High Current Low Voltage Research Articles

풀브리지 컨버터를 갖는 1[kW] 연료전지 시스템 스위치 병렬 특성 분석

Fuel cell system which can solve the environmental problem is receiving attention. To use utility power necessary power conversion system from low voltage that is generated by fuel cell system. because fuel cell has special characteristic of low voltage high current. To improve PCS's efficiency the paralleling method is used. Available the method could reduce the switching loss. But the existing research could not be found optimal result and accompanying several effects. In this study analysis several effects causing the parallel method. The effects have been demonstrated through simulations and experiments.

Arc root mobility on piezoelectrically actuated contacts in miniature circuit breakers

A novel contact opening mechanism has been developed using a piezoelectric actuator to open the contacts in a low contact opening velocity circuit breaker. The arc control on the contacts is critical for successful current interruption (10/sup 3/-10/sup 4/ A) in low voltage (<250V) devices. Previous work has shown how arc root commutation from the contact region into the arc chamber is affected by arc chamber materials, contact materials and the gap behind the moving contact for contact velocities between 1ms/sup -1/ and 10ms/sup -1/. This work is extended using a commercially available piezoelectric actuator to open the contacts. Contact opening speeds are assessed and the arc root mobility is characterized under this operating regime. A flexible test apparatus and solid-state high-speed arc imaging system are used to gather data on the arc root during the opening of the contacts. New experimental results are presented on the anode and cathode root velocity and arc root motion in an arc chamber with piezoelectrically actuated contact opening. These results can be used to improve the design of high current low voltage circuit breakers suitable for piezoelectric actuation.

Recent achievements and approaches for further optimization of high current low voltage power semiconductor components

Recent achievements and approaches for further optimization of high current low voltage power semiconductor components

Advanced power semiconductors and ICs for DC/DC converter applications

This paper describes recent advances in power semiconductor devices, integrated circuits, and packages for DC/DC converter applications. Special emphasis is placed on the latest discrete power MOSFET devices and packages. Features and trends in ICs for control of synchronous buck converters are highlighted as well. The paper will also cover a new class of miniaturized hybrid assembly that sets new efficiency standards for high current low output voltage applications.

MOCVD grown δ-doped InGaP/GaAs heterojunction bipolar transistor

An InGaP/GaAs heterojunction bipolar transistor (HBT) with an 50A undoped spacer and δ-doped sheet at B-E heterointerface is fabricated and studied. A common-emitter current gain of 280 and an offset voltage as small as 55mV are obtained, respectively. This results show that high current gain and low offset voltage can be attained simultaneously without the passivation of E-B junction. From the experimental results, it shows that the potential spike is indeed reduced by the employment of an δ-doped layer simultaneously.

Leakage current of Al- or Nb-doped Ba0.5Sr0.5TiO3 thin films by rf magnetron sputtering

The effects of Al and Nb doping on the leakage current behaviors were studied for the Ba0.5Sr0.5TiO3 (BST) thin films deposited on Pt/Ti/SiO2/Si(100) substrate by rf magnetron sputtering. Al and Nb were selected as acceptor and donor dopants, respectively, because they have been known to replace Ti-sites of the BST perovskite. The BST thin films prepared in situ at elevated temperatures showed relatively high leakage current density and low breakdown voltage. However, the BST thin films deposited at room temperature and annealed subsequently in air showed improved electrical properties. In particular, the leakage current density of the Al-doped BST thin film was measured to be around 10−8 A/cm2 at 125 kV/cm, which is much lower than those of the undoped or Nb-doped thin films. The results suggest that the Schottky barriers at grain boundaries in the film interior could determine the leakage behavior in the BST thin films.

δ-doping InGaP/GaAs heterojunction bipolar transistor

An InGaP/GaAs heterojunction bipolar transistor with a 50 undoped spacer and δ-doping sheet at base-emitter heterointerface is fabricated and studied. A common-emitter current gain of 280 and an offset voltage as small as 55 mV are obtained, respectively. These results shows that high current gain and low offset voltage can be attained simultaneously without the passivation of the emitter-base junction. The experimental results show that the potential spike is reduced by the employment of a δ-doped layer simultaneously. On the contrary, theoretical consideration also shows that the potential spike vanishes by inserting a δ-doping sheet between the emitter-base heterointerface.

Simulation of a non conventional high current low voltage power converter with EMTP

This paper presents, a novel, non-conventional 24-pulse converter for low-voltage high current applications based on a peculiar series connection of the primary zigzag windings. Simulation results confirmed experimental results and allowed second order phenomena to be taken into account. Even though EMTP software was not intended to simulate such a converter, it has been successfully used, showing to be a powerful simulation tool even in complex power-electronics systems.

High current density triode magnetron sputtering

There have been many attempts to use triode arrangements to improve sputtering systems. We present a version where the auxiliary cathode is not used to change the sputtering discharge but to create activated reactive ion plating conditions on the substrates. The system uses a high current density low voltage electron beam to activate metal vapour and reactive gases. The different geometric arrangements are presented. The electric and kinetic characteristics of the system are described and shown for the example of nitride deposition.

