Rectangular Excitation Research Articles

Analysis of Torque Characteristics of Parallel Hybrid Excitation Machine Drives With Sinusoidal and Rectangular Current Excitations

The parallel hybrid excitation machine (PHEM) consists of axial parallel permanent magnet machine part and doubly salient electromagnetic machine part. The three-phase armature windings of two parts are connected in series. Based on the waveforms of back electromotive force, both sinusoidal and rectangular current excitations can be adopted in PHEM. The torque characteristics of PHEM drives with ideal sinusoidal and ideal rectangular current excitations are analyzed. The average torque versus armature current in brushless ac (BLAC) and brushless dc drives are comparatively analyzed. Furthermore, the torque and torque ripple versus current angle in some typical armature currents are investigated. Moreover, the speed and torque waveforms are given under the vector control and the current pulsewidth modulation control scheme. Finally, the experimental data of the target PHEM agree well with the simulation results. It is shown that in BLAC drives, the PHEM exhibits higher torque density with lower torque ripple.

Studying the computational resource demands of mathematical models for moving surface eddy current probes for synthesis problems

Distribution of eddy current density for three types of coils of excitation of moving surface eddy current probes, in particular circular, rectangular, orthogonal-rectangular shapes was calculated according to the formulas of exact electrodynamic mathematical models with allowance for the speed effect. Calculation time from 8 to 20 hours was established for a circular excitation coil with dimensions of testing zone 50´50 mm at speed u x =40 m/s. The calculation time was from 8 to 9 hours for a rectangular excitation coil at a speed of movement in direction of two components u x , u y =20 m/s with the testing zone dimensions of 80´48 mm. The calculation time was more than 7 hours for an excitation coil of orthogonal rectangular shape with dimensions of the testing zone of 15´35 mm at a speed of movement in direction of components u x , u y =40 m/s; and for the testing zone dimensions of 12´24 mm for u x , u y =40 m/s it was longer than 9 hours. It was found that the computational complexity of calculation of distribution of the eddy current density with the use of exact mathematical models was rather large when changing even two spatial coordinates in the testing zone. That is, the direct use of exact mathematical models when calculating the values of distribution of the eddy currents density in the points of the controlled zone is inappropriate taking into account the considerable resource intensity of the computational process. The necessity for using a mathematical apparatus of surrogate optimization was substantiated for designing eddy current probes with a uniform distribution of eddy current density in the testing zone. This study is useful for non-destructive testing specialists in the field of mechanical engineering. The study results can be used in designing eddy current probes with improved metrological characteristics, in particular homogeneous sensitivity, localization of the probing excitation field, improved noise immunity, possibility of eliminating the edge effect manifestations in testing

Rise kinetics of up-conversion luminescence under pulsed excitation. Probabilistic model and experiment

A probabilistic model describing the luminescence kinetics in systems of interacting rare-earth ions is proposed. The basic position of the model is that any mechanism of energy transfer between ions can be represented as a sequence of elementary processes. The duration of each elementary process of energy transfer is a random variable. An analytical expression is found for the time dependence of the radiant flux spectral density of ions for any pump modulation and its special case when the durations of elementary processes have exponential distribution laws and the excitation modulation is a rectangular or short pulse. It is shown that the initial stage of this dependence is a power function. The process of energy transfer from the pump radiation to the emitting ion consists of a number of elementary successive stages which determine the exponent. Mechanisms of up-conversion energy transfer under pulsed excitation are considered in systems consisting of ions of two types: donors interacting with pump radiation and acceptors receiving energy from donors. The number of successive elementary processes, of which these mechanisms are composed, is determined. A regression analysis of the rise kinetics of up-conversion luminescence of the Y0.8Yb0.2F3: Tm3+(1 at%) crystal is made using the proposed probabilistic model. The kinetics was obtained under rectangular pulsed excitation by IR radiation of a λp=933nm semiconductor laser diode. The most important mechanisms of energy transfer from Yb3+ ions to the Tm3+ ions responsible for transitions between the ground 3H6 term and excited 3F4, 3H4, 1G4, 1D2, 1I6 terms of the Tm3+ ions are established. The durations of these energy transfer processes are determined.

