RE: Filters & Chokes

[Terry Fritz <twftesla-at-xxxxxxxxxx>]

Hi Gary,

	Wow!  What a great tidbit of information!  I always was puzzled by your
coil's great performance and how "very" hot your resistors were getting.
Looks like you have the first SLTR (Saturating Larger Than Resonant) coil!
If you can run a 15/60 at 184mA RMS I won't feel so afraid of running mine
at 85mA ;-)))  You may want to consider putting a line fuse on the input of
the NST to prevent the thing from really going nuclear.  I would think:

15000 x 0.184 / 120 = 23 amps!!

I guess a 20 amp fast blow fuse would be right!?  I am very surprised it
can take that.  I wonder if there is some mechanism that is preventing the
NST from going to super high currents.  If one can reliably run and NST at
these high currents (2760 watts!!), it would be a major step forward!!  "I"
have always been afraid to "play around" up there and I don't scare easy! ;-)))

Cheers,

	Terry


At 09:03 PM 11/14/2000 -0500, you wrote:
>I use a standard unmodified 15/60 NST and the filter uses a pair of 1.6K
>113W resistors.  For a very long time I was puzzled at just how hot these
>got.  By standard logic, the power is I^2 R, or .06^2 * 1600 = 5.76Watts.
>But after building a fiber-optic VI probe, I was able to scope the NST
>secondary current with a digital scope, which also performs true-RMS
>calculations.  Guess what?  My 60mA NST is pushing 184 mA, RMS.  It appears
>that some unexpected things happen when charging an LTR cap, speculation is
>that the current shunts saturate and allow far more current to pass.  So the
>184 mA causes a dissipation of 54 Watts per resistor.
>
>Gary Lau
>Waltham, MA USA
>