What do unbalanced resistance readings indicate?

• A. Shorted turns in one winding, open winding in one phase, or poor terminal connections.
• B. Balanced readings indicate a problem.
• C. Unbalanced readings are normal.
• D. Only one winding needs to be checked.

Answer: (A)

When a motor winding is healthy, each phase should show about the same DC resistance. That equal resistance lets the phases share current evenly and run smoothly. If the readings are unbalanced, it points to a fault in one or more windings or their connections. A shorted turn in a winding lowers that phase’s effective resistance, an open winding makes it appear much higher or infinite, and bad terminal connections add extra resistance or variability. Any of these issues causes one phase to differ from the others, which is why unbalanced readings indicate a problem.

Balanced readings, by contrast, suggest the windings are in good condition. The idea isn’t that unbalanced readings are normal; you should check multiple windings and compare them to confirm a fault rather than assuming one reading is fine in isolation.