Active magnetic compensated clamp-on current sensor

Abstract

The application relates to an active magnetic compensation clamp current sensor, comprising a first clamp head and a second clamp head; the first clamp head and the second clamp head each comprise a magnetic core and can be combined to form a closed ring body; the clamp current sensor further comprises an excitation circuit, a compensation circuit and a detection circuit; the excitation circuit is used for generating an excitation signal and modulating the excitation signal to a first excitation winding and a second excitation winding; the detection circuit is used for acquiring a current signal on the current detection winding and the excitation winding, integrating to generate an error signal; and the compensation circuit is used for acquiring the error signal and generating a compensation signal applied to a first compensation winding and a second compensation winding. The application provides an active magnetic compensation clamp current sensor, solves the problems that the current clamp current sensor is insufficient in precision and is easily interfered by external temperature and magnetic field, and the like, and compared with the existing clamp current sensor, the active magnetic compensation clamp current sensor can simultaneously measure alternating current and direct current, is not affected by environmental temperature, and has a great improvement in accuracy.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of current measurement, in particular to a clamp current sensor with active magnetic compensation. BACKGROUND

[0002] The existing current measurement tools mainly include a clamp current transformer, a Hall current sensor and a fluxgate current sensor. The Hall current sensor includes an open-loop Hall and a closed-loop Hall.

[0003] The principle of the transformer is that when the measured signal is an alternating current signal, an induced current is generated by electromagnetic induction, and the measured signal is calculated by the induced current. Therefore, it can only measure alternating current signals, and theoretically cannot measure direct current. And due to the limitation of the saturation magnetic field of the magnetic core, the dynamic range of the measurement is small, and the accuracy is also affected by the magnetic permeability and residual magnetism of the magnetic core, so the application range is small.

[0004] The principle of the open-loop Hall is to use the potential difference generated by the Hall effect of the Hall chip under the magnetic field generated by the measured current to detect the potential difference to calculate the measured current. The temperature of the Hall chip itself has a great influence on the whole sensor, and the Hall effect is not obvious when the measured current is small, so the dynamic range of the sensor is small.

[0005] The principle of the closed-loop Hall is to detect the potential difference on the Hall chip to drive the power amplifier to output a compensation current. The magnetic potential generated by the compensation current is equal in size and opposite in direction to the magnetic potential generated by the measured current, which cancels out the magnetic flux in the magnetic core. However, the output signal of the Hall chip is small when the magnetic potential is 0, and the overall noise is large and the temperature drift is serious.

[0006] The fluxgate current sensor uses the even harmonic in the alternating saturation process of the magnetic ring as the characteristic signal. Once the magnetic ring is formed, its relative permeability will hardly change with the external signal. Therefore, as long as the excitation source is stable, the even harmonic will only change with the measured signal. Compared with the Hall chip, the temperature has little effect on the fluxgate principle.

[0007] In related technologies, due to material reasons, the existing fluxgate current sensor can only be made into a complete ring shape and cannot be made into an open-close type clamp shape. SUMMARY

[0008] In order to at least partially overcome the problems in the related art, the present application provides a clamp current sensor with active magnetic compensation.

[0009] According to an embodiment of the present application, a clamp current sensor with active magnetic compensation is provided, comprising: a first jaw and a second jaw; the first jaw and the second jaw each comprise a magnetic core, and the two can be combined to form a closed ring body;

[0010] The magnetic core of the first jaw is wound with a first current detection winding, a first excitation winding and a first compensation winding; the magnetic core of the second jaw is wound with a second current detection winding, a second excitation winding and a second compensation winding;

[0011] The jaw-type current sensor further comprises an excitation circuit, a compensation circuit and a detection circuit; the excitation circuit is configured to generate an excitation signal and modulate the excitation signal to the first excitation winding and the second excitation winding; the detection circuit is configured to acquire current signals on the current detection winding and the excitation winding, and integrate to generate an error signal; the compensation circuit is configured to acquire the error signal and generate a compensation signal applied to the first compensation winding and the second compensation winding.

