A Hybrid Method for Electromagnetic Coupling in Large Spaces

A hybrid method combining finite difference time domain(FDTD)with topology network was presented to treat with electromagnetic couplings and transmissions in large spaces A generalized matrix euqation expressing the relations among wave vectors at every port of the network nodes was give Scattering characteristics and electromagnetic distributions of every node was calculated independently using FDTD A structure of irises in a waveguide was taken as numerical examples This hybrid method has more advantages than the traditional FDTD method which includes saving calculation time,saving memory spaces and being flexible in setting up FDTD grids

高压直流换流站穿墙套管的局部放电在线测量(英文)

An online partial discharge(PD) measurement performed on a high voltage direct current(HVDC) wall bushing successfully identified the presence of internal discharges.The wall bushing is a sulfur hexafluoride gas-insulated bushing,rated for 500 kV dc and terminated on a thyristor-controlled HVDC converter bridge.The measurement of PD within the HVDC station environment is particularly challenging due to the high levels of electromagnetic noise caused by thyristor switching events and external air-corona from the neighboring high-voltage equipment.An additional challenge is the""mixed"voltage stress on the bushing insulation,which has both ac and dc high-voltage components.There are also fast transients during the firing of thyristors in the HVDC conversion process that cause added stress to the insulation.As a result,the analysis and interpretation of PD data for HVDC equipment is more complex;PD pulses may occur in response to the ac,dc,or switching transient voltage stresses.In this paper,an online PD measurement strategy for noise filtering and isolation of PD sources within the bushing are discussed.The PD measurement data is plotted on a phase-resolved diagram where the line supply power cord voltage was used as a reference. The phase-resolved diagram appears to suggest that the fast transients,caused during switching,trigger some PD events.Measurements were also performed with the aid of a modern PD measurement instrument having noise separation capabilities.The findings from the online PD measurements are verified with physical evidence,found after the bushing was removed from service,suggested internal PD had occurred inside the bushing.

SIMUUTION OF ELECTROMAGNETIC TUBE BULGING BASED ON LOOSE COUPLING METHOD

A loose coupling method is used to solve the electromagnetic tube bulging. ANSYS/ EMAG is used to model the time varying electromagnetic field with the discharge current used as excitation, in order to obtain the radial and axial magnetic pressure acting on the tube, the magnetic pressure is then used as boundary conditions to model the high velocity deformation of tube with DYNAFORM, The radial magnetic pressure on the tube decreases from the center to the tube end, axial magnetic pressure is greater near the location equal to the coil height and slight in the other region. The radial displacement of deformed workpicces is distributed uniformly near the tube center and decreases from the center to the end; Deformation from the location equal to coil height to the tube end is little. This distribution is consistent with the distribution of radial pressure; Effect of the axial magnetic pressure on deformation can be ignored, The calculated results show well agreements with the experimental results.

Dynamics of electromagnetic slip coupling for hydraulic power steering application and its energy-saving characteristics

To improve high-speed road feel and enhance energetic efficiency of hydraulic power steering(HPS) system in heavy-duty vehicles, an electromagnetic slip coupling(ESC) was applied to the steering system, which regulated discharge flow of steering pump to realize variable assist characteristic as well as uniquely transfer on-demand power from engine to steering pump. The model of ESC was established and the dynamic characteristics of ESC were presented by the way of simulation and experiment. Upon the layout of the assist characteristics, output torque of ESC was derived. Based on the ESC model, the output torque characteristics of ESC were simulated under steering situation and straight driving situation, respectively. The consistency of simulated ESC output torque and the one deduced from assist characteristics verifies the correctness of the ESC dynamic model. To illustrate energy saving characteristics of ESC-HPS, energy consumption comparison of ESC-HPS and conventional HPS was carried out qualitatively and quantitatively. It follows that the energy consumption of ESC-HPS decreases by 50% compared with that of HPS.

Microwave left-handed composite material made of slim ferrite rods and metallic wires

This paper reports on experimental study of the microwave properties of a composite material consisting of ferrite and copper wires. It finds that the slim ferrite rods can modify the magnetic field distribution through their anisotropy, so that the ferrite＇s negative influence on the copper wires＇ plasma will be reduced. Left-handed properties are observed even in the specimen with close stuck ferrite rods and copper wires.

