Cable Sizing?

Question

I need detailed steps on how to go about sizing a cable for two purposes. 1, Size cable for e.g flourescent tube say 36W. 2, A 5.5KW induction motor with power factor 0.8, 3 phase at 415 L-L.

Can someone show me in details (including detailed formulas) how i can go about this.

Many thanks

Answer 1

Dear pa,

Thank you, am also fine like you,dear simply find the current

in the circuit. For your case

1. 36w yeah you are not mention the operating voltage of flourescent tube ok any way if it is a 230v means,

    W=VI, here I=36\230,

2. 5.5kw=5500w

    So simply find the current. Then select suitable thickness of cable with good quality

Note : For best, use double the size of counductor thickness

Answer 2

For lights there is a standard here of 1.5 mm^2 this could be different in different areas.

5.5kW on 400 V you can use 4mm^2 to be safe but you can try 2.5mm^2.

Normally the cables are rated for current carrying capacity. So you check the maximum current of the motor and double it for starting up.

Answer 3

Hi Vince,

It all depends on how deep you want to go into this.  IEE has a whole bunch of tables that'll show you the current carrying capacity and voltage drop of a specific cable but installation method/location/proximity to other cables etc all have a beraing on the issue.

Take a look at this for example: http://www2.theiet.org/Publish/WireRegs/...

Regards,

Tony