Capacitor Clamped Coupled Inductor Bi-Directional DC-DC Converter with Smooth Starting

In this paper, a new type of capacitor clamped coupled inductor bidirectional DC–DC converter is proposed, which offers high voltage gain with smooth starting current transients, as well as reduced stresses on the capacitor. Steady state operation, mathematical modelling, and state space modelling for the proposed converter are presented in detail. A simplified single voltage clamped circuit is developed to mitigate the voltage spikes caused due to the coupled inductor by recovering the leakage energy effectively. Moreover, the clamping capacitor helps in reducing the ripples in output voltage, which in effect significantly reduces the stress on the switch and offers less ripple content at the load terminals. Simulation of the proposed converter is carried out using Simulink/MATLAB for the conversion of 24V DC to 200V DC. For this conversion, simulation results have proven that there is reduction of 13.64% of capacitor voltage stresses. Further, under line varying conditions, converter responses have proven that there is a 119% and 25.25% reduction in input current and output voltage transients, respectively. Similarly, 25.25% and 76.5% transient reductions of input current are observed for line and control parameter variations. The hardware investigation of the converter was carried out with a 100 W, 24 V/200 V setup. The converter achieved efficiency of 93.8%. The observations supplement the simulation results.

Dynamic Performance Characterization Techniques in Gallium Nitride-Based Electronic Devices

In this paper, we compare and discuss the main techniques for the analysis of the dynamic performance of GaN-based transistors. The pulsed current-voltage characterization provides information on the effect of different trapping voltages on various bias points of the device under test, leading to the detection of all the possible effects, as well as to the choice of the optimal filling and measure bias conditions in other techniques. The drain current transients use one of the identified bias configurations to extract information on the deep level signature responsible for the performance variation and, thus, they can pinpoint the corresponding physical crystal lattice configuration, providing useful information to the growers on how the issue can be solved. Finally, given the complex interplay between the filling and emission time constants, the gate frequency sweeps can be used to obtain the real performance in the target operating condition.

Bus Impact on the Inductance Distribution of Electromagnetic Launchers

<div>Simulations are crucial in the electromagnetic launcher (EML) researches on account of extreme physical conditions. More energy into the system adds weight to the model’s accuracy as the operation risk rises. In this paper, the electromagnetic impact of the bus structure is discovered in a recently developed EMFY-3 electromagnetic launcher, is presented. An H-shaped bus structure is used for current injection. However, experiments showed that the H-shaped bus changes inductance calculations. A careful examination is made to reveal the physical reasoning of the bus impact. We hypothesize that the rail portion surrounded with bus geometry has less inductance than the rest due to the eddy current created by rail current transients, which should be calculated carefully through numerical calculations, i.e., 3-D Finite Element Method (FEM). Two different simulation models were constructed to test the hypothesis. Moreover, rail currents, breech, and muzzle voltages are measured to investigate electromagnetic calculations. Results showed a good agreement with experiments where the bus structure was modeled explicitly. That aspect showed that the bus structure should be well-examined when multiple PPS are connected.</div>

Bus Impact on the Inductance Distribution of Electromagnetic Launchers

<div>Simulations are crucial in the electromagnetic launcher (EML) researches on account of extreme physical conditions. More energy into the system adds weight to the model’s accuracy as the operation risk rises. In this paper, the electromagnetic impact of the bus structure is discovered in a recently developed EMFY-3 electromagnetic launcher, is presented. An H-shaped bus structure is used for current injection. However, experiments showed that the H-shaped bus changes inductance calculations. A careful examination is made to reveal the physical reasoning of the bus impact. We hypothesize that the rail portion surrounded with bus geometry has less inductance than the rest due to the eddy current created by rail current transients, which should be calculated carefully through numerical calculations, i.e., 3-D Finite Element Method (FEM). Two different simulation models were constructed to test the hypothesis. Moreover, rail currents, breech, and muzzle voltages are measured to investigate electromagnetic calculations. Results showed a good agreement with experiments where the bus structure was modeled explicitly. That aspect showed that the bus structure should be well-examined when multiple PPS are connected.</div>

In situ investigation on the role of hydrogen evolution on the estimated metastable pit sizes in an Al-Mg alloy

The fraction of pit dissolution charge that contributes to hydrogen evolution (HE) occurring within metastable pits (analyzed in real-time) was determined to evaluate the error it introduces in the pit size estimations derived merely from the analysis of dissolution current. With in situ optical time-lapse imaging, the charge consumed by HE (C&lt;sub&gt;HE&lt;/sub&gt;) during the current transients was determined from the size of the hydrogen bubbles evolving at real-time metastable pit locations in an aged Al-Mg alloy. The ratio C&lt;sub&gt;HE&lt;/sub&gt;/C&lt;sub&gt;pit&lt;/sub&gt; was observed to range between 0.019 and 0.052 depending on the charge of the transient. This difference was attributed to the catalytic nature of the pit surface that develops as a consequence of the pertinent pitting mechanism. Therefore, it was concluded that the HE within the metastable pits might not play a significant role in the underestimation of metastable pit sizes determined from the current transients recorded at anodic potentials below E&lt;sub&gt;pit&lt;/sub&gt;.