CN105301409A - Grounding fault detection and alarm circuit of frequency converter - Google Patents
Grounding fault detection and alarm circuit of frequency converter Download PDFInfo
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- CN105301409A CN105301409A CN201510791946.9A CN201510791946A CN105301409A CN 105301409 A CN105301409 A CN 105301409A CN 201510791946 A CN201510791946 A CN 201510791946A CN 105301409 A CN105301409 A CN 105301409A
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Abstract
The invention discloses a grounding fault detection and alarm circuit of a frequency converter. The detection and alarm circuit comprises a fault detection circuit and an alarm signal generating circuit. The fault detection circuit comprises a detection resistor. One end of the detection resistor is connected to the ground and the other end is connected with one end of a first capacitor, one end of a second capacitor and the signal input end of the alarm signal generating circuit. The other end of the first capacitor is connected with the negative pole of a first current-limiting diode and the positive pole of a second current-limiting diode. The positive pole of the first current-limiting diode is connected with a P pole via a first resistor. The negative pole of the second current-limiting diode is connected with the P pole via a second resistor. The other end of the second capacitor is connected with the negative pole of a third current-limiting diode and the positive pole of a fourth current-limiting diode. The positive pole of the third current-limiting diode is connected with an N pole via a third resistor. The negative pole of the fourth current-limiting diode is connected with the N pole via a fourth resistor. The detection and alarm circuit is small in size, highly integrated and low in cost.
Description
Technical field
The present invention relates to warning circuit, specifically a kind of Earth Fault Detection warning circuit of frequency converter.
Background technology
Along with improving constantly of electric propulsion system power grade, system reliability and maintainable requirement more and more harshness.In many power electronic equipments, the security relationship of frequency converter is to the overall situation of security of system.The DC bus of frequency converter is made up of jumbo electric capacity, if there is accident, will cause irremediable damage to equipment.When earth fault extremely surprisingly occurs for the P pole of frequency converter or N, be equivalent to the indirect less resistance on P pole or N pole and ground, this resistance is much smaller than stake resistance (ten mega-ohms) over the ground under normal circumstances.This earth fault may cause the harm such as DC voltage decline, secondary circuit damage, major loop open circuit.Usually, people can design a circuit judges earth fault generation by detecting ohmically change in voltage.Detect under normal circumstances on resistance and do not have voltage, when earth fault occurs, can form a loop, the electric current in loop flows through and detects resistance generation voltage, produces alerting signal by the subsequent process circuit detecting voltage.
In the prior art, general frequency converter failure testing circuit schematic diagram as shown in Figure 1, is divided into testing circuit and warning circuit, selecting MIU10 as being current measurement amplifier, being arranged to-90mV ~ 90mV voltage amplification to-5V ~ 5V in prior art.Circuit theory is as follows: under normal circumstances, between P-N, 1500V busbar voltage is mounted with identical resistance R1 and R2 of two resistances.Because the resistance of resistance R1 with R2 is identical, therefore two ohmically voltages are 750V, and now detecting resistance Rs two ends does not have voltage; When earth fault occurs in frequency converter P pole, in suitable Fig. 1, S closes, and is equivalent to indirect 1 the small resistor R3 on P pole and ground.Now, stake resistance R3 is in parallel with R1 after connecting with detection resistance Rs, then connects with R2, resistance Rs has electric current to flow through, and is steady state value.Therefore just earth fault can be detected by detecting the change of Rs both end voltage.Because the function of the left and right circuit of testing circuit in Fig. 1 is symmetrical, in like manner known, when there is earth fault in N pole, there is same process, difference is, there is earth fault and N pole and earth fault occur to detect the electric current on resistance Rs contrary in P pole, causes Rs both end voltage just may be or be negative, so PLC must judge window voltage.Be connected in parallel on the voltage that the diode detected on resistance Rs can limit MIU10 input end in Fig. 1, make Rs both end voltage can not exceed the forward voltage drop of diode, play the effect of protection.Detect voltage U s and pass to PLC after MIU10 amplifies, can carry out reporting to the police or protecting after detection voltage exceeds the voltage range of setting.
