lighting contactor

[kwired]

Are you sure on that?

I have had AC coils burn out because the contactor was mechanically stuck.

I have run into several contactor coils that the plastic encasement melts and jams the armature leaving it stuck closed. Siemens NEMA size 4 contactors in particular is one common one I often have to replace, seems to happen with almost every coil failure - and is hard to remove the old coil when that happens as well.

 

[kwired]

Not really.

Fuses will have to be rated just great enough to allow normal inrush yet blow on surge (a result of overvoltage).

I agree. With as low of a VA rating involved here finding the right fuse for maximum protection yet avoiding nuisance tripping could be a little challenging. That is why motors usually have two types of protection though the load of this coil is more "fixed" during what is normal operation then it is on a motor.

 

[mgookin]

A fuse or breaker spec sheet should give you a waveform or trip curve as to when it's expected to open.
As to the coil on the contactor, some manufacturers give you specs on inrush magnitude but not duration. You can assume its less than time to operate.
To engineer a workaround to the problem using the overload protection process being discussed is going to take some work and it's likely to end in trial and error.
Both overvoltage and undervoltage have been discussed. Are you designing for both?

For 100 years there have been power outages. If it was normal to burn out expensive contactor coils from power outages we would not use the processes we use.
I still say there's an underlying problem. Opening either side of a L1-L2 coil connection is done all the time. That's how the lights are switched.

If there is stray voltage, that needs to be addressed. I'd like to see OP do a test and open each leg one leg at a time and see if there's any voltage from the connected side to the disconnected side of the coil. If there is voltage present, that's a problem that needs to be addressed.
It would also be nice to have some part numbers and voltage readings.
Hypothetical Example: If it's a coil rated 120V connected to 240V maybe the 240V is not enough to kill it on a normal day but if you're getting 260V on power restoration, maybe that is killing it, making the power restoration the common element in coil failure. In this case (and I'm not saying this is the case) the problem would be the wrong coil or improper connection, not the power failure/ power restoration.

 

[GoldDigger]

A fuse or breaker spec sheet should give you a waveform or trip curve as to when it's expected to open.
As to the coil on the contactor, some manufacturers give you specs on inrush magnitude but not duration. You can assume its less than time to operate.
To engineer a workaround to the problem using the overload protection process being discussed is going to take some work and it's likely to end in trial and error.
Both overvoltage and undervoltage have been discussed. Are you designing for both?

For 100 years there have been power outages. If it was normal to burn out expensive contactor coils from power outages we would not use the processes we use.
I still say there's an underlying problem. Opening either side of a L1-L2 coil connection is done all the time. That's how the lights are switched.

But not opening only one line at the service while other loads remain connected!

 

[rippledipple]

contactor

contactor

But not opening only one line at the service while other loads remain connected!

#cutler CN35 elect held,comes on by photo cell.

 

[iwire]

I would go for a mechanically contactor held long before trying to fix it with fuses or suppressors.

 

[mgookin]

But not opening only one line at the service while other loads remain connected!

I understand that. It burns stuff up. We've all seen plenty of it. That's a rare event and a small percentage of outages.
It sounds like from what OP is saying that every time there's an outage he's losing multiple coils. Am I misinterpreting that?

 

[GoldDigger]

I understand that. It burns stuff up. We've all seen plenty of it. That's a rare event and a small percentage of outages.
It sounds like from what OP is saying that every time there's an outage he's losing multiple coils. Am I misinterpreting that?

It also sounds like the OP has been having quite a few outages. Maybe something in common about the mechanism?

 

[kwired]

I understand that. It burns stuff up. We've all seen plenty of it. That's a rare event and a small percentage of outages.
It sounds like from what OP is saying that every time there's an outage he's losing multiple coils. Am I misinterpreting that?

He possibly has only partial outages (like just loss of one ungrounded conductor) but frequently for some reason. Undervoltage relays or phase monitors would help with this situation.

 

[iwire]

I That's a rare event and a small percentage of outages.

Single line outages are pretty common in my area. We are mostly overhead distribution so that may be why.

 

[kwired]

Single line outages are pretty common in my area. We are mostly overhead distribution so that may be why.

very common on rural electric systems, and majority of medium voltage distribution is overhead.

