A fault detection circuit and apparatus

Abstract

The application discloses a kind of fault detection circuit and device, including detection front end, current detection unit, overcurrent protection self-locking unit and detection rear end;The detection front end is electrically connected with the live side of circuit;The detection front end is electrically connected with the input end of the current detection unit, and the current detection unit is used to detect the current value of the live side of circuit;The input end of the current detection unit is electrically connected with the overcurrent protection self-locking unit, and the overcurrent protection self-locking unit is used to carry out power-off protection;The output end of the current detection unit is electrically connected with the detection rear end, and the detection rear end is electrically connected with the fault side of circuit;The application aims to provide a kind of fault detection circuit and device, installation is fast, easy to operate, can provide power-off protection function, the safety performance of circuit is high, can shorten the time of fault processing judgment, improve the experience of customer, strong popularization, good portability, economy.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power detection, in particular to a fault detection circuit and device. BACKGROUND

[0002] With the rapid development of national economy, the acceleration of urbanization development process, people's living standards have been improved, and the power consumption is increasing, and the overall quality and quantity of power resources are gradually improved. The power supply measurement department is facing the increase of metering business volume, and also faces the problem of increasing work load of customer side electric energy meter fault. At present, after the electric energy meter fails, the fault troubleshooting work is tedious and difficult. The traditional fault test and troubleshooting is difficult, and there is no special test host for instantaneous short circuit in the troubleshooting process, which has great safety hazard, low processing efficiency, and cannot read the electric energy meter data on site in the first time to identify and judge the fault, which affects the user's power consumption and easily causes the contradiction between the customer and the power supply department.

[0003] In the existing electric energy meter fault processing work, if the on-site equipment does not have the function of reading the phase fault current fault point, and the fault point needs to be found one by one, three-phase fault will cause the problem of unable to send power, so it is impossible to observe the size of the test phase short circuit current, and the required data cannot be obtained, and the on-site fault is difficult to judge, which brings inconvenience to the workers.

[0004] The current fault detection has many shortcomings: the short circuit current caused by three-phase fault is too large, the value cannot be tested, the personnel operation has great safety hazard; the fault judgment efficiency is low, the fault processing time is too long, and the man-machine efficiency is low; the customer's demand processing time is too long, the problem cannot be judged on site at one time, and user complaints are easy to cause. SUMMARY

[0005] The purpose of the present application is to provide a fault detection circuit and device, which is fast to install, easy to operate, can provide power-off protection function, has high safety performance, can shorten the fault processing and judgment time, improve the customer experience, has strong popularization, good portability and economy.

[0006] To achieve this purpose, the present application adopts the following technical scheme: a fault detection circuit, comprising a detection front end, a current detection unit, an overcurrent protection self-locking unit and a detection rear end;

[0007] The detection front end is electrically connected with the live side of the circuit; the detection front end is electrically connected with the input end of the current detection unit, and the current detection unit is used for detecting the current value of the live side of the circuit;

[0008] The current detection unit is electrically connected with the input end of the over-current protection self-locking unit, and the over-current protection self-locking unit is used for power-off protection.

[0009] The output end of the current detection unit is electrically connected with the detection rear end, and the detection rear end is electrically connected with the fault side of the circuit.

[0010] Preferably, the current detection unit comprises a three-phase current transformer and an ammeter, three-phase input ends of the three-phase current transformer are electrically connected with the detection front end, and two phases of three-phase output ends of the three-phase current transformer are electrically connected with the ammeter.

