RE: homebrew hv

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Loudner, Godfrey by way of Terry Fritz <twftesla-at-qwest-dot-net>" <gloudner-at-SINTE.EDU>

Hi Marc

Locating the primary on the center leg and the secondary on the two outer
legs will gives you some degree of current limiting. This will also reduce
the insulation requirements. If you put both the primary and secondary on
the middle leg, the insulation requirements will be very high. In fact you
might have to back off your goal of 40 kV. Unless you can get hold of
professional insulating materials, it is unlikely that substitutes will
stand up to 40 kV. I tried to get hold of professional materials, but you
have to buy in bulk. The professional materials are very thin, absorb oil,
and have tremendous dielectric strength. My dental x-ray transformers are
about the same size as the ones I see at your web site, but they are capable
of 70 kV and 10 mA. An inspection of the x-ray units reveal the high quality
of the insulation. Also have you checked that you have enough window space
to pack in that many turns of # 22 wire along with insulating materials. If
you insist on 40 kV, I would place the primary on the center leg. The
secondary should be placed on the outer legs. The winding on each leg should
be broken up into two or more coils that are well insulated from each other.
Remember that these coil sections have to be properly phased with each
other. These procedures will reduce the insulation requirements. Whether you
decide to ground to the core or not as in NSFs, you will have serious coil
to core insulation problems at 40 kV.

As to your second question, you certainly have an inductor that you can gap
with shims. Its current limiting capabilities will depend upon your
measurements. A situation like this can be sized up by experiments. 

Godfrey Loudner  

> -----Original Message-----
> From:	Tesla list [SMTP:tesla-at-pupman-dot-com]
> Sent:	Saturday, September 29, 2001 1:28 PM
> To:	tesla-at-pupman-dot-com
> Subject:	homebrew hv
> 
> Original poster: "Metlicka Marc by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <mystuffs-at-orwell-dot-net>
> 
> All,
> Last night i pulled one of the 40-1 transformers apart:
> http://www.fortunecity-dot-com/meltingpot/syria/1210/id26.htm
> They are held together with steel strapping and the cores slid out very
> nicely. The cores are really well constructed, looks like they may have
> been pressed into shape? They are actually 1"t x 2.5"w x 12"h with a
> 4.5" outside core width.
> There are a few things i want to ask for help on:
> first is whether this seems like a good core to wind a hv transformer
> on?
> i am thinking of a large nst type transformer using a hv winding on each
> outer leg and the primary on the center. The thing is that the original
> transformer has both windings around the center lag, maybe because all
> the flux travels through this doubled section? so will the windings on
> the outer legs see enough magnetic flux to generate the hv, I'm shooting
> for 20 kv each using and 41675 turns of 22g wire each. This would need
> 250 turns of primary wire (if my calcs are right?) or would it be a
> better idea to wind one single hv winding with the primary in the center
> like the original? I'm just not experienced enough to know.
> 
> second is that with the large taps of the originals secondary windings,
> and the fact that two cores doubled up fit right into the hole of the
> big winding, and the fact that i could gap the core with shims, could
> this make a good high current inductor?
> I will check the inductance of this core, but i was wondering if anyone
> could give me an idea of what it should be for a nice 100+ amp current
> limiting reactor?
> The center core area would be 12" but capable, the taps are 250 amp
> rated so it looks like at least a 150 amp rating for the windings?
> I will post more data as it comes, but i'm hopping for some input from
> the list on these tesla projects? (i hope, i hope)
> Thanks,
> Marc
> 
>