Trapezoidal Waveform Research Articles

Analysis and Optimization of Power MOSFETs Shaped Switching Transients for Reduced EMI Generation

The abrupt change in current or voltage caused by the rapid switching action of power semiconductor devices will generate high-frequency electromagnetic interference (EMI) and needs to be located as the primary interference sources in power electronics. This paper deals with interference suppression on the basis of the study of shaped switching transients in switching waveforms and closed-loop gate drive method for power MOSFETs. The characteristics of switching waveforms with arbitrary switching transients are investigated in both time- and frequency-domain. In addition, conditions of constructing a switching waveform with optimized switching transients are put forward. An optimized Gaussian switching waveform with infinite successive derivatives is proposed which provides the deepest decreasing rate in the interference source spectrum for a given switching time. Compared with a trapezoidal waveform with single-slope transients, the proposed switching waveform has better interference suppression at high frequencies. Meanwhile, a closed-loop gate control prototype with on-state resistance compensation is presented to shape the switching transients of power MOSFETs. The simulated and experimental results show that the proposed controller is successfully implemented to shape the drain–source voltage into an optimized Gaussian reference. Spectrum comparisons show that the EMI generation is effectively suppressed as expected.

Effects of the driving voltage waveform on the performance of the Stirling-type pulse tube cryocooler driven by the moving-coil linear compressor

The effects of three typical waveforms, namely, sine, trapezoid and smeared sine, on the performance of the Stirling-type pulse tube cryocooler (SPTC) driven by the moving-coil linear compressor are analyzed and studied experimentally. The results indicate that the dynamic pressure at the inlet of the cold finger has a weak relation with the driving voltage waveform, but the latter plays an important role in affecting both the motor efficiency and the SPTC cooling performance. In the tested range, either the cooling efficiency or the motor efficiency under the smeared sine waveform is the highest, while that under the sine waveform is the lowest. Moreover, given that the input power is below 30 W, the motor efficiencies under both smeared sine and trapezoid waveforms exceed 90%, which suggests a promising approach to achieve a linear compressor with a very high motor efficiency by optimizing the voltage waveform.

Extending Geobandwidth using the Multipulse Configuration

Measurement bandwidth is an important feature of a geophysical system. Bandwidth allows detection of very resistive features (such as some kimberlites) and very conductive targets (like massive sulphides). In electromagnetic systems, bandwidth is not simply the sample rate of the data acquisition system or the earliest time channel, but also depends on transmitter spectrum, distance to target and processing. Optimising a system to detect a feature or measure a specific signal requires design considerations and trade-offs for different targets. The choice of excitation waveform in electromagnetic systems is one such trade-off. A square-pulse allows high-frequency energy to be excited, but, because of electronic limitations, has only limited dipole moment. A half-sine waveform efficiently generates energy at the base frequency and first few odd harmonics (low-frequency energy) and less high-frequency energy. Here, we describe the Multipulse configuration, an option on the Helitem system which employs both a half-sine and a trapezoid waveform to efficiently generate high- and low-frequency energy. Using survey data, we show the resolution power of the combined system compared to a single waveform. The combined data is better able to resolve near-surface features and deep structure than data from either waveform alone.

Influence of frequency and wave form on S-N fatigue of commercial austenitic stainless steels with different nickel contents in inert gas and in high pressure gaseous hydrogen

The main part of this investigation are S-N fatigue tests of austenitic stainless steels with different nickel contents (12.6–13.7wt%) in high pressure gaseous helium and hydrogen at −50°C to characterize the influence of hydrogen on the S-N curve. For the steel with 12.6wt% Ni the low cycle fatigue life in hydrogen was about one order of magnitude lower compared to helium. The slopes of the two curves were comparable. The influence of hydrogen decreased with increasing nickel content, which is consistent with tensile test results. The S-N results in He were significantly influenced by the test frequency. Number of cycles to failure decreased with decreasing frequency until saturation at around 0.1Hz. Hydrogen effects were predominant down to a frequency of about 1Hz. Below 1Hz, the decrease in numbers of cycles to failure was dominated by the frequency effect and not by the hydrogen effect. An increased effect of hydrogen for a trapezoid wave form compared to a triangle wave form could not be identified.

Linear ion trap mass selectivity with impulse power supply and sinusoidal dipolar excitation.

