[ARC5] 24vdc power

[scottjohnson1 at cox.net]

I wish I saved my old posts on this subject since it comes up every so
often!  I find the best way to operate rotating machinery that once operated
in a mobile environment is to replicate that environment.  SO-
Get a power supply that can handle the full load current and float an SLA
battery across it.  Size of the battery and power supply is proportional to
load, but in your case, a 10-20 A switcher. Set to27.5 V (for normal indoor
ambient temperature)
Less for hotter, more for cooler, but in the range of 27-28V.  For your 10A
load, 12V 7AH SLA batteries would do nicely. (Two in series).  Increase AH
capacity proportionately for higher current loads.  Amazon and eBay have
plenty of inexpensive switcher that will work, just don't buy the REALLY
cheap ones, unless you like the acrid smell of burning components.

-----Original Message-----
From: arc5-bounces at mailman.qth.net <arc5-bounces at mailman.qth.net> On Behalf
Of Charles via ARC5
Sent: Sunday, September 4, 2022 10:23 AM
To: arc5 at mailman.qth.net
Subject: Re: [ARC5] 24vdc power

> Hey guys,
> What's everybody using to provide 24vdc for your military radios? Two
12vdc supplies in series?  Home brew?  Do they make a 24vdc switching supply
that will handle 10 amps or so?
> Thanks for your input,
>
> Richard kn7sfz
Anything with a dynamotor needs about five times the motor nameplate current
for the starting surge...

I got a 2 KVA three-phase 115V 400 Hz rotary converter at a flea market but
nothing I had was big enough to start it (rated at 27.5VDC at 115 amps!)

So I bought a 20 VAC, 5 KVA toroid transformer on ebay, a BFBR (big bridge
rectifier), heat sink, a 220,000 uF cap, meters and shunts, and brewed up a
24-28V 120 amp brute force supply with 240 VAC input. THAT starts the
converter all right. It doesn't even blink at smaller dynamotors :)

-Charles, WB3JOK/0

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