Just had an idea that raised a few questions and I can't find any relevant data on after a bit of searching so thought I'd ask here. If you were to make a transformer entirely encased in superconducting material would it result in a significant step toward and ideal transformer or is magnetic flux confinement not that much of an issue? Would it have any noticeable change? What if you were to make everything out of insulated superconducting materials (the core, the windings and a case to ensure none of the magnetic flux escaped)? If it makes a difference, please assume the casing would be deposited directly against the windings and core insulation so all that actually exists between the different components would be insulation of negligable thickness (just enough to avoid arcing).