From what I know, the key to reducing losses due to eddy currents in a core is to reduce the path that they take, as is shown in this diagram illustrating solid vs. laminated cores (courtesy of Wikipedia).
Would taking this one step further and making the core a bundle of wires/rods instead of a stack of laminations reduce the losses further? If so, then why aren't there any commercial designs using it?
What stands between each lamination ? Isolator. If you switch from lamination to wires, you'll get much more isolator, and therefore less metal in the same volume of core. Doing so, you'll get a less efficient core, you'll have to increase its size, increasing cost, wire length on the coils, losses in the wires and that's often a bigger drawback than the benefit in metal losses reduction. I'm also doubtful about the mechanical resistance of such core.
