621-6550RC

621-6550RC

621-6550RC

3.PLC控制系统中电磁干扰的主要来源有哪些呢？

  (1)来自空间的辐射干扰

  空间的辐射电磁场（EMI）主要是由电力网络、电气设备的暂态过程、雷电、无线电广播、电视、雷达、高频感应加热设备等产生的，通常称为辐射干扰，其分布极为复杂。若PLC系统置于所射频场内，就回收到辐射干扰，其影响主要通过两条路径；一是直接对PLC内部的辐射，由电路感应产生干扰；而是对PLC通信内网络的辐射，由通信线路的感应引入干扰。辐射干扰与现场设备布置及设备所产生的电磁场大小，特别是频率有关，一般通过设置屏蔽电缆和PLC局部屏蔽及高压泄放元件进行保护。

  (2)来自系统外引线的干扰

  主要通过电源和信号线引入，通常称为传导干扰。这种干扰在我国工业现场较严重。

  (3)来自电源的干扰

  实践证明，因电源引入的干扰造成PLC控制系统故障的情况很多，笔者在某工程调试中遇到过，后更换隔离性能更高的PLC电源，问题才得到解决。

  PLC系统的正常供电电源均由电网供电。由于电网覆盖范围广，将受到所有空间电磁干扰而在线路上感应电压和电路。尤其是电网内部的变化，入开关操作浪涌、大型电力设备起停、交直流转动装置引起的谐波、电网短路暂态冲击等，都通过输电线路到电源边。PLC电源通常采用隔离电源，但其机构及制造工艺因素使其隔离性并不理想。实际上，由于分布参数特别是分布电容的存在，隔离是不可能的。

  (4)来自信号线引入的干扰

  与PLC控制系统连接的各类信号传输线，除了传输有效的各类信号之外，总会有外部干扰信号侵入。此干扰主要有两种途径：一是通过变送器或共用信号仪表的供电电源串入的电网干扰，这往往被忽略；二是信号线受空间电磁辐射感应的干扰，即信号线上的外部感应干扰，这是很严重的。由信号引入干扰会引起I/O信号工作异常和测量精度大大降低，严重时将引起元器件损伤。对于隔离性能差的系统，还将导致信号间互相干扰，引起共地系统总线回流，造成逻辑数据变化、误动和死机。PLC控制系统因信号引入干扰造成I/O模件损坏数相当严重，由此引起系统故障的情况也很多。

Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
NEW Qty   2 Ariel A-14513 Compressor Suction Seat SUC VLV SEAT   80CDX   PRC
   1  633  23
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Square D KH36225861 I-Line Circuit Breaker 225 Amps 480VAC
Pre-Owned
   1  633  23
  
Free Shipping
Only 1 left!
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Kaydon Model 981 Ho   Liquid Filter
Pre-Owned
   1  633  23
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
NEW Bently Nevada 21504-000-020-10-02 7200 Series Proximity Probe
   1  633  23
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
NEW Dixon M30-04A Coalescing Filter w/ Automatic Drain
   1  633  23
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Lot GE AMC6EB Spectra Circuit Breaker Module with 6 THED113020 20 Amps
Pre-Owned
   1  633  23
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
EGS / Appleton Mercmaster III 100W Metal Halide Light Fixture MLSH104G1NMTFTZ2UP
   1  620  02
Was:  Previous Price   2  314  32
  
Free Shipping
30% off
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Northern Telecom NT5D12AG Dual Port DTI / PRI Card RIse 04
Pre-Owned
   1  598  48
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Honeywell 07082-28-00000-000 Conductivity Analyzer no hardware
Pre-Owned
   1  598  48
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
NEW Miller 8814-24/ Adjustable Bean Anchor MFP3969110 12" to 24" Length
   1  598  48
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Square D FI36100 I-Limiter Circuit Breaker 100 Amps 600VAC
Pre-Owned
   1  598  48
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Fisher Rosemount CL6895X1-A1 Smart Device Input Panel 12P0247X032 Rev   C
Pre-Owned
   1  581  10
Was:  Previous Price   2  258  72
  
