@StevefromPA prewar in general used more voltage.
Look at the prewar Z for example, it tops out at 25v. A later ZW is 20v. (The Z counted on external whistle boxes that ate 5v. The ZW separates 5v worth of windings and sends it straight to the internal whistle circuit, leaving 20v worth of windings for the throttles/acc..)
The other difference is, it is likely it was a 50hz system there, but in the states we mostly use 60hz. Good news is that the 50hz motors characteristics on 60hz should all improve slightly.
The question is would the 20v rating be like saying our motors are a 12v (cruising speed, most efficient), or 20v (max "safe" voltage)¿? ; Because there were 40-50v trains...which I imagine would run at slowish prototypical speed at 20v. I.e. it may be half speed at full throttle, or will run just like most prewar, but it should run. With lite tin behind it, you'd be ok even if it was high volt I think.
