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Re: New HBT info for Doug

How big an inductor will I need? Also, do you think using a combination of
resistive and inductive load is a good idea? I've seen that advocated in some
places. I'd probably use a low-saturation salt water resistive load (heat
buffer,
and a lot less expensive).
About getting wire from the old xfmrs--they're actually low-voltage
transformers,
and I'm pulling it off the 120-volt primary. The insulation *should* hold.
If I
can, I'll use all new wire, but I might run out.
As for the VA rating, I'm building about 6 kVA in, and about 2-4 kVA out
(hysteresis/eddy/etc. loss).
One other thing-what does HBT stand for? I've seen NST and MOT, but HBT?

Tesla List wrote:

> Original Poster: RWB355-at-aol-dot-com
>
>  Original Poster: Doug Brunner <dabrunner-at-earthlink-dot-net>
>
>  I bought a 100' spool of 10-gauge a little while ago. Problem is, unless I
>  have a LOT of secondary windings to go with it, the inductance will be
really
> low and
>  it'll waste a huge amount of energy in hysteresis losses. I'm going to try
>  to put as many secondary windings on as I can, maybe 6400 or 10000 if I'm
> lucky
>  and can rip open some unused transformers.
>
>  Another question: if I were to put in an external inductive current
>  limiter, would that be a big power loss (as in would I be losing a large
> fraction of the
>  power I put in to the limiter, rather than my coil)? Is a variac a
better way
> to go
>  (if current starts to get too high, turn down the voltage), or is doing
> something like
>  that unsafe?
>
> Hi there again Doug,
>
> You will lose a little power using a limiting inductor. However it will be
> less (a LOT less) than using a resistive limiter. A resistive load not only
> drops the voltage (which an inductive load does not, at least not on such a
> large scale), but also gives off heat. The higher the VA the higher the
losses
> and the more heat is produced. A lot of Teslaphiles use oven elements and
you
> know what that means. They can boil themselves a cup of coffee while running
> their coils. Your variac idea posses one big problem. You know what would
> happen if you ( in case of emergency or excitement) were to turn it in the
> wrong direction. Bye, Bye xformer. If I where you I would use an inductive
> ballast to limit your total current and a variac for fine tuning. This
way you
> can ramp the variac up to full w/o having to continuesly watch the ampere
> meter. Another idea would be to use the variac alone if you can make a good
> and postive dead stop at the max voltage/current you will be able to use on
> your xformer. You would have to find the position experimentally.
>
> W/o knowing what VA rating you want to build I can´t tell you if AWG 10
is too
> big or too small fo the primary.
> I wouldn´t relish your idea of using several different transformers for a
wire
> source, thou.  I´ll tell you why. First of all you would need to find
several
> transformers of the same type to keep the wire gauge the same. Just because
> the tranformers VA is the same, doesn´t mean the wire gauge will be the
same.
> This depends on how much the xformer manufacturer overrated his design. The
> next problem you have is joining the wires, when you run out of the first
> spool. You can solder this, but:
> a.) the wire will be thicker here
> b.) You will have to polish up this joint (sharp edges enhance corona and
arc
> overs)
> c.) You´ve got to insulate this joint really good.
>
> My last argument for not re-using wire is of physical nature. The wire
will be
> kinked at the edges of the turns where it was originally wound. You would
have
> to have a lot of luck if these kinks would "fit" your new core. It´s a
lot of
> work to smooth out these kinks. The wire is more or less strained at these
> kinks, really inviting it to break at a somewhat heavier pull, while winding
> the new job.
>
> If I were you I would:
>
> a.) Decide on my needed VA rating
> b.) Try to find an old welding xformer from stick welder (etc)
> c.) Leave the primary alone.
> d.) Calculate my new number of turns and wire gauge for the HV I need.
> e.) Insulate the new winding very good after each wire layer, core, etc.
> f.)  Go for a small width and a larger heigth for the secondary coil form.
> g.) Try to put the primary in the middle of the core and split the secondary
> in two.
> h.) CT the secondary to cut down the insulation loading.
> i.)  Make a test run w/o oil at 25% and 50%. If all goes well pluck ´er in
> oil.
>
> Never make a HBT for an exact VA rating, when choosing the secondary wire
> size. Go bigger. It won´t hurt and it does give you a comfortable safety
> margin.
>
> Coiler greets from germany,
> Reinhard

--
           --Mr. Postman (Doug Brunner)
                <dabrunner-at-earthlink-dot-net>