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In this paper the issues of bearings' condition monitoring of induction motors having a squirrel-cage rotor is considered. Experimental results and their analysis are presented. The works were during the test of induction motor at rated nominal mode, with bearings: healthy and alternatively with two faults, which had defects inner and outer part of bearing frame.
Low frequency torque oscillations in the load can induce frequency components in the vicinity of that of rotor faults resulting in false alarms when applying motor current signature analysis (MCSA). False rotor fault indications due to load oscillations are most common in applications that employ speed reduction couplings for high torque, low speed operation. Recently, ideas for separating rotor faults...
Fault diagnosis of electric motors is still a challenging task for researchers. Various rotor cage faults detection techniques for electric motors have been proposed during the last two decades. One of these techniques widely used is the one based on the stator current spectral analysis which is still an open topic of research. This paper focusses on this technique; which has proven to be simple and...
We present in this paper an overview of the slot harmonic frequency detection applied to the broken rotor bars faults diagnosis This technique uses the behavior of the current spectral analysis and the estimation of the rotor slot harmonic to detect broken rotor bars in three phase induction machine. Experimental tests performed with broken rotor bars show the effectiveness and merits of the proposed...
This paper presents an application based on higher order spectra (HOS) for fault pattern extraction of induction motors. The focus was put on one of major HOS measures, the bispectrum in particular. The bispectrum is the third-order frequency domain measure, which contains information that conventional spectral analysis techniques cannot provide. A series of experiments for fault diagnosis of induction...
The progressive cracking in the squirrel cage rotor bars of induction motors can lead to irreversible damage. For this reason, an early analysis of this type of faults is very necessary. Amongst the existing analysis methods, the Power Spectral Density (PSD) estimation by Periodogram, is considered as a very popular technique and is widely used in industry. However, this technique presents some drawbacks...
This paper uses linear power spectral analysis to quantify servo-flap helicopter vibratory data measured from multiple locations of the rotor blade system and the fuselage. Vibration is the most important performance index in helicopter design and this paper compares helicopter vibrations during hover and high-speed cruising flights. In particular, we compared vibratory data measured from three locations...
In the article a theoretical basis of induction motor diagnostic methods based on motor current and motor power consumption spectra analysis is presented. Equations, describing current and power curves of motor working with most frequently caused damage types, were shown. A comparison of informative values of these signals has showed that power consumption signal contains greater number of diagnostic...
The fault detection in an induction motor (IM) operated by a variable speed drive (VSD) is an actual industrial need as most of the line-fed machines are replaced by a VSD, due to their improved speed regulation and fast dynamic response. However, undesired harmonics are always present when the IM is fed through a VSD. Under this operating condition, most developed techniques are unable to detect...
The sensitivity to Power Quality (PQ) disturbances is today increasing in micro grids due to the great economic consequences that PQ disturbances can generate. However, micro grids include several distributed energy resources (DER) interconnected to the grid with static converters that can deteriorate the Power Quality levels. Among DER, wind turbine systems (WTSs) are expected to be widely employed...
Spectral analysis of stator current allows us to study and identify the saturation harmonics for the case of a healthy motor and a motor with an eccentricity fault This paper describes the influence of magnetic saturation on the diagnosis of mixed eccentricity fault in squirrel induction motors by a modeling and a simulating work. The effect of eccentricity and saturation are included in the calculation...
This paper introduces a new approach of the stator current spectral analysis, based on chirp-Z transform (CZT) and Zoom Multiple signal classification (ZMUSIC), for diagnosing the occurrence of bearing faults in three-phase induction motor. In contrast with traditional FFT, CZT and ZMUSIC are suitable when it is necessary to analyze a not stationary signal such as the current signal of the induction...
To improve the accuracy of mechanical fault diagnosis, all-phase FFT (apFFT) is introduced to estimate individual harmonics' frequency, amplitude and phase of fault signal. Combining with synthesized FFT/apFFT correcting method of phase difference, the frequency and amplitude estimation can be obtained by utilizing these two spectral analysis results at the position of peak spectral line. Moreover,...
Sensorless control techniques of ac machines based on fundamental wave methods have a critical point of operation at zero frequency. Using signal injection methods zero frequency operation is possible, however another critical point of operation may exist at overlap frequencies which, so far has not been addressed by research. The resulting signals from injection based sensorless control methods are...
It is well known that stator winding faults such the inter-turn short circuit are the most frequent source of breakdowns in induction motors. Early detection of any small inter-turn short circuit during motor operation would eliminate some subsequent damage to adjacent coils and stator core, reducing then the repair cost. To achieve this purpose, the present paper proposes a new method, called Park-Hilbert...
This paper deals with monitoring condition of electrical failures in variable speed of permanent magnet synchronous motor (PMSM) drives by stator current signature analysis. The objective of this study is to develop a detection method for the open phase fault in PMSM drives. The main idea consists in minimizing the number of sensors allowing the open stator phase fault of the system to study. The...
The aim of this paper is to develop a technique for detecting a real rotor inter-turn short-circuit fault in a wound rotor induction machine working as generator by using the spectral and the bispectral analysis. The stator currents provide interesting signatures since the rotor inter-turn short-circuit fault introduces new harmonics in the stator windings. Hence, in this paper, it is proved that...
It is well known that slotting harmonics exist in most of the electrical machines. These harmonics may supply valuable information for condition monitoring of bearings, windings or rotor bars. Utilization of these harmonics for rotor speed and position estimation is limited mainly due to long sampling periods required by spectral estimation techniques. In this study, a novel speed and position estimation...
The introduction of Voltage Source Inverter fed motors has produced significant changes in the field of diagnostics being necessary further research to overcome various challenges. To enhance the diagnosis of motor faults it is advisable to consider as many fault signatures as possible, so, in this paper it is analyzed the detection of broken bars using the spectra around harmonics introduced by the...
Bearing lubrication is very important to ensure a satisfactory and long operation of bearings. An excess of lubrication can be as damaging as a lack of lubrication. An excess of oil or grease has damaging effects in the short term such as difficult heat evacuation, sliding balls and greater current consumption. There are some procedures, such as acoustic monitoring and methods based in charts provided...
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