[0011] Preferably, the over-current protection self-locking unit comprises an alternating current contactor, a motor protector, an over-current protection circuit, a closing switch and an opening switch, three-phase input main contacts of the alternating current contactor are electrically connected with the three-phase output ends of the three-phase current transformer, three-phase output main contacts of the alternating current contactor are electrically connected with three-phase input ends of the motor protector, three-phase output ends of the motor protector are electrically connected with the detection rear end, a 95 contact of the motor protector is electrically connected with the opening switch, the opening switch is electrically connected with one of the three-phase output main contacts of the alternating current contactor, an auxiliary normally open contact of the alternating current contactor is electrically connected with the closing switch, the closing switch is electrically connected with a 96 contact of the motor protector, the 96 contact of the motor protector is electrically connected with another auxiliary normally open contact of the alternating current contactor, a positive input end of the over-current protection circuit is electrically connected with the 95 contact of the motor protector, and a negative input end of the over-current protection circuit is electrically connected with the 96 contact of the motor protector.

[0012] Preferably, the over-current protection circuit comprises a programming control chip, a logic operation chip, resistors R1, R2, R3, R4, R5, R6, R9, R10, capacitors C1, C2, C3, C4, C9, an adjustable resistor R, a variable resistor CW2, a potentiometer W and a switching diode WD.

[0013] The programming control chip is electrically connected with the logic operation chip, a first pin of the logic operation chip is electrically connected with one end of the capacitor C1 and one end of the resistor R2, the other end of the capacitor C1 is electrically connected with a second pin of the logic operation chip, and the other end of the resistor R2 is electrically connected with a twenty-first pin of the logic operation chip; a twenty-second pin of the logic operation chip is electrically connected with one end of the adjustable resistor R, the other end of the adjustable resistor R is electrically connected with a twenty-fourth pin of the logic operation chip, an adjusting end of the adjustable resistor R is electrically connected with one end of the resistor R10, and the other end of the resistor R10 is electrically connected with a nineteenth pin of the logic operation chip.

[0014] The 26th pin of the logic operation chip is electrically connected with one end of the resistor R6 and one end of the switching diode WD, the other end of the switching diode WD is electrically connected with one end of the resistor R1, the other end of the resistor R1 is electrically connected with one end of the potentiometer W, the other end of the potentiometer W is electrically connected with one end of the resistor R6 and the 27th pin of the logic operation chip;

[0015] The 28th pin of the logic operation chip is electrically connected with one end of the capacitor C3, the other end of the capacitor C3 is electrically connected with the 29th pin of the logic operation chip and one end of the resistor R3, the other end of the resistor R3 is electrically connected with the 96th contact of the motor protector and one end of the capacitor C9, the other end of the capacitor C9 is electrically connected with the 95th contact of the motor protector and one end of the resistor R4, the other end of the resistor R4 is electrically connected with one end of the variable resistor CW2, the other end of the variable resistor CW2 is electrically connected with the 38th pin of the logic operation chip and one end of the resistor R10;

[0016] The 30th pin of the logic operation chip is electrically connected with one end of the resistor R6, the other end of the resistor R6 is electrically connected with the 36th pin of the logic operation chip;

[0017] The 31st pin of the logic operation chip is electrically connected with one end of the capacitor C4, the other end of the capacitor C4 is electrically connected with the 32nd pin of the logic operation chip;

[0018] The 33rd pin of the logic operation chip is electrically connected with one end of the capacitor C2 and one end of the resistor R10, the other end of the capacitor C2 is electrically connected with one end of the resistor R10, the 37th pin of the logic operation chip is electrically connected with one end of the resistor R10;

[0019] The 25th pin of the logic operation chip and the 40th pin of the logic operation chip are electrically connected with one end of the resistor R9, the other end of the resistor R9 is electrically connected with one end of the resistor R10.

[0020] Preferably, a three-phase air switch is arranged in the circuit between the detection front end and the current detection unit.

[0021] Preferably, three indicator lights are connected in parallel with the detection rear end.

[0022] A fault detection device adopting the above fault detection circuit, comprising a box body, an input end, three-phase indicator lights, a three-phase main switch, a tripping button, a closing button and an output end.

