[Amps] measuring secondary resistance TSPA

Steve Thompson g8gsq at eltac.co.uk
Mon Mar 27 03:33:31 EST 2006


John T. M. Lyles wrote:

 > Steve
 > What do you look for, in terms of relative resistance, for a 
choke-input-filter designed transformer?

Sorry for the very late reply. Other distractions, and searching for a 
notes of measurements, which I've failed to locate.

Turning to ones kicking around in reach here:

1800Vac 1.5kVA which I had custom wound. Secondary resistance is 19ohms. 
With 40uF cap input, this transformer is happy at 750mA dc for hours, 
and comfortably delivers well over 1A dc.

1900V, labelled 1A dc, and does it very comfortably, secondary 
resistance 14 ohms.

2250/0/2250, no current rating but 50% bigger/heavier than the other 
two. Carries a plate specifying "use with choke part number...". Each 
leg of the winding is 105 ohms - or 52.5 ohms if reconfigured for a fwb 
2250V winding.

These are very crude figures, and there are unknown variables and design 
requirements, but the 4:1 ratio is somewhere around what I remember from 
previous measurements.

I'd expect to be able to scale the resistances up with increasing 
voltage and down with increasing current and use that as a guide.

Steve


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