In technique scheme, testing circuit mainly bears DC bus-bar voltage by resistance, as Fig. 1, when there is the extreme fault of P pole shorted to earth or N pole shorted to earth, resistance R2 or R1 will bear whole DC bus-bar voltage, power consumption is comparatively large, then to select resistance R1 and the requirement of R2 power index higher, often reach more than tens watts.Meanwhile, have higher requirement to the voltage withstand class of resistance, and this kind of resistance volume can be comparatively large, and MIU10 can not be used for pcb board installation.Therefore, the defect of this kind of testing circuit scheme is comparatively large for accounting for volume, and be not suitable for pcb board design occasion, in addition, cost is also relatively high.
Summary of the invention
Object of the present invention is exactly will provide that a kind of volume is little, integrated level is high and the Earth Fault Detection warning circuit of the frequency converter that cost is low.
For achieving the above object, the Earth Fault Detection warning circuit of the frequency converter designed by the present invention, comprising the failure detector circuit that can produce fault detection voltage and can detecting voltage transitions is that the alerting signal of alerting signal produces circuit; Its special character is: described failure detector circuit comprises detection resistance, described detection resistance one end ground connection, and the other end is the output terminal of failure detector circuit, connects one end of one end of the first electric capacity, the second electric capacity respectively; The other end of described first electric capacity is connected with the positive pole of the second Current Limiting Diodes with the negative pole of the first Current Limiting Diodes sky respectively; The positive pole of described first Current Limiting Diodes is extremely connected with P by the first resistance, and the negative pole of described second current limliting pole pipe is extremely connected with P by the second resistance; The other end of described second electric capacity is connected with the positive pole of the 4th Current Limiting Diodes with the negative pole of the 3rd Current Limiting Diodes respectively; The positive pole of described 3rd Current Limiting Diodes is extremely connected with N by the 3rd resistance, and the negative pole of described 4th Current Limiting Diodes is extremely connected with N by the 4th resistance; Described alerting signal produces the input end of circuit and is connected with the output terminal of failure detector circuit.
Further, described alerting signal generation main circuit will comprise diode, comparator circuit and signaling conversion circuit; Described diode and detection resistor coupled in parallel, one end is connected with the output terminal of failure detector circuit, other end ground connection; The input end of described comparator circuit is connected with one end of diode, and output terminal is connected with the input end of signaling conversion circuit; Described diode is used for preventing failure detector circuit abnormal and having an impact to comparator circuit and change-over circuit; Detection photovoltaic conversion is that comparison signal sends signaling conversion circuit to by described comparator circuit; Comparison signal is converted to alerting signal by described signaling conversion circuit.
Further, described first resistance, the second resistance, the 3rd resistance are identical with the resistance of the 4th resistance; Described first Current Limiting Diodes, the second Current Limiting Diodes, the 3rd Current Limiting Diodes are identical with the 4th Current Limiting Diodes.
Again further, described comparator circuit comprises chip MC33161, the 5th resistance, the 6th resistance, the 7th resistance and the 8th resistance; 1 pin of described chip MC33161 connects one end of the 6th resistance and 7 pin of chip MC33161 respectively, and the other end of described 6th resistance is connected with one end of diode by the 5th resistance, is connected again with 2 pin of chip MC33161 simultaneously; 3 pin of described chip MC33161 are connected with one end of diode by the 8th resistance, simultaneously again by the 7th resistance eutral grounding; The 4 pin ground connection of described chip MC33161; 5 pin and 6 pin of described chip MC33161 are connected the input end of change-over circuit simultaneously, and 8 pin of described chip are connected with power supply.
