CAM 621-0016
CAM 621-0016
CAM 621-0016
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
SEALED Allen Bradley 1397-MB014 Motor Blower Starter
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
Toyoda / Sanyo Denki MC256-R140/220 Resistor Unit
Pre-Owned
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
Toyoda / Sanyo Denki MC256-R003/090 Resistor Unit
Pre-Owned
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
NEW Flowserve 357204-G 1 750" Dura-Seal Kit 109020
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
Square D KC34125 Circuit Breaker 480VAC
Pre-Owned
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
NEW Omron SP20-DT-D Programmable Controller
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
Toshiba VMCCX2 TOSDIC DCS Interface Card VMCCX21AAA1
Pre-Owned
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
NEW Worthington 232120X1 Air Compressor Inlet Valve Replacement Part
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
NEW Unbranded Seat Ring for Masoneilan Control Valve 37-10174-6A2 3" G-47299-14
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
Xycom 3515 KPM Industrial Control Computer Workstation 3515-A1L214103500V
Pre-Owned
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
Westinghouse MC3800WK Switch 800 Amp Trip 600VAC 250VDC 457D455G29
Pre-Owned
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
Bayside PS1420-010 Horizontal Gearhead 10:1 Ratio MT142-010-003 MTG
Pre-Owned
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
SAF / Paul Wurth CA409-2 / PW409-2 SAFphire Backplane Termination Card
Pre-Owned
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
Fisher Rosemount CL7015X1-A3 Process I/O Board 38A9426X022 Rev E/F
Pre-Owned
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
Fisher Rosemount CL7015X1-A3-37 Process I/O Board 38A9426X022 Rev H
Pre-Owned
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
Fisher Rosemount CL7015X1-A3 Process I/O Board 38A9426X02R Rev J
Pre-Owned
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
Fisher Rosemount CL7015X1-A3-33 Process I/O Board 38A9426X022 Rev G
Pre-Owned
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
SAF / Paul Wurth PW-HHT1 Programmable Linear Controller Interface
Pre-Owned
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
Honda Engineering PB-200 Weld Schedule Program
Pre-Owned
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
Bosch PE 100 Analog Press Controller Module 0 608 830 093
Pre-Owned
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
NEW Norgren C/511 Quick Exhaust Valve B2425 3/4" NPT
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
Toyoda CPUL2 Servo Amplifier CPU Board TP-2322-3
Pre-Owned
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
Limitorque 21800-028 Geared Limit Switch Assembly
Pre-Owned
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
NEW Masoneilan BUNA-N-NYLON-RPP-4Q-09 Actuator Diaphragm Size 15
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
ITE HJD63F400 Sentron Series Circuit Breaker 400A Frame 400A Trip 600VAC
Pre-Owned
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
NEW Burling Instruments Inc V-1S Temperature Switch 8-1/2" 125-225°F
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
Unbranded 4D Vibration Shock Absorber
Pre-Owned
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
Allen Bradley 42336-172-51 1336 Drive Interface Board Rev E
Pre-Owned
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
Unbranded 4D Vibration Shock Absorber with Housing
Pre-Owned
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
Banner PProCTL PresencePLUS Pro II Controller Module
Pre-Owned
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
Emerson 02-766395-00 Digital Drive Control Board Rev K
Pre-Owned
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
NEW Delta Controls 622-YYY-A-2 5"MPT-AA Direct Inserted Flow Switch
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
Bently Nevada 3500 POSTTTION I/O Module 139554-01
Pre-Owned
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
Pacific Scientific BL2432-24-1-X-005 Permanent Magnet Brushless Servo Motor
Pre-Owned
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
NEW Nordson Heated Hose TC 50 13 Pt100 16 Foot NIB TC-50-13-Pt100 FOR SALE
Brand New
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
Rosemount 8800F015SA1E1D1M5E5R2 Vortex Flowmeter
Pre-Owned
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
NEW Cutler-Hammer D520BP1A2 Power Supply Monitor Module Series A2
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
NEW Agastat 7012ACH2 Timing Relay Module 120V 1 5-15 Seconds
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
Bently Nevada 3500/42M Proximator/Seismic Module PWA 140734-02 Rev M
Pre-Owned
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
Bently Nevada 3500/50 Tachometer Module PWA 133388-02 Rev D
Pre-Owned
1 737 47
Free Shipping
Watch
Get fast shipping and excellent service when you buy from Top-rated sellers
Item image
NEW SKF 7219 BEA/G Angular Contact Roller Bearing
1 737 47
898995850
