Analytical field calculations for various helical conductors

Analytical methods have been developed for the electromagnetic calculation of helical coils, the inductance of a twisted bifilar lead, and the current distribution of commonly used twisted superconducting multistrand cables and composites. These methods are based on the analytical expressions of the magnetic field and the vector potential resulting from a single helical thin conductor. The current distributions among each strand or filament within a twisted superconducting multistrand cable or multifilamentary composite are obtained using the principle of a minimum magnetic energy in the case of insulated strands or filaments and the condition of zero enclosed magnetic flux for noninsulated strands or filaments.