# high voltage fuses

• posted

Hi,

I'm doing phd research on high voltage fuses. I would like to seek some opinion/advices regarding this matter. i have come across a formula derivate by I.M Onderdonk shown as below Ifuse = Area * sqrt(log((Tmelt-Tambient)/(234-Tambient)+1)/(Time*33))

where

Tmelt = melting temp of wire in deg C Tambient = ambient temp in deg C Time = melting time in seconds Ifuse = fusing current in amps Area = wire area in circular mils

However this equation is only valid for circular cross section. Does anybody know some useful information to calculate the current for non-circular cross section.

Nisa.

• posted

to seek

across a

sqrt(log((Tmelt-Tambient)/(234-Tambient)+1)/(Time*33))

section.

current for

as a semi educated guess on that issue I'd say it current would be a function of cross sectional area unless you got extreme, such as with a foil or whatever then its probably different due to the huge differences in survace area vs cross sectional area.

We could use an advance in high voltage fuse technology though and you might well be on the right track with your question that in the final analysis relates to surface area effects of the fuze element.

One of the problems presently is a delay in blowing the fuse on shorts that are less than bolted...resulting in dangerously extended delays for shorts through the human body etc.

Perhaps a foil type fuse element, in a multi element fuse would ablate away on modestly excessive current, causing an exponential rate of decay in the other elements below dead short conditions allowing for a net faster disruption of the flow. This foil element could be chemically alloyed to be primarily sensitive to electron flow not simply heat. Making the fuse less affected by variable ambient temperature conditions and more affected by current flow alone.

Phil Scott

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