Also further, connect change-over circuit described in and comprise chip SN55451B, the 9th resistance, the tenth resistance, the 11 resistance, the 12 resistance, the 3rd diode, light emitting diode and the 3rd electric capacity; 7 pin of described chip SN55451B are connected with the output terminal of comparator circuit, are connected by the 9th resistance with power supply simultaneously; The 4 pin ground connection of described chip SN55451B, 6 pin of described chip SN55451B are connected with power supply by the tenth resistance; 8 pin of described chip SN55451B connect power supply and respectively by the 3rd capacity earth, 5 pin of described SN55451B are connected with power supply by the 11 resistance, connect the positive pole of the 3rd diode and the negative pole of light emitting diode respectively again simultaneously, the described negative pole of the 3rd diode and the positive pole of light emitting diode are connected one end of the 12 resistance simultaneously, and the other end of described 12 resistance connects power supply.
Again further, described diode comprises the first diode group and the second diode group, in the first diode group, there is multiple first diode to connect on identical forward direction, and have multiple second diode to connect on the forward direction contrary with the first diode forward direction in the second diode group, the first diode group is in parallel with the second diode group to be made to point to different directions.
In technique scheme, described first diode has four, and described second diode has four, and described first diode and the second diode are 1N914ATR diode.
In technique scheme, the resistance of described first resistance, the second resistance, the 3rd resistance and the 4th resistance is 220k Ω, and power is 3W; It is the 1N4007 type diode of 1000V that peak reverse of selecting described first Current Limiting Diodes, the second Current Limiting Diodes, the 3rd Current Limiting Diodes and the 4th Current Limiting Diodes repeats voltage; The resistance of described detection resistance is 1.1k Ω.
In technique scheme, the resistance of described 5th resistance is 243k Ω, and the resistance of described 6th resistance is 100k Ω, and the resistance of described 7th resistance is 100k Ω, and the resistance of described 8th resistance (R8) is 56.2k Ω.
In technique scheme, described 3rd diode is 1N4148 diode.
The present invention is judging the generation of earth fault by detecting ohmically detection change in voltage, then detection voltage is converted into comparison signal through comparing, then comparison signal is converted to alerting signal.Improve traditional ground fault detection circuit of bearing DC bus-bar voltage with large resistance, utilize withstand voltage high electric capacity to bear DC bus-bar voltage, can detection of ground faults effectively.
Technique effect of the present invention is embodied in:
(1) volume is little.The resistor power index that the present invention selects is little, and comparing with power of the prior art is the resistance of more than tens watts, and the power of resistance of the present invention is generally several watts.This makes volume also corresponding reduction.
(2) integrated level is high.Because resistance volume used is little, facilitate integrated, and detection limit is without the need to amplifying, and can not be used for the device of pcb board installation without the need to current amplifier MIU10 and so on.
(3) cost is low.Select the resistance that power index is little, reduce cost, and the cost of chip MC33161 and chip SN55451B is low, further reduces cost.
(4) stable and reliable for performance.The chip MC33161 that the present invention selects and chip SN55451B is conventional standard chips, stable performance, can make whole circuit reliability service.
Accompanying drawing explanation
Fig. 1 is the frequency converter failure testing circuit schematic diagram of prior art.
Fig. 2 is failure detector circuit schematic diagram of the present invention.
Fig. 3 is the equivalent circuit theory figure of the present invention's failure detector circuit when breaking down.
Fig. 4 is that alerting signal of the present invention produces circuit theory diagrams.
Fig. 5 is the positive negative overpressure Cleaning Principle figure of chip MC33161.
Embodiment
Describe performance of the present invention in detail below in conjunction with accompanying drawing, but it does not form limitation of the invention, only illustrate.Simultaneously by illustrating, advantage of the present invention will become clearly and easy understand.
Failure detector circuit schematic diagram as shown in Figure 2, detects resistance Rs one end ground connection, and the other end connects the signal input part that one end of the first electric capacity C1, one end of the second electric capacity C2 and alerting signal produce circuit respectively.The other end of the first electric capacity C1 is connected with the positive pole of the second Current Limiting Diodes D2 with the negative pole of the first Current Limiting Diodes D1 respectively.The positive pole of the first Current Limiting Diodes D1 is extremely connected by the first resistance R1 and P, and the negative pole of the second current limliting pole pipe D2 is extremely connected by the second resistance R2 and P.The other end of the second electric capacity C2 is connected with the positive pole of the 4th Current Limiting Diodes D4 with the negative pole of the 3rd Current Limiting Diodes D3 respectively.The positive pole of the 3rd Current Limiting Diodes D3 is extremely connected by the 3rd resistance R3 and N, and the negative pole of the 4th Current Limiting Diodes D4 is extremely connected by the 4th resistance R4 and N.
