CN110658374A - Current transformer with wide frequency, wide measurement and anti-magnetic interference capability - Google Patents
Current transformer with wide frequency, wide measurement and anti-magnetic interference capability Download PDFInfo
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- CN110658374A CN110658374A CN201911109810.XA CN201911109810A CN110658374A CN 110658374 A CN110658374 A CN 110658374A CN 201911109810 A CN201911109810 A CN 201911109810A CN 110658374 A CN110658374 A CN 110658374A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
- G01R15/18—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers
- G01R15/183—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers using transformers with a magnetic core
- G01R15/185—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers using transformers with a magnetic core with compensation or feedback windings or interacting coils, e.g. 0-flux sensors
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R1/00—Details of instruments or arrangements of the types included in groups G01R5/00 - G01R13/00 and G01R31/00
- G01R1/02—General constructional details
- G01R1/18—Screening arrangements against electric or magnetic fields, e.g. against earth's field
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
- G01R15/20—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using galvano-magnetic devices, e.g. Hall-effect devices, i.e. measuring a magnetic field via the interaction between a current and a magnetic field, e.g. magneto resistive or Hall effect devices
- G01R15/202—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using galvano-magnetic devices, e.g. Hall-effect devices, i.e. measuring a magnetic field via the interaction between a current and a magnetic field, e.g. magneto resistive or Hall effect devices using Hall-effect devices
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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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Abstract
The invention discloses a current transformer with broadband, wide-range measurement and anti-magnetic interference capabilities, and belongs to the technical field of transformers, wherein a signal conditioning circuit comprises an induction circuit, a differential amplification circuit and a power amplification circuit, a Hall chip of the induction circuit is fixed in an air gap formed in a magnetic core, the output end of the power amplification circuit is connected with one end of a secondary coil, the other end of the secondary coil is connected with the ground after being connected with a first sampling resistor Rm 1in series, the connection point of the first sampling resistor Rm1 and the ground is a signal negative output end M1-, the connection point of the first sampling resistor Rm1 and the secondary coil is a signal positive output end M1+, the signal conditioning circuit further comprises a constant voltage source circuit, and the output end of the constant voltage source circuit is connected with the Hall chip. Under the conditions of wide frequency and wide range and external magnetic interference, the current can still be measured with high precision, the direct current and harmonic components contained in the measured current can be accurately measured, and the measurement is not influenced by a power factor.
Description
Technical Field
The invention belongs to the technical field of transformers, relates to a current transformer, and particularly relates to a current transformer with broadband and wide-width measurement and anti-magnetic interference capabilities.
Background
According to the standard structure of IEC/TC13 and the international suggestion of OIML R46 electric energy meters, China sets up an electric energy measurement and load control standard system corresponding to the standard structure, and under the new situation that a new standard system and a national power grid company are built and arranged in the electric power Internet of things for wide application, higher requirements are provided for the current transformer for the electric energy meter: the conventional electromagnetic current transformer has the defects of complex secondary coil winding process, large temperature error of wound copper wires, large size, nonlinearity, easiness in saturation, small dynamic range, easiness in interference of an external magnetic field and the like, and the requirement of industry development cannot be met. Especially, when the power factor of the new standard system is equal to 0.5L, the direct current and even harmonic wave-half wave rectification waveform test of the electric energy meter stipulates the requirements, and the traditional electromagnetic current transformer can not meet the standard requirements. The research on a novel electronic current transformer for an electric energy meter, which has the advantages of wide dynamic range, high reliability, high sensitivity, high temperature stability and strong magnetic interference resistance, is imperative.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, designs the current transformer with wide-frequency and wide-amplitude measurement and anti-magnetic interference capability, can still realize high-precision measurement on the current in the wide-frequency and wide-amplitude range and under the condition of external magnetic interference, can accurately measure direct current and harmonic components contained in the measured current, and is not influenced by a power factor.
