Home › Electrical Engineering Forum › General Discussion › size of cable
 This topic has 3 replies, 3 voices, and was last updated 10 years, 1 month ago by Spir Georges GHALI.

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2011/02/02 at 3:26 pm #10372ghulam mujtabaParticipant
HI i am mujtaba want to know that how can we calculate size of cable as per requirement of load
2011/02/04 at 6:11 am #11799adminKeymasterist of all we'll calculate total kw of all componants, which are proposed to install on sable. then find out the ampers from power formula. and then we multiply the total amperes with 3, in case of inductive load. then we will select the suitable cable according to our calculated amperes from cable chart.
2011/02/15 at 7:42 pm #11823adminKeymasterwaqas said:
ist of all we'll calculate total kw of all componants, which are proposed to install on sable. then find out the ampers from power formula. and then we multiply the total amperes with 3, in case of inductive load. then we will select the suitable cable according to our calculated amperes from cable chart.
You can find a welding cable chart here of a basic amperage chart here.
2011/06/07 at 9:14 am #12146Spir Georges GHALIParticipantghulam mujtaba said:
HI i am mujtaba want to know that how can we calculate size of cable as per requirement of load
Dear ;
First, by knowing the load's power ” P “, the kind of load ” Single Phase or 3 Phases “, and the Cos φ, we can claculate the nominal current ” Ib ” of load by applying the formula :
– For single phase : Ib = P / V x Cos φ
– For 3 phases : Ib = P / 1.73 x U x Cos φ
where :
– V : voltage between phase & neutral
– U : voltage between 2 phases
Then you should decide or know the methode of installation of cables as we have many methode ( better to refer to IEC 345552 ), and the ambiant temperature, so, we can find the correction factors and the totat ” k “, so, we calculate the nominal current for cable in standard conditions ” Iz = Ib / k “, and by this value and the table of ” IEC 364552 ” we can do the choice of cable accordingly to the kind of cable ” Single or Multi “, ” Cu or Alu “, ” PVC or XLPE “.
After knowing the section, we should calculate the percentage of drop voltage of the cable, if the percentage is equal or less the standard values, the cable is OK, if not, we should ovesize the section of cable. But be carful that the standard values of Drop Voltage percentages are from Source to the load, that means all cables from the source ( transformer or generator ) to the load.
Regards.

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