The principle of failure detector circuit is as follows: under normal circumstances, and between P-N, 1000V busbar voltage is charged to the first electric capacity C1 and the second electric capacity C2 by the first resistance R1, the first current limliting D1, the 4th Current Limiting Diodes D4 and the 4th resistance R4 path.After charging terminates, ignore diode forward pressure drop, the voltage at the first electric capacity C1 and the second electric capacity C2 two ends is all about 500V.Now detect resistance Rs two ends and there is no voltage.When there is earth fault in frequency converter P pole, in suitable Fig. 2, S closes, at indirect 1 small resistor R5 on P pole and ground, now, the equivalent electrical circuit of Fig. 2 circuit as shown in Figure 3, have two paths, by stake resistance R5, detection resistance Rs, the 4th Current Limiting Diodes D4 and the 4th path, resistance R4 place, the second electric capacity C2 is charged between P-N.First electric capacity C1 is discharged with detection path, resistance Rs place by the second Current Limiting Diodes D2, the second resistance R2, the 4th resistance R5, therefore just can detect earth fault by detecting the change of resistance Rs both end voltage.Along with the process that the second electric capacity C2 charges and the first electric capacity C1 discharges, flow through the electric current detecting resistance Rs to reduce gradually, its both end voltage also reduces thereupon, after the second electric capacity C2 charges and to discharge with the first electric capacity C1 and terminate, second electric capacity C2 voltage is 1000V, and the first electric capacity C1 voltage is 0V.Now detecting resistance Rs both end voltage is just.Because the function of the left and right circuit of failure detector circuit in Fig. 2 is symmetrical, in like manner known, when there is earth fault in N pole, there is similar process, when there is earth fault unlike, N pole, the first electric capacity C1 carries out charging, the second electric capacity C2 discharges, and the direction of current flow through when earth fault occurs for the electric current that detects resistance Rs and N pole is contrary, now, it is negative for detecting resistance Rs both end voltage.
For Fig. 3 circuit, there is the circuit equation following (ignoring the tube voltage drop of diode) of moment in P pole ground fault:
Through type (1) can solve detection voltage U s and be shown below:
Because the first resistance R2 is identical with the 4th resistance R4 resistance, the first electric capacity C1 is identical with the second electric capacity C2, and therefore, the second resistance R2 is the same with the curent change trend on the 4th resistance R4.
First resistance R1, the second resistance R2, the 3rd resistance R3 and the 4th resistance R4 resistance mainly play metering function in capacitor charge and discharge process, and bear half DC bus-bar voltage at short notice when earth fault occurs.When P pole or N pole are short-circuited fault, the voltage that resistance in circuit bears is maximum, according to short circuit extreme case design resistance parameter, the first resistance R1, the second resistance R2, the 3rd resistance R3 and the 4th resistance R4 all choose 220k Ω/3W resistance of PR03 series here.There is moment in short circuit extreme case, the maximum reverse peak value that first Current Limiting Diodes D1 and the 3rd Current Limiting Diodes D3 bears is 500V, here the first Current Limiting Diodes D1, the second Current Limiting Diodes D2, the 3rd Current Limiting Diodes D3 and the 4th Current Limiting Diodes D4 all select peak reverse to repeat 1N4007 diode that voltage is 1000V.With reference to the threshold value of earth fault setting in Fig. 1 prior art Earth Fault Detection, in this circuit, the threshold value of earth fault setting is 130k Ω, namely as stake resistance R5≤130k Ω over the ground, assert frequency converter generation earth fault.Conveniently subsequent conditioning circuit is to the process detecting voltage, detects voltage design upon the occurrence of a ground fault at 2 ~ 5V, therefore chooses and detects resistance Rs=1.1k Ω.Parameter being substituted into formula (2) can abbreviation be:
As stake resistance R5=130k Ω, detect voltage U s=2.28V; When stake resistance R5=0 (i.e. ground short circuit), detect voltage U s=4.95V.Therefore, when detecting voltage U s>2.28V, show that earth fault occurs in P pole.In like manner, when detecting voltage U s<-2.28V, show that earth fault occurs in N pole.