The invention adopts the specific technical scheme that: the utility model provides a current transformer that possesses wide band, broad width measurement and anti magnetic interference ability, includes the shell, sets up magnetic core in the shell, secondary coil and one end that the winding is on the magnetic core are located the shell outside and the other end and cross the inner loop side of bypassing the magnetic core and extend to the outside primary current connection piece of shell, and the key lies in: the current transformer further comprises a signal conditioning circuit arranged in the shell, the signal conditioning circuit comprises an induction circuit, a differential amplification circuit and a power amplification circuit which are sequentially connected, a Hall chip of the induction circuit is fixed in an air gap formed in the magnetic core, the output end of the power amplification circuit is connected with one end of the secondary coil, the other end of the secondary coil is connected with the ground after being connected with a first sampling resistor Rm 1in series, the connection point of the first sampling resistor Rm1 and the ground is a signal negative output end M1-, the connection point of the first sampling resistor Rm1 and the secondary coil is a signal positive output end M1+, the signal conditioning circuit further comprises a constant voltage source circuit, and the output end of the constant voltage source circuit is connected with the Hall chip.
The signal conditioning circuit further comprises a protection circuit connected with the input end of the constant voltage source circuit, the protection circuit comprises a first transient diode TVS1 and a second transient diode TVS2 which are reversely connected in series between the positive input end V + and the negative input end V-of the constant voltage source circuit, and the connection point of the first transient diode TVS1 and the second transient diode TVS2 is connected with the ground.
The induction circuit comprises an eighth resistor R8 and a tenth resistor 10 which are connected in series between a positive output end + V and a negative output end-V of the constant voltage source, and the connection point of the eighth resistor R8 and the tenth resistor 10 is simultaneously connected with the Hall chip H and the differential amplification circuit.
The differential amplifying circuit is a three-operational-amplifier precise differential amplifier consisting of a differential amplifier U2 and peripheral devices thereof, the differential amplifying circuit comprises a third resistor R3 connected between a Hall chip and a third pin of the differential amplifier U2, a twelfth resistor R12 connected between the Hall chip and a fifth pin of the differential amplifier U2, a fourth resistor R4, a sixth resistor R6, a seventh resistor R7, a ninth resistor R9, a fourteenth resistor R14, a thirteenth resistor R13, a connecting point of the fourth resistor R4 and the sixth resistor R6 is connected with a first pin of the differential amplifier U2, a connecting point of the sixth resistor R6 and the seventh resistor R7 is connected with a second pin of the differential amplifier U2, a connecting point of the seventh resistor R7 and the ninth resistor R9 is connected with a sixth pin 2 of the differential amplifier U582, and a connecting point of the ninth resistor R56 and the fourteenth resistor R14 is connected with a seventh pin of the differential amplifier U14, the connection point of the fourteenth resistor R14 and the thirteenth resistor R13 is connected with the twelfth pin of the differential amplifier U2, a fifth resistor R5 is connected between the thirteenth pin and the fourteenth pin of the differential amplifier U2, and the fourteenth pin of the differential amplifier U2 is connected with the power amplification circuit.
The power amplifying circuit comprises a first triode Q1, a second triode Q2, a first diode D1, a second diode D2 and an eleventh resistor R11 which are sequentially connected between the base of the first triode Q1 and the collector of the second triode Q2 in series, the connecting point of the first diode D1 and the second diode D2 is connected with the differential amplifying circuit, the connecting point of the second diode D2 and the eleventh resistor R11 is connected with the base of the second triode Q2, a second resistor R2 is connected between the collector and the base of the first triode Q1, the emitter of the first triode Q1 is connected with the emitter of the second triode Q2, and the connecting point of the emitter and the emitter is connected with the input end of the secondary coil.
The current transformer further comprises a signal conditioning board, the signal conditioning circuit is arranged on the signal conditioning board, the Hall chip is fixedly connected with the signal conditioning board, a clamping groove used for inserting the signal conditioning board is formed in the shell, and the signal conditioning board is inserted into the clamping groove.
The middle of one side plate of the shell protrudes outwards to form a square groove on the inner side, the square groove is located on the outer side of the signal conditioning plate, a power strip pin for connecting a signal conditioning circuit on the signal conditioning plate with the outside is arranged in the square groove, the power strip pin comprises a power lead-in pin pair and a signal output pin pair, the lower ends of the two pins of the power lead-in pin pair are respectively connected with a positive input end V + and a negative input end V-of a constant voltage source circuit, the lower ends of the two pins of the signal output pin pair are respectively connected with a signal output end M1+ and a signal output end M1-, and the upper ends of the two pins of the power lead-in pin pair and the signal output pin pair are all protruded outside the.
