CN216310100U

CN216310100U - Closed-loop current sensor with magnetic shunt structure

Info

Publication number: CN216310100U
Application number: CN202120885392.XU
Authority: CN
Inventors: 白茹; 蓝天; 窦爱玉; 钱正洪; 王杰; 李俊
Original assignee: Hangzhou Dianzi University
Current assignee: Hangzhou Dianzi University
Priority date: 2021-04-27
Filing date: 2021-04-27
Publication date: 2022-04-15
Anticipated expiration: 2031-04-27

Abstract

The utility model discloses a closed loop type current sensor with a magnetic shunt structure, wherein the magnetic shunt structure formed by an air gap of a magnetic ring and the magnetic ring has the effect of shunting and attenuating a signal magnetic field generated by current to be detected, the magnetic sensor is arranged at the central position of a connecting line of the air gap and the center of the magnetic ring and can sense and detect the signal magnetic field component after shunting and attenuating, an instrument amplifier and a power amplifier are used for processing a signal generated by the magnetic sensor, amplifying and driving a feedback coil to generate a magnetic field with the direction opposite to that of an original signal magnetic field and the size similar to that of the original signal magnetic field, a current signal in the feedback coil detects the feedback current by sampling the voltage at two ends of a resistor, and inputs the voltage signal into an MCU (microprogrammed control unit) for ADC (analog to digital converter) conversion; the working range of the magnetic sensor is increased, the current working range detectable by the current sensor is improved, the working range and the linearity of the current sensor are improved, and the obtained current sensor is high in sensitivity, wide in working range, good in linearity and high in bandwidth.

Description

Closed-loop current sensor with magnetic shunt structure

Technical Field

The utility model belongs to the technical field of magnetic sensor application, and relates to a closed-loop current sensor based on a magnetic shunt structure.

Background

The current sensor is a detection device which can sense the information of the measured current and convert the information into an electric signal meeting certain standard requirements or information in other required forms according to a certain rule for output so as to meet the requirements of information transmission, processing, storage, display, recording, control and the like. The current sensor is generally applied to actual measurement and protection systems of current, such as the fields of photovoltaic, wind power, metallurgy, electric power, smart power grids, railway locomotives, power supplies, aerospace, military industry, internet of things and the like.

Current sensors can be classified into open-loop current sensors and closed-loop current sensors according to the presence or absence of a feedback circuit. Open-loop current sensors are favored by manufacturers because of their simple structure, high reliability, and high overload capability. The open-loop current sensor is generally constructed from a magnetic core, an excitation wire passing through the magnetic core, a detection element, and a processing circuit. For example, the patent technology with the publication number of CN 210835038U adopts symmetric dual magnetic cores and dual sensors to eliminate interference signals, so that the anti-interference capability is strong, but the working range is limited by the working range of the sensing chip and is difficult to be improved, and the response time is also affected by magnetic hysteresis and external magnetic field, so the bandwidth is low, the response is slow, and the precision is low; the utility model has the granted publication number of CN 112147401A and is named as an invention patent of a current detection circuit based on a Hall current sensor, similarly, the working range of the utility model is limited by the linear working range of a sensing chip, and the utility model also has the problems of small measuring range, poor linearity and low precision.

The structure of the closed-loop current sensor generally comprises a detection element, a magnetic core or a non-magnetic core, a processing circuit, a feedback coil and the like. For example, in the utility model with the publication number of CN 203259575U, the name of which is closed-loop current sensor, the magnetic sensing detecting element is placed at the air gap of the magnetic ring opening, and is provided with a signal processing circuit and a feedback coil, so as to generate a feedback magnetic field opposite to the magnetic field generated by the primary current, i.e. the magnetic balance method, but because the magnetic field at the air gap is too strong and the small position change has too much influence on the measurement accuracy, the working range is smaller, the linearity is lower and the stability is greatly influenced by the vibration. The authorized bulletin number is CN 210803570U, and the name is a closed-loop current sensor, and the technical means of a current transformer is adopted, so that the detection precision can be improved to a certain extent, but the technical method can only detect alternating current signals and cannot detect direct current signals. The utility model discloses an authorization notice number is CN 207215885U, and the name is a closed loop current sensor's utility model patent, and it has adopted the scheme of no magnetic core, directly feeds back the magnetic field on the sensing chip, and no magnetic core does not have and gathers magnetic effect, and under the fixed circumstances of device, just can't detect the signal in weak and small magnetic field, and the detection precision is difficult to improve.

