As I understand it, the 75C value in table 9 is the _conductor_ temperature, caused by the combination of self heating and ambient temperature.

Ampacity of a conductor is set by the current which, if carried on a continuous basis in the specified ambient conditions, would cause the conductor to self heat to its temperature limit. In theory, if you had exactly the conditions used to calculate table 310.16, and you ran say 100 A through each of a set of 3 #3 conductors bundled together, then the copper would heat up to 75C. For what its worth, the calculations of table 310.16 are _very_ conservative with respect to thermal conductivity to ambient, and conductors are rarely continuously 100% loaded if they are sized per NEC calculations, so it is rare to actually find conductors that self heat to the temperatures limits.

The notes to table 9 show how the 'effective Z' is calculated, allowing you to calculate Ze from wire resistance and wire reactance it for any power factor. The notes to table _8_ give the calculation used to adjust resistance for different conductor temperatures.

IMHO even if you are using 90C rated conductors, it is _very_ likely that the conductor temperature will be well below 75C, and that the resistance of the conductor will be below that given in table 9.

-Jon