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plc与dcs的分析比较
dcs和plc的设计原理区别较大,plc是由继电器控制原理发展起来的,它以存储执行逻辑运算、顺序控制、定时、计数和运算等操作的指令;并通过数字输入和输出操作,来控
制各类机械或生产过程。用户编制的控制程序表达了生产过程的工艺要求,并事先存入plc的用户程序存储器中。运行时按存储程序的内容逐条执行,以完成工艺流程要求的操作。plc的cpu内有指示程序步存储地址的程序计数器,在程序运行过程中,执行一步该计数器自动加1,程序从起始步(步序号为零)起依次执行到最终步(通常为end指令),然后再返回起始步循环运算。plc每完成一次循环操作所需的时间称为一个扫描周期。不同型号的plc,循环扫描周期在1微秒到几十微秒之间。程序计数器这样的循环操作,这是dcs所没有的。这也是使plc的冗余不如dcs的原因。dcs是在运算放大器的基础上得以发展的。把所有的函数和过程变量之间的关系都做成功能块(有的dcs系统称为膨化块)。dcs和plc的表现的主要差别是在开关量的逻辑解算和模拟量的运算上,即使后来两者相互有些渗透,但是还是有区别。80年代以后,plc除逻辑运算外,控制回路用的算法功能已经大大加强,但 plc用梯形图编程,模拟量的运算在编程时不太直观,编程比较麻烦。但在解算逻辑方面,表现出快速的优点,在微秒量级,解算1k逻辑程序不到1毫秒。它把所有的输入都当成开关量来处理,16位(也有32位的)为一个模拟量。而dcs把所有输入都当成模拟量,1位就是开关量。解算一个逻辑是在几百微秒至几毫秒量级。对于plc解算一个pid运算在几十毫秒,这与dcs的运算时间不相上下。
在接地电阻方面,对plc也许要求不高,但对dcs一定要在几欧姆以下(通常在4欧姆以下)。模拟量隔离也是非常重要的。
相同i/o点数的系统,用plc比用dcs,其成本要低一些(大约能省40%左右)。plc没有专用操作站,它用的软件和硬件都是通用的,所以维护成本比dcs要低很多。如果被控对象主要是设备连锁、回路相对很少,采用plc较为合适。如果主要是模拟量控制、并且函数运算很多,***采用dcs。dcs在控制器、i/o板、通讯网络等的冗余方面,一些高级运算、行业的特殊要求方面都要比plc好的多。plc由于采用通用监控软件,在设计企业的管理信息系统方面,要容易一些。
GE FANUC A06B-6065-H030#H550 Spindle A06B6065H030#H550
GE FANUC Spindle Motor A06B-0780-B100 #3000
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Baldore ID15V250-MO ID15V250MO Variable Torque 50HP
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Allen Bradley 2711-T10C20 /F 2711T10C20 Panelview 1000
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Allen Bradley PowerFlex 700S 20DD027A0EYNANNNA A 20HP
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Emerson FX-8500 FX8500 Positioning Servo Drive
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Allen Bradley 2711P-RP2 /C 2711PRP2 Panelview Plus
Indramat DKC04.3-040-7-FW DKC04.30407FW ECO Drive
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Allen Bradley Digital Servo 1394-SJT10-A /A 1394SJT10A
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ProSoft Allen Bradley 3100-MCM 3100MCM Comm Module
Allen Bradley 1394C-SJT05-D C 1394-SJT05-D
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FANUC A06B-6089-H201 Servo Amplifier A06B6089H201 L Use
GE Fanuc A06B-6093-H114 A06B6093H114 Servo Amplifier
Allen Bradley 1394C-SJT10-D D 1394-SJT10-D
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Modicon Telemecanique BPH1 423N5MA2CA1 BPH1423N5MA2CA1
Bosch Rexroth Indramat HDS03.2-W100N HDS032W100N
Siemens Panel 6AV6 545-0BC15-2AX0 6AV65450BC152AX0
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ABB Drive 3HAB8101-8/08D 3HAB8101808D DSQC346G
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Allen Bradley 2098-DSD-075 /A 2098DSD075 Servo Drive
Allen Bradley 2711P-RP1 /D 2711PRP1 Panelview Plus
Allen Bradley 2094-BC01-M01 /A 2094BC01M01 Axis Module
New GE FANUC A06B-0852-B201 AC Spindle Motor 2.2kW
GE FANUC Servo Amp A06B-6066-H244 A06B6066H244
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New In Box Allen Bradley 2094-BL02 A 2094BL02
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Allen Bradley 2711P-RP1 /B 2711PRP1 Panelview Plus
Allen Bradley PowerFlex 700S 20DD027A0NYNANNNN A
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Allen Bradley 1394C-SJT10-D C 1394-SJT10-D
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NEW Allen Bradley 22B-E012N104 /A 22BE012N104 10 HP
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NEW Foxboro IMT96-SEADB10M IMT96SEADB10M Transmitter
MINT GE Fanuc A06B-6089-H321 A06B6089H321 Servo Amp
Allen Bradley 1394-SJT05-T /A 1394SJT05T Turbo
Allen Bradley Panelview 2711P-RDK10C /A 2711PRDK10C
MINT Pacific Scientific SC753A001-01 SC753A00101 Servo
Allen Bradley Powerflex 70 20AD022C3AYNANNN /A 15HP
Allen Bradley 2711P-RP1 /B 2711PRP1 Panelview Plus
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Allen Bradley 2711P-RP /A 2711PRP
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Allen Bradley Panelview 2711-K10C8 /C 2711K10C8
Emerson FX-4120 Positoning Servo Drive w/ PCM-11 Cntrl
Allen Bradley Ultra 2098-DSD-HV100-SE /B 2098DSDHV100SE
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Allen Bradley Powerflex 400 22C-D022N103 22CD022N103
Emerson Quantum II 9500-8102 Digital DC Drive 20HP
Allen Bradley 2711P-RDT7C /A 2711PRDT7C Panelview Plus
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Allen Bradley Powerflex 70 20AD027A3AYNANC0 /A 20 HP
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Siemens 6AV6 545-0BA15-2AX0 6AV65450BA152AX0 Panel
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Indramat DKC 1.1-030-3 DKC110303 AC Servo Controller
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