Thanks Steve for putting the reasons in words I can understand. I can
not see the secondary wire size as it is in a sealed metal case, but
with the size of the case 8x6 , 7.5 high and heavy I think it will hold
up. I did not know the difference in the way they were made, the
original output was for .450ma but that was CCS service I am sure.
Rich, kd0zz
>>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
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