发布时间 : 星期四 文章(完整版)基于PLC的电镀生产线控制系统设计本科毕业设计更新完毕开始阅读9b8a38c303d276a20029bd64783e0912a2167caa
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, causes 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 operation's control system must establish the exterior electric appliance interlock protection; the reciprocation moves and rises and falls motion 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, 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 stop work, all output also separates; when the power source restores, if RUN input connection, then
operates carries on automatically. Therefore, to establish the essential current limiting protection circuit to some easy over-loading's input device. 5. Significant breakdown warning and protection. Regarding easy to have heavy accident's place, to guarantee the control system when the heavy accident occurs still the reliable warning and the protection, should have with the significant breakdown the contacting signal to output through the external circuit, caused the control system to move under the safe condition. Fifth, PLC earth. The good earth is guaranteed that the PLC reliable work the important condition, may avoid the heterogametic the voltage surge harm. PLC meets the grounding and machine's ground terminal docking, meets the grounding the cross-sectional area should not to be smaller than 2mm2, the earth resistance is smaller than 100Ω; If must use the expansion unit, its ground point should accept after checking with the elemental area earth in the same place. In order to suppress adds in the power source and the input end, out-port's disturbance, should joins the special-purpose grounding to PLC, the ground point should with the power equipment (for example electrical machinery) the ground point separate; If cannot meet this kind of requirements, must achieve with the other equipment public earth, forbids to establish contacts the earth with other equipment. The ground point should approach PLC as far as possible.
Sixth, the redundant system and hot backup system in profession in and so on petroleum, chemical industry, metallurgy certain systems, the request control device has the extremely high reliability. If the control system breaks down, will create the production suspension, the raw material massive wastes or the equipment trouble, will create the enormous economic loss to the enterprise. But depends on the enhancement control system hardware's reliability to satisfy the above request is only not enough, because the PLC itself reliable enhancement has certain limit. Uses the redundant system or the hot backup system can solve the above problem quite effectively. 1. Redundancy control system in redundancy control system, entire PLC control system (or in system most important part, if the CPU module) of two set of identical system composition. Two CPU module use same user program multi-tasking, one is advocates CPU, another is spare CPU; advocates the CPU work, but the spare CPU output is forbidden, when advocates CPU breaks down, spare CPU automatic investment movement. This cut process is controlled by the redundancy processing unit RPU, the switching time in 1~3 scanning periods, the I/O system's cut is also completes by RPU.
2. Hot backup system in the hot backup system, two CPU with the communication connection connects in together, which is at circular
telegram condition .When the system presents the breakdown, advocates CPU informs spare CPU to make the spare CPU work. This cut process is not too generally quick, but its structure is simpler than the redundant system.