170M5112 is an Eaton Bussmann series high-speed square body fuse, rated at 630 amps and 690 volts.
It is designed for protecting power converters, rectifiers, and variable speed drives.

Bussmann Fuse, Semiconductor Fuse, Time Delay Fuse, High Speed Fuse, Class J Fuse, Class T Fuse, Class cc fuse, Class RK1 Fuse, Class RK5 Fuse, Class L Fuse, DC Contactor, Disconnect Switch, Car Fuse, Current Limiting Fuse, HV Fuse, Bussmann Fuse Holder, AC Fuse, DC Fuse
You can ask any Bussmann fuse and fuse cross reference(Littelfuse, Mersen, etc).