Shunt Coil Research Articles

Unusual Complications of Ventriculoperitoneal Shunt Surgery

Background: Ventriculoperitoneal shunt (VP shunt) surgery is one of the most common procedures being performed in the pediatric age group in neurosurgical centers worldwide. Although considered a simple surgery, the complications have made it one of the most difficult procedures to manage in the long term. In this study, we describe our experiences in managing the unusual complications of this common procedure in children. Materials and Methods: This retrospective study enrolled 13 pediatric cases having unusual complications related to VP shunt who presented to us from August 2013 to August 2019. All the cases were evaluated for their demographic profile, type of complications, possible pathophysiology, outcome, and management. We had used only spring-valve-based Chhabra VP shunt in all of our cases. Results: The age group ranged between 2 and 18 years, with a male to female ratio of 9:4. Anal extrusion of distal shunt tube was observed in four cases, and two cases each of urethral and oral extrusion were also seen. Two cases developed extrusion of shunt tube through the anterior abdominal wall and one case developed umbilical fistula. Multiple extradural hematoma and intraventricular bleed with partial shunt coil were also seen in each of the cases, respectively. All cases were managed as per need. Conclusion: Unusual complications of VP shunt surgery are increasingly being observed nowadays. Prompt diagnosis and treatment of these complications result in an excellent outcome.

"Barefoot" matriarchs take on India's electricity gap [News

The women wielding soldering irons in this rustic solar engineering workshop may not know how to read or write, but they know their way around their circuit boards. “This is the shunt coil,” Jansya Devi says, with a proud smile. “This is an eight-pin connector, and this is a drum coil.” These technical words were not in Devi’s vocabulary a few months ago. She hails from Bihar, a state in eastern India known mainly for its rural poverty. Her village doesn’t get electricity from the national power grid, she says, and after dark she typically does her housework by the light of a kerosene lantern and candles. She dreads the monsoon season, when high winds make it difficult to keep the wicks lit. She has a mobile phone, but to charge it she has to send it along with someone making a trip to the nearest town.

Improvement of the method used for control of starting direkt-currentrailway motor

The analysis of methods for rotation speed control of direct-current traction motors with the series and compound excitation is conducted in the paper. The scheme to improve energy efficiency of speed control devices of traction electric motors of public electric transport rolling stock is proposed. The proposed scheme using the increasing DC-DC converter allows to perform a smooth TEM field weakening, improve the shunt coil copper use and reduce electric power consumption at starting the rolling stock. In this case, weakening the compound excitation TEM field is conducted by changing the current in both series, due to the input converter circuit, and shunt coil. Moreover, current control in the shunt coil, the magnetizing force of which is directed opposite the magnetizing force of the series coil, is performed due to the output converter circuit. The electrical schematic diagram of the test stand and results of studying the proposed field weakening method are proposed.

Research on Producing Low-power Low-voltage DC Power Supply with High-voltage Power Bus

The online monitoring equipment installed on the high-voltage power bus is supported by reliable and stable DC power, which cannot be obtained from industrial low-voltage AC power or chemical battery. This paper presents a circuit based on the principle of electromagnetic induction to obtain low-voltage low-power DC power supply from high voltage power bus. The circuit consists of energy-acquired coil, the rectifier and regulator circuit, and the shunt coils. This power supply can work with small current in the bus, also it can output stable DC voltage in the case of large current in the bus by starting shunt coil. The experimental data indicates that the output voltage of the power supply are 3.3V and 5V, the output power is greater than 120 mW and the bus starting current is less than 5A, all these can suffice for the online monitoring equipment.

Recovery Characteristics of Three-Phase Matrix-Type SFCL in Ground Fault

We investigated the recovery characteristics of a three-phase matrix-type superconducting fault current limiter (SFCL) with 1 × 3 matrix array. Recovery characteristics of superconducting units indicate that quenched superconducting units are returned from their normal state to their superconducting state. The recovery and rapidly quenching characteristics of the superconducting units are very important for the application of the SFCL in the power system. Through analysis of the recovery time, we confirmed that the recovery time of superconducting units in current-limiting part became shorter by increasing turn's number of the shunt coils in the trigger part to generate the magnetic field. From these results, we found that the power burden of the superconducting units was almost equalized because the difference between their critical currents was extremely reduced by magnetic field of shunt coils. Finally, the more the power burden or the absorption energy density of the superconducting units was equalized, the shorter the recovery time of its superconducting units was.

Quench Development in Bi-2212 Bulk Coils During Quenches

We investigated the quench development in resistive superconducting fault current limiters (SFCLs) based on Bi2Sr2CaCu2O8 (Bi-2212) bulk coils. In order to protect them from hot spot formation, the bulk coils were either attached with a metal shunt layer or connected with a shunt coil in parallel. The bulk coils also had a plastic support for enhanced mechanical strength and insulation. The SFCLs were subjected to simulated AC fault currents for quench measurements. They were immersed in liquid nitrogen during the experiment for effective cooling. The resistance of the Bi-2212 bulk coil stayed low for a few milliseconds, until it increased rapidly. The increase was more rapid in the SFCL with a shunt coil than with a shunt layer. Once the quench was completed, the resistance increased at slower rates. The average temperature of the bulk coil reached about 230 K at 3 cycles after quench start at application voltage of 2.4 Vrms/cm with a shunt coil, and at 0.4 Vrms/cm with a shunt layer. The resistance development in Bi-2212 bulk coils could be quantitatively explained with the concept of transfer of heat generated during quenches to the liquid nitrogen as well as within the Bi-2212 bulk. The fault period was divided into three regions: flux-flow region, region prior-to quench completion, and region after quench completion. Resistance was calculated separately for each region and compared with data. The results agreed well with data.