[0012] Further, the first excitation winding comprises a first decoupling winding and a first magnetic flux detection winding; the second excitation winding comprises a second decoupling winding and a second magnetic flux detection winding.

[0013] Further, the first jaw comprises a magnetic core C1, a magnetic core C2, a magnetic core C3 and a magnetic core C4; a first current detection winding W1, a first decoupling winding W2, a first magnetic flux detection winding W3 and a first compensation winding W4 are wound on the magnetic cores C1-C4 respectively;

[0014] The second jaw comprises a magnetic core C1', a magnetic core C2', a magnetic core C3' and a magnetic core C4'; a second current detection winding W1', a second decoupling winding W2', a second magnetic flux detection winding W3' and a second compensation winding W4' are wound on the magnetic cores C1'-C4' respectively.

[0015] Further, the excitation circuit comprises a waveform generator, a frequency divider and a magnetic modulation power amplifier;

[0016] The waveform generator is configured to generate a waveform signal with a preset frequency and amplitude;

[0017] The frequency divider is configured to perform frequency division processing on the waveform signal generated by the waveform generator;

[0018] The magnetic modulation power amplifier is configured to modulate the waveform signal output by the frequency divider to the windings W2, W2', W3 and W3'.

[0019] Further, the detection circuit comprises a magnetic demodulation unit and an error synthesis unit;

[0020] The magnetic demodulation unit is driven by the waveform signal output by the waveform generator, and demodulates a direct current error signal on the magnetic core;

[0021] The error synthesis unit is configured to acquire the direct current error signal output by the magnetic demodulation unit and the alternating current error signal on the windings W1 and W1', and integrate to generate an error signal.

[0022] Further, the compensation circuit comprises a servo power supply; the servo power supply is used for outputting the error signal after power amplification to the compensation winding W4, W4', so that the error signal on the error synthesizer is continuously reduced to close to zero, forming a closed loop control.

[0023] Further, the compensation circuit further comprises a band elimination filter; the band elimination filter is connected between the error synthesis unit and the servo power supply, and is used for suppressing the conduction modulation ripple caused by the error synthesis unit.

[0024] Further, the clamp current sensor further comprises a mechanical switch and a linkage switch.

[0025] The mechanical switch is pressed down before the clamp current sensor is opened, and the contact in the switch is turned on.

[0026] The linkage switch cooperates with the mechanical switch, and is used for disabling the output of the servo power supply and disabling the output of the magnetic modulation power amplifier when the mechanical switch is turned on.

[0027] Further, the clamp current sensor further comprises an overload protection unit.

[0028] The overload protection unit is used for detecting the direct current error signal output by the magnetic demodulation unit, and outputs a protection signal to the error synthesis unit when the detected direct current signal exceeds the measurement range.

[0029] Further, the clamp current sensor further comprises a measurement resistor R s and an amplitude amplification unit.

[0030] The measurement resistor R s is connected in series with the compensation winding W4, W4', and converts the compensation current into a voltage signal.

[0031] The amplitude amplification unit adjusts the voltage signal on the measurement resistor Rs to a set output range.

[0032] The technical scheme provided by the embodiment has the following beneficial effects:

[0033] The active magnetic compensation clamp current sensor provided by the application solves the problems of insufficient precision and susceptibility to external temperature and magnetic field interference of the current sensor; the application realizes the opening and closing of the magnetic flux gate current sensor, and realizes the magnetic flux gate principle based on active magnetic compensation based on the new circuit principle, and realizes high precision; compared with the existing clamp current sensor, the application can measure alternating current and direct current at the same time, is not affected by the environment temperature, and has a great improvement in accuracy.

[0034] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the application, as claimed. BRIEF DESCRIPTION OF DRAWINGS

[0035] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the application and serve to explain the principles of the application, in which, like reference numerals designate corresponding parts throughout the several views.