In summary, the conventional open-loop current sensor has the problems of small measuring range, low linearity, low precision, low bandwidth and the like, and the conventional related technology of the closed-loop current sensor also has the problems of small measuring range, low linearity, low precision or poor stability.

Disclosure of Invention

The utility model aims to provide a closed-loop current sensor with a magnetic shunt structure, which aims to overcome and make up the defects in the prior art and improve the working range, the detection precision, the working bandwidth and the linearity of the current sensor.

The utility model comprises a detachable accurate positioning magnetic ring mounting and fixing support, a magnetic ring with two symmetrical gaps, a magnetic sensor, a signal processing and signal feedback circuit consisting of an instrument amplifier, a power amplifier, a feedback coil, a sampling resistor and an MCU (microprogrammed control Unit), and an upper computer at a PC (personal computer) end, wherein the upper computer can be communicated with the signal processing circuit.

The magnetic ring is a magnetic ring structure consisting of two semicircular magnetic rings and two symmetrical air gaps, the upper half part of the magnetic ring structure is detachable, and the lower half part of the magnetic ring structure is fixed through a magnetic ring bracket, so that a circuit to be measured can be assembled in situ and the current can be measured without damaging or influencing the original circuit structure; the magnetic ring mounting bracket can accurately fix the two semicircular magnetic rings, so that the widths of two air gaps of the magnetic rings are kept fixed, the two air gaps on the magnetic rings are used for shunting and attenuating a signal magnetic field generated by current to be measured, and a smaller magnetic field component is generated by a stray magnetic field generated by a larger original signal magnetic field through the air gaps at the position where the air gaps extend to the centers of the magnetic rings; the magnetic sensor is arranged at the central position of a connecting line between the air gap and the center of the magnetic ring, the sensitive axis direction of the magnetic sensor is vertical to the connecting line between the air gap and the center of the magnetic ring, and the magnetic sensor can sense and detect the signal magnetic field component after shunting and attenuation, so that the magnetic field detection range of the magnetic sensor can be increased, namely the range of signal current which can be detected by the current sensor is increased, and a current signal with a wider range can be detected; the signal processing circuit and the signal feedback circuit are used for amplifying the signal output by the magnetic sensor, converting the signal into a current signal and then driving the feedback coil, the signal feedback coil is wound on the lower half magnetic ring, and a feedback magnetic field generated by the signal feedback coil in the sensitive axis direction of the magnetic sensor is similar to the original signal magnetic field in size and opposite in direction, so that a closed loop structure is formed, and the magnetic field detection range, sensitivity and linearity of the current sensor can be further improved. The upper computer is PC end software which can be communicated with the signal processing circuit, and is used for reading and displaying the current measured value output by the signal processing circuit through the serial port at the PC end and further processing data.

The magnetic sensor is a high-sensitivity magnetic sensor and is composed of a Wheatstone bridge structure consisting of four magnetoresistors, a leakage magnetic field generated by signal current at the center of a connecting line between an air gap of a magnetic ring and the center of the magnetic ring can be detected, the Wheatstone bridge of the magnetic sensor outputs a differential signal, and an instrument amplifier amplifies signal voltage and outputs the signal voltage to a power amplifier.

The power amplifier is an operational amplifier for converting voltage into current signals, and is used for converting voltage signals output by the instrument amplifier into current signals and driving the current to the feedback coil, so that the feedback coil generates a feedback magnetic field which is opposite to and close to a signal magnetic field generated by original signal current in direction of a sensitive axis of the magnetic sensor under the driving of the feedback current, and a closed-loop feedback structure is formed.

The feedback coil is a spiral coil structure wound by a metal wire, and can generate a magnetic field which is similar to the signal current in size and opposite to the signal current in the direction of the sensitive axis of the magnetic sensor under the drive of the feedback current.

The sampling resistor is a high-power resistor, the current signal in the feedback coil is detected by the voltage at two ends of the sampling resistor, the voltage signal is input into the MCU for ADC conversion, and finally the MCU is in serial communication with the PC and finally presented on the PC end upper computer.

Furthermore, the magnetic ring is made of nickel-based, cobalt-based or iron-based soft magnetic materials.

Furthermore, the fixed support comprises a magnetic ring fixed shell, a joggle structure and a magnetic sensor fixed structure, and is made of nonmagnetic substances, preferably resin and plastic.

Furthermore, the magnetic sensor is selected from a giant magnetoresistance sensor, an anisotropic magnetoresistance sensor or a tunnel junction magnetoresistance sensor.

