Most likely an AC motor, the question being whether it was an induction or synchronous motor. I have a vague recollection that the motors were re-geared, trading off some acceleration for higher top speed and using a shorter (lighter) train to get back some of the acceleration. With aero drag consuming all but a small fraction of tractive effort at top speed, I wouldn’t think that shifting gears would buy much.
Will the increased speed be worth the increased electricity that will be drawn to increase the speed? Can you estimate what the additional cost will be?
Typically how much does it costs to run the Acela at speed per mile. Are the Regional train engines cheaper to run than the Acela’s at the same speed?
The reason for mechanical transmissions that shift gears is to match the HP output of the prime mover, no matter what the type, with the vehicle speed. Railway vehicles typically have electrical “transmissions” and are limited at the low end current and at the high end by motor rotational speed. The constant HP portion of operation is pretty broad, generally. Even with a top speed over 300 mph, the limitations at the low end of the speed range probably aren’t a killer