02. Coil Inductance Calculation Comparisons

A comparison of coil inductance calculations comparing the Wheeler equation for multilayer coils with inductance calculations using Finite Element Modelling (specifically the FEMM program) had been performed. Results were documented at this link: http://www.femm.info/wiki/AirCore

A summary of the Wheeler equations for inductance of air core coils is at this link: http://home.earthlink.net/~jimlux/hv/wheeler.htm

The programs TBCALC.EXE and SFCALC.EXE have been used to make calculations of Inductances of the same coils. In doing this, tube properties in TUBECALC.EXE were given the properties of free space (electrical conductivity = 0 and relative magnetic permeability = 1). Similarly, the plate properties in SFCALC.EXE were given the properties of free space (conductivity = 0 and relative magnetic permeability = 1). With an excitation current of 1 Ampere used in the transmit coil, the voltage induced in the detector coil (with same dimensions of transmit coil and separation between the coils = 1 E-10 m) was calculated at 100 kHz test frequency. The calculated voltage was divided by 2 x pi x 100000 Hz to determine the coil inductance in Henries. Results of the comparisons are listed in the tables below. One table lists coil dimensions in inches, the other table lists the dimensions of the same coils in metres: