CN2689240Y - Double detecting current sensors - Google Patents

Abstract

The utility model discloses a double-detection type current sensor, in which an air gap is evenly and symmetrically opened on the annular iron core, and after the feedback windings in the two symmetrical channels are connected in series, one end is grounded, and the other end is connected to one end of the corresponding sampling resistor; the symmetrical After the output of the arranged two Hall elements is amplified by the op amp, it performs filtering, voltage-current conversion, and current amplification processing. The output is connected to the other end of the above-mentioned sampling resistor, and the voltage signal at both ends of the resistor is sent to the computer; The connected Rogowski coil, the two ends of the coil are connected to the sampling resistor, the voltage signal of the resistor is amplified by the operational amplifier, filtered, integrated and amplified, and then sent to the computer; the computer processes the above-mentioned sets of data, and then sends the measured current to the computer. to the display. The utility model can overcome the deficiency caused by the saturation of the iron core of the sensor; the precision is better than 0.5%, the power consumption is small, the temperature additional error is less than 0.1%/10°C, the anti-magnetic interference ability is strong; the structure is simple.

Description

Dual Sensing Current Sensor

technical field

The utility model relates to a current sensor, which is suitable for detecting direct current and alternating current including the following aspects: the transient current signal used in current feedback, cut-off control, steady current regulation and DC side overcurrent and short circuit protection in power electronic equipment detection.

Background technique

Accurately detect and control non-sinusoidal current in DC transmission system, frequency conversion speed control device, UPS power supply, inverter welding machine, electrolytic plating, numerical control machine tool, microcomputer monitoring system, power grid monitoring system and various fields that need to isolate and detect non-sinusoidal current , is the fundamental guarantee for the safe and reliable operation of the equipment and the first problem to be solved.

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, no dynamic and thermal stability problems, and good performance. Excellent 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 current of iron core saturation caused by too large amplitude or too high di/dt, such as Pulse 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. But because the magnetic circuit of the Rogowski coil does not contain an iron core, when the measured current is too small (such as ≤100A) or the di/dt is not large, the voltage signal induced from the Rogowski coil is too weak due to the small mutual inductance coefficient. The error is large. Therefore, measures must be taken to increase the mutual inductance of the Rogowski coil.

Current measuring equipment such as current comparators, current transformers, and shunts have been developed; some measuring equipment based on physical effects such as magneto-optical effects and nuclear magnetic resonance have also appeared.

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 high current, it is inevitably inductive. Therefore, after the shunt is connected, it will not only affect the measured current waveform, but also cannot truly transmit non-sinusoidal signals.

For the transformer-type current transformers widely used at present, it has the advantages of high dielectric strength, reliable operation, and low price. However, when the transient current or di/dt is too 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 high current. 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 limits the size of the measured current. Moreover, its shielding structure is complex and its size is large. It is generally used as a laboratory calibration device for current.

In addition to the above-mentioned current sensors, a magnetic balance Hall current sensor has also appeared. It 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. Its function is the same as that of a traditional current transformer. It has good electrical isolation between its input and output, and its 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 intensity. 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. Therefore, measures must be taken to overcome the influence of unfavorable factors such as the Hall potential of the Hall element, the sensitivity of the Hall element to the position of the measured current-carrying conductor, and temperature errors.

With the wide application of power electronic technology in DC transmission system, 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 and other fields, for It is particularly important to transmit and detect non-sinusoidal current waveforms with wide frequency spectrum (including DC components), small amplitude, and high di/dt. For the transient current whose amplitude is not too large, if a shunt is connected in series in the power electronic circuit, it will inevitably change the electrical parameters of the circuit, which will have an impact on the measured current loop; if a comparator, current transformer, Rogowski Conventional sensing devices such as coils and Hall elements can no longer meet the detection requirements of the above-mentioned special waveform current.

Contents of the invention

The purpose of the utility model is to overcome the shortcomings of the above-mentioned prior art, and provide a dual-detection current sensor. The sensor is composed of a Hall element and a Rogowski coil connected in series, which obviously improves the saturation characteristics, linearity and anti-interference ability of the sensor, is sensitive to small currents, and can accurately measure transient currents where the di/dt is not too large, of course It is also possible to measure large currents or transient currents with relatively high di/dt.

