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Re: [Amps] transformer talk

To: amps@contesting.com
Subject: Re: [Amps] transformer talk
From: Steve Thompson <g8gsq@eltac.co.uk>
Date: Fri, 10 Feb 2006 07:35:25 +0000
List-post: <mailto:amps@contesting.com>

KD7QAE wrote:
> For the major types of filters the secondary RMS current is related to 
> the DC load current as:
> 
> Inductor input: 0.7
> FWCT capacitor input: 1.0 to 1.2
> FWB capacitor input: 1.6 to 1.8
> 
> Data from O.H. Schrade: "Analysis of Rectifier Operation"
I agree these are the ranges of figures that 'drop out' most often - but 
I'd caution against automatically assuming that they cover every 
instance. In the last case, if you have 1.9 instead of an assumed 1.7, 
there's 25% more heat.

In the absence of using PSU Designer or somesuch to predict values, 
0.7xIdc for choke input and 1.7xIdc for capacitor input are also useful 
estimates of the rms ripple current in the smoothing caps.

Steve
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