CN111458550A - Current sampling circuit structure and device with wide current variation range - Google Patents
Current sampling circuit structure and device with wide current variation range Download PDFInfo
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- CN111458550A CN111458550A CN201910049077.0A CN201910049077A CN111458550A CN 111458550 A CN111458550 A CN 111458550A CN 201910049077 A CN201910049077 A CN 201910049077A CN 111458550 A CN111458550 A CN 111458550A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/0092—Arrangements for measuring currents or voltages or for indicating presence or sign thereof measuring current only
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R35/00—Testing or calibrating of apparatus covered by the other groups of this subclass
- G01R35/04—Testing or calibrating of apparatus covered by the other groups of this subclass of instruments for measuring time integral of power or current
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Abstract
The invention provides a current sampling circuit structure and a device suitable for a circuit with a wide current change range. The invention solves the problems that the current range of the electric energy meter is smaller, the application range of the electric energy meter is greatly expanded, and the measurement precision of the sampling circuit of the electric energy meter is effectively improved.
Description
Technical Field
The invention belongs to the technical field of power supply circuits, relates to a sampling circuit structure, and particularly relates to a current sampling circuit structure and a current sampling device.
Background
In recent years, the global demand for intelligent electric energy meters is increasing, and the quantity of electric energy meters in regions such as Europe and southeast Asia exported in China is also increasing year by year. At present, the standard of the small current and the standard of the large current of the three-phase electric energy meter commonly used in China are 1(10) A, and the standard of the large current is 20(200) A, but the current measurement precision of the electric energy meters with different calibration standards is different, namely the measurement precision of the electric energy meter with the large calibration current can not meet the requirement of the electric energy meter with the small calibration current. Therefore, the electric energy meter with large calibration current cannot be applied to a small current circuit, so that the current range applicable to the domestic electric energy meter is small, the circuit environment applicable to a single electric energy meter is limited, and the increasing demands of domestic users are difficult to meet.
For foreign users, especially users in European regions, the requirement on the applicable current range of the electric energy meter is generally higher than the current requirement in China, so that the current electric energy meter commonly used in China is difficult to meet the requirement on the applicable current range of the electric energy meter by the foreign users, especially the users in European countries, and the requirement on the measurement accuracy of the electric energy meter in foreign countries is generally higher than the current IEC or ANSI standard requirement in China.
Disclosure of Invention
In view of the above disadvantages of the prior art, an object of the present invention is to provide a current sampling circuit structure and device, which are used to solve the problems that the current sampling range of the domestic existing electric energy meter is narrow and the electric energy meter cannot work in a wide current range, and achieve that the same electric energy meter can work under a large current signal, and the measurement precision of the sampling current under a small current signal meets the requirement of IEC or ANSI standard on the measurement accuracy of the electric energy meter current meter.
To achieve the above and other related objects, the present invention provides a current sampling circuit structure suitable for a circuit with a wide current variation range, the current sampling circuit structure comprising: the current transformer comprises a primary side winding and a secondary side winding; the secondary side active circuit comprises a signal amplification module which is used for amplifying a current signal obtained by the secondary side winding of the current transformer through electromagnetic induction, and the amplified current signal is fed back to the secondary side winding of the current transformer through the secondary side active circuit so as to realize the dynamic balance of the primary magnetic potential and the secondary magnetic potential of the current transformer.
In an embodiment of the present invention, the current transformer includes an iron core sleeved on the input wire and a bifilar secondary power coil wound on the iron core, and the bifilar secondary power coil includes two sub-windings connected through the secondary side active circuit, which are a secondary detection winding and a secondary measurement winding respectively.
In an embodiment of the present invention, the secondary side active circuit further includes a protection module, an adjustment detection module, and a filtering module, and is connected to the signal amplification module.
In an embodiment of the invention, the signal amplifying module and the filtering module are connected in series with the secondary detection winding and the secondary measurement winding.
In an embodiment of the present invention, the protection module is connected in parallel to two ends of the secondary detection winding, and is configured to perform amplitude limiting on a current signal output by the secondary detection winding.
In an embodiment of the invention, the signal amplifying module includes an inverse proportion operational amplifying circuit, a non-inverting input terminal of the inverse proportion operational amplifying circuit is grounded, a non-inverting input terminal of the inverse proportion operational amplifying circuit inputs the current signal output by the secondary detection winding, and an output terminal of the inverse proportion operational amplifying circuit is connected to the filtering module.
