Re: Microsim and filter design

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

Original poster: "Dr. Duncan Cadd by way of Terry Fritz <twftesla-at-uswest-dot-net>" <dunckx-at-freeuk-dot-com>

Hi David, Terry, All!

Date: 22 January 2001 01:36
Subject: RE: Microsim and filter design


>Original poster: "Terry Fritz" <twftesla-at-uswest-dot-net>
>
>Hi David,
>
> You want the filter to reduce the high frequency ringing
that reaches the
>transformer.


<snip>


>>I then
>>substituted the filter you suggested and repeated the
simulations both with
>>and without the damping resistor. Results can be found at
>>www.corridor-dot-net/deano/NewFiltr.zip . (336KB)


<snip>

Thanks for your input on this.  I have "had a go" myself,
though being a complete neophyte on the microsim thing, have
no great confidence yet in my ability to drive it. The
learning curve is vaguely Himalayan and my simulations are
presently perched precariously half way up the South Col ;-)

The following comments should therefore be treated
_with_*great*_caution_ !


My initial observations are:

1) The "little L", L,C components need selecting on the
basis of the radio frequency being generated by the coil.
For 100kc/s, "little L" = 50mH, L = 400mH, C = 10nF+ looks
interesting. Obviously the inductance and capacitance needed
for higher frequencies is less. The previous values I
suggested are better for e.g. 400kc/s.

2) There may be quite a high current circulating in the
damping resistor, which needs selecting on the basis of the
"little L" and C values.  I remain uncertain about the
appropriate power rating for this component.

3) Care needs to be taken to ensure there is not a
possibility of resonance between {"little L" + L} and C with
the break rate 8<O


In other words, the filter needs designing for each
individual coil (though it isn't exactly hard!)  However,
from my limited twiddling, it does seem that it _may_
(emphasise uncertainty!) be possible to design a good filter
with 1-2% input power loss.

I _may_ (emphasise high probability) be quite wrong here
(CAUTION: learner driver!) and it would be great if more
simulations on this thing can be done to test these findings
prior to cooking a transformer with this filter design!  I
wouldn't want anyone to lose a tranny (or worse) thanks to
my inexperience with microsim.  All input/comments
gratefully received.

Dunckx