1. The current is unbalanced with large difference of three phases in no-load condition.
Fault reason: ① Number of turns of winding of three phases are different; ② Start and end of winding are wrong; ③ The power voltage is unbalanced; ④ The winding has certain faults like turn-to turn fault, and inversed grafting coil.
Troubleshooting: ① Rewind the stator's winding; ② Check and rewind; ③ Measure the power voltage and eliminate the unbalance; ④ Clear winding faults.
2. The pointer of ampere meter is swing when the motor under no-load and overload condition.
Fault reason: ① Conducting bar of cage type rotor is break or snap; ② Wound rotor is fault (one-phase short circuit) or the brush, short-circuiting device of collecting ring is bad connect.
Troubleshooting: ① Find the reason and reweld the bar or change the rotor; ② Check the circuit of wound rotor and repair.
3. The motor has abnormal sound.
Fault reason: ① There is friction between rotor and stator's insulation paper or slot wedge; ② The bearing is worn or the oil contents foreign materials like sand; ③ The core of rotor and stator is loose; ④ The bearing is lack of oil; ⑤ The core of stator and rotor rub each other; ⑥ Power voltage is too high or unstable; ⑦ Stator's winding is wrong.
Troubleshooting: ① Clip insulation paper or peel down the slot wedge; ② Change or clean the bearings; ③ Repair the core of stator and rotor; ④ Fill oil; ⑤ Eliminate friction; ⑥ Check and reset the power voltage; ⑦ Remove the stator’s winding fault.