[Amps] PS Theory ?

Skram, Helge (MED) helge.skram at med.ge.com
Tue Sep 2 16:32:55 EDT 2003

Agree, this works fine. Mains voltage drop may be significant for multi
kilowatt psu's.
I have used the same method to determine the transformer resistance to use
in the PSU Designer.
Load down the transformer and measure voltage versus current. R= delta V /
delta current.

73 de LA6MV

-----Original Message-----
From: Ian White, G3SEK [mailto:G3SEK at ifwtech.co.uk]
Sent: 1. september 2003 16:55
To: amps at contesting.com
Subject: Re: [Amps] PS Theory ?

rlm wrote:
>**  Ian -- Does the PSU Designer program have an entry for Mains 
Well, kind-of. It has a little calculator where you can work out the 
effective secondary resistance, which includes the real secondary 
resistance plus a contribution from the primary resistance plus the 
mains resistance.

If you have a figure for mains resistance, you can add it to the primary 

>How does one measure this quantity?  Thanks.

1. Connect an accurate AC ammeter between the mains supply and your 
biggest amp, or some other large 220-230V appliance.

2. With the load switched off, use a high-resolution RMS AC DVM to 
measure the off-load voltage V1, just upstream of the ammeter.

3. Wind up to full load, and then measure the current I and the on-load 
voltage V2 (which will of course be lower).

4. R = (V1 - V2)/I.

73 from Ian G3SEK         'In Practice' columnist for RadCom (RSGB)
                            Editor, 'The VHF/UHF DX Book'
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