Convert to DC voltage by (RMS / DC Converter, 31-1). The converted DC voltage is converted into a digital voltage by an analog / digital converter 32-1, and the digital voltage is supplied to the measurement circuit 33. Therefore, by measuring the output voltage applied from the measuring circuit 33, the AC voltage applied to the voltage transformer 10 is eventually measured.

In addition, the current transformer 20 drops the AC input current up to 10 A and outputs 100 mA or less, so that the output current, which is the effective value current, by the burden resistor 23 connected to the secondary side of the current transformer 20. Convert to voltage. That is, the burden resistor 23 corresponds to an AC current / AC voltage converting unit that generates an AC voltage proportional to the output current output from the AC current drop.

The converted AC voltage of 2 V or less is converted into a DC voltage by an RMS / DC converter (31-2). The analog / digital converter 32-2 converts the digital voltage into the digital voltage, and the digital voltage is supplied to the measurement circuit 33. Therefore, by measuring the output current applied from the measurement circuit 33, the AC current applied to the current transformer 20 is finally measured.

That is, since the measuring circuit 30 cannot directly measure an AC voltage of 2 kV or less or an AC current of 10 A or less directly, the voltage transformer 10 and the current transformer 20 make a voltage of 2 V or less and 100 mA or less. It is used to reduce the current to.

In addition, the AC voltage current measuring device 1 according to an embodiment of the present invention further includes a DC power supply and a voltage stabilizer 40 for supplying DC power and stabilizing the DC voltage. 30 may be configured to supply.

Hereinafter, the configuration and principle of the voltage transformer 10 applied to the measuring device 1 according to an embodiment of the present invention will be described in more detail. 2 shows a circuit diagram of a voltage transformer 10 according to an embodiment of the present invention. The voltage transformer 10 according to an embodiment of the present invention is used to drop an AC voltage of several thousand V to an output voltage of several V or so. As shown in FIG. 2, the voltage transformer 10 according to the embodiment of the present invention has a voltage input terminal 11 having a primary winding number N _{P1 to} which an input voltage is applied, and a _dropped voltage having a secondary winding number N _P2 . The output terminal 12 to be outputted and the burden resistor 13 connected to the output terminal 12 side are provided.

By the voltage transformer 10 having the primary winding N _P1 and the number of secondary windings N _P2 , the input voltage of the voltage current measuring instrument can be supplied to a voltage of several V suitable for the AC voltage current measuring circuit 30. For example, in order to drop the AC input voltage of 2 kV to a voltage of several V, the following conversion principle is applied to the voltage transformer 10. That is, when the input voltage, which is the primary voltage input to the input terminal 11 of the voltage transformer 10, is referred to as V ₁ , and the secondary voltage output from the output terminal 12 is referred to as V ₂ , Equations 1 and 2 below. Is established.

Where Kp is the rated voltage conversion ratio.

For an ideal voltage transformer 10, the rated voltage conversion ratio (K _P) The rated voltage transformation ratio is equal to the ratio (V ₁ / V ₂ ) of the primary voltage (V ₁ ) and the secondary voltage (V ₂ ) as shown in Equation 1, and also the winding ratio (N) of the voltage transformer 10. _P1 / N _P2 ). As shown in Equation 2, the voltage V ₁ supplied to the primary of the voltage transformer 10 may be calculated from the product of the secondary voltage V ₂ of the voltage transformer 10 and the rated voltage conversion ratio K _P. have. In other words, by measuring the secondary low output voltage (V ₂ ) in the measuring circuit 30 and multiplying the voltage rating conversion ratio (K _P ) by a known voltage, the primary voltage (V ₁ , input voltage) of the AC voltage transformer 10 is measured. Can be calculated accurately. On the contrary, the secondary voltage V ₂ can be calculated by dividing the primary voltage V ₁ by the rated voltage conversion ratio K _P.

For example, if the primary (N _P1 ) and secondary windings (N _P2 ) of the voltage transformer 10 are 4000 times and four times, respectively, the rated conversion ratio K _P is 1000, and thus the input voltage of 2 kV (V ₁ ). When applied, the secondary voltage V ₂ of the voltage transformer 10 becomes 2V. As such, when the rated voltage conversion ratio K _{P of the} voltage transformer 10 is correctly known and the secondary voltage V _{2 of} the voltage transformer 10 is accurately measured, the primary voltage V ₁ , of the voltage transformer 10 is measured. It can be seen that AC input voltage) can be calculated accurately. In this way, the second voltage V ₂ of the divided voltage transformer 10 may be supplied to the AC voltage measuring circuit 30 to measure the input voltage V ₁ of 2 kV.

