[Amps] Transformer guess?

[Manfred Mornhinweg]

Vic,

> What I want to know is how much DC I can draw from the HV winding
> with a full-wave CT circuit. 

A simple rule for small transformers is that they are designed to have a 
voltage drop of close to 5% in each winding (10% total). This figure can 
vary a little, but not very much. At least it gives a reasonably close 
idea. So, take out your multimeter, measure the resistance of the 
windings, and apply Ohm's Law, using 5% of each winding's voltage. That 
will give you the approximate current rating of each winding.

It might be good to measure both the primary and secondary windings, 
calculate the current for each, and see how well the two power ratings 
match. They should be very close, of course. If there is a large 
difference, you either have made a mistake, or the transformer is poorly 
designed!

Note that this 5% voltage drop per winding is typical only for medium 
size transformers. Very small ones, like those in wall warts, tend to 
run with higher voltage drop, 10% or even more per winding, while large 
transformers run with ever smaller voltage drops, as size increases. The 
truck-size jobs at the town's substation certainly drop less than 1% per 
winding!

Manfred

========================
Visit my hobby homepage!
http://ludens.cl
========================