Alerting signal produces circuit and processes detection voltage, produces alerting signal, passes to host computer.The alerting signal of design produces circuit as shown in Figure 4.In order to prevent front end observation circuit fault on the impact of back-end circuit; protect at detection voltage U s two terminating diode; because detection voltage U s may be may be just negative, and consider to clamp the voltage at about 2.5V, therefore on detection resistance Rs, be parallel with diode.Two groups of first diode groups parallel with one another and the second diode group is comprised at diode, in the first diode group, be in series with the first diode D5 that four forward directions are identical, in the second diode group, be in series with the second diode D6 that four forward directions are contrary with the second diode group.First diode D5 and the second diode D6 is 1N914ATR diode.
1 pin of chip MC33161 connects one end of the 6th resistance R6 and 7 pin of chip MC33161 respectively, and the other end of the 6th resistance R6 is connected with the signal input part that alerting signal produces circuit by the 5th resistance R5, is connected again with 2 pin of chip MC33161 simultaneously.3 pin of chip MC33161 are connected with the signal input part that alerting signal produces circuit by the 8th resistance R8, simultaneously again by the 7th resistance R7 ground connection.The 4 pin ground connection of chip MC33161,5 pin and 6 pin of chip MC33161 are connected one end of the 9th resistance R9 simultaneously, and the other end of the 9th resistance R9 is connected with power vd D.8 pin of chip MC33161 are connected with power vd D.
The 4 pin ground connection of chip SN55451B, its 7 pin is connected with one end of the 9th resistance R9, its 6 pin is connected with power vd D by the tenth resistance R10, its 8 pin connects power vd D and respectively by the 3rd electric capacity C3 ground connection, 5 pin of SN55451B are connected with power vd D by the 11 resistance R11, connect the positive pole of the 3rd diode D7 and the negative pole of light emitting diode D8 respectively again simultaneously, the described negative pole of the 3rd diode D7 and the positive pole of light emitting diode D8 are connected one end of the 12 resistance R12 simultaneously, and the other end of described 12 resistance R12 connects power vd D.
Chip MC33161 in Fig. 4 is general voltage monitoring chip, utilizes this chip to realize positive overvoltage and negative overpressure monitoring here.The positive overvoltage of MC33161 and negative overpressure monitoring voltage principle are as shown in Figure 5.According to the databook of MC33161,3 pin inputs are set to positive overvoltage monitoring, the limit value V in Fig. 5
1with V
2can be tried to achieve by following formula (4) and formula (5), 2 pin inputs are set to negative overpressure monitoring, limit value V
3with V
4can be tried to achieve by following formula (6) and formula (7):
Wherein, V
th1with V
th2be the threshold voltage of chip MC33161 internal comparator, be 1.27V, V
h1with V
h2be the hysteresis voltage of chip MC33161 inside, be 0.025V.V
reffor being chip MC33161 internal reference voltage, be 2.54V.
The alerting signal of Fig. 4 produces in circuit gets the 8th resistance R8=56.2k Ω, and the 7th resistance R7=100k Ω, calculates known by formula (5), positive overvoltage monitoring threshold V
2=1.98V, when detecting voltage U s and being greater than 1.98V, 5 pin of chip MC33161 and 6 pin output low levels; Formula (6) calculates V
1=1.94V, when detecting (hysteretic characteristic of MC33161) when voltage U s is less than 1.94V, 5 pin of chip MC33161 and 6 pin export high level.Get the 5th resistance R5=243k Ω in circuit, the 6th resistance R6=100k Ω, calculate known by formula (7), negative overpressure monitoring threshold is about V
4=-1.9V, when Us is less than-1.9V, 5 pin of chip MC33161 and 6 pin output low levels; Formula (6) calculates V
3=-1.82V is (hysteretic characteristic of MC33161) when Us is greater than-1.82V, and 5 pin of chip MC33161 and 6 pin export high level.
