GENERIC FIELD PROBLEMS IN DESIGN STUDIES OF HIGH TEMPERATURE SUPERCONDUCTING TRANSFORMERS

A feasibility study for a large power transformer reveals several key design issues, each of which is expressible in terms of simple, fundamental field effects. Six generic effects are briefly reviewed and their importance explained. In all cases but one their influence can be estimated, to an accuracy adequate for feasibility purposes, without computation or detailed analysis. They are: mechanical stress due to magnetic fields; electrical breakdown caused by winding capacitance distribution; dielectric breakdown caused by the mixing of different materials, including liquid nitrogen; reduction of critical current density due to internal magnetic fields; the need, or otherwise, for conductor transposition; modelling of field penetration and ac losses in HTc superconductors.