Low Impedance Load Research Articles

Analysis on the low-frequency electromagnetic pulse coupling to horizontal electrically short lines

In this study, we investigated the coupling features of the nuclear electromagnetic pulse (NEMP) on overhead cables in the middle-and-far regions, different from the transmission line model commonly used for field-line coupling in high-frequency cases, using a simpler lumped approximation to solve the electrically small size model in low-frequency cases. To verify its effectiveness, a simulation model with the same conditions was set up using the software of Computer Simulation Technology (CST), and cable coupling experiments were performed in a laboratory environment using a bounded-wave electromagnetic pulse simulator. The calculated results of the lumped approximation circuit were compared with the CST simulation and measured results, and the agreement was good. The results also shows that the load exhibits a differential response in the case of the low impedance and it is consistent with the excitation signal in the case of the high impedance. Finally, some more experiments were constructed to analyzed the effect of different cable parameters on the cable load response through experiments, and the experimental results are also in general agreement with the theoretical analysis, in which the induced signal of the low-impedance load is mainly determined by the magnetic field in the direction normal to the cable and the ground loop and the induced signal of the high-impedance load is mainly determined by the electric field in the direction of the height of the cable erection.

Solid Discharger for the Systems Forming a Current Pulse in Low-Impedance Loads of Inductive Storages of Electromagnetic Energy

Solid Discharger for the Systems Forming a Current Pulse in Low-Impedance Loads of Inductive Storages of Electromagnetic Energy

THE RESONANT AMPLIFIER OF THE ACTIVE ELECTRICAL POWER WITH ADDITIONAL VOLTAGE SOURCE. SUGGESTIONS, ANALYSIS, NUMERICAL ESTIMATES

The problem of increasing energy saving in industry leads to the need to develop new technical devices. The paper presents and analyzes the circuit of the resonance amplifier of active electric power, evaluates the characteristics of electromagnetic processes for the fundamental substantiation of the operation of real devices based on this circuit. Mathematical analysis of electromagnetic processes taking place was carried out using strict methods of the theory of electric circuits. The advantages of this scheme in comparison with similar previous proposals are shown. The device includes four active-reactive circuits that are inductively connected. The first of them is an input circuit with a harmonic signal source that needs to be amplified. The second circuit generates enhanced reactive power in the "voltage resonance" mode. The third circuit with an additional voltage source provides reactive power output from the second circuit in the "resonance of currents" mode without adverse effects on amplification processes. The fourth circuit, inductively connected to the third circuit, contains an output load - a resistor that simulates the allocation of active power. On the basis of the analysis and numerical evaluation of the characteristics of the processes taking place in the proposed scheme of the resonance amplifier of active electric power, its basic efficiency is shown. The calculations of the experimental model made it possible to formulate recommendations for the selection of circuit elements of a working resonant amplifier with a high efficiency for low-impedance output loads. The considered real parameters of the device make it possible to minimize the dissipation of the energy of converted electrical signals and to increase the amplification factor of the electric power of harmonic currents and voltage by choosing the element base. The obtained results can be considered as practical recommendations for the creation of real devices for amplifying active electric power for use in various industries.

Твердотельный разрядник для систем формирования импульса тока в низкоимпедансных нагрузках индуктивных накопителей электромагнитной энергии

The paper considers the use of a solid discharger with a cathode localized enhancement of electric field working together with an opening switch of an inductive storage to form a quick-rising current pulse in a low-impedance load. The physical factors bringing to an increase in pulse sharpening efficiency are specified. The discharger geometry variant is proposed. The technique for a determination of its parameters depending on the experimental requirements and conditions is described. The paper presents the results of the experiments on a stationary facility demonstrating a possibility to generate the current pulses with a rise front ~ 100 ns in the inductive loads ~ 10 nH. The obtained results allow giving a recommendation to use this type of dischargers to form multi-megaampere current pulses with submicrosecond rise front (up to ~ 100 ns) for the inductive energy storages and, in particular, for the explosive magnetic (magnetocumulative) generators., in the circuits with low-impedance loads.

