Answer / k.prakashchandra

In usual practice, the carrying capacity of copper is taken
as 2.5 A/sq mm and 1.5 for Al.If the load is steady and
continuous 60 % of these values are adopted.

Answer / jamil

According to NEC , i want to reduced grounding cable from
4mm2 to 2.5 mm2 ,can u give me technical sheet to depend it
from NEC

Answer / hari

Cable size should be 25 Sq.mm

For Ex: 1000A MCCB
For Al - We have to Consider 0.8/Sq.mm
For Cu - We have to Consider 1.6/Sq.mm

For 1000A = 1000*0.8
= 800A
We have to go for (100X10)mm Bus Bar

Answer / balraj.gabriel

There is no formula for calculating the cable size. Usually
the cables are sizing based on standards like NEC,BEC.,
etc. if you want to size the cable you first choose the
std, which is using in ur location.as per NEC std just
multiply the 100*1.25=125A, choose the cable ( table-
310.16) for that size. after you choose the cable you have
to derate the cable for your laying location & way of
laying.

Answer / shirish

Theory for Cable Sizing.
From Ohms law, the voltage drop in an electrical conductor is
V = I R
where
I = Current, amps
R = Resistance, Ohms

The electrical resistance can be derived from the properties of the conductor material.
R = ρ L / A
where
ρ = Resistivity, Ω mm2 /m
L = Length, m
A = Cross sectional area, mm2
Watch the units in the above equation.

The resistance can also be expressed in terms of the material conductivity (ψ) which is just the reciprocal of the resistivity.
R = L / (ψ A)

Table 1. Typical material electrical conductivity
Material Conductivity, ψ
Copper 58
Aluminium 36
Mild Steel 7.7

Combining Ohms law with the resistance expression, we get.
V = (I L) / (ψ A)

Now, we can define an acceptable voltage drop in a conductor. I have calculated the voltage drop that was used in several published tables and get around 5.5 Volts.
We could therefore re-arrange this equation to give the cable size. But cables come in standard sizes measured in mm2. In addition, you also need to consider the maximum current for each cable size.

Table 2. Conductor sizes and maximum currents
Cable Size, mm2 1.5 2.5 4 6 10 16 25 35 50 70 95 120 150 185 240 300
Maximum current, A 13 21 28 36 46 61 81 99 125 160 195 220 250 285 340 395
So, the theory is relatively simple, let us now see how to use the program.

Answer / amrish sharma

there is no funda or formula to get size of conductor wrt
to load. just calculate the ampere of the load, and then as
per ampere ,,, as per the cross sectional area of the
conducter like 1.5mmsq can bear the 4-6amp load,,,so on..

how many mega ohms insullation of the cable can't be use when testing with megger tester for Low voltage cable 240V use?

3 Answers  

How do you protect your appliances from harm in case of neutral failure in a three phase power supply set up.

4 Answers  

Why we not use the impedance relay in protection of short transmission line ?

4 Answers  

What is CCT (Correlated Color Temperature) ?

0 Answers  

if we have to design a small transformer of rating 1 kva or 1 mva , how can we design it?

1 Answers  

What is difference between Over Current & Earth Fault protection?

0 Answers   ABC,

what is the relation b/w KW and KWH? plz explain with example.

6 Answers   FAG,

Is it possible to protect 3phase overload and earth fault of the 3phase system using two CT's.

0 Answers  

What is oil temprature with A/T contacts in Transformer ?

1 Answers  

What is meant by unilitrel device?plz tell about h-parametrs

1 Answers  

What is the principle of residual protection?

0 Answers  

please write motor, transformer, Generator setting, fault level calculation of Tr.etc

0 Answers