Voltage transformer 10 has a primary high input voltage (V ₁₎ for converting a low secondary voltage of the output voltage (V _2), and precisely measuring an output voltage (V ₂₎ converting the rated voltage of the AC voltage of the ratio ( By multiplying K _P ) by calculating the primary voltage (V ₁ ) it is possible to measure the high voltage input voltage (V ₁ ).

The secondary rated voltage of the general voltage transformer 10 is fixed at 110 V, and the primary rated voltage is in the range of 110 V to 765 kV depending on the measurement range. In addition, the voltage transformer 10 is a coil having excellent insulation so that the error of the rated voltage conversion ratio (K _P ) is small in the toroidal core core having a high permeability, and winding and molding the primary and secondary sides in a special method. Therefore, the rated voltage conversion ratio (K _P ) is not affected by temperature and humidity, and therefore, the long-term stability of the rated voltage conversion ratio (K _P ) has an advantage that it can be used as an ultra high precision measuring instrument of AC high voltage.

The above-mentioned primary voltage turns (N _P1 ) and secondary voltage turns (N _P2 ) are just one preferred embodiment and should not be construed as being limited thereto. In another embodiment, the primary voltage turns N _P1 is 8000 times the secondary voltage turns N _P2 , or the primary voltage turns N _P1 2000 times the secondary voltage turns N _P2. It may be configured twice to the rated voltage conversion ratio (K _P ) to 1000, and the other turns ratio may be variously set according to the range that the measurement circuit 30 can accurately measure.

Hereinafter, the configuration and principle of the current transformer 20 to be applied to the AC voltage measuring device 1 according to an embodiment of the present invention will be described in more detail. 3 shows a circuit diagram of a current transformer 20 according to an embodiment of the present invention. As shown in FIG. 3, the current transformer 20 according to the embodiment of the present invention has a current input terminal 21 having a primary winding number N _{C1 to} which an input current is applied, and a dropped current having a secondary winding number N _C2 . Is provided with an output terminal 22 for outputting a charge resistor 23 for converting a current connected to the output terminal 22 side into a voltage.

For example, in order to lower the AC input current I ₁ of 50 A to the output current I ₂ of several hundred mA, the following conversion principle of the current transformer 20 is applied.

That is, the primary side current (I ₁ , input current) and secondary side current (I ₂ , output current) of the current transformer 20 are respectively I _1. And _I2 In this case, the following Equations 3 and 4 are established.

Where K _c is the rated current conversion ratio, N _c1 is the number of turns wound on the primary side, and N _c2 is the number of turns wound on the secondary side.

The ideal current transformer 20, the rated current conversion ratio (K _C, rated current transformation ratio) In the case of the primary current, as shown in equation (3) (the input current, I ₁₎ and the secondary current (output current, I ₂₎ Is equal to the ratio (I ₁ / I ₂ ), and is inversely proportional to the winding ratio (N _C2 / N _C1 ) of the current transformer 20.

As shown in Equation 4, the input current I ₁ supplied to the input terminal 21 of the current transformer 20 is the output current I ₂ and the rated current conversion ratio outputted to the output terminal 22 of the current transformer 20. It can be calculated from the product of (KC). In other words, by accurately measuring the small output current (I ₂ ) of the secondary side and multiplying by the known rated current conversion ratio (K _c ), it is possible to accurately calculate the input current (I ₁ ), which is the primary current of the current transformer 20. . On the contrary, the output current I ₂ as the secondary current can be obtained by dividing the input current I _{1 as the} primary current by K _c .

For example, if the number of turns N _c1 wound on the primary side of the current transformer 20 is 10 times and the number of turns N _c2 wound on the secondary side is 1000 times, the rated current conversion ratio K _C is 100. do. Thus, for example, when an input current I ₁ of 10 A is applied to the input terminal 21, the secondary current (output current I ₂ ) output to the output terminal 22 of the current transformer 20 is 100 mA. Becomes

As such, when the rated current conversion ratio K _{c of the} current transformer 20 is correctly known and the secondary current I _{2 of the} current transformer 20 is accurately measured, the primary current I ₁ of the current transformer 20 is measured. It can be seen that can be measured accurately. The output current I ₂ reduced to about several hundred mA in this manner is supplied to the AC current measuring circuit 30 to measure the AC input current I ₁ of about several tens A.