Furthermore, the feedback ring is formed by winding a non-magnetic and high-conductivity copper core enameled wire material.

The utility model combines the magnetic sensor technology, the magnetic shunt technology and the signal feedback technology, adopts the magnetic shunt technology to shunt and attenuate a larger signal magnetic field into a reduced magnetic field, thereby increasing the working range of the system, improving the current working range detectable by the current sensor, and adopts a closed loop structure to balance the original signal magnetic field, thereby further improving the working range and the linearity of the current sensor.

Drawings

FIG. 1 is a schematic view of an overall system of the present invention;

FIG. 2 is a schematic view of a mounting bracket of the present invention;

fig. 3 is a simplified circuit diagram of the system.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

As shown in FIG. 1, a closed-loop current sensor based on a magnetic shunt structure comprises a signal current lead 1-1, a magnetic ring 1-2, a magnetic sensor 1-5, an instrument amplifier 1-6, a power amplifier 1-7, a feedback coil 1-8, a sampling resistor 1-9, an MCU1-10 and an upper computer 1-11;

the magnetic rings 1-2 are made of soft magnetic materials, iron-based amorphous materials with the inner diameter of 40mm and the outer diameter of 60mm are selected in the embodiment, the magnetic rings are integrally annular, and air gaps with the width of 1mm are formed on the left side and the right side (in the figure, the air gaps of the left magnetic ring 1-3 and the air gaps of the right magnetic ring 1-4).

The signal current lead 1-1 is made of copper and vertically penetrates through a plane where the magnetic ring is located inwards, and the copper bar is overlapped with the circle center of the magnetic ring.

The magnetic sensors 1-5 are giant magneto-resistance (GMR) sensors, are positioned on a perpendicular bisector from a lead wire on one side of the lead wire to the inner wall on the side of the magnetic ring, and the sensitive axis direction of the magnetic sensors is downward in the perpendicular direction.

The instrument amplifier 1-6 is a differential input operational amplifier with low noise, high precision and high common mode rejection ratio and is positioned outside the magnetic ring.

The power amplifier 1-7 is an operational amplifier for converting a voltage signal into a current signal, is positioned at the rear stage of the instrumentation amplifier 1-6, and is connected with a following mode for driving the feedback coil 1-8 to generate current.

The feedback coils 1-8 are formed by winding copper enameled wires, are wound on the lower half side of the magnetic ring, are symmetrical about a straight line in the vertical direction of the center of a circle, are positioned at the rear stage of the power amplifier, and convert current signals into magnetic field signals to counteract the magnetic field generated by the signal current wires 1-1 and gathered in the magnetic rings 1-2, so as to achieve the effect of magnetic balance.

The sampling resistor 1-9 is a high-power thick film resistor with the resistance value of 1 ohm, is positioned at the rear stage of the coil, the other end of the sampling resistor is grounded and is grounded with the power amplifier, the current flowing through the resistor is converted into a voltage signal again, and the voltage signal is input to the MCU1-10 part for ADC conversion and output to be displayed and monitored on the upper computer 1-11 at the rear stage.

As shown in fig. 2, the diagram is a fixing bracket of a signal current lead 1-1, a magnetic ring 1-2 and a magnetic sensor 1-5 in the implementation process of fig. 1, and the fixing bracket comprises a signal current lead groove 2-1, a fixing air gap 2-2, a magnetic sensor PCB fixing hole 2-3, an upper half magnetic ring bracket 2-4, an upper half magnetic ring groove 2-5, a tenon 2-6, a mortise 2-7, a lower half magnetic ring bracket 2-8, a lower half magnetic ring groove 2-9 and a lower half magnetic ring support platform 2-10;

the signal current lead groove 2-1 is positioned above the lower half magnetic ring bracket, and after the upper half magnetic ring is disassembled, the lead to be tested can be clamped into the groove so as to fix the signal current lead.

The upper half magnetic ring support 2-4 is a support of an upper half magnetic ring and comprises an upper half magnetic ring groove 2-5 and two tenons 2-6. In the embodiment, the upper half magnetic ring groove 2-5 is of a concave structure, and the half-ring-shaped magnetic ring is accurately fixed in the groove, so that the effect of firmly combining the magnetic ring and the bracket is achieved. The tenon 2-6 is a convex structure and is used for being butted with the mortise 2-7 to achieve the tenon joint fixing effect.

