CN1243248C - Current sensor - Google Patents

Abstract

The present invention discloses a current sensor, which is characterized in that after feedback windings in two symmetrical channels are connected in series, one end of the feedback windings is connected with the ground, and the other ends of the feedback windings are connected with one end of a sampling resistor correspondingly. After the output of two Hall elements symmetrically arranged is magnified by an operational amplifier and is processed by the following steps of wave filtering, the transformation of voltage and current and current amplifying treatment, the output terminals of the Hall elements are connected with the other end of the sampling resistor, and voltage detecting signals at both of the two ends of the electric resistor are sent to a computer. The present invention also comprises a Rogowski coil whose both ends are connected with the sampling resistor in parallel. After voltage detecting signals of the sampling resistor are magnified by the operational amplifier and are processed by wave filtering and integral magnifying, the voltage detecting signals are sent to the computer. After each group of data is processed by the computer, the value of the measured current is sent to a display to be displayed. The present invention obviously improves the saturation characteristic and the linearity of the sensor, and the accuracy is superior to 0.5 %. The present invention has the advantages of good ability of magnetic disturbance resistance, simple structure, and convenient installation, debugging and maintenance. In addition, the additional error of temperature is less than 0.1 %/10 DEG.

Description

a current sensor

Technical field:

The invention relates to a current sensor, which is especially suitable for current feedback, cut-off control, steady current regulation, and transient large current signal detection in DC side overcurrent and short circuit protection in power electronic equipment.

Background technique:

Accurate detection and control in frequency conversion speed control devices, inverter devices, UPS power supplies, inverter welding machines, substations, electrolytic plating, CNC machine tools, microcomputer monitoring systems, power grid monitoring systems and in various fields that require isolation and detection of large non-sinusoidal currents The non-sinusoidal large current is the fundamental guarantee for the safe and reliable operation of the equipment and the first problem to be solved.

Now, large current measuring devices such as current comparators, current transformers, and shunts have been developed; some measuring devices based on physical effects such as magneto-optical effects and nuclear magnetic resonance have also appeared. These devices can be roughly divided into two categories in terms of their working principles: the measuring device that determines the magnitude of the measured DC large current according to the voltage drop of the measured current on the known resistance, such as a shunt; the magnetic field established by the measured current A measuring device to determine the magnitude of the measured current, such as a Rogowski coil direct measuring device.

The biggest problem with using a shunt is that there is no isolation between the input and the output, and when using a shunt to measure high-frequency or large currents, it is inevitably inductive. Therefore, after connecting the shunt, it will affect the measured current waveform. Non-sinusoidal signals cannot be transmitted realistically.

For the transformer-type current transformers widely used at present, they are transformers based on the principle of electromagnetic induction, which have the advantages of high dielectric strength, reliable operation, and low price. However, when the transient current or di/dt is very large, the magnetic circuit is prone to saturation, and the secondary current cannot reflect the measured current without distortion; the frequency range it can adapt to is very narrow, especially it cannot transmit DC; and, due to the mutual inductance The non-ideality of the transformer causes large errors in the transformation ratio and phase, which need to be compensated by hardware or software, which increases the complexity of the system; in addition, there is an exciting current when the current transformer is working, so it is Inductive components have the same disadvantages as shunts when measuring high frequency or large currents. Later, a current transformer with an air gap was developed on this basis. Since this transformer opened a section of air gap in the magnetic circuit, its reluctance increased, remanence decreased, and the equivalent magnetization curve was linearized, making the magnetic The circuit will not be saturated when the transient current or di/dt is large, so the secondary side can basically respond to the transient current without distortion, but its structure size is relatively large.

For the current comparator with iron core, the performance is stable, the power consumption is small (compared with the shunt), it can bear a large load, and the circuit under test can not be disconnected during installation. However, due to the use of iron core materials, it does not have ideal magnetization characteristics, is easy to saturate, and has limitations on the magnitude of the measured high current, and its shielding structure is complex, and its size is large. Generally, it is used as a laboratory calibration device for high current.

