High Frequency Induction Research Articles

A CFD simulation of the liquid-cooled pipe conductors for the high power and high frequency power electronic circuits

In recent years, depending on the developments in semiconductor technology; the performance of power electronic circuits has been increased significantly with higher power and higher switching frequency capability. However, the higher switching frequency increases both core and winding losses of the magnetic components (such as inductor and transformer) contained in the power electronics circuits. In high frequency inductors, during the rippled current flow, the winding conductors cause abnormal temperature rises due to the skin and proximity effects. This phenomenon cannot be precisely determined by mathematical methods in the design phase. In this study, the liquid cooled pipe conductors are recommended in the windings of high-frequency and high-power inductors employed in the power electronic circuits, which can be used in renewable energy systems and electric vehicles. These pipe conductors have been modeled with the Ansys-Mechanical Fluent software and the temperature values have been determined with the computational fluid dynamics (CFD) analysis. Thus, the cooling performance for the inductor winding versus the liquid circulation through the copper pipe conductor has been reported.

Improvement of the joint quality in the high-frequency induction welding of pipes by edge modification

High-frequency induction welding (HFIW) is among the most commonly used methods for producing roll formed pipes. In this paper, weld quality is evaluated through examining the weld properties, in order to obtain the effect of edge preparation on improvement of weld quality. Temperature distribution in the weld zone is studied through the groove shape of the weld joint, and the other parameters such as current, frequency, and linear speed, considered constant, are equal to 1400 A, 150 kHz, and 25 m/min respectively. The mechanical and metallurgical properties of the weld metal were evaluated by tensile test and metallography. The appropriate temperature distribution resulted from modifying the shape of the connecting edges, leading to a reduction of 27% in the mean size of the grains in the weld zone. The results also show that by increasing the temperature of welding, the heat-affected area expands and the other areas decrease. When the results of the metallography tests of the weld zone were compared, a more uniform weld width was observed in the welded specimens with modified edges. The results also showed an 18% decrease in the weld width in specimens, compared with the specimens without edge preparation.

Formability Analysis and Oxidation Layer Effects in Dieless Drawing of Stainless Steel Wires

In this study, dieless drawing experiments of stainless steel SUS304 wires of 1 mm in diameter were carried out using a self-developed dieless drawing machine. In order to prevent oxidation, argon gas was applied to a self-designed chamber during dieless drawing processes. The effects of the forming temperature and the oxide layer on the mechanical properties of the drawn SUS304 stainless wires obtained by tensile tests are discussed in this paper. A finite element model considering the high frequency induction heating mode in the finite element software DEFORM2D was developed to conduct the heat transfer analysis and the formability analysis of the drawn products in dieless drawing of stainless steel wires. The effects of the drawing speed and forming temperature on the maximal reachable area reductions are discussed. Through the comparisons of the maximal reachable area reduction between the finite element simulations and experiments, the finite element modelling for dieless drawing processes was validated.

Manufacturing of 42SiCr-Pipes for Quenching and Partitioning by Longitudinal HFI-Welding

In the pipe manufacturing and pipe processing industry, the demand for cost-effective pipes with high strength and good ductility is increasing. In the present study, the inductive longitudinal welding process was combined with a Quenching and Partitioning (Q&P) treatment to manufacture pipes with enhanced mechanical properties. The aim of the Q&P process is to establish a martensitic structure with increased retained austenite content. This allows for the beneficial use of both phases: the strength of martensite as well as the ductility of retained austenite. A 42SiCr steel, developed for Q&P processes, was joined at the longitudinal seam by a high-frequency induction (HFI) welding process and was subsequently heat-treated. The applied heat treatments included normalizing, austenitizing, quenching, and two Q&P strategies (Q&P-A/Q&P-B) with distinct quenching (Tq = 200/150 °C) and partitioning temperatures (Tp = 300/250 °C). Investigations of the microstructures revealed that Q&P tubes exhibit increased amounts of retained austenite in the martensitic matrix. Differences between the weld junction and the base material occurred, especially regarding the morphology of the martensite; the martensite found in the weld junction is finer and corresponds more to the lath-type morphology, compared to the base material in the circumference. In all zones of the welded tube circumference, retained austenite has been found in similar distributions. The mechanical testing of the individual tubes demonstrated that the Q&P treatments offer increased strength compared to all other states and significantly improved ductility compared to the quenched condition. Therefore, the approach of Q&P treatment of HFI-welded tubes represents a route for the mass production of high-strength tubular products with improved ductility.