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

Outside the insulating layer and protective layer of the above-mentioned feedback winding and the Rogowski coil connected in series, a ground wire layer is specially set to replace the above-mentioned ground wire, and an insulating layer and a protective layer, an electromagnetic shielding layer, and an outermost Layer insulation and protective layers.

The utility model has the advantages of:

(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 potentials on the two symmetrically distributed Hall elements , and self-cancellation in the circuit, effectively improving the anti-interference performance of the sensor.

(2) Because the Hall element is symmetrically placed in the air gap, the shortcoming that the Hall element is relatively sensitive to the position of the measured current carrier is effectively overcome.

(3) Since the Hall element is placed symmetrically in the air gap, the temperature error of the Hall element can be effectively suppressed.

(4) The sensor utilizes 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, it will not be satisfied because the amplitude is too large or too high di/dt /dt causes the current detection requirement of the magnetic saturation of the iron core), which can avoid changing the original di/dt value due to the access of the sensor, so it is especially suitable for current feedback, cut-off control, and stability in power electronic equipment. Flow regulation and DC side overcurrent detection.

(5) Using Rogowski coils connected in series can effectively improve its sensitivity to the measured small current.

(6) The sensor utilizes Rogowski coils connected in series without an iron core, has no saturation problem, wide frequency band, and fast response characteristics. Since the distributed capacitance of the Rogowski coil connected in series decreases approximately linearly with the increase in the number of series coils, and the series inductance increases linearly with the increase in the number of coils, the theory proves that this has little effect on the frequency response characteristics of the Rogowski coil , but it can obviously improve the mutual inductance coefficient of the Rogowski coil.

(7) The Rogowski coil obtained in series connection can not only measure the non-sinusoidal transient current detection in the power electronic circuit because the amplitude is not too large or the di/dt is not too high, but also can complete the measurement of the current amplitude in the circuit. If the di/dt is too large or too high, it will cause magnetic saturation of the iron core, and the current detection task when the Hall sensor cannot work normally, that is, it can overcome the shortage of iron core saturation, and will not have adverse effects on the power electronic circuit, and will not make the The entire sensor is paralyzed.

(8) The sensor uses Rogowski coils connected in series without an iron core, which can measure large currents or transient currents with a relatively high di/dt, and only need to reduce the number of Rogowski coils in series.

(9) 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, it also samples the output current and adds it through the feedback of the voltage follower. The device forms 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 wide 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 is a schematic structural view of an embodiment of the utility model.

FIG. 2 is a schematic diagram of the positions of the three skeleton cores in FIG. 1 .

FIG. 3 is a circuit diagram of Hall elements H ₁ , H ₂ and Rogowski coils in series arranged symmetrically in FIG. 1 .

FIG. 4( a ) is a circuit diagram of a constant current source of the Hall element H ₁ in FIG. 1 .

FIG. 4( b ) is a circuit diagram of a constant current source of the Hall element H ₂ in FIG. 1 .

FIG. 5 is a schematic structural view of the circular cross-section skeleton core F ₁ in FIG. 1 .

Detailed ways

As shown in Figure 1, 1 is a display, 2 is a computer for processing detection voltage signals from two groups of parallel channels; 3 is processing filtering, voltage-current conversion, current Amplifying circuit; 4 is a filter and integral amplifier circuit for processing the induced voltage from Rogowski coils connected in series; 5 is the measured current bus; 6 is a dedicated ground layer; F ₁ , F ₂ and F ₃ are three skeleton cores; A ₁ and A ₂ are operational amplifiers; R _S1 and R _S2 are the sampling resistors of the two groups of detection channels; I _F1 and I _F2 are the currents flowing in the two groups of detection channels; U _S1 is the terminal voltage of the sampling resistor R _S1 ; U _S2 is the output voltage of the circuit 4; U _R1 and U _R2 are the terminal voltages of the sampling resistor R _S2 , H ₁ and H ₂ are two Hall elements; U _H1 and U _H2 are the Hall voltages output by the two Hall elements Voltage; W ₁ and W ₂ are the two feedback windings of the channel; W ₃₁ and W ₃₂ are the turns of the two series-connected coils Rog1 and Rog2 respectively.