Be provided with the circular slot YC on the bottom plate of shell, the lower extreme and the circular slot grafting of the magnetic core that has secondary coil, chip location breach has been seted up with the corresponding position in air gap of magnetic core on the bottom plate, and hall chip pegs graft with chip location breach, has still seted up the connection piece holding tank on the bottom plate, primary current connection piece and connection piece holding tank joint.
Three magnetic cores are arranged in each shell, and correspondingly, the number of the primary current connecting sheet, the number of the Hall chips H and the number of the signal conditioning circuits are all three.
A magnetic shielding layer is arranged on the inner wall of the shell.
The invention has the beneficial effects that: an air gap is arranged on a magnetic core, a Hall chip is arranged in the air gap, a primary current Ip1 flows through a primary winding, namely a primary current connecting sheet, the generated magnetic flux acts on the Hall chip, the Hall chip outputs Hall voltage under certain excitation current Ic, the Hall voltage outputs a secondary current I2 after being amplified by a differential amplifying circuit and a power amplifying circuit, a magnetic field which is offset with the primary current Ip1 is generated by a feedback circuit, the magnetic field in the magnetic core is zero, a current transformer works in a zero magnetic flux mode and is always in a zero magnetic flux compensation state and is not influenced by the linearity of a magnetic circuit and the Hall chip, the temperature drift error is small, the response speed of the whole closed-loop system is high, the dynamic balance establishment time is not more than l mus, the linearity of the current transformer can be better than 0.1 percent, the measurement precision grade is within 0.2 percent, and the measurement error of direct current and even harmonic in an alternating current line is very small, under the condition that the power factors are 1.0 and 0.5L, the error is basically unchanged, and the electromagnetic interference resistance and the external magnetic field interference resistance are strong. The method can be suitable for nondestructive measurement of current signals with wide frequency domain and wide amplitude, and can keep high-precision measurement of current without being influenced by power factors.
Drawings
FIG. 1 is a schematic structural diagram of the present invention.
Fig. 2 is a schematic view of the internal structure of the housing of fig. 1.
FIG. 3 is a schematic block diagram of the circuit for unidirectional current measurement according to the present invention.
Fig. 4 is a circuit diagram of a constant voltage power supply circuit of the present invention.
FIG. 5 is a circuit diagram of an inductive circuit of the present invention.
Fig. 6 is a circuit diagram of the differential amplifier circuit of the present invention.
Fig. 7 is a circuit diagram of a protection circuit of the present invention.
Fig. 8 is a circuit diagram of a power amplifier circuit according to the present invention.
In the drawing, 1 represents a housing, 2 represents a magnetic core, 3 represents a secondary coil, 4 represents a primary current connection piece, 5 represents an air gap, 6 represents a hall chip, 7 represents a signal conditioning board, 8 represents a card slot, 9 represents a square slot, 10 represents a pin, 11 represents a circular slot, 12 represents a chip positioning notch, 13 represents a connection piece accommodating slot, 14 represents a differential amplifier circuit, 15 represents a power amplifier circuit, 16 represents a constant voltage power supply circuit, and 17 represents a protection circuit.
Detailed Description
The invention is described in detail below with reference to the following figures and specific embodiments:
in the specific embodiment, as shown in fig. 1 to 8, a current transformer with broadband, wide-range measurement and anti-magnetic interference capability includes a housing 1, a magnetic core 2 disposed in the housing 1, a secondary coil 3 wound on the magnetic core 2, and a primary current connection sheet 4 having one end disposed outside the housing 1 and the other end passing through an inner ring side of the magnetic core 2 and extending to the outside of the housing 1, and further includes a signal conditioning circuit disposed in the housing 1, the signal conditioning circuit includes an induction circuit, a differential amplification circuit 14, and a power amplification circuit 15 connected in sequence, a hall chip 6 of the induction circuit is fixed in an air gap 5 formed on the magnetic core 2, an output end of the power amplification circuit 15 and one end of the secondary coil 3 are connected to the other end of the secondary coil 3 in series with a first sampling resistor Rm1 and then connected to the ground, a connection point of the first sampling resistor Rm1 and the ground is a negative signal output end M1-, the connection point of the first sampling resistor Rm1 and the secondary coil 3 is a signal positive output end M1+, the signal conditioning circuit further comprises a constant voltage source circuit 16, and the output end of the constant voltage source circuit 16 is connected with the hall chip 6. The current I2 output by the power amplifying circuit 15 generates a compensation magnetic field through the feedback circuit, and the compensation magnetic field cancels the magnetic field generated by the primary current I1, so that the magnetic field in the magnetic core 2 is zero, and the current transformer works in a zero magnetic flux mode.
