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2 PLC控制系统中电磁干扰的主要来源
2.1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，其分布较为复杂。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。
2.2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。
（1）来自电源的干扰
Reliance Electric V-S Spindle Drive 355C22D 480VAC 72A
Reliance 150HP DC, 500 volts, 2500 RPM
F&F Koenigkramer Reliance Chair
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USED: Reliance TEFC-XT motor, 250 hp, 3/60/460 volt, 17
Brooks Automation ATR8 Reliance 3 Axis Robot 121655
RELIANCE ELECTRIC 3RA2015 USPP 3RA2015
Reliance 700 HP Electric Motor.
RELIANCE ELECTRIC UVZ3475 USPP UVZ3475
200-300hp Reliance DCS S6R-DIG Power Module 803613-SC
Reliance Electric 86466-3R Rectifier Stack 864663R
One-day shipping available
UNUSED: Reliance TEFC motor, 200 hp, 3/60/460 volt, 178
Reliance Chair and Stand, Complete Lane Package
RELIANCE ELECTRIC 150V4051 USPP 150V4051
RELIANCE ELECTRIC 355C22D USPP 355C22D
Allen Bradley Reliance SD3000 SD3K2004 DC Drive Control
Transfer Pup Trailer Reliance 16 ft 3 Axle
RELIANCE 802220-16VE POWER MODULE **XLNT**
RELIANCE ELECTRIC 86466-3R USPP 864663R
RELIANCE ELECTRIC 7C658 USPP 7C658
RELIANCE ELECTRIC 29274-9SS USPP 292749SS
RELIANCE ELECTRIC 3RA2008U USPP 3RA2008U
RELIANCE ELECTRIC 50R4160 NSPP 50R4160
RELIANCE 6819633/SC2512ATZ DC MOTOR 15HP 53.5A **NEW**
FAIRBANKS MORSE/RELIANCE SUBMERSIBLE PUMPS 100 HP "EXP"
Reliance Electric Motor 200 hp 200hp 1785 RPM NEW
Reliance 493Hp Motor with York Chiller/Compressor Pump
RELIANCE ELECTRIC 3RA2015U USPP 3RA2015U
RELIANCE ELECTRIC 57C-410B USPP 57C410B
NIB Reliance Electric 75R4160 GV 3000 75 HP AC Drive
RELIANCE 803613-RC DCS POWER MODULE S6R DIG 100-150HP
RELIANCE 6SB501-144CNNNB SP600 150HP 575V DRIVE *NIB*