[0036] Figure 1 is a schematic diagram of the technical principle of active magnetic compensation.

[0037] Figure 2a is a schematic diagram of the magnetic flux change in the magnetic core of active magnetic compensation.

[0038] Figure 2b is a schematic diagram of the voltage change on the magnetic core of active magnetic compensation.

[0039] Figure 3 is a schematic diagram of the structure of a clamp-type current sensor of active magnetic compensation according to an exemplary embodiment.

[0040] Figure 4 is a partial enlarged view of the middle clamp head part. Figure 3

[0041] Figure 5 is a schematic diagram of the cross section of the clamp head of a clamp-type current sensor of active magnetic compensation according to an exemplary embodiment.

[0042] Figure 6 is a schematic diagram of the circuit of a clamp-type current sensor of active magnetic compensation according to an exemplary embodiment.

[0043] Figure 7 is a circuit block diagram of a magnetic demodulation unit according to an exemplary embodiment.

[0044] Figure 8 is a circuit block diagram of an error synthesis unit according to an exemplary embodiment.

[0045] In the figure: 1 - first clamp head; 2 - second clamp head; 3 - clamp body; 101 - shell; 102 - shell; 201 - shell; 103 - shell limiting block; 104 - anti-static copper foil; 105 - magnetic shielding layer; 106 - anti-vibration insulation layer. DETAILED DESCRIPTION

[0046] ​The exemplary embodiments will be described in detail herein with reference to the attached drawings. In the following description, like reference numerals refer to like elements, unless the context clearly dictates otherwise. The implementations described in the following exemplary embodiments are not meant to represent all implementations consistent with the present application. Rather, they are merely examples that are consistent with some aspects of the present application, as detailed in the appended claims.

[0047] To further describe the technical solutions of the present application, the technical principle of active magnetic compensation is explained in detail.

[0048] As shown in Figure 1 , the principle of active magnetic compensation is that the excitation source I e excites the magnetic core (C) to saturation by a periodic signal with a certain frequency through the excitation winding (W e ); the measured current I P = 0, the magnetic flux in the magnetic core is shown in Figure 2a , which is shown in Figure 2b , B-H, V-t is symmetrical, which is called magnetic balance. If the primary current I P is not 0, the primary current breaks the magnetic balance, and the demodulator detects the magnetic imbalance as a magnetic balance detection mechanism, and drives the servo source to generate a compensation current I S applied to the magnetic core, so that the magnetic core restores the magnetic balance. The number of turns of the primary current is denoted as W P ( Figure 1 The winding inside the sensor is shown in Figure 1 , and W P is the measured current cable, which is not shown in Figure 1 ), the number of turns of the secondary compensation winding is denoted as W S , then W P × I P = W S × I S ; that is, the measured current I P = W S × I S / W P .

[0049] Based on the above technical principle, an active magnetic compensation clamp current sensor is proposed. As shown in Figure 3As shown, the clamp-on current sensor includes a clamp body 3, a first clamp head 1, and a second clamp head 2. The bottom end of the first clamp head 1 is rotatably connected to the clamp body 3 via a pivot, allowing the first clamp head 1 to rotate around the pivot. The bottom end of the second clamp head 2 is fixedly connected to the clamp body 3. Through the rotation of the first clamp head 1, the top ends of the first clamp head 1 and the second clamp head 2 can close and open relative to each other; when their top ends are closed, the first clamp head 1 and the second clamp head 2 form a closed ring. The clamp-on current sensor also includes a mechanical trigger; when the mechanical trigger is pressed, the first clamp head 1 rotates, opening its top end; when the mechanical trigger is released, the first clamp head 1 automatically resets, closing its top end.

[0050] Both the first clamp head 1 and the second clamp head 2 include a magnetic core, and the two can be combined to form a closed ring. The magnetic core of the first clamp head is wound with a first current detection winding, a first excitation winding, and a first compensation winding; the magnetic core of the second clamp head is wound with a second current detection winding, a second excitation winding, and a second compensation winding.