The magnetic balance Hall current sensor is a new generation of industrial current sensor developed based on the Hall effect to measure and control current. Its essence is a current-magnetic-voltage converter, and its function is the same as that of a traditional current transformer. Its There is good electrical isolation between input and output, and the insulation withstand voltage exceeds 3kV. It uses the Hall element to measure the magnetic induction intensity of the measured current in the air gap of the iron core (surrounding the measured current-carrying conductor) to determine the magnitude of the measured current. Its characteristics are: simple structure, can not disconnect the circuit under test during installation; and has many advantages such as high precision, good linearity, wide frequency band, fast response, strong overload capacity and no energy loss of the circuit under test. However, the values of the input resistance and output resistance of the Hall element are not constant, so it has a magnetoresistance effect, which increases continuously with the magnetic induction. Apart from the Hall potential in a single Hall element, there are several other residual potentials in the output voltage. The Hall coefficient, input resistance, output resistance and residual potential of the Hall element are all related to temperature, so the Hall element has a large temperature error.

Rogowski coil, its magnetic circuit does not contain iron core, is a special structure of air-core coil, also known as air-core transformer. Because its magnetic circuit does not contain an iron core, there is no saturation problem, good transient performance, wide frequency range, little influence by the external magnetic field and the position of the measured current-carrying conductor, there is no power and thermal stability problem, and it has good performance. Electromagnetic shielding characteristics, good insulation with high-voltage circuit, simple structure, easy processing, etc., with the external integration circuit, it can accurately measure the transient large current such as pulse of core saturation caused by too large amplitude or too high di/dt current, lightning current. It is currently widely used as a simple and effective sensor for measuring large transient currents or high di/dt currents in air-insulated switches and relay protection. However, because the magnetic circuit of the Rogowski coil does not contain an iron core, when the measured transient current or di/dt is not large, the induction signal is too weak and the measurement error is relatively large.

With the wide application of power electronic technology in the fields of frequency conversion speed control device, inverter device, UPS power supply, inverter welding machine, substation, electrolytic plating, numerical control machine tool, microcomputer monitoring system, power grid monitoring system, etc., for high frequency, high The transmission and detection of di/dt and wide-spectrum (including DC components) current waveforms are particularly important. For the transient current in power electronic equipment is not large, but di/dt is high, if conventional devices such as shunts, comparators, current transformers, Rogowski coils and Hall elements are used as current detection devices alone, it is not enough to measure Require.

Contents of the invention

The object of the present invention is to provide a current sensor to overcome the disadvantages of the above-mentioned prior art. It is a current sensor with dual detection mode composed of Hall element and Rogowski coil. It significantly improves the saturation characteristics and linearity of the sensor. It is more sensitive to current and can accurately measure high di/dt transient large current.

In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a current sensor, including an annular iron core and a Hall element, an air gap is evenly and symmetrically opened on the above-mentioned annular iron core, and the feedback winding phases in the two channels are symmetrical. In series, one end of the series connection is grounded, and the other end is connected to one end of the corresponding sampling resistor; in the air gap above, two Hall elements placed symmetrically form a group, and each Hall element is controlled by a constant current source, and two in each group The output terminals of the Hall element are respectively connected to the positive and negative input terminals of the operational amplifier, and after being amplified by the operational amplifier, filtering, voltage-current conversion, and current amplification processing are performed, and the output terminal after current amplification processing is connected to the other end of the above-mentioned sampling resistor , the detection voltage signal at both ends of the sampling resistor is sent to the computer; it also includes a Rogowski coil, and the corresponding sampling resistor is connected in parallel at both ends of the coil, and the two ends of the sampling resistor are respectively connected to the positive and negative input terminals of the operational amplifier, and the positive input The terminal is grounded, and the detection voltage signal of the sampling resistor is amplified by the operational amplifier, and then filtered and integrated and amplified, and the signal after the integral and amplified processing is sent to the computer; the computer processes the above-mentioned detection voltage signal and the signal after the integral and amplified processing. After that, the measured current is sent to the display for display.

Outside the insulation layer and protective layer of the above-mentioned feedback winding and Rogowski coil, a ground wire layer is specially set to replace the above-mentioned ground wire, and an insulation layer and a protective layer, an electromagnetic shielding layer, and an outermost insulation layer are arranged in sequence outside the ground wire layer. layer and protective layer.

The advantages of the present invention are:

1. Because the Hall element is symmetrically placed in the air gap, when the interference magnetic field from the same direction enters the Hall element, the magnetic flux density will generate opposite Hall interference potential on the two symmetrically distributed Hall elements. and cancels itself in the circuit.

