Solid State Magnifiers.


I've had a bit of time to do a bit of electronics over these last few
I've got a half bridge working - only 4" sparks at the moment because I'm
more concerned with design, theory and measurement before I push it
up to a kilowatt.

A some questions, regarding saturating the output transformer.

1) In the push pull configuration (centre tapped primary, voltage applied
alternately to each half) the output voltage is 2 * Vin * the turns ratio.
Each primary is pulled down to 0v and then see saws to twice the supply
voltage (Vin) when the other side is pulled down. (the centre tap goes to
the positive supply).
When I come to calculate the number of primary turns required to keep
the maximum flux density under say 2000 guass should I calculate on the
basis of Vin or 2 * Vin?  
(I have used Vin but I now think that my output transformer is saturating,
as a result).

2) Same question but for a half bridge I take it I use Vin and for a full
bridge or
H bridge I take it I use 2 * Vin?

3) Can the transformer also be saturated if too much current is drawn from
the secondary? I suspect yes but then how much is too much?

Now an easy question :)

I can measure the input impedance of the coil at resonance - I know the
voltage and current drawn and the turns ratio - it seems to be about 5k
(The coil is a polythene bucket 13 inch diameter wound with 0.4mm wire for
hieght of 14", toriod about 18" diameter of  3" diameter tube), resonating
at 89kHz.

4) How would I calculate the theoretical input impedence for a given coil -
treat it as a
series L, C, R circuit when viewed from the bottom where L is the
inducatance, C is
Cself plus Ctoriod, R is the DC resistance of the wire (maybe fudged with
the skin
depth to give a better approximation to the AC resistance)?

I'm thinking of winding a coil with a lower input impedence - which I can
drive with
a lower secondary voltage on the output transformer (reducing the number of

turns, insulation problems and the effects of internal capacitance).

Just in case that isn't enough for you there is bonus question - I would
like to
get a really big ferrite output transformer -I've just got an ETD59 Philips
Farnell which has twice the core area of the ETD49 that I'm experimenting
When I went for the data on it I noticed that Philips also do an E71 - does
know where I can source one?  (UK preferably but it's fairly light - so
shipping is OK)

My previous solid state stuff is one my web page:


Have fun,

Alan Sharp.