Applicazione della Tecnica di Analisi Tempo-Frequenza a un Motore Sincrono a Magneti Permanenti Soggetto a Disallineamento

Over the past few years, there has been a steadily increasing interest in permanent magnet synchronous motors (PMSM) compared to other machines, as they offer a higher efficiency, high output power-to-volume ratio, and high torque-to-current ratio. For that reason, condition monitoring and diagnostic features are essential to improve the reliability of these drives, which could show information on wear, malfunctions, and incipient stages of degradation. In this thesis, a diagnosis technique applied to a PMSM that is operating in time-varying conditions is proposed. Specifically, the tests are intended to assess the condition of the PMSM during the startup transient phase, as well as in its steady-state mode, under both no-load and loaded conditions, at various supply frequencies of 90 Hz, 120 Hz, 150 Hz and 180 Hz. The experiment is executed, firstly, with the healthy motor, then, with the same motor with misalignment (static eccentricity), and the parameters that are measured and analyzed are the stator current, radial stray flux, vibrations, and torque, to which the Short Time Fourier Transform (STFT) signal processing method is applied, a time-frequency domain analysis method. In the first chapter, the focus is on explaining and identifying the types of faults that can occur in the PMSM, electrical and mechanical, providing some examples from various research papers. The state of the art of the PMSM is described in the second chapter. Additionally, a brief examination of the behaviour of a PMSM with and without static eccentricity is conducted through a two-dimensional finite element analysis (FEA) utilizing Simcenter MAGNET software. In the third chapter, signal processing techniques used for electrical machine diagnosis are presented, explaining their characteristics, differences, and limitations. The fourth chapter explains the setup and the equipment used in the test, which includes an electrical drive accompanied by various measurement instruments utilized to measure and analyse the parameters of interest. In the final chapter, the data obtained from the acquisitions is analyzed, with a focus on identifying the fault-related harmonics, explaining the reasons behind the existence of certain harmonics, and providing insights into how these harmonics change in relation to frequency and load.