Non-invasive local magnetic hysteresis characterization of a ferromagnetic laminated core

Abstract

An alternative sensing solution is described to measure local magnetic hysteresis cycles through a laminated magnetic core. Due to the reduced space gap separating two successive laminations, it is impossible to interpose the usual oversize magnetic sensors (wound coil, Halleffect sensor). In this study, the space issue has been solved by printing the needle probe method for the magnetic state monitoring and by using a micrometric Giant Magneto Resistance (GMR) for the magnetic excitation measurement. An instrumented magnetic lamination including the non-invasive monitoring solution has been built and moved successively to every lamination position of the whole laminated ferromagnetic core. A precise cartography of the hysteresis losses has been reconstructed from all these local measurements and the average values compared to the classic measurement methods obtained with a wound coil. The relative agreement between the experimental results observed opened doors to large improvement in the estimation of magnetic losses and in the design of magnetic circuits.

Internal Characterization of Magnetic Cores, Comparison to Finite Element Simulations: A Route for Dimensioning and Condition Monitoring

“…Under such a condition, a direct implementation is not possible on a ferromagnetic electrical steel lamination whose roughness is approximately tens of nanometers in the best cases. In [27], a 270-μm thick silicon substrate was used to develop a noninvasive solution. Such a high thickness is not feasible.…”

“…However, polishing treatments or fabrications process can be performed [46]. Although these methods were not tested in [27], the resulting substrate thickness can decrease to a few tens of micrometers.…”

“…Embedding any instrumentation system inside a laminated magnetic core was difficult. In [26] and [27], printed electronics have been used to perform such measurements.…”

“…In [27], we specifically focused on embedding a B ⃗ sensor (where B ⃗ is the magnetic flux density (induction field) averaged through the tested specimen cross-section). We used the printed magnetic needle probes method (PMNPM) (also described in [28]), in which the conventional needle probe [29], [30] is replaced with a printed probe.…”

“…The resulting sensor exhibits a thickness of a conductive ink layer (≈30 μm). In [27], a 270-μm thick chip composed by a giant magneto resistance (GMR) sensor [31], [32] was positioned next to the PMNPM sensor to measure the surface tangent magnetic excitation field H ⃗ locally. Local hysteresis cycles B (H ) were plotted for each lamination (all sensors were placed in positions where B ⃗ and H ⃗ are presented collinearly).…”