[marzetti]

I have some used transformers that may be useful for power supplies but I have no way of determining what current they are rated for. Any ideas?

[Al_The_Man]

The Va is calculated using core size and current rating of conductors etc.
This link may help.
Guide to Transformers Part 3
Al.

[marzetti]

Thanks Al. There's a lot to digest there for a newbie such as myself but if I understand what I have read I will need to obtain or build a constant current source. Any suggestions on that?

[Al_The_Man]

What is your application?
Al.

[marzetti]

I intend to use this transformer to power a linear positioning system. I need ~2A @24V.
Comparing this transformer to another 50VA I have I'm guessing it is more than adequate based on weight. So it seems the easiest route would be to just try it in a power supply and see if it heats up too much. Does that sound reasonable?

[Al_The_Man]

If the core size is comparable or larger than your other TXfmr, Then most likely it will be OK, the other thing is wire gauge, but at 2amps it would have to be 20g or smaller to be under sized.
You could always make up a supply and put a 2a load on it and see if the voltage collapses that much or you get overheating.
It would requires a 50w 10/12ohm resistor however, for temporary tests, Automotive lamps or old stove elements etc can be recruited for temporary loads/testing.
Al.