inner Primary proposal
Kolas, Sat Jul 15 2006, 08:25PMOk, I've seen countless TC's of all types with primaries on the outside of the secondary.
This serves it's perpose when the secondary dia is 1-6".
However, what would be the main draw back to putting a primary inside the secondary of say, a 12" secodnary?
I've scrateched the small secondary I asked about stripping yesterday because I found 12.5" pipe.
And I wanted to use as large/tall pipe I could get and this offers just that. So my proposal, since this is a VTTC, is to have a helical priamry inside the secodnary with the secodnary wound as usuall.
Not only would this save on primary winding length, but it would also possibly help reduce the possibility of primary/secodnary flashover.
I apreaciate responses.
Kolas
Re: inner Primary proposal
ped, Sat Jul 15 2006, 08:28PM
an interesting idea, but wouldnt the field be reversed? also i imagine the risk of primary to secondry strike would be higher, as the electrically charged field would be high and concentrated inside the tube of the secondry?
ped, Sat Jul 15 2006, 08:28PM
an interesting idea, but wouldnt the field be reversed? also i imagine the risk of primary to secondry strike would be higher, as the electrically charged field would be high and concentrated inside the tube of the secondry?
Re: inner Primary proposal
Finn Hammer, Sat Jul 15 2006, 08:54PM
I have made several coils with this type of primary, and although a couple of them still are functional, I don`t recommend it anymore.
The electrical field strength in the area btwn. the primary coil and the secondary is high, and at the primary coil this leads to the formation of corona.
You cannot insulate your way out of a corona problem. If you add more dielectric into the space, the field strength in the remaining air goes up.
So unless you cast the primary into potting compound, and completely avoids voids
, there is inevitably going to be a corona induced failiure.
I have seen this happen, with the acompanying zoot, and carbon tracks all along the inside length of the secondary, to avoid this kind of primary coil.
Cheers, Finn Hammer
Finn Hammer, Sat Jul 15 2006, 08:54PM
I have made several coils with this type of primary, and although a couple of them still are functional, I don`t recommend it anymore.
The electrical field strength in the area btwn. the primary coil and the secondary is high, and at the primary coil this leads to the formation of corona.
You cannot insulate your way out of a corona problem. If you add more dielectric into the space, the field strength in the remaining air goes up.
So unless you cast the primary into potting compound, and completely avoids voids
, there is inevitably going to be a corona induced failiure.I have seen this happen, with the acompanying zoot, and carbon tracks all along the inside length of the secondary, to avoid this kind of primary coil.
Cheers, Finn Hammer
Re: inner Primary proposal
EDY19, Sat Jul 15 2006, 09:28PM
Tuning it would also seem to be a bit of a pain
EDY19, Sat Jul 15 2006, 09:28PM
Tuning it would also seem to be a bit of a pain
Re: inner Primary proposal
Conundrum, Mon Jul 17 2006, 02:28PM
What about making the primary a rectangular coil? use thick HV wire (of the sort used on old monochrome TVs) and wind it vertically.
-A
Conundrum, Mon Jul 17 2006, 02:28PM
What about making the primary a rectangular coil? use thick HV wire (of the sort used on old monochrome TVs) and wind it vertically.
-A
Re: inner Primary proposal
Kolas, Mon Jul 17 2006, 09:28PM
It will definatly be helical (wound like the secondary) Either way, inside or ouside.
However, I didnt get many responses tooting up the idea..... So I guess I wont do it :(
Though, this was an attempt to save wire as far as the primary goes, consideing it's such pricey stuff. Being a 12" diameter secondary.
Any ideas to help cut down on primary length?
Kolas
Kolas, Mon Jul 17 2006, 09:28PM
It will definatly be helical (wound like the secondary) Either way, inside or ouside.
However, I didnt get many responses tooting up the idea..... So I guess I wont do it :(
Though, this was an attempt to save wire as far as the primary goes, consideing it's such pricey stuff. Being a 12" diameter secondary.
Any ideas to help cut down on primary length?
Kolas
Re: inner Primary proposal
EEYORE, Mon Jul 17 2006, 09:38PM
I have used a primary inside the secondary before...I never had any trouble whatsover. it was an 8.5in diameter secondary, and I used 6.5in diameter form for the primary. Primary wire was 14awg insultated hookup wire.
This was with my old DRSSTC(power levels up to 1kw, 3 foot arcs)...
Matt
EEYORE, Mon Jul 17 2006, 09:38PM
I have used a primary inside the secondary before...I never had any trouble whatsover. it was an 8.5in diameter secondary, and I used 6.5in diameter form for the primary. Primary wire was 14awg insultated hookup wire.
This was with my old DRSSTC(power levels up to 1kw, 3 foot arcs)...
Matt
Re: inner Primary proposal
Steve Ward, Mon Jul 17 2006, 09:56PM
You do realize, that if your primary diameter is smaller, you need more turns, right? I think the amount of wire required stays fairly constant. The actual number of turns isnt what is crucial, but the inductance. That said, there are certain geometries that will maximize inductance per foot of wire (i think when H=R its pretty good).
Steve Ward, Mon Jul 17 2006, 09:56PM
Though, this was an attempt to save wire as far as the primary goes, consideing it's such pricey stuff. Being a 12" diameter secondary.
You do realize, that if your primary diameter is smaller, you need more turns, right? I think the amount of wire required stays fairly constant. The actual number of turns isnt what is crucial, but the inductance. That said, there are certain geometries that will maximize inductance per foot of wire (i think when H=R its pretty good).
Re: inner Primary proposal
ragnar, Mon Jul 17 2006, 11:27PM
Or when H = 2r
ragnar, Mon Jul 17 2006, 11:27PM
Or when H = 2r
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