[Amps] PS Theory ?

[Ian White, G3SEK]

Steve Thompson wrote:
>On Thursday 28 August 2003 06:39, Skram, Helge (MED) wrote:
>> The peak current will depend on capacitors and resistances.
>> Peak current can be very high. What is important ia average current.
>Peak current determines the voltage under load, it's RMS current rather than
>mean or 'average' that determines the heating effect in the transformer. If I
>remember correctly, transformer RMS current is typically 2-3 x dc current in
>a bridge/capacitor input psu. The psu designer prog. gives you good
>information about what's going on and has accurately diagnosed shortcomings
>in several psus I've looked at.

Yes, it gives accurate values of RMS currents in the transformer, diodes 
and capacitor separately - all items of interest.

There's a "gotcha" here. 'PSU Designer' always starts its simulation 
with the switch-on surge at time=0, and this will distort any average 
results including RMS currents. So be sure to check how long it takes 
for the graphs to settle to steady values, and then specify "Report 
After A Delay Of" at least that long. You will then see the correct 
steady-state results.


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