Free Shipping
30% off
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Westinghouse Emerson 1C31224G01 Ovation Analog Input Module
Pre-Owned
   1  581  10
Was:  Previous Price   2  258  72
  
Free Shipping
30% off
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Westinghouse Emerson 1C31227G01 Ovation Analog Input (Current) Module Rev03
Pre-Owned
   1  581  10
Was:  Previous Price   2  258  72
  
Free Shipping
30% off
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   GE Energy PRC-100 SFP Power Distribution Module 7610086 Rev   1
Pre-Owned
   1  563  73
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   TimeMark 412SP Automatic Reverse Controller 91A00070-01
Pre-Owned
   1  563  73
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Bailey Controls IMCOM03 infi 90 Controller Module
Pre-Owned
   1  563  73
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
NEW Dodge NUP2212ECP  C0/C3 Cylindrical Roller Bearing
   1  563  73
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Square D KAL361751212J Circuit Breaker 175 Amps 600VAC Auxiliary
Pre-Owned
   1  563  73
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Yokogawa FX1A-FP-1A*B Programmable Computing Unit Damaged Foot
Pre-Owned
   1  563  73
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
NEW Hayward 3 Inch Butterfly Valve BYV11020A316VLI
   1  563  73
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Fisher Rosemount CL6842X1-A2 Analog Output Interface 41B7285X022 Rev   G
Pre-Owned
   1  563  73
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Eaton AF-160302-0480 Dynamatic 3 HP Motor Drive 380-480V
Pre-Owned
   1  563  73
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Allen Bradley 20AD5P0A0AYNNNNN PowerFlex 70 Variable Frequency Drive 2/3 HP
Pre-Owned
   1  563  73

  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Fisher Rosemount CL7006X1-A1 Backplane Board 36A4973X012 Rev   B
   Fisher Rosemount CL7006X1 Backplane Board 36A4973X012 Rev   C
Pre-Owned
   1  563  73
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
NEW Dixson 051P Pro Series Programmable Bar Graph +/-7  5 Inches
   1  563  73
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Fisher Rosemount CL6825X1-A2 Provox Smart Device Input 12P0408X072 Rev   J
Pre-Owned
   1  563  73
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
NEW Dixson 051P Pro Series Programmable Bar Graph Pressure Meter 0-500 PSIG
   1  563  73
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Fisher Rosemount CL6825X1-A2 Provox Smart Device Input 12P0408X072 Rev   H
Pre-Owned
   1  563  73
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Allen Bradley 42336-252-51 1336 Drive Main Control Board Rev   8
Pre-Owned
   1  563  73
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Fisher Rosemount CL6825X1-A2 Provox Smart Device Input 12P0408X092 Rev   L
Pre-Owned
   1  563  73
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Brown & Sharpe 80-410-214-2 CMM Machine Connector Board
Pre-Owned
   1  563  73
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Allen Bradley 2706-A11J DL10 Dataliner Display
Pre-Owned
   1  563  73
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
NEW Timken H414210-200502 Tapered Roller Bearing
   1  563  73
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Square D KAL361501021 Circuit Breaker 150A 600VAC Shunt Trip Gray Face
Pre-Owned
   1  563  73
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   PDI PCB07983A 4 Channel Star Modem Board
Pre-Owned
   1  563  73
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Siemens C98040-A1045-P3-26-85 Circuit Drive Board
Pre-Owned
   1  563  73
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Honeywell 620 Series 620-0059 Redundancy Control Module VR 2  2 Rev   R
Pre-Owned
   1  563  73
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Balluff BTL5-E10-M0330-P-S32/US Micropulse Linear Transducer 084808488 US
Pre-Owned
   1  563  73
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Bently Nevada 3300/15 Dual Vibration Monitor 3300/15-02-01-00-00-00-00
Pre-Owned
   1  563  73
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Opto 22 Optomux PB4MD Digital Brain Board 001696C
Pre-Owned
   1  563  73
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   ABB A1004401 NPBSA Module A10043-01 Rev   B
Pre-Owned
   1  563  73