An ion trap mass analyzer can be operated by either a sinusoidal waveform power supply or an impulse waveform power supply. The optimal conditions for the performance of ion trap which is driven by an impulse waveform power supply with sinusoidal dipolar voltage were investigated theoretically, and further verified by experiments. The analytical relationship between β and q values is derived theoretically for optimal performance, and the dependencies β(q) for different trapezoidal waveforms are studied. To explain the dependence of resolution with working point q, the derivative dβ/dq is also derived analytically for the case of a rectangular waveform power supply. The theoretical results are further verified by experiments. The results from both theoretical calculations and experiments are in very good agreement. The behaviour resolution with q is controlled by the dispersion dβ/dq that was also confirmed by experiments, when the resolution increases with q. The optimal conditions of β, qex values and required excitation time n are when S(q) is close to 1 for an ion trap driven by trapezoidal waveform voltage with sinusoidal dipolar voltage. It shown that with increasing impulse parameter τ the dispersion dβ/dq decreases and the mass resolution also decreases as result. In the case of applying a rectangular waveform shape voltage, the mass selectivity is the same as for the sinusoidal wave shape. Copyright © 2016 John Wiley & Sons, Ltd.

A Quasi-Switched-Capacitor Resonant Converter

A quasi-switched-capacitor (QSC) resonant converter is proposed for isolated dc/dc conversion in offline power supply application. Similar to the Φ2 resonant converter, the proposed converter is operated most efficiently at fixed switching frequency and duty ratio, and it features trapezoidal voltage waveforms on all switches. Full soft switching combining ZCS, ZVS on and off is achieved within a wide load range, and, therefore, the switching loss is minimized. In addition, compared to half/full-bridge converters (e.g., the LLC resonant converter and the dual-active-bridge converter), the proposed converter reduces the voltage stress on primary-side switches to 2/3 of the input voltage, and, thus, enables more choices of low-voltage devices, which are more efficient because of better figure of merit. Furthermore, the proposed converter reduces the transformer turns ratio by 2/3, and, thus, enables less number of turns of the winding, lower winding loss, and lower transformer leakage inductance, making it suitable for high-frequency operation. A 90-W 88-V/19-V 700-kHz prototype is built with 100-V eGaN FETs. The transformer design and PCB layout are presented to minimize the transformer leakage inductance and stray inductance. The prototype achieved a power density of 172 W/in3, and a flat efficiency curve with a peak value of 96%.

Instrument current transducer for measurements in asymmetrical conditions in three-phase circuits with upper harmonics

The theme of the article is protection of electrical circuits against negative sequence currents both with sinusoidal and trapezoidal waveforms. The suggested solution is enhancement of instrument current transducers used in industrial relaying and control applications. The instrument negative sequence current transducer connected to Rogowski coils designed by the authors is presented in the article. To protect circuits with extremely non-sinusoidal currents (such as trapezoidal waveforms), instrument transducers with 2nd order low pass filter are suggested. In the presence of higher-order harmonics in the protected three-phase circuit the low pass filter will reduce the THD in the output voltage of instrument negative sequence current transducer (as compared to harmonics in currents of the protected circuit) and compensate for the differentiation effect typical of such transducer schemes.The paper may be of interest for investigators and engineers engaged in research, design and commissioning of protection and control equipment, current instrument and measurement devices used in industrial applications, and also for undergraduate and postgraduate students in electrical engineering.

Influence of Confinement Pressure on the Development of Three Stage Curve for Bituminous Mixtures

As part of the mechanistic-empirical pavement design procedure, the flow number test is used to rank the bituminous mixtures for rutting. In the flow number test, a sample is subjected to 0.1 s of loading followed by 0.9 s rest period and a haversine load waveform is used. This test protocol has serious limitation and these are due to the loading conditions applied and the post-processing procedure followed for flow number determination. In this investigation, three changes were made in the existing flow number protocol. The first one was in the load waveform. A trapezoidal waveform was used instead of the haversine load waveform. The second change was related to loading conditions. Different combinations of confinement and deviatoric loading were applied and the final choice was made based on the resulting three stage creep curve. The third change was related to post-processing method and a Francken model to capture the complete three stages of deformation was used. A BC mix with mid-gradation following MoRTH (Specifications for roads and bridge works. Indian Roads Congress, New Delhi 2013) guidelines was used with VG30 and CRMB60 binder. PReSBOX shear compactor was used for making cylindrical samples of 94 mm diameter and 150 mm height. The samples were cast with a target air voids of 6 %. All the testing was carried out at 50 and 60 °C. Different confinement conditions ranging from 50 to 200 kPa were used with the deviatoric loading ranging from 200 to 600 kPa. The influence of modified binder was clearly seen in the development of three stage curve. The collected data was post-processed using Francken model and the flow number was determined. This flow number was bench marked with the existing flow number protocol and it was seen that there were gross discrepancies.