Fabrication of Ni60+25%WC reinforced steel matrix surface composites by induction cladding

Failure of mechanical parts usually occur on the surface or start from the surface, such as wear, oxidation corrosion and fatigue. This work uses high frequency induction cladding technology to improve the overall performance of stainless steel surface. A layer of WC and stainless steel is coated on the surface of the stainless steel. The effects of different WC material contents and different induction heating current intensities on the cladding were analyzed. After the preparation of the sample, the morphology and properties of the cladding layer were analyzed by SEM, XRD and other test methods. The results show that when the content of WC is 2%-3%, the heating time is 90s and the heating current is 860A-890A. The surface of the cladding layer is most densely formed and there is no obvious over-burning phenomenon and pore generation.

Thermoelectric properties of BiSbTe/graphene nanocomposites

In this work, BiSbTe based graphene composites with different vol% of graphene were processed by the pressure assisted high frequency induction heated sintering. The exfoliated graphene was uniformly dispersed in the BiSbTe powder through magnetic stirring and ball milling. The pristine BiSbTe and composites powders were consolidated by the high frequency induction heated sintering. Thermoelectric properties of the developed bulks were investigated in the temperature range 300–500 K. The results suggest that ball milling as well as incorporation of graphene substantially changes the transport properties of nanostructured BiSbTe composites from pristine bulk. The electrical conductivity of the composites degraded somewhat gradually with the addition of graphene. The effective thermal conductivity reduces by incorporation of graphene, which is attributed to increased phonon scattering by the enormous nanostructured phase boundaries and graphene. The enhanced Seebeck coefficient accompanied by the reduction in thermal conductivity leads to improved figure of merit up to ~ 1.2 at ~ 375 K for 0.5 vol% graphene/BiSbTe composite.

Researh on the Developments of HFIC Allied Powders

The following paper presents the constructive manufacturing solution for low and medium allied powders in continuous flux, by melting in the caster, using high frequency induction currents - HFIC, wires, base material, and continuously discarding the melt over a rotating drum, cooled at a determined speed, thus by optimizing the movement and cooling parameters we can obtain the proper grain size.The functional model has the capability to achieve alloyed powders within a broad range of grain size, recommended in research. The melting furnace can be supplied with solid wires or tubular wires, with a fill coefficient of up to 0.55%, which allows the composite core to be integrated into the alloying system. Also, due to its high degree of flexibility, the equipment allows the HFIC melting crucible to be supplied with more than two wires at a time, a feature that ensures a high level of alloying of the powders to be achieved.The functional model developed in order to manufacture powders continuously was used to produce alloyed powders, insensible to elements burns when alloyed, by passing them, at welding, through the electric arc. Forwards we present physical-chemical characteristics of two powders destined to develop composite core from tubular wire alloyed with chromium and nickel.Repairing hot molds by the MIG molds made of low alloyed improvement steel requires type Fe-2.5% Cr-4.5W-V materials, with high homogeneity of the composite mixture from the making of powdered core of tubular wires.Repairing the semi-mechanized rotors made of martensitic steels from hydropower plants requires tubular (cored) wires that deposit type Fe-12% Cr-4% Ni alloys, possibly even Mo.

A Novel Method for Humidity-Dependent Through-Plane Impedance Measurement for Proton Conducting Polymer Membranes.

