400 metres of 16mm SWA cable, ....has this been supplied in a single length or is there any joints in this run?? I take it that this cable has been direct buried, so how did you pull this cable in for that 400 metre run?? I hope and pray you didn't use a tractor off the farm, cause if you did, the chances are, it's not a 16mm cable anymore. The other thing of course, ...is what sort of condition is that cable sheath in, even before any back filling with the excavated soil, that i'm going to put money on, hasn't been de-stoned or sifted!!!
I'm not going to mention the calc's for this cable, as others here, have covered that side of things.
I'd still be concerned about the starting current volt drop on this motor though, after 400 metres