Ripple Level Research Articles

Numerical determination of the threshold magnetic field in superconducting strips and coils triggering dynamic resistance

Abstract The threshold magnetic field is a key parameter for evaluating the current decay caused by dynamic resistance in superconducting windings and magnets. For a DC-carrying superconducting slab under an AC parallel magnetic field, the analytical theory clearly shows that there is only one electric central line (ECL) across the slab width at the onset of dynamic-resistance. However, threshold magnetic fields in superconducting strips and coils have not been fully investigated. Based onthe one-ECL criterion, this paper first presents a method for numerically determining the threshold magnetic field via the evolving internal magnetic field in superconducting strips and coils. By probing transient electromagnetic behaviours, interestingly, we found a distinctive feature of superconducting strips in which a wide region of zero electrical field is observed when dynamic resistance/loss initially occurs. With increasing magnetic fields, this region gradually shrinks and eventually become the ECL. More importantly, this numerical method can analyse the local threshold magnetic field in a targeted coil turn. The ability to quantify threshold magnetic field provides a clear guidance on the acceptable level of ripple and harmonic magnetic fields for coil windings in superconducting maglev trains and field windings of superconducting machines operating at persistent current mode.

Enhancing SRM Performance through Multi-Platform Optimization and FPGA-Based Real-Time Simulation

This paper proposes a multi-platform algorithm methodology in order to define firing angles of torque sharing functions (TSFs) for the indirect torque control of switched reluctance motors (SRM) through a hardware-in-the-loop (HIL) system. This proposal is used to achieve optimal levels of torque ripple and losses with accuracy and reliability, while taking advantage of real-time simulation. The analysis is performed assuming steady-state conditions of speed and torque reference for levels below the base speed, aiming to obtain firing angles ensuring optimal tracking performance. A novel methodology is proposed by using a grid search algorithm that handles the communication between Python, Code Composer, and the Typhoon HIL device. For that, an experimental data FPGA-based model with 500~ns of simulation time step is used to ensure highly accurate dynamic responses of current and electromagnetic torque. Moreover, controller-HIL (C-HIL) is used to have a safe and high fidelity testing environment, allowing rapid testing before transitioning to an experimental test bench. The simulation results are experimentally validated, demonstrating that the proposed strategy is effective and ensures optimal performance, taking into account peripheral systems of A/D, signal conditioning, PWM, and sensor emulation.

Ripple-induced neoclassical toroidal viscous torque in Augmented-First Plasma operation phase in ITER

Abstract A systematic calculation is performed on the ripple-induced neoclassical toroidal viscous (NTV) torque for new ITER scenarios designed for the Augmented-First Plasma (A-FP) operation phase with the full tungsten wall, where the plasma-wall gap is varied in view of mitigating the impact of tungsten wall-plasma interactions. The torque calculation includes drift kinetic response of the plasma thermal and energetic particles to the n = 18 (n is the toroidal harmonic number) ripple field. For the plasma scenario with ~45 cm plasma-wall gap at the outboard mid-plane and considering the corrected ripple level of 0.17% by the ferritic steel inserts, the computed net NTV torque acting on the plasma column is in the sub-Nm level. However, with decreasing the plasma-wall gap, the computed net NTV torque can reach a level comparable to that produced by the neutral-beam momentum injection in ITER. Ripple correction by ferritic inserts reduces the net torque by a factor of 3.3 for all the three A-FP scenarios considered. The n ω d = l ω b (with ω d and ω b being the toroidal precession and bounce frequencies of trapped particles, respectively, and l an integer number) type of resonance-enhancement of the NTV torque, due to thermal particles, is found to be weak in ITER despite high-n of 18. The same also holds for the ITER 10 MA steady state scenario from the D-T operation phase, where the aforementioned resonance associated with fusion-born alphas is also included. The ripple-induced NTV torque is well below that produced by the resonant magnetic perturbation applied for controlling the type-I edge-localized mode in ITER.