Simultaneous size and geometry optimization of steel trusses under dynamic excitations

During the past decades, the main focus of the research in steel truss optimization has been tailored towards optimal design under static loading conditions and limited work has been devoted to investigating the optimum structural design considering dynamic excitations. This study addresses the simultaneous size and geometry optimization problem of steel truss structures subjected to dynamic excitations. Using the well-known big bang-big crunch algorithm, the minimum-weight design of steel trusses is conducted under both periodic and non-periodic excitations. In the case of periodic excitations, in order to examine the effect of the exciting period of the dynamic load on the final results, the design instances are optimized under different exciting periods and the obtained results are compared. It is observed that by increasing the excitation period of the considered sinusoidal loading as well as the finite rise time of the non-periodic step force, the optimization results approach the minimum design weight obtained under the static loading counterpart. However, in the case of the studied rectangular periodic excitation, the results obtained do not approach the optimum design associated with the static loading case even for higher values of the exciting period.

Recent development of reluctance machines with different winding configurations, excitation methods, and machine structures

This paper reviews the performances of some newly developed reluctance machines with different winding configurations, excitation methods, stator and rotor structures, and slot/pole number combinations. Both the double layer conventional (DLC-), double layer mutually-coupled (DLMC), single layer conventional (SLC-), and single layer mutuallycoupled (SLMC-), as well as fully-pitched (FP) winding configurations have been considered for both rectangular wave and sinewave excitations. Different conduction angles such as unipolar120o elec., unipolar/bipolar 180 oelec., bipolar 240 o elec. and bipolar 360oelec. have been adopted and the most appropriate conduction angles have been obtained for the SRMs with different winding configurations. In addition, with appropriate conduction angles, the 12-slot/14-pole SRMs with modular stator structure is found to produce similar average torque, but lower torque ripple and iron loss when compared to non-modular 12-slot/8-pole SRMs. With sinewave excitation, the doubly salient synchronous reluctance machines with the DLMC winding can produce the highest average torque at high currents and achieve the highest peak efficiency as well. In order to compare with the conventional synchronous reluctance machines (SynRMs) having flux barriers inside the rotor, the appropriate rotor topologies to obtain the maximum average torque have been investigated for different winding configurations and slot/pole number combinations. Furthermore, some prototypes have been built with different winding configurations, stator structures, and slot/pole combinations to validate the predictions.

Electromagnetic induction analysis of a rectangular differential excitation coil-based eddy current sensor

A differential excitation coil eddy current sensor based on a rectangular geometry is proposed and designed. The working principle of this sensor is analysed based on mathematical theory and the principle of electromagnetic induction. Analysis shows that, owing to the superposition effect, this sensor can induce higher magnetic flux density so that it can detect a stronger disturbance when it encounters defects in the conductor. The high sensitivity of the sensor is verified through experiments.

Core loss calculation for magnetic materials employed in SMPS under rectangular voltage excitations

Magnetic materials are widely used in switching-mode power supplies (SMPS) and magnetic components in SMPS usually work under two typical rectangular excitations (with or without the period of zero voltage). Extensive experimental results have shown that there is quite a difference of core loss between sinusoidal excitations and rectangular excitations, which means the traditional core loss calculation methods are no longer applicable. In this paper, two formulas for core loss calculation under the above rectangular excitations are derived based on the Improved Generalized Steinmetz Equation (IGSE). Core loss of different magnetic materials, under both sinusoidal excitations and rectangular excitations with different frequencies and duty cycles, are measured. Experimental results show that the formulas are accurate enough and very useful to predict the core loss.