In an embodiment of the invention, an operational amplifier in the inverse proportional operational amplifier circuit is connected to an external power source.
In an embodiment of the invention, the adjustment detection module is connected in parallel with the operational amplifier in the inverse proportional operational amplifier circuit, and is configured to adjust a current phase in the signal amplification module.
In an embodiment of the present invention, one end of the filtering module is connected to the signal amplifying module, and the other end of the filtering module is connected to the secondary measurement winding of the current transformer; the filter is used for filtering a direct current bias signal in the current signal and passing an alternating current signal.
In an embodiment of the invention, the secondary side active circuit is grounded after passing through a load resistor, and the load resistor is used for transmitting a current signal in the secondary side active circuit to an external circuit.
The invention also provides a current sampling device comprising the circuit structure of any one of the current sampling circuit structures.
As described above, the current sampling circuit structure and apparatus of the present invention have the following advantages:
according to the invention, the signal amplification module is arranged in the secondary side active circuit, so that the amplification processing of the secondary side winding sampling signal of the current transformer is realized, and the dynamic balance of the magnetic potential of the primary side and the secondary side of the electromagnetic transformer is achieved, thereby effectively enlarging the current measurement range applicable to the current sampling circuit of the electric energy meter and solving the problem of small current range applicable to the current sampling circuit of the existing electric energy meter; the invention effectively reduces the internal error of the current transformer, improves the measurement precision of the current sampling circuit of the electric energy meter, meets the requirement on the measurement accuracy of the current meter of the electric energy meter even higher than that in the IEC or ANSI standard, and meets the differentiated product requirements of different countries and different customers.
Drawings
Fig. 1 is a schematic structural diagram of a current sampling circuit structure according to an embodiment of the present invention.
Fig. 2 is a circuit diagram 1 of a current sampling circuit structure according to an embodiment of the invention.
Fig. 3 is a circuit diagram of a current sampling circuit structure according to an embodiment of the invention shown in fig. 2.
Description of the element reference numerals
Current sampling circuit structure
11 Current transformer
12 secondary side active circuit
13 load resistor R5
112 primary side winding
113 secondary detection winding
114 secondary measurement winding
121 protection module
122 signal amplifying module
123 adjustment detection module
124 filtering module
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It is to be noted that the features in the following embodiments and examples may be combined with each other without conflict.
It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention, and the components related to the present invention are only shown in the drawings rather than drawn according to the number, shape and size of the components in actual implementation, and the type, quantity and proportion of the components in actual implementation may be changed freely, and the layout of the components may be more complicated.
Example one
Referring to fig. 1, the present invention provides a current sampling circuit structure, which includes an electromagnetic transformer 11 and a secondary side active circuit 12.
Referring to fig. 2, fig. 2 is a specific structure of a current sampling circuit according to the present invention. The current transformer 11 is not limited in kind, and may be a common current transformer, including an iron core, a primary winding, and two secondary windings wound around the iron core. The primary winding 112 of the current transformer is connected with an external circuit to be tested, and the external circuit to be tested inputs a primary side current signal in the primary winding 112; the two secondary side windings are respectively a secondary detection winding 113 and a secondary measurement winding 114, and are in circuit communication through the secondary side active circuit 12. The detection winding 113 performs small current sampling on the input current in the primary winding 112 through electromagnetic induction, the sampled small current signal is amplified by the secondary active circuit 12 to form active current which is input into the measurement winding 114, and the generated magnetic flux demagnetizes the iron core, so that the magnetic potential balance of the two sides of the primary side and the secondary side of the current transformer is achieved.
As shown in fig. 3, the secondary side active circuit 12 is connected in series with the detection winding 113 and the measurement winding 114 of the current transformer 11, and includes a protection module 121, a signal amplification module 122, an adjustment detection module 123, and a filtering module 124; the secondary side active circuit is connected in series with the detection winding 113 of the current transformer 11, and then is connected in series with the measurement winding 114 of the current transformer 11 sequentially through the protection module 121, the signal amplification module, the adjustment detection module and the filtering module; then, the load resistor 13 is connected to an external circuit, which may be an ADC circuit or another circuit, and will not be described here.