Solid discharger for the systems forming a current pulse in low-impedance loads of inductive storages of electromagnetic energy

The paper considers the use of a solid discharger with a cathode localized enhancement of electric field working together with an opening switch of an inductive storage to form a quick-rising current pulse in a low-impedance load. The physical factors bringing to an increase in pulse sharpening efficiency are specified. The discharger geometry variant is proposed. The technique for a determination of its parameters depending on the experimental requirements and conditions is described. The paper presents the results of the experiments on a stationary facility demonstrating a possibility to generate the current pulses with a rise front ~100 ns in the inductive loads ~10 nH. The obtained results allow giving a recommendation to use this type of dischargers to form multi-megaampere current pulses with submicrosecond rise front (up to ~100 ns) for the inductive energy storages and, in particular, for the explosive magnetic (magnetocumulative) generators., in the circuits with low-impedance loads. Keywords: solid (condensed) dielectric, breakdown delay, overvoltage.

An Introduction to High Data Rate Current-Steering Nyquist DACs: Fasten your seat belts

The current-steering DAC is the most common architecture for medium resolution and ultrahigh data rates, extending well to tens of giga samples per seconds in nanometer MOS process technologies. It is commonly found in all types of communication systems, instrumentation, and consumer applications, among others, due to its capability of efficiently synthesizing the analog output on a low impedance load. This tutorial builds upon previous ones, pointing to a variety of techniques that extend the current-steering DAC’s dynamic performance to an ever-higher input data rate and analog output frequency.

Investigation on Nonuniformity of Magnetic Field in Curved Coaxial Magnetically Insulated Transmission Line System

The curved coaxial magnetically insulated transmission line (MITL) generates nonuniform magnetic fields, causing substantial current loss and nonuniform current in the system. However, the nonuniform magnetic field can recover uniformity with a certain distance after the curved region. In this article, 3-D particle-in-cell simulations were carried out to investigate the mechanism of the recovery of nonuniform magnetic field in the region after the 90°-curved MITL and the factors influencing the distance needed for the recovery of the uniformity of magnetic field. The results indicate that a high-impedance load causes higher nonuniformity of the magnetic field in the MITL after the curved region than the situation with a low-impedance load. The profile of nonuniformity of the magnetic field in the MITL after the curved region transforms from an exponentially decreasing shape to a “W” shape when the MITL operates from a load-limited case to a self-limited case. The distance for the recovery of the nonuniform magnetic field after the 90°-curved MITL is about 2–3 times the radius of the anode, and has no independence with the radii of curvature and cathode. This work fascinates the improvement of magnetic field uniformity in the curved MITL system.

Design and Implementation of a Capacitive Energy Storage Pulse Drive Source

According to the requirement of driving power supply for pulsed semiconductor laser, a method of constant current output is proposed by combining large energy storage capacitance with MOS transistor working in linear region to solve the problem of generating high amplitude, short pulse width and high stability current pulse on low impedance load. The front stage uses the buck circuit to charge the energy storage capacitor, and through the hysteresis control of the buck circuit, the voltage of the energy storage capacitor is controlled. In the latter stage, the MOS transistor working in the linear region is used to realize the pulse output, and the PI module is used to adjust the output current to ensure the constant output current. Through PSPICE simulation, the key factors affecting the output pulse amplitude, pulse width and rise time are analyzed and verified by experiments. Using 155V DC power supply, the experimental results show that the capacitor energy storage pulse driver circuit can achieve a pulse constant current output with amplitude of 30A, pulse width of 300μs and rise time of less than 10μs on a 5 Ω low impedance load.

Design and Implementation of High Power Pulse Constant Current Source

According to the requirement of the semiconductor laser for driving power supply, aiming at the problem of how to produce the current pulse with high amplitude, short pulse width and high stability on the low impedance load, a method of realizing the constant current output of the pulse by using the combination of the buck transform circuit and the linear regulation module is proposed. The Buck circuit is hysteresis controlled to control the storage capacitance voltage, and then the MOSFET working in the linear region is adjusted by the PI module to ensure constant current output on the load. The key factors affecting the output pulse amplitude, pulse width, front and back edge parameters are also analyzed and verified by experiments. The results of 170V DC power supply show that the circuit designed in this paper can output 30A, 250us pulse width and rise time less than 10us pulse constant current output on 5Ω low impedance load.

