3HAC8081-11
3HAC8081-11
【工控小知识】
PLC控制系统主要抗干扰措施
(1)电源的合理处理,抑制电网引入的干扰对于电源引入的电网干扰可以安装一台带屏蔽层的变比为1:1的隔离变压器,以减少设备与地之间的干扰,还可以在电源输入端串接LC滤波电路。
(2)正确选择接地点,完善接地系统良好的接地是保证PLC可靠工作的重要条件,可以避免偶然发生的电压冲击危害。接地的目的通常有
两个,其一为了安全,其二是为了抑制干扰。完善的接地系统是PLC控制系统抗电磁干扰的重要措施之一。
PLC控制系统的地线包括系统地、屏蔽地、交流地和保护地等。接地系统混乱对PLC系统的干扰主要是各个接地点电位分布不均,不同接地点间存在地电位差,引起地环路电流,影响系统正常工作。例如电缆屏蔽层必须一点接地,如果电缆屏蔽层两端A,B都接地,就存在地电位差,有电流流过屏蔽层,当发生异常状态如雷击时,地线电流将更大。
此外,屏蔽层、接地线和大地有可能构成闭合环路,在变化磁场的作用下,屏蔽层内又会出现感应电流,通过屏蔽层与芯线之间的耦合,干扰信号回路。若系统地与其他接地处理混乱,所产生的地环流就可能在地线上产生不等电位分布,影响PLC内逻辑电路和模拟电路的正常工作。PLC工作的逻辑电压干扰容限较低,逻辑地电位的分布干扰容易影响PLC的逻辑运算和数据存储,造成数据混乱、程序跑飞或死机。模拟地电位的分布将导致测量精度下降,引起对信号测控的严重失真和误动作。
安全地或电源接地:将电源线接地端和柜体连线接地为安全接地。如电源漏电或柜体带电,可从安全接地导入地下,不会对人造成伤害。
系统接地:PLC控制器为了与所控的各个设备同电位而接地,叫系统接地。接地电阻值不得大于4Ω,一般需将PLC设备系统地和控制柜内开关电源负端接在一起,作为控制系统地。
信号与屏蔽接地:一般要求信号线必须要有的参考地即“单点接地”,屏蔽电缆遇到有可能产生传导干扰的场合,也要在就地或者控制室接地,防止形成“地环路”。
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Centum XL Power Supply Unit | PS63*A
PS71*A Centum XL Power Supply | PS71*A
PW301
Centum XL Power Module | PW301
PX1*A
Centum XL Sequencer Interface Card | PX1*A
RS81*B
Centum XL Interface Card | RS81*B
SI11*B Centum XL Station Internal Communication Card | SI11*B
ST5*A
Centum XL Multipoint Status I/O Card | ST5*A
ST6*A
Centum XL Multipoint Status Input Card | ST6*A
ST7*A
Centum XL Multipoint Status Output Card | ST7*A
VM1*D
Centum XL Multipoint Analog I/O Card | VM1*D
VM2*D
Centum XL Multipoint Analog I/O Card | VM2*D
AS S919
Micro XL Keyboard-Video Module | AS S919
BC1*A
Micro XL BRAIN Communication Card | BC1*A
CP81B*B
Micro XL MOPS - MOPL Processor Card | CP81B*B
CP81B*C
Micro XL MOPS - MOPL Processor Card | CP81B*C
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Micro XL MOPS - MOPL Processor Card | CP81E*A
DP88*A
Micro XL MOPS - MOPL Display Card | DP88*A
DP88*C
Micro XL MOPS - MOPL Display Card | DP88*C
DP88*D
Micro XL D MOPS - MOPL Display Card | DP88*D
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Micro XL MOPS - MOPL Display Card | DP88B*A
EA0*A
Micro XL Signal Conditioner - Output Isolator Card | EA0*A
EA1*A
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EC0*A
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EN83*A
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ET5*A
Micro XL Signal Conditioner - T/C Input | ET5*A
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HD82B*A
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KB83*A
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KB92*A Micro XL Keyboard | KB92*A
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LC82*A
Micro XL Redundant RL-Bus Interface Card | LC82*A
LC82*B
Micro XL Redundant RL-Bus Interface Card | LC82*B
LCS*C
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MAC2*B
Micro XL Multipoint Analog Control Card | MAC2*B
MAC2*C
Micro XL Multipoint Analog Control Card | MAC2*C
MF89*A
Micro XL MOPS Power Supply | MF89*A
MF89*B
Micro XL MO