 

[rippledipple]

coil

coil

very common on rural electric systems, and majority of medium voltage distribution is overhead.

The coil is only 120v, i don't think a partial outage would matter.

 

[kwired]

The coil is only 120v, i don't think a partial outage would matter.

For some reason I thought you mentioned a 208 or 240 volt coil. 120 usually don't have those kind of issues but is still potential neutral issues - though if it were a service or feeder neutral gone bad you would probably have many other items with issues.

 

[rippledipple]

suppressor

suppressor

For some reason I thought you mentioned a 208 or 240 volt coil. 120 usually don't have those kind of issues but is still potential neutral issues - though if it were a service or feeder neutral gone bad you would probably have many other items with issues.

I wonder how expensive these transient suppressors are,and how many hits they will take?? And if they will even work in my case??

 

[mgookin]

#cutler CN35 elect held,comes on by photo cell.

The coil is only 120v, i don't think a partial outage would matter.

Here are the Eaton spec sheets. Can you confirm the digit which indicates coil voltage is correct? If the wrong coil is in there and you're using 120V you could be pulling 2x-5x amperage and that might be your problem.

 

[rippledipple]

coil

coil

Here are the Eaton spec sheets. Can you confirm the digit which indicates coil voltage is correct? If the wrong coil is in there and you're using 120V you could be pulling 2x-5x amperage and that might be your problem.


View attachment 15029

View attachment 15030 [/QUOTE only time they burnout is in a power outage

 

[Jraef]

... only time they burnout is in a power outage

In a lot of cases, an outage is PRECEDED by a sag event, often a prolonged one, which then pops a breaker or fuse somewhere to make it an actual outage. The reason it APPEARS as though the coil burns out when power comes back on is because... how would you KNOW until power comes back on? The coils might actually be burning out just before the power completely fails.

 

[Smart $]

Here's a catalog you may want to look over...

http://www.eaton.com/ecm/groups/public/@pub/@electrical/documents/content/vol05_tab06.pdf

 

[Jraef]

The CN35 is just their standard Freedom series contactor, they just rate the contacts a little differently for tungsten loads. The coils are exactly the same as on their motor starters. VA varies by size (we don't know what size these are, do we?), but the voltage tolerance is +10%, -15%; pretty standard for the industry.

Although nobody at Eaton pays me to care, lets face it, they don't make junk and if they had a major problem with coil burn-out on every contactor they made, they would be out of the business. The point is that this is not a product flaw, this is something going on at YOUR facility, and you have to find it. Masking the symptoms by using fuses and/or surge suppressors is just kicking the can down the road.

Oh and coil surge suppressors that go on the coils are to suppress the surges THEY cause for other things on the same circuit. That wouldn't do anything for the coil itself. An SPD at the service entrance would help if it is crap coming in from the utility lines, but if something inside of your facility is making dirty power with lots of spikes, it might not do anything for you. Surge suppressors are really TRANSIENT surge suppressors, but for some reason they stopped calling them that. They don't do a thing for sags and swells , a swell being a slow increase in voltage.

 

[rippledipple]

coil

coil

The CN35 is just their standard Freedom series contactor, they just rate the contacts a little differently for tungsten loads. The coils are exactly the same as on their motor starters. VA varies by size (we don't know what size these are, do we?), but the voltage tolerance is +10%, -15%; pretty standard for the industry.

Although nobody at Eaton pays me to care, lets face it, they don't make junk and if they had a major problem with coil burn-out on every contactor they made, they would be out of the business. The point is that this is not a product flaw, this is something going on at YOUR facility, and you have to find it. Masking the symptoms by using fuses and/or surge suppressors is just kicking the can down the road.

Oh and coil surge suppressors that go on the coils are to suppress the surges THEY cause for other things on the same circuit. That wouldn't do anything for the coil itself. An SPD at the service entrance would help if it is crap coming in from the utility lines, but if something inside of your facility is making dirty power with lots of spikes, it might not do anything for you. Surge suppressors are really TRANSIENT surge suppressors, but for some reason they stopped calling them that. They don't do a thing for sags and swells , a swell being a slow increase in voltage.

Thanks guys!!!!