In this study, we introduce a through-plane electrochemical measurement cell for proton conducting polymer membranes (PEM) with the ability to vary temperature and humidity. Model Nafion and 3M membranes, as well as anisotropic composite membranes, were used to compare through plane and in plane conductivity. Electrochemical impedance spectroscopy (EIS) was applied to evaluate the proton conductivity of bare proton exchange membranes. In the Nyquist plots, all membranes showed a straight line with an angle of 60–70 degrees to the Z’-axis. Equivalent circuit modeling and linear extrapolation of the impedance data were compared to extract the membrane resistance. System and cell parameters such as high frequency inductance, contact resistance and pressure, interfacial capacitance were observed and instrumentally minimized. Material-related effects, such as swelling of the membranes and indentation of the platinum mesh electrodes were examined thoroughly to receive a reliable through-plane conductivity. The received data for model Nafion and 3M membranes were in accordance with literature values for in-plane and through-plane conductivity of membrane electrode assemblies. Anisotropic composite membranes underlined the importance of a sophisticated measurement technique that is able to separate the in-plane and through-plane effects in polymer electrolytes.

Non-Invasive Magnet Temperature Estimation of IPMSM Based on High-Frequency Inductance With a Pulsating High-Frequency Voltage Signal Injection

In this paper, a method to estimate the temperature of a permanent magnet of a traction motor for automotive applications is derived by analyzing the high-frequency inductance of an interior permanent-magnet synchronous motor. The derived method exploits the high-frequency inductance as an indicator of the magnet temperature, and it does not require a temperature sensor not only on the rotor side but also on the stator side. Hence, the method is truly noninvasive. The proposed method has been verified in a small-scale experimental setup. The performance of the method has been evaluated at various torques, speeds, and magnet temperatures ranging from -24 to 82 °C. Through testing at various operating conditions, it has been confirmed that the maximum error is less than 2.9 °C even when the speed and torque vary.

Magnet Temperature Estimation in Permanent Magnet Synchronous Machines Using the High Frequency Inductance

Permanent magnet synchronous machines (PMSMs) torque production capability depends on the permanent magnets (PMs) magnetization state, which can be affected by PMs’ temperature and by the current flowing throughout the stator windings; knowledge of the PMs’ temperature can be therefore of great importance both for control and monitoring purposes. PMs’ temperature can be measured or estimated; PM temperature measurement is not easy and is not normally implemented in commercial drives. PM temperature estimation methods can be divided into thermal models based, back electromotive force (BEMF)-based, and signal injection based methods. Existing high frequency (HF) signal injection methods estimate the PM temperature from the measured stator HF resistance. Unfortunately, the resistance is also affected by magnetoresistive effect, which can limit the accuracy of the estimates. This paper proposes the use of the stator d -axis HF inductance for PM temperature estimation. This makes temperature estimation insensitive to magnetoresistive effect. In addition, it allows the use of higher frequencies, reducing the adverse impact of the injected signal on machine performance.

Numerical Simulation of Metal Surface Layer Modification Using High-Frequency Induction Heating

Thermal processes of modifying the surface layer of a metal in a moving substrate with continuous induction heating of a rectangular substrate region by a high-frequency electromagnetic field have been studied using numerical simulation. The distribution of electromagnetic energy over the substrate surface is considered uniform, and over its volume, it is described by empirical formulas. It is assumed that, during the melting of the metal, the nanosized particles of the refractory compound inside of it are evenly distributed over the volume of the liquid metal and act as crystallization centers during its cooling. The boundary of the melting region is determined in the Stefan approximation, and the boundaries of the solid phase growth region are computed within the framework of the Kolmogorov theory of the metal crystallization. In the quasi-stationary distribution of the temperature field approximation, the size of the melting and crystallization zones was estimated and the growth kinetics of the solid phase was calculated. The characteristics of induction heating that make it possible to reduce the surface treatment time were determined. Calculated estimates of the specific power of the electromagnetic field were obtained that ensures that the melting region remains unchanged at the substrate velocity in the range of 1–3 cm/s.

