The Pulsed Field Magnetometer - a tool for characterizing Permanent Magnets.
R. Gössinger*), M. Küpferling*), A. Wimmer*), M. Taraba*), W. Scholz*),
J. Dudding**), P. Lethuillier***), B. Enzberg-Mahlke****),
W. Fernengel*****), G. Reyne******)
Proceedings of the Sixteenth International Workshop on Rare-Earth Magnets and Their Applications, Ed. H. Kaneko, M. Homma, M. Okada, The Japan Institute of Metals, 2000, pp. 1129-1138.
A large bore pulsed field hysteresograph working at room temperature is
described. The system shall be used for a fast quality control of
industrial permanent magnets. It consists of a pulse magnet which is
driven by a 24 mF condenser battery (U = 2500 V) with a bore of 70 mm
inner diameter and a maximum field of 10T. Hirst constructed a second
system working with a smaller battery but also with two different pulse
durations. The Hirst system can be charged up to 3 kV - the whole
charging and measuring cycles is surveyed by a PC. Applying two
different pulse duration can be used to make eddy current corrections
for the true shape of the loop. The magnetization is calibrated with
pure Fe and Ni within 1%. For the field calibration a hall probe can be
used as well as a critical field of a sample. The effect of eddy
currents is careful studied measuring the ``eddy current -
magnetization'' in spheres and cylinders of Al and Cu. The magnetization
scales linear with dH/dt - the slope is proportional to the resistivity.
The experimental results are compared with analytical, as well as finite
element calculations. The hysteresis of technical permanent magnets
(barium ferrite, Nd-Fe-B) as obtained in a static magnetometer is
compared with that measured in the pulsed field system. The loop agrees
for barium ferrite within 1%. The loop is measured with different types
of pick-up systems (axial N/N (TU PFM) but also coaxial (Hirst PFM) with
extended homogeneity).
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Feb. 13, 2001