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Re: NST Protection

Hi Arthur,

        It seems like burning off very roughly 10% of a coil's input power in
the NST filter resistors gives good results.  In your case, that is 15000 x
0.030 x 0.10 = 45 watts.  So each of your resistors could be 25 watts at 25 /
0.030^2 = 27.8K ohms.  "I" would go for 10K ohms each just because... (it's a
little armwaving).  So one 25 watt 10K on each leg should do it...  That is
only 9 watts per resistor but you need big resistors to hold off the voltage
(maybe you should go to 50 watts with a 15kV NST to bee sure to hold off the
voltage).  10K and 500pF gives a cutoff frequency of 31.8kHz so you should be
cutting the high frequencies well.  

So a 10K-ohm  50-watt resistor and a 500pF 10kV cap on each leg to ground is my
best guess...

Cheers,

        Terry

At 12:18 PM 05/16/2000 +1000, you wrote: 
>
> Hi all, 
> I'm in the process of building my NST protection for a 15kv/30ma setup. 
> I have 2 safety gaps + 2 500pf 30kv caps to ground. I am wondering as to what
> rating to go for in the way of resistors. I have seen a few different setups
> on some of your web sites but most are for larger NST's. Should I go for
> 1.5k/100watt, one on each HV side? 
> 1k/50watt,two on each side? 
> 5k/50watt,two on each side? 
> And could someone please explain what is the correct way to work out the
> right resistors for a particular power supply. 
> thanks in advance, 
> Arthur.