Inductance calculations for coils with an iron core of arbitrary axial position

A semi-analytical method is proposed to calculate the magnetic field and inductances of axisymmetric iron-core coils. A group of source functions are introduced to simplify the formulas and accelerate calculation. Compared to previous researches, with the help of the source functions, the relative locations of the coil and the core in axial direction can be arbitrary, which extend the application range of the method. The results evaluated by the proposed method are compared with those given by finite element method (FEM), from which it is confirmed that the proposed method is effective and much faster than FEM simulations under the same calculation accuracy.