[ARC5] A pair of questions

[WA5CAB at cs.com]

The problem with switchers is that their regulator circuitry allows for 
little to no surge rating.  The standard rule-of-thumb with large dynamotors 
and inverters is that the starting surge current will be at least 3X the rated 
FLA on the nameplate.  Four of the 37A units will probably start a DY-17 or 
17A reliably.  Whether three would work or just go into foldback every time 
is iffy.  What would happen if you tried with just one depends upon what 
the regulator current limiter is programmed to do.  If it just crowbars and 
shuts down, at least you wouldn't hurt the dynamotor or starter relay.  If it 
drops the voltage in order to maintain 37A output, you will probably damage 
the starter relay if you aren't quick enough on the OFF switch when it 
starts oscillating.

Your second idea might work, though.

Robert Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480

In a message dated 11/13/2017 17:03:44 PM Central Standard Time, 
kb8tq at n1k.org writes: 
> Hi
> 
> A pair of Mean Well RSP-1000-27 supplies running in parallel would do the 
> trick if
> you are going the swisher route. You can go bigger if you need to. They 
> let you run
> as many as 4 in parallel at one time. Each one puts out 37A at 27V. They 
> will adjust 
> up to 30V on the output. 
> 
> The switchers have the advantage of efficiency. At 100% efficiency you 
> will have 
> 17.5A at 120V going into your setup.  That will squeeze into a 20A circuit 
> (sort of ….)
> A pure linear supply (as opposed to a pre-switcher / post linear) is not 
> going to be
> very efficient…..
> 
> A 140A 20V transformer and a 200A diode bridge would be another approach. 
> Put
> a few big high current  caps on the output and you have a supply. That 
> sort of idea 
> has been my approach over the years …. Not much regulation, but lots of 
> current. 
> 
> Bob
> 
> 
> >On Nov 13, 2017, at 5:05 PM, Scott Robinson <spr at earthlink.net> wrote:
> >
> >A switcher rated for 75A might be cheaper, but of course it can be a 
> source of RF noise.
> >/scott
> >
> 
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