Why would you protect a 120-277 LED driver with a fuse that is 600V rated
Fuses that are rated for higher voltage (and maybe higher breaking current) have less tendency to arc, so they tend to open up faster and may be better for protecting semiconductors.
The manufacturer may have found, by actual testing, an &quot;off label&quot; use for the fuse that is cheaper and/or more available than one designed specifically for I2T characteristics.