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*To*: tesla-at-pupman-dot-com*Subject*: Re: [Fwd: Spark gap not firing]*From*: "Tesla list" <tesla-at-pupman-dot-com>*Date*: Sat, 10 Feb 2001 15:37:02 -0700*Resent-Date*: Sat, 10 Feb 2001 15:42:11 -0700*Resent-From*: tesla-at-pupman-dot-com*Resent-Message-ID*: <_qVXmC.A.YID.4Och6-at-poodle>*Resent-Sender*: tesla-request-at-pupman-dot-com

Original poster: "Terry Fritz" <twftesla-at-uswest-dot-net> Hi Luc, Oops! As Ed mentioned the correct formula is: Fc = 1/(2 x pi x R x C) The below was in radians per sec... Hi Luc, The source and load impedances play into this but I think the R and C is dominant for the case we have here. Probably close enough... Fc = 1 / RC I always let the computer figure it out ;-)) Cheers, Terry At 11:24 PM 2/9/2001 -0500, you wrote: >Hi Terry, list, > >I'm in the process of designing a power supply and I try to find a formula to >create a RC low pass filter (Terry NST filter protection ) I look at your >paper, >on the web, I remember I read about it in the past but were ? I know if you >change the value of R and C you change at what frequency the filter start to >cut >and how fast the db cut rise with the frequency. I could apply your value but I >like to understand what I do . Can you help me to find the formula or if my >memory is good the graph to calculated it ? > >Luc Benard > > > >> snip >> >> The voltages levels by themselves are within the NST's rated maximum. >> However, what worries me is the frequency. If and NST gets hit with 15kV >> at 60 Hz it is happy. But think of what happens when the output terminals >> are hit with 15kV at 400kHz! The secondary coils of the NST are not going >> to look like nice inductors anymore but rather complex L's and C's. I >> suspect that instead of the high voltage being evenly distributed across >> the output windings, as they are at low frequency, much of the voltage is >> spread across just a few windings at high frequency. At 400kHz, the high >> frequency voltage is just not going to get very far in the output windings >> and that high voltage my hit only a few layers and BLAMMO! Since trying to >> figure out how the high frequency voltage distributes in the output winding >> of an NST is rather messy. I figure it is best to simply stop it from ever >> going there... >> >> Reports like yours of NSTs taking this high frequency voltage are >> encouraging. However, I suspect that is an exceptional case. Since the >> strong emphasis on using protection filters, and putting the gap across the >> NST began, the number of NST failures has dropped dramatically... >> >> Cheers, >> >> Terry >> > >snip >

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