Lower boundary capacity estimations of frequency-selective communication channels with PAM-n-signals achievable using resolution time theory

The issue of ensuring high specific capacity of promising wire telecommunication systems is one of the key problems of the last decade. At the same time, despite the existing spectrally efficient modulation methods that are used in existing communication systems, the majority of leading researchers associate further solution of this issue with the transition to the mode of information transmission at a rate "Faster-than-Nyquist" rate (FTN), in which the information receiving about the channel symbol occurs with pronounced intersymbol interference. In turn, this causes difficulties in the practical implementation of the receiver when using optimal signal processing algorithms with nonpolynomial computational complexity, and in the case of suboptimal demodulation methods implementing various types of channel equalization, due to conceptual limitations cannot provide a wide coverage of speeds in this mode. In this regard, the study of an alternative approach to processing signals with multi-position PAM-n-signals on the output of baseband frequency-selective channels (FSC) is relevant. The object of this paper is the study of the possibilities offered by the theory of resolution time for baseband FSC of the, in which information is transmitted using the PAM-n-signal, in the FTN mode. A modified mathematical model of FSC is presented, thanks to which analytical expressions are obtained for estimating the specific capacity in terms of the low bound capacity estimation introduced by Sh. Shamai, expressions for estimating the BER, including the case under the action of destabilizing factors on the symbol synchronization system. Auxiliary capacity estimations and rules for calculating the conditions for achieving them are introduced, convenient for engineering analysis. By means of numerical simulating for the most typical conditions inherent in wired FSC, which are modeled in this work by Chebyshev filters with ripple level of 3 dB and Butterworth filters, it is shown that in the FSN mode with a S/N ratio of no more than 40 dB and instability of the symbol synchronization system operation of 2.5% of the channel symbol duration with a bit error probability of 10–12, it is possible to expect a specific capacity of 5.7–8 bits/Hz*s. It is shown that these results are achieved by using hybrid forms of partial pulses. Recommendations for choosing a partial pulse shape are presented, their main properties are studied from the point of view of their engineering application.

Control Strategies of Thrust Ripple Suppression for Electromagnetic Microgravity Facility

This paper presents an innovative solution that is able to suppress the thrust ripple in a high-power asynchronous linear induction motor (LIM) used in a microgravity experiment facility electromagnetic launch (MEFEL) system. By addressing the crucial need for low levels of thrust ripple in MEFEL applications, we propose a dynamic model-based adaptive controller (MAC) and an enhanced quasi-proportional-resonant (PR) controller. The MAC is designed to compensate for the inherent impedance asymmetry of the linear motor. The PR controller minimizes thrust ripple by eliminating harmonics within the current loop. A comparative analysis indicates that both MAC and PR control are effective in reducing harmonics, suppressing the thrust ripple, and maintaining system stability. Computer simulations show a noteworthy 75% reduction in the thrust ripple and a decrease in the negative current. Partial tests on the MEFEL device validate the practical efficacy of the proposed control methods, emphasizing the method’s ability to enhance the quality of microgravity in real-world scenarios significantly.

DC/DC converter to power spectral lamps

Objectives. The paper describes the creation of a DC/DC converter for powering hollow cathode lamps widely used currently as highly stable sources of spectral lines in spectral absorption analyzers and other applications. Typically, mains power supplies are used for such lamps, since installations using hollow cathode lamps are manufactured as stationary. However, there are no principal obstacles to manufacturing portable versions by simply substituting the power supply. However, special attention should in this case be paid to the power supply of the spectral lamp itself, since the amplitude stability of the radiation depends on the smoothness of its supply voltage. Therefore, the development of the pulse DC/DC converter with high efficiency and low rippling is a relevant and expedient problem.Methods. The set task is solved by methods of mathematical calculations, circuit simulation in LTSpice XVII сomputer-aided design system, and experimental verification.Results. The structural and principal electrical circuit of a prototype converter is developed on the basis of a topological analysis of pulse DC/DC converters, along with its calculations and simulation, and a printed circuit board. The developed autonomous high-voltage DC/DC converter has a low ripple level (~250 mV) of the output voltage (~491 V) at a load current of ~20 mA to ensure highly stable radiation.Conclusions. The possibility of obtaining a high voltage when using the topology of a step-up DC/DC converter with a choke is demonstrated. The experimental verification confirmed the correctness of calculations and modeling of a high-voltage DC/DC converter for powering hollow cathode spectral lamps.

