CN202075330U - Current measure apparatus based on equipotential heavy current screening - Google Patents
Current measure apparatus based on equipotential heavy current screening Download PDFInfo
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- CN202075330U CN202075330U CN2011201739864U CN201120173986U CN202075330U CN 202075330 U CN202075330 U CN 202075330U CN 2011201739864 U CN2011201739864 U CN 2011201739864U CN 201120173986 U CN201120173986 U CN 201120173986U CN 202075330 U CN202075330 U CN 202075330U
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- current
- equipotential
- shielding
- follower
- output terminal
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- Testing Relating To Insulation (AREA)
Abstract
The utility model describes a current measure apparatus based on equipotential heavy current screening, which employs an equipotential follower based on an operational amplifier and a current amplifying circuit to separate the interference current from the total current, and absorbs the interference current, thus influence of the interference current on the measured current is eliminated. The current measure apparatus based on equipotential heavy current screening can be used to measure the insulation resistor of an internal water-cooled electric generator, and also can be used in other application to separate the interference current from an undercurrent and measure the undercurrent.
Description
Technical field
The utility model relates to a kind of current measuring device, especially a kind of device by the big current shielding commercial measurement of equipotential water-cooled generator insulation resistance leakage current.
Background technology
Insulation resistance meter is generally used in megger test, and measuring magnitude is μ A even littler electric current.Insulation resistance meter has a shielding end, is used for absorbing the surface leakage current of measured resistance.The current potential of the shielding end of common insulation resistance meter not exclusively equates with the current potential of measuring junction, and shielding end ABSORPTION CURRENT is limited in one's ability, generally can absorb and suitable, the perhaps littler electric current of leakage current magnitude of tested insulation resistance.The megger test of water-cooled generator is a special megger test.Water-cooled generator is by being distributed in the collection pipe cooling in the generator windings.During the generator operate as normal, collection pipe is connected to support by ring flange, is ground.And when measuring the insulation resistance of water-cooled generator, the ground wire at collection pipe ring flange place is disconnected, and ring flange is connected to the shielding end of tester.Water resistance in the collection pipe can equivalence be two parts, and a part is the equivalent water resistance R between winding and the ring flange
W1, another part is the equivalent water resistance R between ring flange and the support
W2When carrying out megger test, the test high direct voltage is carried in the insulation resistance R of winding
XOn, produce measured current I
XSimultaneously, testing high voltage also is carried in to form on the water resistance and disturbs water resistance leakage current I
WFollowing problem is arranged when measuring the insulation resistance of water-cooled generator:
1) because the leakage current of water resistance is very big, may cause the shielding end of common insulation resistance meter not absorb up to 80mA.Consequently the leakage current of water resistance passes through R
W2Flow into support, thereby enter the measurement passage, cause measuring error.Therefore common insulation resistance meter is not suitable for measuring the insulation resistance of water-cooled generator.
2) for eliminating the influence of water resistance leakage current, special-purpose water-cooled generator Insulation Resistance Tester ZC-37 adopts the method for manual shift, between dc high-voltage source and ring flange, adjust fixing and water resistance leakage current equal and opposite in direction, an opposite polarity electric current, to offset of the influence of water resistance leakage current to the measurement insulation resistance leakage current.And during proper testing,, cause that the water resistance resistance changes because the water in the collection pipe is polarized after loading high pressure.And the variation of water resistance resistance can cause the variation of water resistance leakage current.Bu Chang fixed current had just lost efficacy so, before.
Summary of the invention
At above problem, the utility model proposes a kind of current measuring device based on the big current shielding of equipotential, both guaranteed shielding end and support end equipotential, and guaranteed that again the shielding end can absorb big electric current, and adopt the electric current and voltage double lead that separates to eliminate the influence of lead resistance equivalent potential screen.
The technical scheme that its technical matters that solves the utility model adopts is: a kind of current measuring device based on the big current shielding of equipotential is provided, it comprises: shield end lead-in wire, the equipotential follower based on operational amplifier, expansion stream absorption circuit and current-to-voltage converting circuit, described shielding end lead-in wire adopts the current/voltage lead-in wire that separates, interference current that can will be bigger separates from total current and shields absorption, thus its influence of elimination interference current to tested electric current.
The input end of described current/voltage lead-in wire connects together, and is connected to the conductively-closed point, and the output terminal of current/voltage lead-in wire separates; Wherein, voltage lead is at internal layer, and its output terminal is connected to the inverting input of equipotential follower, and current feed is at skin, and its output terminal is connected to the output terminal that expands current circuit.
The in-phase input end of described equipotential follower based on operational amplifier connects the inverting input of current-to-voltage convertor, and its inverting input connects the output terminal of voltage lead, and its output termination bipolarity expands the input end of current circuit.