Heat Transfer and Thermophysics of Subsonic Dissociated-Air Jets in Flow past a Cylindrical Model in a High-Frequency Induction Plasmatron

Heat transfer in the subsonic high-enthalpy air flow in the VGU-4 induction plasmatron is experimentally and numerically investigated for three versions of the sectional discharge channel with the exit section diameters of 30, 40, and 50 mm. The model was a flat-nosed cylinder, 20 mm in diameter. Using a Gamma code the enthalpy he and the velocity at the jet axis are numerically reconstructed from the experimental data. The method for approximately determine the enthalpy he on the basis of the experimental data and the Fay—Riddell formula for the heat flux is proposed. The effective dimensionless model radius reff is introduced, which makes it possible to take account for the dependence of the flow at the outer edge of the boundary layer on the model and discharge channel geometries and the plasmatron operation regime. The value of reff is calculated for the VGU-4 operation regimes with a simple cylindrical discharge channel and a sectional channel. The values of the enthalpy he calculated using the “exact” and approximate methods are compared: the greatest difference in the he values amounts to 6%.

High-Frequency Induction Heated Synthesis and Consolidation of Nanostructured Al-TaC Composite and Its Mechanical Properties.

The significance of Al matrix composites reinforced with metal carbide having low density and very high hardness increases in order to reduce CO₂ emissions and improve the efficiency of energy in automobile and transportation industries. Nanopowder mixture of Ta and Al₄C₃ were fabricated by high energy ball milling. Highly dense nanostructured 4Al-3TaC composite was consolidated by high-frequency induction heated sintering within one min from the mechanically activated nanopowder mixture of Ta and Al₄C₃ under the 80 MPa pressure. The microstructure, sintering behavior and mechanical properties (hardness and fracture toughness) were evaluated using FE-SEM and Vickers hardness tester.

Ceramic nanofibers versus carbon nanofibers as a reinforcement for magnesium metal matrix to improve the mechanical properties

Light composite materials based on Magnesium matrix reinforced with carbon or ceramic nanofibers were fabricated by powder metallurgy rout using high frequency induction heat sintering (HFIHS) technique. A comprehensive comparative study has been investigated on using ceramic nanofibers and carbon nanofibers as a fibers reinforced Magnesium metal matrix in order to evaluate the overall improvements in mechanical properties. Electrospinning technique followed by calcination process were used efficaciously to synthesize and fabricate the Titanium Oxide (TiO2) fibers and carbon fibers. Mg/nanofibers mixtures were prepared via powder metallurgy route using mechanical alloying technique by adding 1, 3, 5 and 10 wt% calcined nanofibers to Mg matrix. In inert atmosphere and room temperature, mixtures were initially processed using high energy ball milling for 15 + 15 min. The final bulk cylindrical samples were obtained by performing consolidation or sintering process using high frequency induction heat sintering furnace (HFIHS). Characterization of the sintered composites have been investigated using field emission scanning electron microscopes (FESEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). While, hardness test and compression test were performed in order to evaluate the mechanical properties of the fabricated composites. The obtained result shows that, the ultimate compressive strength increased to 281 MPa at 5 wt% TiO2, which represent about 12.4% more than the pure Mg. Hardness improved up to 64.4% in case of using the ceramic nanofibers as reinforcement. While using CNFs as reinforcement to the Mg matrix, slightly deteriorates the mechanical properties.

Transient Liquid Phase Bonding of Ti-6Al-4V and Mg-AZ31 Alloys Using Zn Coatings.