[0023] The input end is electrically connected with the detection front end, the output end is electrically connected with the detection rear end, the input end and the output end are arranged on the side wall of the box body, the three-phase indicating lamp, the three-phase total switch, the opening button and the closing button are arranged on the upper surface of the box body, the opening button is electrically connected with the opening switch of the over-current protection self-locking unit, the closing button is electrically connected with the closing switch of the over-current protection self-locking unit, and the display end surface of the ammeter of the current detection unit is located on the upper surface of the box body; and the three-phase total switch is electrically connected with the three-phase air switch of the over-current protection self-locking unit.

[0024] The technical scheme of one embodiment of the present application has the advantages that: the connection mode of the circuit is simple, and the operation is simple; the power-off protection function is provided, the safety performance of the circuit is high, the circuit design structure can be reduced, the circuit has the advantages of small size, light weight, convenient carrying and the like; the fault detection circuit is used for fault processing, the time required for single electric energy meter fault judgment can be shortened to 1 minute, the processing time of customer appeal is shortened, the possibility of customer complaint is reduced, and customer satisfaction is improved; the work efficiency of the circuit is improved, the on-site operation efficiency is greatly improved compared with traditional operation, the safety factor is high; the circuit has strong popularization and good portability and economy. BRIEF DESCRIPTION OF DRAWINGS

[0025] Fig. 1 is a connection schematic diagram of the circuit of one embodiment of the present application;

[0026] Fig. 2 is a connection schematic diagram of the over-current protection circuit of one embodiment of the present application;

[0027] Fig. 3 is a structure schematic diagram of the device of one embodiment of the present application.

[0028] Among them: detection front end 1, current detection unit 2, three-phase current transformer 21, ammeter 22;

[0029] Over-current protection self-locking unit 3, AC contactor 31, motor protector 32, over-current protection circuit 33, programming control chip 331, logic operation chip 332, closing switch 34, opening switch 35; detection rear end 4; three-phase air switch 5;

[0030] Box body 6, three-phase indicating lamp 7, three-phase total switch 8, opening button 9, closing button 10. DETAILED DESCRIPTION

[0031] The technical scheme of the present application will be further described below by combining the drawings and through specific embodiments.

[0032] Embodiments of the present application are described below in detail, examples of which are shown in the drawings, wherein the same or similar notations represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by reference to the drawings are exemplary only, for the purpose of explanation, and are not to be understood as limiting the present application.

[0033] In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specified.

[0034] Referring to Figs. 1 to 3 As shown in the drawings, a fault detection circuit comprises a detection front end 1, a current detection unit 2, an overcurrent protection self-locking unit 3 and a detection rear end 4.

[0035] The detection front end 1 is electrically connected to the live side of the circuit; the detection front end 1 is electrically connected to the input end of the current detection unit 2, and the current detection unit 2 is used to detect the current value of the live side of the circuit.

[0036] The current detection unit 2 is electrically connected to the input end of the overcurrent protection self-locking unit 3, and the overcurrent protection self-locking unit 3 is used for power-off protection.

[0037] The output end of the current detection unit 2 is electrically connected to the detection rear end 4, and the detection rear end 4 is electrically connected to the fault side of the circuit.

[0038] In operation, the detection front end 1 is only connected to the live side of the circuit, and the detection rear end 4 is connected to the fault side of the circuit, so that the connection of the detection circuit is completed, the connection mode is simple, and the operation is simple; the current value of the live side of the circuit is detected by the current detection unit 2, and the overcurrent protection self-locking unit 3 provides power-off protection at the same time, so that the safety performance is high, the circuit design structure is reduced, and the advantages of small size, light weight, portability and the like are achieved; the fault handling is performed by the fault detection circuit, so that the time required for single energy meter fault judgment is shortened to 1 minute, the processing time of customer complaints is shortened, the possibility of customer complaints is reduced, and the customer satisfaction is improved; the work efficiency of the circuit is improved, the on-site operation efficiency is greatly improved compared with the traditional operation, and the safety factor is high; the fault detection circuit has strong popularization, portability and good economy.

