Re: resonant vs LTR

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

Original poster: FutureT-at-aol-dot-com 

In a message dated 1/5/04 7:41:33 PM Eastern Standard Time, 
tesla-at-pupman-dot-com writes:

>hi all,
>
>in the teslamap program the resonant tank cap for my
>transformer (15\30-240v\50hz) is shown as 6.8nf and
>the LTR cap is shown as 8.9nf. is it acceptable to use
>a cap value somewhere in between\including these two
>values or is it either\or with no in between?
>
>regards
>richard


Richard,

I assume you're using an NST or similar transformer to power the
coil.  One thing to consider is that if the cap value is too small
(too close to resonance), a terrible condition called the *voltage
reversal mode* may occur.  Actually this may occur only using
a synchronous gap at 120 bps.  So if you're using a static gap,
you don't need to worry about this (I don't think).  With a static
gap, you can
always keep the gap spacing close, and thereby avoid extra
high voltages which would perhaps destroy the NST.  Another
thing to consider is that an NST may resonate over a range:
It may resonate with caps considerably larger in value than
the formula predicts.  Each NST brand and size may behave a
little differently.  When the voltage reversal mode occurs, it
will make the power factor horrible, the NST will draw a
very high current and run very hot, and be destroyed over time.
Async (non-sync) rotaries may destroy NSTs especially if run
at a low breakrate.

John