CN201266833Y - On-line pre-detection circuit and device for protection of shorted to earth of frequency changer output end - Google Patents
On-line pre-detection circuit and device for protection of shorted to earth of frequency changer output end Download PDFInfo
- Publication number
- CN201266833Y CN201266833Y CNU2008200593098U CN200820059309U CN201266833Y CN 201266833 Y CN201266833 Y CN 201266833Y CN U2008200593098 U CNU2008200593098 U CN U2008200593098U CN 200820059309 U CN200820059309 U CN 200820059309U CN 201266833 Y CN201266833 Y CN 201266833Y
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- circuit
- frequency converter
- output end
- resistance
- earth
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Abstract
The utility model relates to a frequency converter output end ground short circuit protection on-line pre-detection circuit; the circuit is connected between a DC bus and the output end of a frequency inverter; each phase of the three-phase output end of the frequency inverter is connected with the same detecting resistance; one end of three resistances is connected in parallel and then in series with an output resistance R0 of the detecting circuit; and R0 is connected with a DC UL. In the frequency converter output end ground short circuit protection on-line pre-detection device, the voltage drop at two ends of the R0 in the frequency converter output end ground short circuit protection on-line pre-detection circuit is output to a voltage comparator, and the electric signal which is generated by the voltage comparator is separated by a photocoupler and then input to a single-chip microcomputer for processing. The loop only has minimal current, does not cause any influence to the safety of the power electronics device insulation gate bipolar transistor IGBT of the frequency converter nor further damage the electric motor; moreover, in a given measuring method, the circuit is simple, consists of resistors, and has very small power consumption and very low cost.
Description
Technical field
The utility model relates to circuit shorted to earth protection field, relates in particular to a kind of inverter output terminal shorted to earth protective circuit and device.
Background technology
Frequency converter is a kind of power electronic equipment, and its main circuit mainly is made of the power electronic device insulated gate bipolar transistor IGBT.To such an extent as to its load motor through regular meeting because motor makes moist, reasons such as mechanical friction overheated, coil cause motor insulation decline short circuit.Because motor housing ground connection, this will make inverter output terminal generation shorted to earth or insulation against ground resistance drop to outlier.In case frequency converter starts and will produce very big short circuit current to earth, the safety of the power device insulated gate bipolar transistor IGBT of frequency converter is brought threat, also can cause the further damage of motor.Fig. 1 shows being connected of frequency converter and motor.Motor is equivalent resistance Rx over the ground.Drop to very low or short circuit as this resistance, the power electronic device insulated gate bipolar transistor IGBT can flow through very big electric current after then frequency converter started.
Present frequency converter all has overcurrent or short-circuit protection circuit.Original guard method all is to start the back at frequency converter to detect output end current or dc bus current.If detect very big short circuit current, just protect, block the drive signal that adds to insulated gate bipolar transistor IGBT fast, report to the police simultaneously and demonstration.But because short circuit current is very big, and very big current-rising-rate is arranged
Even protect very soon, also can bring heavy current impact to insulated gate bipolar transistor IGBT, still have the possibility that insulated gate bipolar transistor IGBT and motor are further damaged.
In fact under many circumstances, motor if can detect after insulation descends or damages, and often is easy to repair (only need dry as damp motor).But burn in case flow through to cause behind the big electric current.So the protective circuit that this patent relates to not only can protect frequency converter also can protect motor.
At present general overcurrent or short-circuit protection adopt special-purpose Hall current instrument transformer, and cost is higher, and needs power supply.As adopt resistance measurement, because it is big to flow through electric current, power consumption is bigger.
Summary of the invention
Technical problem to be solved in the utility model provides a kind of inverter output terminal shorted to earth and protects online pre-detection circuit and device, and is not high enough with reliability in the solution prior art, circuit complexity, defect of high cost.Technical scheme
A kind of inverter output terminal shorted to earth is protected online pre-detection circuit, and this circuit is connected between dc bus and the inverter output terminal, and the three-phase output end of the frequency converter 2 identical detection resistance that whenever links is R
A, R
B, R
C, after three resistance one end parallel connections and testing circuit output resistance R
0Be in series R
0UL links with dc bus.
A kind of inverter output terminal shorted to earth is protected online pre-detection device, comprises testing circuit (1), voltage comparator (2), single-chip microcomputer (3), the R of testing circuit (1)
0The two ends pressure drop output to voltage comparator (2), voltage comparator (2) links to each other with single-chip microcomputer (3) by electric coupling.
