CN110568304A - Filter circuit of iron core grounding power frequency current - Google Patents
Filter circuit of iron core grounding power frequency current Download PDFInfo
- Publication number
- CN110568304A CN110568304A CN201910925436.4A CN201910925436A CN110568304A CN 110568304 A CN110568304 A CN 110568304A CN 201910925436 A CN201910925436 A CN 201910925436A CN 110568304 A CN110568304 A CN 110568304A
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- CN
- China
- Prior art keywords
- resistor
- capacitor
- filter circuit
- operational amplifier
- power frequency
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R1/00—Details of instruments or arrangements of the types included in groups G01R5/00 - G01R13/00 and G01R31/00
- G01R1/30—Structural combination of electric measuring instruments with basic electronic circuits, e.g. with amplifier
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
- G01R23/16—Spectrum analysis; Fourier analysis
- G01R23/165—Spectrum analysis; Fourier analysis using filters
Abstract
The invention discloses a filter circuit of iron core grounding power frequency current, which adopts an adjustable Q value double-T active band-stop filter circuit with filtering, amplifying, feedback and adjusting functions, and is additionally provided with an operational amplifier U2 with a feedback function and a potentiometer with an adjusting function on the basis of the active band-stop filter circuit, wherein the potentiometer has the function of adjusting the quality factor Q of the circuit, and two independent adjustable Q value double-T active band-stop filter circuits with narrow band stop band central frequencies of 50Hz and 100Hz are designed aiming at 50Hz power frequency and second harmonic thereof. The invention can filter the interference generated by 50Hz power frequency and harmonic thereof, improves the precision of the measured electric signal, can be randomly adjusted according to the circuit requirement in application, is more flexible in application, and can be widely applied to the aspects of low-frequency signal information processing, data transmission, interference suppression and the like.
Description
Technical Field
The invention belongs to the technical field of circuits, and relates to a band-elimination filter circuit for filtering power frequency interference, which is used for monitoring iron core grounding current of a power transformer in the power industry, in particular to a filter circuit for iron core grounding power frequency current.
Background
The circuit with selectivity to the frequency of the signal is called as the filter circuit, it can make the signal in a certain specific frequency range pass, prevent the signal outside this frequency range from passing, can be divided into four kinds of filter circuits of low-pass (LPF), high-pass (HPF), band-pass (BPF) and band-stop (BEF) according to the difference of the pass band frequency, can be divided into active filter and passive filter again according to there is active component in the filter circuit, the passive filter forms a low-resistance state access to some harmonic current through the matching of inductance and electric capacity, the passive filter is with low costs, operate steadily, but the harmonic rejection rate is generally only 80%; the active filter can effectively offset system harmonic waves, and for low-power low-frequency signals, the active filter has better overall performance than a passive filter circuit and stronger harmonic wave filtering function.
For example, CN208013294U discloses an on-line monitoring device for grounding current of a transformer core, which includes a current transformer, a filter, a range switching circuit, an AD conversion module, a microprocessor, an LED digital display, a current limiting circuit, a buzzer alarm, a GPRS module, and a monitoring terminal. The power supply and distribution in China uniformly uses the alternating current with the frequency of 50Hz, and the interference of the 50Hz power frequency signal cannot be avoided when the electric signal is acquired, processed and analyzed.
Disclosure of Invention
In view of the above, the present invention provides a filter circuit with an iron core grounded to power frequency current, so as to solve the deficiencies in the prior art.
In order to achieve the purpose, the invention is realized by the following technical scheme:
The filter circuit comprises two cascaded adjustable Q value double-T active band-stop filter circuits, wherein each adjustable Q value double-T active band-stop filter circuit comprises a first resistor, a second resistor, a third resistor, a variable resistor, a first capacitor, a second capacitor, a third capacitor, a first operational amplifier and a second operational amplifier, the negative input ends of the first capacitor, the second capacitor and the first operational amplifier are sequentially connected in series, the negative input ends of the first resistor, the second resistor and the first operational amplifier are sequentially connected in series, one end of the third resistor is respectively connected with the first capacitor, the second capacitor, the first resistor and the second resistor, the other end of the third resistor is connected with the output end of the second operational amplifier, and the output ends of the first resistor, the third capacitor and the second operational amplifier are sequentially connected, the variable part of the variable resistor is connected with the positive input end of the second operational amplifier, and the variable resistor is connected with the output end of the first operational amplifier and is grounded.
