电缆选择的敖设
为了减少动力电缆辐射电磁干扰,尤其是变频装置馈电电缆。笔者在某工程中,采用了铜带铠装屏蔽电力电缆,从而降低了动力线生产的电磁干扰,该工程投产后取得了满意的效果。
不同类型的信号分别由不同电缆传输,信号电缆应按传输信号种类分层敖设,严禁用同一电缆的不同导线同时传送动力电源和信号,避免信号线与动力电缆靠近平行敖设,以减少电磁干扰。
4.3硬件滤波及软件抗如果措施
信号在接入计算机前,在信号线与地间并接电容,以减少共模干扰;在信号两极间加装滤波器可减少差模干扰。
由于电磁干扰的复杂,要根本消除迎接干扰影响是不可能的,因此在PLC控制系统的软件设计和组态时,还应在软件方面进行抗干扰处理,进一步提高系统的可靠。常用的一些措施:数字滤波和工频整形采样,可有效消除周期干扰;定时校正参考点电位,并采用动态零点,可有效防止电位漂移;采用信息冗余技术,设计相应的软件标志位;采用间接跳转,设置软件陷阱等提高软件结构可靠。
4.4正确选择接地点,完善接地系统
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。
系统接地方式有:浮地方式、直接接地方式和电容接地三种方式。对PLC控制系统而言,它属高速低电平控制装置,应采用直接接地方式。由于信号电缆分布电容和输入装置滤波等的影响,装置之间的信号交换频率一般都低于1MHz,所以PLC控制系统接地线采用一点接地和串联一点接地方式。集中布置的PLC系统适于并联一点接地方式,各装置的柜体中心接地点以单独的接地线引向接地极。如果装置间距较大,应采用串联一点接地方式。用一根大截面铜母线(或绝缘电缆)连接各装置的柜体中心接地点,然后将接地母线直接连接接地极。接地线采用截面大于22mm2的铜导线,总母线使用截面大于60mm2的铜排。接地极的接地电阻小于2Ω,接地极好埋在距建筑物10~15m远处,而且PLC系统接地点必须与强电设备接地点相距10m以上。信号源接地时,屏蔽层应在信号侧接地;不接地时,应在PLC侧接地;信号线中间有接头时,屏蔽层应牢固连接并进行绝缘处理,一定要避免多点接地;多个测点信号的屏蔽双绞线与多芯对绞总屏电缆连接时,各屏蔽层应相互连接好,并经绝缘处理。选择适当的接地处单点接点。
PLC控制系统中的干扰是一个十分复杂的问题,因此在抗干扰设计中应综合考虑各方面的因素,合理有效地抑制抗干扰,对有些干扰情况还需做具体分析,采取对症下药的方法,才能够使PLC控制系统正常工作。
Reliance Electric VS Drive SP 500 M/N 1SU41001
RELIANCE ELECTRIC 57408 POWER MODULE INTERFACE (NIB)
RELIANCE ELECTRIC 48267 C RESISTOR DYNAMIC BRAKING NIB
RELIANCE ELECTRIC 2TC3075 NSFP 2TC3075
Reliance Electric GV/3000 SE 5V4460 5Hp NEW
2X RELIANCE ELECTRIC 14C11 MINIPAK PLUS DC DRIVE 1.5HP
RELIANCE ELECTRIC 69330-3A NSFP 693303A
RELIANCE ELECTRIC FIELD REGULATOR MODULE 57412 57412-E
RELIANCE ELECTRIC 1/3HP AC MOTOR FBP FRAME 1725RPM
NOS RELIANCE ELECTRIC BRAKE COIL 413366-AH 30/460V 60HZ
RELIANCE ELECTRIC GV6000 AC DRIVE 3 HP 3 PHASE
RELIANCE ELECTRIC REEVES 9205 X-V PULLEY 1-1/8 H95509
RELIANCE ELECTRIC 418285-112A VCRB-1A CONTROL BOARD NEW
Reliance Electric BDC-25L Brushless Amplifier
Reliance Electric 0-48680-117 Regulator Board GP 2000
New Reliance Electric Remote Operator Adapt Kit 14C220
Expedited shipping available
Reliance Electric AC Drive Model 6MDDN-2P3101
Expedited shipping available
reliance electric flexpak 3000 75/150 HP DC DRIVE
RELIANCE ELECTRIC KP-H330 BLOWER 1/10HP
RELIANCE ELECTRIC PATCH
RELIANCE ELECTRIC GV6000 AC DRIVE 7.5HP
Reliance Electric Output Module 57C403
Reliance Electric VTAC 7 HVAC DRIVE
RELIANCE ELECTRIC CALIBRE 13.5 HP ELECTRIC MOTOR
**NIB** Reliance Electric Analog Input 61C542A
Expedited shipping available
RELIANCE ELECTRIC 69932-218 CAPACITOR LOT OF 6
Reliance Electric SP500 VS AC Drive 1 HP 230V…
Reliance Electric 5-24 VDC Output Module 57C420
RELIANCE ELECTRIC 418285-113A PSBD-4A CONTROL BOARD NEW
Enlarge
RELIANCE ELECTRIC 418283-81A TRBD-1 CONTROL BOARD NEW
Enlarge
Reliance Electric 0-52806-1 TLOB Tach Loss Overspeed
RELIANCE ELECTRIC 418285-112A VCRB-1A CONTROL BOARD NEW
Enlarge
RELIANCE ELECTRIC 418285-79A MAPS-1 CONTROL BOARD
Enlarge
RELIANCE ELECTRIC 0-52808-2 (OLVC) GOOD TAKEOUT
Reliance Electric Power Matched DC Motor! 8318A
RELIANCE ELECTRIC 50 H.P. MOTOR , 575V , 890 RPM NEW
RELIANCE ELECTRIC RECTIFIER STACK 86466-74RD
Expedited shipping available
RELIANCE ELECTRIC MOTOR 125 H.P. 575V , 1785 RPM USED
RELIANCE ELECTRIC MOTOR 25 H.P. , 575V, 1180 RPM , NEW
Reliance Electric 1SU51001 1HP SP500 VS Drive 1 HP NIB
RELIANCE ELECTRIC MOTOR 50 H.P. , 575V , 1185 RPM , NEW
RELIANCE ELECTRIC MOTOR 60 H.P. , 575V , 1185 RPM NEW
I.D. # P40G04758
RELIANCE ELECTRIC 0-57412 DCS FIELD REGULATOR
RELIANCE ELECTRIC MOTOR 60 H.P. 575 V , 1185 RPM NEW
RELIANCE ELECTRIC MOTOR 75 H.P. , 575 V , 1185 RPM NEW
**FS** Reliance Electric Analog Input 61C542A
Expedited shipping available
RELIANCE ELECTRIC MOTOR 75 H.P. , 575 V , 1780 RPM NEW
RELIANCE ELECTRIC IMPAK ADJUSTABLE FREQUENCY DRIVE 8C10
Reliance Electric 5-24 VDC Input Module 57C419
RELIANCE ELECTRIC P44G0362N 125 HP FR. 444TS MOTOR NEW
RELIANCE ELECTRIC P44G0362N 125 HP FR. 444TS MOTOR NEW
NEW RELIANCE ELECTRIC 9C42 QD POTENTIOMETER KIT 9C42
Expedited shipping available
Reliance Electric 57408-C Power Module Interface NEW
One-day shipping available
MK-1207 RELIANCE ELECTRIC MAXPAK 3 VS DRIVE












