فهرست مطالب mansour ojaghi

Many investigations have been conducted to detect single incipient faults in squirrel cage induction motors. However, there is much less research on detecting and discriminating simultaneous faults within the induction motor. The simultaneous presence of eccentricity fault with some other faults is unavoidable due to some manufacturing imperfections or the possible misalignment of the motor-load shafts. Neglecting the intrinsic eccentricity and simultaneous faults might cause mistakes in the condition motoring of the motor. This article presents an analytical and experimental approach to detecting the simultaneous mix of eccentricity and broken rotor bar faults. Theoretical analyses represented how the indicators appear in the stator current due to mechanical faults according to dynamic equations, MWFA, and Fourier series. Thus, a new frequency indicator was introduced to identify simultaneous faults. The suggestive index is monitored in the modified winding function (MWFA), and finite element (FE) simulations and its amplitude was studied in motors with healthy conditions and separate and simultaneous faults. Simulation and experimental results confirmed the capability of the proposed index to distinguish simultaneous faults from other cases. This method is non-invasive, low-cost, load-independent, and can be implemented in the monitoring system of any motor.

Due to the widespread usage of three-phase induction motors in various industries, including power plants, refineries, petrochemicals, mining, transportation, shipping, etc., requirements for monitoring their conditions to detect various incipient defects are increasingly growing. It is necessary to detect the induction motor faults, which may cause the motor to stop unintentionally, in the shortest time with the highest accuracy in order to eliminate the problem with prior planning before spreading it. Some effective indices for detecting different types of the rolling-element bearing localized faults are derived from the motor vibration signal. In this paper, the mentioned indices are measured and analyzed in different scenarios to evaluate their reliability using laboratory test results. The results show that the influence of the motor temperature in the range from 30 to 75oC on the magnitudes of the indices is between 1 to 3 dbs; considering the magnitudes of the indices, such influence is rather negligible. Similarly, increasing the motor load from no-load up to full-load can influence the magnitude of the best selected indices by up to 2 dbs. In addition, increasing the localized defect severity (the hole diameter) from 2 to 5 mm usually affects the indices magnitudes by an oscillating manner with a maximum oscillation amplitude of 20 dbs.