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Registered Member #1159
Joined: Fri Dec 07 2007, 02:10AM
Location: Hudson Valley of NY State
Posts: 84
My 125 KV @300 ma X-Ray transformer is coming together. I got the tank back from the body shop, painted & free od dents & dings. Amazing what you can get for a case of COORS Lite . I picked up 2 five gallon cans of SHELL DIALA A when I was on long Island & have everything to put it back together.
Discounting resistive heating elements, what is the easiest way to current limit this beast? I'm thinking one or more 500' roll(s) of THHN in 10 or 12 gauge wire & use small bundles of insulated coat hanger wire inserted into the core(s) to vary inductance. I'd like to limit the primary current to 50 Amps or less. Primary voltage is 240. I guess #10 might be OK for short runs.
I do have a large autotransformer from the X-Ray controller that is wound with heavy gauge wire, but it's really heavy & I'd rather not lug it around.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Well you can always use some shorted MOTs for initial testing, 50A would be 2 to 3 shorted mots in parallel. Or if you have more mots you can put two in series on each "string" then parallel these strings to get the current you need. Configured like this they should stand at least a minute of short-circuit operation.
It is also possible to configure even number of mots as saturable reactor. (but I don't think these work as most of you think, however it should work as a crude variable ballast).
Registered Member #477
Joined: Tue Jun 20 2006, 11:51PM
Location: Seattle, WA
Posts: 546
Sweet!! Can't wait to see some sparks, Bob!
I once put two 500' spools of #10 from Home Depot in series and applied 240V. The current was about 40A. However, 1000' of #10 gets pretty warm pretty quickly at 40A! Definitely for short runs only! For better results, you might try a couple of hundred turns of some heavier gauge wire with a more substantial core as you suggest. One recipe was given on TCML some time ago: I'm working on the same essential thing right now using part of a large transformer core.
Registered Member #160
Joined: Mon Feb 13 2006, 02:07AM
Location: Melbourne, Australia
Posts: 938
That's 37.5 kW !! What are you going to use that puppy for?? Obviously not a Tesla coil. I think your best bet would be to use the controller since you have it, I can't imagine the transformer would be any lighter to lug around, or the ballast that you would need to build. Got any pictures of the baby?
Registered Member #1408
Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679
Home Depot is getting pricey. Those spools are now in the $50+ range..... MOTs can be free.
There was someone who mentioned an automotive alternator spool or something similar. But you need size! I'd start to think price vs size. IF you could find one a junked arc welder x-former (shorted) you might get what you need in one shot.
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Simple current liniting ballast ??
. I picked up 2 five gallon cans of SHELL DIALA A when I was on long Island & have everything to put it back together. 