Pulsed Eddy Current Nondestructive Testing for Defect Evaluation and Imaging of Automotive Lightweight Alloy Materials

Rapid and accurate damage detection of magnesium-aluminum alloy, which is an important material for automotive lightweight, is of great significance. Pulsed eddy current (PEC) is an effective electromagnetic nondestructive testing and evaluation (NDT&E) technique for metal materials. Metal loss evaluation and imaging are one of the most important steps in quality control and maintenance of key components of automobiles. A PEC method based on a rectangular excitation coil and an axial parallel pickup coil is proposed and investigated for the purpose of metal loss evaluation and imaging. Metal loss type of defects with different sections is designed and detected using line scanning technique and C-scan imaging in two scanning directions. Experimental results have illustrated that metal loss depth can be estimated effectively by the peak amplitude of PEC A-scan response. Then, the quantification information of metal loss depth is preliminarily obtained based on the linear fitting equation. Consequently, metal loss evaluation is realized by line scanning peak waves and C-scan pseudo 3D images. At last, the sensitivity comparison shows that the metal loss can be detected in both directions. The proposed method is an effective approach to evaluate the image surface-breaking metal loss in automotive lightweight alloy materials.

Study of cumulative fatigue damage detection for used parts with nonlinear output frequency response functions based on NARMAX modelling

Cumulative fatigue damage detection for used parts plays a key role in the process of remanufacturing engineering and is related to the service safety of the remanufactured parts. In light of the nonlinear properties of used parts caused by cumulative fatigue damage, the based nonlinear output frequency response functions detection approach offers a breakthrough to solve this key problem. First, a modified PSO-adaptive lasso algorithm is introduced to improve the accuracy of the NARMAX model under impulse hammer excitation, and then, an effective new algorithm is derived to estimate the nonlinear output frequency response functions under rectangular pulse excitation, and a based nonlinear output frequency response functions index is introduced to detect the cumulative fatigue damage in used parts. Then, a novel damage detection approach that integrates the NARMAX model and the rectangular pulse is proposed for nonlinear output frequency response functions identification and cumulative fatigue damage detection of used parts. Finally, experimental studies of fatigued plate specimens and used connecting rod parts are conducted to verify the validity of the novel approach. The obtained results reveal that the new approach can detect cumulative fatigue damages of used parts effectively and efficiently and that the various values of the based nonlinear output frequency response functions index can be used to detect the different fatigue damages or working time. Since the proposed new approach can extract nonlinear properties of systems by only a single excitation of the inspected system, it shows great promise for use in remanufacturing engineering applications.

DYNAMIC ANALYSIS OF FIBER-REINFORCED POLYMER COMPOSITE ELECTRIC POLES

This paper presents finite element modeling of tapered fiber-reinforced polymer (FRP) poles in ABAQUS for dynamic analysis. Modal analysis and transient dynamic analysis are presented in order to evaluate the effect of fiber orientation, taper ratio, number of layers and lamina thickness on the dynamic properties of tapered poles. Trends observed from the parametric studies on the analyses of the FRP poles are enumerated. In addition, the effect of rectangular dynamic excitations on the overall response of the FRP poles is presented encapsulating impulsive loadings that may occur due to wind gusts or loss of cable tension supported by the FRP poles. Result shows that the fundamental frequency of the poles decreased as the fiber-orientation increased up to 60 degrees. In addition, the fundamental frequency of the poles increased as the number of layers increased. No significant difference was observed in natural frequency of the poles when varying the lamina thickness without changing the overall laminate thickness. The fundamental frequency of the FRP poles decreased by 10% as the taper ratio increased from 0.4 to 1. Transient dynamic analysis showed that FRP poles with higher fiber orientation angle had the larger maximum tip deflection. However, only small differences were observed when the deflections are normalized as the ratio of the maximum dynamic deformation to the maximum static deformation.

