Of 9 means of settlements of PLC breakdown problem detailed and analytic

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In recent years, as social development, PLC but program controller got extensive use in industrial production, at the same time technical personnel uses a requirement to also be in to its heighten of year after year, because this is normal to the system stability service requirement is taller and taller also. The dependability of PLC product itself can assure, but a few incorrect operations in applying can cause certain effect. Arranged a few PLC to use 9 medium little skill daily for everybody, the hope is using PLC to be helped somewhat daily to everybody. One, PLC oneself breakdown is judged generally speaking, PLC is extremely reliable equipment, give fault rate very low. The hardware such as the CPU of PLC damages or software runs the probability that make mistake to be almost 0; If PLC input dot is not strong report inbreaks be caused by, also won't damage almost; Of PLC output relay often drive a point, short circuit of except periphery load or design are unreasonable, load current exceeds rated range, the life of contact is very long also. Accordingly, we search electric trouble spot, the periphery that should be put in PLC mainly is electric on component, always do not suspect PLC hardware or program to have a problem, equipment of this good to fast maintenance breakdown, fast extensive is resurgent producing is very important, the PLC that talks because of this author place controls the electric corrective maintenance of loop, the key is absent PLC itself, however the periphery in loop of PLC place control is electric component. 2, the input is outputted (I/O) of module choose output module cent to be transistor, two-way silicon controlled rectifier, contact model. Transistor switch rate is the rapiddest (general 0.

2ms) , but laden capacity is the smallest, about 0.

2~0.

