CN105301409B - The Earth Fault Detection warning circuit of frequency converter - Google Patents

The Earth Fault Detection warning circuit of frequency converter Download PDF

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CN105301409B
CN105301409B CN201510791946.9A CN201510791946A CN105301409B CN 105301409 B CN105301409 B CN 105301409B CN 201510791946 A CN201510791946 A CN 201510791946A CN 105301409 B CN105301409 B CN 105301409B
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resistance
circuit
diode
current limiting
fault detection
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CN105301409A (en
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艾胜
任强
曾启帆
孙驰
胡亮灯
陈德鹏
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Naval University of Engineering PLA
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Abstract

The invention discloses a kind of Earth Fault Detection warning circuits of frequency converter, including failure fault detection circuit and alarm signal generation circuit;Fault detection circuit includes detection resistance, and detection resistance one end ground connection, the other end is separately connected the signal input part of one end of the first capacitance, one end of the second capacitance and alarm signal generation circuit;The other end of first capacitance is connected with the anode of the cathode of the first Current Limiting Diodes and the second Current Limiting Diodes respectively;The anode of first Current Limiting Diodes is extremely connected by first resistor with P, and the cathode of the second current limliting pole pipe is extremely connected by second resistance with P;The other end of second capacitance is connected with the anode of the cathode of third Current Limiting Diodes and the 4th Current Limiting Diodes respectively;The anode of third Current Limiting Diodes is extremely connected by 3rd resistor with N, and the cathode of the 4th Current Limiting Diodes is extremely connected by the 4th resistance with N.The present invention is small, and integrated level is high and at low cost.

Description

The Earth Fault Detection warning circuit of frequency converter
Technical field
The present invention relates to warning circuit, the Earth Fault Detection warning circuit of specifically a kind of frequency converter.
Background technology
With the continuous improvement of electric propulsion system power grade, system reliability and maintainable requirement are more and more severe It carves.In many power electronic equipments, the overall situation of the security relationship of frequency converter to system safety.The DC bus of frequency converter is by big The capacitance of capacity forms, and if there is accident, irremediable damage will be caused to equipment.The poles P of frequency converter or N are extremely surprisingly sent out When raw earth fault, it is equivalent to the indirect smaller resistance on the poles P or the poles N and ground, this resistance is much smaller than normally In the case of ground resistance (ten mega-ohms) over the ground.This earth fault may cause DC voltage to decline, secondary circuit damages, main The harm such as loop open circuit.Usually, people can design a circuit by the voltage change in detection resistance to judge ground connection event The generation of barrier.There is no voltage in detection resistance under normal circumstances, when earth fault occurs, a circuit, circuit can be formed In electric current flow through detection resistance and generate voltage, the subsequent process circuit by detecting voltage generates alarm signal.
In the prior art, general frequency converter failure detection circuit schematic diagram is as shown in Figure 1, be divided into detection circuit and report Alert circuit, it is current measurement amplifier to select MIU10 to be used as in the prior art, be arranged to by -90mV~90mV voltage amplifications to - 5V~5V.Circuit theory is as follows:Under normal circumstances, there are two the identical resistance of resistance value for mounting in 1500V busbar voltages between P-N R1 and R2.Since the resistance value of resistance R1 and R2 is identical, two ohmically voltages are 750V, at this time detection resistance Rs two Hold no voltage;When earth fault occurs for the poles frequency converter P, S is closed in suitable Fig. 1, and is equivalent to indirectly with ground in the poles P 1 low resistance R3.At this point, ground resistance R3 is in parallel with R1 after connecting with detection resistance Rs, then connects with R2, have on resistance Rs Electric current flows through, and is steady state value.Therefore earth fault can be detected by detecting the variation of Rs both end voltages.Due in Fig. 1 The function of the left and right circuit of detection circuit is symmetrical, similarly it is found that when earth fault occurs for the poles N, has same process, no It is that the poles P occur earth fault and electric current of the earth fault on detection resistance Rs occurs on the contrary, leading to the both ends Rs with the poles N with place Voltage may be just or be negative, so PLC must judge window voltage.It is connected in parallel in Fig. 1 on detection resistance Rs Diode can limit the voltage of MIU10 input terminals, and Rs both end voltages is made not exceed the forward voltage drop of diode, play protection Effect.Detection voltage Us passes to PLC after MIU10 amplifies, can be into after detecting voltage range of the voltage beyond setting Row alarm or protection.
