Dear All, I'm trying to make sure that some conductors carrying 230V r.m.s in an ambient temperature of 70oC have a large enough conductor and the correct insulation to withstand a short circuit current of 17A for 30 minutes.
Does anyone know which formulae are appropriate? I have tried the calculations in BS7454 : 1991 "Calculations of thermally permissible short-circuit currents, taking into account non-adiabatic heating effects" and the results don't seem to make sense. So here are the parameters Max current = 17A Start temp - 20oC Conductor size - 1.5mm2 Time period - 30 mins Conductors not bunched I'm trying to find out what the final PVC insulation temperature will be, all the catalogues that I have only seem to give the current at 20 or 30oC. The results I have are: Adiabatic - 23291.48oC Non-adiabatic - 34.48oC The results are supposed to give the final temperature. For the non-adiabatic result, is a 14oC rise what you would expect or is this the whole rise 20 + 34.48 = 54.48oC? Are there any wire experts out there? Regards Richard
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