On a 75kva 3 phase transformer I use my Ugly's book to see that it is rated for 180 amps full load current. Looking at the allowable ampacities of conductors table I can see that using 75 C column and going to 180 amps that I can use 4/0 alum. or copper clad cable. When I inspected the transformer I found it to be wired with 4/0 paralled USE type cables. Was that over kill or why did they parallel the cables with 6 line conductors and 2 neutrals instead of using 3 line conductors and 1 neutral. I know it can't hurt to over size the wire (except cost and lug size in the panels). Thanks!