It is that the compound expansion stream of NPN, PNP absorbs circuit that described expansion stream absorbs circuit, can absorb the electric current of polarity or plus or minus, wherein the base stage of two triodes connects together, and is connected to the output terminal of equipotential follower, the emitter of two triodes also connects together, and is connected to the output terminal of current feed.
Described current/voltage lead-in wire and expansion stream absorb the backfeed loop that circuit constitutes the equipotential follower, this structure has guaranteed that the equipotential follower can follow the current potential of test lead the input end to electric current and voltage lead-in wire, thereby thoroughly eliminates the influence of lead resistance to equivalent potential screen.
After the method for the big current shielding current measuring device of described equipotential by the big current shielding of equipotential separated and sponged interference current, more tested electric current is measured, thereby eliminated the influence of interference current tested electric current.
Description of drawings
Below in conjunction with drawings and Examples the utility model is further specified.
Fig. 1 is the block diagram of the big current shielding current measuring device of equipotential.
Fig. 2 is the specific implementation circuit diagram of the big current shielding current measuring device of equipotential.
The current/voltage lead wire circuit figure of Fig. 3 for separating.
Fig. 4 is the operation amplifier circuit figure of low maladjustment voltage.
Fig. 5 expands current circuit figure for bipolarity.
Fig. 6 is the big current follower of equipotential based on operational amplifier.
Fig. 7 is current-to-voltage converting circuit figure.
Embodiment
Implementation method of the present utility model is, adopts the equipotential follow circuit based on operational amplifier, makes the current potential of ring flange end follow the current potential of support end automatically, allows water resistance R
W1Leakage current all flow into shielding end, guarantee simultaneously at water resistance R
W2On do not produce leakage current.In addition, the equivalent potential screen end must be able to absorb the leakage current up to 80mA, and can guarantee that still equipotential follows.For eliminating the influence of collection pipe lead resistance to equivalent potential screen, shielding end lead-in wire has adopted the voltage and current lead-in wire that separates.
Fig. 1 is the block diagram of the big current shielding current measuring device of equipotential, and Fig. 2 is the specific implementation circuit diagram of the big current shielding current measuring device of equipotential.R wherein
XBe the insulation resistance of water-cooled generator winding, R
W1Be the equivalent water resistance between winding and the ring flange, R
W2Be the equivalent resistance between ring flange and the support.
The current/voltage lead-in wire of Fig. 3 for separating, wherein the input end of current/voltage lead-in wire connects together, and is the B among the figure; The output terminal of voltage lead is E, and the output terminal of current feed is D.The lead-in wire of shielding end may reach 20m, and its lead resistance is greater than 0.5 Ω.When the electric current of 80mA flows through this lead-in wire, can produce tens millivolts pressure drop, cause at water resistance R
W2The last voltage V that can not ignore that produces
BCThereby, cause electric current 1
W2=V
BC/ R
W2Flow into test channel.In general, R
W2Be 10k Ω～30k Ω, then I
W2Be μ A level.The leakage current magnitude of this electric current and tested insulation resistance is suitable, therefore can cause error to the measurement of insulation electrical measurement leakage current.
Fig. 4 is the operational amplifier N of low maladjustment voltage
2, its in-phase input end is connected to the inverting input C of current-to-voltage convertor, and its inverting input meets the output terminal E of voltage lead, and its output termination bipolarity expands the input end F of current circuit.
Fig. 5 expands current circuit for bipolarity, and purpose is the current absorption ability that enlarges the equipotential follower.Expand current circuit by current-limiting resistance R
2, NPN triode T
1, PNP triode T
2Constitute.T
1, T
2Adopt through-current capability to constitute compound expansion current circuit greater than the triode of 1A.T
1Collector be connected to positive supply+15V, T
2Collector be connected to GND.T
1, T
2Base stage connect together, by current-limiting resistance R
2Be connected to N
2Output terminal F.T
1, T
2Emitter also be connected together, be connected to the output terminal D of current feed.So, the interference current from shielding end inflow current lead-in wire passes through T
2Sponged by GND, and flow out the interference current of current feed by positive supply process T from shielding end
1Provide.Absorb with this shielding that realizes the bipolarity interference current.
Fig. 6 is the big current follower of equipotential based on operational amplifier, and by the current/voltage lead-in wire that separates, bipolarity expands the operational amplifier N that stream absorbs circuit and low maladjustment voltage
2Constitute.The in-phase input end of its medium potential follower is connected to the inverting input C of current-to-voltage convertor, and its inverting input is connected to the output E of pressure-wire.Expand the defeated output terminal D that is connected to current feed that brings out that stream absorbs circuit, constitute the negative feedback of equipotential follower.Because N
2Inverting input is a high impedance, and interference current all flows through from current feed.Do not have electric current to flow through on the voltage lead, so its input and output terminal potential is equal, i.e. V
B=V
EBecause N
2Two input ends be empty short, therefore V is arranged
E=V
CCan see,, can realize that the current potential of the input end of current/voltage lead-in wire follows the current potential of test input, i.e. V by this equipotential follower
BC=0, absorb interference current I fully thereby reach
W1, and guarantee I
W2=0.
