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Hi.  We installed 3 x V570 plc's running on ethernet network.  Also connected Indusoft scada system to system.  Delta vsd run also on same network.

All working fine and then sometimes comms to scada stops.  Also comms to VSD's not constant.  If comms to scada laptop fails we have to restart plc's to get comms again.

Any suggestions or help will be appreciated

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Is it possible to temporary sw off (or power of) VFD?

If the problem gone - VFD EMF noise stop comms.

You must check - is it motor GROUND wire and SHIELD of motor cable (if present)  connected to VFD PE    AND VFD PE  connected to the machine or cabinet GND.

Also please read pdf documents posted in my link




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In addition to kratmel's excellent advice, are the PLCs the Master or Slave to the SCADA? If Master, then there are some Ethernet System Operand settings that can improve connection recovery. Also, there are some ladder code techniques that will auto-reconnect when the connection is lost. Can you post your program here?

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Hi. Thanks for answer.  Scada is master.  If scada comms lost plc and drives still have comms be it with short intermittent loss of comms.  second or so.

The program is on laptop in west africa.  Client try to sort it out as we can't travel there to assist.


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What are the details of the actual network?  What kind of switch are you using and what is the environment in which it's mounted?

How long are the cables, and are they store-bought (molded ends) or were they made in the field with the little connectors and a crimp tool?

I've had problems that were "my fault" (there's something wrong with your PLC!) that turned out to be RJ45 contacts turning green on a switch mounted in the ceiling.

For troubleshooting you may want to add indicators to a screen showing the status of some of the Ethernet system bits SB 140..158.  Which ones you care about depends on the socket used for the SCADA system.  You'll also want to tweak some values in SI 100 .. SI 110.

As Flex asked - post your PLC program if you can for better help.  

Joe T.

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