Frequency Spectrum Analysis of Magnetic Field Strength for Effective Condition Monitoring of Magnetic Cores

Fault diagnosis and condition monitoring of electromagnetic devices is a normal practice to prevent unpredicted downtime and catastrophic failure. As a key objective in effective fault diagnostic, the quality assessment of magnetic cores to identify core faults or interlaminar faults (ILFs) can be addressed. ILFs in magnetic cores make direct impact on the magnetizing process, which results in anomaly and asymmetry in the magnetic fields and hence magnetizing currents. This article presents a pragmatic approach for ILF analysis and condition monitoring of magnetic cores with grain-oriented electrical steels (GOESs). The proposed technique relies on interpreting frequency spectrum of the magnetic field over one cycle of magnetization. To this end, experimental work was undertaken on stacks of four standard Epstein size laminations subjected to artificial ILFs of different severities. The impacts of each fault scenario on dynamic hysteresis loop (DHL) and instantaneous wave shapes of magnetic field strength in time and frequency domains were studied. This work found that frequency spectrum analysis of magnetic field strength could be employed as a diagnostic tool to identify ILF. This approach can effectively increase the accuracy of fault diagnosis and improve detectability of weak fault signatures.