I have a device of copper and iron (about 8 kg) which looks like two shell inductors joined so that there is some coupling but high leakage. The windings seem to be identical. Each is a single continuous winding with 4 intermediate taps. I did not see this in use, but when I got it the two windings were linked at one end. The equipment it came from was powered, I think, from normal 240 VAC mains.
It's just my curiosity, but I can't fathom what it might do. Since the windings were linked, it does not provide isolation. If it is a transformer or common mode choke, why so little coupling? If it is two independent auto transformers or chokes, isn't the coupling a problem?
Anyone seen one at work anywhere?