Which type of large electric motor (>500 HP) applications require/ prefer DC motors and Which AC?
Large fixed speed motors are typically AC synchronous motors or induction AC motors. DC motors are used typically in applications that either reuire reversing direction, or precise speed control. You can accomplish fine speed control with AC motors, it requires massive Variable Frequency Drives. An example of DC motors: AK Steel slab mill in Middletown, Ohio uses 75,000 HP DC reversing motors to roll out ingots into slabs of hot steel, then slabs into plate and then coil stock. I couldn’t imagine the VFD required to control speed on that size motor plus the serious issue of needing to reverse direction.