Beneficial effect
The utility model is installed in the interior output loop of frequency converter, after the frequency converter energized, just monitors, detects the insulation against ground situation of frequency converter to load motor when starting as yet.Drop to below the critical value in case shorted to earth or insulation against ground resistance take place, just protect (showing fault, No starting).And under this detected state, have only minimum electric current, and can not produce any influence to the safety of the power electronic device insulated gate bipolar transistor IGBT of frequency converter, also can not produce further and damage motor.And the method for measurement circuit that provides is simple, is made of resistance, and power consumption is very little, and cost is very low.
Description of drawings
Fig. 1 is the demonstration frequency converter of prior art and the link circuit figure of motor;
Fig. 2 is a frequency converter shorted to earth pre-detection electric circuit inspection schematic diagram;
Fig. 3 protects online pre-detection installation drawing for the inverter output terminal shorted to earth.
Embodiment
Below in conjunction with specific embodiment, further set forth the utility model.Should be understood that these embodiment only to be used to the utility model is described and be not used in the restriction scope of the present utility model.Should be understood that in addition those skilled in the art can make various changes or modifications the present invention after the content of having read the utility model instruction, these equivalent form of values fall within the application's appended claims institute restricted portion equally.
Embodiment 1
As shown in the figure, a kind of inverter output terminal shorted to earth is protected online pre-detection circuit, and this circuit is connected between dc bus UL and the inverter output terminal, and the three-phase output end of the frequency converter identical detection resistance that whenever links is R
A, R
B, R
C, after three resistance one end parallel connections and testing circuit 1 output resistance R
0Be in series R
0UL links with dc bus, R wherein
0The two ends pressure drop output to voltage comparator 2, the signal of telecommunication that voltage comparator 2 produces handles 3 through photoelectric coupler isolation input single-chip microcomputer.
When the frequency converter energized but when not starting as yet (this moment, insulated gate bipolar transistor IGBT was not open-minded as yet); the phase line of electrical network is by frequency converter input side rectifier bridge, and------the inverter output terminal shorted to earth is protected online pre-detection circuit, and---inverter output terminal---motor (being equivalent insulation resistance)---ground wire forms path to dc bus UL.Insulation resistance (being Rx) as motor is very big, and then the electric current crossed of this loop stream is minimum, in resistance R
0On pressure drop minimum, i.e. testing circuit output voltage U
ShVery little, this is a normal condition.If the insulation resistance of motor drops to critical value following (it has been generally acknowledged that the Ω less than 0.5M), the electric current that flows through the loop increases, in resistance R
0On pressure drop also increase, the testing circuit output voltage increases.This is the shorted to earth malfunction.Owing to detect resistance R
AAnd R
0Resistance very big, even the motor shorted to earth, the electric current that flows through also is limited in very little value (being generally less than 10mA), can not cause the further damage of motor.And the power device insulated gate bipolar transistor IGBT is not open-minded as yet, can not be on the hazard yet; In case the load insulation against ground damages, R
0On pressure drop U
ShWill become big, this voltage signal input control circuit is judged, can report to the police, show, forbid that frequency converter starts, and reaches protective effect effectively.
R in the testing circuit
0On pressure drop U
ShSend into comparator, compare with predefined reference voltage, if the good U of frequency converter insulation against ground
ShLess than reference voltage, comparator is output as low level.If the frequency converter insulation against ground damages, then U
ShBe higher than reference voltage, comparator is output as high level, handles through photoelectric coupler isolation input single-chip microcomputer, and scm software is designed in the frequency converter energized but when not starting, and this input is detected and judges.As have short-circuit signal, and then block response to enabling signal, block frequency converter output, report to the police and the fault demonstration.
The selection of resistance value:
(1) correctly selects resistance.Generally when inverter load insulation resistance during greater than 0.5M Ω, R
0On pressure drop U
ShLess than 4V.When the load insulation resistance less than 0.5M Ω, R
0On pressure drop U
ShGreater than 4V.The resistance computational methods are as follows:
During the critical condition of power taking machine insulation damages
I
cr＝U
m/(R
J+R
A+R
0) U
sh＝I
crR
0
Wherein:
I
Cr: the electric current that flows through electrical machine insulation resistance during critical condition that electrical machine insulation damages.Generally get 0.5-1mA.When motor over the ground during dead short circuit, electric current is by R
AAnd R
0Current limliting is at 1-2mA.
U
m: electrical network phase voltage peak value.Because testing circuit is an instantaneous operation, so calculate with voltage peak.When three-phase 380V, be phase voltage peak value 220
V, i.e. 311V.
U
Sh: the testing circuit output voltage.Determine according to follow-up protective circuit threshold values, for example get 4V.
R
J: during critical condition that electrical machine insulation damages, the insulation resistance of load motor is generally 0.5M Ω.
