Systematic Design and Circuit Analysis of Lightning Impulse Voltage Generation on Low-Inductance Loads

The well-known circuit for the generation of lightning impulse voltage (LIV) on low-inductance loads was introduced by Glaninger in 1975, and the circuit component selection was proposed by Feser. However, the circuit and the approach for the component selection have some difficulties for which further adjustment is required for obtaining the waveform parameters according to the standard requirement. In this paper, an extended Glaninger’s circuit with an additional series resistor is proposed. Furthermore, a systematic design and circuit analysis of LIV generation for low-inductance loads are developed. With the help of a circuit simulator, the circuit analysis for the component selection is described. The validity of the proposed circuit was confirmed by some experimental results in comparison with the simulated ones. The proposed circuit and component selection provide not only the generation waveform according to the standard requirement but also other promising performances in terms of the wide inductance load range from 400 μH to 4 mH, a voltage efficiency of over 80%, an overshoot voltage of below 5%, an undershoot voltage of below 40%, and a maximum charging capacitance of 10 μF. From the simulated and experimental results, the proposed circuit and component selection approach is very useful for the LIV tests on low-inductance loads instead of using the conventional approach based on trial and error.

Pattern Formation in a RD-MCNN with Locally Active Memristors

This chapter presents the mathematical investigation of the emergence of static patterns in a Reaction–Diffusion Memristor Cellular Nonlinear Network (RD-MCNN) structure via the application of the theory of local activity. The proposed RD-MCNN has a planar grid structure, which consists of identical memristive cells, and the couplings are established in a purely resistive fashion. The single cell has a compact design being composed of a locally active memristor in parallel with a capacitor, besides the bias circuitry, namely a DC voltage source and its series resistor. We first introduce the mathematical model of the locally active memristor and then study the main characteristics of its AC equivalent circuit. Later on, we perform a stability analysis to obtain the stability criteria for the single cell. Consequently, we apply the theory of local activity to extract the parameter space associated with locally active, edge-of-chaos, and sharp-edge-of-chaos domains, performing all the necessary calculations parametrically. The corresponding parameter space domains are represented in terms of intrinsic cell characteristics such as the DC operating point, the capacitance, and the coupling resistance. Finally, we simulate the proposed RD-MCNN structure where we demonstrate the emergence of pattern formation for various values of the design parameters.

A New Simulated Inductor with Reduced Series Resistor Using a Single VCII±

This paper presents a new realization of a grounded simulated inductor using a single dual output second-generation voltage conveyor (VCII±) as an active building block, two resistors and one grounded capacitor. The main characteristic of the proposed circuit is that the value of the series resistor can be significantly reduced. Thus, it has the property of improved low-frequency performance. Another feature is the use of a grounded capacitor that makes the proposed circuit attractive for integrated circuit (IC) realization. A simple CMOS implementation of the required VCII± is used. However, a single passive component-matching condition is required for the proposed structure. As an application example, a standard fifth-order high-pass ladder filter is also given. SPICE simulations using 0.18 μm CMOS technology parameters and a supply voltage of ±0.9 V as well as experimental verifications, are carried out to support the theory.

LEDs driven by AC without transformers or rectifiers

We explore the driving of LEDs by untransformed AC. An extreme case is driving 1.9 V threshold (red) LEDs with UK mains, peak voltage 325 V. Commonly, driving is by transformed, rectified (DC) supply with a series resistor (where a significant fraction of the power is wasted) to limit current in the LED. With AC, one can instead reactively limit to a maximum current safe for an LED by employing a series capacitive impedance. Cheaper and simpler supplies can thus be employed in some cases. We analyse such non-linear circuits, and also explore questions of duty cycle and power experimentally.

A New Research Method for Corrosion Defect in Metal Pipeline by Using Pulsed Eddy Current

Pulsed eddy current (PEC) is a new technique to distinguish corrosion defeats inside and outside the metal pipeline. In comparison with other eddy current techniques, the PEC technique has the advantage of being simple and high velocity. In this article, a brand-new PEC probe based on differential conductivity is established through the combination of modules like square wave generator, eddy current coil bridge, differential current, voltage sample circuits and so on. The 50% duty cycle square wave is used as the driving signal. To measure differential conductance, a coil bridge configuration with two legs is adopted. One leg is composed of measurement eddy current coil and the in-series resistor, and the other is reference eddy current coil and the in-series resistor. Because the two legs go through defects in pipeline non-synchronously, there is a differential conductance between the two coils. A trans-impedance amplify circuit is used to detect coil eddy current. At the same time, two amplifiers are used to measure the differential voltage between the two coils. A 14 bit ADC is used to sample differential voltage, measurement and reference eddy currents which transferred to differential current by main processor Complex Programmable Logic Device (CPLD). CPLD is used to get differential conductance by differential current divide differential voltage. At last the eddy current signal sampling sequence is developed. A dynamic testing fixture with artificial defects carved on the pipeline is used to validate PEC probe’s accuracy. The differential conductance signals were displayed on the oscilloscope. Results showed that the inside defect had two peaks, positive peak and negative peak, but the outside defect only had one positive peak. We can conclude that the brand-new PEC probe has high accuracy in distinguishing the inside and outside defects.

Technique for Measuring Magnitudes and Phases of Voltage and Current in the Band-Selective Parallel LCR Circuit

The current in the parallel LCR (inductor, capacitor and resistor) circuit depends not only on the magnitude of the applied electromotive force (emf) but also on its frequency. The circuit current in the parallel LCR circuit becomes very small in the resonating region, but at the same time, the potential difference across the LC tank becomes very large. These results are justified if there is a large induced current in the LC tank in such a way that the inductive and capacitive branch currents are nearly out of phase so that the vector sum of the currents be minimal. This theory can be verified by inserting a small series resistor in each branch. Finally, calculated magnitudes and phases of the potential differences across the newly connected resistors which are directly related to the magnitudes and phases of corresponding branch currents verify the theory.

Analytical Performance Prediction of an Electromagnetic Launcher and Its Validation by Numerical Analyses and Experiments

An electromagnetic launcher (EML) is used to generate high launching velocities. The basic governing equation of the propulsion force of an EML is that the propulsion force is directly proportional to current and inductance gradient. L ′ is the inductance gradient that refers to the increase or decrease in the inductance with the length of rails. The inductance gradient is easily calculated because it is a function of the rail shape and frequency. However, current ( I ) flowing in an EML is calculated by the series resistor, inductor, and capacitor (RLC) equation of the equivalent circuit. Here, L is not constant and increases as the projectile muzzles. Owing to the increase in inductance, the current ( I ) and voltage ( V ) vary depending on the projectile position. Therefore, inductance, current, and voltage should be exactly obtained to calculate the exact current at a specific time. This study deals with analytical performance prediction using the relation EML propulsion force with real-time current, which is based on an increase in resistance and inductance at a specific time. To validate this approach, the results of the current waves are compared via numerical analyses and experiments. Using this prediction method, it is possible to determine and optimize the rail shape and length from the capacitor bank and vice versa.