[ARC5] High current 28VDC power supply?

[Kenneth G. Gordon]

On 28 Dec 2022 at 17:31, Adam Castellani via ARC5 wrote:
 
> Hope the experienced and bright minds here might add their views on
> the suitability of this unit ,a 600 watt, 25 amp switcher adjustable
> from 21.6 to 27.6 volts for command and liaison set use. 
> 
> 1) Do you think 25 amps will be enough to power both a DM-33 and single DM-32 
> simultaneously as part of a complete SCR-274-N? (actually the transmitter portion is 
> SCR and the receiver portion and modulator are ARA ATA)

No. At least, not by itself. By itself it is 4X too small. However, if you parallel that with two 
fully-charged series-connected automobile-sized 12 V batteries (24 V), the batteries should, 
easily, provide the 100 amp starting current, and the 24 V power supply may carry the load 
after the starting current drops off. That supply may also keep the batteries topped off after 
you have turned your rigs off.

You actually need at least +28.8 VDC out of your power supply to do the job. That 27.6 V 
MAY be just enough.

> 2) How about starting a PE-73 dynamotor to power a BC-375?

Again, no, at least not alone. As above, 4X too small.

> 3) Could the 25 amp unit simultaneously power a BC-375 and BC-348 as part of a 
> complete SCR-287?

Again, no.
 
> 4) Would it have a hope of powering both an SCR-287 and an SCR-274-N at the same 
> time?

Hardly.

> In addition to the PP-1104-C units, which I wish were available in the UK, are there other 
> ready built PSUs worth considering?

I don't know. Others may. You also may wish to consider building your own switching supply. 
Although that would be time-consuming, the circuitry is not particularly involved, and 
schematics are available on the web. I cannot give you direct links to such projects, but I 
have seen them.

> The 25 amp models are available. Unfortunately, the next size up which is 1000 watts, 
> 42 amps adjustable from 20.4 to 28.8 volts is on back order for a year.

Well, IMHO, although that one may be barely adequate, there are other power-supplies 
which could do the job. You may wish to look for an old military surplus "28 VDC" power 
supply. You MAY find one on eBay. Shipping would be pretty high though. They are pretty 
heavy.

> Thank you for your views and help. Photographs of these two projects are here,here 
> ,hereand here.
> 
> Merry Christmas and Happy New Year,
> Adam

And Merry Christmas and Happy New Year to you and yours.

Ken W7EKB