Re: term understanding: voltage reversal.

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

Original poster: Bert Hickman <bert.hickman-at-aquila-dot-net> 

Tesla list wrote:
>Original poster: "Crow Leader" <tesla-at-lists.symmetric-dot-net>
>----- Original Message -----
>From: "Tesla list" <tesla-at-pupman-dot-com>
>To: <tesla-at-pupman-dot-com>
>Sent: Wednesday, February 18, 2004 7:04 PM
>Subject: Re: term understanding: voltage reversal.
>
>  > Original poster: Bert Hickman <bert.hickman-at-aquila-dot-net>
>[cut]
>  > dielectric and premature failure. The estimated % voltage reversal can be
>  > estimated if you know the "Q" of the circuit:
>  >
>  >     % Vrev = 1.57*Sqrt(1/(Q^2-1))
>I don't understand this formula. Can you add more brackets? It's invalid for
>a Q of 1 if it's (Q*Q) -1 and otherwise it's just 1.57 * sqrt (Q)
>KEN
>
>.
Hi Ken,

Sorry about that - I grabbed the wrong formula off one of the spreadsheet I 
use for some of this stuff. The formula I previously posted was only an 
approximation for systems with relatively large Q's.

The correct formula should be:

           % Vrev = e^(-1.57/Q)

This was actually derived from a formula shown in "The Effect of Reversal 
on Capacitor Life", Capacitor Engineering Bulletin 96-004 on General 
Atomics' (Maxwell's) site:

           Q = -Pi/(2*ln(%Vrev))

See http://www.hvpower-dot-com/technical_bulletins.html  for this and other 
excellent papers by the pulsed power capacitor experts. Unfortunately, the 
formula I originally posted gave similar results for Q=15 so I didn't 
question it at the time. The correct formula holds for any Q > 0.

Best regards,

-- Bert --
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