The protection module 121 in the secondary side active circuit may be more than two diodes connected in parallel in an inverse direction, and is connected in parallel to two ends of the detection winding 113 of the current transformer, so as to perform an amplitude limiting function on a secondary side induced current signal output by the detection winding 113, that is, limit the size of the signal, and prevent an excessive signal from entering a subsequent secondary side active circuit due to an inrush current input by a primary side of the current transformer. The protection module may also be other structures that can protect the above circuits, and only one structure will be described herein, and other structures will not be described again.
The signal amplification module is an inverse proportion operational amplification circuit, wherein the inverse phase input end of the operational amplifier is connected with the induced current signal output by the detection winding coil through the input resistor R1, the in-phase input end of the operational amplifier is connected with the balance resistor R4 and then is grounded, and the output end of the operational amplifier is connected with the filter module circuit. A feedback resistor R3 is connected between the inverting input end and the output end of the operational amplifier and is a feedback loop of the operational amplifier, and the feedback resistor R3 and the input resistor R1 are used for adjusting the amplitude amplification factor of a current signal in the inverse proportion operational amplification circuit. The operational amplifier is powered by an external power supply and can be powered by double power supplies.
The adjusting and detecting circuit is a circuit formed by serially connecting a capacitor C1 and a load resistor R2 and is connected to two ends of an operational amplifier feedback loop in the inverse proportion operational amplifying circuit in parallel, and the input resistor R1, the load resistor R2 and the capacitor C1 act together and are used for adjusting the phase of a current signal in the inverse proportion operational amplifying circuit. The capacitor C1 forms a high-pass filter, which is used to pass high-frequency signals, to filter interference signals in the current signals, and to prevent self-excitation, so that the input current signals are more stable.
The filtering module is a filtering blocking capacitor, the input end of the filtering module is connected in series with the output end of the inverse proportion operation amplifying circuit, and the output end of the filtering module is connected with the measuring winding 114 of the current measuring transformer 11 and then connected with a load resistor R5. The filtering module may also be other circuit structures capable of implementing the same filtering function, and only one structure mode is described here, and other modes are not described again.
The load resistor R5 is used to convert the active current signal outputted from the measurement winding 114 into a voltage signal, and transmit the voltage signal to an external current sampling circuit (e.g., an analog-to-digital conversion circuit) for measurement.
The working principle of the current sampling circuit structure is as follows:
the secondary side active circuit 12 samples the secondary side current of the current transformer 11 at the detection winding 113, amplifies and filters the secondary side current, and transmits the secondary side current to the measurement winding 114 of the current transformer 11. According to kirchhoff's law of magnetic circuit: the total magnetic flux penetrating out of or entering any closed surface is constantly equal to 0, and the demagnetization of the iron core of the electromagnetic transformer by the magnetic flux generated by the current signal in the measurement winding 114 is realized by adjusting the signal amplification factor and the signal phase in the signal amplification module, so that the primary side magnetic potential and the secondary side magnetic potential of the current transformer 11 reach a dynamic balance state, the specific difference and the angular difference of the electromagnetic transformer are reduced, the current measurement precision of the current sampling circuit is improved, and the application range of the current sampling circuit structure is effectively expanded.
The working process of the current sampling circuit structure is as follows:
as shown in fig. 3, after a current signal is input at the primary side of the current transformer 11, an induced current signal Itest is generated by the detection winding 113 through electromagnetic induction, and is transmitted to the signal amplification module through the protection module, after the induced current signal Itest is amplified by the signal amplification module, the current signal is filtered by the filter module and is transmitted to the measurement winding 114 of the current transformer 11, so that the dynamic balance between the magnetic potentials at the primary side and the secondary side of the current transformer is realized, and the internal error of the current transformer is reduced. Finally, the current signal output by the measurement winding 114 is converted into a voltage signal by a load resistor R5, and is transmitted to an external current sampling circuit or other external circuits.