[0051] In some embodiments, the first excitation winding includes a first decoupling winding and a first flux detection winding; the second excitation winding includes a second decoupling winding and a second flux detection winding.

[0052] like Figure 3 As shown, the first clamp head 1 includes magnetic cores C1, C2, C3, and C4; a first current detection winding W1, a first decoupling winding W2, a first flux detection winding W3, and a first compensation winding W4 are respectively wound on magnetic cores C1 to C4. The first clamp head 1 includes a first housing 101 and a second housing 102; both the first housing 101 and the second housing 102 are provided with grooves, and the first housing 101 and the second housing 102 are interlocked, so that the grooves form an annular space inside the housing for arranging magnetic cores C1, C2, C3, and C4. Among them, magnetic cores C1, C2, and C3 are all semi-circular magnetic cores, and the three are the same size and are stacked in the same direction. Magnetic core C4 is a semi-circular hollow structure, and its internal space is used to arrange the combined structure of magnetic cores C1 to C3; in some embodiments, magnetic core C4 includes two semi-circular outer shells, both of which are groove structures, and the two are interlocked to form a semi-circular hollow structure.

[0053] like Figure 4 As shown, the second clamp head 2 includes magnetic cores C1', C2', C3', and C4'; a first current detection winding W1', a first decoupling winding W2', a first flux detection winding W3', and a first compensation winding W4' are respectively wound on magnetic cores C1' to C4'. The arrangement structure of magnetic cores C1' to C4' is the same as that of magnetic cores C1 to C4, and will not be described again here. (Refer to...) Figure 4It should be noted that the magnetic cores C1' to C4' are arranged in the housing 201, and the top end of the magnetic core C4' is flush with the top end of the housing 201, and the top ends of the magnetic cores C1' to C3' are higher than the end of the housing 201, that is, the top ends of the magnetic cores C1' to C3' extend out of the top end of the housing 201 by a certain length.

[0054] Correspondingly, in the first jaw 1, the top end of the magnetic core C4 is flush with the housings 101 and 102, and the top ends of the magnetic cores C1 to C3 are lower than the end of the housings 101 and 102, that is, the top ends of the magnetic cores C1 to C3 are sunken into the inside of the housings 101 and 102 by a certain length, and the magnetic core C1 is inserted into the magnetic core C1' by a length of several millimeters. Moreover, the top ends of the magnetic cores C1' to C3' are higher than the length of the housing 201 by a length equal to the length by which the top ends of the magnetic cores C1 to C3 are lower than the length of the housing, so that the first jaw 1 and the second jaw 2 can be combined with each other. Such a structure can increase the contact area of C1 to C3 and C1' to C3', and ensure that the magnetic permeability of the magnetic cores is reduced less.

[0055] As shown in FIG. 1, Figure 5 The structure of the jaw includes an outer shell 101 at the outermost side, the cross section of the outer shell 101 is rectangular, and the outer shell limiting blocks 103 are arranged on the four side walls of the rectangle. The winding W4 is arranged inside the outer shell 101, and the outer side of the winding W4 is wrapped with a layer of anti-static copper foil 104. The anti-vibration insulation layer 106 is filled between the outer shell 101 and the winding W4. The anti-vibration insulation layer 106, the magnetic shielding layer 105 and the combined structure of the magnetic cores C1 to C3 are sequentially arranged inside the winding W4. The anti-static copper foil 104 is arranged in the anti-vibration insulation layer 106 between the winding W4 and the magnetic shielding layer 105. The combined structure of the magnetic cores C1 to C3 includes the magnetic cores C1 to C3 arranged side by side, the windings W1 to W3 on the magnetic cores C1 to C3, and the anti-vibration insulation layer 106 wrapped between the windings W1 to W3. It should be noted that the structure of the first jaw 1 and the second jaw 2 is the same, and both are the above-mentioned multi-layer structure.

