Optimization of an Actively Shielded Air-Core Superconducting Transformer

Air-core superconducting transformers incorporate the function of shunt reactors, thus they can be used in highvoltage high-capacity applications. They result lighter than their traditional counterpart while requiring heavy metallic shields. However they may represent an effective alternative to traditional transformers only if the weight and clearance reduction is accompanied by acceptable values of magnetizing current and leakage fluxes. The reduction of the leakage fluxes allows the reduction of the metallic shield size leading to an enhancement of the weight advantage. In addition the value of the mutual inductance should fit the shunt reactor action requirement. These objectives can be achieved by the active shielding technique. The paper proposes to properly design both the transformer and its active shield by means of a combined optimization stochastic algorithm. The procedure outlined is applied to a three-phase transformer layout.