Maintenance of industrial fan 'strange' phenomenon

Maintenance of industrial fan in 2018 - 'blame' phenomenon 11 - 10 as temperatures rise, the workshop temperature is very high, part of jobs has been using the electric fan, one day, got a call from workshop repair service, an industrial fan was not in the workshop. I looked to the scene, is a with the single-phase industrial fan for many years, after electrify motor does not turn, hear the hum of the slight I turn on the fan cover with a screwdriver ( A screwdriver) Try to gently touch the wind leaf, as a result, the blades still ( The 123 file, each gear) I use a lot of external force, the situation remains. With the hand when the power is cut off can turn flexibly. I disconnect the motor casing, carefully check the motor winding short circuit, open circuit, the capacitor is also normal. Since no electricity problems, that is the mechanical aspects of the problem, then why has not move after the power supply? As usual, I open the machine and found two bearings has been short of oil gap is very big, but the rotation without binding. Close to the side of the wind leaf apex motor shaft neck has wear and tear, next to an old fan after replaced the old motor axis, while change two new sets of bearings, fan is operating normally. Believe peers in the maintenance of single-phase asynchronous motor can meet the above fault, so what is causing the failure phenomenon? Originally such fault is a typical fault of single-phase asynchronous motor. 1 fault phenomenon not electricity when the rotor of the motor can be flexible rotation, after electrify, not only can't start, rotor stator 'suck up, instead of being turned to be not moved with the hand, even with a lot of external force, the rotor did not move. 2 failure causes of the stator, the rotor caused by uneven air gap, gap where small magnetic induction intensity is strong, the air gap bigger place, magnetic induction intensity is weak, the rotor in the process of rotation, due to the uneven air gap, and uneven force, will produce vibration, uneven air gap is serious, a electric motor, the rotor was immediately big gap small magnetic field force to absorb not turning. 3 troubleshooting (1) bearing wear, gets gap uneven, replace the bearing. (2) the rotor axis wear rotor eccentricity should be replaced. (3) end cover wear or different heart replacement end cover. General unilateral bearing wear or axis wear, although uneven air gap, but not unilateral magnetic force failure. Above is my point in single-phase asynchronous motor repair experience, we hope to discuss improving. （ Source: electrician learning network)