Flow Ripple Reduction in Reciprocating Pumps by Multi-Phase Rectification.

Reciprocating piezoelectric micropumps enable miniaturization in microfluidics for lab-on-a-chip applications such as organs-on-chips (OoC). However, achieving a steady flow when using these micropumps is a significant challenge because of flow ripples in the displaced liquid, especially at low frequencies or low flow rates (<50 µL/min). Although dampers are widely used for reducing ripples in a flow, their efficiency depends on the driving frequency of the pump. Here, we investigated multi-phase rectification as an approach to minimize ripples at low flow rates by connecting piezoelectric micropumps in parallel. The efficiency in ripple reduction was evaluated with an increasing number (n) of pumps connected in parallel, each actuated by an alternating voltage waveform with a phase difference of 2π/n (called multi-phase rectification) at a chosen frequency. We introduce a fluidic ripple factor (RFfl.), which is the ratio of the root mean square (RMS) value of the fluctuations present in the rectified output to the average fluctuation-free value of the discharge flow, as a metric to express the quality of the flow. The fluidic ripple factor was reduced by more than 90% by using three-phase rectification when compared to one-phase rectification in the 2-60 μL/min flow rate range. Analytical equations to estimate the fluidic ripple factor for a chosen number of pumps connected in parallel are presented, and we experimentally confirmed up to four pumps. The analysis shown can be used to design a frequency-independent multi-phase fluid rectifier to the desired ripple level in a flow for reciprocating pumps.

Focal Plane Array-Fed Shaped-Beam Transmitarray With Small-Gain Ripple and Low Sidelobe Level

A novel shaped-beam transmitarray antenna fed by a focal plane array is proposed. It features the small gain ripple and low sidelobe level. Unlike the traditional shaped-beam transmitarray designed by phase only optimization, the proposed one is put forward based on the superposition principle. An array is used as the feed. When the feed elements are excited, orthogonal beams pointing at different angles are generated. Then the expected beam can be shaped by adding up these orthogonal beams with appropriate weights. Specifically, the selection criteria for the number, the angles and the weights of these orthogonal beams are provided. Several squared-flattop beams and a flattop-cosecant squared beam are designed for validation.

Comparison of the input filter effect to PV panel by SEPIC MPPT converter

PV panel with front end converter for MPPT purpose is always employed for solar energy. The current that front end converter draws from PV panel are generally includes ripple regarding to operation mode of the converter and the type of converter. Such current ripple when it has higher magnitude is so harmful for the PV panel, it either shortened lifetime or results faults on PV panel. To overcome such drawbacks, input filter must be used with front end converter for PV panel connection. Although, in the literature, there are a few types of input filter, the effect of the filter and input current ripple and current noises are not compared for PV panel integration. The original contribution of the study is the analysis of input filter types for PV panel integration. As an input filter, LCL, LCL with damping, LC, C filters are used, and their effects are compared for PV panel. In addition, as a front-end converter SEPIC converter is chosen because of having lower or higher output voltage regarding to input voltage. Besides, using LCL based filters as input filters of SEPIC converter are another contribution of the paper. By means of the applications with up to 15 W SEPIC converter and simulations with DC source and PV panel, it is shown that LC filter ensures better results using DC source by applications regarding current ripple and noise level. However, C filter is better for PV panel by simulations than DC source, it is because PV panel exhibits current source character, and LC filter has lower current ripple. Also with PV source, LCL with damping filter transfers higher energy to the load than the others. Furthermore, LCL type filter reduces inductor by 35% and capacitor by 4.7 times in total. Moreover, LCL filter has higher efficiency with 88% than others in the applications and lower ripple for simulations with DC source.

