It's been awhile, and it's my sincere hope this message/question finds you well. I've changed jobs since our last communique and work installing fiber optic current and voltage sensors for power generating stations and the higher voltage class substations. Our sensors are competitive with conventional CT's and VT's down to about 138kV.
My question is what does the output of the secondary of a toroid with 3 primary inputs (windings) that are square waves with 40khz, 20khz and 10khz respectively look like? I mean, I'm having a real difficult time wrapping my mind around why the use of the toroid to combine the 3 inputs. The coil would not have much of the way of either step up or step down. What purpose can you think of would constitute the need for this transformer?