Reflection-Based Short Pulse Generation in CMOS

In this letter, a low cost, compact, and systematic method for generating a short pulse and efficiently delivering it to low impedance loads is proposed. The load can be a resistive on-chip or off-chip load, an antenna, or another stage such as a power combiner. The technique is inspired by time-domain reflectometry from a short-circuited termination. The technique is fully compatible with the CMOS technology. To show the feasibility of the idea, two chips are fabricated and tested in a low cost 0.11- $\mu \text{m}$ CMOS process with fT ≈ 80GHz. The full-width at half maximum (FWHM) of the pulses are 6.8ps and 8.8ps, and the amplitudes over a 50 ${\Omega }$ load are 0.62V and 1V. Either of the chips occupies ${1160\times 540\,{\mu \mathrm {m}}^{2}}$ in area.

A Series-Connected-Load Doherty Power Amplifier With Push–Pull Main and Auxiliary Amplifiers for Base Station Applications

This article proposes a new approach for designing high-power Doherty power amplifiers (DPAs) with extended bandwidth. The analysis starts with a generic series-connected load (SCL) DPA architecture to derive equations that relate the $ABCD$ parameters of the output combiner to the transistors’ optimum and load impedances. These equations make it possible to significantly increase the load impedance in the SCL DPA compared to the more popular parallel-connected load (PCL) DPA architecture—a feature of particular importance when targeting very high output power DPAs for macrocell base stations and broadcast applications. High-power PCL DPAs require very low load impedance, seriously complicating their design and limiting the achievable bandwidth of the DPA. To further maximize the load impedance increase, the proposed SCL DPA uses a push–pull topology for the main and peaking amplifier stages. A low-loss planar balanced-to-unbalanced transformer (balun)-based combiner network is then utilized to realize the DPA series-connected combiner while absorbing the transistor’s parasitics. The proposed approach is applied to design a proof-of-concept 350-W SCL DPA operating over the band spanning from 720 to 980 MHz. The prototype demonstrated a peak output power of about 55 dBm over a 30% fractional bandwidth with a 6-dB back-off efficiency, measured using a pulsed signal, of between 46.6% and 54.6%. Furthermore, the modulated signal-based measurement results confirmed the linearizability of the SCL DPA prototype, while it maintained a back-off efficiency over 50% for a signal with 7.1-dB peak-to-average power ratio.

Low-Voltage AlGaAs/GaAs Thyristors as High-Peak-Current Pulse Switches for High-Power Semiconductor Laser Pumping

The dynamic characteristics of a low-voltage thyristor based on an AlGaAs/GaAs heterostructure have been studied in the mode of generation of high-amplitude pulses with width of tens of nanoseconds in a circuit with low-impedance load based on an array of high-power AlGaAs/GaAs semiconductor lasers. The presented approach uses thyristors and diode laser arrays as discrete components, so it can be extended to other (not AlGaAs/GaAs-based) semiconductor lasers. It is demonstrated that a current pulse can be generated with an amplitude of 69 A and a width of 40 ns in a vertically assembled stack of an array of semiconductor lasers and thyristors. It was shown that raising the number of single thyristors does not lead to pulse broadening and makes it possible to raise several-fold the peak current amplitude to 208 A, with the peak laser emission power reaching a value of 78 W.

