Why Neutral Cable Size Is Half Of Phase Cable?
The neutral conductor is half the size of the phase conductor because it only transfers the unbalanced current between phase A and phase B.
The neutral wire is connected to the ground, as is the center tap of the secondary (output) winding of the transformer at the pole (directly in the middle of the secondary coil), creating a 0V ground reference point that divides the voltage between the two branches (120V).
For this reason, it is permissible to be smaller.
The cross-section of the neutral conductor can be smaller than the cross-section of the phase conductor if the cross section of the phase conductor is larger than 16 mm2 for copper cables or 25 mm2 for aluminum cables. Cable if both of the following conditions are met:
- The neutral conductor is protected by a device that, in the event of a short circuit between a live conductor and earth, automatically disconnects all conductors of the circuit, including the neutral conductor.
- The maximum voltage to the ground must not exceed 50 V for single-phase circuits and 30 V for three-phase circuits.