Abstract
The asymmetry in the manufacturing and assembling is the common issue of rotor systems. Different degrees of errors are inevitable in alternating current (AC) motors, which causes degraded performances. Furthermore, around 80 % of mechanical faults link to rotor eccentricity. The eccentricity faults (EFs) generate excessive mechanical stress and then lead to fatigue in the other parts of the motor. Motor current signal analysis (MCSA) can be used to diagnose induction machine (IM) faults. As the EF leads to an unequal air gap when the rotor rotates, the inductance of IM also responds to the EF. Moreover, the dynamic load is a typical situation due to residual dynamic unbalance and misalignment. To study how EFs and dynamic load affect the stator current. The current model of symmetrical motor, asymmetrical motors with three-level EFs and with dynamic load are investigated numerically. The correctness of models is verified through experimental study. The results show the level of EF affects the sideband peak values significantly in the stator current spectrum. These findings will provide a foundation for the accurate diagnosis of motor health conditions.
Highlights
Eccentricity faults (EFs) refer to the air-gap space between stator and rotor that varies when the induction machine (IM) is working [1]. 80 % of mechanical faults result in rotor eccentricity [2]
When the motor is with eccentricity, the sidebands of the dynamic load cases in the spectrum a related to the original angle
This study develops alternating current (AC) motor models with eccentric effects
Summary
Eccentricity faults (EFs) refer to the air-gap space between stator and rotor that varies when the induction machine (IM) is working [1]. 80 % of mechanical faults result in rotor eccentricity [2]. Eccentricity faults (EFs) refer to the air-gap space between stator and rotor that varies when the induction machine (IM) is working [1]. 80 % of mechanical faults result in rotor eccentricity [2]. A NUMERICAL STUDY OF ROTOR ECCENTRICITY AND DYNAMIC LOAD IN INDUCTION MACHINES FOR MOTOR CURRENT ANALYSIS BASED DIAGNOSTICS. Dynamic load faults come from external faults instead of from an IM It is mainly caused by gearbox transmission failure, load imbalance and misalignment [11]. If the load torque oscillates as the IM working, the current will be modulated with spectral components related to abnormal load faults [13]. Any torque oscillation at a multiple of the rotational speed will produce stator currents at eccentricity frequency (Eq (1) (2)) [14].
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