Chip SN55451B in Fig. 4 is optical fiber driving chip (comprising two and door), here only with 1 passage, its 6 pin is set to permanent high by pull-up resistor, upon the occurrence of a ground fault, the 7 pin input low levels of chip SN55451B when i.e. 5, the 6 pin output low level of MC33161 (), its 5 pin output low level, optical fiber head is luminous, passes to host computer in this, as alerting signal.
9th resistance R9, the tenth resistance R10 are identical with the resistance of the 11 resistance R11, are 1k Ω.3rd diode D7 is 1N4148 diode.
Alerting signal of the present invention produces circuit can also other way of realization, and the structure of all failure detector circuits is consistent with the present invention, all drops in the protection domain of this patent requirement.
Claims (10)
1. an Earth Fault Detection warning circuit for frequency converter, comprising the failure detector circuit that can generate fault detection voltage and can detecting voltage transitions is that the alerting signal of alerting signal produces circuit; It is characterized in that:
Described failure detector circuit comprises detection resistance (Rs), described detection resistance (Rs) one end ground connection, the other end is the output terminal of failure detector circuit, connects one end of one end of the first electric capacity (C1), the second electric capacity (C2) respectively;
The other end of described first electric capacity (C1) is connected with the positive pole of the second Current Limiting Diodes (D2) with the negative pole of the first Current Limiting Diodes (D1) respectively; The positive pole of described first Current Limiting Diodes (D1) is extremely connected with P by the first resistance (R1), and the negative pole of described second current limliting pole pipe (D2) is extremely connected with P by the second resistance (R2);
The other end of described second electric capacity (C2) is connected with the positive pole of the 4th Current Limiting Diodes (D4) with the negative pole of the 3rd Current Limiting Diodes (D3) respectively; The positive pole of described 3rd Current Limiting Diodes (D3) is extremely connected with N by the 3rd resistance (R3), and the negative pole of described 4th Current Limiting Diodes (D4) is extremely connected with N by the 4th resistance (R4);
Described alerting signal produces the input end of circuit and is connected with the output terminal of failure detector circuit.
2. the Earth Fault Detection warning circuit of frequency converter according to claim 1, is characterized in that: described alerting signal produces main circuit will comprise diode (1), comparator circuit (2) and signaling conversion circuit (3);
Described diode (1) is in parallel with detection resistance (Rs), and one end is connected with the output terminal of failure detector circuit, other end ground connection;
The input end of described comparator circuit (2) is connected with one end of diode (1), and output terminal is connected with the input end of signaling conversion circuit (3);
Described diode (1) has an impact to comparator circuit (2) and change-over circuit (3) for preventing failure detector circuit abnormal;
Detection photovoltaic conversion is that comparison signal sends signaling conversion circuit (3) to by described comparator circuit (2);
Comparison signal is converted to alerting signal by described signaling conversion circuit (3).
3. the Earth Fault Detection warning circuit of frequency converter according to claim 1, is characterized in that: described first resistance (R1), the second resistance (R2), the 3rd resistance (R3) are identical with the resistance of the 4th resistance (R4); Described first Current Limiting Diodes (D1), the second Current Limiting Diodes (D2), the 3rd Current Limiting Diodes (D3) are identical with the 4th Current Limiting Diodes (D4).