The lower half magnetic ring support 2-8 is a support of a lower half magnetic ring and comprises two mortises 2-7, a lower half magnetic ring groove 2-9 and a lower half magnetic ring support platform 2-10 which are respectively arranged opposite to the two tenons 2-6.

In the embodiment, the lower half magnetic ring grooves 2-9 are of a concave structure, the two sides of the middle of the lower half magnetic ring grooves are slightly wider and are used for winding the feedback coil, and the magnetic ring after winding can be accurately fixed in the grooves so as to achieve the effect of firmly combining the magnetic ring and the support. The mortises 2-7 are of a concave structure and are used for being butted with the tenons 2-6 to achieve the tenon joint fixing effect.

The left side and the right side of the joggled joint of the upper half magnetic ring support 2-4 and the lower half magnetic ring support 2-8 are symmetrically provided with fixed air gaps 2-2, the fixed air gaps can separate two half magnetic rings 1-2 in the upper magnetic ring groove and the lower magnetic ring groove, and two air gaps with equal fixed intervals can be formed on the left side and the right side so as to achieve the effect of forming a magnetic shunt structure after the joggled joint.

The magnetic sensor PCB fixing holes 2-3 are used for fixing the printed circuit board on which the magnetic sensors 1-5 are positioned on the magnetic ring support so as to ensure that the relative positions of the magnetic sensors and the magnetic ring are not changed.

The lower half magnetic ring support tables 2-10 are used for supporting the whole fixed support and can be flatly placed on the flat operation table surface.

As shown in fig. 3, a simplified circuit diagram of a principle of the implementation of fig. 1 is shown, including a magnetic sensor, an instrumentation amplifier U1, a power amplifier U2, a feedback Coil and a sampling resistor R.

In this embodiment, an active magnetic sensor GMR SAS030-1 is used, and thus power is supplied at 5V. The wheatstone bridge structure composed of R1, R2, R3 and R4 on the left side is an expansion of the internal structure of the magnetic sensor, and signals between R1 and R3 and between R2 and R4 are output as differential signals to the subsequent instrumentation amplifier.

The instrumentation amplifier U1 uses INA849 of Texas instruments, and can amplify signals 1000 times in a frequency band range with better performance, and the slew rate of 35V/mus can ensure that the signals are not distorted.

The power amplifier U2 was selected from the traversal instrument OPA548 to produce a maximum current signal of 3A, sufficient for the coil to produce a magnetic field signal that cancels the current in the signal current conductor.

The utility model is implemented by clamping the upper half magnetic ring into the upper half magnetic ring groove, winding the feedback coil on the lower half magnetic ring and clamping the lower half magnetic ring into the lower half magnetic ring groove, fixing the printed circuit board with the magnetic sensor on the lower half magnetic ring bracket, clamping the signal current lead into the signal current lead groove, joggling and fixing the upper and lower magnetic ring brackets, introducing current into the signal current lead in a direction vertical to the plane, generating a clockwise magnetic field in the space, collecting most of the magnetic field inside the magnetic ring by the magnetic ring, generating a small leakage magnetic field at the air gap, the direction of the leakage magnetic field being parallel to the sensitive axis of the magnetic sensor, generating a forward differential voltage signal to the instrument amplifier by detecting the change of the magnetic field, amplifying the signal by the instrument amplifier through adjusting Rg resistance, converting the voltage signal into a current signal by the power amplifier in front stage, the current generates a magnetic field in the feedback coil in the counterclockwise direction, the feedback magnetic field is continuously increased along with the increase of the current in the feedback coil, the magnetic field is close to and offsets the original magnetic field at the moment, the current in the final feedback coil can be stabilized at a smaller value at last, the process is very fast, within milliseconds or even microseconds, the current signal can be converted into a voltage signal by the rear-stage sampling resistor at the moment, and the magnitude of the current to be measured can be judged according to the voltage value on the resistor after calibration. Meanwhile, a voltage signal on the sampling resistor also flows into the MCU, is converted into a digital signal through the ADC, and is output to an upper computer at the PC end through a serial port of the MCU for displaying, so that the purpose of monitoring and displaying the size of the current to be detected in real time by the upper computer is achieved.

Specifically, the peripheral circuit of the instrumentation amplifier U1 comprises two power supplies, an Rg resistor, and two filter capacitors of C1 and C2. The power is used for supplying power for U1, and the maximum output voltage after the voltage value has decided the instrument amplifier and has enlargied, and Rg resistance is used for adjusting the magnification, can carry out 1 to the multiple regulation of infinity according to the formula that the manual provided in theory, and C1 and C2 are filter capacitor, filter the ripple of power.

