Variational expressions of inductances of coupled annular rings

Variational expressions are presented for the self and mutual inductances of coupled annular rings for the first time. Two independent analytical procedures are developed to afford the variational expressions of inductance matrix and its inverse matrix. Numerical computations are performed by using the appropriate sets of basis functions, and they clarify the range of errors and show that the errors can be reduced systematically. Conductor thickness effect is also investigated.