3A, 24VDC, apply to the equipment that sudden switch, signal contacts, wait for signal to join with device of frequency conversion, dc commonly, should note the effect of transistor leakage current to load. Silicon controlled rectifier advantage is not to have contact, have communication load performance, laden ability is not great. Output has relay hand in dc load characteristic, laden ability is great. Relay is chosen above all commonly in groovy control contact output, defect is switch speed slow, control in 10ms commonly, unwell apply at high frequency switch. 3, requirement of ground connection of system of PLC of ground connection problem is stricter, had better have system of independent special ground connection, notice the other equipment that concerns with PLC also wants reliable ground contact even. When dot of many circuit ground connection joins together, can produce the electricity that expect is less than, bring about logical error or attaint circuit. Produce the account of different ground connection electromotive force, because receive a place to be on physical area,be normally by space too far, when when apart very remote equipment is together by telecommunication cable or sensor join, the electric current between cable and ground can flow via whole circuit, although be inside very short distance, the load current of large facility also can be between its and ground electromotive force generation changes, perhaps produce unpredictable electricity directly through electromagnetism action. Between the incorrect power source that accepts a place, annihilative electricity produces likely in circuit, so that destroy facility. PLC system chooses way of a bit ground connection commonly. Fight to rise in all the model disturbs ability, to imitate signal can use technology of screen float ground, namely the screen layer of signal cable a bit ground connection, signal loop float is empty, with the earth insulation resistance should not be less than 50M Ω . 4, capacitance exists between each lead that eliminates space capacitance to avoid misoperation cable, eligible cable can be limitation of this look value in certain limits. Even if eligible cable, when cable length exceeds certain length, the capacitance of each space allows a value to also can exceed the value of a requirement, when using this cable at PLC to input, space capacitance causes the misoperation of PLC likely, can appear a lot of phenomena that cannot understand. Main show is these phenomena: Bright wiring is correct, but PLC does not have an input however; PLC should some is inputted, and not should some has however, namely PLC inputs mutual interference. To solve this one problem, should treat as: 1, use cable core wrings the cable that closes together; 2, shorten as far as possible the length of use cable; 3, the input mutual interference uses cable apart; 4, use screen cable. 5, the environment of spot of industry of interference rejection processing is harsher, existing interference of a lot of frequency of on any account. These interference introduce PLC through the cable that is linked together with spot equipment commonly. Besides ground connection measure, in the design choice in cable and apply facilities labor, should notice to take step of a few interference rejection: 1, imitate quantity signal belongs to small signal, the influence that is disturbed extremely easily by the outside, should choose cable of double deck screen; 2, signal of high speed pulse (if pulse sensor, computation is piled up dish etc) should choose screen cable, prevent foreign interference already, also prevent signal of high speed pulse to believe the interference of date to low n; 3, the telecommunication cable frequency between PLC is taller, should choose the cable that manufacturer offers commonly, in the requirement not high case falls, can choose the cable of double skeining thread that takes screen; 4, imitate line, dc line cannot take a line inside same line chamfer with communication line; 5, derivative screen cable introduces inside control ark must ground connection, answer not to pass wiring terminal to be linked together with equipment directly; 6, communication signal, dc signal and imitate signal cannot common a cable, dynamical cable should lay apart with signal cable. 7, when the spot is safeguarded, the method that solves interference has: Use screen wire cable to getting the line of interference, lay afresh; Code of wave of interference rejection filter is joined in the program. 6, mark inputs output, convenient overhaul PLC is controlling a complex system, what can see is the indicator light with the input output wiring terminal, corresponding relay that fluctuation staggers two rows and PLC number, resemble having the integrated circuit of 10 several feet together. If any person does not see principle graph overhaul breakdown equipment, can be at a loss what to do, the rate that searchs breakdown will be particularly slow. In view of this kind of circumstance, we are expressed one piece according to scale of electric principle graph case, stick on the console of equipment or control ark, indicate the electric equipment symbol that every PLC input outputs terminal number to answer relatively to it, chinese name, namely the function of each pin shows similar integrated circuit. Had this piece of input to output form, can spread out the overhaul to understanding unit process of cargo bandling or the electrician that are familiar with this equipment echelon graph. But not familiar to those pairs of unit process of cargo bandling, for the electrician that won't see echelon pursue, need again scale a piece of form: PLC input outputs logistic function. This watch explained actually to loop is inputted in major unit process of cargo bandling (spark component, associated component) with output loop (executive component) logistic correspondence concerns. Practice proof if you can use an input adroitly to output corresponding watch and input to output logistic function, overhaul electric breakdown, do not carry blueprint, also can freely easily. 7, conclude through program logic the PLC sort that breakdown often uses on industry now is various, to the PLC of low end, echelon graph dictates very much the same, to in high-end machine, be like S7-300, a lot of programs are written with language watch. Economic echelon plan must have Chinese symbol comment, it is very difficult to be read otherwise, before seeing echelon pursue if can understand equipment technology or unit process of cargo bandling probably, look easier. If undertake electric breakdown is analysed, it is application commonly examine a way instead or say to push a way instead, output corresponding watch according to the input namely, from breakdown the dot finds the output relay of corresponding PLC, begin to examine the logistic impact that satisfies its movement instead. Experience makes clear, examine one department issue, breakdown can eliminate basically, it is not much that because equipment is coinstantaneous,two breakdown that reach above two cases are nodded. 8, sufficient and reasonable use resource of soft, hardware 1, the injunction that do not participate in control to circulate or has thrown before the loop can not receive PLC; 2, when multiple instruction controls a job, but preexistence PLC is exterior an input point will be received again after they are shunt-wound; 3, soft component of in-house function of PLC of make the most of, call mediacy adequately, make the program has complete continuity, develop easily. Also reduce hardware investment at the same time, reduced cost; 4, each output had better become independent below the condition that the condition allows, facilitating control and examination, also protect other to output loop; Meet only when an output nods occurrence breakdown bring about out of control of corresponding output loop; 5, if output is / retrorse pilot is laden, want to be locked up from the first line of a couplet on a scroll of PLC in-house program not only, and should be in PLC is exterior take step, prevent load to be in two direction movement; 6, PLC is urgent stop to should use exterior switch to cut off, in order to ensure safe. 9, other note 1, do not receive line of alternating current source input terminal to go up, lest burn out PLC; 2, earthing terminal should become independent ground connection, do not carry series with other equipment ground connection, area of ground wire cut is not less than 2mm² ; 3, power of auxiliary power source is lesser, the device that can drive small-power only (photoelectricity sensor) ; 4, a few PLC have have check the number a certain quantity ofly (namely terminal of clearing location wiring) , do not receive the line on; 5, when in outputting circuit when PLC, was not being protected, answer to use the protector such as fuse in the series connection in exterior circuit, prevent laden short circuit to cause damage. 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