Riassunto analitico
The objective of this study is to investigate the two specific failure modes of SPM electric motors. This is achieved through the use of analytical models computed with MATLAB tools and the implementation of experimental tests, following the theory called Motor Current Signature Analysis (MCSA). The study was conducted in collaboration with Kohler Engines EMEA, which is interested in testing and investigating the physics of failure and reliability of the electric motor mounted on the hybrid unit equipped with diesel engine. The study examines two main failure modes: Winding Insulation Degradation and Bearing Pitting.
The first topic, Winding Insulation Degradation, was investigated using an analytical model in conjunction with Weibull reliability analysis. An algorithm implemented in MATLAB simulates a number of failed samples and retrieves the Weibull law and B10 value.
The second topic, Bearing Pitting, was investigated at Kohler Testing facilities by measuring vibrations, phase current and phase voltage spectra at specific motor working points. An intentionally damaged bearing has been used to simulate a premature ageing. The experimental purpose is to generate Mechanical vibrations associated with variations in the physical air gap of the machine modulate the air gap flux density and generate stator currents at predictable frequencies related to the electrical supply and vibrational frequencies. Test results show that the current signature can be used to identify the presence of bearing faults, and a predictive diagnosis can be modulated according to the machine’s operational modes.
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