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coillah

Thu Jul 15 2010, 05:45AM

Registered Member #1517 Joined: Wed Jun 04 2008, 06:55AM
Location: Chico CA
Posts: 304

I am building a resistive thermal evaporation system for my vacuum chamber. I was planning on using 0 gauge welding cable to connect the feed-through studs to the power transformer. Is this going to work? I am mostly concerned with the heat as I am pretty sure there will be some serious heat going through there.

~115VAC 10A in
~10 VAC 100-150A out (this is the welding cable side)

Any recommendations, thoughts, suggestions?

radiotech

Thu Jul 15 2010, 03:49PM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546

How long will the cables be and what size/material/threading are the feedthrough studs?

doctor electrons

Thu Jul 15 2010, 08:25PM

Registered Member #2390 Joined: Sat Sept 26 2009, 02:04PM
Location: Milwaukee Wisconsin
Posts: 381

When buying cable, there is a temperature rating on it. I think the most common welding cable has
a rating of 90 degrees C. If you know what temperatures you are expecting the cable to encounter
picking one should be easy. I can tell you some of the higher temp wire and cable is very expensive!
I use a hi temp wire at work quite a bit, its 14awg cloth insulation, about 15 dollars a foot.

coillah

Fri Jul 16 2010, 04:16PM

Registered Member #1517 Joined: Wed Jun 04 2008, 06:55AM
Location: Chico CA
Posts: 304

Feed through studs are copper. The boat inside the chamber is tungsten (usually), and the studs are ~3/4" dia.

The cable will only need to run about 4ft, and the connectors are going to be lugs, beefy lugs.

radiotech

Fri Jul 16 2010, 05:44PM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546

That is big stud for 150 amps. The issue is getting a lug to fit 3/4" yet be crimpable to a flexable cable sized for 150 amps. Also suggest use Bellville washers made of Durium and make sure torque to tighten is establised.

radiotech

Fri Jul 16 2010, 05:57PM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546

Finding lugs crimpable to flexible cable sixed for 150 amps that will fit 3/4" studs will be an issue. Use Durium hardware and bellville washers and establish torque to tighten.

You also might to consider plug connectors at chamber like welding machines use if you need to disconnect frequently to clean or repair,

Edit: excuse double post- first one vanished then re-appeaered, doubtlessly due to my fumbling.

coillah

Fri Jul 16 2010, 06:09PM

Registered Member #1517 Joined: Wed Jun 04 2008, 06:55AM
Location: Chico CA
Posts: 304

Does it sound like the cabling will be enough to support the current? I was hoping to order it this week sometime.

...

Fri Jul 16 2010, 07:22PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

A #0 should be fine, its rated for 150A with a 1 amp/ 700 Circular mils, for short runs you can usually get away with 1/200 which would allow 500A.

klugesmith

Fri Jul 16 2010, 10:22PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

coillah wrote ...
Does it sound like the cabling will be enough to support the current? I was hoping to order it this week sometime.

[edit] #0 wire is a very conservative gauge for 150A, suitable for multiple wires enclosed in a conduit.
In open wiring with free air circulation, AWG4 can carry 150 amps.
Welding references are handy.

For low voltage circuits, you also need to mind the voltage drop.
In an 8 foot loop (4' out and 4' return) of AWG 4, the voltage drop at 150A would be only 0.3 V.

As people have pointed out, for both wire sizes it may be hard to find a ring lug that will fit a 3/4 inch stud.
You could make an adapter out of copper plate or bus bar, with one 3/4 inch hole and a smaller hole for a bolt that fits the wire's lug.

As others have also pointed out, there could be a problem at the vacuum chamber end with heat from the inside.
The high-current feedthroughs will be heated by thermal conduction from the evaporator filament or boat.
The chamber wall will be heated by radiation from the evaporator. I bet that's where most of the electrical input power goes.

coillah

Mon Jul 19 2010, 04:36PM

Registered Member #1517 Joined: Wed Jun 04 2008, 06:55AM
Location: Chico CA
Posts: 304

Yes it's a very engaging project.

The backstreaming of heat is my primary concern. I am probably going to downsize the gauge of the cabling, as it will probably make life a bit easier when it comes to finding connectors and whatnot.

My issue with all of this is the lack of any sort of reading material. I was hoping to run into someone on here with a bit of experience in building these sorts of things who could point me in the direction of literature.

So far the advice has been very productive, thanks guys!

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