Correct cable sizing?

[pyare]

Hi guys,

I'm trying to learn the electrical wiring in a panel, I'd like to ask anyone here has a good link for me read up on how to calculate the correct cable sizing like for example: 415V AC, 3 phase, 65Amp?


Thanks.

Determination of cable size
vc=1000vd divide by L*I where
vc=voltage drop in millivolts per ampere per meter route length of the cct.
vd=actual voltage drop in volts
vp=permissible voltage drop on the cct.your country;you have to find it.
L=route length in meters;distance from load terminals to the point of supply.
I=current to be carried by the cable.

 

[CaseyK]

To size any electrical feed you first need to know the external earth loop impedance and the prospective fault current at the source you intend to feed from.

In most installations nowadays voltdrop is a bigger factor in sizing a cable than Ib. Therefore you also should know what percentage voltdrop has been allowed in the cabling to the source you are going feed your panel from!

Regards

Paul.

In 35 years of panel and switchgear building, I have had this information less then 12 times. The panel has to be able to deliver the required voltage and current no matter what is out there. If the voltage drop is too much, then the contactors should be located at the machine, or a more centralized MCC should be utilized.

On occasion, the utilities will perform a loop resistance, and require extra grounding for the service feed. In an industrial location, in the states, the NEC has specific requirements.

Agricultural settings have there guidelines, also. 'Specially if livestock are present.

 

[pouch]

These value are easily measured by any competant electrical person. These values are not just nice to have, they are a must have to any designer of electrical power installations. One of the main reasons there are far fewer electrical fires nowadays is the proper design of electrical circuits, using the tools readily available to all competant persons.

 

[S7Guy]

I will be starting on a large project in Chicago soon, and one of the requirements by the customer was that anyone who walked through the door had to have two days of arc flash training. I ended up taking a course presented by http://www.vincemay.com/ , and it was actually very interesting. As Pouch said, fault current calculations are being taken much more seriously now than they were before.