2. The sensor uses the non-inductance and fast response characteristics of the Hall sensor to measure the current in the power electronic circuit whose amplitude is not too large or not too high di/dt, that is, the measurement will not be caused by the amplitude being too large or too high di/dt dt causes magnetic saturation of the core. Since the original di/dt value is changed due to the access of the sensor, it is especially suitable for current feedback, cut-off control, steady current regulation and DC side overcurrent detection in power electronic equipment.

3. The sensor utilizes the Rogowski coil's non-saturation problem, wide frequency bandwidth, and fast response characteristics to measure the non-sinusoidal transient current in the power electronic circuit caused by the saturation of the iron core due to too large amplitude or too high di/dt, that is, it is especially suitable for Detection of current signals used in current feedback, cut-off control and short-circuit protection in power electronic equipment.

4. The sensor adopts a constant current source circuit with strong load capacity of voltage-current conversion. In order to stabilize the output current, in addition to introducing deep negative feedback in each link, the output current is also sampled and fed back to the adder through the voltage follower. , forming a large external feedback, which further enhances the stability of the output current, so that the output current of the constant current source has high stability within a large range of load changes.

In short, the saturation characteristics and linearity of the sensor are obviously improved; the accuracy is better than 0.5%, the power consumption is small, the temperature additional error is less than 0.1%/10°C, and the anti-magnetic interference ability is strong; the structure is simple, the weight is light, the price is low, and installation, Calibration, debugging and maintenance are very convenient.

Description of drawings

Fig. 1(a) is a schematic structural diagram of an embodiment of the present invention.

Fig. 1(b) is a schematic diagram of the positions of two skeleton cores according to an embodiment of the present invention.

Fig. 2 is a circuit diagram of the symmetrical arrangement of the Hall elements H ₁ and H ₂ and the Rogowski coil in Fig. 1(a).

FIG. 3( a ) is a circuit diagram of a constant current source of the Hall element H ₁ in FIG. 1( a ).

Fig. 3(b) is a circuit diagram of a constant current source of the Hall element _H2 in Fig. 1(a).

Fig. 4(a) is a schematic structural view of the circular cross-section skeleton core F ₁ in Fig. 1(a).

Fig. 4(b) is a schematic structural view of the rectangular cross-section skeleton core F ₂ in Fig. 1(a).

Detailed ways

As shown in Figure 1(a), 1 is a display, 2 is a computer that processes the detection voltage signals from two groups of parallel channels; 3 is processing the filtering, voltage-current conversion, and Current amplification circuit; 4 is the filtering and integral amplification circuit for processing the induced voltage from the Rogowski coil detection element, and its output voltage is U _S2 ; 5 is the measured current bus; 6 is the dedicated ground layer; F ₁ and F ₂ are two A ₁ and A ₂ are operational amplifiers; R _S1 and R _S2 are the sampling resistors of the two detection channels; I _F1 and I _F2 are the currents flowing in the two detection channels; U _S1 is the terminal of the sampling resistor RX Voltage; U _R1 and U _R2 are the terminal voltage of the sampling resistor _RS2 , H ₁ and H ₂ are two Hall elements; U _H1 and U _H2 are the Hall voltage output by the two Hall elements; W ₁ and W ₂ is the two feedback windings of the channel; W ₃ is the Rogowski coil.

