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[Amps] Transformer secondary resistance

To: <amps@contesting.com>
Subject: [Amps] Transformer secondary resistance
From: Ian White, G3SEK" <g3sek@ifwtech.co.uk (Ian White, G3SEK)
Date: Tue, 7 May 2002 07:43:48 +0100
Jeffrey Madore wrote:
>Thank you, gentlemen, for your responses re my questions pertaining to 
>the suitability of a transformer with a 106 Ohm secondary at 5300 volts 
>and a 120 volt primary. BTW I rechecked the primary resistance and it 
>appears to be about 0.1 Ohms + - .
>
>My next question is, what would be considered a decent secondary 
>resistance at that voltage?
>
>Actually that voltage is a bit high. What if I used a full wave ct 
>rectifier scheme? Then the voltage would be about half and the 
>secondary resistance would also be 1/2. Would a 53 ohm secondary be 
>considered suitable for a 1500 watt amp?
>
>Since I have access to all the winding leads, what if I paralleled the 
>secondary windings and used a bridge rectifier?  Now the secondary 
>resistance would be about 26 Ohms.
>
All these questions can be answered by Duncan Munro's excellent PSU 
Designer software. There's a link from the 'In Practice' page on my web 
site, where you can also pick up a file containing rectifier data for HV 
supplies.

Unfortunately the transformer data input doesn't consider primary and 
secondary resistance separately - only secondary resistance - but 
there's a workaround in the Help file: multiply the primary resistance 
by the step-up turns ratio squared, and add it to the secondary 
resistance.

>
>Any opinions are much appreciated.
>
With the best will and knowledge in the world, it's hard for anyone in 
this group to give opinions on a transformer he's never seen. Used 
properly, this software lets you make your own predictions.

-- 
73 from Ian G3SEK          Editor, 'The VHF/UHF DX Book'
                           'In Practice' columnist for RadCom (RSGB)
New e-mail: g3sek@ifwtech.co.uk
New website: http://www.ifwtech.co.uk/g3sek

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