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A bearing is an important component in any rotating machinery especially in induction motors. Thus, timely detection and diagnosis of induction motor bearing (1MB) is crucial to prevent sudden damages. This paper proposes a method to utilize artificial neural network (ANN) by using genetic algorithm (GA) to identify 1MB fault diagnosis. In this case, GA is utilized to find the optimum weights and...
We describe a new method for detecting characteristic bearing fault signatures from accelerometer vibration data based on a probabilistic model of the fault signal generation process. It is common to assume that single-point bearing defects cause periodic disturbances in bearing vibration signals, but this assumption may not be valid in practice. Our new method is less sensitive to departures from...
Demodulation techniques extract modulating currents induced by induction motors rotor faults and directly evaluate these fault currents in time and frequency domain. Vector representation of amplitude and phase modulation is analyzed with the investigation, how both modulations change with changing parameters. It is proved that fault indicators of amplitude modulation do not change with motor changing...
This paper deals with mechanical fault monitoring in induction machines from stator current measurements. The considered faults lead to amplitude and/or phase modulations of the measured stator current. The different faults can be characterized by their time-frequency signatures via the Wigner distribution. The time-frequency representations apply to complex signals that may be obtained through the...
The thermal characteristics of de-energized AC motors are largely different from those of operating AC motors. The conventional thermal protection techniques are not capable of providing reliable thermal protection for AC motors operated with intermittent periodic duty cycles. This paper proposes a non-intrusive stator winding resistance and temperature estimation technique for soft-starter-connected...
Effects of rotor faults on stator currents in induction motors are studied in the present work. Particularly, the effects of such faults on the sidebands at fundamental and harmonics current components are analyzed. A multiple-coupled circuit model determines the variation of amplitude of these sidebands as a function of the number of broken bars, load and motor-load inertia. The results obtained...
The paper presents an iterative algorithm for direct determination of current spectra at a steady state of synchronous motors when some perturbations occur in a mechanical load torque. In such cases electromagnetic and mechanic phenomena are strongly related, what is reflected by disturbances in the angular velocity and in all motor currents. Non-linear character of equations describing such performances...
The paper introduces a monitoring and diagnostic technique for the detection of incipient stator electrical faults in Doubly Fed Induction Machine (DFIM) for wind power systems. Operating in aggressive environments, the detection of anomalies at an incipient stage is crucial to decide about the operating continuity of the machines. Discrete Wavelet Transform (DWT) is used to detect stator faults under...
This paper discusses a problem of modeling induction machines when some faults appear in a cage by using a model reduced to four equations. Starting from an advance mathematical model with full representation of a cage and considering arbitrary cage faults the steady-state equations are developed. Those equations are reduced to four equations using symmetrical components of stator and rotor quantities...
Effects of voltage unbalance on the induction motors power, torque and vibrations are analyzed in this paper. Voltage unbalance produces power oscillations at twice the supply frequency, which introduces, in turn, torque oscillations and vibrations at this frequency. The dependence of these power oscillations on the unbalance level and motor load is analyzed by simulation. The effects of voltage unbalance...
Periodically time-varying loads such as reciprocating compressors produce torque and speed variations in grid-connected induction motors that are used to drive them. In each compression cycle, the torque and speed variations manifest themselves through periodic pulsations in induction motor's complex current vectors. Based on the concept of narrowband angle modulations, this paper analyzes the complex...
A novel on-line stator core fault diagnosis method for induction motors (IM) is proposed. This approach is based on an adaptive state observer; it is derived from the IM dynamic model considering stator iron losses. In this model the iron losses are represented by an equivalent iron loss resistance (RFe). Stator core fault causes important variations on iron losses and these variations are reflected...
Nowadays Permanent Magnet Synchronous Motor (PMSM) are an attractive alternative to induction machines for a variety of applications due to their higher efficiency, power density and wide constant power speed range. In this context the condition monitoring of magnets status is receiving more and more attention since is critical for industrial applications. This paper presents a characterization of...
This paper focuses on finding possible means of identifying winding defects by looking for special features in the Fourier transform of hysteresis signature of the earth current. The effect of the magnetic characteristics of the iron material on the dynamic behaviour of the system will be taken into account. The method is based on simulations of the dynamic magnetic behaviour of the magnetic material...
Thyristor based, phase angle controlled, speed regulators are widely used for energy efficient control of single-phase induction motors. This leads to power saving but adversely affects the life of insulation in the motors due to distortions in the applied voltage and current waveforms. The accelerated insulation ageing is due to increased voltage peaks, voltage transients and increased thermal stress...
In this paper a study about the different effects of shaft eccentricities on the external electric variables of a brushless salient-pole synchronous generator for ship onboard service is presented. Static and dynamic rotor eccentricities were simulated by using a dynamic mesh-model including inductances computed by an improved MWFA-based analyses and by 3D FEM, and taking in account the damping effect...
The paper describes medium voltage electrical stations in which there is going to be implemented an automated monitoring system formed of local data acquisition, protection and control equipments mounted at the level of each cell within the electrical stations. This monitoring system is based on software packages for data acquisition, storing, data transmission and processing, monitoring and analysis...
The aim of this paper is to analyze theoretically and experimentally the stator current of a three phase induction machine and load torque signals in a hoisting winch system, in order to show how they are influenced by the wire rope faulty condition. When the wire rope is subjected to axial and torsional loads, the outer strands can separate from the core in permanent way and make the rope useless...
Eccentricity related faults in induction motors have been studied extensively over the last few decades. They can exist in the form of static or dynamic eccentricity or both, in which case it is called a mixed eccentricity fault. These faults cause bearing damage, excessive vibration and noise, unbalanced magnetic pull (IMP) and under extreme conditions stator-rotor rub which may seriously damage...
The paper presents an application of a rotor broken bars detection method in induction motor drives with Field Oriented Control (FOC). Rotor fault distorts the magnetic symmetry and subsequently deteriorates the steady-state and dynamic performance. As fast speed control loop compensates for the unevenly distribution of the field, the inverter supply voltage is adjusted accordingly. The modulated...
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