Predicting Core Losses Under the DC Bias Based on the Separation Model

Magnetic components in switched-mode power converters usually work under the rectangular voltage excitations with a dc premagnetization; the nonlinear changing characteristics of core losses in the magnetic components are hard to predict. In this paper, the method for predicting core losses in power inductors is introduced. A simplified hysteresis loss model is proposed to explain the well-known empirical characteristics of the hysteresis loss. If the working conditions of the dc bias and flux density are the same, hysteresis losses will keep constant independent with the exciting voltage waveforms, and the values of eddy-current losses will also have the constant mathematics relationships between nonsinusoidal voltage excitations and sinusoidal voltage excitations. The proposed method is very practical since it only takes core loss data under the sinusoidal voltage excitations as inputs rather than relies on any material parameters. Core losses under the different duty cycles and premagnetization levels have been tested; the experimental results verify the correctness of the proposed model.

Design of Inductors With Significant AC Flux

A design methodology is introduced to select a minimum core volume for an inductor or coupled inductors experiencing appreciable core loss. The geometric constant ( K gac) has been found to be a power function of the core volume for commercial toroidal, ER, and PQ cores, permitting the total loss to be expressed as a direct function of the core volume. The inductor is designed to meet specific loss or thermal constraints. An iterative procedure is described in which 2-D or 3-D proximity effects are first neglected and then subsequently incorporated via finite-element simulation. The methodology is demonstrated for coupled inductors in a 5-MHz converter in critical conduction mode. The core loss is verified using rectangular excitation and the winding loss is inferred from thermal measurements.

An Investigation of Ferrite and Nanocrystalline Core Materials for Medium-Frequency Power Transformers

In this study, two transformers are designed using the ferrite N87 and the nanocrystalline core materials for the same power level and operating frequency. The operating frequency is defined as 10 kHz, which is suitable␣for both materials. Modeling and simulation studies have been performed with the same finite element analysis software and the obtained results have been reported. The nanocrystalline and the ferrite N87 core materials have been compared according to both electrical and mechanical parameters. In these comparisons, many features such as core and winding losses, flux distributions, leakage flux, efficiency, and both electrical and mechanical performance have been reported comparatively in the case of rectangular waveform excitation of the transformer. Obtained results show that the weight and the volume of the transformer are reduced and more compact transformer is designed by using the nanocrystalline core material. In addition, besides the core loss, winding losses are also reduced in this design.

EXPERIMENTAL AND THEORETICAL STUDYING OF PHOTOCONDUCTIVITY OF POLYMERIC LAYERS WITH DYES

We present the results of the experimental and theoretical studying photoconductivity of polymer layers with the dyes. It’s investigated photoconductivity of organic dyes in solid polymeric matrices with rectangular pulse excitation light. The obtained experimental data indicate on the quadratic (i.e. non-linear) relationship between photocurrent values that are obtained for two different levels of radiation intensities.

A FPGA-Based Broadband EIT System for Complex Bioimpedance Measurements—Design and Performance Estimation

Electrical impedance tomography (EIT) is an imaging method that is able to estimate the electrical conductivity distribution of living tissue. This work presents a field programmable gate array (FPGA)-based multi-frequency EIT system for complex, time-resolved bioimpedance measurements. The system has the capability to work with measurement setups with up to 16 current electrodes and 16 voltage electrodes. The excitation current has a range of about 10 µA to 5 mA, whereas the sinusoidal signal used for excitation can have a frequency of up to 500 kHz. Additionally, the usage of a chirp or rectangular signal excitation is possible. Furthermore, the described system has a sample rate of up to 3480 impedance spectra per second (ISPS). The performance of the EIT system is demonstrated with a resistor-based phantom and tank phantoms. Additionally, first measurements taken from the human thorax during a breathing cycle are presented.