[0039] Preferably, the current detection unit 2 comprises a three-phase current transformer 21 and an ammeter 22, the three-phase input end of the three-phase current transformer 21 is electrically connected to the detection front end 1, and the three-phase output end of the three-phase current transformer 21 is electrically connected to the ammeter 22.

[0040] The three-phase or three-phase four-wire after the detection front-end connection table, voltage matching AC 0.4kV voltage, ammeter 22 starting voltage is 100V-400V power supply, make control circuit meet AC 400V power supply, meet the circuit work and control requirements.

[0041] Specifically, the overcurrent protection self-locking unit 3 includes an AC contactor 31, a motor protector 32, an overcurrent protection circuit 33, a closing switch 34 and an opening switch 35; the three-phase input main contact of the AC contactor 31 is electrically connected with the three-phase output end of the three-phase current transformer 21, the three-phase output main contact of the AC contactor 31 is electrically connected with the three-phase input end of the motor protector 32, and the three-phase output end of the motor protector 32 is electrically connected with the detection rear end 4; the 95 contact of the motor protector 32 is electrically connected with the opening switch 35, the opening switch 35 is electrically connected with one of the three-phase output main contacts of the AC contactor 31, one auxiliary normally open contact of the AC contactor 31 is electrically connected with the closing switch 34, the closing switch 34 is electrically connected with the 96 contact of the motor protector 32, and the 96 contact of the motor protector 32 is electrically connected with another auxiliary normally open contact of the AC contactor 31; the positive input end of the overcurrent protection circuit 33 is electrically connected with the 95 contact of the motor protector 32, and the negative input end of the overcurrent protection circuit 33 is electrically connected with the 96 contact of the motor protector 32.

[0042] The overcurrent protection self-locking unit 3 is used to realize overcurrent protection self-locking control, the moving coil of the AC contactor 31 is connected with two phases in the three-phase line after the ammeter 22, one end of the coil is connected with one phase, the other end of the coil is connected with the normally open contact of the AC contactor in parallel, the normally open contact is connected with the closing switch in series, the 96 contact of the motor protector is connected, and the 95 contact of the motor protector is connected to the opening switch in series, and finally connected to the other phase to form a loop. The 96 contact of the motor protector is connected to the other end of the normally open contact of the AC contactor. The AC contactor is powered by AC 400V, the contactor is actuated after the loop is closed, the fault line is connected, and the power supply after the meter is realized. The line fault diagnosis is realized; the closing switch 34 uses the normally open contact, and the opening switch 35 uses the normally closed contact. The 95 / 96 contacts of the motor protector are normally closed contacts, the solid-state contact in the motor protector is actuated, the line is separated, and the AC contactor is cut off; the motor protector is set by the flow, the 95 / 96 contacts are actuated, and the contact mode is changed.

[0043] Preferably, the overcurrent protection circuit 33 comprises a program control chip 331, a logic operation chip 332, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a resistor R9, a resistor R10, a capacitor C1, a capacitor C2, a capacitor C3, a capacitor C4, a capacitor C9, an adjustable resistor R, a variable resistor CW2, a potentiometer W and a switching diode WD.

[0044] The program control chip 331 is electrically connected with the logic operation chip 332, a first pin of the logic operation chip 332 is electrically connected with one end of the capacitor C1 and one end of the resistor R2, the other end of the capacitor C1 is electrically connected with a second pin of the logic operation chip 332, and the other end of the resistor R2 is electrically connected with a twenty-first pin of the logic operation chip 332; a twenty-second pin of the logic operation chip 332 is electrically connected with one end of the adjustable resistor R, the other end of the adjustable resistor R is electrically connected with a twenty-fourth pin of the logic operation chip 332, an adjusting end of the adjustable resistor R is electrically connected with one end of the resistor R10, and the other end of the resistor R10 is electrically connected with a nineteenth pin of the logic operation chip 332.