Theoretical Prediction of the Quench Behavior of a SFCL Module Having a BSCCO-2212 Bulk Coil and a Shunt Coil

This paper deals with theoretical prediction of the quench behavior for a superconducting fault current limiter (SFCL) module. The SFCL module consists of a monofllar type BSCCO-2212 bulk and a shunt coil made of copper or brass. The BSCCO-2212 bulk coil is placed inside the shunt coil, and they are connected in parallel. In order to analyse the quench behavior of the module, the equivalent circuit equation was first derived from the experimental circuit structure and then the partial differential equation was solved. The inductance values of the BSCCO bulk coil and impedance of the shunt coil are calculated by Bio-Savart and Ohm's formula, respectively. We computed the voltage and current behavior during quenches using those values, and compared the results with experimental short-circuit data for the SFCL module. Both computation and test results agreed well. Therefore, we conclude that the analytic result can be applied effectively to design of a SFCL module.

Fault Current Limitation Characteristics of Bi-2212 Bulk Coil With Different Types of Shunt Coils

We investigated fault current limitation characteristics of a resistive superconducting fault current limiter (SFCL) which consists of a Bi-2212 bulk coil and a shunt coil. For the experiments, different types of shunt-coils which had the same impedance were prepared. One group had high resistance, and the others were designed to have high inductance. The effects of the impedance component variation on current limitation characteristics of the SFCL were compared with each other. The test results showed that the SFCLs of both groups successfully limited the fault current of 7 kA <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rms</sub> to below 5 kA <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</sub> right after the fault occurred. The SFCLs with a shunt coil of higher inductance quenched more uniformly, but had a high voltage spike by Ldi/dt at the first half cycle after fault. On the other hand, the ones with higher resistance quenched comparatively less uniformly, but the voltage spike was much smaller. The impedance of the shunt coil is being optimized, taking into consideration stability, insulation, its effect on the circuit and other factors.

Optimum design of matrix fault current limiters using the series resistance connected with shunt coil

In this paper we described the improved design for the matrix fault current limiters (MFCL). To do this, we used thin film-type superconducting elements. therefore it means that we can make the MFCL with minimized size and high switching speed because of the high current density and the high indexing value of superconducting thin film. Also we could minimize the bulky shunt coil using the connection of a series resistance with a shunt coil. Also we could effectively block up a leakage current in shunt coils under no-fault condition and simply control total impedances of a current-limiting part using this method. After we designed an appropriated 1×2 basic MFCL module with an applied voltage of 160V, we enlarged it to a 2×2 MFCL module and a 3×2 MFCL module where applied voltages were 320V and 480V, respectively. Experimental results for our MFCL were reported in terms of various fault currents, variation of series resistance and so on. We think that these methods will be useful in the optimum design of an m×n MFCL.

Simulation model for a novel superconducting fault current limiter

A simulation model for a novel superconducting fault current limiter is presented. The components of the novel fault current limiter are melt cast processed BSCCO 2212 tubes with shunt coils wound around them, which are connected in parallel. The simulation model is based on the electrical and thermal equivalent circuits of a component. A corresponding system of state space differential equations describes these equivalent circuits, which are coupled through several variables. MATLAB is used to solve the state space differential equation system, incorporating the material properties of the bulk BSCCO 2212 as well as the copper coil. Through a comparison of the simulation results and measured data the introduced model is validated. With the simulation model, the design of the components for a fault current limiter can be further improved.

WELDING TRANSFORMER CONTROL BY THE ELECTRONIC CONTROL OF LEAKAGE FLUX

ABSTRACT In this paper, the triac is used to control the welding transformer leakage reactances and thus the welding currents. This new method keeps the input and output currents and voltages in sinusoidal wave forms. The triac is connected across the terminals of a coil wound on a fixed limb magnetic shunt. A simple triggering circuit is used to control the current of the triac and thus the current of magnetic shunt coil. This leads to variation of welding transformer leakage flux, leakage reactances and thus a variation of welding current. The distortion due to the triac is only affecting the leakage flux of the welding transformer. The leakage flux is very small (compared with main flux) and most of it passes in the transformer window. Then, no harmonic pollution in the bus–bar or in the welding transformer. Thus, high operating efficiency is obtained. This new method can be used with single or three phase are welding transformer. In this work, a three phase multi–operator welding transformer is experimentally checked with the new system. The recorded wave forms support the system advantages. Performance characteristics are experimentally measured and give adequate results.

Shunt protection for superconducting Maglev Magnets

Closely coupled, short-circuited shunt coils are proposed for quench protection of super-conducting Maglev magnets which use high resistance, matrix composite conductors. It is shown that, by suitable design, the shunts can reduce ac losses and that the changing currents during magnet energization or vehicle lift off and landing can be tolerated.

Extraction of the electron beam from a 30-MeV. synchrotron.

ELECTRONS of energy up to 20 MeV. have been extracted from the 30-MeV. synchrotron1 at the Atomic Energy Research Establishment with the aid of a small shunt coil carrying a pulse of current.