We're almost on common ground now! I want to determine the thermal "bottlenecks" within the electric motor. This by doing a lumped system analysis of the motor, e.g. determining all the different thermal resistances of the different parts of the motor. I choose the copper winding cores as the primary heat source, so that the motor heats up from the windings. The heat flow is equivalent with the copper loss term. So that would mean P=I^2 * R, which is the current source in the model ( one of many, every loss term is equal to a current injection within the thermal resistance network).
So yes i do agree with your story. BUT, back to the question, to determine the thermal (equivalent) resistance of the windings, including their insulation within the stator slots, I'd like to introduce only ONE thermal resistance. This means I want to bypass the fact that there are 780 different conductors running through 1/18 th of the motor, with each of those 780 conductors/wires their own insulation. To bypass this, I need to know if I can determine a thermal conductivity term (k) which is a "educated guess" of the complete thermal conductivity value of copper+insulation.
I just want to simplify the winding part of the thermal model, so all the other resistances, e.g. radiation and convection, plus conduction to the rotor part of the motor are all evaluated.