Method -1 We talk about 3 phase, heavy load, and Aluminium cable. According to Ampere load = near by available cable size Example-1, 60A load, here available cable near below 60 are 50 sqmm and 35 sqmm If the cable length below 100 mtrs we use 35 sqmm If the cable length above 100 mtrs we use 50 sqmm cable. Example-2, 300A load, here available cable near 300 are 300 sqmm and 240 sqmm If the cable length below 100 mtrs we use 240 sqmm cable and if the cable length above 100 mtrs we use 300 sqmm cable. You may use 2 run of 150 sqmm cable against 300 sqmm single cable. Similarly for 1000A load We use 3 run of 300 sqmm cable For 1600A load we use 5 run of 300 sqmm cable. For Copper cable multiply the Ampere by 1.2 and use above method. Method -2 For below 30A load and copper cable ...we just use Below 1KW load - 1.5 sqmm 2-3 KW load - 2.5 sqmm 3-5 KW load - 4 sqmm 5-9 KW load - 6 sqmm 9-12 KW load - 10 sqmm 12-16 KW load - 16 sqmm 16-25 KW load - 25 sqmm For aluminium cable Divide the load(KW) by 1.2 and use above method ☝️
If you want to use formula then I recommend use formula Power in KW(Load) = Volt x Current x power factor Example 3 phase load given 8 KW So, 8 KW = 8000W = 415(volt) x I(current) x 0.8 (pf) You Get I (current ) = 8000/(415*0.8) = 24A Now for safety I = 24 x 1.5 or 2 = 36 to 48 A Now search on google current capacity of Cu cable If you found 6 sqmm cable capacity = 33 A 10 sqmm cable capacity= 45 A And you calculate your current capacity= 36A to 48A According to your calculation 10 sqmm cable better for safety but you may use 6 sqmm cable too.
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How calculate that cable size
Method -1
We talk about 3 phase, heavy load, and Aluminium cable.
According to Ampere load = near by available cable size
Example-1, 60A load, here available cable near below 60 are 50 sqmm and 35 sqmm
If the cable length below 100 mtrs we use 35 sqmm
If the cable length above 100 mtrs we use 50 sqmm cable.
Example-2, 300A load, here available cable near 300 are 300 sqmm and 240 sqmm
If the cable length below 100 mtrs we use 240 sqmm cable and if the cable length above 100 mtrs we use 300 sqmm cable.
You may use 2 run of 150 sqmm cable against 300 sqmm single cable.
Similarly for 1000A load
We use 3 run of 300 sqmm cable
For 1600A load we use 5 run of 300 sqmm cable.
For Copper cable multiply the Ampere by 1.2 and use above method.
Method -2
For below 30A load and copper cable ...we just use
Below 1KW load - 1.5 sqmm
2-3 KW load - 2.5 sqmm
3-5 KW load - 4 sqmm
5-9 KW load - 6 sqmm
9-12 KW load - 10 sqmm
12-16 KW load - 16 sqmm
16-25 KW load - 25 sqmm
For aluminium cable
Divide the load(KW) by 1.2 and use above method ☝️
If you want to use formula then I recommend use formula
Power in KW(Load) = Volt x Current x power factor
Example 3 phase load given 8 KW
So, 8 KW = 8000W = 415(volt) x I(current) x 0.8 (pf)
You Get
I (current ) = 8000/(415*0.8) = 24A
Now for safety
I = 24 x 1.5 or 2 = 36 to 48 A
Now search on google current capacity of Cu cable
If you found
6 sqmm cable capacity = 33 A
10 sqmm cable capacity= 45 A
And you calculate your current capacity= 36A to 48A
According to your calculation 10 sqmm cable better for safety but you may use 6 sqmm cable too.