Re: cap firing voltage scope measurements question
Subject: Re: cap firing voltage scope measurements question
From: Terry Fritz <twftesla-at-uswest-dot-net>
Date: Mon, 21 Jun 1999 20:13:01 -0600
At 05:04 PM 6/21/99 -0400, you wrote:
>In a message dated 99-06-21 16:16:18 EDT, you write:
>Not only is it more robust to use a stiff transformer and separate
>ballast as I'm doing, but it allows a complete tuning of the charging
>system, such that the peak cap voltage can be made to coincide
>with the best firing phase. An NST system may require a
>compromise in the firing time.
I tried to model an NST system with a large inductive ballast (50mH). I
could adjust the firing time as you say and it gives a great charging
curve. However, the firing voltage drops from 21kV to 8kV :-( Looks like
a PT or "stiff" transformer is required for this most interesting timing
adjustment with an external ballast.
Of course, a stiff transformer can charge a larger cap than an NST anyway.
So there may be other things affecting it. Could it be that you PT system
is simply supplying higher currents and you are simply charging the cap at
a nice looking point when, given a fixed ballast, you could get more energy
out if you were to still fire late and charge an optimally sized primary
cap?? By working with a fixed ballasted transformer, I get the best power
transfer by firing late. I would think that would hold basically true for
any current limited transformer. I wonder if given your ballast setting,
you have a nice charging curve but the system is less optimal than it could be?