Fig. 7 is a current-to-voltage converting circuit, by operational amplifier N
1With feedback resistance R
1Constitute.By big electric current equipotential follower, can sponge interference current I fully
W, then from the only remaining measured current I of the electric current of support end inflow metering circuit
XElectric current I
XFlow through R
1, at N
1Output terminal forms voltage output V
G=I
XR
1
Advantage of the present utility model is and measuring current can be separated that the interference current that measurement is not changed influences from interference current.Use the water-cooled generator Insulation Resistance Tester of this device, can be from the leakage current of motion tracking shield water resistance.Even changing, water resistance causes that leakage current changes, and also can not influence the test of insulation resistance leakage current.
Claims (5)
1. current measuring device based on the big current shielding of equipotential, it comprises that shielding end goes between, flows absorption circuit and current-to-voltage converting circuit based on equipotential follower, the expansion of operational amplifier, it is characterized in that: described shielding end lead-in wire adopts the current/voltage lead-in wire that separates, be used for will be bigger interference current separate and shielding absorbs from total current, thereby eliminate the influence of interference current to tested electric current.
2. the current measuring device based on the big current shielding of equipotential as claimed in claim 1 is characterized in that: the input end of the current/voltage lead-in wire of described separation connects together, and is connected to the conductively-closed point, and the output terminal of described current/voltage lead-in wire separates; Voltage lead is at internal layer, and its output terminal is connected to the inverting input of described equipotential follower, and current feed is at skin, and its output terminal is connected to the output terminal that described expansion stream absorbs circuit.
3. the current measuring device based on the big current shielding of equipotential as claimed in claim 2, it is characterized in that: the in-phase input end of described equipotential follower based on operational amplifier connects the inverting input of described current-to-voltage convertor, the inverting input of described equipotential follower connects the output terminal of described voltage lead, and the described expansion stream of the output termination of described equipotential follower absorbs the input end of circuit.
4. the current measuring device based on the big current shielding of equipotential as claimed in claim 2, it is characterized in that: it is that the compound expansion stream of NPN, PNP absorbs circuit that described expansion stream absorbs circuit, can absorb the electric current that polarity is plus or minus, wherein the base stage of two triodes connects together, be connected to the output terminal of described equipotential follower, the emitter of two triodes also connects together, and is connected to the output terminal of described current feed.
5. the current measuring device based on the big current shielding of equipotential as claimed in claim 2, it is characterized in that: described current feed and described expansion stream absorbs the backfeed loop that circuit constitutes the equipotential follower, is used for the current potential of the test lead of equipotential follower is followed to the input end of current/voltage lead-in wire.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2011201739864U CN202075330U (en) | 2011-05-27 | 2011-05-27 | Current measure apparatus based on equipotential heavy current screening |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2011201739864U CN202075330U (en) | 2011-05-27 | 2011-05-27 | Current measure apparatus based on equipotential heavy current screening |
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| Publication Number | Publication Date |
|---|---|
| CN202075330U true CN202075330U (en) | 2011-12-14 |
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ID=45113427
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN2011201739864U Expired - Fee Related CN202075330U (en) | 2011-05-27 | 2011-05-27 | Current measure apparatus based on equipotential heavy current screening |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104345201A (en) * | 2013-08-09 | 2015-02-11 | 华为技术有限公司 | Leakage current detection method and device |
| US9625517B2 (en) | 2013-08-09 | 2017-04-18 | Huawei Technologies Co., Ltd. | Leakage current detection method and apparatus for detecting leakage of current from a board-mounted component |
| CN110031678A (en) * | 2019-03-27 | 2019-07-19 | 武汉市康达电气有限公司 | Water-cooled generator Insulation Resistance Tester |
-
2011
- 2011-05-27 CN CN2011201739864U patent/CN202075330U/en not_active Expired - Fee Related
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104345201A (en) * | 2013-08-09 | 2015-02-11 | 华为技术有限公司 | Leakage current detection method and device |
| WO2015018189A1 (en) * | 2013-08-09 | 2015-02-12 | 华为技术有限公司 | Leakage current detection method and device |
| US9625517B2 (en) | 2013-08-09 | 2017-04-18 | Huawei Technologies Co., Ltd. | Leakage current detection method and apparatus for detecting leakage of current from a board-mounted component |
| CN110031678A (en) * | 2019-03-27 | 2019-07-19 | 武汉市康达电气有限公司 | Water-cooled generator Insulation Resistance Tester |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20111214 Termination date: 20150527 |
|
| EXPY | Termination of patent right or utility model |