Ti-6Al-4V and Mg-AZ31 were bonded together using the Transient Liquid Phase Bonding Process (TLP) after coating both surfaces with zinc. The zinc coatings were applied using the screen printing process of zinc paste. Successful bonds were obtained in a vacuum furnace at 500 °C and under a uniaxial pressure of 1 MPa using high frequency induction heat sintering furnace (HFIHS). Various bonding times were selected and all gave solid joints. The bonds were successfully achieved at 5, 10, 15, 20, 25, and 30 min. The energy dispersive spectroscopy (EDS) line scan confirmed the diffusion of Zn in both sides but with more diffusion in the Mg side. Diffusion of Mg into the joint region was detected with significant amounts at bonds made for 20 min and above, which indicate that the isothermal solidification was achieved. In addition, Ti and Al from the base alloys were diffused into the joint region. Based on microstructural analysis, the joint mechanism was attributed to the formation of solidified mixture of Mg and Zn at the joint region with a presence of diffused Ti and Al. This conclusion was also supported by structural analysis of the fractured surfaces as well as the analysis across the joint region. The fractured surfaces were analyzed and it was concluded that the fractures occurred within the joint region where ductile fractures were observed. The strength of the joint was evaluated by shear test and found that the maximum shear strength achieved was 30.5 MPa for the bond made at 20 min.

In Vitro Regeneration of ICP 8863 Pigeon Pea (Cajanus cajan (L.) Millsp.) Variety using Leaf Petiole and Cotyledonary Node Explants and Assessment of their Genetic Stability by RAPD Analysis

Objectives: A reliable in vitro regeneration protocol by direct organogenesis was developed in ICP 8863 variety of pigeon pea using leaf petiole and cotyledonary node explants. Methods: For direct shoot bud induction, leaf petiole explants from seven-day-old in vitro grown seedlings and cotyledonary node explants from twelve-day-old were cultured on MS medium supplemented with various combinations and concentrations of BAP, NAA and Kinetin. Induced shoot buds of both the explants were elongated on MS medium fortified with different concentrations of BAP, NAA and GA3. The wellelongated shoots of both the explants were transferred to MS medium supplemented with various concentrations of IBA. Finally, the regenerated plants were transferred to soil and vermiculate mixture in 1:1 ratio for acclimatization. Further, molecular characterization of the in vitro regenerated plants was carried out using eight OPP and OPAZ RAPD primer series. Findings: High frequency of shoot bud induction (92 %) was observed in leaf petiole explants with 2.0 mg/L6-BAP concentration compared to cotyledonary node explants. The induced shoots were kept for elongation and maximum percentage of elongation (93 %) was noticed in leaf petiole explants with 1.0 BAP + 0.1 NAA + 2.0 GA3 mg/L concentrations compared to cotyledonary node explants. The well-developed shoots of both the explants showed profuse rooting, where high percentage of rooting (95 %) was observed in leaf petiole explants with 0.5 mg/L IBA concentration. The pattern of amplification resulted through RAPD analysis confirmed the genetic stability of in vitro regenerated plants. Improvement: The regeneration protocol standardized in this study is suitable and reliable to develop transgenic pigeon pea plants by agrobacterium mediated genetic transformation. Keywords: Auxins, Cytokinins, Gibberellins, Organogenesis, Pigeonpea

The Hazards of Building in the Vicinity of Electromagnetic Fields: Lessons for Building Code Enforcement in Nigeria

This paper dealt with the topic of electromagnetic field (EMF) and its effects on building occupants when such buildings are located within the vicinity of the field. Two main sources of EMF, namely, high voltage power transmission lines and cellular towers, were reviewed. Empirical evidence revealed that they have a tendency to emit electromagnetic fields and they have been determined to be hazardous to building occupants. Studies have also established that when buildings are erected within an unsafe distance to the fields, occupants of such buildings become exposed to health risks. Indeed, evidence exists to show that exposure to these fields can lead to cancer in children and that men exposed to the fields are also susceptible to health risks. Studies by the International Agency for Research on Cancer (IARC) among others, assessed the carcinogenicity of radiofrequency electromagnetic fields (RF-EMF) positing that human responses to RF-EMF can occur from use of personal devices such as mobile telephones, cordless phones, Bluetooth, and amateur radios; from occupational sources such as high frequency dielectric and induction heaters, and high-powered pulsed radars. Exposures can also occur from environmental sources such as mobile phone base stations, broadcast antennas, and medical applications. This paper also examined standards for safe distances and buffers for building location with respect to EMFs and made recommendations for policy makers and building code enforcement services. Keywords : Building Codes, Epidemiology, Carcinogenicity, Radio Frequency, Extreme Low Frequency, Non-Ionizing Radiation DOI : 10.7176/JETP/9-3-01 Publication date :March 31 st 2019