Design and analysis of a single-phase low-frequency active power factor correction circuit: a symmetric trapezoidal current waveform approach

This paper focuses on the design and analysis of the single-phase Low-Frequency Active Power Factor Correction (LFAPFC) circuit. The LFAPFC circuit has several attractive features such as low electromagnetic interference, low switching frequency and ease of implementation when compared with the High-Frequency Active Power Factor Correction circuit. Moreover, its performance is much better than that of the Passive Power Factor Correction circuit. However, few of the previous studies focus on determining the values of major parameters of the LFAPFC circuit and their corresponding performance. To conduct an in-depth study on the LFAPFC circuit, this paper proposes a systematic design method based on analyzing the characteristics of a symmetric trapezoidal current waveform. Using the proposed method, output performance indices such as total harmonics distortion and power factor of the LFAPFC circuit can be estimated. In addition, the relationship among the output performance, inductance and conduction parameters of the power switch is derived and investigated. Using the proposed method, designers can determine suitable values of conduction parameters and inductance for specific applications. Computer simulations and real experiments are carried out to verify the effectiveness of the proposed method.

Comparison of different pressure waveforms for heat transfer performance of oscillating flow in a circular cylinder

In the present investigation, an oscillating motion of unsteady Burger's fluid in a circular cylinder was modeled with different pressure waveforms. Three different waveforms are considered: the case of a trapezoidal, triangular and sinusoidal waveform. Analytical solutions of velocity and temperature distribution are obtained for an oscillating laminar flow, which can be used to analyze the effects of flow type on the heat transfer performance. The limiting cases have been considered to examine the heat transfer performance of four different non-Newtonian fluids. Results show that the heat transfer of the oscillating flow depends on the fluid material parameter, Prandtl number, amplitude oscillating waveform and radial coordinate. The trapezoidal and sinusoidal waveforms of oscillating motion can result in a higher heat transfer performance.

Crack Growth Resistance Characteristics Determination Algorithm for Creep-fatigue Interaction

A creep-fatigue crack growth rate interpretation method and algorithm and test results are described. The algorithm allows to obtain a crack growth rate diagram in terms of creep stress intensity factor. The proposed algorithm is realized on steel compact tension specimens (12Х1MF).Crack growth rate was determined on standard compact specimens under temperature 550°C. The waveforms for the loading and unloading portions were trapezoidal, and the loading/unloading times were held constant – 5 s. A hold time of predetermined duration, 60 s, was superimposed on the trapezoidal waveforms at maximum load. The potential drop and the unloading compliance methods were used to monitor crack length during the creep–fatigue tests.For the experimental crack paths in tested specimens the governing parameter for the 3D-fields of the stresses and strains at the crack tip in the form of In-integral was calculated by finite element analysis along crack front. The governing parameter of the stress-strain fields in form of In-integral was used as the foundation of the creep stress intensity factor. The creep stress intensity factor approach was applied to the fatigue crack growth. The numerical and experimental results demonstrated that Kcr is the most effective crack tip parameter in correlating the creep–fatigue crack growth rates in power plant materials and can be used reliably for practical purposes.

Comparison of fatigue crack propagation in nickel base superalloys RR1000 and Udimet 720Li

The effects of temperature, dwell and environment on the fatigue crack growth behaviour of two nickel base turbine disc superalloys RR1000 and Udimet 720Li are presented in the present paper. Fatigue tests were carried out at room temperature in air using a 20 Hz sinusoidal loading waveform and at elevated temperatures of 650 and 725°C in both air and vacuum environments using a trapezoidal loading waveform with dwell times at a maximum load of 1 or 20 s. The fatigue crack propagation resistance of both materials is rationalised in terms of the influence of microstructure as well as the effects of alloy chemistry.

Electrical characterization and modeling of pulse-based forming techniques in RRAM arrays

The forming process, which corresponds to the activation of the switching filament in Resistive Random Access Memory (RRAM) arrays, has a strong impact on the cells’ performances. In this paper we characterize and compare different pulse forming techniques in terms of forming time, yield and cell-to-cell variability on 4kbits RRAM arrays. Moreover, post-forming modeling during Reset operation of correctly working and over formed cells has been performed. An incremental form and verify technique, based on a sequence of trapezoidal waveforms with increasing voltages followed by a verify operation that terminates when the expected switching behavior has been achieved, showed the best results. This procedure narrows the post-forming current distribution whereas reducing the Reset switching voltage and the operative current. These advantages materialize in a better control of the cell-to-cell variability and in an overall time and energy saving at the system level.

