iDRY Vacuum Kilns

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See Contactors, See Contactors run off step down coil

Started by slowzuki, May 30, 2006, 01:41:03 PM

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slowzuki

I'll update the mill thread soon too but in the meantime,

I seriously smoked the coil on a very large contactor.  I bought a 200 amp contactor to run my motor so it would be beefy but the coil burned up and smoked.  It heated the whole contactor up so it was too hot to touch.

I'm assuming there was a short in the coil and it started drawing way too much power, wouldn't be caused by the vibrations of being on a mill would it?

I'm wondering if my contactors really have 120 v coils in them not hte stated 240 volt.

Gary_C

The most common reason for a coil on a contactor to fail would be some mechanical restriction that prevents the contactor from moving it's full travel. Ultimately that will cause the coil to overheat and thus fail. Of course applying the wrong voltage to the coil will also do the same thing.  :)

Always check the coil itself for the voltage rating. Coils can be easily changed and the contactor rating has nothing to do with the coil rating. Take the coil out if you have to to see the voltage rating. There will always be a tag directly on the coil.
Never take life seriously. Nobody gets out alive anyway.

slowzuki

I'll give that a shot tonight.  My spare contactor is identical, a siemens it is.  I tried to see the coil voltage on it the other day but couldn't find it.  I took the contacts cover off the top, then the metal shield off the bottom but no dice.

There is a pair of rods that stick through the side, I think they may need removed to really get it open.

beenthere

The contactors on my air conditioner wouldn't "contact" and the service man suggested I look to see if there were any of the Asian beetles that crawled in there. Sure enough, there were. Cleaned them out and it worked fine. Was told that sometimes they cause some arcing and melting of the contacts, but that didn't happen for me.

Don't know this is related to your problem, but reminded me of a possibility.  :)
south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

Gary_C

One other thing to check. Some contactors have multiple voltage coils that can be hooked up for different control voltages. Check the wiring diagram to see if it shows multiple hook up methods.
Never take life seriously. Nobody gets out alive anyway.

slowzuki

Ok so I hauled open my identical spare to check the coil voltage and dun da dun da dunnnn nothing on it.  The model number just repeats the contactor number, a 3TB52

It looks as though a replacment coil is 100$ US so I hope I can locate one with a known voltage.  Aparently the whole contactor is 500$ us to replace :o  I bought the pair for 75$.

I'm searching for the coil impedences for the various coils so I can deduce what mine is and maybe add a resistor to the circuit.

slowzuki

Well my contactor is from the 80's and obsolete so no coil assemblies are around except those in stores own stock.  I'll have to see if I can locate one or try a resistor to knock the voltage back a bit.

Danny_S

how's the mill working anyways? any good pics for us?
Plasma cutting at Craig Manufacturing

slowzuki

Danny how are ya!  Found a step down transformer at the electrical supplier popped it in and went to town on a log!  Now have my first official spruce 2x6 and 6x6 for the building!  Wasted a good 2x6 too by taking off too big a slab on my second turn but we'll get better!

I'll post the pics and more info in the real thread tomorrow!

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