Pictured is a standard “Wye” connection. First test is the “megger” test which measures resistance to ground. Should be 800-900 Mega ohms (MΩ) resistance (our tester reads up to 500 Mega ohms)
- Connect megger to V1 and to Ground. Run test, should exceed 500MΩ
- Connect megger to V2 and to Ground. Run test, should exceed 500MΩ
- Connect megger to V3 and to Ground. Run test, should exceed 500MΩ
In theory they all share the neutral in the middle, and testing only 1 leg should be sufficient, but this isolates each leg
Next test is a resistance of the windings for each leg
- Resitance test should be between V1 → V2, V2 → V3, V1 → V3 and all values should be the same. Corrosion on terminal connections may result in different values, but should all be very close (within .5 Ω to .05 Ω)
Final test would be current draw on each leg, but would require an amperage clamp and ability to run motor continuously.
- I of V1 = I of V2 = I of V3 “should” all be equal