Bypass Contactor

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sii

Senior Member
Location
Nebraska
I have a 150 hp pulverizer that is started by a Motortronics soft start. The bypass contactor coil is housed in plastic and held in place by a small (compared to the weight of the coil) plastic clip. This plastic clip is broken, allowing the housing to fall out the bottom of the contactor and the part is a few days out. The tech from the manufacturer told me I should just zip-tie the coil into the housing. He said "people do it all the time" which tells me that maybe they should take another look at their engineering but I guess that's not my problem here.

My boss wants me to do it but I'm against it as this unit, if I remember correctly, costs around $8K. It seems foolish to me to take a chance of damaging the unit beyond repair. If it were to come loose again do I run the chance of further damage or would the contactor simply drop out?
 

Cow

Senior Member
Location
Eastern Oregon
Occupation
Electrician
If that coil works itself loose, you stand a pretty good chance of making the contactor chatter. I wouldn't try to ziptie the coil unless I was DAMN SURE it wouldn't come loose.

You blow that contactor apart and you'll wish you were only down for a few days waiting on a plastic clip....

But, if the boss says do it....
 

sii

Senior Member
Location
Nebraska
If that coil works itself loose, you stand a pretty good chance of making the contactor chatter. I wouldn't try to ziptie the coil unless I was DAMN SURE it wouldn't come loose.

You blow that contactor apart and you'll wish you were only down for a few days waiting on a plastic clip....

But, if the boss says do it....

He's pretty reasonable. I just didn't buy the manufacturere rep saying that it wouldn't be a problem.
 

jbelectric777

Senior Member
Location
NJ/PA
"Got Ductape" LOL....... Have your boss sign a "not liable agreement" [that'll go over like a lead balloon] Did I spell "Lead" the right way? Just secure it until your part comes in, even if you take some insulated copper size 12 or 10 solid, drive screws at each end, should be ok. You would be surprised at some things I've been ordered to do !
 

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
If I'm not mistaken, that is an LS (ex LG) contactor and the coil is on a kind of a cassette that slides out of the bottom. The plastic clip holds the cassette in place, the coil itself is always "floating" in the casette in order to be self aligning. Once engaged, the armature extends down into the coil itself, so it would not drop out. The only real danger here is that if the tray slips down while off, the coil will not pull in the contactor when you need it. The Motortronicsw soft starter will not be immediately harmed however, it just means that the heat will begin building up in the enclosure. If your contactor looks like this, you may be able to buy a replacement coil directly from LS or one of ther distributors.

Meta-MECSeriesContactorsTOR_s7.gif


Depending on which Motortronics starter you have, it may or may not "know" that the bypass contactor failed to close: The VMX will, the XL Series will not. the VMX cannot operate very long without the bypass as it was redesigned a few years ago to ALWAYS use it. The XL Series, being older, was not, it has much more heat sink. If you have an XL Series, you can just leave the door ajar, with appropriate warnings and clearances of course. Also don't do this if it's outside or in a wet area!

As a temporary fix I would not hesitate to do the zip-tie fix, all it is doing is keeping the cassette in place. Alternately, you could remove the contactor and flip it over so the coil doesn't drop OUT, it will be held in by gravity.
 
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