An Alternative System to Characterize Permanent Magnets with Strong Magneto-Crystalline Anisotropy Without Irreversible Demagnetization

The determination of the main magnetic properties of permanent magnets usually requires sophisticated and expensive measuring systems. This work analyses and proposes a low-cost system for the characterization of Rare Earth and Ceramic permanent magnets at room temperature and with linear demagnetization curve by a methodology simpler than the standard ones. It comprehends a magnetic circuit with the permanent magnet under test, a steel yoke with appropriate pole pieces, a variable air-gap, low power magnetization and demagnetization coils, a Hall effect Gaussmeter, a fluxmeter, a coil driver electronic circuit and a virtual instrumentation system. It is presented the variable air-gap method to determine the remanent magnetic flux density and the determination of the recoil permeability with limited demagnetization current in a standard closed magnetic circuit. Considering linear demagnetization, H_c and (BH)_max are determined accordingly. Also, the results of the tests and analysis of related uncertainties are presented. Thus, it is shown that the variable air-gap hysteresis meter is an alternative characterization system for linear demagnetization permanent magnets that presents uncertainties within those defined by the standards.