Implementation of Instantaneous Power Spectrum Analysis for Diagnosis of Three-Phase Induction Motor Faults Under Mechanical Load Oscillations; Case Study of Mobarakeh Steel Company, Iran

Induction motors are the most commonly used prime movers in various industrial applications. Their vast amount of implementation necessitates a thorough condition monitoring framework to assure their well-being, reduction of costs, increasing their lifetimes and avoiding unwanted stoppages. Intensive research efforts have been focused on motor current signature analysis (MCSA), the technique which utilizes the spectral analysis of the stator current and aims to detect electrical and mechanical defects. Although MCSA is one of the most common and efficient techniques in condition monitoring of induction motors, several drawbacks hinder their applicability and efficiency in certain conditions; one of the most important of which is when the motor faces oscillating loads where fault-related sidebands in MCSA spectrum are misunderstood with the ones due to load oscillation and hence it leads to false indications . In this paper, a new fault detection technique focusing on active and reactive instantaneous power signatures rather than stator current is proposed for the diagnosis of faults in three-phase induction motors and prevention of false indications due to overlapping fault sideband components with those pertained to load oscillations. As a specific case study, a large 2 MW motor in steel production process in Mobarakeh Steel Company, Iran, with a relatively oscillating load is studied. A common fault in induction motors, a broken rotor bar is simulated for verification of the results. Computer simulation is performed using MATLAB based on the proposed case study and both approaches are compared in both healthy and faulty situations, highlighting the advantages of the proposed method.