[0056] The purpose of the present application is to provide an active magnetic compensation clamp current sensor and a magnetic compensation method to solve the problems of insufficient accuracy and susceptibility to external temperature and magnetic field interference of the current sensor. The present application proposes a new structure, which realizes the opening and closing of the magnetic flux gate current sensor, and based on the new circuit principle, realizes the magnetic flux gate principle based on active magnetic compensation, and realizes high precision. Compared with the existing clamp current sensor, it can simultaneously measure AC and DC, is not affected by the environment temperature, and has greatly improved accuracy.

[0057] In order to make the purpose, technical scheme and advantages of the present application clearer, the embodiments of the present application will be further described in detail below with reference to the drawings.

[0058] The clamp-shaped current sensor further comprises an excitation circuit, a compensation circuit and a detection circuit; the excitation circuit is used for generating an excitation signal and modulating the excitation signal to the first excitation winding and the second excitation winding; the detection circuit is used for acquiring the current signals on the current detection winding and the excitation winding, and integrating to generate an error signal; and the compensation circuit is used for acquiring the error signal and generating a compensation signal applied to the first compensation winding and the second compensation winding.

[0059] As shown in the accompanying drawings, Figure 6 The present application provides a kind of active magnetic compensation clamp-shaped current sensor and magnetic compensation scheme, including clamp head, waveform generator, frequency divider, magnetic modulation power amplifier, LDO, magnetic demodulation unit, error synthesis unit, band-pass filter, servo power supply, mechanical board machine, linkage switch, overload detection, measurement resistance Rs, amplitude amplification unit.

[0060] Clamp head: it is the core device of sensor for magnetic detection, compensation, and is composed of first clamp head 1 and second clamp head 2.The first clamp head 1 includes magnetic core C1, C2, C3, C4, winding W1, W2, W3, W4.The second clamp head 2 includes magnetic core C1', C2', C3', C4', winding W1', W2', W3', W4'.C1, C1' constitute direct current detection magnetic core.C2, C2' constitute decoupling magnetic core.C3, C3' constitute alternating current zero magnetic flux detection magnetic core, and W4, W4' constitute magnetic potential compensation magnetic core.W1-W4, W1'-W4' are wound on C1-C4, C1'-C4' respectively. P It is the signal to be measured, passing through the hole of the clamp head.

[0061] In some embodiments, the excitation circuit comprises a waveform generator, a frequency divider and a magnetic modulation power amplifier.

[0062] The waveform generator is used for generating waveform signals with preset frequency and amplitude; it provides stable and reliable frequency and amplitude waveform, which can be square wave, sine wave or triangular wave.It should be noted that in other embodiments, the waveform generation unit can also use the inductance of magnetic core C1-C3 to form an LC waveform generator.

[0063] The frequency divider is used for frequency division processing of the waveform signals generated by the waveform generator; it provides 1 / 2 waveform generator frequency as the frequency source of the magnetic core excitation signal.

[0064] The magnetic modulation power amplifier is used for modulating the waveform signals output by the frequency divider to the windings W2, W2', W3, W3', so as to excite them to magnetic saturation.It should be noted that in other embodiments, the magnetic modulation power amplifier can be modulated in the form of transformer coupling, thereby replacing the magnetic modulation power amplifier modulation.

[0065] LDO: it provides stable power supply voltage for all units on the sensor body.

[0066] In some embodiments, the detection circuit comprises a magnetic demodulation unit and an error synthesis unit.

[0067] The magnetic demodulation unit is driven by the waveform signal output by the waveform generator, and demodulates the DC error signal on the magnetic cores C2, C2', C3, C3'. The circuit block diagram of the magnetic demodulation unit is shown in Figure 7 .

[0068] The error synthesis unit is used to obtain the DC error signal output by the magnetic demodulation unit and the AC error signal coupled out of the windings W1, W1', and to integrate the DC error signal and the AC error signal to generate an error signal. The circuit block diagram of the error synthesis unit is shown in Figure 8 .

