[Amps] CD Cap

[Steve Thompson]

>>This also brings up another question, I am going to use an old
> 
> transformer. It has 230v input, three input terminals, out put is with
> terminals 1-2, 3000vac, with terminals 1-3 ,2090vac. Resistance is
> .45ohms 
> input(1-2) or 1.02ohms input (1-3), output R is 41.4 ohms at terminal
> 4-5. 
> In another thread it was brought up about transformers for a choke input
> might be a problem?? How do I tell and why do I care? 

It's worth caring because of the nuisance if your transformer dies. Any 
replacement you find is bound to be 1" too big somewhere.

If a transformer is intended for choke input operation, the secondary 
current is (to a very crude approximation) constant and roughly the the 
same value as the dc. In capacitor input the current flows in short 
peaks - again very roughly - 3x the dc for 1/3rd of the time. Since 
heating  comes from I^2, the same secondary winding resistance and same 
dc current results in 3x the heating in the secondary. In a transformer 
for choke input, the manufacturer will often save money and space by 
using thinner wire, resulting in higher resistance. If you then use that 
with cap input, things can get stinking hot.

My gut feel is that your 41ohm winding will be fine with cap input, 
probably up to 0.5Adc or so, and you caps will be running at below 50% 
ripple rating.

Steve