Numerical Determination of Induced Electric Eddy Fields Inside Arbitrarily Shaped Induction Coils

We propose a numerical solution of Faraday＇s law of induction based on the knowledge of the time-varying, non-uniform vector potential inside arbitrarily shaped electrical coils. The vector potential can be related to the magnetic induction which yields the well-known form of Faraday＇s law. The algorithm applies for non-retarding fields within the quasi-stationary regime. The model is intended to help to understand the behavior of electromagnetic fields inside the discharge chambers of radio-frequency ion thrusters. This provides a basis for modeling an inductively-coupled plasma which is kept burning by absorbing electromagnetic energy. In the long run, this plasma model will be used to support development processes of electric and electronic control devices which are needed for driving radio-frequency ion thrusters more efficiently. To predict the induced radio frequency fields more precisely, the skin effect along the coil wire is modeled. Furthermore, an impedance model of the coil, which incorporates the skin effect, is introduced. The simulated data are compared to measured values obtained by a generic electric field probe. Although the probe was uncalibrated, the observed values were highly similar to the expected values as determined by the numerical solution.

Electromagnetic–thermal–structural coupling analysis of the ITER edge localized mode coil with flexible supports

In a fusion reactor, the edge localized mode（ELM） coil has a mitigating effect on the ELMs of the plasma. The coil is placed close to the plasma between the vacuum vessel and the blanket to reduce its design power and improve its mitigating ability. The coil works in a high-temperature,high-nuclear-heat and high-magnetic-field environment. Due to the existence of outer superconducting coils, the coil is subjected to an alternating electromagnetic force induced by its own alternating current and the outer magnetic field. The design goal for the ELM coil is to maintain its structural integrity in the multi-physical field. Taking as an example the middle ELM coil（with flexible supports） of ITER（the International Thermonuclear Fusion Reactor）, an electromagnetic–thermal–structural coupling analysis is carried out using ANSYS. The results show that the flexible supports help the three-layer casing meet the static and fatigue design requirements. The structural design of the middle ELM coil is reasonable and feasible. The work described in this paper provides the theoretical basis and method for ELM coil design.

Observation of intracavity electromagnetically induced transparency in Cs vapor coupled with a standing-wave cavity

Cavity quantum electrodynamics （QED） is mainly re- searching the interaction process with a coherent atomic medium placed inside an optical resonant cavity, and has been of great interest in recent years. A well-known cavity- QED effect is the vacuum Rabi splitting or normal-mode splitting phenomenon that is under the strong coupling condition,

Co-Ni Electromagnetic Coupling in Hollow Mo_(2)C/NC Sphere for Enhancing Electromagnetic Wave Absorbing Performance

For enhancing the electromagnetic wave(EW)attenuation and adsorption,rational constructing and homogeneously distributing bimetallic electromagnetic coupling units in hollow structure is an effective way,but hard to achieve.Herein,a CoNi-doped hybrid zeolite imidazole framework was synthesized as precursor,which was further converted into a hollow CoNi-bimetallic doped molyb-denum carbide sphere(H-CoNi@MoC/NC)through a two-step etching and calcination strategy.At the loading amount of 15 wt%,a strong absorption of minimum reflection loss(RL_(min))of-60.05 dB at 7.2 GHz with the thickness of 3.1 mm and a wide effective ad-sorption bandwidth(EAB)of 3.52 GHz at the thickness of 2.5 mm were achieved,which was far beyond the reported MoC-based metallic hybrids.The crucial synergistic Co-Ni electromagnetic coupling effect in the composite was characterized,not only enhanc-ing the dipolar/interfacial polarization,but also promoting the impedance matching,displaying the optimized EW absorbing perfor-mance.

Thermal-annealing-regulated plasmonic enhanced fluorescence platform enables accurate detection of antigen/antibody against infectious diseases

Plasmonic enhanced fluorescence(PEF)technology is a powerful strategy to improve the sensitivity of immunofluorescence microarrays(IFMA),however,current approaches to constructing PEF platforms are either expensive/time-consuming or reliant on specialized instruments.Here,we develop a completely alternative approach relying on a two-step protocol that includes the self-assembly of gold nanoparticles(GNPs)at the water–oil interface and subsequent annealing-assisted regulation of gold nanogap.Our optimized thermal-annealing GNPs(TA-GNP)platform generates adequate hot spots,and thus produces high-density electromagnetic coupling,eventually enabling 240-fold fluorescence enhancement of probed dyes in the near-infrared region.For clinical detection of human samples,TA-GNP provides super-high sensitivity and low detection limits for both hepatitis B surface antigen and SARS-CoV-2 binding antibody,coupled with a much-improved detection dynamic range up to six orders of magnitude.With fast detection,high sensitivity,and low detection limit,TA-GNP could not only substantially improve the outcomes of IFMA-based precision medicine but also find applications in fields of proteomic research and clinical pathology.

