rakes do need modification to go HOG
a good example of that are the EMU's in Mumbai. for years, having stayed in DC traction, we were never aware about what it meant to have neutral zones :P so once Mumbai started going under AC, areas progressively started getting the feel of lights and fans going off randomly, in middle of no where during your journey. the problem got more attention once they moved beyond Kalyan/Borivali and eventually the problem was solved by having a small pair of LED lights in coach that stayed lit even in NZ (the main lighting supply+fans go out).
for...
more... long distance trains too the lighting supply is on battery, but AC supply isn't, and that is affecting cooling
hence wanted to know if the imported rakes had such problems originally.