A model for the triboelectric nanogenerator with inductive load and its energy boost potential

A new method which exploits energy oscillation between the TENG and an inductive load is proposed to boost the energy output for the triboelectric nanogenerator (TENG) with contact-separation (CS) mode. A time-domain theoretical model is established to analyze the operation of the energy oscillation circuit – (TENG and the inductive circuit) comprehensively. In the model, the TENG is constituted by a series of finite-sized charged planes (FSCP), dielectric materials, and the air-gap. The inductive load is used to promote the oscillation of charge on the TENG. With the newly developed inductive load model, we can observe that, at small load resistance, a boost can be achieved from the voltage on the TENG and the current flowing in the circuit and therefore the energy output observed both from the source (TENG) and on the load (resistor) show increased value. Finally, it is found that for a specific load (resistor) and inductor, the boost performance will reach its peak value for an optimal value of the motion speed for the air-gap between TENG planes (or the variation speed of the mechanic energy). This proposed inductive circuit shows the potential of a standard method for the performance improvement of the energy harvesting scenario using the TENG in particularly for low load impedance.

Hybrid Analog and Digital Control of a High Current Converter Based on an EDLC Bank for Rapidly Decreasing Input Voltage

This paper proposes unconventional control techniques for a portable power supply consisting of electric double-layer capacitors (EDLCs), a dc-dc converter, and a low-impedance load such a plasma load. Between the EDLCs and the plasma load consuming high power, a dc-dc converter is required to control the output voltage from the rapidly decreasing voltage of EDLCs. In addition, the dc-dc converter should maintain a set point by responding to arcs occurred in plasma process. This paper proposed hybrid analog and digital controls for a nonideal boost converter which was setup by theoretical analysis. The proposed system is verified with experiment and simulation. As a result, the proposed control method can maintain the constant output voltage longer than a traditional analog pulsewidth modulation control.

A novel compact low impedance Marx generator with quasi-rectangular pulse output

In this paper, a novel low impedance compact Marx generator with near-square pulse output based on the Fourier theory is developed. Compared with the traditional Marx generator, capacitors with different capacity have been used. It can generate a high-voltage quasi-rectangular pulse with a width of 100 ns at low impedance load, and it also has high energy density and power density. The generator consists of 16 modules. Each module comprises an integrative single-ended plastic case capacitor with a nominal value of 54 nF, four ceramic capacitors with a nominal value of 1.5 nF, a gas switch, a charging inductor, a grounding inductor, and insulators which provide mechanical support for all elements. In the module, different discharge periods from different capacitors add to the main circuit to form a quasi-rectangular pulse. The design process of the generator is analyzed, and the test results are provided here. The generator achieved pulse output with a rise time of 32 ns, pulse width of 120 ns, flat-topped width (95%-95%) of 50 ns, voltage of 550 kV, and power of 20 GW.

A 25-F Electric Double-Layer Capacitor Bank and DC Power Supply for Portable High-Current Applications

A portable dc power supply based on electric double-layer capacitor (EDLC) bank was established for high-power applications. EDLC bank needs a dc–dc converter to maintain a constant output voltage and current. Especially, a low-impedance load makes the voltage of capacitors discharge faster, and their discharging time is determined by RC time constant. The proposed system is designed as a fundamental concept, and deals with some issues occurring in a large-scale system. Also, this paper provides detailed information and consideration for a real establishment. Last, we performed a full-scale experiment using basic techniques.

A Fractional Slot Multiphase Air-Core Compulsator With Concentrated Winding

Compulsator is a specially designed generator capable of delivering high current pulses to a low-impedance load, such as the electromagnetic railgun. In order to increase the tip speed of the rotor, advanced composite materials have been used in the recent compulsator prototype, which is mentioned as air core instead of the traditional iron core. For typical air-core compulsators, there are no slots and steel teeth to place the armature windings due to the nonmachinability of composite materials. Therefore, concentric windings in racetrack style are often adopted instead of traditional lap winding in most cases, since it is more convenient to be fixed by composite materials. However, overlap occurs at the end winding part for multiphase compulsators, which are not easy to be formed during the manufacture process. In this paper, a fractional slot multiphase air-core compulsator with concentrated windings is proposed and analyzed. The main advantage of fractional slot configuration is that it can offer a concentrated winding structure under certain conditions, which means each coil only spans one “tooth,” and will not cause any intersection between each phase at the end winding. Two referenced fractional slot air-core compulsators with two phases, six poles, and four “slots” or eight “slots” (q = 1/3 and q = 2/3, q is the “slot” per pole per phase) are analyzed and compared with the performance of a traditional integral slot machine. The results indicated that the output voltage and self-excitation performance of a fractional slot compulsator can reach the same level with an integral slot one, and the discharging performance can reach an acceptable level. Thus, the fractional slot multiphase concept can be further used to improve the manufacture process of the winding in the future.

