morgan3520
Member
- Location
- Dallas, TX
- Occupation
- Electrical Engineer
Thanks, but what does the "attainment factor" represents?The ampacity current I=sqrt(Tc-(Ta+ΔTd)/(Rdc*(1+Yc)*Rca')
Rca'=Ri+qs*Rse+qe*Re'
Re'=0.012*ρe*n'*{log(Dx/De)+LF*log[(4*L/Dx)*F]}
So, in order to calculate Re'[outside thermal resistance] we need to know Dx
the fiction diameter of the last part of the thermal circuit.
If you know the diffusivity of the medium and the thermal cycle duration you may use
formula (45) Dx=1.02*sqrt(α*length of cycle) .If you don’t then use equation (67)
log(Dx/De)=83/n'/ρ*[(1-x)*Rea-x*Rce] where x=(1-AF)/(1-LF).