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Re: [Amps] watts unlimited smps

Subject: Re: [Amps] watts unlimited smps
From: Ian White GM3SEK <>
Reply-to: Ian White GM3SEK <>
Date: Mon, 27 Jun 2005 00:12:15 +0100
List-post: <>
Johan wrote:
>here is some info on the watts unlimited PS.
>Being part of the J3/K5AND group running this smps in a 8877 amp we have
>run into some serious issues with this PS.
>The local power system on Grenada does not allow us to use this PS.
>The power system used here is a phase and neutral, where the neutral
>is grounded.This creates a ground loop after the bridge rectifier this
>tripping the resorts fuses.
>I had a long look at the schematic and bottom line is that this power
>supply will never work in these specific power line configuration.
>We had a look at the manualand its not specified that under these
>conditions the ps will not work.
>You can ONLY work if you have a floating AC line. Now these power
>systems are used throughout the world, so you'd better check before using
>it on a expedition.
>The only suggestion I can make is to have a isolation transformer in
>front of it,but whats the point of using a light weight PS?

I have the schematic here, and the grounding is not totally clear - 
there seem to be three different "ground" symbols used in various 
places. In different countries, those symbols could be interpreted as 
"mains earth", "chassis"... or possibly the other way around.

But the Watts Unlimited PSU works fine on US 115V and also on British 
230V, both of which have neutral connected to ground. In both of those 
countries, neutral and protective ground are separated on the supply 
side of the overload breakers and the residual current breaker.

What exactly did you mean by "tripped fuses", and exactly how is the 
supply side wired in Grenada?

73 from Ian GM3SEK         'In Practice' columnist for RadCom (RSGB)
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