2023年全國碩士研究生考試考研英語一試題真題(含答案詳解+作文范文)_第1頁
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1、<p>  PLC QUESTION</p><p>  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 u

2、se 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, therefo

3、re should pay attention to the following question in the use. </p><p>  First, installment and wiring</p><p>  (1) The power line, the pilot wire as well as the PLC power line and the I/O line s

4、hould distinguish the wiring, between the insulating transformer and PLC and I/O should use the double rubberized wire connection.</p><p>  (2) PLC should be far away from the strong jamming source like elec

5、tric 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. </p>

6、<p>  (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 signal's transmission should use the shielded

7、 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. </p><p>  (4) The PLC elemental area and t

8、he expansion unit as well as functional module's ties cable should lie alone, prevents the outside signal the disturbance.</p><p>  (5) The exchange output line and the direct-current output line do not

9、 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. </p><p>  Second, I/O end wiring </p><p>

10、;  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. </p><p>  (2

11、)Inputs/the output line not to be able to use the identical root electric cable, the input/output line to be separated. </p><p>  (3)Uses the normally opened contact form to connect the input end as far as p

12、ossible, causes the establishment the trapezoidal chart to be consistent with the relay schematic diagram, is advantageous for reading. </p><p>  2. Outgoing junction </p><p>  (1) The out-put w

13、iring 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 sourc

14、e in the identical group's output. </p><p>  (2) Because the PLC output element is sealed on the print circuit wafer, and connects to the terminal strip, if will connect output element's load short c

15、ircuit, will burn down the print circuit wafer, therefore, application fuse protection output element. </p><p>  (3)Uses when the relay outputs, withstands inductive load's size, will affect relay's

16、service life, therefore, time use inductive load the selective relay working life must be long. </p><p>  (4) The PLC output load possibly has the disturbance, must therefore take the measure to control, if

17、direct-current output's after flow guarantees protects, the exchange output anti- accommodates the absorbing circuit, the transistor and the bidirectional thruster output by-passed resistor protection.</p><

18、;p>  Third, 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

19、 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. </p><p>  (1) Stops the electric ci

20、rcuit 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 whe

21、n PLC breaks down, can cause the injury load power source reliably to shut off.</p><p>  (2)Fragment. The forward and reverse revolution and so on reversible operation's control system must establish the

22、 exterior electric appliance interlock protection; the reciprocation moves and rises and falls motion the control system, must establish the exterior spacing protection circuit.</p><p>  (3)The programmable

23、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, regar

24、ding 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. </p><p>  (4) Power source load pro

25、tection. 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 permissibl

26、e 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 protecti

27、on circuit to some easy over-loadin</p><p>  (5) Significant breakdown warning and protection. Regarding easy to have heavy accident's place, to guarantee the control system when the heavy accident occur

28、s 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.</p&

29、gt;<p>  Fourth, 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 term

30、inal 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

31、 the elemental area earth in the same place. In order to suppress adds in the po</p><p>  Fifth, the redundant system and hot backup system in profession in and so on petroleum, chemical industry, metallurgy

32、 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 cr

33、eate 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 en</p><p>  (1) Redundancy control system

34、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 advocat

35、es 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 proce

36、ssing unit RPU, the switching </p><p>  (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 syste

37、m 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.</p><p>  譯文:PLC 在應用中

38、應注意的問題</p><p>  PLC是專門為工業(yè)生產(chǎn)服務的控制裝置,通常不需要采取什么措施,就可以直接在工業(yè)環(huán)境中使用。但是,當生產(chǎn)環(huán)境過于惡劣,電磁干擾特別強烈,或安裝使用不當,都不能保證PLC的正常運行,因此在使用中應注意以下問題</p><p>  一、安裝與布線  1、 動力線、控制線以及PLC的電源線和I/O線應分別配線,隔離變壓器與PLC和I/O之間應采用雙膠線連接?!?/p>

39、 2、 PLC應遠離強干擾源如電焊機、大功率硅整流裝置和大型動力設備,不能與高壓電器安裝在同一個開關柜內(nèi)?! ?、 PLC的輸入與輸出最好分開走線,開關量與模擬量也要分開敷設。模擬量信號的傳送應采用屏蔽線,屏蔽層應一端或兩端接地,接地電阻應小于屏蔽層電阻的1/10?! ?、 PLC基本單元與擴展單元以及功能模塊的連接線纜應單獨敷設,以防止外界信號的干擾?! ?、 交流輸出線和直流輸出線不要用同一根電纜,輸出線應盡量遠離高壓線和動力

40、線,避免并行。二、I/O端的接線  1、 輸入接線  (1)輸入接線一般不要超過30米。但如果環(huán)境干擾較小,電壓降不大時,輸入接線可適當長些。(2)輸入/輸出線不能用同一根電纜,輸入/輸出線要分開。(3)盡可能采用常開觸點形式連接到輸入端,使編制的梯形圖與繼電器原理圖一致,便于閱讀?!?. 輸出連接 ?。?)輸出端接線分為獨立輸出和公共輸出。在不同組中,可采用不同類型和電壓等級的輸出電壓。但在同一組中的輸出只能用同</p

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