[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.
<Doug
## 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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