CN105304303A - Precise AC-DC large current transformer - Google Patents
Precise AC-DC large current transformer Download PDFInfo
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- CN105304303A CN105304303A CN201510642231.7A CN201510642231A CN105304303A CN 105304303 A CN105304303 A CN 105304303A CN 201510642231 A CN201510642231 A CN 201510642231A CN 105304303 A CN105304303 A CN 105304303A
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Abstract
The invention provides a precise AC-DC large current transformer. According to the transformer, based on a zero flux principle, a self-oscillation magnetic modulator technology with relatively simple modulation and demodulation circuits is combined with an active AC current transformer technology, wherein a self-oscillation magnetic modulator is used for detecting DC flux, and an active AC current transformer is used for detecting AC flux. During normal work hours, the transformer always works at a zero flux state no matter the detected current is DC current or AC current, and thus the measurement accuracy of the DC current and AC current can be improved at the same time. Moreover, the ripple current sensed at the primary-side and secondary-side windings by the excitation flux of the self-oscillation magnetic modulator due to a transformer effect is inhibited by adopting an excitation flux compensating circuit, and the ripple current generated in secondary-side windings due to the fact that the time constant of the useful signal extraction circuit of the self-oscillation magnetic modulator is limited is inhibited by adopting a high-pass filter, so that the measurement accuracy is further improved.
Description
Technical field
The invention belongs to big current field of precision measurement, particularly relate to a kind of accurate alternating current-direct current great current mutual inductor.
Background technology
The accurate measurement of D.C. high-current is generally by realizing based on the comparator for direct current of traditional magnetic modulator technology or Zero magnetic flux direct-current current transformer, but be subject to the restriction of the wherein modulating frequency of magnetic modulator, this quasi-instrument can only be used for measuring direct current or low-frequency ac.The accurate measurement of AC great current is generally then realized by AC current comparator or Zero flux AC current transformer, but this quasi-instrument can only be used for measuring interchange, and is not suitable for direct current.Therefore, for needing the application scenario measuring direct current and AC great current simultaneously, two quasi-instruments all can not complete independently.
The existing instrument transformer simultaneously can measuring direct current and AC great current at present, but the DC measurement function of this quasi-instrument mostly have employed traditional magnetic modulator technology, and circuit is complicated, and cost is higher, limits it to a certain extent and uses.The replacement scheme of low cost adopts the relatively simple self-oscillation magnetic modulator of modulation and demodulation circuit to make a direct current flux detector, has at present and can measure direct current based on the great current mutual inductor of this technology simultaneously and exchange.
But, there are two subject matters in such instrument transformer at present: one is owing to lacking modulation flux compensation magnetic core and winding, the modulation magnetic flux of self-oscillation magnetic modulator can respond to the ripple current of certain amplitude in instrument transformer former limit winding and vice-side winding by transformer action, ripple current in the winding of former limit can disturb tested loop, and the ripple current in vice-side winding can increase measure error.Two is the restrictions by the transducer response time, wherein the time constant of the useful signal extraction circuit of self-oscillation magnetic modulator can not arrange too large, the problem brought thus is that the high fdrequency component in useful signal can not be actively damped, this high fdrequency component directly will produce ripple current as error signal drives feedback control circuit, thus introduce measure error.Therefore, such current transformer can't be used for accurate measurement at present.
Fig. 1 is a kind of schematic diagram of the existing alternating current-direct current great current mutual inductor based on self-oscillation magnetic modulator.The gage outfit of two toroidal core C1 and C2 and three winding W1, W3 and W4 formation instrument transformers in Fig. 1, winding W5 is generally the single turn conductor through instrument transformer gage outfit, for flowing through tested big current IP.All the other elements form the signal conditioning circuit of instrument transformer, for signal extraction and FEEDBACK CONTROL.Be wrapped in the winding W1 on magnetic core C1, comparator A1 and exciting curent sampling resistor R1 formation self-oscillation magnetic modulator, for detecting direct current flux.The high fdrequency component of low pass filter B2 in filtering exciting curent (or exciting curent pressure drop v2 on sampling resistor R1) thus obtain useful signal v7.Be wrapped in winding W3 on magnetic core C2 for detecting exchange flux, its output signal v8 is added with signal v7 by summing circuit D2, and the output signal v9 of summing circuit D2 exports secondary current IS for compensating the magnetic flux of measured current I P generation as error signal drives feedback control circuit A3 and power amplification circuit A4 thereof, finally reach Zero flux state.
