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Re: [TCML] Pig Ballasting...
Question could one parallel the wound ballasts for more current (welding
rod ballast)?
On Sun, Oct 28, 2012 at 4:31 PM, David Rieben <drieben@xxxxxxx> wrote:
>
>
> 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?
> >>>
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