The signal conditioning circuit further comprises a protection circuit 17 connected to the input terminal of the constant voltage source circuit 16, as shown in fig. 7, the protection circuit 17 comprises a first transient diode TVS1 and a second transient diode TVS2 connected in reverse series between the positive input terminal V + and the negative input terminal V-of the constant voltage source circuit 16, and the connection point of the first transient diode TVS1 and the second transient diode TVS2 is connected to ground. The protection circuit 17 is designed for electromagnetic compatibility (EMC), has strong electromagnetic compatibility (EMC), and mainly realizes the capability of resisting external strong electromagnetic interference (EMS), the principle lies in that a circuit which mainly comprises a TVS device and has the capability of resisting external strong electromagnetic interference is designed at an external connection part, the TVS is a high-efficiency protection device in a diode form, and when two poles of the TVS are impacted by reverse transient high energy, the TVS can be 10-12At the speed of second order, the high impedance between two poles is changed into low impedance, the surge power up to thousands of watts is absorbed, the voltage between two poles is clamped at a preset value, the precision components in the electronic circuit are effectively protected, the damage of various surge pulses is avoided, and therefore the external strong electromagnetic interference is effectively isolated.
The constant voltage source circuit 16 provides working voltage + V-V for the Hall chip 6, and meanwhile, the constant voltage source circuit 16 also generates adaptive compensation voltage to compensate the zero potential of the Hall chip 6. As shown in fig. 4, the positive power supply V + and the negative power supply V-of the transmission amplifier U1 respectively pass through the transmission amplifier U1 to generate + V and-V, and are connected to the hall chip 6 to provide stable operating voltage.
The induction circuit comprises an eighth resistor R8 and a tenth resistor 10 which are connected in series between a positive output end + V and a negative output end-V of the constant voltage source circuit 16, and the connection point of the eighth resistor R8 and the tenth resistor 10 is simultaneously connected with the Hall chip 6 and the differential amplification circuit 14. As shown in fig. 5, the sensing circuit is formed by connecting the hall chip 6 in parallel with an eighth resistor R8 and a tenth resistor R10, the eighth resistor R8 is an adjustable resistor, and the eighth resistor R8 and the tenth resistor R10 perform unequal voltage compensation on the hall chip 6.
As shown IN fig. 6, the differential amplifier circuit 14 is a three-operational-amplifier precision differential amplifier composed of a differential amplifier U2 and its surrounding devices, the differential amplifier circuit 14 includes a third resistor R3 connected between the hall chip 6 and the third pin, i.e. 1IN + end, of the differential amplifier U2, a twelfth resistor R12 connected between the hall chip 6 and the fifth pin, i.e. 2IN + end, of the differential amplifier U2, a fourth resistor R4, a sixth resistor R6, a seventh resistor R7, a ninth resistor R9, a fourteenth resistor R14, and a thirteenth resistor R13 sequentially connected between the thirteenth pin, i.e. 4 IN-end, of the differential amplifier U2 and the ground, a connection point of the fourth resistor R4 and the sixth resistor R6 is connected to the first pin, i.e. 1OUT end, of the differential amplifier U2, a connection point of the sixth resistor R6 and the seventh resistor R7 is connected to the second pin, i.e. 1 IN-end, of the differential amplifier U2, the connection point of the seventh resistor R7 and the ninth resistor R9 is connected to the sixth pin, i.e., the 2 IN-terminal, of the differential amplifier U2, the connection point of the ninth resistor R9 and the fourteenth resistor R14 is connected to the seventh pin, i.e., the 2 OUT-terminal, of the differential amplifier U2, the connection point of the fourteenth resistor R14 and the thirteenth resistor R13 is connected to the twelfth pin, i.e., the 4IN + terminal, of the differential amplifier U2, the fifth resistor R5 is connected between the thirteenth pin, i.e., the 4 IN-terminal, of the differential amplifier U2 and the fourteenth pin, i.e., the 4 OUT-terminal, of the differential amplifier U2, and the fourteenth pin, i.e., the 4 OUT-terminal, of the differential. The three-operational-amplifier precise differential amplifier regulates and amplifies the tiny voltage generated by the Hall chip 6, thereby eliminating the equidirectional voltage error and simultaneously providing the precise amplification of a weak signal.
As shown in fig. 8, the power amplifier circuit 15 includes a first transistor Q1, a second transistor Q2, a first diode D1, a second diode D2, and an eleventh resistor R11 connected in series between the base of the first transistor Q1 and the collector of the second transistor Q2, a connection point of the first diode D1 and the second diode D2 is connected to the differential amplifier circuit 14, a connection point of the second diode D2 and the eleventh resistor R11 is connected to the base of the second transistor Q2, a second resistor R2 is connected between the collector and the base of the first transistor Q1, an emitter of the first transistor Q1 is connected to an emitter of the second transistor Q2, and a connection point of the emitter and the emitter of the second transistor Q2 is connected to the input end of the secondary coil 3. The power amplifying circuit comprises a complementary power amplifying circuit for eliminating cross-over distortion OCL and completes power amplification of voltage signals output by the differential amplifying circuit, the first triode Q1 is of a PNP type, and the second triode Q2 is of an NPN type.
As a further improvement of the invention, the current transformer further comprises a signal conditioning board 7, the signal conditioning circuits are all arranged on the signal conditioning board 7, the Hall chip 6 is fixedly connected with the signal conditioning board 7, a clamping groove 8 for inserting the signal conditioning board 7 is arranged in the shell 1, and the signal conditioning board 7 is inserted into the clamping groove 8. The dismouting is convenient and fast more, labour saving and time saving, and the security is higher moreover.
As a further improvement of the present invention, the middle portion of one side plate of the housing 1 protrudes outward to form a square groove 9 inside, the square groove 9 is located outside the signal conditioning plate 7, a socket pin 10 for connecting a signal conditioning circuit on the signal conditioning plate 7 with the outside is arranged in the square groove 9, the socket pin 10 includes a power lead-in socket pair and a signal output socket pair, the lower ends of two pins of the power lead-in socket pair are respectively connected with a positive input terminal V + and a negative input terminal V-of the constant voltage source circuit 16, the lower ends of two pins of the signal output socket pair are respectively connected with a signal output terminal M1+ and a signal output terminal M1-, and the upper ends of the pins of the power lead-in socket pair and the signal output socket pair protrude outside the housing 1. Convenient and fast disassembly, time and labor saving and good safety.
As a further improvement of the invention, a circular groove 11 is arranged on a bottom plate of the shell 1, the lower end of the magnetic core 2 with the secondary coil 3 is inserted into the circular groove 11, a chip positioning notch 12 is arranged at a position on the bottom plate corresponding to the air gap 5 of the magnetic core 2, the Hall chip 6 is inserted into the chip positioning notch 12, a connecting sheet accommodating groove 13 is also arranged on the bottom plate, and the primary current connecting sheet 4 is clamped with the connecting sheet accommodating groove 13. As shown in fig. 1 and 2, the circular groove 11 is a groove surrounded by two circular arc-shaped plates, a gap is left between the two circular arc-shaped plates, and the circular groove 11, the chip positioning notch 12 and the connecting sheet accommodating groove 13 can play a role in positioning, so that the mounting is simpler and more convenient.
As a further improvement of the invention, three magnetic cores 2 are arranged in each shell 1, correspondingly, the number of the primary current connecting sheet 4, the Hall chip 6 and the signal conditioning circuit is three, the three signal conditioning circuits are arranged on the same signal conditioning plate 7, and the current transformer adopts a structural mode that three phases share one shell 1, so that the complex design of a single current transformer shell is omitted, and the difficulty and the cost of the production process are reduced.
As a further improvement of the present invention, a magnetic shield layer is provided on the inner wall of the housing 1. The magnetic shielding layer is made of a ferromagnetic material with high magnetic conductivity, and can effectively shield an external magnetic field, so that the capacity of the current transformer for resisting the interference of the external magnetic field is improved.