In the above-mentioned technical solutions, detection circuit mainly bears DC bus-bar voltage, such as Fig. 1 by resistance, works as hair The raw poles P shorted to earth either the extreme failure of the poles N shorted to earth when resistance R2 or R1 to bear entire DC bus-bar voltage, Power consumption is larger, then to selecting resistance R1 and R2 power index more demanding, often reaches tens watts or more.Meanwhile to resistance Stress levels have higher requirement, and this kind of resistance volume can be larger, and MIU10 can not be used for pcb board installation.Therefore, The defect of such detection circuit scheme is that account for volume larger, is not suitable for pcb board design occasion, in addition, cost is also relatively It is high.
Invention content
Present invention aim to provide, a kind of small, integrated level is high and the earth fault of frequency converter at low cost Detect warning circuit.
To achieve the above object, the Earth Fault Detection warning circuit of the frequency converter designed by the present invention, including can generate The fault detection circuit of fault detection voltage and the alarm signal generation circuit that detection voltage can be converted to alarm signal;It is special Different place is:The fault detection circuit includes detection resistance, and detection resistance one end ground connection, the other end is fault detect The output end of circuit is separately connected one end of the first capacitance, one end of the second capacitance;The other end of first capacitance respectively with The cathode of first Current Limiting Diodes sky and the anode of the second Current Limiting Diodes are connected;The anode of first Current Limiting Diodes passes through First resistor is extremely connected with P, and the cathode of the second current limliting pole pipe is extremely connected by second resistance with P;Second capacitance The other end is connected with the anode of the cathode of third Current Limiting Diodes and the 4th Current Limiting Diodes respectively;The third Current Limiting Diodes Anode be extremely connected with N by 3rd resistor, the cathode of the 4th Current Limiting Diodes is extremely connected by the 4th resistance with N;Institute The input terminal for stating alarm signal generation circuit is connected with the output end of fault detection circuit.
Further, the alarm signal generation circuit includes mainly diode, comparison circuit and signal conversion electricity Road;The diode is in parallel with detection resistance, and one end is connected with the output end of fault detection circuit, other end ground connection;Institute The input terminal for stating comparison circuit is connected with one end of diode, and output end is connected with the input terminal of signaling conversion circuit;Institute Stating diode, fault detection circuit is abnormal and is had an impact to comparison circuit and conversion circuit for preventing;The comparison is electric Road converts detection voltage to comparison signal and sends signaling conversion circuit to;The signaling conversion circuit is converted to comparison signal Alarm signal.
Further, the first resistor, second resistance, 3rd resistor are identical with the resistance value of the 4th resistance;Described One Current Limiting Diodes, the second Current Limiting Diodes, third Current Limiting Diodes and the 4th Current Limiting Diodes are identical.
Still further, the comparison circuit includes chip MC33161, the 5th resistance, the 6th resistance, the 7th resistance and Eight resistance;1 foot of the chip MC33161 is separately connected one end of the 6th resistance and 7 feet of chip MC33161, and the described 6th The other end of resistance is connected by the 5th resistance with one end of diode, while being connected again with 2 feet of chip MC33161; 3 feet of the chip MC33161 are connected by the 8th resistance with one end of diode, while being connect further through the 7th resistance Ground;4 feet of the chip MC33161 are grounded;5 feet and 6 feet of the chip MC33161 connect the input of conversion circuit simultaneously End, 8 feet of the chip are connected with power supply.
