This will be an odd one to describe, but from a high power APC Symmetra UPS, these inductors are used in the AC output filter (HF sine wave). There are 3 of these per AC leg, in series, with no capacitors.
They are wound really odd, and I want to know why! (pictures below)
If you take a length of wire (about 10 feet?), feed 1/2 of the length through the core, and start winding BOTH ends away from the initial wire insertion point... BUT BOTH ENDS GO IN THE SAME DIRECTION around the toroid core... just wound in opposition (one wire leg goes CW, the other CCW).
When you finish winding (same number of turns on each wire leg), you end up with both ends of the wire arriving at the same point... and these are the terminations.
It somewhat reminds me of the Tesla Bifilar Flat coil... but on a toroid, and only one wire.
(If you're up for one more oddity, explain that 4-path small copper trace on the bottom side of the filter board - last image below. There's no connections to them)