Cable Sizing for Motors

[Beta101]

Hi All,

I was wondering if anyone in this forum can refer me to any document online or website that discuss electrical cable selection and rating.

Regards

 

[alexit]

Go to here:

http://www.lappusa.com/140contents.htm

And look at "National Electric Code Allowable Conductor Ampacity", there are four tables to refer to when sizing conductor to this standard.

 

[msherb]

Depending on where you live, there are several codes you are required to follow. In the USA, you will be safe with NFPA 70, which is also known as the National Electric Code (NEC). YOu will specifically be looking for the tables unde NEC 310.16 (?) I believe. If you don't feel like ponying up the $150 for the standard, the tables are reprinted in every Ugly's electrical reference book (little yellow handbook every electrician should have). You can pick one of these up for about $15 at you local bookstore.

 

[waross]

For motors see also NEC 430... Specifically NEC 430.22 Which requires the conductors for a single motor to have 1245 ampacity, and requires conductors for a group of motors to have an ampacity of 100% PLUS 25% of the current rating of the largest motor.
The Canadian Electrical code also specifies minimum temperature ratings for motor circuit conductors and the temperature rating that must be used for sizing motor conductors.