Re: Modeling the transformer

["Herbert Mehlhose" <herbert.mehlhose-at-xxxxxx> (by way of Terry Fritz <twftesla-at-xxxxxxxxxx>)]

Hi,
thank you Terry for your explanation to my question some time ago.
I have now done my model as you told me.
My measurements with open load and calculations lead to 68mH primary
and 323H secondary inductivity. At 229V my transformer draws a current
of 10.7A with open circuit.
My transformer has a rating of 220V/15.4kV at 130mA. It has a 5mm
gap in the core.
I ran the model with closed output and adjusted coupling until the
secondary current matched.
With open load, it was not enough to change the secondary inductance
just a bit, instead I had to change it to a much higher value. This again had
an influence on the short current again..... So I ended up with several
iterations until everything seemed to be fine.
The model now looks like: L primary=0.0681H, L secondary=700H.
R primary=0.25ohm, R secondary=1352ohm.
Coupling is quite low: only 0.68 (due to the gap in the core...)
What strikes me is the quite high difference in the secondary inductivity
values: 323H vs. 700H.
I now did a measurement, feeding voltage in the secondary and
measuring the current with open primary. This leads to a
value of 274H, much closer to 323H.
I'm not sure about my 700H value now. This is especially important for me,
as with 700H I will have about 40Hz resonance with my cap resulting
in resonant charging effects. With 323H this would be 59Hz, so if I am
somewhere in between, my resonance will be VERY close to
50Hz. So I will need a very good safety gap over my 100bps SRSG
I'm currently building. I'm trying to add a model of the safety gap into
my microsim schematic, but up to now only with strange results.
Any ideas where this large difference comes from? Maybe the gap
in the core makes this model inaccurate??
Under
http://home.wtal.de/herbs_teslapage/model2.html
there is some information about the new coil I build, also a small
picture of the transformer.

Thank you very much for any help.
Herbert