Low-Frequency Magnetic Fields in Diagnostics of Low-Speed Electrical and Mechanical Systems

The magnetic field created by technical devices is a source of information. This information could be used in contactless diagnostics and predictive maintenance or for resolving problems along with standard NDT (nondestructive testing) methods, especially if we consider large, slow-speed devices, such as electromotors, transmissions, generators. Identification causalities device failure processes near one the suitable methods improving sustainability systems. measurements presented article were performed VEMA 04 fluxgate vector magnetometer DC-250 Hz bandwidth 2 nT sensitivity. Postprocessing results was means discrete Fourier Transform, spectrogram creation Wavelet Transform. presents data gathered during measurement pair extraction fans power 140 kW each maximum revolutions up to 740 rev/min controlled frequency converters single semi-Kaplan water plant 400 peak at 1005 generator speed. before after repairs ventilators ventilation system 60% 100% maximal output power. rotating fields fan electromotor stator, rotor revolutions, slip ball-bearing frequencies identified spectrums distance 700 mm from axis both cases. During on turbine, changes states mechanical electrical components machine monitored increase range 0–95%, phasing grid. Standard processing Discrete spectrograms Transform used. In measured fields, 1st–4th harmonics turbine shaft, shaft also their side identified. Significant time area 60–95% With help Wavelet, transform intervals where it desirable operate turbine. analyses compared vibro-diagnostic principles.