The skeleton core _F1 is an annular iron core. Two air gaps are opened in the diameter direction of the iron core _F1 . The air gaps are evenly and symmetrically distributed. The length of the iron core of each channel is equal. The Hall elements _H1 and _H2 are respectively placed in the in the air gap. On the outer insulating material of the iron core _F1 , the feedback winding is evenly and densely wound. 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. Symmetrically arranged Hall elements H ₁ and H ₂ 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 The circuit 3 performs filtering, voltage-current conversion, and current amplification. The output terminal of the circuit 3 is connected to the other end of the sampling resistor _RS1 , and the voltage at both ends of the sampling resistor _RS1 is sent to the computer 2.

In the present utility model, there are multiple air gaps evenly and symmetrically distributed, and generally the number of air gaps can be selected as an even number greater than or equal to 2 and no more than 10. Because the more openings, the greater the total length of the air gap, the iron core will not be saturated, but considering that more openings will reduce the accuracy of the sensor, 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 _F1 should be as small as possible. Since the opening is larger, the iron core _F1 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 F ₁ loses the function of the magnetic gathering ring, and the opening of the iron core F ₁ is too large, which is not conducive to the accuracy of the sensor. 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 _F1 , taking into account the requirements of the measured current and the size of the iron core, otherwise the measurement accuracy of the sensor will be affected. In order to enhance the sensing signal of the sensor, the axial thickness of the iron core _F1 can be increased as much as possible without changing other dimensions of the sensor, and the length of the air gap can also be increased accordingly.

Skeleton cores F ₂ and F ₃ are non-ferromagnetic materials, Rogowski coils are evenly and densely wound on the outer insulating material of F ₂ and F ₃ , and then the return wire is drawn out from the center of the skeleton cores F ₂ and F ₃ . The structural parameters of the two series-connected coils Rog1 and Rog2 may be the same or different. The two outgoing terminals of the coils Rog1 and Rog2 are connected to the sampling resistor _RS2 , and the two ends of the sampling resistor _RS2 are connected to the positive and negative input terminals of the operational amplifier _A2 respectively, and the positive input terminal is grounded. The output of the operational amplifier _A2 is filtered, The integral amplifier circuit 4 is sent to the computer 2.

Select operational amplifier A ₂ should consider its slew rate, rising speed, drift and precision, generally choose a high-speed low-drift precision operational amplifier, for example, OP27. Circuit 4 is a common filtering and integral amplifier circuit. When selecting the number of Rogowski coils connected in series, it is necessary to consider the magnitude of the measured current or di/dt, that is, the voltage signal induced from the Rogowski coil should not be too weak (otherwise the measurement error will be large), and the series connection of Rogowski coils should also be considered. The dynamic characteristics of the coil must also consider the structural size of the entire sensor.

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.

If the number of air gaps in the skeleton core _F1 is ten, and the number of Rogowski coils connected in series is six, then the two Hall elements symmetrically arranged as one group, there are five groups in total, and five are input into the computer 2. One set of data, plus one set output from six series-connected Rogowski coils, computer 2 will process six sets of different data, and after processing, the magnitude of the measured current will be sent to display 1 for display.

As shown in Figure 2, for the convenience of installation, the three frame cores _F1 , _F2 and _F3 should be selected to have the same size, and 13 is the return line groove of the frame core _F2 (of course, the frame core _F3 also has a return line slot). In _order to illustrate the positional relationship of the three skeleton cores, Figure 2 exaggerates the distances d _{1 and d 2} between them. After the wire layer insulating layer and protective layer, the electromagnetic shielding layer and the outermost insulating layer and protective layer, they can be fixed together to form a whole.

