1. The air gap between stator and rotor exceeds the specified value.

　　2. Axial displacement of motor rotor; Refers to the contraction of one end of the rotor into the stator core, which increases the magnetoresistance encountered at the end of the magnetic flux, leading to excessive no-load current.

　　3. Bearing ball wear and shaft bending cause stator and rotor phase friction. At this point, although the motor is empty, as with the load, so that the no-load current too large.

　　4. The number of turns per phase winding is insufficient.