Hi everybody,
I am looking for information on how to size-up a cable(for example: what is the cable size that I have to use for a motor with 20 kW consumption).
Thank you in advance for your information.

With best regards,
Hermanto

 

In general, the factors that must be considered are:

o Allowable voltage drop for normal operating load.

o Allowable voltage drop for future operating load as detemined by motor's Service Factor.

o Allowable voltage drop for starting condition.

o Type of starting, ie, full-voltage, reduced-voltage, part-winding, delta-wye, etc.

o Short-circuit withstand capability (fusing capacity) for an in-close fault, occuring near protective device terminals.

o Ground or earth-fault capability for far-end fault, occuring at motor terminals. For this determination ground or earth-return path impedance must be determined.

o Derating factor(s) covering installation, ie, free-air, direct-burial (dry, wet), in conduit, etc.

o Derating factor(s) covering conductor material.

o Derating factor(s) coverng cable construction, round or sector shaped, 3x1/c, 1x3/c, 3=BD-core, 4-core, overall sheath and/or shield.

o Derating factor(s) covering insulation type and voltage level.

If you need additional info, please feel free to contact me.

Regards,
Phil Corso, PE
(Boca Raton, FL)