When one phase is at zero, what is happening in the circuit?

When one phase is at zero, what is happening in the circuit?

• A. The circuit stops
• B. The other two are providing power to the circuit
• C. The system automatically rebalances
• D. The phasing meter triggers alarm

Answer: (B)

In a three-phase system, the three phase voltages are 120 degrees apart, and the instantaneous voltages always sum to zero. If one phase is momentarily at zero volts, the other two phases are equal in magnitude but opposite in sign at that instant, so the line-to-line voltages remain nonzero and the load still gets power. The circuit doesn’t stop; the remaining two phases are delivering energy to the load, though the supply becomes unbalanced for that moment. This is a transient situation often described as single-phasing, not a complete shutdown or automatic rebalancing.

In a three-phase system, the three phase voltages are 120 degrees apart, and the instantaneous voltages always sum to zero. If one phase is momentarily at zero volts, the other two phases are equal in magnitude but opposite in sign at that instant, so the line-to-line voltages remain nonzero and the load still gets power. The circuit doesn’t stop; the remaining two phases are delivering energy to the load, though the supply becomes unbalanced for that moment. This is a transient situation often described as single-phasing, not a complete shutdown or automatic rebalancing.