But, there are two subject matters in such instrument transformer at present: one is owing to lacking modulation flux compensation magnetic core and winding, the modulation magnetic flux of self-oscillation magnetic modulator can respond to the ripple current of certain amplitude in instrument transformer former limit winding W5 and vice-side winding W4 by transformer action, ripple current in former limit winding W5 can disturb tested loop, and the ripple current in vice-side winding W4 can increase measure error.Two is the restrictions by the instrument transformer response time, the time constant of the useful signal extraction circuit B2 of self-oscillation magnetic modulator wherein can not arrange too large, the problem brought thus is that the high fdrequency component in useful signal can not be actively damped, this high fdrequency component directly will produce ripple current as error signal drives feedback control circuit A3 and power amplification circuit A4 thereof, thus introduce measure error.Therefore, such instrument transformer can't be used for accurate measurement at present.
Summary of the invention
In order to solve the shortcoming that alternating current-direct current great current mutual inductor circuit structure is complicated, cost is higher based on traditional magnetic modulator, the alternating current-direct current great current mutual inductor former and deputy limit modulation ripple simultaneously solved based on emerging self-oscillation magnetic modulator can not be used for greatly the shortcoming of accurate measurement, the invention provides that a kind of structure is simple, the accurate alternating current-direct current great current mutual inductor of relative inexpensiveness, comprise gage outfit, for measuring the big current flowing through former limit winding; Self-oscillation magnetic modulator circuit, for detecting direct current flux; Magnetizing flux compensating circuit, for offsetting the ripple current of magnetizing flux induction; And Zero flux AC current transformer circuit, for detecting exchange flux.
According to a preferred embodiment of the invention, the gage outfit of accurate alternating current-direct current great current mutual inductor is made up of three toroidal cores, two excitation windings, exchange flux detection winding, vice-side winding, two field windings are wrapped on two toroidal cores respectively, exchange flux detects winding and is wrapped on three toroidal cores stacked back-to-back, and vice-side winding is wrapped on exchange flux detection winding, the gage outfit of accurate alternating current-direct current great current mutual inductor passes former limit winding, for measuring the big current flowing through former limit winding.
According to present invention further optimization embodiment, the physical characteristic of described two toroidal cores is identical with geometric parameter, the geometric parameter of the 3rd described toroidal core is identical with described two toroidal cores, but physical characteristic can be identical, also can be different, the number of turn of described two excitation windings is identical, and vice-side winding is wrapped in exchange flux and detects on winding.
According to present invention further optimization embodiment, self-oscillation magnetic modulator circuit is made up of the first field winding, comparator and the first resistance, the Same Name of Ends of output termination first field winding of comparator, the non-same polarity of the first field winding connects the input of comparator, be connected with the first resistance simultaneously, the other end ground connection of the first resistance.
According to present invention further optimization embodiment, magnetizing flux compensating circuit is made up of the second field winding, unity gain inverter and the second resistance, the input of unity gain inverter is connected with the output of comparator, the Same Name of Ends of output termination second field winding of unity gain inverter, the non-same polarity of the second field winding connects the second resistance, the other end ground connection of the second resistance.
According to present invention further optimization embodiment, also comprise the first summing circuit, second summing circuit, low pass filter, and high pass filter, two inputs of the first summing circuit connect the ungrounded end of the first resistance and the output of high pass filter respectively, and the output of the first summing circuit connects the input of low pass filter, and two inputs of the second summing circuit connect the output of low pass filter and the Same Name of Ends of exchange flux detection winding respectively.
According to present invention further optimization embodiment, wherein Zero flux AC current transformer circuit detects winding, feedback control circuit, power amplification circuit, vice-side winding and the 3rd resistance by exchange flux and forms, the input of feedback control circuit connects the output of the second summing circuit, the output of feedback control circuit connects the input of power amplification circuit, power amplification circuit connects the Same Name of Ends of vice-side winding, the non-same polarity of vice-side winding connects the 3rd resistance, the other end ground connection of the 3rd resistance.
According to present invention further optimization embodiment, wherein feedback control circuit adopts the proportional, integral circuit be made up of operational amplifier.
According to present invention further optimization embodiment, wherein after described proportional, integral circuit, connect power amplifier output mutual inductor secondary current, this power amplifier is any one in category-A, category-B, AB class or D class, or is made up of multiple discrete component, or is made up of single integrated device.
According to present invention further optimization embodiment, described low pass filter is any one in passive first order low pass filter, passive high-order low-pass filter, active first-order low pass filter and active high-order low-pass filter, and described high pass filter is any one in passive first order high pass filter, passive higher order high pass filters, active first-order high pass filter and active higher order high pass filters.