A theoretical model of the mercury and copper vapour arcs

A model of the vapour arc is proposed which reconciles the characteristics of very high current density and low voltage drop. Two methods of electron emission are suggested to account for the exceptional current density: emission by excited atom bombardment, and thermionic field emission. The relative importance of these two processes is examined. In addition, account is taken of the effects of the transfer of ion momentum to the gas in the arc spot and the overall energy balance. The relationships derived from these mechanisms enable a quantitative description of the parameters of the arc spot to be made which only depends on the basic constants of the cathode material. Values of the arc parameters calculated for the mercury and copper arcs agree well with experimental measurements.

Duoplasmatron Ion Sources

A survey on questions related to the production of multiply charged ions with the Duoplasmatron ion source is given. In spite of differences of the multiply charged ion source and the mass separator type, design considerations show that high containment is a common feature to be attained in both subjects. Multiply charged metal ions are produced by material evaporation into the magnetically confined anodic plasma and auxiliary gas feed into the cathode discharge regions. Energy spreads of ion beams from the low and the high arc current source are compared. The Duoplasmatron ion source proves to be a hygieneous source of high containment that permits the production of medium charge states up to 9+ for xenon at modest energy spread and good brilliance of the extracted ion beam in a high current-low voltage discharge mode.

Flux Pumps for Use at 60 Hz

Many superconducting devices now being built require currents of a thousand or more amperes. When the currents needed are dc and large compared with the heat leakage into the cryostat from sources other than the electrical leads, it may be advantageous to use a flux pump or ac-to-dc converter within the dewar for powering the device. The flux pumps described convert low current-high voltage ac power into high current-low voltage dc power. Pumps designed to operate in the 500 to 1200 A range at 5 to 50 W will be discussed.

A new approach to the small accelerator vacuum system

The incorporation of a titanium bulk sublimator in combination with a getter ion pump in a small accelerator vacuum system is shown to provide major advantages in pumping performance, reduction of the tritium hazard, and improvement in system reliability. A mode of operation is suggested for the sublimator which can greatly increase sublimator lifetime. Typical operating data for the vacuum system of a 300 kilovolt accelerator equipped with a sublimatorlion pump combination are presented. A proposal for the adaptation of a comparable vacuum system to a standard 150 kilovolt accelerator is made. Conclusion A combination of a titanium bulk sublimator (TBS) and a getter-ion pump has been applied to the vacuum system of a 300 kilovolt accelerator used for the production of neutrons and offers the following advantages: (1) Routine pumpdown from atmosphere to 10−7 torr in 1 hour. (2) A variable pumping speed of from several litres/sec to over 17,000 litres/sec depending upon pumping requirements for H2, O2, N2, CO and H2O. (3) It is estimated that a 400 gram loading in a TBS should last for 3½ years in a 300 kilovolt machine and over 10 years in a 150 kilovolt vacuum system. (4) System is completely sealed and provides for controlled venting for tritium absorbed during rough pumping. (5) Tritium released from the target is permanently buried in the walls of the sublimator as titanium tritide thus reducing substantially the hazard associated with pump maintenance. Operation of the titanium sublimator in the region where the deuterium gas leak into the vacuum system matches the diffusion of deuterium into the titanium substrate can signifi- cantly extend the life of the TBS. Use of this design criteria should prove extremely valuable when applied to high current low voltage accelerators that use highly loaded tritium targets.

High Current Low Voltage Electron Bombarder for Excitation of a Molecular Beam

An electron bombarder for producing intense beams of metastable atoms and molecules has been constructed and operated. The cathode is a 1×5 cm nickel matrix with a BaSrO coating. It has been found to resist poisoning by a variety of gases. The anode consists of 10 parallel channels, each 0.1 cm wide, 5 cm long, and 1 cm high. Anode currents of up to 380 mA at 20 V have been obtained. Beams of N2, helium, and argon have contained approximately 1011 metastables/sec.

The effects of lateral injection and base-widening on the high current-low voltage characteristics of transistors

The common emitter I C  V CE characteristics of double-diffused transistors at low collector-to-emitter biases are discussed. The observed decrease in emitter-to-collector resistance is qualitatively described by existing models for base-widening and lateral injection. The quantitative nature of the reduction in resistance depends on the bulk lifetime and dimensions of the transistor. The decrease in resistance is shown to take place prior to the onset of saturation.

Thermal instability in power transistor structures

A time-dependent formulation is obtained for the two-dimensional heat-flow problem applied to a model for an interdigited power transistor structure. The treatment predicts that lateral thermal instability can arise at high power densities from the interaction of a local temperature rise within the transistor volume with the temperature dependence of the emitter current. A solution is offered which permits calculation of the effect of transistor design on the tendency toward thermal instability. It is seen that the presence of series emitter and base resistance can significantly improve device stability, especially at high currents where the dynamic emitter resistance becomes small and these resistances tend to limit the emitter current. This partly explains the more stable transistor operation at a given power level observed at high current-low voltage compared to high voltage-low current. Lateral instability can cause an order of magnitude reduction in the power-handling ability of a transistor compared to the case where only steady-state heating and maximum junction operating temperature are considered. A many-fold improvement in power capability is calculated for a transistor with emitter heat-sinking rather than the more conventional collector heat-sinking.