Analysis and Design of a Modular Multilevel Converter With Trapezoidal Modulation for Medium and High Voltage DC-DC Transformers

Conventional dual-active bridge topologies provide galvanic isolation and soft-switching over a reasonable operating range without dedicated resonant circuits. However, scaling the two-level dual-active bridge to higher dc voltage levels is impeded by several challenges among which the high dv/dt stress on the coupling transformer insulation. Gating and thermal characteristics of series switch arrays add to the limitations. To avoid the use of standard bulky modular multilevel bridges, this paper analyzes an alternative modulation technique, where staircase approximated trapezoidal voltage waveforms are produced; thus, alleviating developed dv/dt stresses. Modular design is realized by the utilization of half-bridge chopper cells. This way the analyzed dc-dc transformer employs modular multilevel converters operated in a new mode with minimal common-mode arm currents, as well as reduced capacitor size, hence reduced cell footprint. Suitable switching patterns are developed and various design and operation aspects are studied. Soft-switching characteristics will be shown to be comparable to those of the two-level dual-active bridge. Experimental results from a scaled test rig validate the presented concept.

Effect of mean stress on multiaxial ratcheting life: A simplified life prediction model based on average equivalent stress amplitude

This article proposes a model to predict uniaxial and multiaxial ratcheting life by addressing the three primary parameters that influence failure life: fatigue damage, ratcheting damage and the multiaxial loading path. These three factors are addressed in the present model by (a) the stress amplitude for fatigue damage, (b) mean stress-dependent Goodman equation for ratcheting damage and (c) an inherent weight factor based on average equivalent stress to account for the multiaxial loading. The proposed model requires only two material constants which can be easily determined from uniaxial symmetric stress-controlled fatigue tests. Experimental ratcheting life data collected from the literature for 1025 and 42CrMo steel under multiaxial proportional and nonproportional constant amplitude loading ratcheting with triangular sinusoidal and trapezoidal waveform (i.e. linear, rhombic, circular, elliptical and square stress paths) have shown good agreement with the proposed model.

PGSE, OGSE, and sensitivity to axon diameter in diffusion MRI: Insight from a simulation study.

PurposeTo identify optimal pulsed gradient spin‐echo (PGSE) and oscillating gradient spin‐echo (OGSE) sequence settings for maximizing sensitivity to axon diameter in idealized and practical conditions.MethodsSimulations on a simple two‐compartment white matter model (with nonpermeable cylinders) are used to investigate a wide space of clinically plausible PGSE and OGSE sequence parameters with trapezoidal diffusion gradient waveforms. Signal sensitivity is measured as a derivative of the signal with respect to axon diameter. Models of parallel and dispersed fibers are investigated separately to represent idealized and practical conditions.ResultsSimulations show that, for the simple case of gradients perfectly perpendicular to straight parallel fibers, PGSE always gives maximum sensitivity. However, in real‐world scenarios where fibers have unknown and dispersed orientation, low‐frequency OGSE provides higher sensitivity. Maximum sensitivity results show that on current clinical scanners (G max = 60 mT/m, signal to noise ratio (SNR) = 20) axon diameters below 6 µm are indistinguishable from zero. Scanners with stronger gradient systems such as the Massachusetts General Hospital (MGH) Connectom scanner (G max = 300 mT/m) can extend this sensitivity limit down to 2–3 µm, probing a much greater proportion of the underlying axon diameter distribution.ConclusionLow‐frequency OGSE provides additional sensitivity to PGSE in practical situations. OGSE is particularly advantageous for systems with high performance gradients. Magn Reson Med 75:688–700, 2016. © 2015 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Influence of oxidation on fatigue crack initiation and propagation in turbine disc alloy N18