[0045] A twenty-sixth pin of the logic operation chip 332 is electrically connected with one end of the resistor R5 and one end of the switching diode WD, the other end of the switching diode WD is electrically connected with one end of the resistor R1, the other end of the resistor R1 is electrically connected with one end of the potentiometer W, the other end of the potentiometer W is electrically connected with the other end of the resistor R5 and a twenty-seventh pin of the logic operation chip 332.

[0046] A twenty-eighth pin of the logic operation chip 332 is electrically connected with one end of the capacitor C3, the other end of the capacitor C3 is electrically connected with a twenty-ninth pin of the logic operation chip 332 and one end of the resistor R3, the other end of the resistor R3 is electrically connected with a 96 contact of the motor protector 32 and one end of the capacitor C9; the other end of the capacitor C9 is electrically connected with a 95 contact of the motor protector 32 and one end of the resistor R4, the other end of the resistor R4 is electrically connected with one end of the variable resistor CW2, the other end of the variable resistor CW2 is electrically connected with a thirty-eighth pin of the logic operation chip 332 and one end of the resistor R10.

[0047] A thirtieth pin of the logic operation chip 332 is electrically connected with one end of the resistor R6, and the other end of the resistor R6 is electrically connected with a thirty-sixth pin of the logic operation chip 332.

[0048] The 31st pin of the logic operation chip 332 is electrically connected with one end of the capacitor C4, and the other end of the capacitor C4 is electrically connected with the 32nd pin of the logic operation chip 332;

[0049] The 33rd pin of the logic operation chip 332 is electrically connected with one end of the capacitor C2 and one end of the resistor R10, and the other end of the capacitor C2 is electrically connected with one end of the resistor R10; and the 37th pin of the logic operation chip 332 is electrically connected with one end of the resistor R10.

[0050] The 25th pin of the logic operation chip 332 and the 40th pin of the logic operation chip 332 are electrically connected with one end of the resistor R9, and the other end of the resistor R9 is electrically connected with one end of the resistor R10.

[0051] The overcurrent protection circuit 33 adopts a programmable chip to cooperate with a motor protector to realize setting, and plays a role of protecting a main circuit and feeding a signal to an indicating lamp.

[0052] The overcurrent protection circuit 33 integrates two chips and other electronic elements. The two chips are an SST programming control chip and a logic operation chip. The logic operation chip is a 40-pin four-bit chip, which can realize data acquisition and analog-to-digital conversion functions, and can process the acquired data. In the circuit diagram, IN is an AC signal that enters the data acquisition end after rectification, and the electrical signal is input after filtering and energy storage. The signal is transmitted to the logic operation chip through a combination circuit composed of a capacitor, a resistor and a diode. The logic operation chip transmits the operation signal to the programming control chip through pin 5, pin 10 and pin 15. The designer determines the final parameters and transmits them to the programmable control chip through debugging. After the program is sealed, the logic operation chip can operate normally. Unlike the traditional closed-loop control system, the controllable protection circuit can be combined with the traditional closed-loop control system through this logic operation chip, and the insecurity brought by the traditional overcurrent protection can be abandoned. The analog signal is converted into a digital signal through the analog-to-digital conversion in the chip, and the digital signal is analyzed and operated by the operation unit to realize accurate sampling and protection.

[0053] High-precision protection and diagnosis accessories are selected, and a protection and diagnosis circuit is integrated to realize fault phase and current detection. The electric energy meter can be connected behind the on-site power supply, and the current data of each phase after power supply can be read. The operation personnel can complete the electric energy meter fault detection within one minute. Through protection and test current data, the working time can be greatly shortened, and the work efficiency can be improved.

[0054] Specifically, a three-phase air switch 5 is arranged in the circuit between the detection front end 1 and the current detection unit 2.

[0055] The three-phase air switch is selected to allow the maximum current to be 100A, has strong isolation capacity, withstands AC 1000V without discharge breakdown, uses a round surface contact point inside, has a large contact surface and strong overcurrent capacity.

