A magnetorheological (MR) damper with energy harvesting ability was proposed based on electromagnetic induction (EMI) principle. The energy harvesting part was composed of a permanent magnet array and inducing coils which move vertically. This device could act as a linear power generator when the external excitation was applied, and the kinetic energy could be converted into electrical energy due to the relative linear motion between the magnets array and the inducing coils. Finite element models of both the MR damper part and the linear power generator part were built up separately to address the magnetic flux distributions, the magnetic flux densities, and the power generating efficiency using ANSYS software. The experimental tests were carried out to evaluate the damping performance and power generating efficiency. The results show that the proposed MR damper can produce approximately 750 N damping forces at the current of 0.6 A, and the energy harvesting device can generate about 1.0 V DC voltage at 0.06 m·s−1excitation.
A magnetic field sensor is designed and fabricated using a piezoelectric face shear mode Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT)/Metglas magneto-electric (ME) composite. An outstanding ME coupling coefficient up to 1600 V/(cm Oe) was experimentally achieved, being ∼50% higher than the value from the extensional PMN–PT/Metglas ME composite with the same volume. The detection limit was found to be 2 × 10−6 Oe for the DC magnetic field, while it was 2 × 10−8 Oe for the AC magnetic field. The sensitivity of the face shear mode PMN–PT/Metglas ME composite is about one order of magnitude higher than that of a 32 extensional mode PMN–PT/Metglas based ME composite in sensing a weak DC magnetic field. A sensing array was also designed based on the ME composite to image weak DC magnetic fields, demonstrating a great potential promising for sensing weak magnetic fields.
A magnetic field sensor based on the ∆E effect (the change of elastic modulus of the MS phase under external magnetic field) was designed and fabricated using 36-face shear mode piezoelectric (PE)/magnetostriction (MS) composite. This device was proposed to sense a magnetic field by monitoring the change of the device electrical impedance in magnetic fields. The electrical impedance changes due to ∆E effect and the electromechanical coupling factor of the composite were experimentally and theoretical explored. The dynamic range for the 36-face shear mode composite is found to be ~400% larger than a 31/32 extensional mode composite. Of particular importance is that the proposed magnetoelectric (ME) sensor based the ∆E effect is able to sense a weak magnetic field without bulky AC/DC excitation coils, which are usually used in the traditional ME sensor based on magneto-mechano-electric coupling effect. A two-dimensional (2D) magnet target imaging array was designed based on the PE/MS magnetic field sensor to image a target magnet located at different distances and with different orientations at room temperature. This design provides a good paradigm for 2D magnetic field sensing and imaging with a simple PE/MS composite sensor structure.
It is very important to study the overvoltage protection and insulation coordination of the converter stations for the ±800kV UHVDC transmission project because of its importance in the power grid. The paper studies two kinds of arrester arrangements of the converter stations in the Nuozhadu to Guangdong ±800kV UHVDC power transmission project by using the PSCAD/EMTDC program. The simulation results show that the protective level of arresters is different, while the insulation levels of critical equipments in the converter station are almost the same under these two arrester arrangement schemes.
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