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1、PLC QUESTIONPLC which should pay attention in the application is specially the control device which serves for the industrial production, usually does not need to take any measure, may use directly in the industry environment. But, when the production environment is too bad, the electromagnetic inte
2、rference is special intense, or installs uses improper, cannot guarantee PLC the normal operation, therefore should pay attention to the following question in the use. First, installment and wiring(1) The power line, the pilot wire as well as the PLC power line and the I/O line should distinguish th
3、e wiring, between the insulating transformer and PLC and I/O should use the double rubberized wire connection.(2) PLC should be far away from the strong jamming source like electric welding machine, the high efficiency silicon rectifier unit and the large-scale power equipment, cannot install with t
4、he high-pressured electric appliance in the identical switch cabinet. (3) The input and output of PLC are best separate the line, the switch quantity and the simulation quantity must separate the placing. The simulation quantity signals transmission should use the shielded wire, the shielding layer
5、should an end or the both sides earth, and the earth resistance should be smaller than the shielding layer resistance 1/10. (4) The PLC elemental area and the expansion unit as well as functional modules ties cable should lie alone, prevents the outside signal the disturbance.(5) The exchange output
6、 line and the direct-current output line do not use the identical root electric cable, the output line to be far away from the high tension line and the power line as far as possible, avoids parallel. Second, I/O end wiring 1. Input wiring (1) inputs the wiring not to surpass 30 meters generally. Bu
7、t if the environment disturbance is small, when the loss of voltage is not big, the input wiring may suitable long. (2)Inputs/the output line not to be able to use the identical root electric cable, the input/output line to be separated. (3)Uses the normally opened contact form to connect the input
8、end as far as possible, causes the establishment the trapezoidal chart to be consistent with the relay schematic diagram, is advantageous for reading. 2. Outgoing junction (1) The out-put wiring divides into the independent output and the public output. In not group, may use the different type and t
9、he voltage class output voltage. But can only use the identical type, the identical voltage class power source in the identical groups output. (2) Because the PLC output element is sealed on the print circuit wafer, and connects to the terminal strip, if will connect output elements load short circu
10、it, will burn down the print circuit wafer, therefore, application fuse protection output element. (3)Uses when the relay outputs, withstands inductive loads size, will affect relays service life, therefore, time use inductive load the selective relay working life must be long. (4) The PLC output lo
11、ad possibly has the disturbance, must therefore take the measure to control, if direct-current outputs after flow guarantees protects, the exchange output anti- accommodates the absorbing circuit, the transistor and the bidirectional thruster output by-passed resistor protection.Third, outside secur
12、ity electric circuit to guarantee that the overall system can under the secure state the reliable work, avoids, because the external power supply breaks down, PLC to present the heavy economic loss which and the person casualty exceptionally, the disoperation as well as outputs by mistake creates, P
13、LC the outside should install the essential protection circuit. (1) Stops the electric circuit anxiously. Regarding can cause the user to cause the damage the dangerous load, besides performs in the control procedure to consider, but also exterior should design the emergency stop electric circuit, c
14、auses when PLC breaks down, can cause the injury load power source reliably to shut off.(2)Fragment. The forward and reverse revolution and so on reversible operations control system must establish the exterior electric appliance interlock protection; the reciprocation moves and rises and falls moti
15、on the control system, must establish the exterior spacing protection circuit.(3)The programmable controller has self-checking functions and so on surveillance timer, when inspects exceptionally, outputs completely the closure. But when programmable controller CPU breakdown cannot control the output
16、, therefore, regarding can cause the user to cause the damage the dangerous load, to guarantee that the equipment moves under the secure state, must design the external circuit to protect. (4) Power source load protection. If the PLC power source breaks down, the interruption interval is short in 10 seconds, PLC works not affected, if the power source interrupt surpasses 10 second or the power source drops surpasses the permissible value, then the PLC