This accurate alternating current-direct current great current mutual inductor is based on Zero flux principle, relatively simple for modulation and demodulation circuit self-oscillation magnetic modulator technology is combined with active ac current transformer technology, wherein self-oscillation magnetic modulator is for detecting direct current flux, and active ac current transformer is for detecting exchange flux.Like this, when normally working, no matter for direct current or exchange tested electric current, instrument transformer can be operated in Zero flux state all the time, thus can improve the certainty of measurement of direct current and alternating current simultaneously.In addition, have employed additional magnetic core and winding for compensating the ripple current responded on former limit and vice-side winding due to transformer action, and on the basis of additional magnetic core and winding, have employed high pass filter for offsetting the high fdrequency component in useful signal, thus reduce because useful signal extracts circuit, the i.e. limited ripple current produced in vice-side winding of the time constant of low pass filter.
Accompanying drawing explanation
In order to be illustrated more clearly in the embodiment of the present invention, be briefly described to the accompanying drawing used required in embodiment below.Obviously, the accompanying drawing in below describing is only section Example of the present invention, for those of ordinary skills, can also obtain other embodiment and accompanying drawing thereof according to these accompanying drawing illustrated embodiments.
Fig. 1 is a kind of schematic diagram of the existing alternating current-direct current great current mutual inductor based on self-oscillation magnetic modulator;
Fig. 2 is the schematic diagram of accurate alternating current-direct current great current mutual inductor provided by the invention.
Linearity when Fig. 3 is accurate alternating current-direct current great current mutual inductor measurement direct current provided by the invention.
Frequency bandwidth when Fig. 4 is accurate alternating current-direct current great current mutual inductor measurement alternating current provided by the invention.
Embodiment
Carry out clear, complete description below with reference to accompanying drawing to the technical scheme of embodiments of the invention, obviously, described embodiment is only section Example of the present invention, instead of whole embodiment.Based on embodiments of the invention, other embodiments all that those of ordinary skill in the art obtain under the prerequisite not making creative work, all belong to the scope that the present invention protects.
Fig. 2 is the schematic diagram of accurate alternating current-direct current great current mutual inductor provided by the invention.The gage outfit of three toroidal cores C1, C2, C3 and four winding W1, W2, W3, W4 formation instrument transformers in figure, wherein two field winding W1 and W2 are wrapped on toroidal core C1 and C2 respectively, exchange flux detects winding W3 and is wrapped on three magnetic core C1, C2 and C3 stacked back-to-back, and vice-side winding W4 is wrapped on winding W3.Former limit winding W5 is the single turn conductor through instrument transformer gage outfit, for flowing through tested big current IP.The stain on each winding side represents Same Name of Ends.
Winding W1, comparator (or operational amplifier) A1 and resistance R1 form self-oscillation magnetic modulator for detecting direct current flux, and general principle is the linear relationship based on existing between the mean value of the exciting curent of winding W1 and tested electric current (or magnetic flux).The concrete connected mode of self-oscillation magnetic modulator is: the Same Name of Ends of the output termination winding A1 of comparator (or operational amplifier) A1, the non-same polarity of winding A1 connects the input of comparator A1, be connected with resistance R1 simultaneously, the other end ground connection of resistance R1.
Winding W2, unity gain inverter A2 and resistance R2 form magnetizing flux compensating circuit, the ripple current that the magnetizing flux for offsetting in magnetic core C1 is responded in vice-side winding W4 and former limit winding W5 due to transformer action.The concrete connected mode of magnetizing flux compensating circuit is: the input of unity gain inverter A2 is connected with the output of comparator (or operational amplifier) A1, the Same Name of Ends of the output termination winding W2 of unity gain inverter A2, the non-same polarity connecting resistance R2 of winding W2, the other end ground connection of resistance R2.
The effect of high pass filter B1 is the low frequency component in exciting curent in the filtering winding W2 pressure drop v4 on resistance R2, its output signal v5 is offseted by the high fdrequency component in the pressure drop v2 of the exciting curent in summing circuit D1 and winding W1 on resistance R1, and the signal v7 that final output high fdrequency component is minimum after low pass filter B2 decays further of the remaining high fdrequency component in the output signal v6 of summing circuit D1.
