The voltage rating on a 5 x 20 fuse is related to its disintegration characteristics during the time the fuse element is burning up. A higher voltage rated fuse element disintegrates faster to prevent arcing while the element is burning up. This is not to be confused with the time it takes for the fuse element to begin destructing which would be designated by slo-blo, fast-blo, time-delay, or other letters.
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