That is, the current transformer 20 converts a large input current I1 of several tens of A or less applied to the input terminal 21 into an output current I ₂ of 100 mA or less of the measurement circuit 30, thereby measuring the measurement circuit 30. ) Is applied to precisely measure this output current (I ₂ ) and calculate the input current (I ₁ ) by multiplying the set rated current conversion ratio (Kc).

In addition, since the current transformer 20 is wound around the core core with a coil having excellent insulation and molding, the rated current conversion ratio K _C of the current transformer 20 is less affected by temperature and humidity. Since the long-term stability of K _C ) is excellent, it can be used as an ultra-precision measuring instrument of alternating current versus current.

The above-mentioned primary current winding number (N _C1 ) and secondary current winding number (N _C2 ) are provided only one preferred embodiment and should not be interpreted as being limited thereto. In another embodiment, the primary current winding number N _C1 is five times the secondary current winding number N _c2 is 500 times or the primary current winding number N _C1 is 20 times the secondary current winding number N _c2 . It is also possible to configure the rated current conversion ratio (K _c ) to 100 by 2000 times, and other winding ratios may be variously set according to the range in which the measurement circuit 30 can accurately measure.

Hereinafter, an AC voltage measuring method using the AC voltage measuring device 1 according to an embodiment of the present invention will be described. 4 is a flowchart illustrating an AC voltage measuring method using the voltage transformer 10 according to an exemplary embodiment of the present invention. First, the AC input voltage V ₁ to be measured is supplied to the input terminal of the voltage transformer (S10-1).

In addition, the voltage drop 10 outputs the output voltage V ₂ dropped in accordance with the rated voltage conversion ratio K _p to the output terminal 12 (S20-1). The principle of the voltage drop is the same as the operating principle of the voltage transformer 10 described above.

Next, the output voltage V ₂ is converted into a DC voltage by the effective value / DC converter 31-1 (S30-1), and the DC voltage is converted into a digital voltage by the analog / digital voltage converter 32-1. (S40-1). Then, the converted digital voltage is supplied to the AC voltage current measurement circuit 33 to accurately measure the output voltage V ₂ (S50-1).

The AC input voltage is calculated by multiplying the output voltage V ₂ by the known voltage conversion ratio Kp to measure the AC input voltage (S60-1).

Figure 5 shows a table showing the measured output voltage and the output voltage error for the input voltage according to the experimental example of the voltage transformer type AC voltage divider of the present invention. As shown in FIG. 5, in the experimental example, the first term on the left side is an input voltage (V ₁ , V) applied to the input terminal 11 of the voltage transformer 10, and the second term converts the input voltage to a rated voltage. The theoretical calculated value (rated output voltage, V) divided by the ratio (K _P ) is the output voltage of the ideal voltage transformer 10 without error in the conversion ratio. The third term is the output voltage (V ₂ ) measured at the output stage 12 of the voltage transformer 10, and the last term is the error of the theoretical rated output voltage of the actual measured output voltage (V ₂ ). will be.

As shown in FIG. 5, the characteristics and accuracy of the output voltage V ₂ according to the input voltage V ₁ of the voltage transformer 10 having a maximum of 2 kV can be known. Since the minimum input voltage of the test example was 1 V and the conversion ratio K _p of the voltage transformer 10 was 1000, the rated output voltage at this time was 1 mV, and the maximum input voltage of the test example was 2 kV, so the rated output at this time was The voltage is 2 V.

That is, 2 V becomes the maximum voltage input to the AC voltage current measuring circuit 30. In the ideal voltage transformer 10 having no conversion error, the output voltage V ₂ should be equal to the rated output voltage even though the input voltage V ₁ is as small as a few V, but the error increases due to the limitation of the iron core permeability. It can be seen that. As the input voltage (V ₁ ) increases, the error decreases, and the maximum error is about-0.3%. Therefore, as the AC voltage divider of the high voltage AC voltage AC measuring device (1) having an accuracy of 3% or less in the input voltage range of 1 V to 2 kV. The accuracy of the voltage transformer 10 to be utilized is determined to be sufficient.

