Cable size 30 kw motor star delta?

Cable size 30 kw motor star delta?



(I took the lowest power factors / efficiency u should expect at rated power. (75/75)

and adjusted the frequency efficiency to 75%, compared to 60hz

I would install #1 copper conductors with a #3 ground

30000watts/380volts/1.73constant for 3ph/.75eff/.75power factor/.75freq.adjust=108A


The phase current for a 30KW motor on 380V is about 46 Amps at full load.

Wired in star/delta, that's split over two wires per phase so 23A.

Using individual wires, 4mm sq would be the absolute minimum size, that's rated at 23A if used in an enclosed bundle.

If it was connected with two runs of 4 core steel wire armoured cable (3 phase + earth), you could use 2.5mm as the worst case conditions for that still give it a rating of 31A.

If there is any possibility of high ambient temperatures, I'd go up a size on either setup.

The ultimate deciding factor is that the cable must have a higher rating than the fuses and/or overload needed by the motor, so the fuse breaks before the cable overheats in case of a fault.

The typical 'rule of thumb' calculation for three phase 415V motors is to rate the cable at 2A per kilowatt, so that would give 60A per phase or 30A per cable core in s/d.


30wk is the rated output.

what is drawn to produce the RATED OUTPUT is the actual power consumed

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