Three-Phase Faults a Single-Phase Stabilizer Can't Fix

A single-phase stabilizer corrects the voltage it sees at its own input. On a three-phase system, that is often not where the problem is.

Phase imbalance

Phase imbalance means the three line voltages differ from each other. Equipment with three-phase motors then draws uneven current, heats up and derates. Regulating only one phase can even make the imbalance worse, because the corrected phase shifts the neutral point for the other two.

Phase loss

Phase loss is a sudden event rather than a slow drift. Motors continue to run on two phases with reduced torque and rising temperature, which is why phase-failure protection belongs in the same cabinet as the regulator.

Neutral drift on four-wire systems

Neutral drift appears on three-phase four-wire systems when single-phase loads are unevenly distributed. Phase-to-neutral voltage rises on lightly loaded phases and drops on heavily loaded ones, which is exactly the condition that damages control electronics.

What to specify

Three-phase servo and SCR stabilizers regulate each phase independently, which addresses all three conditions at once. The three-phase stabilizer range covers per-phase regulation, and the ZBW-S static series applies where no moving part is acceptable. When specifying one, state the imbalance measured at the site, not only the average voltage.