Determining transformer current rating

[Jeff1946]

I have a few unmarked AC power transformers I have removed from various electronic devices.  It's easy to measure the voltage.  How to I determine the current.  My thought-- put various loads on and note the voltage drop. My guess would be about 10% drop maximum.   Then I would leave this load on and see how warm the transformer gets.  Any other suggestions?

[BravoV]

Had similar question while a go at when I mod my isolation transformer, a fellow here pointed out few useful hints -> https://www.eevblog.com/forum/projects-designs-and-technical-stuff/modding-an-isolation-transformer-please-advise/msg80157/#msg80157

Hope this helps.

[IanB]

To give you an idea, here is a load graph I plotted of a transformer marked 12 V  2 A. I think checking it doesn't get too warm after leaving it running for a while is the best option you have for figuring out the current rating.