A current sensor is composed of two frame cores (Frame) _F1 and _F2 , the frame core _F1 is composed of an iron core, and the frame core _F2 is composed of an epoxy resin rod. An air gap is set in the diameter direction of the iron core _F1 , the length of the iron core of each channel is equal, the air gap is evenly and symmetrically distributed, and the Hall element is placed in the air gap. On the outer insulating material of the iron core, the feedback winding coil is evenly and densely wound with multiple turns to form a helical shape. The feedback winding coil can also be wound in a Rogowski coil manner. When winding the feedback winding, attention must be paid to the winding direction of the coil to ensure that the sensor realizes the principle of zero magnetic flux detection. The two feedback windings W ₁ and W ₂ are connected in series, and one end of the series connection is connected to one end of the sampling resistor R _S1 , and the other end is grounded. Since the opening is larger, the core is less likely to be saturated. But when the opening is too large, the magnetic field in the air gap will disperse, so that the iron core loses the function of the magnetic gathering ring, and if the opening of the iron core is too large, it will be detrimental to the accuracy of the transformer. Therefore, the length of the air gap can be less than 10 to 15 times the square root of the cross-sectional area of the iron core, taking into account the size of the measured current and the size of the iron core, otherwise it will affect the measurement accuracy of the sensor; in order to enhance the sensing signal of the sensor, without changing the other dimensions of the sensor Next, the axial thickness of the skeleton core _F1 can be increased as much as possible, and the length of the air gap can also be increased accordingly. In addition, the number of air gaps may be an even number greater than or equal to 2 and not exceeding 10. Because the more openings, the longer the length of the air gap, the less saturated the iron core will be. However, considering that more openings will reduce the accuracy of the transformer, on the other hand, it will increase the manufacturing cost and reduce the mechanical strength of the iron core. Therefore, the number of openings in the core should be as small as possible. The Hall elements H ₁ and H ₂ are symmetrically arranged, and both are controlled by a constant current source. The output terminals of the two Hall elements H ₂ and H ₁ are respectively connected to the positive and negative input terminals of the operational amplifier A ₁ , and then sent to Circuit 3 performs filtering, voltage-current conversion, and current amplification processing. The output terminal of the circuit is connected to the other end of the sampling resistor _RS1 , and then each is sent to the feedback winding to generate a reverse magnetic field that is balanced with the magnetic field generated by the measured current to achieve Zero-flux measurement principle. The voltage across the sampling resistor R _S1 is sent to the computer 2 . The above-mentioned circuit 3 is a common filtering, voltage-current conversion, and current amplification circuit.

On the outer insulating material of the skeleton core _F2 , a Rogowski coil is evenly and densely wound in a single turn to form a spiral shape, and the rewinding wire is drawn from the center of the skeleton core _F2 , and the sampling resistor R _S2 is connected in parallel at both ends of the coil, and the two ends of the sampling resistor R _S2 Terminals are respectively connected to the positive and negative input terminals of the operational amplifier _A2 , and the positive input terminal is grounded, and its output is sent to the computer 2 through the filter and integral amplifier circuit 4. Select operational amplifier A ₂ must consider its slew rate, rising speed, drift and precision, generally choose high-speed low-drift precision operational amplifier. Circuit 4 is a common filtering and integral amplifier circuit.

The above-mentioned two groups of different data are processed by the computer 2, and the measured current is sent to the display 1 for display after processing.

It is easy to see that if the number of air gaps of the skeleton core _F1 is 10, and two Hall elements symmetrically arranged as one group, there are five groups in total. At this time, five groups of data are input into the computer 2, and then Adding one set output from the Rogowski coil, the computer 2 will process six sets of different data, and after processing, the measured current will be sent to the display 1 for display.

As shown in Figure 1(b), for the convenience of installation, the two skeleton cores _F1 and _F2 should be selected to have the same size, and 20 is the return slot of the skeleton core _F2 . In order to illustrate the positional relationship of the two skeleton cores, Figure 1(b) exaggerates the distance d between them. After the electromagnetic shielding layer and the outermost insulating layer and protective layer, they are tightly fixed together to form a whole.

