Hi Richard,
I don't claim to be an expert but have you tried the
back of Belden's catalogue to see if it compares?
***** Begin Quoted Material *****
Current Degree Rise above ambient
Amps 10 C 35C
17 10 AWG 14 AWG
-----
No. of Conductors Factors
1 1.6
2-3 1.0
4-5 0.8
6-15 0.7
16-30 0.5
***** End Quoted Material *****
The decrease in factors is a result of external wires
thermally insulating interior wires of a wire bundle.
Regards, Doug
At 01:47 PM 11/3/98 +0000, Richard Steele wrote:
>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
>
>Attachment Converted: "D:\Documents\Web Docs\vcard7.vcf"
>
