Numerical calculations of internal impedance of solid and tubular cylindrical conductors under large parameters

When calculating the internal impedance of solid or tubular cylindrical conductors, Bessel functions are involved if the skin effect has to be taken into account. Under unfavourable conditions, large parameters of the Bessel functions will occur, which will lead to unreliable results if the Bessel series are computed directly. Using the polynomial approximations of Bessel functions, closed-form formulas are developed to deal with this problem. For the convenience of applications, several sets of curves, for both the skin effect resistance ratio and internal inductance ratio of solid and tubular cylindrical conductors, which cover different ranges of parameters, are presented.