Name two common diagnostic tests for motor windings besides insulation resistance.

• A. Winding resistance measurement and polarity check
• B. Vibration analysis and infrared thermography
• C. Ultrasound testing and magnetic particle inspection
• D. Hydrostatic test and leak check

Answer: (D)

When diagnosing motor windings, you assess electrical condition beyond insulation resistance by checking continuity and how the windings are connected. The first key test is winding resistance measurement. By measuring each winding’s resistance and comparing it to the expected per‑ winding value, you can detect open circuits, shorted turns, loose connections, or damaged windings. This test is direct, quick, and reveals issues that can cause abnormal current, overheating, or reduced performance.

The second essential test is polarity or phase relation check. This verifies that the windings are connected with the correct polarity relative to each other and to the supply. Proper polarity ensures the motor develops correct torque and rotates in the intended direction. If polarity is off, you can get reverse rotation or poor starting and running performance, signaling mis-wiring or connection problems that need correcting.

Other options either focus on mechanical condition (vibration and infrared thermography), nondestructive material checks (ultrasound and magnetic particle), or fluid-related testing (hydrostatic and leak checks), which don’t directly assess the electrical integrity of windings.