In a three-phase system, the neutral current is

Answer: A. Zero

In a three-phase system, when the loads are perfectly balanced, the neutral current is zero.

Solution

For three-phase system

V_AN=V∠0°

V_BN=V∠-120°

V_CN=V∠120°

When the loads are perfectly balanced; Z_A=Z_B=Z_C=Z

The phase-A current is I_AN=V_AN/Z_A=V/Z∠0°=I∠0

The phase-B current is I_BN=V_BN/Z_B=V/Z-120°=I∠-120°

The phase-C current is I_CN=V_CN/Z_C=V/Z∠120°=I∠120°

The neutral current I_N=I_AN+I_BN+I_CN

=I∠0+I∠-120°+I∠120°=0

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