As shown in Figure 3, I ₊ and I _- are positive and negative power supplies, which supply current to two symmetrically placed Hall elements H ₁ and H ₂ respectively; RF ₁ and RF ₂ represent the feedback of constant current sources I ₊ and I _- Resistor; terminals a ₁ and c ₁ indicate the DC control current input and output terminals of the Hall element H ₁ , terminals b ₁ and d ₁ indicate the Hall voltage output end of the Hall element H ₁ , terminals a ₂ and c ₂ indicate the Hall element 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 end of the Hall element H ₂ ; the operational amplifier A ₁ can be selected such as INA128 instrumental operational amplifier or OP07, OP27, etc. The precision operational amplifier constitutes the circuit structure of the operational amplifier for instrumentation; R _K represents the magnification control resistor of the operational amplifier A ₁ , and high-precision resistors can be selected; circuit 3 is the usual filtering, voltage-current conversion, and current amplification circuit; * indicates four The terminal of the same name of the windings W ₁ , W ₂ , W ₃₁ , and W ₃₂ .

Terminal _a1 of the Hall element _H1 is connected to the feedback resistor R _F1 of the constant current source (the current supplied to _H1 is I ₊ ), the other end _c1 is grounded, and the terminal _c2 of the Hall element _H2 is connected to the constant current source ( The current supplied to _H2 is _I- ) the feedback resistor R _F2 is connected, the other end _a2 is grounded, the _b1 end of Hall element _H1 is connected to the _d2 end of Hall element _H2 , and the end of Hall element _H1 Terminal _d1 and terminal _b2 of Hall element _H2 are respectively connected to the negative input terminal and positive input terminal of the operational amplifier _A1 . Since b ₁ and d ₂ of the Hall elements H ₁ and H ₂ are connected, c ₁ and a ₂ are connected 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 , H ₂ generate opposite Hall interference potentials, which cancel themselves out in the circuit. When the DC control current input terminals a ₁ , c ₁ and a ₂ , c ₂ of the Hall elements H ₁ , H ₂ flow through the DC current from the constant current source, when there is a magnetic field on the vertical surface and the magnetic force lines pass through it, its Hall The voltage output terminals b ₁ , d ₁ and b ₂ , d ₂ terminals generate Hall voltage, and the operational amplifier A ₁ can amplify the Hall potential difference, that is, U _H ＝U _H1 -U _H2 , and its magnification is controlled by the control resistor _RK , the magnification factor is approximately 1+50kΩ/ _RK , and then sent to the circuit 3 for processing.

As shown in Figure 4(a), the specific connection method of the constant current source circuit of the Hall element _H1 is that the positive input terminal of the operational amplifier _A3 is connected to the reference source U _ref1 through the resistor _R2 , and the positive input terminal is connected through the resistor R ₃ is grounded, the negative input terminal of operational amplifier A ₃ is connected to its output terminal through resistor R ₄ , and the negative input terminal is connected to the output terminal of operational amplifier A ₅ through resistor R ₁ , and the output terminal of operational amplifier A _{3 is connected to the output terminal of operational amplifier A 3} through resistor R ₅ Received to the negative input of operational amplifier _A4 . 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 _R8 Received to the base of the power amplifier tube _T1 . 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 Figure 4(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 4(b), the specific connection method of the constant current source circuit of the Hall element _H2 is that the positive input terminal of the operational amplifier _A6 is connected to the reference source U _ref2 through the resistor _R12 , and the positive input terminal is connected through the resistor R ₁₃ is grounded, the negative input terminal of operational amplifier _A6 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 output terminal of operational amplifier _A6 through resistor _R15 Received to the negative input of operational amplifier _A7 . 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 _R18 Received to the base of the power amplifier tube _T3 . 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 Figure 4(b) is briefly described as follows: the reference source U _ref2 passes through the adder A ₆ and the feedback amplifier A ₇ , and the current amplification drive circuit (T ₃ , T ₄ ) 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.

