A high-precision wide-range open-type current clamp based on three-iron-core comparison method principle

Abstract

The application discloses a high-precision open type current testing device with a measuring range of 2000 amperes, and relates to the technical field of electrical measurement, which aims to meet the urgent demand for the high-precision and large-current open type current testing device in the current measurement and testing field. The device adopts the principle of three-iron-core comparison method, and realizes the high-precision measurement of the large current in the open state through three annular magnetic cores made of high magnetic permeability material, cooperating filters, detection windings and other internal devices. The device is composed of a current measuring device and a display device, and the current measuring device and the display device are connected by a communication interface. The current measuring device is composed of a fixed part and an adjustable device, and the opening and closing of the measuring ring port are realized through the control of the button. The core component in the measuring ring port is an annular magnetic core, which is meshed through close connection and limits the generation of leakage current. The display device can transmit the result of the current measuring device to the display touch screen through the communication device, and the range and function can be selected through direct touch.

Description

Technical Field

[0001] This invention relates to the field of electrical measurement technology, specifically to a 2000A high-precision open-type current testing device with a current accuracy of up to 0.05. Background Technology

[0002] An ammeter is an instrument used to measure the magnitude of current in an operating electrical circuit. When measuring current, the common method is to disconnect the circuit under test and then connect the primary side of the ammeter or current transformer in series with the circuit. Integrated current measuring devices such as current transformers are usually called closed-type current testing devices. However, when using open-type current testing devices, current can be measured without disconnecting the circuit, as it does not need to be connected in series. This greatly improves the convenience of current measurement and has wide applications in fields such as current monitoring.

[0003] Open-type current testing equipment used to consist of a combination of a current transformer and an ammeter. The iron core of the current transformer can be opened when the wrench is squeezed; the wire through which the measured current passes can pass through the open gap of the iron core without being cut, and the iron core closes when the wrench is released.

[0004] Open-type current testing equipment is used as a general testing device, but its accuracy is low. Due to the limitations of traditional design principles, the accuracy of clamp-on ammeters used to be generally below 5%. High-current precision measurement often relies on closed-type current testing equipment, such as current sensors, and open-type current testing equipment cannot be used. However, with the development of science and technology and the continuous updating of metrology technology, many fields have new requirements for open-circuit measurements of high current. For example, in the field of hydrogen energy production, the measurement of upstream power requires high accuracy. However, due to the system design, the current loop cannot be disconnected in many cases, making it impossible to connect closed-circuit test equipment into the circuit. Only open-circuit test equipment can be used for measurement, making it impossible to accurately monitor the upstream power of hydrogen energy. Another example is in the traceability field of open-circuit ammeters. In order to transmit measurements to traditional open-circuit current test equipment, such as clamp meters, the accuracy of the equipment itself needs to be at least 0.5 class. If the test coil needs to transmit measurements, the accuracy of the test equipment must be at least 0.1 class. However, the test coil is an integrated device, and traditional high-precision closed-circuit test equipment cannot be connected. This has led to persistent problems with the traceability of clamp coils at the national level, and has also resulted in significant issues with the national calibration standards for clamp meters regarding measurement transmission. Therefore, a wide-range, high-accuracy open-circuit current measuring device is in high demand in various fields, hence the design of a 2000A high-precision open-circuit clamp meter. Summary of the Invention

[0005] The purpose of this invention is to design an open-type current testing device structure, enabling it to measure up to 2000A with an accuracy of 0.05%.

[0006] To achieve the above objectives, this invention employs the principle of the three-core comparison method.

[0007] As attached Figure 1 As shown in the description, three toroidal cores C1, C2, and C3 are made of high permeability material, and four windings W1, W2, W3, and W4 are made of enameled wire. S The measuring head of the DCCT is composed of three magnetic cores, C1, C2, and C3, which have identical physical characteristics and geometric dimensions; and four windings, W1, W2, W3, and W... S The number of turns are N1, N2, N3 and N, respectively. S Winding W1 is wound around magnetic core C1 and connected to comparator U1 and excitation current sampling resistor R. S1 Threshold voltage setting resistors R1 and R2, and low-pass filter L PF A self-excited oscillating flux gate is constructed as a DC zero flux detector.

[0008] Winding W2 is wound around magnetic core C2 and, together with unity-gain inverter U2 and excitation current sampling resistor RS2, forms an excitation flux compensation circuit. This circuit is used to suppress the alternating excitation flux in magnetic core C1 due to the transformer effect in the primary winding W. P and secondary winding W S Modulation ripple induced in the middle.

