PLC相关问题外文翻译材料.doc

外文翻译（原文）plc questionabstract: this paper describes the main components of the plc, and attention problems in use (such as the environment in use, the use of pre-note, etc.)central processing unit (cpu) is the brain of a plc controller. cpu itself is usually one of the microcontrollers. aforetime these were 8-bit microcontrollers such as 8051, and now these are 16-and 32-bit microcontrollers. unspoken rule is that youll find mostly hitachi and fujicu microcontrollers in plc controllers by japanese makers, siemens in european controllers, and motorola microcontrollers in american ones. cpu also takes care of communication, interconnectedness among other parts of plc controllers, program execution, memory operation, overseeing input and setting up of an output. plc controllers have complex routines for memory checkup in order to ensure that plc memory was not damaged (memory checkup is done for safety reasons).generally speaking, cpu unit makes a great number of check-ups of the plc controller itself so eventual errors would be discovered early. you can simply look at any plc controller and see that there are several indicators in the form. of light diodes for error signalization. system memory (today mostly implemented in flash technology) is used by a plc for a process control system. aside form. this operating system it also contains a user program translated forma ladder diagram to a binary form. flash memory contents can be changed only in case where user program is being changed. plc controllers were used earlier instead of plash memory and have had eprom memory instead of flash memory which had to be erased with uv lamp and programmed on programmers. with the use of flash technology this process was greatly shortened. reprogramming a program memory is done through a serial cable in a program for application development. user memory is divided into blocks having special functions. some parts of a memory are used for storing input and output status. the real status of an input is stored either as “1”or as “0”in a specific memory bit/ each input or output has one corresponding bit in memory. other parts of memory are used to store variable contents for variables used in used program. for example, time value, or counter value would be stored in this part of the memory. plc controller can be reprogrammed through a computer (usual way), but also through manual programmers (consoles). this practically means that each plc controller can programmed through a computer if you have the software needed for programming. todays transmission computers are ideal for reprogramming a plc controller in factory itself. this is of great importance to industry. once the system is corrected, it is also important to read the right program into a plc again. it is also good to check from time to time whether program in a plc has not changed. this helps to avoid hazardous situations in factory rooms (some automakers have established communication networks which regularly check programs in plc controllers to ensure execution only of good programs). almost every program for programming a plc controller possesses various useful options such as: forced switching on and off of the system input/outputs (i/o lines), program follow up in real time as well as documenting a diagram. this documenting is necessary to understand and define failures and malfunctions. programmer can add remarks, names of input or output devices, and comments that can be useful when finding errors, or with system maintenance. adding comments and remarks enables any technician (and not just a person who developed the system) to understand a ladder diagram right away. comments and remarks can even quote precisely part numbers if replacements would be needed. this would speed up a repair of any problems that come up due to bad parts. the old way was such that a person who developed a system had protection on the program, so nobody aside from this person could understand how it was done. correctly documented ladder diagram allows any technician to understand thoroughly how system functions. electrical supply is used in bringing electrical energy to central processing unit. most plc controllers work either at 24 vdc or 220 vac. on some plc controllers youll find electrical supply as a separate module. those are usually bigger plc controllers, while small and medium series already contain the supply module. user has to determine how much current to take from i/o module to ensure that electrical supply provides appropriate amount of current. different types of modules use different amounts of electrical current. this electrical supply is usually not used to start external input or output. user has to provide separate supplies in starting plc controller inputs because then you can ensure so called “pure” supply for the plc controller. with pure supply we mean supply where industrial environment can not affect it damagingly. some of the smaller plc controllers supply their inputs with voltage from a small supply source already incorporated into a plc.plc 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 interference 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, siemens plc maintenance 1, maintenance procedures, equipment, periodic testing, adjustment provisions (1) half-yearly or quarterly inspection plc cabinet terminal connections, and if time to re-loose strong local connection; (2) of the cabinet to the host power supply voltage of the monthly re-survey work; second, the provisions of cleaning equipment on a regular basis (1) every six months or a quarter of the plc to clean, cut off power to the plc power supply to the power rack, cpu board and input / output board in turn be removed to purge, clean and then in turn installed in situ, will all link to resume evacuation call and start the host plc. plc box carefully sweeping health; (2) every three months to replace the power rack below the filter; three maintenance preparation, maintenance of order (1) ready before maintenance tools; (2) to protect the components and the template does not function no fault damage, must be protection devices and serious preparations for anti-static; (3) maintenance scheduling and operator contact before and well, be linked to overhaul licensing office hung maintenance card; 4, equipment and method of disassembly sequence (1) downtime, must be two or more monitoring operation; (2) the way the cpu on the front panel select switch from the run to stop position; (3) close the plc power supply mains, and then close the other to the power supply module osaka; (4) connected to the power supply rack power cord clear line number in mind and remove the link location, then remove the power rack and rack screws connected, power rack can be removed; (5) cpu motherboard and i / 0 board in the bottom of the screw rotation after template removed; (6) installed in reverse order; 5, maintenance process and technical requirements (1) measure voltage, use a digital voltmeter or accuracy of 1% of the multimeter, measure (2) the power rack, cpu board can only be removed when the main power cut off; (3) ram module to remove or insert the cpu from the cpu prior to disconnect the pcs power supply, so as to ensure the data is not confused; (4) before removing ram modules, check the battery module is working correctly, if the battery fault light is removed when the pam module content will be lost; (5) input / output board should be removed before the first turn off the mains, but if the production of necessary i / 0 boards can be removed at run-time programmable controllers, but the cpu board qvz (overtime) lights; (6) pluggable template, to be more careful, gently, and the goods shipped out of static electricity; (7) the replacement of components not live action; (8) maintenance must be placed after the template installed in place second, installment and wiring(1) the power line, the pilot wire as well as the plc power line and the i/o line should distinguish the 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 the 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 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 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. third, i/o end wiring 1. input wiring (1) inputs the wiring not to surpass 30 meters generally. but 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 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 the 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 circuit, 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 load 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.fourth, outside security 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, 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 operations 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-loadings input device.(5) significant breakdown warning and protection. regarding easy to have heavy accidents 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 machines ground terminal docking, meets the grounding the cross-sectional area should not to be smaller than 2mm2, the earth resistance is smaller than 100; 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-ports 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 hardwares 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 13 scanning periods, the i/o systems cut is also completes by rpu.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.under a lot of circumstances we are total to like to adopt the string to combine the conversion chip to carry on deliver, under this kind of circumstance not need us to carry on to deposited the machine to establish too and complicatedly, 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 cant 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 combine 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 come together knock on door to have a conversation, after dialogue complete, 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 manages the more important affair, this kind of circumstance is we usually meet of, plc while carry out urgent mission, total will keep the current appearance first, for example the address of the procedure, cpu of tired add the machine data etc., be like to stick down which the book that we see is when we open the door the page or simply make a mark, because we treat and would still need to continue immediately after book of see the behind. the cpu always does the affair that should do according to our will, but your mistake of give it an affair, it also would be same to do, this we must notice.the interruption is not only a, sometimes existing jointly with the hour several inside break, break off to have