Measurement of Arc Resistance by Chemical Flame

Concerning arc resistance of electric insulating materials, development of a reasonable and simple method of testing was recommended for consideration. Taking the deterioration in the low voltage high current arc to be due to the deterioration of its energy source, which was thought to be the low voltage high current arc itself, the bunsen burner was used for the thermal energy source, considering that the equivalent energy source was not to be necessarily confined to electric thermal energy source, but the use of simple energy source such as chemical flame might as efficiently substitute. The test insulator was held horizontally at a constant distance from the nozzle of the burner, and was subjected to deterioration. Then the temperature of the part of the flame which was in contact with the insulator was fixed at 1000°C and at the distance of 50mm. from the nozzle in this condition. The length of the flame was kept at about 70mm. constantly. And then the degree of deterioration was examined by measuring the post-test surface resistance. The two surface resistances, pre-test and post-test, were compared, and the ratio of the lowering determined the character of the deterioration and of the arc resistance.The above mentioned subject was also studied from the point of arc resistance test by low voltage high current. The comparative studies were carried out smoothly. The measurement agreed fairly with the results of various other arc resistance tests by low voltage high current. The present test has thus proved a practical method.

The influence of the initial conditions on the pumping properties of the molecular sieves: P Lukác̆, Department of Experimental Physics, Komenský University, Bratislava, Czechoslovakia

The incorporation of a titanium bulk sublimator in combination with a getter ion pump in a small accelerator vacuum system is shown to provide major advantages in pumping performance, reduction of the tritium hazard, and improvement in system reliability. A mode of operation is suggested for the sublimator which can greatly increase sublimator lifetime. Typical operating data for the vacuum system of a 300 kilovolt accelerator equipped with a sublimatorlion pump combination are presented. A proposal for the adaptation of a comparable vacuum system to a standard 150 kilovolt accelerator is made.A combination of a titanium bulk sublimator (TBS) and a getter-ion pump has been applied to the vacuum system of a 300 kilovolt accelerator used for the production of neutrons and offers the following advantages:(1) Routine pumpdown from atmosphere to 10−7 torr in 1 hour.(2) A variable pumping speed of from several litres/sec to over 17,000 litres/sec depending upon pumping requirements for H2, O2, N2, CO and H2O.(3) It is estimated that a 400 gram loading in a TBS should last for 3½ years in a 300 kilovolt machine and over 10 years in a 150 kilovolt vacuum system.(4) System is completely sealed and provides for controlled venting for tritium absorbed during rough pumping.(5) Tritium released from the target is permanently buried in the walls of the sublimator as titanium tritide thus reducing substantially the hazard associated with pump maintenance. Operation of the titanium sublimator in the region where the deuterium gas leak into the vacuum system matches the diffusion of deuterium into the titanium substrate can signifi- cantly extend the life of the TBS. Use of this design criteria should prove extremely valuable when applied to high current low voltage accelerators that use highly loaded tritium targets.

A method for testing and establishing the rating of semi-conductor rectifiers under dynamic conditions

Owing to the combination of high current density and low forward voltage drop in the rectifying junction of a semi-conductor rectifier, the physical size and thermal capacity for a given rating are low, so that the current on overload can be much greater than for other types of rectifier. Consequently, the junction-temperature rise on overload is extremely rapid, and in some cases considerable temperature fluctuations occur at mains frequency. It is therefore necessary to be able to monitor the junction temperature dynamically (i.e. under working conditions at mains frequency) and to observe the rise of temperature with time. A further necessity for dynamic testing occurs since the measurement of the forward characteristic at high current by d.c. methods can result in excessive heating and possible failure. In the apparatus to be described the separation of forward and reverse half-cycles is secured by means of a synchronous commutator, permitting independent measurement of forward and reverse current and voltage at mains frequency, and hence continuous indication of junction temperature. Operation of the rectifier at full rating without expenditure of the full power necessary to accomplish this by direct methods is also possible. This is particularly useful in life testing large numbers of semi-conductor rectifiers. Limited experience indicates that this method of testing provides operating conditions which are in all ways identical to those which a device experiences under fullload conditions

Resistance Sintering Under Pressure

Resistance sintering under pressure is a method of hot pressing in which a powder compact is subjected to pressure and simultaneously heated by passing a low voltage high amperage current through it. Equipment for this process is described. Its basic characteristics such as resistance requirements for powders and compacts, temperature distribution in compacts, and gas reactions during resistance sintering are discussed. Examples of the sintering process in compacts made of a single metal or an alloy powder and in compacts made of mixtures of powders are presented. Potential commercial applications of the process are evaluated.