Time-dependent development of dynamic resistance voltage of superconducting tape considering heat accumulation

In flux pumps,motors and superconducting magnets,the high temperature superconductor(HTS)coated conductor frequently carries a DC transport current when an oscillating magnetic field is present in the background.Under this circumstance,the interesting effect of dynamic resistance takes place,which can affect the operating performance of superconducting devices:heat accumulation can contribute to the rising temperature of the HTS tape and the dynamic resistance voltage can change accordingly.This article explores the time‐dependent development of the dynamic resistance voltage using a numerical modeling considering the thermal effects.After a validation against experimental results,this work investigates the effects of several factors on the structure of the HTS tape on the time‐dependent development of the dynamic resistance,thus providing insights toward a better understanding of the time‐dependent behavior of HTS tapes under external magnetic fields.

Dynamic characteristics of large permanent magnet direct‐drive generators considering electromagnetic–structural coupling effects

Dynamic characteristics of large permanent magnet direct‐drive generators(PMDGs)considering electromagnetic–structural coupling effects are analyzed in this study.Using the conformal mapping method,the scalar magnetic potential of the air gap magnetic field considering the slot effect is calculated.On the basis of the discrete current element and magnetic equivalent circuit model,the local magnetic saturation effect of the stator and rotor is quantitatively simulated and the air gap magnetic field intensity distribution is obtained via numerical simulation.A series of uniformly distributed equivalent electromagnetic springs are introduced to develop an electromagnetic–structural coupling finite element PMDG model.The proposed air gap field analysis method is verified by the finite element analysis results.On the basis of the test platform for the Goldwind 1.5MW PMDG,both modal and dynamic response tests for the stator/rotor coupling system are conducted,and the results are compared with the natural frequencies,mode shapes,and vibration responses obtained using the numerical model.The effects of the air gap length and rotor speed on the natural frequencies of the coupling system are analyzed.The proposed model has the potential to accurately evaluate the PMDG vibration energy,avoiding resonance points,and maintaining stable operations of the unit.

An optimized transmission line model of grounding electrodes under lightning currents

In this paper, an optimized transmission line model （OTL） for modeling transient behavior of grounding electrodes under lightning currents is presented. The soil ionization effect is considered in OTL, and all electromagnetic couplings between dif- ferent parts of grounding electrode are also considered by selecting the size of segment conductor properly and calculating the mutual coupling parameters between segment conductors accurately. Comparing with the traditional transmission line model, the optimized model can be used to accurately predict the effective length and transient potential rise （TPR） of grounding elec- trodes. Transient behaviors of grounding electrodes are simulated by OTL and the results are in good agreement with those of the electromagnetic model proposed by Grcev, and experiment results performed by Electricit6 de France and Geri. Further- more, non-uniform discharging phenomenon of grounding electrode under lightning current is discussed, and the effective lengths of horizontal grounding electrode under lightning currents are presented.

Multi-Band Hybrid Mobile Phone Antenna Based on Electromagnetic Coupling

This research presents a multi-band hybrid mobile phone antenna based on electromagnetic coupling,which can be applied to mobile handheld devices, occupying a small board space of 39.7 mm × 15.6 mm on the system circuit board. By adding resonant and coupled branch instead of multi-feed on the traditional bent antenna,this design provides four wide operating bands of 0.772—0.998 GHz, 1.540—1.600 GHz, 1.680—2.270 GHz and2.300—2.690 GHz with the hybrid feature of planar inverted-F antenna(PIFA), L-shape, U-shape and S-shape structures, which cover nine-band, i.e., GSM850, GSM900, GPS1575, DCS1800, PCS1900, IMT200, LTE2300,LTE2600 and Blue Tooth/Wi-Fi. Ansoft software HFSS is used in this research to make the antenna performance better and the operating principle of the proposed antenna is described in detail. Result of simulation reveals that the maximum gains of these four wide bands are 2.20,-0.99, 4.01 and 4.05 dBi, respectively. Moreover, this research also tests the return loss(S11) of the fabricated antenna with the vector network analyzer and the result is in accordance with the simulation result on the whole. There are four wide resonant frequencies which cover nine-band of wireless wide area network(WWAN), wireless local area network(WLAN) and long term evolution(LTE), when the available bandwidth is better than 6 d Bi return loss.

Near field coupling to shielded cable due to switching operation in substation

It is vital to study the electromagnetic coupling to shielded cable for improving electromagnetic antiinterference ability of secondary equipment in a substation.As a hybrid of method of moment(MoM)and transmission line method,a frequency domain model is put forward to study the near field coupling to shielded cable due to the switching operation in substation.Compared with the results of EMTP,the proposed method has been proven correct.Furthermore,this method overcomes the disadvantage of EMTP,which is only applicable for transient analysis of parallel conductors.As an example,the presented method is applied to evaluating the electromagnetic interference(EMI)to the shielded cable,whose shield is grounded at both ends,due to the switching operation in 500 kV air insulation substation(AIS).