Also further, the conversion circuit that connects includes chip SN55451B, the 9th resistance, the tenth resistance, the 11st electricity Resistance, twelfth resistor, third diode, light emitting diode and third capacitance;7 feet and comparison circuit of the chip SN55451B Output end be connected, while being connected with power supply by the 9th resistance;4 feet of the chip SN55451B are grounded, the chip 6 feet of SN55451B are connected by the tenth resistance with power supply;8 feet of the chip SN55451B are separately connected power supply and pass through 5 feet of third capacity earth, the SN55451B are connected by eleventh resistor with power supply, while being separately connected the three or two pole again The anode of pipe and the cathode of light emitting diode, the cathode of the third diode and the anode of light emitting diode connect the tenth simultaneously The other end of one end of two resistance, the twelfth resistor connects power supply.
Further, the diode includes the first diode group and the second diode group, in the first diode There are multiple first diodes to connect on identical forward direction in group, and there are multiple two or two poles in the second diode group It connects on the opposite forward direction of Guan Yu the first diode forward directions, the first diode group is in parallel with the second diode group to be made It must be pointed in different directions.
In the above-mentioned technical solutions, there are four first diodes, there are four second diodes, and the described 1st Pole pipe and the second diode are 1N914ATR diodes.
In the above-mentioned technical solutions, the resistance value of the first resistor, second resistance, 3rd resistor and the 4th resistance is 220k Ω, power 3W;First Current Limiting Diodes, the second Current Limiting Diodes, third Current Limiting Diodes and the 4th Current Limiting Diodes Peak reverse is selected to repeat the 1N4007 type diodes that voltage is 1000V;The resistance value of the detection resistance is 1.1k Ω.
In the above-mentioned technical solutions, the resistance value of the 5th resistance is 243k Ω, and the resistance value of the 6th resistance is 100k The resistance value of Ω, the 7th resistance are 100k Ω, and the resistance value of the 8th resistance (R8) is 56.2k Ω.
In the above-mentioned technical solutions, the third diode is 1N4148 diodes.
The present invention is judging the generation of earth fault by the detection voltage change in detection resistance, then will detection electricity Pressure is converted into comparison signal by comparing, then comparison signal is converted to alarm signal.It improves and direct current mother is born with big resistance Traditional ground fault detection circuit of line voltage, DC bus-bar voltage is born using the capacitance of high pressure, can be effectively detected Earth fault.
The technique effect of the present invention is embodied in:
(1) small.The resistor power index that the present invention selects is small, compared to power in the prior art be tens watts with On resistance, the power of resistance of the present invention is generally several watts.This makes volume also accordingly reduce.
(2) integrated level is high.It since resistance used is small, is advantageously integrated, and detection limit is put without amplification without electric current Big device MIU10 etc cannot be used for the device of pcb board installation.
(3) at low cost.The resistance for selecting power index small, reduces cost, and chip MC33161 and chip The cost of SN55451B is low, further reduces cost.
(4) stable and reliable for performance.The chip MC33161 and chip SN55451B that the present invention selects are common standard core Piece, performance are stablized, and entire circuit reliability service can be made.
Description of the drawings
Fig. 1 is the frequency converter failure detection circuit schematic diagram of the prior art.
Fig. 2 is the fault detection circuit schematic diagram of the present invention.
Fig. 3 is the equivalent circuit schematic of present invention fault detection circuit when breaking down.
Fig. 4 is the alarm signal generation circuit schematic diagram of the present invention.
Fig. 5 is the positive negative overpressure detection principle diagram of chip MC33161.
Specific implementation mode
The performance that the invention will now be described in detail with reference to the accompanying drawings, but it does not constitute limitation of the invention, only does Citing.Simultaneously by explanation, advantages of the present invention will become clearer and be readily appreciated that.
