RE: NST power rating con

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

Original poster: "John H. Couture" <couturejh-at-mgte-dot-com> 


For the watts rating of a NST refer to my post Oct 2,2003. The watts output
of a NST is a humped curve on a graph of resistance vs watts. The maximum
wattage is always much less than any nameplate rating. The 7500 KV, 30 ma,
225 watts(?) NST that I tested had a maximum output of 59.3 watts. This
gives a ratio of

    max watts/nameplate watts = 59.3/225 = .2636 = 26.36%

However, the max test watts output to test watts input was

    watts output/watts input = 59.3/60 = .988 = 98.8%

This is the main reason that using NST nameplate numbers for rating TC's
doesn't make sense.

John Couture

-------------------------------


-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Thursday, October 02, 2003 1:29 PM
To: tesla-at-pupman-dot-com
Subject: Re: NST power rating con


Original poster: Ed Phillips <evp-at-pacbell-dot-net>

Tesla list wrote:
  >
  > Original poster: Thomas <tom-at-pwrcom-dot-com.au>
  >
  > The more I look into this the more proof I get that the actual power
  > available from an NST is only half of the face plate values' product,
i.e.
  >
  > P =(V x I)/2
  >
  > It's the only way I could get this to work out:
  >
  > http://www.users.bigpond-dot-net.au/broken.trout/Rotary_eqns.pdf
  >
  > Also it gives an extremely close value (+10%err) for spark length when
half
  > the secondary VA is used for P in: L = 1.7sqrt(P) for my coil.
  >
  > I think the +10% length measured is due to the primary cap being resonant
  > with the NST, and a slightly too wide spark gap.
  >
  > Why is this con(fidence trick) by NST manufacturers not mentioned on any
  > Tesla coil design web sites (that I've seen)?
  >
  > It's almost as bad as the *peak music power* con used by cheap audio gear
  > manufacturers.
  >
  > Tom L.


	Not exactly correct.  With a pure resistive load the power output limit
is as you say.  With a resistive/capacitive load as in TC applications
the power can be very much higher than the product of name plate
open-circuit voltage and short-circuit current.  I've never seen an NST
rated in watts.  Has anyone else?

Ed