Leon Swędrowski

Use of Neural Networks in Diagnostics of Rolling-Element Bearing of the Induction Motor

Bearing defect is statistically the most frequent cause of an induction motor fault. The research described in the paper utilized the phenomenon of the current change in the induction motor with bearing defect. Methods based on the analysis of the supplying current are particularly useful when it is impossible to install diagnostic devices directly on the motor. The presented method of rolling-element bearing diagnostics used indirect transformation, namely Clark transformation. It determines the vector of the spatial stator current based on instantaneous current measurements of the induction motor supply phases current. The analysis of the processed measurement data used multilayered, one-directional neural networks, which are particularly attractive due to their nonlinear structure and ability to learn. During the research 40 bearings: undamaged, with damages of three types and various degrees of fault extent, were used. The conducted research proves the efficiency of neural networks for detection and recognition of faults in induction motor bearings. In case of tests of the unknown state bearings, an efficiency approach to failure detection equaled 77%.

Model and simulation tests of a squirrel - cage induction motor with oscillation of the air gap

Damage of bearings is the most common cause of failures of squirrel-cage induction motors. A faulty bearing results in additional motor vibrations. They are reflected in the harmonic content of stator currents. In certain operating conditions the current signal is the sole source of information on the state of the motor. The paper presents a mathematical model of the motor, allowing for rotor eccentricities. Calculated spectra of the stator currents are presented for the cases of operation with rotor vibrations mapping with some approximation the vibrations caused by faulty bearings. The paper presents also results of laboratory simulations for a motor put into vibrations of adjustable frequency. Vibrations of the motor housing simulate the rotor oscillations caused by a damaged bearing. The results of laboratory simulations permitted to define the relations linking vibrations of the air gap with the components in the stator current spectrum.

Measuring system for analysis of motor supplying current for diagnostic purposes

The object of the investigation presented in the paper are measurements related to diagnostics of induction motors, especially damages caused to bearings. Due to the fact that the amplitude of the network voltage basic harmonic in the current spectrum is high in comparison with components responsible for damages of bearings, there has been proposed a preliminary elimination of this component from the analog current signal. The problem with interpretation of diagnostic measurements in present systems is difference between measurement results of characteristic frequencies and theoretical calculations. In the proposed measurement system this problem was solved in such a way that the value of the angular speed and of the supply frequency is calculated on the basis of appropriate components in the very same current spectrum that is further used in the search for diagnostic components. The paper presents also the measuring system and provides results of the investigations carried out on motor encumbered with specially prepared defect.

Induction motor bearings diagnostic using MCSA and normalized tripple covariance

Diagnosis of induction motors, conducted remotely by measuring and analyzing the supply current is attractive with the lack of access to the engine. So far there is no solution, based on analysis of current, the credibility of which allow use in industry. Statistics of IM bearing failures of induction motors indicate, that they constitute more than 40% of IM damage, therefore bearing diagnosis is so important. The article provides an overview of selected methods of diagnosis of induction motor bearings, based on measurement of the supply current. The problem here is the high disturbance components level of the motor current in relation to diagnostic components. The paper presents the new approach to signal analysis solutions, based on statistical methods, which have been adapted to be used by this diagnostic system. First experimental results with use of this method are also presented, they confirm the advantages of this method.

Detection of inter-turn faults in transformer winding using the capacitor discharge method

Abstract The paper presents results of an analysis of inter-turn fault effects on the voltage and current waveforms of a capacitor discharge through transformer windings. The research was conducted in the frame of the Facility of Antiproton and Ion Research project which goal is to build a new international accelerator facility that utilizes superconducting magnets. For the sake of electrical quality assurance of the superconducting magnet circuits, a measurement and diagnostic system is currently under development at Gdansk University of Technology (GUT). Appropriate measurements and simulations of the special transformer system were performed to verify the proposed diagnostic method. In order to take into account the nonlinearity and hysteresis of the magnetic yoke, a novel mathematical model of the transformer was developed. A special test bench was constructed to emulate the inter-turn faults within transformer windings.

Investigation of inter-turn fault in transformer winding using discharge method

The paper presents the results of an analysis of the inter-turn fault effects on the voltage and current waveform of the capacitor discharge through transformer winding. The research was done within the FAIR project for which a measuring and diagnostic system for testing the condition of electrical circuits of superconducting electromagnets system is being developed. Appropriate measurements and simulations of special transformer system were made to verify the proposed diagnosis method. A mathematical model was developed considering the nonlinearity and hysteresis of the transformer magnetic core. The special test bench was made to emulate the inter-turn faults in transformer windings.