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This paper discusses the synchronous operation of a brushless doubly fed reluctance machine (BDFRM). Basic operation theory of a ducted rotor BDFRM is reviewed, and mathematical analysis relating to synchronous operation is presented. Corresponding control strategy for synchronous speed operation is discussed. A prototype machine is built and implemented as a motor drive. Subsequently, the BDFRM drive is tested in synchronous mode of operation at varying speed levels and loads. [ABSTRACT FROM AUTHOR]

This paper studies the effect of common-mode voltage elimination (CMVE) on the iron loss of electrical machine core laminations under multilevel converter supply. Three identical magnetic ring cores are excited by either a three-level converter or a five-level voltage source converter to study the behavior of CMVE on a three-phase system. Both multilevel converters are controlled by using a space vector pulsewidth modulation as it is one of the most often used techniques for CMVE. These experimental results are confirmed numerically with a dynamic iron loss model. In addition, the effect of CMVE, at different switching frequencies, on the core loss of a synchronous machine is numerically studied. The results presented in this paper show that the core loss is considerably increased when the CMVE is implemented. However, this iron loss increase in the five-level drive systems is lower compared with the three-level ones. Therefore, it is important that the designers of drive systems take such effects into consideration. [ABSTRACT FROM AUTHOR]

An outer-permanent magnet tubular linear generator has been designed to increase the power density and distance of relative movement. The design of the two buoys has been completed. This paper describes the detailed design process of the proposed generator. The magnetic network model of the proposed generator is implemented to analyze the performance. Considering the cogging force and voltage, the linear generator has been optimized and the final parameters have been determined. Based on the design results, the integrated wave converter system has been manufactured and put into China’s Yellow Sea. The measured voltage is highly consistent with the simulation data. All of results show that the proposed generator is well suitable for wave energy conversion. [ABSTRACT FROM AUTHOR]

This paper presents a novel topology of a planetary magnetic gear having only two rotating parts. The proposed gear is a planetary mechanism with two internal engagements that is typically characterized by high torque density. The operational principle and basic design considerations are discussed. The proposed topology offers a simple rotational motion of input and output shafts that does not require additional mechanical converters. The simulation study is carried out with the gear having the gear ratio of −14 with the 2-D finite-element method. The modeling gave promising results in comparison with other high-performance topologies of magnetic gears. The proposed magnetic gear demonstrates torque density of $187~\text {kN}\cdot \text {m}/\text{m}^{3}$ and maximum torque per volume of permanent magnets of $825~\text {kN}\cdot \text {m}/\text{m}^{3}$. Finally, a 3-D sketch is developed showing principal mechanical design peculiarities of the proposed magnetic gear. [ABSTRACT FROM AUTHOR]

This paper examines the nonlinear behavior of inserted type integrated magnetics used in linear level control converters. Due to the nonlinear behavior of the magnetics, an implementation of the insertion type magnetic integration needs to be carefully considered. The saturation of magnetics is normally not a concern in high-voltage input applications, but becomes a serious issue when designing for low-voltage input and high power applications. In this paper, the inserted type integrated magnetics has been categorized into two types according to their magnetic integration configurations. Investigation and discussion of their nonlinear behavior will be presented with the assistance of 3-D simulation results based on the finite-element method. A case study of a 350 W dc–dc converter is used throughout this paper for the ease of illustration. [ABSTRACT FROM AUTHOR]

This paper provides comparative analysis between 2-D and 3-D numerical modeling of electromechanical devices by considering typical errors arising when 2-D models are assumed to model 3-D fields. It is argued that modeling simplifications need to be applied with great care as associated errors are not always predictable. In hierarchical design, both types of models are desirable hence balancing accuracy and computational effort is an increasingly important issue. Three examples are provided to illustrate the comparisons. The first shows a system with magnets for which magnetic field can be calculated analytically. The second concerns torque calculations in a permanent magnet motor. Finally, the third looks at a coil above a conducting plate with induced eddy currents. It is argued that by careful modification of selected parameters the 2-D results could be improved to make them consistent with 3-D models. [ABSTRACT FROM AUTHOR]

