fusing current
fusing current
(OP)
#14 AWG copper melts at 166A, but to calculate the I²T rating I need to know how many milliseconds it takes to melt at this current.
I know there is a link to this info but I've lost it.
Can anyone help?
I know there is a link to this info but I've lost it.
Can anyone help?






RE: fusing current
RE: fusing current
Is this a calculated value?
Do you have links to measured or calc'd values? The formula for fusing current is well known but I couldn't find time durations.
This would put the I²T value at 300,000 A²sec.
RE: fusing current
RE: fusing current
RE: fusing current
Sqr.mm=I*SQRT(A/B*t) or:
t[sec]=(Sqr.mm/I)^2*B/A
A=alpha*Ro*10^4/Tcap
alpha=0.00393 ohm/Co for copper
Ro=1.724
Tcap=3.422
B=ln(1+(TA-TB)/(K+TB))
TA=1084 Co[copper fuse temp.]
TB=40 Co[ambient]
K=234 Co for copper.
I=0.166 KA
Sqr.mm=2.08 for 14 AWG.
RE: fusing current
Try this..
Something I've had laying around for some time.
RE: fusing current
RE: fusing current
Just thought I'd save him the trouble. . .
RE: fusing current
Well deserved an star for the valuable information posted.
For application other than short duration for fusing bare conductor without static wind, adjustment may be required to account for the following effects:
* Conductor insulation on heat disipation for no bare conductors.
* Adiabatic or heat dissipation effect(include wind speed)
* Constant vs variable thermal capacity per unit volume
* Symmetric vs asymmetric (DC decrement factor, X/R ratio)
RE: fusing current
Bill
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