Winding Turns Research Articles

An explicit algebraic model of the planetary boundary layer turbulence: test computation of the neutrally stratified atmospheric boundary layer

An explicit algebraic model of Reynolds stresses and the turbulent heat flux vector for the planetary boundary layer in a neutrally stratified boundary layer of the atmosphere above a homogeneous rough surface is tested. The version of the algebraic model under consideration is constructed on the physical principles of the RANS (Reynolds-averaged Navier−Stokes) approximation for describing stratified turbulence, it employs three forecasting equations, and a correct reproduction of the main characteristics of a neutral atmospheric boundary layer — the components of the mean wind velocity, the wind turn angle, and the turbulent statistics is shown. Test computations show that the proposed model may be used for goal-oriented investigations of the atmospheric boundary layer.

Hybrid DC converter with low switching loss and less ripple current

A hybrid DC/DC converter is studied for direct current microgrid applications to have benefits of low switching losses with wide range of operation load, less winding turns of transformer secondary side, low ripple current on output side and high circuit efficiency. The studied converter includes a phase-shift pulse-width modulation full-bridge circuit and a half-bridge circuit to reduce the switching losses at lagging-leg switches. In the secondary side of the studied converter, two inductors, four diodes and two transformers are adopted to perform partial ripple current reduction and minimise the winding turns. The studied converters are verified with a 1200 W prototype by the experimental results.

Mathematical model of high-voltage instrument autotransformer intended for use in smart grid networks

The object of the research is a mathematical model of the active part of the high-voltage instrument autotransformer with several output windings. The most challenging task in this model is leakage inductance calculation of single winding turns or groups of autotransformer winding turns. Also, a significant problem when calculating the parameters of the autotransformer are those operating conditions, that are close to no-load conditions. To create a mathematical model of the active part of a high-voltage autotransformer, taking into account the leakage inductance of each single winding turn (or groups of winding turns), and also the magnitude and type of the load, it is proposed to modify the known system of transformer equations detailed to the level of single turns (or groups of turns) and use the proposed method for determining the partial self- and mutual- leakage inductances by numerical methods. With a help of the developed mathematical model of the active part of a high-voltage autotransformer, a prototype of a 10 kV autotransformer with high metrological characteristics was designed and manufactured. Positive results of metrological certification of the created high-voltage autotransformer confirmed the possibility of calculating the parameters of such primary high-voltage transformers that can be used in Smart Grid networks in conjunction with analog-to-digital converters, thus unifying the electromagnetic primary high-voltage transformers. It is shown that the operating conditions of high-voltage autotransformers, close to no-load conditions, allow easily achieve high accuracy of high voltage transformation.

How Shifting Winds Turn Tropical Storms into Hurricanes

Researchers present a novel method for analyzing how wind shear affects tropical cyclone strength and structure.

How much detail is needed in modeling a transcranial magnetic stimulation figure-8 coil: Measurements and brain simulations.

BackgroundDespite TMS wide adoption, its spatial and temporal patterns of neuronal effects are not well understood. Although progress has been made in predicting induced currents in the brain using realistic finite element models (FEM), there is little consensus on how a magnetic field of a typical TMS coil should be modeled. Empirical validation of such models is limited and subject to several limitations.MethodsWe evaluate and empirically validate models of a figure-of-eight TMS coil that are commonly used in published modeling studies, of increasing complexity: simple circular coil model; coil with in-plane spiral winding turns; and finally one with stacked spiral winding turns. We will assess the electric fields induced by all 3 coil models in the motor cortex using a computer FEM model. Biot-Savart models of discretized wires were used to approximate the 3 coil models of increasing complexity. We use a tailored MR based phase mapping technique to get a full 3D validation of the incident magnetic field induced in a cylindrical phantom by our TMS coil. FEM based simulations on a meshed 3D brain model consisting of five tissues types were performed, using two orthogonal coil orientations.ResultsSubstantial differences in the induced currents are observed, both theoretically and empirically, between highly idealized coils and coils with correctly modeled spiral winding turns. Thickness of the coil winding turns affect minimally the induced electric field, and it does not influence the predicted activation.ConclusionTMS coil models used in FEM simulations should include in-plane coil geometry in order to make reliable predictions of the incident field. Modeling the in-plane coil geometry is important to correctly simulate the induced electric field and to correctly make reliable predictions of neuronal activation