R
A: the resistance of testing circuit one phase.
Can calculate by above-mentioned relation: R
A=U
m/ I
Cr-R
J-R
0)
R
0: the testing circuit output resistance.
Can calculate: R
0=U
Sh/ I
Cr
As stated above, R in the frequency converter of three-phase 380V power supply
AAvailable 300K Ω, R
0Use 5K Ω.
(2) be used for connecting AC power, but detect when not starting as yet at frequency converter.Detect decision circuitry as shown in Figure 3, the testing circuit output voltage U
ShSend into the back input single-chip microcomputer processing of testing circuit and preset reference voltage ratio, if the testing circuit output voltage U
ShLess than fiducial value, expression load insulation against ground is normal.Then allow frequency converter to start.If testing circuit output voltage U
ShGreater than fiducial value, represent that then the load insulation against ground damages, or shorted to earth.Forbid that frequency converter starts, and report to the police.
(4) busbar voltage can detect resistance upper reaches overcurrent by the insulated gate bipolar transistor IGBT of conducting after frequency converter started.So no longer adopt this detection signal after starting.
Claims (2)
1. an inverter output terminal shorted to earth is protected online pre-detection circuit, it is characterized in that: this circuit is connected between dc bus and the inverter output terminal, and the three-phase output end of the frequency converter identical detection resistance that whenever links is R
A, R
B, R
C, after three resistance one end parallel connections and testing circuit output resistance R
0Be in series R
0UL links with dc bus.
2. an inverter output terminal shorted to earth is protected online pre-detection device, it is characterized in that: comprise testing circuit (1), voltage comparator (2), the single-chip microcomputer (3) of claim 1, the R of testing circuit (1)
0The two ends pressure drop output to voltage comparator (2), voltage comparator (2) links to each other with single-chip microcomputer (3) by electric coupling.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNU2008200593098U CN201266833Y (en) | 2008-06-03 | 2008-06-03 | On-line pre-detection circuit and device for protection of shorted to earth of frequency changer output end |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNU2008200593098U CN201266833Y (en) | 2008-06-03 | 2008-06-03 | On-line pre-detection circuit and device for protection of shorted to earth of frequency changer output end |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN201266833Y true CN201266833Y (en) | 2009-07-01 |
Family
ID=40833202
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNU2008200593098U Expired - Fee Related CN201266833Y (en) | 2008-06-03 | 2008-06-03 | On-line pre-detection circuit and device for protection of shorted to earth of frequency changer output end |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN201266833Y (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103076489A (en) * | 2012-12-12 | 2013-05-01 | 安徽颐和新能源科技股份有限公司 | Instantaneous overcurrent detecting circuit of optical fiber communication cascade type high-voltage inverter |
| CN103176072A (en) * | 2011-12-26 | 2013-06-26 | 上海大郡动力控制技术有限公司 | Electric vehicle busbar insulation detection device and application method thereof |
| CN105021936A (en) * | 2014-04-25 | 2015-11-04 | 青岛海信日立空调系统有限公司 | Method and electric device for detecting electric leakage |
| CN110308391A (en) * | 2019-06-07 | 2019-10-08 | 横店集团英洛华电气有限公司 | A kind of low cost current of electric Acquisition Circuit and its acquisition method |
-
2008
- 2008-06-03 CN CNU2008200593098U patent/CN201266833Y/en not_active Expired - Fee Related
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103176072A (en) * | 2011-12-26 | 2013-06-26 | 上海大郡动力控制技术有限公司 | Electric vehicle busbar insulation detection device and application method thereof |
| CN103076489A (en) * | 2012-12-12 | 2013-05-01 | 安徽颐和新能源科技股份有限公司 | Instantaneous overcurrent detecting circuit of optical fiber communication cascade type high-voltage inverter |
| CN103076489B (en) * | 2012-12-12 | 2016-04-06 | 安徽颐和新能源科技股份有限公司 | Optical-fibre communications cascaded high-voltage frequency converter instantaneous overcurrent testing circuit |
| CN105021936A (en) * | 2014-04-25 | 2015-11-04 | 青岛海信日立空调系统有限公司 | Method and electric device for detecting electric leakage |
| CN105021936B (en) * | 2014-04-25 | 2018-02-13 | 青岛海信日立空调系统有限公司 | A kind of method and electric equipment for detecting electrical leakage |
| CN110308391A (en) * | 2019-06-07 | 2019-10-08 | 横店集团英洛华电气有限公司 | A kind of low cost current of electric Acquisition Circuit and its acquisition method |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| C17 | Cessation of patent right | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20090701 Termination date: 20120603 |