As shown in Figure 2, I ₊ and I _- are positive and negative power supplies that supply current to two symmetrically placed Hall elements H ₁ and H ₂ respectively; R _F1 and R _F2 represent constant current sources I ₊ and I _- Feedback resistance; terminals a ₁ and c ₁ indicate the DC control current input and output terminals of Hall element H ₁ , terminals b ₁ and d ₁ indicate the Hall voltage output end of Hall element H ₁ , terminals a ₂ and c ₂ indicate The DC control current input and output terminals of the Hall element H ₂ , the b ₂ and d ₂ terminals represent the Hall voltage output terminals of the Hall element H ₂ ; A ₁ represents the operational amplifier; R _K represents the magnification control of the operational amplifier A ₁ Resistor; 5 is the measured current bus; * indicates the end of the same name of the three windings W ₁ , W ₂ and W ₃ . The connection method of this circuit is that the _d1 end of the Hall element _H1 and the b2 end of the Hall element _H2 are respectively connected to the negative input end and the positive input end of the operational amplifier _A1 , and the _a1 end of the Hall element _H1 Connect with the constant current source (the current supplied to H ₁ is I ₊ ) feedback resistor R _F1 , the other end c ₁ is grounded, and the c ₂ terminal of Hall element H ₂ is connected to the constant current source (the current supplied to H ₂ is I _- ) The feedback resistor R _F2 is connected, the other end a2 is grounded, and the _b1 end of the Hall element _H1 is connected to the _d2 end of the Hall element HX. After the feedback windings W ₁ and W ₂ are connected in series, one end is connected to the sampling resistor R _S1 , and the other end is grounded. Both ends of the sampling resistor R _S1 are connected to the computer 2 . The above-mentioned resistor R _K can be a high-precision resistor, and the operational amplifier _A1 can be an instrumental operational amplifier such as INA128 or a circuit structure of an instrumental operational amplifier composed of precision operational amplifiers such as OP07 and OP27. Since _b1 of Hall element _H1 is connected to _d2 of Hall element _H2 , _c1 is connected to _a2 and grounded, when the disturbing magnetic field from the same direction enters the Hall element, the magnetic field will be in two Symmetrically distributed Hall elements H ₁ and H ₂ generate opposite Hall interference potentials, which cancel themselves out in the circuit. When the DC control current input terminal a ₁ , c ₁ (or a ₂ , c ₂ ) of the Hall element H ₁ , H ₂ flows through the DC current from the constant current source, when there is a magnetic field on its vertical surface and the magnetic field lines pass through it, its Hall voltage output terminal b ₁ , d ₁ (or b ₂ , d ₂ ) terminals will generate Hall voltage, operational amplifier A ₁ can amplify the Hall potential difference, that is, U _H ＝ U _H1 -U _H2 , and its magnification is determined by the control resistor _RK is controlled, that is, the amplification factor is approximately 1+50kΩ/ _RK , and then sent to the processing circuit 3 for processing.

As shown in Figure 3(a), the specific connection method is that the positive input terminal of the operational amplifier _A3 is connected to the reference source _Uref1 through the resistor _R2 , and the positive input terminal is grounded through the resistor _R3 , and the negative input terminal of the operational amplifier _A3 The input terminal is connected to its output terminal through resistor _R4 , and the negative input terminal is connected to the output terminal _of operational amplifier _A5 through resistor _R1 , and the output terminal of operational amplifier _A3 is connected to the negative input terminal of operational amplifier _A4 through resistor R5 terminal, the negative input terminal of the operational amplifier _A4 is connected to the emitter of the power amplifier tube T2 through the resistor _R6 , the positive input terminal is connected to the emitter of the power amplifier tube _T1 through the resistor _R7 , and grounded, and the output terminal is connected to the emitter of the power amplifier tube _T1 through the resistor R6. R ₈ is connected to the base of the power amplifier tube T ₁ . The collector of the power amplifier tube _T1 is connected to the base of the power amplifier tube _T2 , and connected to the collector of the power amplifier tube _T2 and the +15V power supply through the resistor _R9 . The output terminal of the operational amplifier _A5 is connected to its negative input terminal through the resistor _R10 , and its positive input terminal is connected to the emitter of the power amplifier tube _T2 through the resistor R _F1 . The DC control current input terminal _a1 of the Hall element _H1 is connected to the positive input terminal of the operational amplifier _A5 , and the DC control current output terminal _C1 is grounded.

The working principle of Fig. 3(a) is briefly described as follows: the reference source U _ref1 passes through the adder A ₃ and the feedback amplifier A ₄ , and the current amplification drive circuit (T ₁ , T ₂ ) outputs a high and stable current. Because the operational amplifier A ₅ constitutes a follower circuit, and its input impedance is very high (≥10 ¹² Ω), all the current flowing through the feedback resistor R _F1 flows to the Hall element H ₁ . In order to stabilize the output current, in addition to introducing deep negative feedback in each link, the output current sampling is fed back to the operational amplifier A ₃ through the voltage follower A ₅ to form a large feedback, which further enhances the stability of the output current and makes the constant current The source has high stability in the output current within a wide range of load changes.

