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

Abstract

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, Hc 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.