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This paper proposes an effective magnetizing method in which bulk material is magnetized by field cooling (FC) using a permanent magnet before pulsed-field magnetization (PFM) to improve the efficiency of magnetization. The concept of this method is to form the channel composed of the magnetic field and efficiently penetrate the magnetic flux by PFM of the bulk without heat generation. An Nd-Fe-B magnet was arranged at the growth sector boundary (GSB) or the growth sector region (GSR) on the magnetic pole, and the bulk was cooled to 30 K. After the pre-FC, a single pulsed field was applied, varying in amplitude to 3.9, 4.6, and 5.4 T. Magnetic flux density on the bulk surface was measured during the magnetization, and the trapped field distribution was scanned after PFM. The experimental results showed a decrease in the trapped field for pre-FC at GSR. It was considered that the existing flux by pre-FC blocked the flux penetration of PFM. Afterward, pre-FC using a “C”-shaped magnet was devised, and the validity was confirmed.
Date of Publication: June 2012