An Alternate Rotor Geometry for Switched Reluctance Machine With Reduced Torque Ripple

Switched Reluctance Motor (SRM) benefits from a simple, low cost, and robust structure. However, it exhibits high levels of torque ripple and vibration due to its non-uniform distribution of the flux and force densities in the air gap. To address this problem, a novel rotor with optimally designed flux barriers has been designed to be used along with a conventional SRM stator. In this paper, an optimization algorithm comprised of Genetic Algorithm (GA) and Finite Element Analysis (FEA) has been used to identify the best rotor geometry for maintaining average torque while minimizing torque ripple and tangential vibration of the stator. The performance of the optimized motor is then compared with a conventional SRM of the same size experimentally. The results show significant improvement in torque ripple as well as vibration for the new topology with no tangible drop in efficiency at high speeds.

Amplitude-Phase Based Optimal Voltage Harmonic Injection for Speed Harmonic Minimization in SPMSM

Low torque ripple level is the prerequisite for surface-mounted permanent magnet synchronous machines (SPMSM) to maintain control accuracy and speed stability. Since the speed harmonic's amplitude is proportional to the torque harmonic's amplitude, torque ripple can be reduced by speed harmonic minimization. Harmonic injection method is a practical speed harmonic minimization method. But current harmonic regulation and complex theoretical derivation are required in existing methods. What's more, the effectiveness of many methods will deteriorate when the parameters of PMSM and PI controllers vary. In order to avoid the influence of parameter variations and complex algorithms, an amplitude-phase based optimal voltage harmonic injection method is proposed for speed harmonic minimization in this paper. The influence of the injected voltage harmonic's amplitude and phase on the speed harmonic's amplitude is firstly analyzed. And then a simple speed harmonic controller based on the optimization of injection voltage harmonic's amplitude and phase is designed. The proposed method does not rely on the motor parameters. Moreover, the proposed method is easy to implement. It does not need to regulate current harmonics. The proposed method is simulated and experimentally evaluated under both steady-state and transient conditions.

Wideband and Wide-Angle Switchable Spatial Filter/Shielding With Polarization-Independent Response

In this Letter, an active second-order frequency-selective surface (AFSS) that features a switchable wide pass-band is proposed. Compared to other multi-layer feeding structures, only one layer of FSS is elaborately reconfigured in this design, whose full planar symmetry structure is not destroyed, to achieve the desired all-polarized controlled behavior. The presented design provides good responses under different incident angles and polarizations. The fulfilled structure is composed of three FSS layers and is controlled by semiconductor switches. When the switches are in OFF-state, the proposed design acts as a high-transmittance second-order filter with a low ripple level, whose -0.5 dB passband width is over 24.4% and minimum insertion loss is only 0.1 dB. By switching the semiconductors to ON-state, the unit cells of the top FSS layer are short-connected, which leads to an ultra-wideband shielding behavior from 0 to 10 GHz. Moreover, the proposed structure presents consistent responses under 0°-90° rotation polarizations. Both filter and shielding responses can be obtained up to the 60° incidence. Finally, a prototype is fabricated and measured, and the desired wideband, high-efficiency, wide-angle, and polarization-insensitive switchable performances are obtained through equivalent-circuit calculations, numerical simulations, and experimental measurements.

Sub-second pair distribution function using a broad bandwidth monochromator.

Here the use of a broad energy bandwidth monochromator, i.e. a pair of B4C/W multilayer mirrors (MLMs), is demonstrated for X-ray total scattering (TS) measurements and pair distribution function (PDF) analysis. Data are collected both on powder samples and from metal oxo clusters in aqueous solution at various concentrations. A comparison between the MLM PDFs and those obtained using a standard Si(111) double-crystal monochromator shows that the measurements yield MLM PDFs of high quality which are suitable for structure refinement. Moreover, the effects of time resolution and concentration on the quality of the resulting PDFs of the metal oxo clusters are investigated. PDFs of heptamolybdate clusters and tungsten α-Keggin clusters from X-ray TS data were obtained with a time resolution down to 3 ms and still showed a similar level of Fourier ripples to PDFs obtained from 1 s measurements. This type of measurement could thus open up faster time-resolved TS and PDF studies.