In this embodiment, an original alternating current source signal having a wide variation range is input to the primary side of the current transformer, and the current variation width may be 1Ma to 200A or larger. The number of turns of the detection winding 113 of the current transformer is larger than that of the primary winding, so that a small current signal is generated in the coil of the detection winding 113 through electromagnetic induction, that is, a small current is sampled for the primary side input current. According to kirchhoff's law of magnetic circuit:
I1×N1+I2×N2+Itest×Ntest–Ig×N1＝0
i1 is input current of the primary side of the current transformer; n1 is the primary side winding number of turns of the current transformer; i2 is a winding current measured by the secondary side of the current transformer; n2 is the number of winding turns measured by the secondary side of the current transformer; ntest is the number of turns of a secondary side detection winding of the current transformer; itest is the current of the secondary side detection winding of the current transformer; ig denotes the excitation current of the current transformer.
At the moment when the current transformer I1 inputs the current signal I1 in the primary winding, the current I2 in the measurement winding is not yet generated, and at this time, since the magnetic density in the iron core of the electromagnetic transformer is small, the Ig exciting current is small, and the current signal Itest ≈ N- (N1/Ntest) × I1 generated by electromagnetic induction in the coil of the detection winding 113.
The current Itest output by the detection winding 113 forms a stable current signal I2 which is amplified by a certain proportion a after signal amplification and filtering processing of the secondary side active circuit 12, the current signal I2 generates a new magnetic field at the measurement winding 114 of the current transformer 11, the size of the generated magnetic field is opposite to the direction of the magnetic field generated by the primary side input current I1, namely the phase of the secondary side magnetic flux of the current transformer is opposite to the phase of the primary side, the effect of demagnetizing the iron core is achieved, the magnetic potential balance of the primary side and the secondary side of the current transformer is realized, and the internal errors of the current transformer, including a ratio difference and an angle difference, are greatly reduced. In an ideal state, when the amplification factor of the operational amplifier circuit in the secondary active circuit may be infinite, and when the sampling current of the secondary detection winding 113 is very weak and close to 0, the magnetic flux density of the magnetic field formed in the iron core by the primary current for generating the sampling current through electromagnetic induction is correspondingly very weak, the corresponding excitation current Ig for generating the magnetic field is also very weak and close to 0, and almost all of the active current I2 in the measurement winding 114 is generated by the operational amplifier circuit through amplification. Since the excitation current Ig is also very weak and close to 0, the ratio difference and the angular difference in the active current I2 are also infinitely close to 0, and the accuracy of the output current under any input current condition can be ensured. In the actual current sampling circuit, a certain sampling current Itest necessarily exists in the detection winding 113, i.e., Itest is not equal to 0, so that the actual active current I2 can only approach the state and cannot reach the state, i.e., a certain ratio difference and angular difference still exist in I2.
In the secondary side active circuit, the amplification factor of the operational amplifier is adjusted by selecting the operational amplifiers with different performance parameters (amplification performance) and adjusting the input resistor and the feedback resistor in the amplification circuit, and the amplified signal is fed back to the input end through the feedback circuit to obtain a stable output signal, so that the internal error of the current sampling circuit can be greatly reduced.
When the primary side input current of the current transformer is I1', the current formed at the secondary side winding by electromagnetic induction is I2' and the exciting current for forming a magnetic field is Ig 'for the ordinary current sampling circuit, I1', I2 'and Ig' satisfy the conditions that I1'× N1+ I2' × N2-Ig '× N1 is 0, and I2' - (I2 '2N 2-Ig' 2N 2)/N2 for the current sampling circuit described in the invention, when the sampling current of the detection winding is It, the amplification factor A of the signal amplification module in the secondary side active circuit is adjusted to ensure that the current measured at the secondary side winding is I2, the current is reduced by 1/A, the magnetic flux density of the primary side input current is reduced by the ideal current when the current is I2, the current is reduced by the proportion of the secondary side input current, I2 is I2, the current is reduced by the proportion of the magnetic flux I2, the secondary side input current is I2, and the magnetic flux density of the secondary side winding is reduced by the ideal current I2, I2 is reduced by the normal magnetic flux density of the iron core 2.
In one embodiment, the current transformer adopts a common 0.1-grade current transformer with a rated current of 20(200) A, and the minimum current which can be accurately measured according to the GB1208-1997 standard is 1% of the rated current, namely 20 x 1% ═ 0.2A, namely 200 mA. When an input current signal of 1mA is input at the primary side input end of the current transformer, the minimum current which can be accurately measured by the current transformer is 200 mA; compared with the output current of the secondary side under an ideal state, the output current of the secondary side of the common current sampling circuit without utilizing the invention has an error of about 200 percent, and the error value is far larger than the error range specified by the standard.
