Re: Inductance using FEMM

[jim271@xxxxxxxxxxx]

Example of using FEMM to find the inductance of a coil with the 
dimensions and number of turns specified:

Wire gauge = 18AWG
Max current goal = 100 Amps.
Voltage = 340 V.

Dimensions (using the MGC calculator): 
Length = 12 inches = 0.304m
Inner radius = 0.156 inch
Outer radius = 0.56 inch
Coil thickness = 0.56-0.156 = 0.404inch = 0.0102m

Cross sectional area of winding = 0.304*0.0102 =0.003101m^2

Current = 88.4 Amps per turn
(the current is less than the specified 100amps because the 
calculator assumes each layer of the coil is fully wound.)

Number of turns = 3152

Total current = 3152*88.4 = 278637 = 0.2786 MegAmps

J = Current density = 0.2786/0.003101 = 89.8MA/m^2

Use this value of J for the copper in your FEMM model.

Run FEMM and highlight the copper, read integral(A.J)

Inductance = integral(A.J)/(88.4*88.4)

This should be pretty close to the value from the calculator (8.93mH) 
which was obtained using Wheeler's formula.

-- Jim