Non ideal inductor equivalent circuit
Here's my guess.  In the Intusoft paper, they are using the Rp to model core loss:
&quot;The magnetic loss can be modelled reasonably well as a parallel resistor (Rp) across the existing model.&quot;
That's actually a terrible way of modelling the magnetic losses in many applications, and LTSpice has a completely different way of taking core loss into account with its non-linear inductor models or with more complex equivalent circuits.
So the LT model's parallel resistance is probably there more for numerical convergence help in the simulator and/or insulation leakage rather than to model losses.
From LTWIKI:
&quot;By default, LTspice will supply losses to inductors to aid SMPS transient analysis. For SMPS, these losses are of usually of no consequence, but may be turned off if desired. On the &quot;Tools=&gt; Control Panel=&gt;Hacks!&quot; page, uncheck &quot;Supply a min. inductor damping if no Rpar is given.&quot;