[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [TCML] Pig Ballasting...
I located a local source of X-ray transformers and ended up overvolting a few of them, so I decided to salvage something useful out of them instead of letting them become boat anchors.
David
------------------------------
On Sun, Oct 28, 2012 2:44 PM CDT Travis Tabbal wrote:
>Good thoughts, but how does one locate scrapped transformers? Seems like a
>rather speciality type item.
>On Oct 27, 2012 6:28 PM, "drieben" <drieben@xxxxxxx> wrote:
>
>> Travis,
>>
>> If you could get your hands on an scrapped out decent sized
>> transformer, say like 10 kVA, and wind your own windings
>> on it, this would tend to minimize the eddy current heating,
>> as transformer cores are specifically designed to minimize
>> this.
>>
>> I ended up getting the core from a scrapped out x-ray
>> transformer to build mine. This core was is two "C's"
>> and I had to install some no-ferrous spacers between the
>> two "C" halves to get the desired current control. With
>> no spacing, there was not enough current flow, even into
>> dead short. With too much spacing, the current would
>> go too high, so I placed an AC clamp-on ammeter on
>> it and kept adjusting the spacing until I got the desired
>> current flow into a dead short. Seems like I ended up
>> with about 3/8" spacing to get the current flow that I
>> wanted (around 100 amps for me ;^). I wound each
>> "leg" of one of the "C's" with about 110 turns of #6
>> THNN copper cable and ran them in parallel. IIRC,
>> the core cross section is about 11 square inches and
>> this makes for a very robust ballast that's never gotten
>> even noticably warmer than ambient temperature through
>> all of my abuse ;^)
>>
>> Maybe this will give you some ideas,
>> David
>>
>> ----- Original Message ----- From: "Travis Tabbal" <travis@xxxxxxxxxx>
>> To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
>> Sent: Saturday, October 27, 2012 9:50 AM
>> Subject: Re: [TCML] Pig Ballasting...
>>
>>
>> Thanks for the info Joe. I was wondering what you got for current when
>> running as an air core.? I saw one post last night where someone just used
>> the spool of wire as it came from Home Depot and it didn't get too hot. I
>> seem to recall the current being about 20 amps. I'm tempted to try it just
>> to see what it does.
>> On Oct 27, 2012 7:53 AM, "Joe Mastroianni" <joe@xxxxxxxxxxxxxx> wrote:
>>
>>
>>> I did what you are suggesting, only I used 500' of 10GA. I made a spool
>>> out of 2" PVC with some flat polycarbonate scraps glued on the ends (but
>>> not blocking the interior hole of the PVC) to hold on the wire. The
>>> spool
>>> is about 18" long. Took quite a bit of muscle to wind.
>>>
>>> I experimented with different configurations for the core. I had a
>>> couple
>>> 8' rods of aluminum and steel that I cut up into 2" sections. Generally
>>> speaking the forces want to pull the rods into the core, not visa versa.
>>> If you do the math you see it doesn't matter which way the current is
>>> flowing in the solenoid, so it doesn't matter that it's AC, then, either.
>>>
>>> The real issue you face is heating of the core materials. My pig is only
>>> rated at 5KVA so I rarely pushed it above 10. And in any case at 6kVA I
>>> was getting ground strikes so I didn't feel the need for much more. I
>>> was
>>> measuring the input V and I to the variac, as well as the output, and
>>> shoving things into and out of the ballast core to get reasonable levels.
>>> But those interior rods got really hot, probably because I just threw
>>> them
>>> in there, but also probably because the eddies in some of the materials
>>> were severe.
>>>
>>> And the core would stay hot for a long time. I never melted through the
>>> PVC, but I was close. I'm not sure the best way to cool it down as I
>>> switched to DR coils and didn't experiment much more with that.
>>>
>>> Cheers,
>>> Joe
>>>
>>>
>>> On Oct 26, 2012, at 10:27 AM, Travis Tabbal wrote:
>>>
>>> > I've seen a number of options in the archive. I was just wanting to get
>>> > input on what I wanted to try to make sure I'm not off the deep end
>>> > somewhere before I mess with it. Piggy is 14.4kV 10kVA.
>>> >
>>> > I was thinking of getting a 500' spool of AWG12 THHN wire from Home >
>>> Depot
>>> > or similar and winding it around a 2" PVC or similar tube, about 1.5ft
>>> > winding length. Then getting some ferrous wire from there as well,
>>> perhaps
>>> > something like the little yard flags or something from the fencing
>>> > department for the core. I'd pot the core material inside a smaller >
>>> tube,
>>> > even just as a mandrel, with epoxy or similar (Bondo?). With a threaded
>>> rod
>>> > at the top of the potting for adjustment. Then just build a frame to >
>>> hold
>>> > it together while in operation, seems like the cycling of the magnetic
>>> > field from the 60Hz AC might want to push the core out otherwise?
>>>
>>> ______________________________**_________________
>>> Tesla mailing list
>>> Tesla@xxxxxxxxxx
>>> http://www.pupman.com/mailman/**listinfo/tesla<http://www.pupman.com/mailman/listinfo/tesla>
>>>
>>> ______________________________**_________________
>> Tesla mailing list
>> Tesla@xxxxxxxxxx
>> http://www.pupman.com/mailman/**listinfo/tesla<http://www.pupman.com/mailman/listinfo/tesla>
>>
>>
>> ______________________________**_________________
>> Tesla mailing list
>> Tesla@xxxxxxxxxx
>> http://www.pupman.com/mailman/**listinfo/tesla<http://www.pupman.com/mailman/listinfo/tesla>
>>
>_______________________________________________
>Tesla mailing list
>Tesla@xxxxxxxxxx
>http://www.pupman.com/mailman/listinfo/tesla
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla