Date: Tue, 25 Apr 2017 22:45:14 +0000
From: Bill Turner <dezrat@outlook.com>
To: Amps group <amps@contesting.com>
Subject: Re: [Amps] Price per Watt Conversation
On Tue, 25 Apr 2017 20:37:07 +0000, Manfred wrote:
>
>And why on earth should I use two power supplies in series, instead of
>using a single one of the proper voltage?
REPLY:
Cost.
50 VDC 3 kW supplies are available on eBay dirt cheap. Obsolete
telephone equipment.
73, Bill W6WRT
## agreed. At the telco I worked for, the older –52 vdc switchers
were 3 kw CCS rated, and would work from 40-70 hz. Some
were designed for 208 vac single phase input, usually a 30A breaker
used for each supply. Up to 6 x supplies in a single shelf. They would
all talk to each other, so if one craps out, the remaining 5 would divide
the current between them..and dead on equally. Never saw one blow
up..or give us any problems.
# The newer versions are now 3.3 kw CCS rated, work from 40-68 hz, and
have near perfect power factor correction, as in > .99 at any phase angle.
Neither the old or the new style barely gets luke warm, with a 60A CCS load.
## Just before I retired in nov 2009, several hundred were installed around
town.
We also used them in cell sites. Those ones ran on 240 vac 60 hz, just like
what
you have at home. Looking at the specs, they would run on anything from
165 vac..up to 310 vac.
## Unique in that they could be pulled..hot. They used long silver plated blades
for the -52 vdc output connection to the main buss bar. And shorter, smaller
blades
for the 208 / 240 vac input. When pulled hot, the shorter blades disengage
1st, so the
208 /240 is disconnected a split second b4 the –52 vdc gets disconnected.
## They can be wired for + 52 vdc as well. telcos all use -52 vdc...since
they adopted
the positive ground scheme eon ago. Done to minimize positive plate growth in
the
lead acid batteries. I see no reason why 2 or more cant be wired in series.
## For main office telco use, 6 were in a shelf, aprx 25-30 inches wide. bay
was at least
6 ft tall, and so several shelves could easily fit into a bay, then multiple
bays side by side.
## they are small things, like aprx 4-5 inches wide by aprx 6-7 inches tall
and aprx 12 inches
deep. Well built and designed for 24-7-365 use. Will handle high ambient room
temps and also
high humidity. 3.3 kw x 6 = 19.8 kw CCS per shelf. In normal operation,
the load is such
that if one supply crapped out, the remaining 5 would easily handle the load.
IE: shelf
good for 6 x 60A = 360 A. Normal load would be like no more than 250-280A
per shelf.
## last I looked, they were $475.00 new in the box, with a superb warranty..
built in the usa.
You cant build a 3.3 kw CCS HV regulated supply for that $... nor even an
un-regulated supply.
And the power factor will suck on any B+ supply, there is no way to do PFC on
the typ C input
B+ supply.
Jim VE7RF
## So the power supply to run any of these SS amps is really a moot point
these days, non issue.
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