For fault detection circuit schematic diagram as shown in Fig. 2, the one end detection resistance Rs is grounded, the other end is separately connected the first capacitance The signal input part of one end of C1, one end of the second capacitance C2 and alarm signal generation circuit.The other end of first capacitance C1 It is connected respectively with the anode of the cathode of the first Current Limiting Diodes D1 and the second Current Limiting Diodes D2.First Current Limiting Diodes D1 is just Pole is extremely connected by first resistor R1 with P, and the cathode of the second current limliting pole pipe D2 is extremely connected by second resistance R2 with P.Second electricity The other end for holding C2 is connected with the anode of the cathode of third Current Limiting Diodes D3 and the 4th Current Limiting Diodes D4 respectively.Third current limliting The anode of diode D3 is extremely connected by 3rd resistor R3 with N, and the cathode of the 4th Current Limiting Diodes D4 passes through the 4th resistance R4 and N Extremely it is connected.
The principle of fault detection circuit is as follows:Under normal circumstances, 1000V busbar voltages pass through first resistor between P-N R1, the first current limliting D1, the 4th Current Limiting Diodes D4 and the 4th paths pair resistance R4 the first capacitance C1 and the second capacitance C2 charge.When After charging, ignore diode forward pressure drop, the voltage at the first capacitance C1 and the second both ends capacitance C2 is each about 500V.At this time The both ends detection resistance Rs do not have voltage.When earth fault occurs for the poles frequency converter P, S is closed in suitable Fig. 2, between the poles P and ground 1 low resistance R5 is met, at this point, the equivalent circuit of Fig. 2 circuits as shown in figure 3, share two paths, passes through ground connection between P-N Resistance R5, detection resistance Rs, the 4th Current Limiting Diodes D4 and path pair the second capacitance C2 where the 4th resistance R4 charge.The One capacitance C1 is discharged by path where the second Current Limiting Diodes D2, second resistance R2, the 5th resistance R5 and detection resistance Rs, because This can detect earth fault by the variation of detection resistance Rs both end voltages.With the second capacitance C2 chargings and the first capacitance C1 The process of electric discharge, the electric current for flowing through detection resistance Rs are gradually reduced, and both end voltage also reduces therewith, when the second capacitance C2 chargings After the first capacitance C1 electric discharges, the second capacitance C2 voltages are 1000V, and the first capacitance C1 voltages are 0V.Detection resistance at this time Rs both end voltages are just.Since the function of the left and right circuit of fault detection circuit in Fig. 2 is symmetrical, similarly it is found that when the poles N are sent out When raw earth fault, there is similar process, unlike, when earth fault occurs for the poles N the first capacitance C1 charged, the second electricity Hold C2 to discharge, and flow through current direction when earth fault occurs with the poles N for the electric current of detection resistance Rs on the contrary, at this point, Detection resistance Rs both end voltages are negative.
By taking Fig. 3 circuits as an example, the circuit equation that moment occurs for P pole ground faults is following (tube voltage drop for ignoring diode):
Detection voltage Us can be solved by formula (1) to be shown below:
Since first resistor R2 is identical as the 4th resistance R4 resistance values, the first capacitance C1 is identical as the second capacitance C2, therefore, the Two resistance R2 are as the curent change trend on the 4th resistance R4.