Competition Scenario of Taiwan Transformer Industry

A major applicant of transformers was to increase voltage before transmitting electrical energy over long distances through wires. Most of consumer and commercial electronics for daily using like personal computers, home theaters, air conditions, TVs, cell phones and notebooks, etc., needed transformers to do electrical transfer. Moreover, in order to adopt the design of consumer and commercial electronic devices, the specifications of transformers including the circuits, diameter of wires, turns of windings, and size of cores and bobbins were different; transformers were customization. There were standard specifications for transformers. The common types of transformers were EI type and toroidal type, etc. Due to the internationalization and concentration of business, economic executives no longer had a strong connection with their place of production. Production locations could transfer or collapse for various reasons, amongst them changing cost factors or competition.

The Long and Winding Road After FDA Approval: A Medical Device Industry Perspective.

> The road is long > > With many a winding turn > > That leads us to who knows where > > Who knows where > > —“He Ain’t Heavy, He’s My Brother,” by Bob Russell and Bobby Scott The pitch begins like this: “Patients with #NameYourDisease represent a large market with a significant unmet medical need.” It goes on: “Our #NameYourTechnology is currently in development and promises to improve patient outcomes.” Then without fail, a Gantt chart shows the (best-case) plans for development, preclinical testing, and clinical trials. All of which leads to the pot of gold at the end of the bar chart rainbow: approval by the US Food and Drug Administration (FDA). For many years, this strategy was all it took to make a new therapy successful. All we in industry had to do was to build it—and provide reasonable assurance that it was safe and effective for use in the United States—and patients and providers would come. Like superannuated generals always preparing to fight the last war, many in medical technology continue viewing FDA approval as the end goal of medical research and development efforts. Since leaving academia and joining industry ≈8 years ago, I have found that the world is more complicated than that. Today, FDA approval is just 1 waypoint on a long, winding, and …

High performance 3D printed electronics using electroless plated copper

This paper presents design and performance validation of 3D printed electronic components, 3D toroidal air-core inductors, fabricated by multi-material based Fused Deposition Modelling (FDM) 3D printing technology and electroless copper plating. Designs of toroidal inductor is investigated with different core shapes and winding numbers; circular and half-circular cores with 10 and 13 turns of windings. Electroless plated copper thin film ensures 3D printed toroidal plastic structures to possess inductive behaviors. The inductance is demonstrated reliably with an applied source frequency from 100 kHz to 2 MHz as designs vary. An RL circuit is utilized to test the fabricated inductors’ phase-leading characteristics with corresponding phase angle changes.

A vertical wind structure that leads to extreme rainfall and major flooding in southeast Australia

Here we examine winds associated with extreme rainfall and major flooding in coastal catchments and more broadly over southeastern Australia. Both radio-sonde and re-analysis data are examined. In every case (i) atmospheric moisture content is high and (ii) the low-level winds are onshore, and in almost every case (iii) the wind-direction turns anti-cyclonically with increasing height up to 500 hPa. Data from Brisbane extending back more than 50 years is consistent with this behavior: winds turn anti-cyclonically with increasing height on days with heavy rainfall, whereas winds turn cyclonically with increasing height on days with light or no rainfall. In the coastal zone, extreme rainfall rarely occurs without (i), (ii) and (iii). In eastern Australia beyond the coastal zone, conditions (i) and (iii) are also associated with extreme rainfall. We found very few cases where such conditions were not associated with extreme rainfall in this broader region. This study extends previous work by showing that the link between turning winds and rainfall exists in both the tropics and subtropics, and the link applies in cases of extreme rainfall and associated major flooding.

Online technique for insulation assessment of induction motor stator windings under different load conditions

This paper presents a new condition monitoring system which is able to evaluate and diagnose the stator winding insulation deterioration (SWID) at its initial stages. During the last few decades, considerable efforts have been made in condition monitoring of SWID in induction motors. Nevertheless, an effective diagnosis technique that can lead to a fast and accurate detection of SWID shortly after its occurrence remains a challenge. A new modelling technique is introduced using finite element method which enables detailed simulation (two turn-to-turn resolution) of insulation degradation in a stator slot. Experimental setup is then used to validate the proposed modelling technique. The detail and approximation coefficients of the discrete wavelet transform are shown to provide effective detection of SWID within a few seconds after its occurrence. The proposed system continuously monitors the status of the induction motor and is able to detect the insulation deterioration of only 1.2% turns of phase winding when it starts to take place. The proposed method is only applicable to turn insulation failure detection. Its viability under different load conditions is validated for a small-sized induction motor with simulated turn insulation fault.

The regime shift in the 1960s and associated atmospheric change over the southern Indian Ocean

The change of sea surface temperature (SST) in the southern Indian Ocean (SIO) during the recent six decades has been analyzed based on oceanic reanalysis and model, as well as atmospheric data. The results show that a thermal regime shift in SIO during the 1960s, which is not caught enough attentions, has been of equal magnitude to the linear warming since 1970. Empirical Orthogonal Function (EOF) analyses reveal that a thermal shift is combined with atmospheric changes such as the weakening of westerly during the period of 1960–1967. Inner dynamic connections can be defined that when the westerly winds turn weak, the anticyclonic wind circulation between westerly winds and the trade winds decreases, which further reduces the SST to a negative peak in this period. It is noted that the shifts in the 1960s are also evident for Southern Hemisphere. For example, subtropical high and the entire westerly winds belt at high latitudes both change dramatically in the 1960s. This large-scaled process maybe link to the change of southern annular mode (SAM).

Обеспечение передачи заданной мощности в системе бесконтактного заряда аккумуляторных батарей подводного аппарата

The object of the research is a high-frequency power transformer with separating primary and secondary parts making up a system of contactless power transmission at the autonomous unmanned underwater vehicle (AUUV) for charging its storage batteries. As a research task a delivered justification and development of a methodology for calculating the design parameters of a transformer meeting the delivered requirements for the transmitted power under specified opera­ting conditions is provided. The research is based on a mathematical modeling of electromagnetic processes in the transformer performed in the software package ANSYS Maxwell combined with a live experiment. The characterizing parameters in the form of the magnetic coupling coefficient and the specific inductance of the coil winding turn are identified and their application for the complete identification of the object properties is justified. A system of relative units is proposed in which the characterizing parameters have a constant value for any cores of the same size which makes it easy to scale the results of the received technical solutions when the requirements for the transmitted power change. A method is proposed for determining approximate polynomials connecting arrays of values of the coupling coefficient and specific inductance with the relative values of the gaps between the contact surfaces of the transformer parts and the inter-axial displacements which may possibly occur when the underwater vehicle is automatically moored to the base. The performed studies made it possible to propose a technique for calculating the basic design parameters of the transformers with the initial data in the form of a combination of the specified electrical characteristics and the limitations imposed on the accuracy of the docking of the contact surfaces of the transformer parts. Experimental studies of selected transformer constructs similar to those adopted in the modeling confirm the reliability of the results presented. The results obtained relate to cup-type ferrite cores, but the approaches adopted in the studies make it pos­sible to extend the calculation technique to other transformer designs that can be used in the systems of AUUV contactless battery charging.

Progress of "Yoroi-coil Structure" in Mechanical Strength with High Current Density

Yoroi-coil (Y-based oxide superconductor and reinforcing outer integrated coil) structure has been developed to fabricate very strong pancake coils against electromagnetic force. In Yoroi-coil structure, the outer supporting structure is effective to make a mechanically robust coil having a high current density in the case that the hoop stress must exceed the yield strength of a REBCO-coated conductor without this reinforcement. By the experiments and analysis, we pointed out that the remarkably weak delamination stress can cause the delamination of the coated conductor in coils. So that Yoroi-coil structure has advantages to delamination because it could maintain a coil shape with reinforcing materials, without impregnation. Since higher current density is required by various applications, the Yoroi-coil using austenitic stainless steel reinforcing frames and plates, has been verified by the hoop stress test with high current density. Then, high coil current density of 446 A/mm 2 was achieved by the Yoroi-coil-structured double pancake (DP) coil, with the total number of the winding turns of 574, at 4.2 K in the back-up magnetic field of 11 T. The inner and outer diameters of the DP coil were 190 and 250.1 mm, respectively. Although the hoop stress evaluated on the assumption of excluding the supporting structure exceeds 1 GPa, Yoroi-coil structure restricted the strain of coil winding ranging 0.2% to 0.3%. The stainless steel reinforcing member well supported a part of electromagnetic force in Yoroi-coil structure, even with high coil current density.

Informational Indicators of the Stator Winding Fault for the Relay Protection Construction of an Autonomous Asynchronous Generator

The experiments proved that the short circuit in the small amount of the stator winding turns of an autonomous asynchronous generator does not lead to the generator demagnetization. It was shown that the current in the closed turns far exceeds the nominal current value, depends on the resistance in the fault location and the percentage of the closed turns. With the use of the experiment, the regression equations of the currents in the closed turns and the currents of stator phases as a function of the number of turns, the excitation capacity and the load value were obtained. The applicability of a change in the harmonic composition of currents and vibrations for determination of the inter-winding fault occurrence moment is described. The recommendations for relay protection development on the basis of the detected informational indicators of the short circuits are given.

Performance Investigation of a Brushless Synchronous Machine With Additional Harmonic Field Windings

This paper describes a brushless electrically excited synchronous machine with a distinctive rotor structure and additional harmonic field windings. Spatially distributed third harmonic magnetic fields will be created in the air gap by feeding the stator harmonic windings of a dc current. These harmonic MMFs will generate an induced voltage in the additional rotor harmonic coils, which can supply the field winding with a dc current after rectification. Based on this operation principle, distributions of harmonic windings and the stator harmonic magnetic fields are analyzed. The relationship between harmonic EMFs and rotor harmonic winding turns are studied. Mutual interference between the different magnetic fields and windings in the machine is discussed. The harmonic excitation fields and the air gap flux densities are then calculated by employing finite element methods, and the regulating characteristics of no-load EMF are analyzed and power losses of machine are discussed. Experimental results of one 1.0-kW prototype machine agree well with the theoretical analysis and finite element calculations, which helps to evaluate this type of synchronous machines having brushless electrical excitation.

Fault Diagnosis Method of Permanent Magnet Synchronous Motor for Electrical Vehicle

The permanent magnet synchronous motor has high efficiency driving performance and high power density output characteristics compared with other motors. In addition, it has good regenerative operation characteristics during braking and deceleration driving condition. For this reason, permanent magnet synchronous motor is generally applied as a power train motor for electrical vehicle. In permanent magnet synchronous motor, the most probable causes of fault are demagnetization of rotor's permanent magnet and short of stator winding turn. Therefore, the demagnetization fault of permanent magnet and turn fault of stator winding should be detected quickly to reduce the risk of accident and to prevent the progress of breakdown of power train system. In this paper, the fault diagnosis method using high frequency low voltage injection was suggested to diagnose the demagnetization fault of rotor permanent magnet and the turn fault of stator winding. The proposed fault diagnosis method can be used to check the faults of permanent magnet synchronous motor during system check-up process at vehicle starting and idling stop mode. The feasibility and usefulness of the proposed method were verified by the finite element analysis.

