plc相关问题外文翻译-plc设计(编辑修改稿)

plc相关问题外文翻译-plc设计(编辑修改稿)内容摘要：

mistake creates, PLC 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, 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 operation39。 s control system must establish the exterior electric appliance interlock 外文翻译（ 原文 ） 7 protection。 the reciprocation moves and rises and falls motion the control system, must establish the exterior spacing protection circuit. (3)The programmable controller has selfchecking functions and so on surveillance timer, when inspects exceptionally, outputs pletely 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 overloading39。 s input device. (5) Significant breakdown warning and protection. Regarding easy to have heavy accident39。 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 machine39。 s ground terminal docking, meets the grounding the crosssectional 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, outport39。 s disturbance, should joins the specialpurpose grounding to PLC, the ground point should with the power 外文翻译（ 原文 ） 8 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 hardware39。 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 position. Two CPU module use same user program multitasking, 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 system39。 s cut is also pletes by RPU. Hot backup system in the hot backup system, two CPU with the munication 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. Under a lot of circumstances we are total to like to adopt the string to bine the conversion chip to carry on deliver, under this kind of circumstance not need us 外文翻译（ 原文 ） 9 to carry on to deposited the machine to establish too and plicatedly, but carry on the data exchanges through the data transmission instruction directly, but is not a very viable way in the correspondence, because the PLC of the other party must has been wait for your data exportation at the time of sending out the data, it can39。 t do other works. When you are reading the book, you hear someone knock on door, you stop to start up of affair, open the door and bine to continue with the one who knock on door a dialogue, the telephone of this time rang, you signal hint to connect a telephone, after connecting the telephone through, return overdo e together knock on door to have a conversation, after dialogue plete, you continue again to see your book, this kind of circumstance we are called the interruption to it, it has the authority, also having sex of have the initiative, the PLC had such function .Its characteristics lie in us and may meet the urgently abrupt affairs in the operation process of the equipments, we want to stop to start immediately up of work, the whereabouts。