On Oct 31, 9:15*pm, wrote:
But these were from another era of much simpler multiple unit control
systems. What about modern units with computers?


There it gets more complex.

375/377 configure themselves by current limiting. Its been posted in
here a few times before, but in simple terms each traction pack (or
motor bogie) takes 750 A but once a train reaches or exceeds 4500(?)
A, the train computers divide loads equally across all working packs
but not at 750 A. Or something like that. In this way the performance
of 4x3 (8 packs) is equalised with 3x4 (9 packs).

450/444 are not as smart, they (I think) are 2000 A each 444 and 1500
A each 450 - but as there are less possible permutations actually
don't need to be as complex as 375/377 - in practical terms none of
those you;d find working a train exceed 4500 A.

Overall there are many other scenarios, 465s, 458s, 460s, 376s, are
all different, but the concept is the same, it all works by current
limiting and is not necessarily dependent on number of cars or packs
or motors in the train.

--
Nick