First resistor R1, second resistance R2,3rd resistor R3 and the 4th resistance R4 mainly during capacitor charge and discharge from To metering function, and bear half DC bus-bar voltage in a short time when earth fault occurs.When the poles P or the poles N occur When short trouble, the voltage that the resistance in circuit is born is maximum, designs resistance parameter according to short-circuit extreme case, here the first electricity Resistance R1, second resistance R2,3rd resistor R3 and the 4th resistance R4 choose 220k Ω/3W resistance of PR03 series.It is short-circuit extreme Moment is happened, the maximum reverse peak value that the first Current Limiting Diodes D1 and third Current Limiting Diodes D3 is born is 500V, here First Current Limiting Diodes D1, the second Current Limiting Diodes D2, third Current Limiting Diodes D3 and the 4th Current Limiting Diodes D4 select peak It is worth the 1N4007 diodes that inverted repeat voltage is 1000V.Earth fault is set in prior art Earth Fault Detection referring to Fig.1 Threshold value, the threshold value that earth fault is set in this circuit is 130k Ω, i.e., as ground resistance R5≤130k Ω over the ground, assert and become Earth fault occurs for frequency device.Processing in order to facilitate subsequent conditioning circuit to detection voltage detects voltage and sets upon the occurrence of a ground fault Meter chooses detection resistance Rs=1.1k Ω in 2~5V.Can be with abbreviation by parameter substitution formula (2):
As ground resistance R5=130k Ω, voltage Us=2.28V is detected;When ground resistance R5=0 (i.e. ground short circuit) When, detect voltage Us=4.95V.Therefore as detection voltage Us>When 2.28V, show that earth fault occurs for the poles P.Similarly, work as detection Voltage Us<When -2.28V, show that earth fault occurs for the poles N.
Alarm signal generation circuit handles detection voltage, generates alarm signal, is transmitted to host computer.The alarm of design Signal generating circuit is as shown in Figure 4.Influence of the observation circuit failure in front end to back-end circuit in order to prevent, in detection voltage Us two Terminating diode is protected, and it just may be negative that may be due to detection voltage Us, and considers to clamp the voltage at the left sides 2.5V The right side, therefore it is parallel with diode on detection resistance Rs.Include two groups of parallel with one another one or two in diode Pole pipe group and the second diode group, the identical first diode D5 of forward direction there are four series connection in the first diode group, There are four the forward direction second diode D6s opposite with the second diode group for series connection in second diode group.First diode D5 It is 1N914ATR diodes with the second diode D6.
1 foot of chip MC33161 is separately connected one end of the 6th resistance R6 and 7 feet of chip MC33161, the 6th resistance R6 The other end be connected with the signal input part of alarm signal generation circuit by the 5th resistance R5, while again with chip MC33161 2 feet be connected.3 feet of chip MC33161 are connected by the 8th resistance R8 with the signal input part of alarm signal generation circuit, together When further through the 7th resistance R7 ground connection.4 feet of chip MC33161 are grounded, and 5 feet and 6 feet of chip MC33161 connect the 9th simultaneously The other end of one end of resistance R9, the 9th resistance R9 is connected with power vd D.8 feet of chip MC33161 are connected with power vd D.
4 feet of chip SN55451B are grounded, and 7 feet are connected with one end of the 9th resistance R9, and 6 feet pass through the tenth resistance R10 is connected with power vd D, and 8 feet are separately connected power vd D and are grounded by third capacitance C3, and 5 feet of SN55451B pass through Eleventh resistor R11 is connected with power vd D, while being separately connected the anode of third diode D7 and bearing for light emitting diode D8 again Pole, the cathode of the third diode D7 connect one end of twelfth resistor R12 with the anode of light emitting diode D8 simultaneously, described The other end connection power vd D of twelfth resistor R12.
Chip MC33161 in Fig. 4 is general voltage monitoring chip, realizes positive overvoltage here with this chip and bore Pressure monitoring.The positive overvoltages of MC33161 and negative overpressure monitoring voltage principle are as shown in Figure 5.According to the databook of MC33161,3 are drawn Foot input is set as positive overvoltage monitoring, the limit value V in Fig. 51With V2It can be acquired by following equation (4) and formula (5), 2 are drawn Foot input is set as negative overpressure monitoring, limit value V3With V4It can be acquired by following equation (6) and formula (7):
Wherein, Vth1With Vth2It is the threshold voltage of chip MC33161 internal comparators, is 1.27V, VH1With VH2It is core Hysteresis voltage inside piece MC33161, is 0.025V.VrefIt is 2.54V to be chip MC33161 internal reference voltages.