The shell 1 is a plastic shell, three magnetic cores 2 are arranged in the shell 1, as shown in fig. 1, the three magnetic cores 2 are sequentially arranged from left to right, each magnetic core 2 is wound with a secondary coil 3, each magnetic core 2 is provided with an air gap 5, and correspondingly, the number of the primary current connecting sheet 4, the number of the Hall chips 6, the number of the signal conditioning circuits, the number of the circular grooves 11, the number of the chip positioning gaps 12 and the number of the connecting sheet accommodating grooves 13 are all three. The socket pins 10 include one power lead-in pin pair at the leftmost side and three signal output pin pairs located at the right side of the power lead-in pin pair, the three signal output pin pairs corresponding to the secondary coils 3 on the three magnetic cores 2 one to one. Every magnetic core 2 is placed in a circular slot 11 and is fixed with the insulating cement, every primary current connection piece 4 joint is in order to guarantee that it just passes the central point that corresponds magnetic core 2in order to guarantee in the connection piece holding tank 13 that corresponds, and it is fixed by the filling of insulating cement between primary current connection piece 4 and the secondary coil 3 that corresponds, and the magnetism shielding layer is pasted on shell 1 inner wall with the sticky tape form. As shown in fig. 2, the inner walls of the left and right ends of the housing 1 are fixed with positioning plates, a cavity between the two positioning plates and the side wall of the housing 1 forms a slot 8, and the signal conditioning plate 3 is inserted into the slot 8 and fixed by insulating glue. The three Hall chips 6 are welded and fixed with the signal conditioning plate 7.
The invention can also be used for measuring two-phase current, and the middle magnetic core 2 and the corresponding part are removed, and other construction modes are not changed.
The invention is based on the closed loop hall current sensing technology, as shown in fig. 3, the working principle of the closed loop hall current sensing is described below by taking single-phase current measurement as an example, the working principle of the closed loop hall current sensing is magnetic balance, a primary side primary current Ip1 flows through a primary winding, namely a primary current connecting sheet 4, the generated magnetic flux acts on a hall chip 6 positioned in an air gap 5 of a magnetic core 2 with high magnetic permeability, the hall chip 6 outputs a hall voltage under a certain excitation current Ic, the output secondary current I2 after the hall voltage is amplified by a differential amplifying circuit 14 and a power amplifying circuit 15 generates a magnetic field which is offset with the primary current Ip1 through a feedback circuit, and the magnetic field in the magnetic core 2 is zero at this time. Therefore, the hall chip 6 achieves the purpose of reflecting the magnitude of the primary current Ip 1in proportion to the secondary current I2 (Ip1 × 1 is I2 × N2, and 1 and N2 are the number of turns of the primary coil and the number of turns of the secondary coil, respectively) by the action of the zero-flux indicating indication, and the secondary current I2 outputs a secondary sampling voltage corresponding to the current passing through the primary current line, that is, a voltage between the signal output terminal M1+ and the signal output terminal M1-through the high-precision first sampling resistor Rm 1.
The frequency measurement range of the invention is far wider than that of the traditional current transformer, and the principle is that firstly, the magnetic core 2 adopted by the current transformer has higher resistivity, so that the eddy current loss at high frequency can be well reduced; secondly, the magnetic field at the air gap 5 always changes near zero magnetic flux, and the frequency of the change can be fast because the amplitude of the change of the magnetic field is very small, so that the current transformer has fast response speed. In summary, the upper limit working frequency of the closed-loop hall current transformer can reach more than 100 kHz.
The amplitude measurement range of the current transformer is far wider than that of the traditional current transformer, and the principle is that the current transformer works in a zero-magnetic-flux state, so that the magnetic core 2 cannot be saturated before a magnetic field generated by primary current is larger than the maximum magnetic field which can be generated by a secondary compensation winding provided by a power supply, and just for this reason, the nonlinearity and the hysteresis effect of the magnetic core 2 of the current transformer cannot influence the output, and better linearity and higher precision can be obtained.
The invention works in a zero magnetic flux mode, is always in a zero magnetic flux compensation state, is not influenced by the linearity of a magnetic circuit and a Hall chip 6, has small temperature drift error, high response speed of the whole closed loop system and dynamic balance establishment time less than or equal to L mu s, can ensure that the linearity is superior to 0.1 percent, the measurement precision level is within 0.2 percent, has very small measurement error for direct current and even harmonic in an alternating current circuit, has basically unchanged error under the condition that power factors are 1.0 and 0.5L, and has stronger external electromagnetic interference resistance and external magnetic field interference resistance.
