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Re: primary mounting positions
Hi Terry
>
>
> 1. The coupling between the primary and secondary
> may be too high. People
> are always trying to get greater primary to
> secondary coupling. However,
> there is a limit at about 0.2 where increasing the
> coupling further hurts
> performance and starts to cause other problems.
> With the primary in the
> center of the coil, you would have to have the
> primary turns spaced fairly
> far from the secondary just to keep the coupling
> reasonable.
-----
I'm not sure if 1/2 coils are sensitive in the same
manner to the coupling range k>0.2 but I assume the
same spacing primary turns secondary coil turns gives
tighter coupling in the 1/2 case arrangment than in
classical 1/4 wave one.So,I agree primary turns should
be kept far from the mid of coil to avoid overcouplin
problems here.
Back to k>0.2 and classical 1/4 TC.
Someone may say that corresponding theoreticaly
derived waveform for this gives more expressed
freq.splitting and faster voltage rate rise and
secondaries simply don't like being driven faster
(they arc over ,flashover and destroy themselfs).
..And answers I usually meet look like this "for
given final output voltage faster buildup causes more
stress to the secondary."
In other words they refer to time as the most
important factor *dV/dt gradient higher more danger
involved* I can't buy this.And IMHO for TC I would
rather think longer the time of voltage life more
dangerous situation to secondary.
I think that the problem lays in higher local voltage
gradients along secondary structure (dV/dx and NOT
dV/dt) developing during buildup under tighter couplin
conditions.We are dealing mostly with distributed
secondary circuits and how this phenomenon happens
from case to case I can only guess.
Regards,
Boris
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