Winding W3 is for detecting exchange flux, output signal v9 after its induced signal v8 is added with signal v7 by summing circuit D2 is as the error signal of system, drive feedback control circuit A3 and power amplification circuit A4 thereof exports the magnetic flux that offset current IS produces for offsetting measured current I P, until realize ampere-turn equilibrium, i.e. IS*W4=IP*W5.Because the number of turn of winding W4 and W5 is known, and current IS is accurately measured by the four-terminal resistance R3 be in series with winding W4 and is obtained, thus can in the hope of the value of electric current I P.
Relatively simple for above-mentioned modulation and demodulation circuit self-oscillation magnetic modulator technology combines with Zero flux AC current transformer technology by accurate alternating current-direct current great current mutual inductor provided by the invention, like this, for the tested electric current of direct current, above-mentioned self-oscillation magnetic modulator and useful signal thereof extract circuit B2 and feedback control circuit A3, power amplification circuit A4 and vice-side winding W4 forms closed loop, and for the tested electric current of interchange, exchange flux detects winding W3 and feedback control circuit A3, power amplification circuit A4 and vice-side winding W4 forms Zero flux AC current transformer, thus Zero flux state can be set up all the time in very wide frequency band, thus improve the certainty of measurement of direct current and alternating current simultaneously.Above-mentioned magnetizing flux compensating circuit add the ripple current that inhibit the magnetizing flux of self-oscillation magnetic modulator to respond in former limit winding W5 and vice-side winding W4 due to transformer action, high pass filter B1 adds, and inhibits the useful signal due to self-oscillation magnetic modulator to extract circuit, the i.e. limited ripple current caused in vice-side winding W4 of the time constant of low pass filter B2, thus further increase certainty of measurement.
Linearity when Fig. 3 is accurate alternating current-direct current great current mutual inductor measurement direct current provided by the invention.In figure, transverse axis represents tested electric current, and the longitudinal axis represents the difference current between the secondary current IS of instrument transformer provided by the invention and the output current of national 5kA D.C. high-current ratio standard device (proportional error in full scale is less than 0.5ppm).As can be seen from the figure, the secondary current difference in full scale ± 600A is maximum is about 0.65 μ A, is about 1.1ppm relative to secondary rated current ± 0.6A.
Frequency bandwidth when Fig. 4 is accurate alternating current-direct current great current mutual inductor measurement alternating current provided by the invention.In figure, transverse axis represents the frequency of measured current I P, the longitudinal axis represents the secondary output current IS of instrument transformer provided by the invention and former limit measured current I P converts the electric current of secondary ratio (representing in db form) by turn ratio W4/W5, wherein measured current I P=3Arms (effective value of sinusoidal current).As can be seen from the figure, the three dB bandwidth of instrument transformer provided by the invention is greater than 100kHz.
Obviously, those skilled in the art can carry out various change and modification to the present invention and not depart from the spirit and scope of the present invention.Like this, if belong within the scope of the claims in the present invention and equivalent technologies thereof to these amendments of the present invention and distortion, then the present invention also comprises these changes and distortion.
Claims (10)
1. an accurate alternating current-direct current great current mutual inductor, is characterized in that, comprising:
Gage outfit, for measuring the big current (IP) flowing through former limit winding (W5);
Self-oscillation magnetic modulator circuit, for detecting direct current flux;
Magnetizing flux compensating circuit, for offsetting the ripple current of magnetizing flux induction; And
Zero flux AC current transformer circuit, for detecting exchange flux.
2. accurate alternating current-direct current great current mutual inductor according to claim 1, it is characterized in that, described gage outfit is by three toroidal core (C1, C2, C3), two excitation winding (W1, W2), exchange flux detects winding (W3), vice-side winding (W4) is formed, two field winding (W1, W2) two toroidal core (C1 are wrapped in respectively, C2) on, exchange flux detects winding (W3) and is wrapped in three toroidal core (C1 stacked back-to-back, C2, C3) on, and vice-side winding (W4) is wrapped on exchange flux detection winding (W3), the gage outfit of accurate alternating current-direct current great current mutual inductor is through former limit winding (W5), for measuring the big current IP flowing through former limit winding (W5).
3. accurate alternating current-direct current great current mutual inductor according to claim 2, it is characterized in that, described two toroidal core (C1, C2) physical characteristic is identical with geometric parameter, the geometric parameter of the 3rd described toroidal core (C3) and described two toroidal core (C1, C2) identical, but physical characteristic can be identical, also can be different, the number of turn of described two excitation windings is identical, and vice-side winding (W4) is wrapped in exchange flux and detects on winding (W3).
