>doesn't the amperage go up proportionally to the voltage going down?
To output the same horsepower, yes. But odds are that the motors are not being asked to perform full rated load.
In other words, a 50 HP motor at 575 V is a 10 HP motor at 120 V.
Simply derate the horsepower by 20-25% and the amps probably won't be a problem. The lower voltage probably is not as efficient.
