J. Cusido

Fault Detection in Induction Machines Using Power Spectral Density in Wavelet Decomposition

Motor-current-signature analysis has been successfully used in induction machines for fault diagnosis. The method, however, does not always achieve good results when the speed or the load torque is not constant, because this causes variations on the motor-slip and fast Fourier transform problems appear due to a nonstationary signal. This paper proposes a new method for motor fault detection, which analyzes the spectrogram based on a short-time Fourier transform and a further combination of wavelet and power-spectral-density (PSD) techniques, which consume a smaller amount of processing power. The proposed algorithms have been applied to detect broken rotor bars as well as shorted turns. Besides, a merit factor based on PSD is introduced as a novel approach for condition monitoring, and a further implementation of the algorithm is proposed. Theoretical development and experimental results are provided to support the research.

Fault Detection by Means of Hilbert–Huang Transform of the Stator Current in a PMSM With Demagnetization

This paper presents a study of the permanent magnet synchronous motor (PMSM) running under demagnetization. The simulation has been carried out by means of two dimensional (2-D) finite element analysis (FEA), and simulations results were compared with experimental results. The demagnetization fault is analyzed by means of decomposition of stator currents obtained at different speeds. The Hilbert Huang transform (HHT) is used as processing tool. This transformation represents time-dependent series in a two-dimensional (2-D) time-frequency domain by extracting instantaneous frequency components within the signal through an Empirical Mode Decomposition (EMD) process.

Motor Fault Detection Using a Rogowski Sensor Without an Integrator

This paper presents a new approach for the current acquisition system in motor fault detection applications. This paper includes the study, design, and implementation of a Rogowski-coil current sensor without the integrator circuit that is typically used. The circuit includes an autotuning block able to adjust to different motor speeds. Equalizing the amplitudes of the fundamental and fault harmonics leads to higher precision current measurements. The resulting compact sensor is used as a current probe for fault detection in induction motors through motor current signal analysis. The use of a Rogowski coil without an integrator allows a better discrimination of the fault harmonics around the third and fifth main harmonics. Finally, the adaptive conditioning circuit is tested over an induction machine drive. Results are presented, and quantitative comparisons are carried out.

Study on the Permanent Magnet Demagnetization Fault in Permanent Magnet Synchronous Machines

This article studies the permanent magnet demagnetization fault in permanent magnet synchronous machines (PMSM). The study is carried out by analyzing the harmonics obtained using the fast Fourier transform (FFT) of stator and zero sequence currents at nominal torque for the whole range of machine operation speeds. The appropriate combination of analyses on the different currents makes it possible to determine the faults for any speed range

On the short-circuiting Fault Detection in a PMSM by means of Stator Current Transformations

This paper examines winding faults as short circuit for permanent magnet synchronous motor (PMSM). The study is carried out by means of stator current harmonic analysis. dq0 current transformation is also used to diagnose the state of the machine, and Wavelet approach is proposed to extend the analysis to the transitory of the failure. Experimental results for the full range of speeds have been obtained, which demonstrate the claims of the paper.

Broken Bearings Fault Detection for a Permanent Magnet Synchronous Motor under non-constant working conditions by means of a Joint Time Frequency Analysis

This work is an approach to develop new and reliable tools in order to diagnose mechanical faults in PMSM motors under non constant working conditions. These kinds of faults (especially damaged bearings) are more present in the industry. The paper presents a theoretical overview of the different techniques for a joint time frequency analysis and an experimental study of detection and diagnosis of damaged bearings on a permanent magnet synchronous motor (PMSM). The experiments were performed with variable rotor speed in such a way that the conventional methods such as MCSA do not work well. The stator current is analysed by means of STFT and Gabor spectrogram. Both results are presented and discussed.

Broken Bearings and Eccentricity Fault Detection for a Permanent Magnet Synchronous Motor

The paper presents an experimental study of the broken bearings and eccentricity faults detection for a permanent magnet synchronous motor (PMSM). Conclusions are obtained from the analysis of the stator current harmonic spectrum. The analysis is spread to a zero component and q axis component of the stator current, for the whole range of rotor speeds

Induction Motor Fault Detection by using Wavelet decomposition on dq0 components

Early detection of interturn shorts during motor operation would eliminate consequential damage to adjacent coils and the stator core, then reducing repair costs and motor outage time. In addition to the benefits gained from early detection of turn insulation breakdown, significant advantages would accrue by locating the faulted coil within the stator winding. Fault location would not only increase the speed of the repair, but would also permit more optimal scheduling of the repair outage. Motor current signature analysis (MCSA) method is widely used as a diagnose tool for industrial applications. On the other hand, Parks transform is the most popular transformation used in vector control algorithms. By analyzing the current spectra of dqO Park components with MCSA method it is possible to improve earlier fault detection. Moreover, using wavelet transform as signal analysis method it is possible to reduce signal noise effects. Experimental results clearly corroborate the main aim of the paper

Fault detection by means of Hilbert Huang Transform of the stator current in a PMSM with demagnetization

This paper presents a novel method to diagnose demagnetization in permanent-magnet synchronous motor (PMSM). Simulations have been performed by 2-D finite-element analysis in order to determine the current spectrum and the magnetic flux distribution due to this failure. The diagnostic just based on motor current signature analysis can be confused by eccentricity failure because the harmonic content is the same. Moreover, it can only be applied under stationary conditions. In order to overcome these drawbacks, a novel method is used based upon the Hilbert-Huang transform. It represents time-dependent series in a 2-D time-frequency domain by extracting instantaneous frequency components through an empirical-mode decomposition process. This tool is applied by running the motor under nonstationary conditions of velocity. The experimental results show the reliability and feasibility of the methodology in order to diagnose the demagnetization of a PMSM.

Discrete Space Vector Modulation Applied on a PMSM Motor

The permanent magnet synchronous motors (PMSM) are extensively used in high-performance industrial applications. The electromagnetic torque in a PMSM is proportional to the angle between the stator and rotor flux linkages. Therefore, high dynamic response can be achieved by means of direct torque control (DTC). However, because the rotor flux linkage is fixed on the rotor of PMSM, high torque ripple is produced when making use of full voltage vectors in classical DTC. The paper presents an improved PMSM DTC scheme by using a simplified space vector modulation technique, which addresses the problem by introducing a higher number of predefined voltage space vectors. The voltage vectors are tabulated in more precise switch tables which also take the emf induced in the stator windings into account. While still using switch tables to maintain the simplicity of the classical DTC scheme, the torque ripple results significantly decreased. Theoretical development and simulation results from the classical and improved DTC are presented and compared to support the research. Results show that the torque, flux linkage and stator current ripple are significantly decreased with the improved DTC