[0009] The winding W3 is wound around the magnetic core C3 to form the detection winding of the active AC current transformer, which serves as an AC zero flux detector and is also used to expand the bandwidth and reduce modulation ripple.

[0010] secondary winding W S The magnetic cores C1, C2, and C3 are wound back-to-back and stacked together, through which the secondary compensation current I flows. S Used to cancel the measured current I on the primary side P The generated magnetic field thus achieves zero magnetic flux.

[0011] Magnetizing current sampling resistor R S2 voltage signal v on sn2 After passing through high-pass filter H PF Then, with the excitation current sampling resistor R S1 voltage signal v on sn1 The sums are obtained by the summing circuit Sum1, and the output signal v is... sn12 As a low-pass filter L PF The input signal. Figure 1 H PF Mainly used to suppress L PFConducted modulation ripple caused by a finite time constant.

[0012] The output signal v of the DC zero flux detector dc The DC error signal of the DCCT is used as the output signal v of the AC zero flux detector. ac As the AC error signal of the DCCT. The DC error signal vdc and the AC error signal v ac The sums are obtained by the summing circuit Sum2, and the output signal v is... e This serves as the system error signal for the DCCT. This error signal controls the proportional-integral converter P. I Drive power amplifier P A Output secondary compensation current I S Used to cancel the measured current I on the primary side P The generated magnetic field forms a closed loop to achieve zero magnetic flux.

[0013] Because the DCCT introduces deep negative feedback, the primary side is measured by a large current I. P It is precisely converted into a small secondary current I according to a certain ratio. S And small current I S It is then easy to pass through a precision four-terminal resistor R M The signal is converted into a voltage signal and then measured using a high-order digital multimeter (DMM). Since the conversion ratio is known, the measured small secondary current value can be easily calculated to obtain the measured large primary current value, thus enabling precise measurement of large DC currents.

[0014] In actual design, as shown in the appendix Figure 2 As shown, this device consists of a current measuring device and a display device, both of which are integrated. The current measuring device comprises a fixed part 1 and an adjustable part 2. The end of the current measuring device has a communication interface 3 for connecting to the communication interface 4 of the display device. The movable part 5 of the adjustable part 2 is controlled by a button 6; pressing and releasing the button controls the opening and closing of the movable part 5. When closed, the measuring coil 7 can perform high-precision current measurement using the three-core comparison method. The measuring part 8 in the measuring coil 7 is a toroidal magnetic core made of high permeability material, arranged as shown in the attached figure. Figure 3 As shown, the toroidal magnetic cores 12 are all closely arranged to ensure that the measuring ring 7 can actively engage after closing, thereby minimizing leakage current. The measuring ring 7 also has a built-in self-locking device, which can only be opened by pressing button 5 after closing, further ensuring the tightness of the closure.

[0015] The display device mainly consists of a housing 9, a display screen 10, a switch 11, and a communication interface 4. It is connected to the communication interface 3 of the current measuring device through the communication interface 4. The display screen 10 is a touch screen that displays the measured value of the current measuring device on the display screen. The corresponding measurement function and range can be selected by touching the screen with a finger. Attached Figure Description The present invention will be further described below with reference to the accompanying drawings: Figure 1 This is the schematic diagram of a current clamp circuit. Figure 2 This is a schematic diagram of a current clamp structure; Figure 3 This is a schematic diagram of the magnetic core arrangement structure of the current clamp jaws.

Claims

1. A high-precision open-type current testing device with a measurement range of up to 2000 amperes, characterized in that: Using the three-core comparison method, the three toroidal cores are made of a high-permeability material.

2. The high-precision open-type current testing device with a measurement range of up to 2000 amperes as described in claim 1, characterized in that, The three toroidal magnetic cores have identical physical properties and geometric dimensions, and the toroidal magnetic cores 12 are closely arranged to ensure that they can actively engage after the measuring ring 7 is closed, so as to minimize leakage current.

3. The high-precision open-type current testing device with a measurement range of up to 2000 amperes as described in claim 1, characterized in that, Controlled by button 6, the opening and closing of movable part 5 can be controlled by pressing and releasing the button. After closing, the measuring ring 7 can perform high-precision current measurement through the three-core comparison method.

4. A high-precision open-type current testing device with a measurement range of up to 2000 amperes as described in claim 1, characterized in that, It consists of a current measuring device and a display device. The display device is connected to the current measuring device via the communication interface 3 through the communication interface 4.

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