[0069] In some embodiments, the compensation circuit comprises a servo power supply; the servo power supply is used to output the error signal after power amplification to the compensation windings W4, W4', so that the error signal on the error synthesizer is continuously reduced to close to zero, forming a closed-loop control.

[0070] In some embodiments, the compensation circuit further comprises a band elimination filter; the band elimination filter is connected between the error synthesis unit and the servo power supply, and is used to suppress the conducted modulation ripple caused by the error synthesis unit; thereby reducing the interference of the excitation signal to the error synthesizer.

[0071] Mechanical board machine: pressed down before the opening of the clamp current sensor, the contact in the board machine is conducted.

[0072] Linkage switch: cooperates with the mechanical board machine, and is used to disable the output of the servo power supply and the output of the magnetic modulation power amplifier when the mechanical board machine is conducted, so as to ensure that the magnetic core will not be over-saturated due to the decrease of the magnetic permeability caused by the air gap generated by the opening of the clamp.

[0073] In some embodiments, the overload protection unit is used to detect the DC error signal output by the magnetic demodulation unit, and outputs a protection signal to the error synthesis unit when the measured DC signal exceeds the measurement range; finally, the servo power supply outputs a periodically changing compensation current, and waits for the measured current to return to the normal measurement range, and the magnetic potential formed by the compensation current is equal, and the overload protection unit stops working, and the sensor returns to the normal working range.

[0074] Measurement resistance R s : connected in series with the compensation windings W4, W4', and converts the compensation current into a voltage signal. It should be noted that the measurement resistance R s is an optional component, and the embodiment without the measurement resistance can also realize the measurement function of the present application.

[0075] Amplitude amplification unit: adjust the voltage signal on the measurement resistance R s to the set output range. For example, 5V output corresponding to 1kA, or 10V output corresponding to 1kA. It should be noted that the amplitude amplification unit is an optional unit, and the embodiment not including the unit can also realize the measurement function of the present application.

[0076] Compared with the existing fluxgate sensor, the magnetic cores C1-C3 are cut according to the required appearance, so that they have an openable and closable clamp structure. The air gap is adjusted by process to ensure that the magnetic permeability is at a high point, thereby ensuring the sensitivity of the sensor.

[0077] The working principle of the scheme of the present application will be described in detail below in combination with specific application scenarios.

[0078] The waveform generator generates a fixed frequency f, the frequency f generated by the waveform generator is divided into C1 modulation signal 1 / 2 and C2 modulation signal with a phase difference of 180 degrees by the frequency division and inverting unit; the magnetic modulator excites the magnetic cores C1-C1' and C2-C2' to magnetic saturation by using the f / 2 frequency of the frequency divider; the magnetic parameters of C2-C2' are nearly identical to those of C1-C1', and the excitation signal on C2-C2' has a phase difference of 180 degrees with the C1 modulation signal; the excitation currents of C1 and C2 are combined on the capacitor C1 through the current limiting resistors R1 and R2, and the capacitor C1, as an excitation current maintaining unit, at the same time, forms a low-pass filter with R1 and R2 to filter out high-frequency interference. When the primary current I p is zero, the magnetic demodulation unit detects the direct current error signal on the excitation signal under the drive of the waveform generator, the hysteresis loop is symmetrical, the error signal is nearly 0, and the introduction of the primary current causes the magnetic potential on the magnetic core C1 to shift, generating a direct current error signal; the error synthesizer receives the direct current error of the magnetic demodulation unit and the alternating current error signal of the alternating current zero magnetic detection winding W1 and W1', and synthesizes them into a signal, so that the clamp-shaped sensor can measure both direct current signals and alternating current signals.

