Research On The Current Amplitude Features Of Induction Motor Bearing Faults

Induction motors are widely used in modern industrial fields, which have the excellent performance, such as low cost, easy to maintenance and high power weight ratio. When a critical motor breakdown, the machine could appear irreparable damage. Bearing fault is one of the highest probability faults for motors. The early fault diagnosis for the induction motor bearing fault has great significance.Blodt etc simulate the influence of bearing fault on load torque by using periodic unit pulse, but it is too ideal. This thesis presents the periodic rectangular pulse model, which is used to simulate the torque oscillation due to local bearing fault, and the features of periodic rectangular pulse has been researched in details. Also, the influence of bearing fault on stator current has been researched. This thesis represent that the each side frequency amplitude of eigenfrequency satisfy the function Sa envelope with fault width variation. The numerical simulation has been carried out in Matlab. Current spectrums with different fault width have been comparative analysis, which results verify the correctness of the theoretical derivation.The thesis have researched the amplitude feature of current eigenfrequency which generated by rotor slot harmonic and bearing fault. The stator current frequency expression was deduced, some new eigenfrequencies were discovered. This frequency is related to rotor rotation frequency and rotor bar number, and their amplitude is affected by fault width Ï„ and frequency order n. Squirrel cage motor with 26 and 28 bars have been built in Ansoft Maxwell, and the co-simulation with Simplorer have been implemented. The result shows that those proposed eigenfrequencies are subsistent.Bearing fault simulation test rig has been designed and established in this thesis. The experiment research has been implemented via this rig. The result shows that those aforementioned theoretical derivations are correct. It can be found that when the motor bearing appears fault, the amplitude of each order current eigenfrequency is not monotonically decreasing, but the amplitude distribution of each orders eigenfrequency satisfies the function Sa side frequency envelope with fault width variation. Considering the effect of rotor slot harmonic, the amplitude feature of new added eigenfrequency satisfies the same change regulation. This conclusion provides an effective theoretical basis for motor bearing fault recognition and fault severity determination.