When the same current transformer is used, and the amplification factor a of the inverse proportion operation amplifying circuit is adjusted to be 1000 by using the current sampling circuit structure provided by the invention, when an input current signal of 1mA is input at the primary side winding of the current transformer, after signal processing of the secondary side active circuit, compared with a common circuit which does not use the current transformer, the error of the secondary side output current is reduced to about 1/1000 ═ 0.10%, namely when the primary side input current is 1mA, the error can be reduced to about 200%/1000 ═ 2% by using the current sampling circuit provided by the invention, thereby greatly reducing the error of the current sampling circuit and improving the measurement accuracy of the current.
In summary, when the input end of the current sampling circuit of the electric energy meter is a small current signal, the invention can greatly reduce the measurement error of the circuit and improve the current measurement accuracy. Therefore, the invention widens the measurement range of the current sampling circuit of the electric energy meter, realizes the accurate measurement of the sampling signal with wide current range by the electric energy meter metering chip, and effectively expands the application range of the existing electric energy meter. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.
Claims (11)
1. A current sampling circuit structure comprising: the current transformer comprises a primary side winding and a secondary side winding; the current sampling circuit structure is characterized in that:
the secondary side active circuit comprises a signal amplification module which is used for amplifying a current signal obtained by the secondary side winding of the current transformer through electromagnetic induction, and the amplified current signal is fed back to the secondary side winding of the current transformer through the secondary side active circuit so as to realize the dynamic balance of the primary magnetic potential and the secondary magnetic potential of the current transformer.
2. The current sampling circuit structure of claim 1, wherein: the current transformer comprises an iron core sleeved on an input wire and a bifilar secondary electricity taking coil wound on the iron core, wherein the bifilar secondary electricity taking coil comprises two sub-windings connected through a secondary side active circuit, namely a secondary detection winding and a secondary measurement winding.
3. The current sampling circuit structure of claim 1, wherein: the secondary side active circuit also comprises a protection module, an adjustment detection module and a filtering module which are connected with the signal amplification module.
4. The current sampling circuit structure of claim 2 or 3, wherein: the signal amplification module and the filtering module are connected with the secondary detection winding and the secondary measurement winding in series.
5. The current sampling circuit structure of claim 2 or 3, wherein: and the protection module is connected in parallel at two ends of the secondary detection winding and is used for limiting the amplitude of an output signal of the secondary detection winding.
6. The current sampling circuit structure of claim 1, wherein: the signal amplification module comprises an inverse proportion operation amplification circuit, the non-inverting input end of the inverse proportion operation amplification circuit is grounded, the inverting input end of the inverse proportion operation amplification circuit inputs the current signal output by the secondary detection winding, and the output end of the inverse proportion operation amplification circuit is connected with the filtering module.
7. The current sampling circuit structure of claim 6, wherein: and an operational amplifier in the inverse proportion operational amplification circuit is connected with an external power supply.
8. The current sampling circuit structure of claim 1, wherein: the adjustment detection module is connected in parallel with an operational amplifier in the inverse proportion operational amplification circuit and is used for adjusting the current phase in the signal amplification module.
9. The current sampling circuit structure of claim 1 or 2, wherein: one end of the filtering module is connected with the signal amplification module, and the other end of the filtering module is connected with a secondary measurement winding of the current transformer; the filter is used for filtering a direct current bias signal in the current signal and passing an alternating current signal.
10. The current sampling circuit structure of claim 1, wherein: the secondary side active circuit is grounded after passing through a load resistor, and the load resistor is used for transmitting a current signal in the secondary side active circuit to an external circuit.
11. A current sampling device, characterized by: the apparatus comprising a current sampling circuit arrangement according to any one of claims 1-10.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910049077.0A CN111458550A (en) | 2019-01-18 | 2019-01-18 | Current sampling circuit structure and device with wide current variation range |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910049077.0A CN111458550A (en) | 2019-01-18 | 2019-01-18 | Current sampling circuit structure and device with wide current variation range |
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| Publication Number | Publication Date |
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| CN111458550A true CN111458550A (en) | 2020-07-28 |
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| CN201910049077.0A Pending CN111458550A (en) | 2019-01-18 | 2019-01-18 | Current sampling circuit structure and device with wide current variation range |
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