[0079] The band-stop filter filters out the modulation ripple at 1 / 2 frequency in the synthesized signal of the error synthesizer, the servo power amplifier amplifies the output signal of the band-stop filter, the difference synthesis signal power amplifier, and outputs to the compensation winding W4 and W4', until the error signal on the error synthesizer is close to zero, forming a closed-loop magnetic compensation effect.

[0080] The error signal close to zero indicates that the magnetic potential generated by the primary current I p is equal to the magnetic potential generated by the compensation current. That is, p ×W p = I s ×(W4+W4’), W p, W4, W4' are parameters fixed when making the sensor, here as a constant, so the measured current I s can be accurately calculated p .

[0081] R s and W4, W4' in series, the amplitude amplification adjusts the voltage signal on R s to the set output range. For example, 5V output corresponding to 1kA, or 10V output corresponding to 1kA. The output voltage V out of the amplitude amplification unit can also accurately calculate the measured current I p .

[0082] When needed, press the mechanical plate on the jaw to open the jaw, and put in the measured primary current bus. The plate is connected with the linkage switch, and the plate is pressed down to disable the servo power supply, and then disconnect the magnetic modulation power amplifier. When the jaw is opened, there is a large air gap in the magnetic core, which causes the magnetic permeability of the magnetic core to be severely reduced. Due to the reduction of the magnetic permeability, the magnetic flux gate effect is weakened or even disappears, so that the closed-loop magnetic compensation effect disappears, and the measurement function of the sensor is lost. When the air gap of the magnetic core increases to resonate with the excitation frequency, the magnetic core eddy current will increase, which produces difficult-to-eliminate residual magnetism. The instability of the residual magnetism causes the magnetic equilibrium point of the magnetic core to change when the jaw is closed again, resulting in a decrease in measurement accuracy. Therefore, the mechanical plate is added to the invention, which disconnects the servo power supply and then disconnects the magnetic modulation power amplifier output before the jaw is opened, avoiding the above process, thereby ensuring the consistency of the magnetic performance of the magnetic core before and after opening, and improving the accuracy of the sensor measurement.

[0083] The overload protection unit monitors the excitation current signal in real time, and outputs a protection signal to the error composition when the excitation current is not in the design interval, so that the servo power supply finally outputs a periodically varying compensation current, and waits for the measured current to return to the normal measurement range. When the magnetic potential formed by the compensation current is equal, the overload protection unit stops working, and the sensor returns to the normal working range. The overload protection unit ensures that the magnetic core will not be over-saturated to produce irreversible residual magnetism due to the existence of I p , which permanently reduces the accuracy of the clamp current sensor, thereby ensuring the safety and stability of the sensor.

[0084] The technical key points of the present application are: 1. Through special structural design, the magnetic core can be opened and closed to form a clamp current sensor while ensuring that the magnetic permeability is reduced as little as possible; 2. There are mechanical plates and linkage switches and other auxiliary units to ensure that the sensor will not produce residual magnetism in the magnetic core and reduce the accuracy due to the existence of air gap when the jaw is opened; 3. The band-stop filter reduces the interference caused by the modulation frequency signal and reduces the local noise, thereby improving the accuracy.

[0085] Compared with the prior art transformer, the scheme of the present application provides a more precise AC / DC current measuring device, which has AC and DC measuring functions. Compared with the prior art Hall current sensor, the present application uses the fluxgate technology, and the demodulator does not rely on the Hall chip, and the temperature drift is reduced from 100ppm / k of the prior art to 0.02ppm / k. Compared with the prior art fluxgate current sensor, the present application also uses the fluxgate technology, but can be opened and closed, and is more convenient to use; and the magnetic permeability does not decrease significantly, and the measurement accuracy does not decrease.

[0086] It can be understood that the same or similar parts in the above-mentioned embodiments can be mutually referred to, and the contents not described in detail in some embodiments can be referred to the same or similar contents in other embodiments.

[0087] It should be noted that in the description of the present application, the terms "first", "second", etc. are only for the purpose of description, and cannot be understood as indicating or implying relative importance. In addition, in the description of the present application, unless otherwise specified, the meaning of "a plurality of" is at least two.