6 illustrates an input voltage and an output voltage graph according to an experimental example of the voltage transformer 10 according to an embodiment of the present invention. A graph showing each point shown in FIG. 6 as a square shows a measured output voltage V ₂ according to an input voltage V ₁ , and a graph showing each point as a circle shows an output according to an input voltage V ₁ . The accuracy of the voltage (V ₂ ), that is, the error (Output Voltage Error (%)) from the theoretical rated output voltage of the measured output voltage (V ₂ ). As shown in FIG. 6, it can be seen that the error decreases as the input voltage increases.

Hereinafter, an AC current measuring method using the AC voltage current measuring device 1 according to an embodiment of the present invention will be described. 7 is a flowchart illustrating an AC current measuring method using the current transformer 20 according to an exemplary embodiment of the present invention. First, the AC input current I ₁ to be measured is applied to the input terminal 21 of the current transformer 20 (S10-2).

Then, the output current I ₂ dropped in the current transformer 20 according to the rated current conversion ratio K _C is outputted to the output terminal 22 (S20-21). The principle of the current drop is the same as the operating principle of the current transformer 20 described above. Next, a voltage proportional to the AC output current of the current transformer 20 is generated in the burden resistor 23. That is, it is converted into an AC voltage proportional to the AC output current (S20-22). The subsequent measuring step is the same as the voltage measuring step.

8 is a table showing the measured output current and the output current error with respect to the input current according to the experimental example of the current transformer current drop of the present invention. As shown in FIG. 8, the experimental example according to the present invention shows the accuracy of the output current I ₂ according to the input current I ₁ of the current transformer 20, and the current transformer 20 used in the test is A current transformer 20 having a maximum rated input current of 10 A and an output current of 0.1 A having a rated current conversion ratio of 100 was used.

Here, the variable of each term is as shown in FIG. 5, the first term on the left side is an input current (I ₁ , unit A) applied to the input terminal 21 of the current transformer 20, and the second term is an input current to a rated current conversion. The theoretical calculated value (rated output current, A) divided by the ratio (K _C ) 100 is the output current of the ideal current transformer 20 without an error in the conversion ratio. The third term is the output current (I ₂ ) measured at the output stage 22 of the current transformer 20, and the last term is the error of the theoretical rated output current of the actual measured output current (I ₂ ). will be.

As shown in FIG. 8, when the input current I ₁ is 10 mA, the output current error is about −0.2% or less, and the accuracy of the output current for the input current I ₁ of 20 mA to 10 A is −0.04. % Or less The current transformer 20 having the above characteristics is determined to have sufficient accuracy of the current transformer 20 to be utilized as the AC current drop of the AC voltage measuring device 1 having an accuracy of 3% or less in the input current range of 10 mA to 10 A. do.

9 illustrates an input current and an output current graph according to an experimental example of the current transformer 20 according to an embodiment of the present invention. In the graph shown in FIG. 9, a graph showing each point as a square shows a measured output current I ₂ according to an input current I ₁ , and a graph showing each point as a circle shows an input current I ₁ . It shows the accuracy (%) of the output current (I ₂ ) according to. As shown in FIG. 9, it can be seen that the error in the range of 0.01 A to 10 A in the input current I ₁ is -0.02% to -0.17%.

1: AC voltage current measuring device
10: voltage transformer
11: input terminal of voltage transformer
12: output stage of voltage transformer
13: burden resistance of the voltage transformer
20: current transformer
21: input terminal of current transformer
22: output stage of current transformer
23: Burden resistance of the current transformer
30: measuring circuit
31-1: RMS / DC Converter
31-2: RMS / DC Converter
32-1: Analog / Digital Converter
32-2: Analog / Digital Converter
33: digital AC voltage current measurement circuit
40: DC power supply and voltage stabilizer
V ₁ : Input voltage and primary voltage of voltage transformer
V ₂ : Output voltage and secondary voltage of voltage transformer
I ₁ : Input current, primary current of current transformer
I ₂ : output current and secondary current of current transformer
N _P1 : Primary winding number of voltage transformer
N _P2 : Number of secondary windings of voltage transformer
N _C1 : primary winding number of current transformer
N _C2 : number of secondary windings of current transformer

