3 phase cable selection and protective devices

[0ld1e]

Hi everyone.

I'm after abit of help calculating cables sizes and protective devices for a 3 phase DOL motor.
I haven't worked on 3 phase equipment for many years and 3 phase calculations is as far back as college so please excuse my ignorance on the subject and not knowing answers to perhaps basic questions.


Lets say for example we have a 3 phase 400v supply going to an induction motor. 5kw and a power factor of 0.8 and its on traywork.

would I be right in thinking the following.

5000/ (400* root3 * 0.8) = 9.02Amps per phase. 16.63A total ?????

table 4D4A BS7671 reference method E says 1.5mm 19Amps.

Sorry for this question but is the 19Amps the total the cable can carry overall or the total per phase?

How do I select the correct cable and 3 pole mcb from here?

I know there are other factor that come into play but can somebody please take me through the basic steps first so I can see how we get from start to finish then I would be happy to look at what other factor we need to consider.

Many thanks.

 

[Spoon]

Hi Old1e. Welcome to the forum.
Look at the manufactures data sheets and they usually give you some info on what size protection you want to be looking at for the motor size you are using.
For a 5kw motor you will be looking about a 32A type C mcb.

 

[telectrix]

read this:

http://www.electriciansforums.co.uk.../31498-supply-calculations-3-phase-motor.html

and this:


Eaton -