Compared to single-phase motors, it’s unusual for a three-phase motor to be ... 1 million ohms); 40 to 50 megohms are indications of a slight breakdown in the wire insulation, or possible oil ...

Single-phase ac motors are as ubiquitous as they ... The main winding, of heavier wire, keeps the motor running the rest of the time. A split-phase motor uses a switching mechanism that ...