The technical scheme of the invention has the beneficial effects that:
the interference generated by 50Hz power frequency and harmonic waves thereof can be filtered, the precision of the measured electric signal is improved, the circuit can be randomly adjusted according to the circuit requirements in application, the application is more flexible, and the designed circuit can be widely applied to the aspects of low-frequency signal information processing, data transmission, interference suppression and the like.
Drawings
FIG. 1 is a schematic view of the structure of the present invention.
Detailed Description
The invention is further described with reference to the following drawings and specific examples, which are not intended to be limiting.
referring to fig. 1, the filter circuit of the iron core grounded power frequency current of the present invention includes two cascaded adjustable Q value double-T active band-stop filter circuits 1, the adjustable Q value double-T active band-stop filter circuit 1 includes a first resistor R1, a second resistor R2, a third resistor R3, a variable resistor Rw, a first capacitor C1, a second capacitor C2, a third capacitor C3, a first operational amplifier U1 and a second operational amplifier U2, a negative input end of the first capacitor C1, a second capacitor C2 and the first operational amplifier U1 are sequentially connected in series, a negative input end of the first resistor R1, the second resistor R2 and the first operational amplifier U1 are sequentially connected in series, one end of the third resistor R3 is respectively connected to the first capacitor C1, the second capacitor C2, the first resistor R1 and the second resistor R2, the other end is connected to an output end of the second operational amplifier U2, the first resistor R6342, the third resistor R5928 and the second operational amplifier U599 are sequentially connected to an output end of the second operational amplifier U2, the variable part of the variable resistor Rw is connected with the positive input end of the second operational amplifier U2, and the variable resistor Rw is connected with the output end of the first operational amplifier U1 and is grounded.
According to the design of the filter circuit for filtering 50Hz power frequency interference, the adjustable Q value double-T active band-stop filter circuit with the functions of filtering, amplifying, feeding back and adjusting is adopted, and a second operational amplifier U2 with the feedback function and a potentiometer (variable resistor Rw) with the adjusting function are added on the basis of the active band-stop filter circuit. The potentiometer Rw has the function of adjusting the quality factor Q of the circuit, the larger the Q value is, the narrower the stop band width is, and the better the frequency selection characteristic is. As shown in the figure, the filter circuit for filtering the 50Hz power frequency interference is designed with two narrow-band stop-band active band-stop filter circuits with independent adjustable Q values of 50Hz and 100Hz respectively aiming at the 50Hz power frequency and the second harmonic thereof, and the two circuits are connected in series to form the band-stop filter circuit with the function of filtering the 50Hz power frequency interference. In the design of a 50Hz band-stop filter circuit, when C1 ═ C2 ≈ 0.01pF, R1 ≈ R2 ≈ 318.4k Ω, C3 ≈ 0.02 μ F, and R3 ≈ 159.2k Ω. In the design of a 100Hz band-stop filter circuit, when C4 ═ C5 ≈ 0.02 μ F, R4 ≈ R5 ≈ 79.6k Ω, C6 ≈ 0.04 μ F, and R6 ≈ 39.8k Ω. The potentiometers Rw1 and Rw2 are adjusted to enable the center frequency of the stop band to be at 50Hz and 100Hz respectively, and the bandwidth of the stop band to be within 2Hz, so that the purpose of completely filtering 50Hz power frequency signals and second harmonic interference thereof in the output voltage Vo is achieved.
