Each synchro consists of a wound, single-phase rotor, mounted on ball bearings, in a housing that contains a three-phase, wye connected stator.

Based on practice, the reasons of large and medium-sized high voltage wound rotor three-phase asynchronous motor rotor failure were expounded, and viable approach was designed.

Analysis is made on the common-seen accidents caused by the phase-wound type asynchronous electromotor rotor coil, and given the preventions.