how much current capacity of 300 sq. mm cable (4 core
aluminium) and 150 sq. mm cable ( 4 core aluminium)
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Answer Posted / 7anoter4
It depends on lot of factors. The duration of the load:
short-time[as in short-circuit case],continuous load,
intermittent load. It depends on also on ambient type [air,
underground-direct laid or in concreted duct],on thermal
resistivity of the ambient [if it is in underground],on
ambient temperature, on insulation type[bare, pvc, xlpe,
epr etc.] and other factors.
Let's say in short-circuit case for 1 sec 300 square mm
aluminum conductor pvc insulated. Permissible temperature
[for PVC short-time]= 150oC.Ambient air 30oC.
Ipermissible=27 kA[27000 A].
For the same cable in open air 30oC[NEC Table 310.15(B)
(17)] continuous load [75 oC]600 MCM=300 sqr.mm permissible
545 A
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