Re: ballast formula

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

Original poster: "James T by way of Terry Fritz <twftesla-at-uswest-dot-net>" <jamest2000-at-att-dot-net>


Hi Scot,

Tesla list wrote:

>  The EI core should be of a healthy size , the center leg should be
approximately a minimun
> of 9-10 square inches of area.

<snip>

>
> if the transformer you plan to use is too small for the current you plan to
> pump thru your Tcoil transformer, the primary in the ballasting
transformer will meltdown.

<snip>

 I have 4 matching transformers with 8 sq. inches core. The only problem
with then is the interleaved
core.
I have used them as ballast and they work fine but are not adjustable. I
was going to try to make a
ballast with multiple taps as some on the list have done.
There is a great metal scrap yard with cores, I just have to find the right
one. Can't afford to buy
the wrong one.
>From my tests and ancedotal experience of others has shown that it would
be between 150 - 300 turns on
a good size core. I would like to calculate how many turns to allow for
each tap. Also how many turns
to the first tap. Experimenting with #8 THHN stranded is not fun.


>
> if you have an amp meter ( which can handle 100A + )  you can do a quick
> test to see just how
> much the ballasting trannie is rated for ...  connect the primary to your
> supply voltage (
> check secondary voltage to determine the possible amperage delivery (( also
> the size of the
> secondary wire thickness is a hint as to how much amperage is to be
> delivered by the secondary
> the thicker the wire the higher the delivered amperage)) example - 120V in
> 12V out, primary
> wire about a #16, secondary wire about a # 6, expect about 50 amps on the
> secondary side, 5
> amps on the primary side. once you have connected the primary to the supply
> voltage and checked
> the secondary voltage you have your winding ratio available. next step ...
> disconnect primary
> voltage , connect the secondary leads to each other ( short the secondary
> side) and reconnect
> the primary to the supply voltage ...  2 things will happen where ,  either
> the fuse will blow
> or it wont, if it doesnt then check the amperage drawn by the primary. this
> amp reading will be
> the nominal rating of the transformer, and that is about what you will be
> limited to as a
> ballasting current to your Tcoil.

Now that you mention it I never checked my current ballast in that way. I
think I will do that , just
to learn a little.
Thanks for the ideas.
James T


>
>
> Scot D