Date: Thu, 06 Jun 2013 05:08:14 -0700
From: Bill Turner <dezrat1242@yahoo.com>
To: Amps <amps@contesting.com>
Subject: Re: [Amps] Advice needed for SS amp
ORIGINAL MESSAGE: (may be snipped)
On Thu, 06 Jun 2013 04:24:21 -0500, W4DNR wrote:
>
>If there were no long term effects of dropping the whole circuit down
>into a tank of water or 50/50 glycol, I think there would be
>additional cooling benefits for the whole pc board.
REPLY:
Brian, ZL4AD, just sent a picture of an amp cooled by transformer oil, which
is a non conductor of course. Might simplify things, worth looking into.
73, Bill W6WRT
## I would not mess with a 50/50 glycol water mix. Sure the boiling point is
raised
to 265 F..and the freezing point is at –40 F. But unless you plan on having
the amp
in an UN heated garage, don’t bother with a 50-50 mix. 100% Distilled water
will
remove way more heat than a 50-50 mix. To prevent spot boiling and bubbles
forming,
and for better flow, you could use a few oz’s of redline water wetter, or
Royal purple..
purple ice. These products just reduce surface tension,and are used in car
engs all the time.
## Most race tracks wont allow a 50-50 mix to be used. They instead use a
100%
distilled water + water wetter. Adding the water wetter agent to the distilled
water will
reduce the temps by a huge amount, like 20F. Dunno if water wetter will
increase resistivity
of water or not.
## a buddy recently constructed a 50 ohm dummy load, built from 9 x 50 ohms
surface mount
resistors, each resistor rated at 800 watts CCS. Wired series-parallel onto a
large AL heatsink.
One of the resistors exploded. The fix was to immerse the fins of the
heatsink straight down into
a ice water bath...problem solved.
## I would not suggest using De-Ionized water either. The ion depleted water
will attack everything
in site. Water cooling could be achieved by using a small 4 to 20 GPM pump,
and routing to an
external air cooled radiator. I use a 4 GPM Bosch 12 vdc electric pump for
my cars supercharger’s
heat exchanger- intercooler setup. It only draws 4 A @ 14 vdc. You can
also get em in 8 GPM,
and all the way up to 55 GPM. A 120 vac version would be the ticket.
## I think 1 watt = 3.15 BTU So for a 1500w output RTTY setup, with say
50% eff, the SS amp
would have a 3 kw input..and 1.5 kw output...and have to dissipate 1500 w as
heat. 1500 x 3.15 =
4725 BTU’s. I just bought a small 7.5 inch tall x 12 inch wide x 3/4 inch
thick transmission cooler for
my car. It is rated for 13,000 BTU. It is a bar + plate type vs the less eff
tube + fin type.
## as long as you had a high enough flow rate, like 2-8 GPM, and a pair of
fans on the small external
radiator, water cooling should be doable. You can mount the radiator either
vert like in a car..OR
horizontal, with air being blown up from below. Commercial air conditioning
roof top units are now
using H mounted rads with fans below em. For ham use, the rad + pump could be
located in another
room, or mount the rad outside.
## As for 50 vdc supplies, there are literally thousands of surplus Telco 52
vdc supplies across
the usa and canada these days..they can’t give em away. They come in
25-50-100-200-400-800A
variety, all using xfmrs. Typ 208/360/480 vac 3 phase for the bigger
ones..and single phase 208/ 240 vac
for the smaller ones.
## telco’s + cell sites are all now using 52 vdc switching types. 3.3 kw
CCS each. Up to 6 can be
mounted in a 25 inch wide rack x 7 inch tall... 19.8 kw ccs. At the office I
worked in, we stacked em 6-7 high,
used for the UPS setup. They barely run luke warm. They either run on 208
single phase...or
240 vac single phase. They will operate just fine with anything from 160 vac
to 300 vac.
Any line freq from 40-70 hz. The slick part is the power factor is always
unity. If 2 or more are used,
they will talk to each other, such that the load always divides equally
between em. If one craps out,
the remaining units take up the slack. $475.00 each brand new. Dunno how
many you could string in series.
I have never tried wiring em in series. You can get em surplus too.
.
I like the idea of a 170 or 340 vdc supply. Then no xfmr required, just a FWB
+ filter cap.
Jim VE7RF
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