Laser-like effects and upconversion fluorescence temporal dynamic in Tm3+, Yb3+ doped YF3 single crystals

A new way of managing fluorescence features in doped bulk and nanosized materials by variation of excitation temporal characteristics is demonstrated. Random laser-like effect on 3H4-3F4 transitions of Tm3+ ions in Yb,Tm:YF3 single crystal was revealed under rectangular pulse train excitation in 930-980 spectral domain.

Influence of the optical pulse length on the amplitude and phase of photoinduced coherent phonons

The theoretical dependence of the amplitude and initial phase of photoinduced coherent vibrations of the crystal lattice on the length of a rectangular excitation optical pulse has been derived. Comparison with the experiment for tellurium has been carried out.

Numerical studies on sloshing in rectangular tanks using a tree-based adaptive solver and experimental validation

As liquid cargo transport developing, hull structural stability and strength are highlighted in various engineering areas due to tanks partially filled with fluid. Sloshing may be accounted as unpredictable force imposed on the whole faces of the tank walls. Water movement in rectangular tanks, under rolling and horizontal excitations, is investigated by numerical and experimental approaches. A parallel code, which directly discretizes the incompressible Navier–Stokes equations, coupled with VOF and tree-based adaptive algorithm, is employed to simulate the behavior of 2D fluid motion. A series of experiments are carried out to measure the pressures on the tank walls and under the water. A good agreement is shown in this paper and the values obtained by computations are validated. Through this, some studies are done on the basis of different excitation frequencies and filled levels.

Analysis of the induced photothermal conduction in the Mn4Si7-Si〈Mn〉-Mn4Si7 and Mn4Si7-Si〈Mn〉-M heterojunctions

The kinetics of photocurrent is studied in the presence of the intrinsic irradiation at hν ≥ 1.12 eV in the Mn4Si7-Si〈Mn〉-Mn4Si7 and Mn4Si7-Si〈Mn〉-M heterojunctions at relatively high applied voltages. It is demonstrated that photocurrent, scattered power, and temperature at the reverse-biased contact of the heterojunction depend on time at dc applied voltage, low temperature, and irradiation at hν ≥ 1.12 eV. The analysis of the temperature dependences of the photocurrent growth with time is used to demonstrate that the photocurrent pulses consist of two fragments: the first one corresponds to a slowly increasing relatively low current with a slope of (2–4) × 10−4 A/s and the second fragment is characterized by a sharp increase in the current with a slope of 0.1–1.0 A/s. Based on the slopes, the heating rates (β1 = 42 deg/s and β2 = 3 × 103 deg/s) and temperature gradients across the transient layer that corresponds to the Mn4Si7-Si〈Mn〉 interface (ΔT/Δx = 6.3 × 106 K/cm for β1 = 42 deg/s and ΔT/Δx ≥ 1.5 × 108 K/cm for β2 = 3 × 103 deg/s) are estimated. It is demonstrated that the Joule self-heating allows relatively high heating rates in the reverse-biased contact of heterojunction, which provides rapid heating similar to the rectangular step excitation that is equivalent to the activation of the long-wavelength (extrinsic) irradiation.

Impedance as guidance for electrode placement in intraoperative monitoring of nerve fibers

Electrodes for intraoperative monitoring should be reliable and should not disturb the surgeon. Since any wiring could complicate the handling of other medical instruments, new developments of autonomic, wireless electrodes are preferred. This new generation of electrodes will not only stimulate the nerve, but will monitor the action potentials as well. A failure to read nerve potentials may be indicative not just of damaged nerves, but may also result from bad electrode-nerve contact. To resolve this, we have developed electrodes which are equipped with impedance measurement features, facilitating simple connectivity checks. Due to energy constraints, the system works in the time domain using a rectangular voltage wave excitation. The voltage at the electrode is sampled and transmitted via RF link to the host computer. The frequency range covered by the excitation and sampling is between 100 Hz and 50 kHz, which is sufficient not only for detecting contact failure, but also for detecting thick layers of connective tissue between the electrode and the nerve fibre. In either instance, the surgeon can be warned of a bad electrode placement.