Simulated Voltage Waveforms Research Articles

Online Transient Measurements of EHV Cable System and Model Validation

The increasing utilization of HVAC underground power cables gives rise to technical challenges related to the occurrence of electromagnetic transients. This paper discusses measurements with sensors based on open air capacitances sensing the electric fields from the line having a wide frequency bandwidth and excellent electromagnetic compatibility performance. However, since the sensors are open air capacitors, they also intercept field lines from other phases and measurement decoupling is necessary. Results from measurements, using the differentiating/Integrating technique, at a 380 kV mixed overhead line underground power cable connection obtained at a transition point and at a substation are presented and compared with PSCAD/EMTDC simulations. The measurement system gives accurate results for low and high frequency transients, while the effect of uncertainties in the decoupling is minor. For switching transients, the simulation model was validated in terms of measured and simulated voltage waveforms resulting in similar maximum overvoltage and frequency content.

Three-Dimensional Electromagnetic Analysis of Tubular Permanent Magnet Linear Launcher

A short-stroke and large thrust axial magnetized tubular permanent magnet linear launcher (TPMLL) is presented in this paper. Its three-dimensional (3-D) finite-element (FE) models are established for sensitivity analyses on some parameters conducted to achieve greatest thrust. Then, its two-dimensional (2-D) FE models are also established. The electromagnetic thrusts calculated by 2-D and 3-D FE method and obtained from the prototype test are compared. Moreover, the prototype static and dynamic tests are conducted to verify the 2-D and 3-D electromagnetic analysis. The combined simulation between the control system and the 3-D FE model of the TPMLL is built. It can be seen that the simulated voltage waveforms and current waveforms of the winding, the simulated frequency curves of the mover with the movement range from –6 to 6 mm, are accordant with the tested results. Hence, the correctness of established FE models is further verified, and the feasibility of proposed control strategy is testified.

Electrical Oscillations of the UNU-ICTP Plasma Focus Device in the Early Breakdown Phase

Recent circuit driven electromagnetic particle in cell simulation of the United Nations University-International Centre for Theoretical Physics plasma focus device revealed regular oscillations in both the voltage and current profiles. The simulated voltage waveform agreed well with the experimental profile, where similar unaccounted oscillations were also observed. In this paper, the oscillations are attributed to the plasma inductance, whose value was calculated by circuit analysis and agreed reasonably well with the computed experimental value. A circuit simulation of the prebreakdown and postbreakdown phases, with the plasma inductance incorporated, reproduced with sufficiency accuracy the electromagnetic particle in cell generated waveforms and consequently confirmed our finding.

Factors affecting the dynamics of wire particles in gas‐insulated systems

AbstractThis paper introduces a theoretical study of the significant factors that affecting the dynamics of wire particles in a horizontal coaxial gas‐insulated transmission line (GITL) and/or gas‐insulated switchgear (GIS) systems. The dynamics of the particle is investigated using a computational algorithm and under different voltage waveforms, gas pressures and coating thicknesses. The simulated voltage waveforms are the 60 Hz AC, single and successive switching impulses (SI), and bipolar‐oscillatory and damped impulses. All the applied voltage waveforms are simulated with and without the DC prestress, except for the AC case. These voltages represent the actual waveforms that occur in practice. The present work highlights the dangerous situations of the particle dynamics and their methods of mitigation. Moreover, the investigated dynamic behaviours of such defect under AC energization give excellent signs for the recognition by the acoustic detection technique.

Complex dynamics of resistively and inductively shunted Josephson junctions

We have measured Nb–AlOx–Nb Josephson tunnel junctions which have resistive shunts with different parasitic inductances. Numerical simulations reveal that specific features in the experimental current–voltage (I–V) characteristics of these devices are dc signatures of complex ac behavior. Depending on the inductance of the shunt loop and the capacitance of the junction, these features may either appear or disappear as the temperature of the device is increased. Examination of the simulated voltage waveforms allows us to map regions of the parameter space which exhibit complicated behavior. These regions should be avoided when a nearly sinusoidal voltage waveform is desired, as is the case for Josephson junction-based oscillators. The agreement of the experimental and simulated I–V curves also enables us to accurately determine the inductance of the shunts and the capacitance of the junctions.

Analysis and prevention of DRAM latch-up during power-on

The occasional power-on latch-up phenomenon of DRAM modules with a data bus shared by multiple DRAM chips on different modules was investigated and the circuit techniques for latch-up prevention were presented. Through HSPICE simulations and measurements, the latch-up triggering source was identified-to be the excessive voltage drop at the n-well pick-up of the CMOS transmission gate of read data latch circuit due to the short-circuit current which flows when the bus contention occurs during power-on. By extracting the HSPICE Gummel-Poon model parameters of the parasitic bipolar transistors of DRAM chips from the measured I-V and C-V data, HSPICE simulations were performed for the power-on latch-up phenomenon of DRAM chips. Good agreements were achieved between measured and simulated voltage waveforms. In order to prevent the power-on latch-up even when the control signals (RAS, GAS) do not track with the power supply, two circuit techniques were presented to solve the problem. One is to replace the CMOS transmission gate by a CMOS tristate inverter in the DRAM chip design and the other is to start the CAS-BEPORE-RAS (CBR) refresh cycle during power-on and thus disable all the Dout buffers of DRAM chips during the initial power-on period.