ROBUST CONTROL OF LOW-COST DIRECT DRIVES BASED ON INTERIOR PERMANENT MAGNET SYNCHRONOUS MOTORS

Torque ripple compensation problem is considered for electrical drives, based on low-cost direct drive interior perma-nent magnet synchronous motors. Robustness properties of the speed and position control systems have been studied using time scale separation properties of the current, speed and position control loops. It is shown that system closed-loop dynamics according to new controller design has cascaded properties with speed and position control loops con-nected in series and therefore has potential of high frequency torque ripple compensation by increasing controllers gains. Experimental results are presented for two motors with similar rated data but significantly different level of the torque ripple. It is shown that despite of significand difference in parasitic torque amplitude, the similar position con-trol performance can be achieved. It makes proposed control algorithms suitable for both high dynamic performance and low-cost direct drive applications with medium performance requirements. References 13, figures 7.

Analysis of Frequency Adjustable Control of Permanent Magnet Synchronous Motor for Pump-controlled Actuators

Recently the pump-controlled system has actively been proposed as a replacement for conventional valve-controlled systems, to improve the energy efficiency in non-road mobile machinery. Earlier research demonstrated that a pump-controlled hydraulic system combines the best properties of traditional hydraulics and electric intelligence. This pump-controlled system can be realized via direct control of hydraulic pimp/motor by varying speed of electric motor without complex servo valves. Nowadays, a wide range of different electric motors is known and available with efficiency higher than 95% One of the most attractive option of electric motor is Permanent Magnet Synchronous Motor (PMSM) due to its size, power, and high efficiency.&#x0D; However, control of electric motors in pump-controlled systems has are not yet considered and not well researched.&#x0D; In this paper, the main objective of this investigation is determination of control values for the pump-controlled actuator and analysis of system’s behavior in different applications.&#x0D; Therefore, model of PMSM drive with pump-emulated load is proposed. Field Oriented Control (FOC) gives wide range of the speed regulation and smooth characteristics, but tuning of controllers is challenging.&#x0D; Case of the steering-modeled load represented that such operations need more power than other modes. More complex frequency converters allow to reach higher level of accuracy and decrease torque ripples, but complexity of such systems increases rapidly.

Sensorless DTC-SVM applied to an induction motor controlled by a three-level inverter using SMSFO

PurposeThe direct torque control (DTC) of induction motor (IM) drive is featured by high ripples in the electromagnetic torque and stator flux profiles because they are controlled by two hysteresis regulators. Furthermore, the machine flux is not directly measurable. Hence, it is better to reconstitute it from the instantaneous electrical equations of the machine. Once the stator flux is estimated, we can guarantee a reliable sensorless DTC control. Thus, the purpose of this research work is to ensure fast response and full reference tracking of the IM under sensorless DTC strategy with desired dynamic behavior and low ripple levels.Design/methodology/approachIn this work, an improved DTC strategy, which is DTC_SVM_3L, is suggested. The first step of the designed approach is to substitute the conventional inverter feeding the motor with a three-level inverter because it guarantees reduced switching losses, improved quality of voltage waveform and low-current total harmonic distortion rate. The second aim of this paper is to make the IM operate at a constant switching frequency by using the nearest three vectors-based space vector modulation (SVM) technique rather than hysteresis controllers. The third objective of this study is to conceive a sliding-mode stator flux observer, which can improve the control performances by using a sensorless algorithm to get an accurate estimation, and consequently, increase the reliability of the system and decrease the cost of using sensors. The stability of the proposed observer is demonstrated based on the Lyapunov theory. To overcome the load change disturbance in the proposed DTC control strategy, this paper exhibits a comparative assessment of four speed regulation methods: classical proportional and integral (PI) regulator, fuzzy logic PI controller, particle swarm optimization PI controller and backstepping regulator. The entire control algorithm was tested under different disturbances such as stator resistance and load torque variations.FindingsIt was ascertained that the IM, controlled with three-level inverter, exhibits good performances under the proposed DTC-SVM strategy based on a sliding-mode observer. The robustness of the suggested approach against parameter variations is also proved.Originality/valueThe theoretical development of the proposed control strategy is thoroughly described. Then, simulations using Matlab/Simulink software are launched to investigate the merits of the sensorless DTC-SVM command of three-level inverter-fed IM drive with different speed regulators.