[0088] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the present application, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0089] Although the embodiments of the present application have been shown and described above, it can be understood that the above-mentioned embodiments are exemplary and cannot be understood as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above-mentioned embodiments within the scope of the present application.

Claims

1. An active magnetic-compensated clamp-on current sensor characterized by, The utility model relates to a kind of current sensor, including: First jaw and second jaw;The first jaw and the second jaw each include magnetic core, and two can be combined to form closed ring body; The magnetic core of the first jaw is wound with first current detection winding, first excitation winding and first compensation winding;The magnetic core of the second jaw is wound with second current detection winding, second excitation winding and second compensation winding; The clamp-on current sensor further includes excitation circuit, compensation circuit and detection circuit;The excitation circuit is used to generate excitation signal, and excitation signal is modulated to first excitation winding and second excitation winding;The detection circuit is used to obtain current signal on current detection winding and excitation winding, and error signal is integrated to generate; The compensation circuit is used to obtain error signal, and compensation signal is generated to be applied to first compensation winding and second compensation winding; The excitation circuit includes waveform generator, frequency divider and magnetic modulation power amplifier; The waveform generator is used to generate waveform signal of preset frequency and amplitude; The frequency divider is used to frequency-division process waveform signal generated by the waveform generator; The magnetic modulation power amplifier is used to modulate waveform signal output by the frequency divider to winding W2, W2', W3, W3'; The detection circuit includes magnetic demodulation unit and error synthesizer; The magnetic demodulation unit is driven by waveform signal output by the waveform generator, and direct current error signal on the magnetic core is demodulated; The error synthesizer is used to obtain direct current error signal output by the magnetic demodulation unit and alternating current error signal on winding W1, W1', and error signal is integrated to generate after integration; The compensation circuit includes servo power supply;The servo power supply is used to output error signal after power amplification to compensation winding W4, W4', so that error signal on error synthesizer is continuously reduced to close to zero, forming closed-loop control; The compensation circuit includes band-stop filter;The band-stop filter is connected between the error synthesizer and the servo power supply, and is used to suppress transmission modulation ripple caused by the error synthesizer; Further comprising mechanical plate machine and linkage switch; The mechanical plate machine is pressed down before the clamp-on current sensor is opened, and the contact in the plate machine is conducted; The linkage switch cooperates with the mechanical plate machine, and is used to disable the output of the servo power supply and disable the output of the magnetic modulation power amplifier when the mechanical plate machine is conducted.

2. The clamp-on current sensor of claim 1, wherein, The first excitation winding includes first decoupling winding and first magnetic flux detection winding;The second excitation winding includes second decoupling winding and second magnetic flux detection winding.

3. The clamp-on current sensor of claim 1, wherein, The first jaw includes magnetic core C1, magnetic core C2, magnetic core C3 and magnetic core C4;First current detection winding W1, first decoupling winding W2, first magnetic flux detection winding W3 and first compensation winding W4 are wound on magnetic core C1-C4 respectively; The second jaw includes magnetic core C1', magnetic core C2', magnetic core C3' and magnetic core C4';Second current detection winding W1', second decoupling winding W2', second magnetic flux detection winding W3' and second compensation winding W4' are wound on magnetic core C1'-C4' respectively.

4. The clamp-on current sensor of claim 1, wherein, Further comprising: overload protection unit The overload protection unit is used for detecting the direct current error signal output by the magnetic demodulation unit, and outputs a protection signal to the error synthesis unit when the detected direct current signal exceeds the measurement range.

5. The clamp-on current sensor of claim 1, wherein, Also comprising: a measurement resistor Rs and an amplitude amplification unit; The measurement resistor Rs is connected in series with the compensation windings W4, W4', and converts the compensation current into a voltage signal; The amplitude amplification unit adjusts the voltage signal on the measurement resistor Rs to a set output range.

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