[Amps] Glitch resistor + fuse?

Jim Thomson jim.thom at telus.net
Wed Nov 15 14:15:20 EST 2017

Date: Wed, 15 Nov 2017 09:49:54 -0600
From: "Doug Renwick" <ve5ra at sasktel.net>
To: <amps at contesting.com>
Subject: [Amps]  Glitch resistor + fuse?

<The Tentec Titan amp uses a single 10 ohm 25watt ohmite.


##  with say 1.5 A of plate current, that amounts to 22.5 watts diss, so it will work ok. 
But 10 ohms doesnt limit the fault current to a low value.  2600 divided by 10 = 260 A fault current,
which is still a bunch.   2600  divided by 50 ohms = 52 A fault current..which is a lot less obviously.
Anything is better than nothing of course.  

##  Forgot to mention in my previous posts, re protection diodes.  I use several 6A10 s in parallel, to 
make one big diode.   3 or 4 of the 6A10s, each with a 400A  surge rating, albeit only for 8.3 msecs, 
is then good for  1200-1600A.   With out any HV fuse in there to interurpt  the fault current, it can take
a while for the breaker in the 240 vac line  to open up.   The HV filter C,   plus the value of the glitch Resistor,
form a simple  RC network. 

##  eg.  25uf  and  10 ohms  =  .00025 secs.   = .25 msec
25 uf and 50 ohms =  .00125 secs     = 1.25 msecs
100 uf  and  50 ohms =  .005 secs     =  5 msecs

## and thats just the time it takes to partially discharge the filter cap down to just 36.8 % of the original B+ voltage.

Jim  VE7RF

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