1、电气工程及自动化专业外文翻译PLC相关问题外文原文：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 microcontroll
2、ers. 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 Americ
3、an 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 (memo
4、ry 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
5、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
6、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
7、 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
8、 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 a
9、lso 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 i
10、ndustry. 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 netwo
11、rks 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 wel
12、l 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 technic
13、ian (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 w
14、ho 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 processi
15、ng 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/
16、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 inp
17、uts 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.P
18、LC 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 s
19、pecial 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 inspect
20、ion 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 pow
21、er 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
22、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 con
23、tact 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 supp
24、ly 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 b
25、ottom 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 of
26、f; (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 los
27、t; (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 o
28、ut 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
29、 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 ele
30、ctric 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
31、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-
32、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 d
33、isturbance 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
