Dual-element fuse derating for temperature

[brainsalad]

Hello,

Cooper-Bussmann has the following guide for derating their dual-element fuses for temperature:

http://www.cooperindustries.com/con...r_Derating_Ambient_Temperature_Correction.pdf

Does it make sense that for an elevated temperature of say 140F, I would have to derate my fuse for both current-carrying capacity as well as opening time (reflecting the two elements of the fuse)?

For example, my fuse is graphically made of a bunch of (Amp, time) points, and for 140F, I have a ~70% derating on time and an ~87% derating on current-carrying capacity, so to derate I should take my set of Amp, time points as (0.87*Amp, 0.7*time).

Thanks for your thoughts.

 

[PHovnanian]

The way I read the graph in that Bussmann pub is:

The "Carrying Capacity Rating" is the long time (asymptote) of the fuse operating curve. This will move to the left on a fuse curve with amps horizontally by the factor shown (0.87 @ 140C).

The "Opening Time" correction is applied to each point along the actual curve (actually both the melting and clearing curves) moving them down (time being vertical). Of course, the clearing time in the vicinity of 1/2 cycle will not be moved much.