[0056] Preferably, the detection rear end 4 is connected in parallel with three indicator lights.

[0057] The indicator light is used to display the fault indication of the fault phase; the fault indication is composed of three-color yellow-green-red indicator lights, the indicator light is powered by the three-phase meter rear power supply, is connected with the overcurrent protection circuit 33, and the fault of the indicator light circuit is analyzed through logic analysis to meet the line fault indication and play a role in overcurrent fault screening.

[0058] A fault detection device comprises a box body 6, an input end, three-phase indicator lights 7, a three-phase total switch 8, a tripping button 9, a closing button 10 and an output end.

[0059] The input end is electrically connected with the detection front end 1, the output end is electrically connected with the detection rear end 4, the input end and the output end are arranged on the side wall of the box body 6, the three-phase indicator lights 7, the three-phase total switch 8, the tripping button 9 and the closing button 10 are arranged on the upper surface of the box body 6, the tripping button 9 is electrically connected with the tripping switch of the overcurrent protection self-locking unit 3, the closing button 10 is electrically connected with the closing switch of the overcurrent protection self-locking unit 3, and the display end surface of the ammeter of the current detection unit 2 is located on the upper surface of the box body 6; the three-phase total switch 8 is electrically connected with the three-phase air switch of the overcurrent protection self-locking unit 3.

[0060] The device has simple wiring, the wiring ends of the input end and the output end are provided with banana plugs and alligator clips, can adapt to various wiring ports, has small volume and light weight, only 350*220*150mm and 2kg in weight, is convenient to carry, can be directly connected to the meter rear, is convenient and reliable in power taking, does not need external power supply, is provided with a three-phase air switch and a motor protector, can improve the safety performance of the device, can display the fault through the digital display three-phase current and the three-phase indicator light, can judge the fault phase of the detection rear end, and the phase determination time is short and the action time is completed within 1 minute.

[0061] The device has simple wiring and operation, can realize one-key starting, has small volume and light weight, is convenient to carry, is convenient and reliable in the meter rear power taking mode, can improve the safety performance of the circuit through the three-phase air switch and the motor protector, has low manufacturing cost, is reproducible, has strong popularization, and has high man-machine efficiency.

[0062] In the description of the specification, the description of the terms "embodiment", "example", and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any suitable manner in any one or more embodiments or examples.

[0063] The technical principles of the present application are described above in connection with specific embodiments. These descriptions are only for the purpose of explaining the principles of the present application and cannot be interpreted in any way as a limitation on the scope of protection of the present application. Based on the explanations here, those skilled in the art can think of other specific embodiments of the present application without creative labor, and these embodiments will fall within the scope of protection of the present application.

Claims

1. A fault detection circuit, characterized by, The detection front end, the current detection unit, the overcurrent protection self-locking unit and the detection back end are connected in series. The detection front end is electrically connected with the live side of the circuit, and the input end of the current detection unit is electrically connected with the detection front end. The input end of the overcurrent protection self-locking unit is electrically connected with the current detection unit, and the overcurrent protection self-locking unit is used for power-off protection. The output end of the current detection unit is electrically connected with the detection back end, and the detection back end is electrically connected with the fault side of the circuit. The current detection unit comprises a three-phase current transformer and an ammeter, and the three-phase input end of the three-phase current transformer is electrically connected with the detection front end. The three-phase output end of the three-phase current transformer is electrically connected with the ammeter. The overcurrent protection self-locking unit comprises an AC contactor, a motor protector, an overcurrent protection circuit, a closing switch and an opening switch.