A novel MS to SL vialess vertical transition for high‐performance substrate integrated filter

In this paper, a novel broadband microstrip-to-stripline (MS-to-SL) vialess vertical transition structure is presented and demonstrated. Firstly, the vialess vertical transition is introduced under two kinds of transmission lines and signal transmission between them through the slotline in the middle ground layer is realized. Then, the proposed vialess vertical transition structure is applied to build up a six-pole broadband high selective bandpass substrate integrated filter with an equal ripple level. After that, for fascinating the design, its design method is analyzed, and design flow is given. Finally, the proposed filter is fabricated and measured. All the simulated and measured results match well with each other.

Array‐based Fabry–Pérot cavity antenna for flat‐topped radiation pattern

AbstractIn this letter, an array‐based ray tracing model and Fabry–Pérot cavity antenna covered by frequency selective surfaces (FSS) are proposed to realize the flat‐topped radiation pattern (FTRP). Based on the array‐based model, a good FTRP can be obtained by combining the initial directivity of the feed array with the additional directivity of FSS‐type partially reflective surface. By using the proposed method, a low‐cost, lightweight, simple structure and dual‐polarization Fabry‐Pérot cavity antenna with small aperture size for FTRP is designed. From the measured results, the FTRP with more than 58° beamwidth and less than 2 dB ripple level in the frequency band of 2.4 to 2.7 GHz for indoor communication are obtained.

Existence of an optimized stellarator with simple coils

An optimized compact stellarator with four simple coils is obtained from direct optimization via a coil shape. The new stellarator consists of two interlocking coils and two vertical field coils similar to those of the Columbia Non-neutral Torus (CNT) (Pedersen et al., Phys. Rev. Lett., vol. 88, 2002, pp. 205002). The optimized configuration has a global magnetic well and a low helical ripple level comparable to that of Wendelstein 7-X (W7-X) (Wolf et al., Nucl. Fusion, vol. 57, 2017, pp. 102020). The two interlocking coils have a smooth three-dimensional shape much simpler than those of advanced stellarators such as W7-X. This result opens up possibilities of future stellarator reactors with simplified coils.

Induction Motor DTC Performance Improvement by Inserting Fuzzy Logic Controllers and Twelve-Sector Neural Network Switching Table

Human civilization has changed forever since induction motors were invented. Induction motors are widely used and have become the most prevalent electrical componentsdue to their beneficial characteristics. Many control strategies have been developed for their performance improvement, starting from scalar to vector to direct torque control. The latter, which is a class of vector control, was proposed as an alternative to ensure separate flux and torque control while remaining completely in a stationary reference frame. This technique allows direct inverter switching and reasonable simplicity compared to other vector control techniques, and it is less sensitive to parameter variation. Yet, the use of hysteresis controllers in conventional DTC involves undesired ripples in the stator current, flux, and torque, which lead to bad performances. This paper aims to minimize the ripple level and ensure the system’s performance in terms of robustness and stability. To generate the appropriate reference control voltages, the proposed method is an improved version of DTC, which combines the power of fuzzy logic, neural networks, and an increased number of sectors. Satisfactory results were obtained by numerical simulation in MATLAB/Simulink. The proposed method was proven to be a fast dynamic decoupled control that robustly responds to external disturbance and system uncertainties.