C74158-A327-E063 6

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
   Dolan-Jenner SS7B351PDO SafeScan Light Curtain Receiver
Pre-Owned
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Dolan-Jenner SS7B351PDO SafeScan Light Curtain Transmitter
Pre-Owned
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Jamesbury ERV-50-01-Q-HR Valve Actuator
Pre-Owned
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
NEW Unbranded 3 Arch Convolution Expansion Joint 3" Diameter 3-5/8" Face-to-Face
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Fanuc A05B-2452-C523 E-Stop Unit Base Assembly
Pre-Owned
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
FOR PARTS Parker P91-5JB-1A0H-4A3 Industrial Computer Workstation
Parts Only
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   York 031-00938D Power Supply Board
Pre-Owned
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Allen Bradley 140068 Motor Control Board Rev   08 Series 1336
Pre-Owned
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   York 031-00809C000 5 Slot Rack Chassis
Pre-Owned
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   York 031-01381-D001 Millennium Integrated Processor / Display Assembly
Pre-Owned
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Unbranded 9 Vane Impeller 2-11/16" Bore 1/2"x1/4"x3-1/4" Keyway
Pre-Owned
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Rexroth DKC06  3-040-7-FW Eco Drive Servo Controller Module without cover
Pre-Owned
   2  432  46
Was:  Previous Price   3  474  95
  
Free Shipping
30% off
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
FOR PARTS Honeywell TVMP-C0-00-AS0-A00-L00-0U000S-00 Multitrend Plus V5 Recorder
Parts Only
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
NEW THK BK15 Ball Screw Unit
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Westinghouse HM2P4XWS10 Shunt Trip Circuit Breaker 400A 600V 2 Pole
Pre-Owned
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   NIMAK AS300B/C Wire Feeder Assembly
Pre-Owned
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
NEW Nordson 1033369 Hot Melt Glue Hose 30 Feet 1500 PSI
Brand New
   2  432  46
  
Free Shipping
2 Watching
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Westinghouse IQ Data Plus II 2D78522 Digital Meter w/ Power Supply & PONI
Pre-Owned
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Yokogawa YS170-001/A31 Programmable Controller S2
Pre-Owned
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
NEW Timken 861 Tapered Roller Bearing Cone
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   General Electric AC362W Flex-A-Plug Bus Plug 60 Amps 600V
Pre-Owned
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
NEW NSK 6315ZC3E Deep Groove Ball Bearing
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Dolan-Jenner SS7B351MDO SafeScan Light Curtain Transmitter
Pre-Owned
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Bucyrus Erie 232269-03 Brake Shoe 232259
Pre-Owned
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Unbranded Underflow Thickening Impeller
Pre-Owned
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
NEW Falk 1090T HUB 710935 Bore 3  375 KW 7/8 x 7/16
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Allen Bradley 1785-L60B PLC-5/60 Processor Module Series C F/W Rev   H
Pre-Owned
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Quartech 9800-AC-AB-0-0 SLC-500 Interface Operator Panel
Pre-Owned
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Allen Bradley 1785-L40B/E PLC-5/40 Processor Module Rev   D01
Pre-Owned
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Post Glover V130-T4-TR6-PG1 PULSERPLUS  NET Grounding System Control Unit
Pre-Owned
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Barber Colman 80EB-10004-001-V-00 Process Module
Pre-Owned
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Allen Bradley 1785-L40B/E PLC-5/40 Processor Module Rev   U01 F/W Rev   E  2
Pre-Owned
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Allen Bradley 1785-L40B/C PLC-5/40 Processor Module FW Rev   E
Pre-Owned
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   ABB 3HAC 14757-1/03 Serial Measurement Board for IRB 6400R M2000
Pre-Owned
   2  432  46
Was:  Previous Price   3  474  95
  
Free Shipping
30% off
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
NEW Falk 0706055 12F SteelFlex Coupling Grid
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
NEW Magnetrol 30-030-2163-002 EZ Modulevel Rev   AP 06
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Furnas VeeArc MCG411K1 Micro7000 Adjustable Frequency Drive 7  5 HP
Pre-Owned
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Allen Bradley 1785-L40B/E PLC-5/40 Processor Module Rev   L01
Pre-Owned
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Mizar Inc   0138301 Serial I/O Adapter Card Rev   J3/C6
Pre-Owned
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Allen Bradley 1785-L40B/C PLC-5/40 Processor Module FW Rev   N  1
Pre-Owned
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
NEW Kingsbury 363625-002-D2 Thrust Bearing Cage
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Allen Bradley 1785-L40B/E PLC-5/40 Processor Module Rev   H01
Pre-Owned
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Allen Bradley 1785-L40B/D PLC-5/40 Processor Module FW Rev   B
Pre-Owned
   2  432  46
  
Free Shipping
Only 1 left!
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Allen Bradley 1785-L40B/E PLC-5/40 Processor Module Rev   S01
Pre-Owned
   2  432  46
  
Free Shipping
 Watch
Get fast shipping and excellent service when you buy from    Top-rated sellers
Item image
   Allen Bradley 1785-L60B PLC-5/40 Processor Module Series C F/W Rev   D
Pre-Owned
   2  432  46