As shown in Figure 3(b), the specific connection method is that the positive input terminal of the operational amplifier _A6 is connected to the reference source _Uref2 through the resistor _R12 , and the positive input terminal is grounded through the resistor _R13 , and the negative input terminal of the operational amplifier _A6 The input terminal is connected to its output terminal through resistor _R14 , and the negative input terminal is connected to the output terminal of operational amplifier _A8 through resistor _R11 , and the output terminal of operational amplifier _A6 is connected to the negative input terminal of operational amplifier _A7 through resistor _R15 terminal, the negative input terminal of the operational amplifier _A7 is connected to the emitter of the power amplifier tube T4 through the resistor _R16 , the positive input terminal is connected to the emitter of the power amplifier tube _T3 through the resistor _R17 , and grounded, and the output terminal is connected to the emitter of the power amplifier tube _T4 through the resistor R17. R ₁₈ is connected to the base of the power amplifier tube T ₃ . The emitter of the power amplifier tube _T3 is connected to the base of the power amplifier tube _T4 , and its collector is connected to the collector of the power amplifier tube _T4 and the -15V power supply through the resistor _R19 . The output terminal of the operational amplifier _A8 is connected to its negative input terminal through the resistor _R20 , and its positive input terminal is connected to the emitter of the power amplifier tube _T4 through the feedback resistor R _F2 . The DC control current output terminal _c2 of the Hall element _H2 is connected to the positive input terminal of the operational amplifier _A8 , and the DC control current input terminal _a2 is grounded.

The working principle of Fig. 3(b) is briefly described as follows: the reference source U _ref2 passes through the adder A ₆ and the feedback amplifier A7, and the current amplification drive circuit (T3, T4) outputs a high and stable current. Because the operational amplifier A ₈ constitutes a follower circuit, and its input impedance is very high (≥10 ¹² Ω), all the current flowing through the feedback resistor R _F2 flows through the Hall element H ₂ . In order to stabilize the output current, in addition to introducing deep negative feedback in each link, the sampling of the output current is fed back to the operational amplifier A ₆ through the voltage follower A ₈ to form a large feedback, which further enhances the stability of the output current and makes the constant current The source has high stability in the output current within a wide range of load changes.

The constant current source mentioned above, the component selection method is as follows: R ₁ ~ R ₇ , R ₁₁ ~ R ₁₇ use high-precision resistors; R ₈ , R ₉ , R ₁₈ , R ₁₉ use carbon film resistors; feedback resistor R _F1 and R _F select high-precision resistors, and their resistance values are close to the input resistance value R _Hi of the Hall element (i=1, 2), satisfying R _P +R _Hi << R ₁ ; the reference sources U _ref1 and U _ref2 can It is produced by using the REF02P chip produced by PMI Company, which is a +5V precision voltage reference/temperature sensor; A ₃ to A ₈ all use high-precision, low-drift, dynamic zero-calibration CMOS type chopping and zero-stabilizing ICL7650 (or CF7650) Integrated operational amplifier.

As shown in Figure 4(a), the skeleton core _F1 is processed into a ring shape with a circular cross-section. Of course, it can also be processed into a ring shape with a rectangular cross-section. The skeleton core _F1 can be composed of silicon steel sheets or permalloy laminates. Outside the insulating layer and protective layer 7 of the skeleton core _F1 , the feedback winding 8 that is formed into a spiral shape is evenly and densely wound with multiple turns, and then the insulating layer and the protective layer 9 are wound outside the winding 8. Besides, the ground of the sensor is specially set The wire layer 6 is provided with an insulating layer and a protective layer 10 , an electromagnetic shielding layer 11 , and an outermost insulating layer and a protective layer 12 in sequence outside the ground wire layer 6 . This structural form improves the anti-electromagnetic interference capability of the sensor.

As shown in Figure 4(b), the skeleton core _F2 is processed into a ring shape with a rectangular cross-section. Of course, it can also be processed into a ring shape with a circular cross-section. The skeleton core _F2 can be selected from soft rubber bands (or epoxy resin rods) . Since the Rogowski coil needs to be wound back for one turn and drawn out from the center of the skeleton core F ₂ , a return slot 20 needs to be opened outward at the center of the skeleton core of the Rogowski coil. The Rogowski coil 14 is tightly wound outside the insulating layer and the protective layer 13 of the skeleton core _F2 , and the insulating layer and the protective layer 15 are wound outside the coil 14, and the ground wire layer 16 of the sensor is specially arranged outside the coil 14. An insulating layer and a protective layer 17 , an electromagnetic shielding layer 18 , and an outermost insulating layer and a protective layer 19 are arranged in sequence outside the wire layer 16 .

