I am trying to understand how a transformer composed as pictured would function. Basically, two separate cores. Both cores go through the secondary winding. But only one of the cores goes through the primary, and the last winding (lets call it the "control" winding..you know where I am going with this..) goes around the last core.
So yes, ultimately I am wondering if you could manipulate the amount of net flux the secondary winding experiences by driving the control winding with the right phase and magnitude to achieve your goals. Goals being a reduced voltage at the secondary compared to what it would be with the control winding open.
The key benefit here is that the net flux that the secondary experiences is reduced, without reducing the flux the primary generates, and therefore, without reducing the inductance of the primary, which would allow more primary current to flow, and is what would happen if you tried this with a single-core transformer.
I have seen this sort of thing called a "three port magnetic component" with a brief discussion here: https://www.researchgate.net/post/Can_anyone_advise_me_on_how_to_build_a_multicore_transformer
LTSPICE will reject modelling of this component if the coupling constants between the inductors is not physically realizable Unfortunately I do not know what that means beyond a very general idea that some coupling will always occur. I would like to know where I can learn exactly how to calculate the "inductance matrix" and solve this myself, and why it is so at an intuitive level.
So I'm looking for an intuitive and algebraic way to understand why the reality deviates from the ideal here.
It seems to me "magnetic amplifiers/saturable reactors" are not this thing.