Specifically, the peripheral circuit of the power amplifier U2 includes two power supplies and two sets of filter capacitors C3 and C4, and the capacitors C3 and C4 can use or use 0.1uF, 10uF, 1000uF, etc. at the same time to filter the ripple and noise of the large-current power supply, thereby ensuring that the output signal is a current signal converted from a pure preceding-stage voltage signal. The operational amplifier connects the inverting input end with the output end, and becomes an operational amplifier in a following mode according to the virtual short-circuit characteristic of the operational amplifier, and the input voltage and the output voltage reach the same magnitude.

The technology of the utility model combines the magnetic sensor technology, the magnetic shunt technology and the signal feedback technology, and adopts the magnetic shunt technology to shunt and attenuate a larger signal magnetic field into a reduced magnetic field, thereby increasing the working range of the system, improving the current working range detectable by the current sensor, and adopting a closed loop structure to balance the original signal magnetic field, and further improving the working range and the linearity of the current sensor.

It will be evident to those skilled in the art that the utility model is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the utility model being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.

The same or similar reference numerals in the drawings of the present embodiment correspond to the same or similar components; in the description of the present invention, it should be understood that if there is an orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "vertical", "horizontal", etc., based on the orientation or positional relationship shown in the drawings, it is only for convenience of description and simplification of description, but it is not indicated or implied that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and therefore, the terms describing the positional relationship in the drawings are only for illustrative purposes and are not to be construed as limitations of the present patent, and specific meanings of the terms may be understood by those skilled in the art according to specific situations.

Claims

1. The closed-loop current sensor with the magnetic shunt structure comprises a magnetic ring mounting and fixing support, a magnetic ring with two symmetrical gaps, a magnetic sensor, a signal processing and signal feedback circuit and a PC (personal computer) end upper computer capable of communicating with the signal processing circuit;

the method is characterized in that: the magnetic ring is a magnetic ring structure consisting of two semicircular magnetic rings and two symmetrical air gaps, the upper half part of the magnetic ring structure is detachable, and the lower half part of the magnetic ring structure is fixed through a magnetic ring bracket; the magnetic ring mounting bracket accurately fixes the two semicircular magnetic rings; the magnetic sensor is arranged at the central position of a connecting line of the air gap and the center of the magnetic ring, and the sensitive axis direction of the magnetic sensor is vertical to the connecting line of the air gap and the center of the magnetic ring; the signal processing and signal feedback circuit comprises an instrument amplifier, a power amplifier, a feedback coil, a sampling resistor and an MCU; the feedback coil is wound on the lower half magnetic ring, and a feedback magnetic field generated by the feedback coil in the sensitive axis direction of the magnetic sensor is similar to the original signal magnetic field in size and opposite in direction, so that a closed loop structure is formed; the signal output by the magnetic sensor is amplified by the instrument amplifier and the power amplifier and then converted into a current signal to drive the feedback coil; the upper computer is respectively and electrically connected with the output end of the signal processing circuit and the PC end, and reads and displays the current measured value output by the signal processing circuit through the serial port at the PC end.

2. The closed-loop current sensor of magnetic shunt structure of claim 1, wherein: the magnetic sensor is composed of a Wheatstone bridge structure consisting of four magnetoresistors.

3. The closed-loop current sensor of magnetic shunt structure of claim 1, wherein: the power amplifier is an operational amplifier for converting voltage into current signals.

4. The closed-loop current sensor of magnetic shunt structure of claim 1, wherein: the feedback coil is a spiral coil structure wound by a metal wire.

5. The closed-loop current sensor of magnetic shunt structure of claim 1, wherein: the sampling resistor is a high-power resistor.

6. The closed-loop current sensor of magnetic shunt structure of claim 1, wherein: the magnetic ring material is made of nickel series, cobalt series or iron series soft magnetic material.

7. The closed-loop current sensor of magnetic shunt structure of claim 1, wherein: the magnetic ring mounting and fixing support comprises a magnetic ring fixing shell, a joggle structure and a magnetic sensor fixing structure, and is made of nonmagnetic substances.

8. The closed-loop current sensor of magnetic shunt structure of claim 1, wherein: the magnetic sensor is selected from a giant magnetoresistance sensor, an anisotropic magnetoresistance sensor or a tunnel junction magnetoresistance sensor.

9. The closed-loop current sensor of magnetic shunt structure of claim 1, wherein: the feedback coil is formed by winding a non-magnetic high-conductivity copper core enameled wire material.