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FEMM
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by Dr Stan Zurek

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====== Real and Imaginary values of L and R ======

In DC simulations (f = 0 Hz) the circuit property results are simple real number denoting the peak values of current and voltage, and direct values of inductance L and resistance R. 

However, in AC simulations (with f > 0 Hz) the circuit property shows inductance L and resistance R as complex numbers with real and imaginary components. 

{{re_and_im_l_and_r.png}}

For example, in the figure above at 50 Hz, the inductance L is:

  Flux/Current = 0.00998433-I*2.38572e-005 Henries

and the resistance R is:

  Voltage/Current = 0.183112+I*3.13667 Ohms

The meaning of these values is such that the real value of inductance (L re = 0.00998433 H) represents the actual inductance of the winding, and it is also directly linked to the imaginary part of resistance, so that R im = L re * 2 * pi * f. Hence:

  R im = 0.00998433 * 2 * 3.14159 * 50 = 3.1367 Ohms
  
And vice versa, L re = R im / (2 * pi * f).

Unofficial FEMM documentation by Dr Stan Zurek

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Unofficial
FEMM
documentation
by Dr Stan Zurek