The inventive samples 1 and 2 were tested and the data obtained are shown in tables 1 and 2 below, respectively:
table 1 sample 1 test data
Table 2 sample 2 test data
As can be seen from the data in Table 1, when the maximum primary current is 60A, the relative error at 1% measuring point (0.6A) is-0.62%, the relative error at 5% measuring point (3A) is 0.15%, the relative error at 20% measuring point (12A) is-0.02%, the relative error at 100% measuring point (60A) is 0.01%, the relative error at 120% measuring point (72A) is 0.03%, and the linearity is 0.07%, and the total meets the 0.2S% precision level of the current transformer for metering.
As can be seen from the data in Table 2, when the maximum primary current is 60A, the relative error of the 1% measuring point (0.6A) is 0.28%, the relative error of the 5% measuring point (3A) is-0.10%, the relative error of the 20% measuring point (12A) is-0.11%, the relative error of the 100% measuring point (60A) is-0.01%, the relative error of the 120% measuring point (72A) is-0.02%, the linearity is 0.06%, and the total meets the 0.2S% precision level of the current transformer for metering.
Claims (10)
1. The utility model provides a current transformer that possesses wide band, broad width measurement and anti magnetic interference ability, includes shell (1), sets up magnetic core (2) in shell (1), secondary coil (3) of winding on magnetic core (2) and one end are located shell (1) outside and the other end and cross the interior ring side of magnetic core (2) and extend to shell (1) outside primary current connection piece (4), its characterized in that: the current transformer further comprises a signal conditioning circuit arranged in the shell (1), the signal conditioning circuit comprises an induction circuit, a differential amplification circuit (14) and a power amplification circuit (15) which are sequentially connected, a Hall chip (6) of the induction circuit is fixed in an air gap (5) formed in the magnetic core (2), the output end of the power amplification circuit (15) is connected with one end of the secondary coil (3), the other end of the secondary coil (3) is connected with the ground after being connected with a first sampling resistor Rm 1in series, the connection point of the first sampling resistor Rm1 and the ground is a signal negative output end M1-, the connection point of the first sampling resistor Rm1 and the secondary coil (3) is a signal positive output end M1+, the signal conditioning circuit further comprises a constant voltage source circuit (16), and the output end of the constant voltage source circuit (16) is connected with the Hall chip (6).
2. The current transformer of claim 1, wherein the current transformer has wide-band and wide-range measurement and anti-magnetic interference capabilities, and further comprises: the signal conditioning circuit further comprises a protection circuit (17) connected with the input end of the constant voltage source circuit (16), the protection circuit (17) comprises a first transient diode TVS1 and a second transient diode TVS2 which are reversely connected between the positive input end V + and the negative input end V-of the constant voltage source circuit (16) in series, and the connection point of the first transient diode TVS1 and the second transient diode TVS2 is connected with the ground.
3. The current transformer of claim 1, wherein the current transformer has wide-band and wide-range measurement and anti-magnetic interference capabilities, and further comprises: the induction circuit comprises an eighth resistor R8 and a tenth resistor 10 which are connected in series between a positive output end + V and a negative output end-V of the constant voltage source circuit (16), and the connection point of the eighth resistor R8 and the tenth resistor 10 is simultaneously connected with the Hall chip (6) and the differential amplification circuit (14).
4. The current transformer of claim 1, wherein the current transformer has wide-band and wide-range measurement and anti-magnetic interference capabilities, and further comprises: the differential amplification circuit (14) is a three-operational-amplifier precise differential amplifier consisting of a differential amplifier U2 and surrounding devices thereof, the differential amplification circuit (14) comprises a third resistor R3 connected between a Hall chip (6) and a third pin of the differential amplifier U2, a twelfth resistor R12 connected between the Hall chip (6) and a fifth pin of the differential amplifier U2, a fourth resistor R4, a sixth resistor R6, a seventh resistor R7, a ninth resistor R9, a fourteenth resistor R14 and a thirteenth resistor R13 which are sequentially connected between a thirteenth pin of the differential amplifier U2 and the ground, a connecting point of the fourth resistor R4 and the sixth resistor R6 is connected with a first pin of the differential amplifier U2, a connecting point of the sixth resistor R6 and the seventh resistor R7 is connected with a second pin of the differential amplifier U2, and a connecting point of the seventh resistor R7 and the ninth resistor R9 is connected with a sixth pin 2 of the differential amplifier U2, the connection point of the ninth resistor R9 and the fourteenth resistor R14 is connected with the seventh pin of the differential amplifier U2, the connection point of the fourteenth resistor R14 and the thirteenth resistor R13 is connected with the twelfth pin of the differential amplifier U2, a fifth resistor R5 is connected between the thirteenth pin and the fourteenth pin of the differential amplifier U2, and the fourteenth pin of the differential amplifier U2 is connected with the power amplification circuit (15).
