OK, the 400Hz and 115V Ac is for weight issues, but what I'd like to know is whether the 3-phase electric motors used in aircraft systems are delta or star-wound?
If I recall, delta-wound motors don't require a neutral wire, thus saving weight again. I think US 3-phase domestic electric motors are always delta-wound whereas in the Antipodes where we have 415V 3-phase power we use star-winding which requires a fourth wire, the neutral - and woe betide your equipment if you have the dreaded "floating neutral"!
I'm guessing the aircraft 3-phase motors would therefore be delta-wound to save wire and thus save weight.