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In this paper, in order to make a clear principal cause in increasing iron loss of amorphous wound cores in processing, effects of bending stress on magnetic characteristics of a Fe-based amorphous wound core are clarified. The amorphous magnetic materials have been widely used as a core material of power transformers to reduce iron loss due to their excellent soft magnetic characteristics. However, the amorphous magnetic material has an issue that the building factor (B.F.) is very large in comparison with that of grain-oriented electrical steel sheets. The amorphous transformers usually use a wound core formed by stacking plural amorphous sheets in different lengths. Bending stress is, therefore, generated at each corner of the wound core in processing. Due to this bending stress, the magnetic characteristics of the wound core deteriorate. The deterioration of magnetic characteristics of the wound amorphous core is so large because of the large magnetostriction constant. As a result, the B.F. of this material becomes larger. In order to remove the residual stress, which is generated in the wound core including the bending stress, the amorphous wound core is usually annealed in a magnetic field, which is called “a magnetic annealing.” In this paper, the effect of the magnetic annealing on the magnetic properties is studied experimentally by evaluating some wound amorphous model cores. As a result, a suitable magnetic annealing condition is clarified and the iron loss of the wound amorphous model core is reduced by 65.7%. [ABSTRACT FROM AUTHOR]

We report theoretically and experimentally a passive bidirectional current–voltage ( $I$ – $V$ ) converter, capable of converting input currents into output voltages, and conversely, input voltages into output currents, based on a multiphase heterostructured magnetoelectric (ME) ring. The ME ring has a coil-wound, intermagnetically biased magnetostrictive–piezoelectric (MS–PE) heterostructure, in which an axially polarized PZT PE ceramic ring is bonded between two circumferentially magnetized, intermagnetically biased Terfenol-D short-fiber/NdFeB magnet/epoxy three-phase MS composite rings. In $I$ – $V$ conversion, a current applied to the coil induces a vortex magnetic field to the ME ring, resulting in an open-circuit voltage from the ME ring because of the direct ME effect. In voltage–current ( $V$ – $I$ ) conversion, a voltage applied to the ME ring produces a circumferential magnetic induction due to the converse ME effect, leading to a short-circuit current from the coil. The converter exhibits simultaneously large $I$ – $V$ and $V$ – $I$ conversion factors of $\sim 0.3$ V/A and $\sim 0.2$ mA/V in a broad non-resonance frequency range up to 80 kHz as well as enhanced conversion factors of $\sim 7$ and $\sim 25$ times at the resonance frequency of 122 kHz, respectively. [ABSTRACT FROM PUBLISHER]