4. accurate alternating current-direct current great current mutual inductor according to claim 2, it is characterized in that, described self-oscillation magnetic modulator circuit is made up of the first field winding (W1), comparator (A1) and the first resistance (R1), the Same Name of Ends of output termination first field winding (W1) of comparator (A1), the non-same polarity of the first field winding (W1) connects the input of comparator (A1), be connected with the first resistance (R1) simultaneously, the other end ground connection of the first resistance (R1).
5. accurate alternating current-direct current great current mutual inductor according to claim 3, it is characterized in that, described magnetizing flux compensating circuit is made up of the second field winding (W2), unity gain inverter (A2) and the second resistance (R2), the input of unity gain inverter (A2) is connected with the output of comparator (A1), the Same Name of Ends of output termination second field winding (W2) of unity gain inverter (A2), the non-same polarity of the second field winding (W2) connects the second resistance (R2), the other end ground connection of the second resistance (R2).
6. accurate alternating current-direct current great current mutual inductor according to claim 5, it is characterized in that, also comprise the first summing circuit (D1), second summing circuit (D2), low pass filter (B2), and high pass filter (B1), two inputs of the first summing circuit (D1) connect the ungrounded end of the first resistance (R1) and the output of high pass filter (B1) respectively, the output of the first summing circuit (D1) connects the input of low pass filter (B2), two inputs of the second summing circuit (D2) connect the output of low pass filter (B2) and the Same Name of Ends of exchange flux detection winding (W3) respectively.
7. accurate alternating current-direct current great current mutual inductor according to claim 6, it is characterized in that, described Zero flux AC current transformer circuit detects winding (W3) by exchange flux, feedback control circuit (A3), power amplification circuit (A4), vice-side winding (W4) and the 3rd resistance (R3) are formed, feedback control circuit (A3), input connect the output of the second summing circuit (D2), the output of feedback control circuit (A3) connects the input of power amplification circuit (A4), power amplification circuit (A4) connects the Same Name of Ends of vice-side winding (W4), the non-same polarity of vice-side winding (W4) connects the 3rd resistance (R3), the other end ground connection of the 3rd resistance (R3).
8. accurate alternating current-direct current great current mutual inductor according to claim 7, is characterized in that, described feedback control circuit (A3) adopts the proportional, integral circuit be made up of operational amplifier.
9. accurate alternating current-direct current great current mutual inductor according to claim 8, it is characterized in that, power amplifier output mutual inductor secondary current is connect after described proportional, integral circuit, this power amplifier is any one in category-A, category-B, AB class or D class, or be made up of multiple discrete component, or be made up of single integrated device.
10. accurate alternating current-direct current great current mutual inductor according to claim 6, it is characterized in that, described low pass filter (B2) is any one in passive first order low pass filter, passive high-order low-pass filter, active first-order low pass filter and active high-order low-pass filter, and high pass filter (B1) is any one in passive first order high pass filter, passive higher order high pass filters, active first-order high pass filter and active higher order high pass filters.
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| CN201510642231.7A CN105304303B (en) | 2015-09-30 | 2015-09-30 | A kind of accurate alterating and direct current current transformer |
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| CN201510642231.7A CN105304303B (en) | 2015-09-30 | 2015-09-30 | A kind of accurate alterating and direct current current transformer |
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| CN105304303B CN105304303B (en) | 2017-08-04 |
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| CN107942124A (en) * | 2017-12-14 | 2018-04-20 | 华中科技大学 | A kind of DC current compares measuring device |
| CN108593999A (en) * | 2018-06-30 | 2018-09-28 | 宁波中车时代传感技术有限公司 | A kind of Zero flux current sensor |
| CN110161296A (en) * | 2018-03-19 | 2019-08-23 | 深圳市航智精密电子有限公司 | The excitation closed control circuit and its control method of fluxgate current sensor |
| CN111693753A (en) * | 2019-11-29 | 2020-09-22 | 中国计量大学 | Novel direct current measuring device |
| CN112986654A (en) * | 2021-02-10 | 2021-06-18 | 南方电网科学研究院有限责任公司 | Current measuring device of broadband alternating current and direct current |
| CN114280350A (en) * | 2021-12-15 | 2022-04-05 | 浙江巨磁智能技术有限公司 | Large current measuring method based on high-precision current sensor and shunt |
| CN117110693A (en) * | 2023-10-25 | 2023-11-24 | 南方电网科学研究院有限责任公司 | Self-excitation type fluxgate current sensor, measuring method and electronic equipment |
| CN117214502A (en) * | 2023-09-04 | 2023-12-12 | 希斯灵顿(大连)科技有限公司 | Current sensor, detection device and detection system |
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