What the ratings mean for your board
The 045101.6NR is a Littelfuse NANO²® 451 series fast-blow fuse rated 1.6 A at 125 V AC or DC. The 50 A breaking capacity at rated voltage means it can safely interrupt a short-circuit fault up to that current without rupturing — adequate for secondary-side protection in a 125 VDC rail where the available fault current stays under that ceiling. The melting I²t of 1.06 A²s tells you how much energy the fuse absorbs before opening — useful when sizing the fuse to ride through inrush current from a capacitive input or a motor start without nuisance blowing. Approved by CSA, cULus, and PSE, so it is accepted in North American and Japanese equipment without additional agency testing.
Lifecycle reality — obsolete, sourced per RFQ
Littelfuse lists the 045101.6NR as obsolete.