DeviceNet

[Daval]

Our plant uses DevieNet as an interface from our motors to our DCS. What happens is sometimes during summer we have a couple of motors, a select three on different MCC's that give us problems by randomly shutting down( unfortunately two of these motors will take out the whole front end of the plant) and leaving no details as to why. Was wondering if anybody else had these situations in their plant and what was done to rectify the problem.

 

[gristlehead]

I am a Profibus engineer and know very little about devicenet but I'll try. There are a number of things that could let the motors drop out. What is you devicenet bus voltage doing when the motors are dropping out? How long is the segment from the PLC to the MCC in total length? This could cause bus voltage drop or loss of telegrams if its too long..Are you extending past the limits of devices on this segment of the bus? What do the connectors look like, do you have any tight bends in the Devicenet cable? Are there any ends that are not grounded properly? Does devicenet send out random telegrams to start and stop or is it deterministic? If it is random your stop command intended for another motor on that segment could be stoping you more inportant motor. I hope some of these questions can help point you in the right direction.

 

[DickDV]

Is this a mag starter, constant speed, motor system or is it variable.

It makes a lot of difference.

Actually, is could be solid state softstarting, too.

Please advise which, and what it takes to get the motor to restart.

 

[Daval]

Sorry guys but it is just a normal CH mag starter. We have one motor where last time we had to reconfigure the poni( it had lost its configuration, went back to default)How would it do this? Voltage spike? but another one of our motors will just stop. All it takes to restart is a command from the control room. This is our most troublesome as it happens more frequently without any indication as to why.
gristlehead thanks for the tips we are in conformance with lengths and grounds( I work in the Canadian artic where grounding is questionable at best) , but never really checked V's at time of drop out, and I believe DeviceNet is deterministic.

 

[gristlehead]

Being that all this talks back to your dcs, why don't you set up first out fault alarms. There could be something either unrelated or very related that could be taking you out. Something could be bumping a temp, torque, vibration, limit or set point. You could have something unrelated accidentally linked in the program, very easy to do in a tag based system; I can't tell you how many times I've confused TT6123 for TT6213...

As far as the other device loosing its config, power loss or spike either one could do it. I would be suspect of the device itself. It should hold its config. Possible internal battery failure?

With thinking that both of these are cross the line starters, how old are they? Do they have any noise or chatter to them when picked up? If they do make raquet when energized be aware that it may only take less than 5% voltage drop for the coils to drop out. Take the contactors apart, sand the metal faces of the iron with emory cloth and apply a light coat of machine oil. If this doesn't stop the chatter replace the contactors.

 

[Daval]

These starters are brand spanking new( plant where I work is only 3 years old).... We do a visual PM on all of our starter every 28 days and contacts are checked and cleaned every 56 days(if warrented) No chattering, run smooth as silk.
This may help for further discussions; Originally the baud rate was set for 250. The one starter that drops out more frequently, before the change, was dropping out 4or 5 times a day/night. Then the rate was changed to 125, and now it is only once in awhile. I'm trying to find the network topology so in the next shut down I can really go over this troublesome section.
Voltage drop is not suspect.
And a further FYI, everything at some point has been changed out in that cell. From the starter to the poni to the line drop and the multiport brick. I don't think it is physical. It is something within the Delta V or DeviceNet. I will talk to our Administrator about your first suggestion gristlehead, thanks.

 

[Daval]

I'm sitting here in front of an HMI and looking at the first outs they are there for safety locks and process locks. the control room will tell you that they get no indications as to why the equipment shut down.

 

[djs]

Some answers to the following questions could help resolve the problem. What is the DeviceNet interface inside the starter? Is it an electronic overload? or is it simpily an I/O interface? Does the interface have the capacity to start and/or start the motor (outputs?). If this is an A-B Intellicenter MCC using a CN2DN bridge or some other type of scanner, try turning off ADR.