Modeling Study for Li-ion Batteries Considering High-frequency Inductance Characteristics Based on Electrochemical Impedance Spectroscopy

As a non-destructive test method, electrochemical impedance spectroscopy (EIS) has been widely used in the analysis and diagnosis of Li-ion batteries in recent years. But the study of the high-frequency characteristics of Li-ion batteries is still not enough and the performance of Li-ion batteries at high frequency is not the same with that of the pure capacitance or pure inductance. Based on EIS, a fractional equivalent circuit model considering high-frequency inductance characteristics is established in frequencies from 10mHz to 10kHz in this paper. Then the model is verified and the parameters of the circuit are explored by using differential evolution (DE) algorithm and fractional-order numerical operations. Compared with the traditional equivalent circuit model, a fractional-order model based on EIS can not only describe the characteristics of the battery more comprehensively but also reduce the number of parameters because each component can simulate a certain physicochemical process of Li-ion batteries. The dominant process of the battery reaction is diverse in different frequency bands and therefore the structure of the developed model can be simplified accordingly. For the high-frequency inductive analysis of the battery, results show that the battery's 'inductance-like' phenomenon has a certain relationship with the frequency. This discovery might be implemented in a power electronic circuit to improve understanding of how batteries react to working condition of high-frequency.

Thermal stability of nanocrystalline Al−10Fe−5Cr bulk alloy

Abstract Thermal stability of nanocrystalline Al−10wt.%Fe−5wt.%Cr bulk alloy was investigated. The initial micro-grained mixture of powders was processed for 100 h using mechanical alloying (MA) to produce nano-grained alloy. The processed powders were sintered using high frequency induction heat sintering (HFIHS). The microstructures of the processed alloy in the form of powders and bulk samples were investigated using XRD, FESEM and HRTEM. Microhardness and compression tests were conducted on the bulk samples for evaluating their mechanical properties. To evaluate the thermal stability of the bulk samples, they were experimented at 573, 623, 673 and 723 K under compression load at strain rates of 1×10−1 and 1×10−2 s−1. The annealed samples exhibited a significant increase in their microhardness value of 2.65 GPa when being annealed at 723 K, as compared to 2.25 GPa of the as-sintered alloy. The bulk alloy revealed compressive strengths of 520 MPa and 450 MPa at 300 K and 723 K, respectively, when applying a strain rate of 1×10−1 s−1. The microstructural stability of the bulk alloy was ascribed to the formation of iron and chromium containing phases with Al such as Al6Fe, Al13Fe4 and Al13Cr2, in addition to the supersaturated solid solution (SSSS) of Cr and Fe in Al matrix.

Analytical Calculation of Static Capacitance for High-Frequency Inductors and Transformers

This paper presents a modified methodology for calculating static capacitance values between conductors with a circular cross section. Two forms of coil's stacking were considered, perfectly in 90° and each layer embedded in the previous one. Finite element simulations were carried out to determine the capacitance values for a 5 × 5 array arrangement, taking into account the two stacking forms. It was observed that depending on the position of the turn in the coil, it could present different capacitances values for the adjacent turns. A comparison between the proposed and existing methods for over isolated conductors was performed as well. The proposed method displayed good agreement with simulation and experimental results. The gain of the proposed method can be even more appreciated when comparing results for over insulated conductors.