smart relay contacts mysteriously burning up
smart relay contacts mysteriously burning up
(OP)
208 3phase w/ neutral service. 3hp 3ph 208-230v motor rarely if ever used to charge hydraulic cylinder. Smart relay control, typical setup used in 100's of locations with similar or identical scenario.
2 outputs (dry contact relay) wired to run traffic lights (120v 60W bulbs) from of 1 leg (through smart relay output) and return to source neutral. Technician verfied .5a on both hot and neutral to light that's on.
4 identical systems, 2 sets of 2 within a few hundred yards of each other, all burning up the plc outputs' contacts.. ..JUST the 120vac (voltage in = L3-N) output that is on is burning up. These (nor any of the others) are being turned on or off, it's pretty much just sitting there on all the time.
The location is within a mile of the ocean, so I'm thinking the air has something to do with it, and maybe a combination of the salty humidity mixed with some harmonics on the neutral, although not sure what might generate harmonics if nothign is sharing source.....?
To my knowledge, there's nothing else on the source, and the only other things on the 120vac circuit are some solenoid valves and a contactor, yet none of which are used.
It's as if the made contacts are just somehow building up contaminant, pushing the contacts apart just enough to arc the 120.
Any thoughts?
2 outputs (dry contact relay) wired to run traffic lights (120v 60W bulbs) from of 1 leg (through smart relay output) and return to source neutral. Technician verfied .5a on both hot and neutral to light that's on.
4 identical systems, 2 sets of 2 within a few hundred yards of each other, all burning up the plc outputs' contacts.. ..JUST the 120vac (voltage in = L3-N) output that is on is burning up. These (nor any of the others) are being turned on or off, it's pretty much just sitting there on all the time.
The location is within a mile of the ocean, so I'm thinking the air has something to do with it, and maybe a combination of the salty humidity mixed with some harmonics on the neutral, although not sure what might generate harmonics if nothign is sharing source.....?
To my knowledge, there's nothing else on the source, and the only other things on the 120vac circuit are some solenoid valves and a contactor, yet none of which are used.
It's as if the made contacts are just somehow building up contaminant, pushing the contacts apart just enough to arc the 120.
Any thoughts?





RE: smart relay contacts mysteriously burning up
RE: smart relay contacts mysteriously burning up
RE: smart relay contacts mysteriously burning up
RE: smart relay contacts mysteriously burning up
In general, there's a possibility that the root cause will eventually turn out to be something not mentioned, and not derivable from the information provided.
RE: smart relay contacts mysteriously burning up
Probly should have mentioned that too huh. sorry about that.
RE: smart relay contacts mysteriously burning up
Indoors? Sheltered at all?
Mike Halloran
Pembroke Pines, FL, USA
RE: smart relay contacts mysteriously burning up
The easiest and most effective remedy is to preheat the filament by letting around 20 percent of rated current flow when relay is open. It is being done all the time.
Saves the bulbs too.
Gunnar Englund
www.gke.org
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RE: smart relay contacts mysteriously burning up
RE: smart relay contacts mysteriously burning up
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RE: smart relay contacts mysteriously burning up
What is you ventilation like? Enclosures within enclosures suggest it is not very good: the rating of your relay contacts will be based on some expected heat rejection to ambient, but if they can't get rid of heat then failure will occur. Heat accelerates corrosion too, doubling the rate for every 10°C rise.
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RE: smart relay contacts mysteriously burning up
The inrush for an incandescent would be a great clue, but the output burns up after a period of being on for several months.
I have a feeling there is some information I'm not getting.
RE: smart relay contacts mysteriously burning up
"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
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RE: smart relay contacts mysteriously burning up
RE: smart relay contacts mysteriously burning up
If contaminated moisture were the problem, it seems like it would be more prevalent on the de-energized, and consequently unheated, relays.