The 8th resistance R8=56.2k Ω, the 7th resistance R7=100k Ω is taken to pass through in the alarm signal generation circuit of Fig. 4 Formula (5) calculates it is found that positive overvoltage monitoring threshold V2=1.98V, when detecting voltage Us more than 1.98V, chip MC33161's 5 feet and 6 feet export low level;Formula (6) calculates to obtain V1=1.94V, when detecting voltage Us and being less than 1.94V, (MC33161's is stagnant Return characteristic), 5 feet of chip MC33161 and 6 feet export high level.The 5th resistance R5=243k Ω, the 6th resistance R6 is taken in circuit =100k Ω are calculated by formula (7) it is found that negative overpressure monitoring threshold about V4=-1.9V, when Us is less than -1.9V, chip 5 feet of MC33161 and 6 feet export low level;Formula (6) calculates to obtain V3=-1.82V when Us be more than -1.82V when (MC33161's Hysteretic characteristic), 5 feet of chip MC33161 and 6 feet export high level.
Chip SN55451B in Fig. 4 is optical fiber driving chip (including two and door), and here only with 1 channel, 6 draw Foot is set as permanent high by pull-up resistor, and upon the occurrence of a ground fault, the 7 pin input low levels of chip SN55451B are (i.e. The 5 of MC33161, when 6 pins export low level), 5 pins export low level, and optical fiber head shines, and is passed in this, as alarm signal To host computer.
9th resistance R9, the tenth resistance R10 are identical with the resistance value of eleventh resistor R11, are 1k Ω.Third diode D7 For 1N4148 diodes.
The alarm signal generation circuit of the present invention can also have other ways of realization, structure and the sheet of all fault detection circuits Invention is consistent, in the protection domain for all falling within this patent requirement.

Claims (10)

1. a kind of Earth Fault Detection warning circuit of frequency converter, including produce fault detection voltage fault detection circuit and Detection voltage can be converted to the alarm signal generation circuit of alarm signal;It is characterized in that:
The fault detection circuit includes detection resistance (Rs), and detection resistance (Rs) one end ground connection, the other end is examined for failure The output end of slowdown monitoring circuit is separately connected one end of the first capacitance (C1), one end of the second capacitance (C2);
The other end of first capacitance (C1) respectively with the cathode and the second Current Limiting Diodes of the first Current Limiting Diodes (D1) (D2) anode is connected;The anode of first Current Limiting Diodes (D1) is extremely connected by first resistor (R1) with P, and described second The cathode of current limliting pole pipe (D2) is extremely connected by second resistance (R2) with P;
The other end of second capacitance (C2) respectively with the cathode and the 4th Current Limiting Diodes of third Current Limiting Diodes (D3) (D4) anode is connected;The anode of the third Current Limiting Diodes (D3) is extremely connected by 3rd resistor (R3) with N, and the described 4th The cathode of Current Limiting Diodes (D4) is extremely connected by the 4th resistance (R4) with N;
The input terminal of the alarm signal generation circuit is connected with the output end of fault detection circuit.
2. the Earth Fault Detection warning circuit of frequency converter according to claim 1, it is characterised in that:The alarm signal Generation circuit includes mainly diode (1), comparison circuit (2) and signaling conversion circuit (3);
The diode (1) is in parallel with detection resistance (Rs), and one end is connected with the output end of fault detection circuit, the other end Ground connection;
The input terminal of the comparison circuit (2) is connected with one end of diode (1), output end and signaling conversion circuit (3) Input terminal be connected;
Fault detection circuit is abnormal and is generated to comparison circuit (2) and conversion circuit (3) for preventing for the diode (1) It influences;
The comparison circuit (2) converts detection voltage to comparison signal and sends signaling conversion circuit (3) to;
Comparison signal is converted to alarm signal by the signaling conversion circuit (3).
3. the Earth Fault Detection warning circuit of frequency converter according to claim 1, it is characterised in that:The first resistor (R1), second resistance (R2), 3rd resistor (R3) are identical with the resistance value of the 4th resistance (R4);First Current Limiting Diodes (D1), the second Current Limiting Diodes (D2), third Current Limiting Diodes (D3) and the 4th Current Limiting Diodes (D4) are identical.