4. the Earth Fault Detection warning circuit of frequency converter according to claim 2, is characterized in that: described comparator circuit (2) comprises chip MC33161, the 5th resistance (R5), the 6th resistance (R6), the 7th resistance (R7) and the 8th resistance (R8);
1 pin of described chip MC33161 connects one end of the 6th resistance (R6) and 7 pin of chip MC33161 respectively, the other end of described 6th resistance (R6) is connected with one end of diode (1) by the 5th resistance (R5), is connected again with 2 pin of chip MC33161 simultaneously; 3 pin of described chip MC33161 are connected with one end of diode (1) by the 8th resistance (R8), simultaneously again by the 7th resistance (R7) ground connection; The 4 pin ground connection of described chip MC33161; 5 pin and 6 pin of described chip MC33161 are connected the input end of change-over circuit (3) simultaneously, and 8 pin of described chip are connected with power supply (VDD).
5. the Earth Fault Detection warning circuit of frequency converter according to claim 2, is characterized in that: described in connect change-over circuit (3) and comprise chip SN55451B, the 9th resistance (R9), the tenth resistance (R10), the 11 resistance (R11), the 12 resistance (R12), the 3rd diode (D7), light emitting diode (D8) and the 3rd electric capacity (C3);
7 pin of described chip SN55451B are connected with the output terminal of comparator circuit (2), are connected by the 9th resistance (R9) with power supply (VDD) simultaneously; The 4 pin ground connection of described chip SN55451B, 6 pin of described chip SN55451B are connected with power supply (VDD) by the tenth resistance (R10); 8 pin of described chip SN55451B connect power supply (VDD) respectively and pass through the 3rd electric capacity (C3) ground connection, 5 pin of described SN55451B are connected with power supply (VDD) by the 11 resistance (R11), connect the positive pole of the 3rd diode (D7) and the negative pole of light emitting diode (D8) respectively again simultaneously, negative pole and the positive pole of light emitting diode (D8) of described 3rd diode (D7) are connected one end of the 12 resistance (R12) simultaneously, and the other end of described 12 resistance (R12) connects power supply (VDD).
6. the Earth Fault Detection warning circuit of frequency converter according to claim 2, it is characterized in that: described diode (1) comprises the first diode group and the second diode group, in the first diode group, there is multiple first diode (D5) to connect on identical forward direction, and have multiple second diode (D6) to connect on the forward direction contrary with the first diode (D5) forward direction in the second diode group, the first diode group is in parallel with the second diode group to be made to point to different directions.
7. the Earth Fault Detection warning circuit of frequency converter according to claim 6, it is characterized in that: described first diode (D5) has four, described second diode (D6) has four, and described first diode (D5) and the second diode (D6) are 1N914ATR diode.
8. the Earth Fault Detection warning circuit of frequency converter according to claim 3, it is characterized in that: the resistance of described first resistance (R1), the second resistance (R2), the 3rd resistance (R3) and the 4th resistance (R4) is 220k Ω, and power is 3W; It is the 1N4007 type diode of 1000V that peak reverse of selecting described first Current Limiting Diodes (D1), the second Current Limiting Diodes (D2), the 3rd Current Limiting Diodes (D3) and the 4th Current Limiting Diodes (D4) repeats voltage; The resistance of described detection resistance (Rs) is 1.1k Ω.
9. the Earth Fault Detection warning circuit of frequency converter according to claim 4, it is characterized in that: the resistance of described 5th resistance (R5) is 243k Ω, the resistance of described 6th resistance (R6) is 100k Ω, the resistance of described 7th resistance (R7) is 100k Ω, and the resistance of described 8th resistance (R8) is 56.2k Ω.
10. the Earth Fault Detection warning circuit of frequency converter according to claim 7, is characterized in that: described 3rd diode (D7) is 1N4148 diode.
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Cited By (2)
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| CN107191980A (en) * | 2017-06-20 | 2017-09-22 | 广东美的厨房电器制造有限公司 | The determination methods and frequency-conversion microwave oven of frequency-conversion microwave oven state of ground wire |
| CN112881940A (en) * | 2019-11-14 | 2021-06-01 | 华为技术有限公司 | Grounding state detection circuit, electrical system and grounding state detection method thereof |
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| CN105301409B (en) | 2018-08-14 |
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