Synchronization of Multiple Pulsed Alternators Discharging Into an EM Launcher

As the energy level in the projectile increases, it becomes necessary to use multiple pulsed alternators discharging in parallel into the electromagnetic launcher. Another reason for having more than one machine is that one needs to compensate for the torque and gyroscopic effects of the pulsed alternator. This requires that machines be built in counter-rotating pairs. These machines are identical in all respects except for their direction of rotation. A study was conducted to determine how the machines can be motored so that they stay in lock step in speed and phase as they are motored to full speed. The methods of connecting these multiple machines are discussed. The aim of the connection scheme is to allow the machines to naturally stay locked in speed and phase throughout its operating range. Sensitivity of the performance of these machines to small variations in the machine parameters, which is to be expected in the machines, is discussed. Sensitivity of the discharge performance to small phase angle mismatches due to tolerances is also discussed. To verify the conclusions of the paper, an experiment was performed on two identical 50-kVA machines discharging into a low impedance load. The motoring system that is discussed in this paper was implemented in this experiment, which kept the machines in lock step. This motoring system is described. Thereafter, discharges were made at various speeds and field current levels. Phase angle mismatches were introduced between the two machines to see how it affected current sharing. The results and conclusions of these tests are presented in this paper.

Electromagnetic Shields of the Air-Core Compulsator

Air-core compulsator is a specially designed generator capable of delivering high current pulses to a low-impedance load, such as the electromagnetic railgun. Due to the absence of ferromagnetic material, the field strength in air-core compulsator can reach 4-6 T. Therefore, electromagnetic shields are required to protect the surrounding operators and instruments from exposure to high magnetic fields. This paper investigates the design methodology of the shield as well as its influence on the performance of the machine. A dynamic model is built to analyze the shielding effect and its performance tradeoffs of a reference compulsator. The result indicates that the effect of the eddy-current shield is much better than the magnetic shield using ferromagnetic material, due to the high frequency and the magnetic saturations. The magnetic field can be completely screened inside the conducting shield, at the expense of some electrical, mechanical, and thermal performance. Since the eddy-current density is sensitive to the location of the shield, the influences of the conducting shield are parametrically analyzed. Using the electromagnetic and thermal coupling field link, the temperature rise of the shield is also calculated. Analysis results can provide the theoretical guides for the shielding of the air-core compulsator investigation in the future.

Vibration Energy Harvesting Based on Magnet and Coil Arrays for Watt-Level Handheld Power Source

Electromagnetic energy conversion, based on Faraday's law, can deliver a relatively large, continuous power to a low impedance load from a vibrating body. However, increasing the energy-conversion efficiency and keeping it high at a relatively large vibration amplitude have been difficult, and no miniature energy harvester has shown more than tens of milliwatt power level from submillimeter vibration amplitude. Here we provide a new energy-conversion technique to convert mechanical vibration into electrical energy with unprecedented power level of more than a quarter watt out of submillimeter vibration amplitude. The technique uses an array of alternating northand south-orientation magnets to enhance magnetic flux change by more than an order of magnitude. A newly fabricated harvester occupying 51 × 51 × 10 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> (= 26 cc) and weighing 90 g generates an electromotive force (EMF) of ν <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p-p</sub> = 28.8 V with 263 mW power output (into 96-W load) when it is vibrated at 65 Hz with vibration amplitude of 660 μm. The power level is high enough to light an incandescent light bulb. Also, its microfabricated version occupying 20 × 5 × 0.9 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> (= 0.09 cc) and weighing 0.5 g generates an EMF of ν <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p-p</sub> = 30 mV with 2.6-μW power output (into 10.8-W load) when it is vibrated at 290 Hz with vibration amplitude of 11 μm.