2. A fault detection circuit according to claim 1, characterised in that, The three-phase input main contact of the AC contactor is electrically connected with the three-phase output end of the three-phase current transformer, the three-phase output main contact of the AC contactor is electrically connected with the three-phase input end of the motor protector, the three-phase output end of the motor protector is electrically connected with the detection back end, the 95 contact of the motor protector is electrically connected with the opening switch, one of the three-phase output main contacts of the AC contactor is electrically connected with the opening switch, one auxiliary normally open contact of the AC contactor is electrically connected with the closing switch, the 96 contact of the motor protector is electrically connected with the closing switch, and the other auxiliary normally open contact of the AC contactor is electrically connected with the 96 contact of the motor protector. The circuit between the detection front end and the current detection unit is provided with a three-phase air switch. The overcurrent protection circuit comprises a programming control chip, a logic operation chip, resistors R1, R2, R3, R4, R5, R6, R9, R10, capacitors C1, C2, C3, C4, C9, an adjustable resistor R, a variable resistor CW2, a potentiometer W and a switching diode WD. The programming control chip is electrically connected with the logic operation chip, the first pin of the logic operation chip is electrically connected with one end of the capacitor C1 and one end of the resistor R2, the other end of the capacitor C1 is electrically connected with the second pin of the logic operation chip, and the other end of the resistor R2 is electrically connected with the 21st pin of the logic operation chip. The 22nd pin of the logic operation chip is electrically connected with one end of the adjustable resistor R, the other end of the adjustable resistor R is electrically connected with the 24th pin of the logic operation chip, the adjusting end of the adjustable resistor R is electrically connected with one end of the resistor R10, and the other end of the resistor R10 is electrically connected with the 19th pin of the logic operation chip. The 26th pin of the logic operation chip is electrically connected with one end of the resistor R6 and one end of the switching diode WD, the other end of the switching diode WD is electrically connected with one end of the resistor R1, the other end of the resistor R1 is electrically connected with one end of the potentiometer W, the other end of the potentiometer W is electrically connected with one end of the resistor R6 and the 27th pin of the logic operation chip; The 28th pin of the logic operation chip is electrically connected with one end of the capacitor C3, the other end of the capacitor C3 is electrically connected with the 29th pin of the logic operation chip and one end of the resistor R3, the other end of the resistor R3 is electrically connected with the 96th contact of the motor protector and one end of the capacitor C9, the other end of the capacitor C9 is electrically connected with the 95th contact of the motor protector and one end of the resistor R4, the other end of the resistor R4 is electrically connected with one end of the variable resistor CW2, the other end of the variable resistor CW2 is electrically connected with the 38th pin of the logic operation chip and one end of the resistor R10; The 30th pin of the logic operation chip is electrically connected with one end of the resistor R6, the other end of the resistor R6 is electrically connected with the 36th pin of the logic operation chip; The 31st pin of the logic operation chip is electrically connected with one end of the capacitor C4, the other end of the capacitor C4 is electrically connected with the 32nd pin of the logic operation chip; The 33rd pin of the logic operation chip is electrically connected with one end of the capacitor C2 and one end of the resistor R10, the other end of the capacitor C2 is electrically connected with one end of the resistor R10, the 37th pin of the logic operation chip is electrically connected with one end of the resistor R10; The 25th pin of the logic operation chip and the 40th pin of the logic operation chip are electrically connected with one end of the resistor R9, the other end of the resistor R9 is electrically connected with one end of the resistor R10.

3. A fault detection circuit according to claim 1, wherein The detection rear end is connected in parallel with three indicator lights.

4. A failure detection apparatus employing the failure detection circuit according to any one of claims 1 to 2, characterized by It comprises a box body, an input end, three-phase indicator lights, a three-phase total switch, a tripping button, a closing button and an output end; The input end is electrically connected with the detection front end, the output end is electrically connected with the detection rear end, the input end and the output end are arranged on the side wall of the box body, the three-phase indicator lights, the three-phase total switch, the tripping button and the closing button are arranged on the upper surface of the box body, the tripping button is electrically connected with the tripping switch of the over-current protection self-locking unit, the closing button is electrically connected with the closing switch of the over-current protection self-locking unit, and the display end of the ammeter of the current detection unit is located on the upper surface of the box body; the three-phase total switch is electrically connected with the three-phase air switch of the over-current protection self-locking unit.

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