In a three-phase system with perfectly balanced loads, what is the neutral current?

• A. Equal to the line current
• B. Maximum
• C. Zero
• D. Variable

Answer: (C)

In a three-phase system with perfectly balanced loads, the neutral current is zero. This is a fundamental principle of balanced three-phase systems.

When loads are perfectly balanced, each phase carries the same current magnitude and the phase currents are 120 degrees apart in time. The vector sum of the currents in a balanced three-phase system leads to cancellation in the neutral conductor. Mathematically, this can be illustrated by summing the three phase currents (IA, IB, IC), which leads to a total of zero:

IA + IB + IC = 0.

As a result, the neutral wire, which serves as the return path for unbalanced current, does not carry any current when the loads are balanced. Therefore, in ideal conditions where loads are equally distributed, the neutral current remains at zero.