Which observation during testing best signals a phase-to-phase short in a three-phase stator?

• A. Abnormally low interphase resistance
• B. Normal interphase resistance
• C. High insulation resistance
• D. No current in any phase

Answer: (A)

When two windings in a three-phase stator develop a short, they create a direct, low-impedance path between those two phases. That shows up during interphase resistance testing as an abnormally low resistance reading between the two phase leads. In a healthy stator, the windings are isolated from each other, so the resistance seen between any two phases is comparatively higher, reflecting only the winding resistance and leakage paths. If you see normal interphase resistance, there’s no phase-to-phase short. If insulation resistance were high, that indicates good insulation but doesn’t point to a short between windings. And if there’s no current in any phase, that would suggest an open circuit or loss of supply, not a short. So the standout sign of a phase-to-phase short during testing is an abnormally low interphase resistance.