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..

Draw the equivalent circuit of crystal oscillator?

0 Answers  

What is the previous name of Cox's Bazar

0 Answers  

An 8 pole, 50 Hz, 3-phase IM is loaded to a poing where pull out torque will occur. The rotor resistance per phase is 0.3 ohm and motor stalls at 650 rpm. The rotor frequency at maximum torque point is A 3.33% B 4.44% C 5.55% D 6.66%

1 Answers  

WHAT DRESS I SHOULD WEAR WHILE ATTENDING AN INTERVIEW? PLEASE SPECIFY THE STYLE AND COLOUR. CAN A LADY WEAR CHUDIDAR FOR AN INTERVIEW?

6 Answers   Wipro,

what is destructive and non-destructive testing of welding

0 Answers  

HOW TO BUILD THE SINGLE PHASE TO THREE PHASE CONVERTER? CAN PROVIDE ME CIRCUIT..THANKS

0 Answers  

Which type of gas used in cylinder (VCB)?????

15 Answers   ICSA,

pls tell about gas insulated substation?which gas is used for that substation?above which rating we are used this substation?how we take maintenance in that substation?it means substation fully shutdown or live condition?if live condition means how?pls clear this things

1 Answers   Essar,

Pls anyone explain me the basics of wiring a house?

3 Answers  

Can we connect two or more energy meters/Amp meters on one CT set(Three phase).

5 Answers   Parle, Watermark Engineering,

How much CTs are required to measure th curent in DOL starting of motor?PLs explain.

1 Answers  

we all know that in transformer, voltage and current are inversely related i.e. Vp/Vs= Is/Ip....so in standard CT..we have a ratio of 200/5...that means our voltage should increase by ratio of 40..althoug that is not the case...because that requires high insulation level.and pratically not feasible......can anybody clarify my ques.......thanx

2 Answers