The Jiles-Atherton (J-A) model is very suitable for modeling ferrite-core based inductors and transformers. In this paper the differential evolution (DE) method was applied to extract five parameters in static J-A model first. Then it was applied to extract another two parameters in dynamic J-A model with five parameters in static J-A model as inputs. It is found that extracting five parameters in static J-A model is relatively easy but extracting another two parameters in dynamic J-A model needs extra effort, especially specifying their ranges. After obtaining all seven parameters, we applied dynamic J-A model to predict the current behavior of a practical switching circuit and successfully obtained the inrush current phenomenon as experimentally observed and reported in literature. We conclude that application of DE method to extract seven parameters in dynamic J-A model for ferrite is feasible. [ABSTRACT FROM PUBLISHER]

This paper presents a thermal model of power converter used in switched reluctance motor (SRM) drive under constant convective heat transfer. The distribution of the system temperature rise is derived based on the average heating power measured as SRM is running steadily, and the temperature rise is independent of ambient temperature which is proved in this paper. The accuracy of the thermal model is verified by comparing experimental data with the results derived from finite-element method (FEM) simulation. Furthermore, this study achieves optimization in heat sink geometry and the placement of power components with the present model. [ABSTRACT FROM PUBLISHER]

An encouraging way to convert ocean wave energy into electricity through direct drive is by using a linear, synchronous, longitudinal-flux permanent-magnet machine (LFM), where the piston is driven by a buoy. In this paper, the speed of the piston is assumed to be constant or sinusoidal. The paper presents an automated method for optimizing the design variables of an LFM with a rectifier, using time-stepping finite-element analysis. The method yields feasible LFM designs tailored to a given ocean wave climate, assuming constant or sinusoidal piston speed. The method will help to avoid a large amount of field calculations to obtain an optimal LFM driven by a buoy. The systematic approach results in a transparent investigation, giving the engineer an easy way to determine the best design. The paper presents LFM designs for a calm site in the Baltic Sea as examples. [ABSTRACT FROM AUTHOR]

Recently high-frequency common magnetic links with cores of advanced magnetic materials, such as nanocrystalline and amorphous materials, have been considered as viable candidates for the development of medium-voltage power converters. This offers a new route of step-up-transformer-less compact and lightweight direct grid integration of renewable generation systems. Most importantly, it minimizes the voltage imbalance and common mode issues of the converter systems. However, the electromagnetic design of high-frequency common magnetic links is a multiphysics problem and thereby affects the system efficiency and cost. In this paper, an optimization technique is proposed and verified by prototype magnetic links. The design optimization, implementation, test platform, and experimental test results are analyzed and discussed. [ABSTRACT FROM AUTHOR]

This paper presents a sensorless bifilar wound permanent magnet brushless DC (BW-PMBLDC) motor fan for automotive engine cooling applications. The key is to incorporate the bifilar winding design into the conventional half-wave PMBLDC motor. Due to the perfect flux-coupling effect between bifilar winding, a regenerative capability is developed so that the trapped energy in the conducting winding during the turn-off period can be re-dumped to DC source through the other winding in the bifilar pair, hence effectively promoting the energy efficiency and repressing the voltage spikes. Moreover, the complementary scheme developed between the bifilar wound phases enables bipolar excitation on the unipolar converter topology. Therefore, the BWPMBLDC motor cannot only offer the advantages of full-wave motor in efficiency, voltage spike reduction, and low torque ripple, but also retain the advantages of simplicity and robustness of unipolar converter topology. Both simulation and experimental results are presented to validate the feasibility. [ABSTRACT FROM AUTHOR]

This paper proposes the unified control for a novel wind turbine-superconducting magnetic energy storage (SMES) hybrid system, where the SMES coil is integrated with the DC link of the current source converter (CSC) fed wind energy conversion system. The unified power and current control schemes are proposed for general grid conditions by designing the proper active damping, the closed-loop grid current regulation, and the decoupled double synchronous frame phase locked loop (DDSRF-PLL). Furthermore, the system operation schemes are proposed and designed for both the normal SMES current condition and the low SMES current condition. The performance of the proposed control schemes are verified by computer simulation. [ABSTRACT FROM AUTHOR]

This paper explores a passive, two-port electromechanical device that employs electrodynamic transduction to yield transformer-like electrical behavior. The device—coined an “electrodynamic transformer” (ET)—comprises two coils that are coupled by their electrodynamic interaction with a strong, static magnet field, supplied by permanent magnets. A prototype structure is built and tested to explore the concept. Operating at 22 Hz, the proof-of-concept device provides a peak open-circuit voltage gain of 12, and a peak efficiency of 39%. The voltage gain is also electrically tunable within the range of \pm5%. [ABSTRACT FROM AUTHOR]

In a high-speed train application, the modularized traction converter produces the significant harmonic currents caused from the switching behavior of a power converter. These harmonic currents bring the interference among the traction equipment. One way to minimize the interference is to design the secondary windings of a power transformer decoupled magnetically as possible. This paper presents a magnetic-field analysis on a winding disposition to clarify an impact on magnetic decoupling between secondary windings, under a limited height of a train. Two winding dispositions for a single-phase shell-type transformer are constructed and simulated by a three-dimensional finite-elements method (FEM) model. The simulation results with two different winding dispositions are provided and the experiments show good agreement with the simulation results. [ABSTRACT FROM AUTHOR]

Interleaved power converter topologies have received increasing attention in recent years for high power and high performance applications. The advantages of interleaved boost converters include increased efficiency, reduced size, reduced electromagnetic emission, faster transient response, and improved reliability. The front end inductors in an interleaved boost converter are magnetically coupled to improve electrical performance and reduce size and weight. Compared to a direct coupled configuration, inverse coupling provides the advantages of lower inductor ripple current and negligible dc flux levels in the core. In this paper, we explore the possible advantages of core geometry on core losses and converter efficiency. Analysis of FEA simulation and empirical characterization data indicates a potential superiority of a square core, with symmetric 45° energy storage corner gaps, for providing both ac flux balance and maximum dc flux cancellation when wound in an inverse coupled configuration. [ABSTRACT FROM AUTHOR]

This paper presents the fabrication and characterization of air-core power inductors that leverage vertically-stacked, thick copper spiral windings to deliver high inductance densities >100 nH/mm^2 and quality factors >10 on silicon substrates. The inductors are designed for on-chip or in-package integration with high-frequency power converter circuits to enable chip-scale power management in size-constrained applications. A process for realizing the inductors through multilevel, three-dimensional molding of electroplated copper structures has been enhanced with capabilities for four independent copper layers in thicknesses of up to 30 \mum each. The impact of increasing the thickness of the stacked copper traces is specifically explored and compared to similar inductors with 10-\mum-thick stacked windings. Impedance characterization revealed a drastic decrease in the series resistance in the thicker inductors as desired but also revealed undesired eddy current and magnetic coupling effects. [ABSTRACT FROM PUBLISHER]

Electrical machines with distributed concentrated windings are challenging the selection of the soft magnetic materials due to stator design and power conversion efficiency. A shorter magnetization path and relatively high magnetization frequency is beneficial for low-permeability soft magnetic materials with low power losses in the core. In this paper, a three-phase machine with laminated and iron powder cores is analyzed with focus on a modular winding design, the torque capability, and the stator energy conversion efficiency. Different iron powder cores are compared to a laminated core using 2-D finite element analysis (FEA). The three-phase machine torque is compared among a conventional distributed concentrated winding, an axially distributed wave-winding, and a number of circumferentially distributed wave-winding segments. According to 3-D FEA, the conventional coils are preferred if the permeability of the core is low. [ABSTRACT FROM PUBLISHER]

Focuses on a study in which a method for analyzing a forward converter in electromagnetic field with hysteresis and circuit equations is implemented. Specification of the forward converter; Simulation and experimental results; Conclusions.

The benefit of magnetoconvection for transformer cooling by ferrofluid is numerically studied. A code combining spectral and finite-element methods is applied on a solenoid system. Magnetostatic, Navier–Stokes, and energy equations are solved simultaneously. A vegetable oil seeded with magnetite nanoparticles at a volume fraction of 10% is considered. The magnetization of the ferrofluid is a function of temperature through an approximation of the classical Langevin’s law. Magnetic and temperature fields are used to update the magnetic action, modeled by the Kelvin force, on the ferrofluid momentum at each time step. Numerical results for regular oil are consistent with experimental temperature data obtained for pure vegetable oil cooling. Numerical results for ferrofluid show that the magnetoconvection modifies the flow convection pattern and speed. The temperature increase in the coil is consequently reduced by about 9.4% with ferrofluid cooling. [ABSTRACT FROM AUTHOR]

An experimental scale-down model of ultra high voltage direct current converter transformer is designed and manufactured to study the wave process in the winding under impulse voltage. Nine outgoing lines are configured on different winding coils of the scale-down model. The voltage waveforms of different outgoing lines are obtained by the lightning impulse voltage. The simulation model of scale-down transformer is established to calculate the distributed parameter matrices through the finite-element method. The equivalent circuit of the transformer winding is proposed to calculate the voltage waveforms and the potential gradient distribution. The comparative analysis of test and simulation results shows that the oscillating voltage occurs in the winding, and the simulation results can reflect the wave process characteristics. [ABSTRACT FROM AUTHOR]

A novel high power factor converter is presented in this paper. The proposed converter is a high-frequency forward converter controlled by a magnetic amplifier. This converter has no need of special control to correct the power factor. Power factor is corrected by the automatic variation of the saturation time of the magnetic amplifier according to the input voltage variation. The current stress of the transistor switch is low because this converter operates in the continuous conduction mode of the inductor current. The circuit operation is verified experimentally at a frequency of 500 kHz. [ABSTRACT FROM PUBLISHER]

To use a permanent magnet (PM) synchronous generator to wind power generation systems, the wind turbine characteristics according to wind speed should be considered in the design stage and performance evaluation. Using the wind turbine characteristics provided by a manufacturer, we predict the performance of a wind power generator that uses an axial flux PM by analyzing the electromagnetic field characteristics. To avoid the long analysis time required by the three-dimensional finite element method because of the structural features of axial flux PM machines, an alternative analytical approach is presented, and its results are validated experimentally. In addition, we present an AC-DC-DC converter that is connected to the experimental setup for back-to-back tests in order to obtain constant output regardless of wind speed variations. [ABSTRACT FROM AUTHOR]

Two different numerical algorithms for computing the Ohmic and eddy-current winding losses of converter transformers are presented. The higher harmonic components of the nonharmonic electric current, generated by the rectifying part of the power electronic converter, are fully taken into account. The calculated numerical results are verified by comparison with measured results. [ABSTRACT FROM PUBLISHER]

A finite element method, which directly uses the node electric scalar potentials and node charge densities as variables, is used to predict the electric field and charge density distributions under polarity reversal (PR) voltage. The penalty method is adopted to impose the Dirichlet boundary values and the Crank–Nicolson (C-N) algorithm is then used to solve the transient equation. The surface node charge densities on the perfectly conducting boundaries are adopted to accurately obtain the normal electric field strengths. The method is tested by a two layer coaxial model and applied to analyze the linear and nonlinear transient electric fields and boundary charge densities of a \pm500 kV converter transformer under PR voltage. [ABSTRACT FROM PUBLISHER]

We describe a method for determining the split winding distribution for coupled inductors in interleaved converters. Our method greatly reduces the footprint and copper losses of the magnetic component. We discuss the analysis and design method for the coupled inductors in detail. We use a geometrical method to solve problems such as uneven fluxes of different legs and magnetic core selection criteria and optimizations. We use a flowchart to design the coupled inductor, and constructed a 400-W prototype by following it. We present some comparisons between our method and those presented in the literature. Simulation and experimental results demonstrate that our method is effective and straightforward. [ABSTRACT FROM AUTHOR]

The design of high-frequency power converter is very difficult because the leakage inductance of the transformer affects the performance. With consideration of the high-frequency eddy current, the flux linkage due to the eddy-current reaction field using a proposed summation calculation method is computed. The leakage inductance of a high-frequency transformer is therefore characterized. An optimum design method of the transformer can be obtained. Experimental results confirm the affectivity of the calculation method. [ABSTRACT FROM AUTHOR]

Discusses the problems experienced in estimating the actual current distribution among various silicon controlled rectifier switches in a converter at the University of Texas at Austin Center for Electromechanics. Importance of multiple switching devices in power converters; Results of the electromagnetic finite-element analysis of one leg of the converter; Role of differential reactance in determining the magnitude of the overload.

A model of magnetic components is presented which includes saturation and static hysteresis and covers a wide frequency range. A dedicated setup measures the B–H curves for extraction of the model parameters and for model validation. The magnetic model is then represented as a spice circuit and is used in transient system simulations of power converters. Simulations and measurements of core losses and the filter performance of common mode chokes are discussed. [ABSTRACT FROM AUTHOR]

We report theoretically and experimentally a passive bidirectional current–voltage ( $I$ – $V$ ) converter, capable of converting input currents into output voltages, and conversely, input voltages into output currents, based on a multiphase heterostructured magnetoelectric (ME) ring. The ME ring has a coil-wound, intermagnetically biased magnetostrictive–piezoelectric (MS–PE) heterostructure, in which an axially polarized PZT PE ceramic ring is bonded between two circumferentially magnetized, intermagnetically biased Terfenol-D short-fiber/NdFeB magnet/epoxy three-phase MS composite rings. In $I$ – $V$ conversion, a current applied to the coil induces a vortex magnetic field to the ME ring, resulting in an open-circuit voltage from the ME ring because of the direct ME effect. In voltage–current ( $V$ – $I$ ) conversion, a voltage applied to the ME ring produces a circumferential magnetic induction due to the converse ME effect, leading to a short-circuit current from the coil. The converter exhibits simultaneously large $I$ – $V$ and $V$ – $I$ conversion factors of $\sim 0.3$ V/A and $\sim 0.2$ mA/V in a broad non-resonance frequency range up to 80 kHz as well as enhanced conversion factors of $\sim 7$ and $\sim 25$ times at the resonance frequency of 122 kHz, respectively. [ABSTRACT FROM PUBLISHER]

An array of ferrite and air-core inductors was fabricated on silicon wafer to characterize inductor performance. The 1 \mu\m and 2.5 \mu\m thick ferrite films for the fabrication of inductors were prepared by dc magnetron sputtering. The inductance of the ferrite inductor increased with the thickness of ferrite film from 45.5 nH for 1 \mu\m thick ferrite to 50 nH for 2.5 \mu\m thick ferrite. The maximum Q-factor was obtained to be 59 at 2.87 MHz from 2.5 \mu\m thick ferrite inductor, which is higher than 49.3 at 2.26 MHz for 1 \mu\m thick ferrite inductor and 23.2 at 1.56 MHz for air-core inductor. Superimposed dc current of 1 \mu\m and 2.5 \mu\m thick ferrite inductors was estimated to be 2.5 A and 2.15 A, respectively, corresponding to a 5% drop in L at 10 MHz. In addition, the power efficiency of the buck dc-dc converter based on the studied ferrite inductors was calculated to be 91.7% for 2.5 \mu\m thick ferrite inductor and 90.1% for 1 \mu\m thick ferrite inductor at load current of 0.647 A. [ABSTRACT FROM AUTHOR]

Examines the influence of silicon-controlled rectifier (SCR) turn-off characteristics on the design of equalizer circuits. Impact of the variability of capacitance value on snubber circuit; Important characteristics of single devices in power converters; Role of auxiliary circuits in protecting SCR.

Discusses the electrical performance and miniaturization potential of two standalone trigger circuit. Analysis of the ability of snubber circuit to protect silicon controlled rectifiers (SCR); Functions of the snubber circuit; Effect of SCR protective circuits on the size of the converter.