For the constant current source mentioned above, the component selection method can be as follows: R ₁ ~ R ₇ , R ₁₁ ~ R ₁₇ use high-precision resistors; R ₈ , R ₉ , R ₁₈ , and R ₁₉ use carbon film resistors; feedback resistors R _F1 and R _F2 use 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 _F +R _Hi << R ₁ ; reference sources U _ref1 and U _ref2 It can be obtained by using the REO2P chip produced by PMI, 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 Fig. 5, 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.

Skeleton cores F ₂ and F ₃ are processed into a ring shape with a rectangular cross-section. Of course, they can also be processed into a ring shape with a circular cross-section. The skeleton cores F ₂ and F ₃ can be selected from soft rubber bands or epoxy resin rods. The Rogowski coil is wound around once when it is wound, and it is drawn out from the center of the return slot of the skeleton core. The Rogowski coil is tightly wound outside the insulating layer and protective layer of the two skeleton cores _F2 and _F3 , and then the insulating layer and protective layer are wound outside the coil, and the ground layer of the sensor is specially set outside the coil. An insulating layer and a protective layer, an electromagnetic shielding layer, and an outermost insulating layer and a protective layer are arranged in sequence outside the wire layer.

Claims (3)

1. A double detection type current sensor, comprising annular iron core, Hall element, is 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 are performed, and its output terminal is connected to the other end of the above-mentioned sampling resistor, and the detection voltage signal at both ends of the sampling resistor is sent to the computer; It also includes Rogowski coils connected in series, and the sampling resistors are connected at the two outgoing ends of the coils, the two ends of the sampling resistors are respectively connected to the positive and negative input terminals of the operational amplifier, the positive input terminals are grounded, and the detection voltage signal of the sampling resistors passes through the After the operational amplifier is amplified, it is filtered, integrated and amplified, and then sent to the computer; The above-mentioned sets of data are processed by the computer, and the measured current is sent to the monitor for display after processing. 2. The current sensor according to claim 1, characterized in that: receiving the constant current source circuit of a Hall element in each of the above-mentioned groups is that the positive input terminal of the operational amplifier _A3 is connected to the reference source through the resistor _R2 U _ref1 , and the positive input terminal is grounded through resistor R ₃ , the negative input terminal of operational amplifier A ₃ is connected to its output terminal through resistor R ₄ , and the negative input terminal is connected to the output terminal of operational amplifier A ₅ through resistor R ₁ , the operation The output terminal of the amplifier _A3 is connected to the negative input terminal of the operational amplifier _A4 through the resistor _R5 , the negative input terminal of the operational amplifier _A4 is connected to the emitter of the power amplifier tube _T2 through the resistor R6, and the positive _input terminal is connected through the resistor R ₇ is connected to the emitter of the power amplifier tube _T1 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 base of the power amplifier tube _T2 . And connect 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 power amplifier tube through the resistor R _F1 The emitter of _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; Another constant current source circuit of the Hall element 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 is connected to the reference source Uref2 through the resistor R13. The resistor _R14 is connected to its output terminal, and the negative input terminal is connected to the output terminal of the operational amplifier _A8 through the resistor _R11 , and the output terminal of the operational amplifier _A6 is connected to _the negative input terminal of the operational amplifier _A7 through the resistor R15. The negative input terminal of the 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 power amplifier tube T4 through the resistor _R18 . To the base of the power amplifier tube _T3 , 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 amplifier A ₈ is connected to its negative input terminal through the resistor R ₂₀ , its positive input terminal is connected to the emitter of the power amplifier tube T ₄ through the feedback resistor R _F2 , and the DC control current output terminal _{c 2} of the Hall element H 2 It is connected with the positive input terminal of the operational amplifier _A8 , and the DC control current input terminal _a2 is grounded. 3. The current sensor according to claim 1 or 2, characterized in that: outside the insulating layer and the protective layer of the Rogowski coil connected in series with the above-mentioned feedback winding, a ground wire layer is specially set to replace the above-mentioned ground wire, in which An insulating layer and a protective layer, an electromagnetic shielding layer, an outermost insulating layer and a protective layer are sequentially arranged outside the ground wire layer.

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