[ARC5] A pair of questions

[jeepp]

Just to sdd to the fray, I use a .5 ohm, 300 watt soft-start resistor on my PP-4763A.  I also modified the relay ckt on the PE-73C.  Haven't addressed the single DY-17A, yet.  Wish I could find one of the huge supplies.....  I also just bought some 15A  switchers that, with input and output EMI filters. They do Ok noise wise for the 24v for the ART-13 a.c. supply and associated receivers, on 80 and 40.  Jeep K3HVG


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-------- Original message --------
From: WA5CAB--- via ARC5 <arc5 at mailman.qth.net> 
Date: 11/14/17  01:04  (GMT-05:00) 
To: arc5 at mailman.qth.net 
Subject: Re: [ARC5] A pair of questions 

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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