First IEC standard of DC bias suppression devices to be issued

IEC TS 60076-23,the first IEC standard on DC bias suppression devices approved by IEC/TC 14 in November 2017,is expected to be published and put into force in 2018,overcoming the lack of such IEC standards in the field.The Shanghai branch of SGCC has carried out studies and researches on DC bias effect for more than 10 years,and it has led the standard development based on its R&D and the application of DC bias suppression devices in China.

New Topologies of High Torque Density Machine Based on Magnetic Field Modulation Principle

With the increasing demand for high torque density in motors,more and more new topologies emerge.Furthermore,the magnetic field modulation principle is widely concerned and has evolved into an effective analysis method for studying the new motor topology.This paper introduces the principle of magnetic field modulation.And the research on high torque density in recent years is reviewed from the perspective of magnetic field modulation,including permanent magnet vernier machine(PMVM),flux reverse machine(FRM),flux switching machine(FSM),dual permanent magnet(DPM)machine,and DC biased machine.The principle of magnetic field modulation makes it possible to propose higher torque density topologies in the future.

Excitation-wavelength-dependent THz wave modulation via external bias electric field

A theoretical model was proposed to describe the effects of external bias electric field on terahertz(THz)generated in air plasma.The model predicted that for a plasma in a bias electric field,the amplification effect of the THz wave intensity increases with the increase of the excitation laser wavelength.We experimentally observed the relationship between the THz enhancement effect and the electric field strength at different wavelengths.Experimental results showed a good agreement with the model predictions.These results enhance our understanding of the physical mechanism by which femtosecond lasers excite air to generate THz and extend the practical applications of THz generation and modulation.

Preparation of YSZ and YBCO Filmon Polycrystalline Metallic Tape

Yttria-stabilized zirconia (YSZ) thin films with the c-axis texturing were successfully deposited onpolycrystalline metallic tape (Hastelloy-C) by a dc bias rf magnetron sputtering. X-ray measurements re-vealed that the resulting YSZ films exhibited pure c-axis texturing. YBCO films deposited by using demaguetron sputtering on Hastelloy tape with YSZ buffer layer were c-axis oriented with △ω(FWHM of apeak in the rocking curve) = 5. 9° . T_c_o of 91 K and J_c of 2. 0 × 10￣3 A/cm￣2(77 K, OT) were obtained.

DC BIAS ELECTRIC FIELD DEPENDENT PIEZOELECTRICITY FOR[001]POLED Pb(In_(1/2)Nb_(1/2))O_(3)-Pb(Mg_(1/3)Nb_(2/3))O_(3)-PbTiO_(3) CRYSTALS

The longitudinal piezoelectric response of[001]poled rhombohedral and orthorhombic Pb(In_(1/2)Nb_(1/2))O_(3)-Pb(Mg_(1/3)Nb_(2/3))O_(3)-PbTiO_(3)crystals were investigated with respect to DC bias electric field,being in the range of-2-15 kV/cm.For rhombohedral crystals with compo-sitions far away from morphotropic phase boundary(MPB),the piezoelectric response generally decreased with increasing positive DC bias field,while for crystals with MPB compositions,the piezoelectric response firstly decreased and then increased as function of DC bias.The piezo-electric response was found to decrease drastically when DC bias larger than phase transition feld.On the other hand,the piezoelectric response was slightly enhanced for all the crystals as function of negative DC bias prior to the depolarization.To explain the obtained results,the field dependent piezoelectric cofficients in domain engineered crystals were analyzed based on ther-modynamic approach.

Theoretical analysis and an improvement method of the bias effect on the linearity of RF linear power amplifiers

Based on the Gummel-Poon model of BJT, the change of the DC bias as a function of the AC input signal in RF linear power amplifiers is theoretically derived, so that the linearity of different DC bias circuits can be interpreted and compared. According to the analysis results, a quantitative adaptive DC bias circuit is proposed, which can improve the linearity and efficiency. From the simulation and test results, we draw conclusions on how to improve the design of linear power amplifier.

Transient plasma-enhanced remediation of nanoscale particulate matter in restaurant smoke emissions via electrostatic precipitation

It is now recognized that nanoscale particulate matter(PM)represents a substantial health hazard for our society,including PM from restaurant smoke.In this study,we explored the use of a transient pulsed plasma in conjunction with an applied DC bias to treat oil aerosols that closely resemble restaurant(i.e.,charbroiler)smoke emissions.For polyaromatic olefin PAO-4 and soybean oil,we found that a three-order-of-magnitude reduction in particulates(i.e.,99.9%remediation)could be achieved with this system.Here,the plasma discharge was produced in a 4-in.-diameter cylindrical reactor with a 5-10 ns high voltage(30 kV)pulse generator together with applied DC bias voltages up to 10 kV.The distribution of nanoparticle sizes was measured using a scanning mobility particle sizer(SMPS)with diameter centered around 225 nm.Here,the main mechanism of remediation occurs in a two-step process in which the oil nanoparticles are first ionized by the free electrons and free radicals in the plasma and then the charged particles are swept out to the sidewalls of the reactor by the applied DC potential.We believe this general approach opens up new degrees of freedom in the design of electrostatic oil aerosol pollution control devices.

Magnetic Properties of Nanocrystalline Powder Cores Fabricated by Mechanically Crushed Powders

Fe73. 5 Cu1 Nb3 Si15.5B7 nanocrystalline powder cores with different particle sizes ranging from 10 to 125 9m were fabricated by cold-pressing techniques. The cores exhibited increased core loss P cv and decreased initial permea- bility μi with addition of fine powders below 50 μm in size, and the content should be less than 40 mass%. It was thought to be closely related to the high coercive force H c due to the stresses generated during the crushing process and high demagnetization fields of small powders. Furthermore, modifying the alloy compositions by adding defined amount of Ni could improve the soft magnetic properties, including superior characteristics of permeability under high direct current （DC） bias field and comparable low core loss at high frequency.