Claims (12)

In the instrument voltage transformer type AC voltage divider applied to the commercial frequency AC voltage measuring device,
A primary voltage input terminal comprising a primary winding wound by the number of primary voltage turns with a coil insulated from an iron core core to receive an AC input voltage; And
A secondary winding wound by a coil insulated from the same iron core core with a secondary voltage winding less than the primary voltage winding to divide the AC input voltage into a size suitable for the input of the digital AC voltage measuring circuit. A voltage transformer type AC voltage divider for an instrument applied to a commercial frequency AC voltage measuring device, comprising: a differential voltage output stage.
The method of claim 1,
The AC input voltage ranges from 2 V to 2000 V,
Voltage output transformer type AC voltage divider for the commercial frequency AC voltage measuring device, characterized in that the output voltage is in the range of 1 mV ~ 2 V.
The method of claim 2,
The rated voltage conversion ratio, which is the ratio of the AC input voltage to the output voltage, is a voltage transformer type AC voltage divider for a commercial frequency AC voltage measuring device, which is determined by Equation 1 below.
(1)

(V ₁ is AC input voltage, V ₂ is output voltage, N _p1 is primary voltage winding and N _p2 is secondary voltage winding)
The method of claim 1,
Instrument applied to the commercial frequency AC voltage measuring device, characterized in that manufactured by winding the primary side winding with the coil insulated in the iron core core, winding the secondary side winding with the coil insulated in the same core core Voltage transformer type AC voltage divider.
In current transformer type AC current drop applied to commercial frequency AC current measuring device,
A primary current input stage consisting of primary windings wound by primary windings with a coil insulated from the core core to receive an AC input current;
A secondary current output stage consisting of secondary windings wound with more secondary windings than the primary windings in order to drop to a size suitable for a digital alternating current measurement circuit; And
A load current transformer type AC current drop applied to a commercial frequency AC current measuring device, comprising: a load resistor having a function of converting an AC output current into an AC voltage.
The method of claim 5, wherein
The AC input current ranges from 10 mA to 10 A,
The output current is 0.1 mV ~ 100 mA range, current transformer type AC current drop for instrument applied to commercial frequency AC current measuring device, characterized in that.
The method according to claim 6,
The ratio of the AC input current to the output current is measured by the following equation (2) to the current transformer current transformer type AC current drop applied to the commercial frequency AC current measuring device.
(2)

(Where I ₁ is the input current, I ₂ is the output current, N _c1 is the number of primary current turns and N _c2 is the number of secondary current turns)
The method of claim 5, wherein
Instrument applied to the current measuring device, characterized in that the winding is made by winding the primary side with the coil insulated at one end of the core core and wound by winding the secondary side with the coil insulated on the same core core To reduce the current transformer type AC current.
The transformer transformer type AC voltage divider and alternating current applied to a commercial frequency AC voltage current measuring device, comprising the voltage transformer transformer AC voltage divider of claim 1 and the current transformer transformer type AC current drop of claim 5. Be strong.
In the AC voltage measuring device applying the voltage transformer type AC voltage divider for the instrument,
AC voltage divider of claim 1;
An effective value / DC converter for applying the output voltage output from the AC voltage divider and converting the output voltage into a DC voltage, and an analog / digital voltage converter for converting the DC voltage into a digital voltage by applying the DC voltage to the digital voltage. An AC voltage measuring device using a voltage transformer type AC voltage divider for an instrument, comprising: a voltage measuring circuit configured to measure the output voltage by having a voltage measuring circuit receiving a voltage.
In the AC current measuring device to which the current transformer type current drop for the instrument is applied,
Dropping the current transformer-type current of the instrument of claim 6;
An AC current / AC voltage converter for generating an AC voltage proportional to the output current output from the AC current drop;
An effective value / DC converter for receiving the AC voltage and converting the AC voltage to a DC voltage; And
An analog / digital converter that receives the DC voltage and converts the DC voltage into a digital voltage and a voltage measuring circuit that receives the digital voltage is input to the current drop by measuring the AC voltage in proportion to the output current. An alternating current measuring device to which a current transformer type current drop for an instrument is applied, comprising a measuring circuit for displaying the input current.
An AC voltage measuring device comprising the AC voltage measuring device of claim 9 and an AC current measuring device of claim 11.

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