A ring-type electric current sensor operated in vortex magnetic field detection mode is developed based on a ring-shaped magnetoelectric laminate of an axially polarized Pb͑Zr, Ti͒O 3 ͑PZT͒ piezoelectric ceramic ring bonded between two circumferentially magnetized epoxy-bonded Tb 0.3 Dy 0.7 Fe 1.92 ͑Terfenol-D͒ short-fiber/NdFeB magnet magnetostrictive composite rings. The electric current sensitivity of the sensor was evaluated, both theoretically and experimentally. The sensor showed a high nonresonance sensitivity of ϳ12.6 mV/ A over a flat frequency range of 1 Hz-30 kHz and a large resonance sensitivity of 92.2 mV/A at the fundamental shape resonance of 67 kHz, besides an excellent linear relationship between the input electric current and the output magnetoelectrically induced voltage. The power-free, bias-free, high-sensitive, and wide-bandwidth natures of the sensor make it great potential for real-time condition monitoring of engineering systems having electric current-carrying cables or conductors. © 2010 American Institute of Physics. ͓doi:10.1063/1.3360349͔ Conventional electric current sensors, which are operated on the basis of detection of electric current-induced magnetic fields, are best represented by Hall and reluctance devices. Hall devices need to be powered by highly stable constant-current supplies, and their inherently weak Hall voltages ͑5-40 V / Oe͒ impose great demands on signal conditioners. 1 Reluctance devices require being interfaced with highly precise integrators and real-time measurements are generally inhibited at low frequencies ͑Ͻ100 Hz͒. 2 By contrast, electric current sensors based on magnetoelectric ͑ME͒ materials do not suffer from these problems due to the intrinsic or extrinsic ME effect exhibited by the materials. 3 The ME effect is defined as an electric polarization response to an applied magnetic field. In the past decade, much research effort has been devoted to the ME materials and their ME effect. These include intrinsic ME effect in single-phase materials and extrinsic ME effect in bulk and laminated composites. 3 Because of better property tailorability and greater extrinsic ME effect arisen from the product effect of the magnetostrictive and piezoelectric effects, laminated composites based on magnetostrictive ͓e.g., Tb 0.3 Dy 0.7 Fe 1.92 ͑Terfenol-D͒ alloy͔ and piezoelectric ͓e.g., Pb͑Zr, Ti͒O 3 ͑PZT͒ ceramics, 0.7Pb͑Mg1 / 3Nb2 / 3͒O 3 -0.3PbTiO 3 ͑PMN-PT͒ single crystals, etc.͔ materials have been the main research focus. 3-11 Accordingly, various configurations in the shape of plate or disk have been studied, including longitudinally or transversely magnetized, longitudinally or transversely polarized plates, 3,6-11 radially or axially magnetized, radially or axially polarized disks, 3-5 etc. However, these plate-or disk-shaped ME laminates are only suitable for detecting magnetic fields of constant direction, indeed, they fall short of detecting vortex magnetic fields associated with current-carrying cables or conductors in reallife applications. 2 In this ...

A heterostructure possessing two concurrent operational modes: current sensing (CS) mode and current transduction (CT) mode and an enhanced current sensitivity associated with the CT mode is proposed by combining a magnetoelectric ring (MER) with a piezoelectric transformer (PET). The MER is a ring-shaped magnetoelectric laminate having an axially polarized Pb(Zr, Ti)O3 (PZT) piezoelectric ceramic ring sandwiched between two circumferentially magnetized, inter-magnetically biased Tb0.3Dy0.7Fe1.92 (Terfenol-D) short-fiber/NdFeB magnet/epoxy three-phase magnetostrictive composite rings, while the PET is a Rosen-type PZT piezoelectric ceramic transformer. The current sensitivity (SI) and magnetoelectric voltage coefficient (αV) of the heterostructure in the two operational modes are evaluated theoretically and experimentally. The CS mode provides a large SI of ∼10 mV/A over a flat frequency range of 10 Hz−40 kHz with a high resonance SI of 157 mV/A at 62 kHz. The CT mode gives a 6.4-times enhancement in resonance SI, reaching 1000 mV/A at 62 kHz, as a result of the amplified vortex magnetoelectric effect caused by the vortex magnetoelectric effect in the MER, the matching of the resonance frequencies between the MER and the PET, and the resonance voltage step-up effect in the PET.

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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 heterostructure in which an axially polarized PZT piezoelectric ceramic ring is bonded between two circumferentially magnetized, intermagnetically biased Terfenol-D short-fiber/NdFeB magnet/epoxy three-phase magnetostrictive 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 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 ~0.3 V/A and ~0.2 mA/V in a broad non-resonance frequency range up to 80 kHz as well as enhanced conversion factors of ~7 and ~25 times at the resonance frequency of 122 kHz, respectively.