Sudden failure of Contrologix system - any idea why?

rguimond

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I received a call very early this Tuesday morning from the plant. A filler wouldn't go into CIP mode. Tried going on-line from home and found that RSLinx didn't see the processor. Drove to the plant and noticed that the indicator light on the power supply (1756-PA72-C) wasn't illuminated. The circuit beraker supplying it was on and there was 248 VAC present across L1 & L2, so I assumed the power supply was shot. As luck would have it, a factory technician was due that same day for PM service, so we picked up another power supply, installed it and waited for the mechanical service to be complete before turning power back on. At 3:30 PM, it became obvious that we had more serious problems...

First, there was no power to the processor (1756-L61-B). We were able to borrow one from a mothballed plywood mill, but when it was installed, we noticed the Devicenet (1756-DND) and Ethernet (1756-ENBT-A) cards didn't power up, either. After another trip to the mill, we found the Sercos (1756-M08SE) module was also bad, along with two 1756-OB16-E cards and three 1756-IB16-A cards. By this time, it was 1:00 AM on Wednesday, so we knew we were in bad shape.

Miraculously, we were able to find replacements for all the bad cards within a 4-hour drive and were up and running by midnight on Wednesday.

Although I'm pleased to be running, I'm concerned that no root cause was found for the failures and I'm hoping someone may be able to shed some light on the issue.

The filler is powered by a 575-230VAC transformer. The fact that there was 248 VAC across L1&L2 may be an issue, so we moved the primaries from 600 to 575 VAC to drop the secondary voltage.

Even though 248 seems a bit high, I'd be surprised if it caused such a catastrophic failure.

Any ideas?
 
Too easy!

There was no lightning that night. Clear skies. Nothing elese in the plant was affected, either.
 
Nothing elese in the plant was affected, either.
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It only has to hit one time at one place. In your book, how many things have to be hit before it counts?
 
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ID-10-T operator error?
what else is on the power supply I/O
I have had power supplies go bad and take out equipment that they feed think about it if the output is rated 24v and its putting out 13v or 35v what hapens to the equipment it supplies? was there a smell of smoke?lots of possibilites.
I recentley had a plc that kept losing comm cards anolog cards and DIO cards drove me crazy turned out to be a bad ground on a motor the supply leads to it were shorting due to vibration and a nick in the wire they would arc to the conduit at the motor end wich was feeed from an underground pvc pipe that changed to rigid at ground level, the best path to ground was a beldon cable to a level switch .Found it when the motor leads finelly went KA-BOOM.
We still blamed the operator!!! his name was "Nick " LOL
 
There was no lightning that night
Click to expand...
just for refernce there is a web site that shows every lighting strike in your area and time date stamps it.not sure if this the one we used in a law suit involving a failed lightning protection system. wished I still had the link anyone got it?
heres a link like it :
http://www.intellicast.com/Storm/Severe/Lightning.aspx

OH since its AB did you check the ground? LOL
 
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Usually for it to take out all the cards, it generally has to be a pretty high voltage or discharge on the DC of the backplane that feeds all of them. As Lancie says, lightning is a common cause. Another is AC (like 115/230vac) shorting to the DC, sometimes via loose or damaged wiring, sometimes by someone who goofed up and doesn't want to cop to it. I have seen an instance where the PLC power supply had such an extreme failure that it took everything else on the backplane out with it as well.
 
Modern Power Supplies are Switching type. Although designers try to make them as safe as possible, it is possible for them to fail in such a way as to put the incoming Mains Voltage on the regulated DC Outputs. Your Power Supply itself may be your culprit. The higher voltage may have contributed to this, but it is within the +/- 10% usually specified. Only an analysis of the Power Supply will answer that.

Stu....
 
Lightning is electricity with extra female hormones..you just cant tell what it's going to do and where..but's gonna be big !
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Exactly. A strike can hit the main electric line and travel long distances and show up as a voltage surge miles from the strike site. I once worked for the Tennessee Valley Authority (large electric utility) that had lines running over 1000 miles. Lightning was a common event, and usually we could not determine from which storm it originated, but the damage was always severe.

Nothing else in the plant was affected, either.
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This pattern is very familar to me. Your 5 or 6 failed components were MOST likely damaged by a high-voltage spike on the incoming power line, and that spike was most likely caused by lightning. A high-voltage surge is looking for the weakest components through which to go-to-ground. Once the spike is "grounded", no other components may be damaged (so typical of single-strike results that I have seen over the years).

Last fall there was a bumper crop of pecans in the area. My neighbors pecan tree was loaded. The gray squirrels were coming from all around to steal nuts from the tree. Unfortunately the main electric line runs right next to this tree, with several limbs within squirrel jumping distance. One day I happened to be looking out the window as a squirrel jumped between the grounded wire and the top hot 6300 volt line and shorted it out. At the same time there was a voltage surge that burned out my main breaker in my home panel. NOTHING ELSE WAS DAMAGED. That breaker was the weak link.
 
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OK, so the general concensus is that it was lightning.

Can anyone recommend an affordable and effective surge suppressor to prevent this from happening again?
 

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