Calculation of mutual inductances by means of the toroidal multipole expansion method

A method is proposed for the calculation of mutual inductances in axisymmetric iron-free current systems. It is based on a toroidal multipole expansion of the magnetic flux function. The mutual inductance is expressed by means of a series of toroidal multipole moments of the two currents. Each term of the series is the product of the internal moment of one of the two currents and the corresponding external moment of the other one. The method can be applied to any axisymmetric current system independently of the current distribution. An example application is presented