What would be the size of cable if connected load is 40kw?how it calculated?

Question

What would be the size of cable if connected load is 40kw?how it calculated?

Answer 1

How long is the cable, and how is it routed.

If its buried, laid in tre-foil or suspended in air different derating factors apply.

The length of the run is important too, in that the longer the run the more volt drop you produce. Sometimes you need to oversize the cable compared to its pure current carrying capacity.

In general, look up the current carrying capacity and derate it by a factor determined by its arrangement. If the cables are routed in numerous formations along the length derate with the highest factor.

I would recommend at LEAST 25mm^2 cross section cable. This will allow you to derate it by about a factor of 0.71 which should cover most types of routing.

This is assuming a 2 core + Earth cable laid on its own or spaced away from other cables. (maximum 600V source)

Insulation X-90, X-HF-90, R-EP-90, R-CPE-90,

R-HF-90 OR R-CSP-90 INSULATION

Answer 2

Cables are sized on amperage.

Whats the voltage ?

What's the maximum operating temperature?

Is the cable in air or in duct?

What's the allowable voltage drop?

Answer 3

The size of a cable is firstly determined by the material used, is it copper or is it aluminium? different materials have different current carrying capacity. Secondly is it a 3 phase or single phase load. Third the current carrying capacity is determined by calculating the design current and then applying any relevant correction factors such as how the cable is installed, if the cable is grouped with other cables, what the surrounding or ambient temperature is and if the cable is in contact with or surrounded by thermal insulation. These factors affect the cable's ability to dissipate heat and hence its current carrying capacity

Assume a certain cable is installed on a metal cable tray this cable gets rid of the heat easily and will in this situation have a high current carrying capacity. If the same cable is surrounded by thermal insulation its current carrying capacity is greatly reduced.

Conclusion:-  your question does not contain many of the facts required to give a definite answer. In reality cable calculations are complicated and should only be carried out by a suitably competent electrical engineer

But to give some kind of answer here are 2 simple examples for copper cable

Assume 3 phase load 400 V minimum current carrying capacity 58 amps per phase worst case about 116 amps per phase

3 phase 480V minimum current 48 Amps per phase worst case approx 100 amp per phase

UK 3 phase cables between 10mm sq and 25mm sq

USA 3 phase cables between 4 AWG and 1 AWG



See source site below

Answer 4

We need more information. What is the supply voltage and number of phases?  

Answer 5

There are many factors affecting the cable sizing.

Click on the following link and download demo version:

http://www.designelectricalpro.com/produ...

Search for The "AC43-13b Acceptable Methods and Standards"

Its an FAA Publication.

for selection,click on:

http://www.boatus.com/boattech/cable.htm

P =[1.732 * V * I * PF] / 1000

P=1.732 *415*0.9*I/1000

40*1000/1.732*415*0.9=I

I=61.83 ampere.

USE 8 AWG CABLE.

Answer 6

40kw divided by voltage = current in Amps.

if its 415v    its 40000w/415v =96.4 Amps.

so you need 100 Amp cable.