For the low-frequency electronic measuring equipment widely applied at present, the scheme uses the mode of combining the adjustable double-T active band elimination filter circuit to filter the 50Hz power frequency interference, although the design is designed and researched aiming at the 50Hz power frequency and the second harmonic thereof, the circuit can be popularized to the higher harmonic noise for filtering the power frequency interference, in addition, the potentiometer is added to have the adjustable function, so that the designed circuit can be randomly adjusted according to the circuit requirement in application, the application is more flexible, and the designed circuit can be widely applied in the aspects of low-frequency signal information processing, data transmission, interference suppression and the like.
While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.
Claims (1)
1. The filter circuit of the iron core grounding power frequency current is characterized by comprising two adjustable Q value double-T active band-stop filter circuits which are cascaded mutually, wherein each adjustable Q value double-T active band-stop filter circuit comprises a first resistor, a second resistor, a third resistor, a variable resistor, a first capacitor, a second capacitor, a third capacitor, a first operational amplifier and a second operational amplifier, the negative electrode input ends of the first capacitor, the second capacitor and the first operational amplifier are sequentially connected in series, the negative electrode input ends of the first resistor, the second resistor and the first operational amplifier are sequentially connected in series, one end of the third resistor is connected with the first capacitor, the second capacitor, the first resistor, the second resistor and the other end of the third resistor is connected with the output end of the second operational amplifier, and the first resistor and the third capacitor are connected with one end of the first capacitor, the second resistor and the other end of the third capacitor in series, The output ends of the second operational amplifiers are sequentially connected, the variable part of the variable resistor is connected with the positive input end of the second operational amplifier, and the variable resistor is connected with the output end of the first operational amplifier and grounded.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910925436.4A CN110568304A (en) | 2019-09-27 | 2019-09-27 | Filter circuit of iron core grounding power frequency current |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910925436.4A CN110568304A (en) | 2019-09-27 | 2019-09-27 | Filter circuit of iron core grounding power frequency current |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN110568304A true CN110568304A (en) | 2019-12-13 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
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| CN201910925436.4A Pending CN110568304A (en) | 2019-09-27 | 2019-09-27 | Filter circuit of iron core grounding power frequency current |
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| CN (1) | CN110568304A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111740716A (en) * | 2020-07-16 | 2020-10-02 | 江西科技学院 | Device and method for filtering power frequency interference |
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| CN107659286A (en) * | 2017-11-11 | 2018-02-02 | 成都优力德新能源有限公司 | A kind of intelligent ultra-weak electronic signal 100Hz filter circuits |
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2019
- 2019-09-27 CN CN201910925436.4A patent/CN110568304A/en active Pending
Patent Citations (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1387824A (en) * | 2002-07-26 | 2003-01-01 | 清华大学 | Alternating T-wave measuring method and device for sports electrocardiogram |
| CN102094619A (en) * | 2009-12-14 | 2011-06-15 | 武侯区巅峰机电科技研发中心 | Trap circuit of small signal amplifier for underground engineering parameter test |
| CN101822540A (en) * | 2010-04-28 | 2010-09-08 | 上海诺诚电气有限公司 | Myoelectricity amplifier and method for sampling myoelectricity signals |
| CN203933566U (en) * | 2014-05-17 | 2014-11-05 | 徐云鹏 | A kind of intelligent ultra-weak electronic signal 100Hz filter circuit |
| CN203933563U (en) * | 2014-05-17 | 2014-11-05 | 徐云鹏 | A kind of bioelectrical signals 50Hz filter circuit of hand-hold type |
| CN204119178U (en) * | 2014-09-05 | 2015-01-21 | 徐云鹏 | A kind of intelligent ultra-weak electronic signal low-power consumption filter circuit |
| CN104639085A (en) * | 2015-02-06 | 2015-05-20 | 国家电网公司 | Low-power filter circuit for weak electrical signals |
| CN204392204U (en) * | 2015-02-06 | 2015-06-10 | 国家电网公司 | A kind of ultra-weak electronic signal low-power consumption filter circuit |
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| CN111740716A (en) * | 2020-07-16 | 2020-10-02 | 江西科技学院 | Device and method for filtering power frequency interference |
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Application publication date: 20191213 |