5. The current transformer of claim 1, wherein the current transformer has wide-band and wide-range measurement and anti-magnetic interference capabilities, and further comprises: the power amplification circuit (15) comprises a first triode Q1, a second triode Q2, a first diode D1, a second diode D2 and an eleventh resistor R11 which are sequentially connected between the base of the first triode Q1 and the collector of the second triode Q2 in series, the connecting point of the first diode D1 and the second diode D2 is connected with the differential amplification circuit (14), the connecting point of the second diode D2 and the eleventh resistor R11 is connected with the base of the second triode Q2, a second resistor R2 is connected between the collector and the base of the first triode Q1, the emitter of the first triode Q1 is connected with the emitter of the second triode Q2, and the connecting point of the emitter and the emitter is connected with the input end of the secondary coil (3).
6. The current transformer of claim 1, wherein the current transformer has wide-band and wide-range measurement and anti-magnetic interference capabilities, and further comprises: the current transformer further comprises a signal conditioning board (7), the signal conditioning circuit is arranged on the signal conditioning board (7), the Hall chip (6) is fixedly connected with the signal conditioning board (7), a clamping groove (8) for inserting the signal conditioning board (7) is formed in the shell (1), and the signal conditioning board (7) is connected with the clamping groove (8) in an inserting mode.
7. The current transformer of claim 1, wherein the current transformer has wide-band and wide-range measurement and anti-magnetic interference capabilities, and further comprises: the middle of one side plate of the shell (1) protrudes outwards to form a square groove (9) in the inner side, the square groove (9) is located on the outer side of the signal conditioning plate (7), a power strip pin (10) for connecting a signal conditioning circuit on the signal conditioning plate (7) with the outside is arranged in the square groove (9), the power strip pin (10) comprises a power lead-in plug pair and a signal output plug pair, the lower ends of the two pins of the power lead-in plug pair are respectively connected with a positive input end V + and a negative input end V-of the constant voltage source circuit (16), the lower ends of the two pins of the signal output plug pair are respectively connected with a signal output end M1+ and a signal output end M1-, and the upper ends of the pins of the power lead-in plug pair and the signal output plug pair are protruded outside the shell (1).
8. The current transformer of claim 1, wherein the current transformer has wide-band and wide-range measurement and anti-magnetic interference capabilities, and further comprises: be provided with circular slot (11) on the bottom plate of shell (1), the lower extreme and circular slot (11) grafting of magnetic core (2) that have secondary coil (3), chip location breach (12) have been seted up with the position corresponding with air gap (5) of magnetic core (2) on the bottom plate, hall chip (6) are pegged graft with chip location breach (12), connection piece holding tank (13) have still been seted up on the bottom plate, primary current connection piece (4) and connection piece holding tank (13) joint.
9. The current transformer of claim 1, wherein the current transformer has wide-band and wide-range measurement and anti-magnetic interference capabilities, and further comprises: three magnetic cores (2) are arranged in each shell (1), and correspondingly, the number of the primary current connecting sheet (4), the number of the Hall chips (6) and the number of the signal conditioning circuits are all three.
10. The current transformer of claim 1, wherein the current transformer has wide-band and wide-range measurement and anti-magnetic interference capabilities, and further comprises: the inner wall of the shell (1) is provided with a magnetic shielding layer.
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| CN201911109810.XA CN110658374A (en) | 2019-11-14 | 2019-11-14 | Current transformer with wide frequency, wide measurement and anti-magnetic interference capability |
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| CN112730949A (en) * | 2020-12-21 | 2021-04-30 | 唐新颖 | High anti-interference Hall sensor |
| CN112730963A (en) * | 2020-12-22 | 2021-04-30 | 唐新颖 | Automobile-level Hall current sensor with temperature compensation and compensation method thereof |
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