| Induction motor is widely used to national production fields. According to statistics, the probability of induction motor bearing fault in the motor fault accounted for more than 40%. Therefore, the study of induction motor bearing fault is of great significance.This paper mainly studies the magnetic field characteristic of the induction motor when the bearing fault occurs. It considers the bearing fault can impact the main magnetic flux of the magnetic field, and deduces the magnetic field characteristic frequency of the bearing fault. The magnetic field characteristic frequency expression is deduced considering a multiple modulation between torque fluctuation frequency, power supply harmonic and slot harmonic. Next, the relational expression of the bearing fault amplitude characteristics and the power’s voltage parameters is deduced. using the search coil to diagnosis the bearing fault, AC transformer proper power supply voltage reduction methods can make the fault amplitude characteristics more identificated. Finally, due to the four search coils of the motor respectively fixed at different positions of the motor stator tooth, taking advantage of this special location relationship to get a data processing method based on multiple search coils magnetic field. In spectrum analysis, this method can effectively identify the fault characteristic frequency in the spectrum and improve the amplitude of characteristic frequency.The correctness of the theory is verified by finite element analysis and real hardware experiment. The characteristics of motor magnetic field when the bearing fault occurs are studied by the motor magnetic field finite element of Ansoft Maxwell simulation. Then the detection platform of simulative bearing fault and actual bearing fault platform are built to diagnose the induction motor bearing fault. Induction motor fault information of magnetic is reflected by the acquisition of search coil induction electromotive force signals. The experimental results show that the bearing fault characteristic frequency of magnetic field signal spectrum is more abundant than stator current spectrum, and the amplitude of some characteristic frequency is more obvious. The method based on search coils to detect the induction motor bearing fault provides directive significance and application value in bearing fault diagnosis field. |