Fatigue crack initiation and propagation behaviour in subsolvus heat treated turbine disc alloy N18 has been assessed in air and vacuum at 650 and 725°C under three-point loading. Fatigue crack initiation processes have been evaluated using single edge U-notch specimens under a 1-1-1-1 trapezoidal loading waveform along with interrupted tests at 650°C to allow intermittent observations of the notch surface. The results show apparent grain boundary (GB) oxidation can occur under an oxygen partial pressure of 10−2–10−3Pa. Cracks mainly initiate from grain boundaries or γ/γ′ interfaces due to the formation and subsequent cracking of Cr-rich and/or Co-rich oxides, and occasionally initiate from surface pores. Fatigue life in these tests appears to be dominated by this crack initiation process and is significantly reduced by increasing temperature and/or application of an oxidizing environment. Crack growth tests conducted under 1-1-1-1 and 1-20-1-1 loading waveforms indicate that oxidation significantly degrades the crack growth resistance of N18 and is associated with more intergranular fracture surface features. Additional oxidation effects on propagation caused by higher temperature or prolonging dwell time appear limited, whereas a prolonged dwell period seems to instead promote additional creep process, which further enhance crack growth, especially at higher temperature.

Enhanced distinction of surface and cavity discharges by trapezoid-based arbitrary voltage waveforms

Identification of different partial discharge (PD) sources may be improved by the use of non-sinusoidal waveforms of the testing voltages. For instance, surface discharge (SD) and cavity discharge (CD) are not always easy to directly distinguish from the phase resolved PD pattern at traditional 50 or 60 Hz alternating sinusoidal voltage. This study compares PD patterns stimulated by sinusoidal voltage and by several forms of trapezoid-wave voltage, including the limiting cases of triangular and approximately square-wave voltages. Trapezoid-based voltage waveforms are considered as a potential new off-line diagnostic method for PD sources. Partial discharge measurements were performed with each different waveform in two test cells representing canonical cases of SD and CD, with polycarbonate plates as the solid insulating material. The results show that the applied voltage of arbitrary waveform could more clearly distinguish between these PD sources� behavior than normal sinusoidal voltage. The constant-voltage period of peak value in trapezoidal and square voltage waveforms played an important role in the distinction of the two discharge sources. Compared with the cavity discharge�s symmetric features, surface discharge produced in the asymmetric test cell shows strong asymmetric behavior during the constant-voltage period between two polarities under trapezoidal and square voltage waveforms. A faster rise time and increased duration of the constant peak-voltage part of the waveform caused more obvious asymmetry of the surface discharge.

Low Power Parallel Prefix Adder Design Using Two Phase Adiabatic Logic

In this paper low power implementation of parallel prefix adders using two phase adiabatic logic has been investigated. A new structure has been proposed for the main blocks of parallel prefix adder. Three parallel prefix adders including Kogge-Stone, Brent-Kung and Ripple Carry have been considered. The effects of power clock frequency and loading capacitance on the new blocks have also been considered. Simulation results using 180nm technology parameters and trapezoidal waveform show an average of 34% power reduction in the main building blocks of the adder at 200MHz clock frequency. This power reduces to 54% for sine wave power clock waveform. This research suggests adiabatic implementation of parallel prefix adders for low power microprocessor and signal processing applications.

Abstract 304: The Effects of Compression Waveforms on the Outcomes of Cardiopulmonary Resuscitation in a Porcine Model of Cardiac Arrest

Background: Previous studies have demonstrated that different mechanical compression waveforms yield different hemodynamic efficacy. In the present study, we investigated the effects of two different compression waveforms on the hemodynamics and defibrillation efficacy in a pig model of CPR. Methods: Ventricular fibrillation was electrically induced in ten male domestic pigs weighing between 35 - 40 kg and untreated for 7 mins. The animals were then randomized to receive chest compression with either trapezoidal (TW) or sinusoidal (SW) waveform. After a total 5 mins of CPR, defibrillation was attempted. ECG, aortic blood pressure (AP), right atrium blood pressure (RAP) and carotid blood flow (CBF) were continuously record and analyzed after the experiments were completed. Results: All animals were resuscitated. The total defibrillation attempts in the TW group were significantly fewer than the SW group (1.6±0.9 vs. 11±7.8, p=0.03) prior to successful resuscitation. Amplitude spectrum analysis (AMSA) and signal integral were significantly greater in each minute of CPR in the TW group when compared with the SW group (Figure 1). Significantly greater CPPs were observed in the TW group during the last 3 mins of CPR. Mean CBF showed no difference during CPR between the two groups, but the dynamic forward CBF in the first 4 mins of CPR was significantly greater in the TW group (Figure 2). Conclusions: Chest compression with trapezoidal waveform improved hemodynamics and defibrillation efficacy in the pig model of CPR. Compression waveform therefore became another important factor to be considered during mechanical chest compression.