4. the Earth Fault Detection warning circuit of frequency converter according to claim 2, it is characterised in that:The comparison circuit (2) include chip MC33161, the 5th resistance (R5), the 6th resistance (R6), the 7th resistance (R7) and the 8th resistance (R8);
1 foot of the chip MC33161 is separately connected 7 feet of one end and chip MC33161 of the 6th resistance (R6), and the described 6th The other end of resistance (R6) is connected by the 5th resistance (R5) with one end of diode (1), at the same again with chip MC33161 2 feet be connected;3 feet of the chip MC33161 are connected by the 8th resistance (R8) with one end of diode (1), simultaneously It is grounded further through the 7th resistance (R7);4 feet of the chip MC33161 are grounded;5 feet and 6 feet of the chip MC33161 are simultaneously The input terminal of conversion circuit (3) is connected, 8 feet of the chip are connected with power supply (VDD).
5. the Earth Fault Detection warning circuit of frequency converter according to claim 2, it is characterised in that:The signal conversion Circuit (3) includes chip SN55451B, the 9th resistance (R9), the tenth resistance (R10), eleventh resistor (R11), twelfth resistor (R12), third diode (D7), light emitting diode (D8) and third capacitance (C3);
7 feet of the chip SN55451B are connected with the output end of comparison circuit (2), while passing through the 9th resistance (R9) and power supply (VDD) it is connected;4 feet of the chip SN55451B are grounded, 6 feet of the chip SN55451B by the tenth resistance (R10) with Power supply (VDD) is connected;8 feet of the chip SN55451B are separately connected power supply (VDD) and are grounded by third capacitance (C3), 5 feet of the SN55451B are connected by eleventh resistor (R11) with power supply (VDD), while being separately connected third diode again (D7) cathode of anode and light emitting diode (D8), the cathode and light emitting diode (D8) of the third diode (D7) are just Pole connects one end of twelfth resistor (R12), the other end connection power supply (VDD) of the twelfth resistor (R12) simultaneously.
6. the Earth Fault Detection warning circuit of frequency converter according to claim 2, it is characterised in that:The diode list First (1) includes the first diode group and the second diode group, has multiple first diodes (D5) in phase in the first diode group With forward direction on connect, and have in the second diode group multiple second diodes (D6) with the first diode (D5) It connects on the opposite forward direction of forward direction, the first diode group is in parallel with the second diode group so that being pointed in different directions.
7. the Earth Fault Detection warning circuit of frequency converter according to claim 6, it is characterised in that:One or two pole It manages there are four (D5), there are four second diodes (D6), and first diode (D5) and the second diode (D6) are 1N914ATR diodes.
8. the Earth Fault Detection warning circuit of frequency converter according to claim 3, it is characterised in that:The first resistor (R1), the resistance value of second resistance (R2), 3rd resistor (R3) and the 4th resistance (R4) is 220k Ω, power 3W;Described first Current Limiting Diodes (D1), the second Current Limiting Diodes (D2), third Current Limiting Diodes (D3) and the 4th Current Limiting Diodes (D4) are selected Peak reverse repeats the 1N4007 type diodes that voltage is 1000V;The resistance value of the detection resistance (Rs) is 1.1k Ω.
9. the Earth Fault Detection warning circuit of frequency converter according to claim 4, it is characterised in that:5th resistance (R5) resistance value is 243k Ω, and the resistance value of the 6th resistance (R6) is 100k Ω, and the resistance value of the 7th resistance (R7) is The resistance value of 100k Ω, the 8th resistance (R8) are 56.2k Ω.
10. the Earth Fault Detection warning circuit of frequency converter according to claim 5, it is characterised in that:Described 3rd 2 Pole pipe (D7) is 1N4148 diodes.
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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
CN112881940B (en) * 2019-11-14 2022-07-26 华为技术有限公司 Grounding state detection circuit, electrical system and grounding state detection method thereof

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