Amtrak still uses motor-generators on some parts of the Northeast Corridor to convert 60 Hz AC grid power to 25 Hz AC traction power. It's exactly what it soun

Amtrak still uses motor-generators on some parts of the Northeast Corridor to convert 60 Hz AC grid power to 25 Hz AC traction power. It's exactly what it sounds like: a motor that is mechanically coupled to a generator. The motor runs on 60 Hz AC and turns the generator at the correct speed to produce 25 Hz AC.