Calibration of Sensing Coils of a Three-Dimensional Magnetic Property Tester

For electrical machines with three-dimensional (3-D) magnetic fluxes, the magnetic properties of magnetic materials under 3-D excitations should be properly determined and applied in machine design and analysis. This paper presents the construction and calibration of the H (field strength) and B (flux density) sensing coils of a 3-D magnetic property testing system, and the correction of measurement error due to the misalignment of sensing coils with excitation fields. The 3-D tester has been used to measure the magnetic properties of soft magnetic composite (SMC), a material specially developed for application of 3-D flux electrical machines. Some 3-D results have been obtained on a cubic SMC sample. The measurement errors caused by the misalignment of sensing coils and excitation fields are corrected by a rotational transformation of coordinates.