Modeling and Diagnostic of Incipient Interturn Faults for a Three-Phase Permanent Magnet Synchronous Motor

This paper discusses incipient end-winding interturn faults in the stator winding of a permanent magnet synchronous motor caused by the mechanical vibrations of the concerned turns. With aging, the end-winding blocking system becomes weaker and turns insulation degrades until its breakdown. The fault is modeled by an intermittent interturn short circuit between the turns of the stator end winding. Intermittent fault occurrence disturbs the stator currents as well as the reference voltages leaving a specific fault signature. The detection method uses a pattern-adapted wavelet to detect fault occurrence. In this paper, it is applied to the quadrature reference voltage. Simulation and experimental results confirm the effectiveness of the proposed approach.

Performance Analysis of SISFCL with the Variation of Circuit Parameters using Jiles Atherton Hysteresis Model

Abstract In modern day power systems, fault current limiters (FCL) are used to provide protection from high fault currents in the event of electrical faults and thus help to deliver uninterrupted electric supply to the consumers. Several technologies of FCLs are available for practical usage. However, the saturated iron-core superconducting fault current limiter (SISFCL) has gained a lot of attention in recent years in view of its ability to offer very low impedance during normal operation and high impedance during faulted condition. Previous mathematical models defining the performance of the device employs a simple BH curve. But as the change in mathematical state of saturation and unsaturation is important for the operation of the device, the paper investigates the responses considering the effects of magnetic hysteresis utilising the Jiles Atherton hysteresis model. Further the performance of the device is analysed with the variations of different parameters viz., the fault resistance magnitude, DC bias current, number of turns of the AC winding and number of turns of the DC winding that portray the effectiveness of the parameters encouraging an optimal design of the limiter.

Soft switching DC/DC converter with high voltage gain and less current ripple

SummaryA new soft switching three‐level converter with two DC/DC circuits in the primary side and current double rectifiers in the secondary side is presented to realize the zero‐voltage switching operation, reduce the transformer secondary winding turns and the output current ripple, and lessen the voltage rating of rectifier diodes. Two DC/DC pulse‐width modulation circuits sharing same power switches with interleaved half switching cycle are adopted in the proposed converter to reduce the current rating of transformer primary windings. Two inductors and four diodes are adopted in the secondary side to achieve current double rectifier, reduce output ripple current, and decrease the transformer secondary winding turns. Based on the pulse‐width modulation scheme, the power switchers can be turned on at zero‐voltage switching operation. Laboratory experiments with a 1.44 kW prototype are provided to verify the theoretical analysis. Copyright © 2016 John Wiley & Sons, Ltd.

Study on Initial Current-Limiting Performance of the Resistive-Type SFCL Element According to the Electrical Coupling Condition With Cores and Coils

This paper was conducted to widen the use of the YBCO-coated conductor's superconducting current-limiting element under the electrical coupling condition with cores and coils. Using cores and coils, diverse winding directions and turn ratios were available, and the initial operating performance of the superconducting current-limiting element could be improved. In this paper, three kinds of YBCO-coated conductors with stabilization layers that had different specific resistivity values were used to fabricate superconducting current-limiting elements, and an electrical coupling condition, which did not produce resistance in the normal operating condition when it was combined with the superconducting current-limiting elements, was presented. After the superconducting current-limiting elements were combined with the electrical coupling condition, an overcurrent was applied, and the initial operation performance was examined. The initial operation performance indicators were the current-limiting rate, response time, and steep slope of the initial current-limiting curve. The current-limiting rate was excellent when the specific resistivity of the superconducting current-limiting element was high and when it was combined with the electrical coupling condition to increase the equivalent impedance. However, when the specific resistivity of the YBCO-coated conductors to the superconducting current-limiting elements was too low, the electrical coupling condition did not work properly. The response time and steep slope of the current-limiting curve characteristics showed that they did not depend on the specific resistivity of the superconducting current-limiting elements when the equivalent impedance of the electrical coupling condition was higher than the resistance of the superconducting current-limiting elements.