Claims (3)

1. A current sensor comprising a ring-shaped iron core and a Hall element, characterized in that: An air gap is evenly and symmetrically opened on the above-mentioned annular iron core, and the feedback windings in the two symmetrical channels are connected in series, one end of the series connection is grounded, and the other end is connected to one end of the corresponding sampling resistor; In the above air gap, two Hall elements placed symmetrically form a group, each Hall element is controlled by a constant current source, and the output terminals of the two Hall elements in each group are connected to the positive and negative input terminals of the operational amplifier respectively. After being amplified by the operational amplifier, filtering, voltage-current conversion, and current amplification processing are performed, the output terminal after the current amplification processing is connected to the other end of the above-mentioned sampling resistor, and the detection voltage signal U _S1 at both ends of the sampling resistor is sent to the computer; It also includes a Rogowski coil, the two ends of the coil are connected in parallel with the corresponding sampling resistor, the two ends of the sampling resistor are respectively connected to the positive and negative input terminals of the operational amplifier, and the positive input terminal is grounded, and the detection voltage signal of the sampling resistor is amplified by the operational amplifier After that, filter, integral amplification processing is carried out again, and the signal U _S2 after integral amplification processing is sent to computer; The computer processes the detection voltage signal U _S1 and the integrated and amplified signal U _S2 , and sends the measured current to the display for display after processing. 2. The current sensor according to claim 1, characterized in that: outside the insulating layer and protective layer of the feedback winding and the Rogowski coil, a ground wire layer is specially set to replace the above ground wire, and outside the ground wire layer An insulating layer and a protective layer, an electromagnetic shielding layer, and an outermost insulating layer and a protective layer are provided. 3. The current sensor according to claim 1 or 2, characterized in that: the two constant current source circuits connected to the two Hall elements in each of the above-mentioned groups are that the positive input terminal of the operational amplifier _A3 passes through the resistor R ₂ is connected to the reference source U _ref1 , and the positive input terminal is grounded through the resistor R ₃ , the negative input terminal of the operational amplifier A ₃ is connected to its output terminal through the resistor R ₄ , and the negative input terminal is connected to the operational amplifier A ₅ through the resistor R ₁ The output terminal of the operational amplifier _A3 is connected to the negative input terminal of the operational amplifier _A4 through the resistor _R5 , and the negative input terminal of the operational amplifier _A4 is connected to the emitter of the power amplifier tube _T2 through the resistor _R6 . The input terminal is connected to the emitter of the power amplifier tube _T1 through the resistor _R7 , and grounded, the output terminal is connected to the base of the power amplifier tube _T1 through the resistor _R8 , and the collector of the power amplifier tube _T1 is connected to the power amplifier tube T ₂ base, and connected to the collector of the power amplifier tube _T2 and the +15V power supply through the resistor _R9 , the output terminal of the operational amplifier _A5 is connected to its negative input terminal through the resistor _R10 , and its positive input terminal is connected to the resistor R _F1 Connected to the emitter of the power amplifier tube _T2 , the DC control current input terminal _a1 of the Hall element _H1 is connected to the positive input terminal of the operational amplifier _A5 , and the DC control current output terminal _c1 is grounded; The positive input terminal of the operational amplifier _A6 is connected to the reference source _Uref2 through the resistor _R12 , and the positive input terminal is grounded through the resistor _R13 , the negative input terminal of the operational amplifier _A6 is connected to its output terminal through the resistor _R14 , and the negative input terminal The terminal is connected to the output terminal of the operational amplifier _A8 through the resistor _R11 , the output terminal of the operational amplifier _A6 is connected to the negative input terminal of the operational amplifier _A7 through the resistor _R15 , and the negative input terminal of the operational amplifier _A7 is connected to the negative input terminal of the operational amplifier A7 through the resistor _R16 . To the emitter of the power amplifier tube _T4 , the positive input terminal is connected to the emitter of the power amplifier tube _T3 through the resistor _R17 , and grounded, and the output terminal is connected to the base of the power amplifier tube _T3 through the resistor _R18 , and the power amplifier The emitter of tube _T3 is connected to the base of power amplifier tube _T4 , its collector is connected to _the collector of power amplifier tube _T4 and -15V power supply through resistor _R19 , and the output terminal of operational amplifier _A8 is connected to Its negative input terminal and its positive input terminal are connected to the emitter of the power amplifier tube _T4 through the feedback resistor R _F2 , and the DC control current output terminal _c2 of the Hall element _H2 is connected to the positive input terminal of the operational amplifier _A8 . The DC control current input terminal a ₂ is grounded.

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