And now with the new 65 vdc LDMOS
devices, all those 50 vdc units are
obsolete.
Progress ...
73, Dick, W1KSZ
On Wed, Apr 26, 2017 at 8:30 AM, Jim Thomson <jim.thom@telus.net> wrote:
> 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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