Marcel Janda

Detection of eccentricity and bearings fault using stray flux monitoring

The article describes the possibilities of employment of external magnetic field for detection of rotor eccentricity and for bearing fault diagnosis. Proposed method uses the magnetic flux density in proximity of induction motor as a diagnostic signal and it reaches the relatively high sensitivity in case of rotating air gap asymmetry represented by dynamic eccentricity. Since the bearing fault is the most frequent type of failure, the feasibility of applying this method is investigated. The results of experimental tests are introduced, including the motors with dynamic eccentricity and with artificially damaged bearing on the inner race. Both the stray flux and stator current are measured and compared in frequency domain.

Effects of eccentricity on external magnetic field of induction machine

This paper deals with the analysis of external magnetic field of three-phase induction motor in order to diagnose the air gap asymmetry caused by eccentric rotor. Dynamic eccentricity produces low frequency air gap flux components, however they can be observed in stator current only under mixed eccentricity. Unlike MCSA (motor current signature analysis), described method allows to detect purely dynamic eccentricity or to detect dynamic eccentricity under mixed eccentricity with a minimal effect of static eccentricity. Although many papers have been focused on external magnetic field analysis, they have usually decribed other types of faults. In this paper the amplitudes of characteristic frequency components are predicted using FEM and some obtained results are verified by measurement. Both purely dynamic and mixed eccentricities are taken into account as well as saturation of magnetic circuit due to its significant influence on calculated spectrum.

Additional asynchronous and pulsating torque analysis of 3-phase induction machine

This document contains possibilities of additional asynchronous torque development due to the high harmonics and their general derivation. Also, there is calculated a pulsating torque of 3-phase induction machine with power 1.1kW from electromagnetic field and example of additional asynchronous torque calculation. Whole analysis is done by finite element method in ANSYS. The torque is calculated via a circular path integral of the Maxwell stress tensor. The Maxwell stress tensor provides a convenient way of computing forces acting on bodies by evaluating a surface integral.

Noise diagnostic of induction machine

The paper deals with the diagnosis of induction motors. Specifically, measurement and analysis of noise. Further examine the possible influence eccentricity of rotor on create noise in electrical machines. Given that measured machine had not cooling system, it is possible identified the two main groups of noise sources. These are the electromagnetic and mechanical sources. Furthermore, an analysis of noise in one revolution of rotor. When comparing the noise of induction motor for one revolution of rotor eccentricity and were found identical to the dominant points. They make it possible to assume that the relationship between the eccentricity of the rotor and the noise that the machine generates. From the viewpoint of electrical machinery that could mean, e is eccentricity of the engine can be diagnosed in the noise measurement. This would be a non-contact measurement, which would simplify the analysis and diagnosis of structural faults of asynchronous machines.

Calculation of the vibration induction motor using the finite element method

This paper deals with the simulation of mechanical vibration using Ansoft Maxwell programs and Ansys Workbench. The actual vibrations are among the compelling indicator of failures of electrical machines. Any mechanical failure or fault in the electric or magnetic circuit affects the individual components of the vibration. Thanks to program Maxwell is then possible to simulate electromagnetic field and distribution of radial forces within the asynchronous motor. Changes of radial forces then enters to the Ansys Workbench as a boundary condition for structural analysis. On that basis, you can watch the size, direction and frequency of the vibration of the machine. This procedure may be used for simulating the impact of any defects on the vibration spectrum. In practice it is possible to use, for example to simulate a breaking of rotor bars and the influence of their break. This method can be used for the calculation of the influence of disturbances on any number of these bars. Other common disorders are static and dynamic eccentricity. Through the use of interconnection program Ansys and Maxwell is possible to determine the course and amplitude of vibration given to size eccentricity. This information can help to monitor the development of faults in electrical machines, their identification and determination of their range.