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We proposed a two-terminal-electrode vertical thyristor and investigated its suitability as a cross-point memory cell without a selector from the viewpoints of p+- and n+-base region width and a vertically stacked doped-epitaxial-Si layer structure such as p++-emitter/n+-base/p+-base/n++-emitter or n++-emitter/p+-base/n+-base/p++-emitter. The proper p+- and n+-base-region width (i.e., 160 nm) and p++-emitter/n+-base/p+-base/n++-emitter layer structure could enable the development of a cross-point memory cell using the half bias concept by preventing misfit dislocations at the junctions between the n++-emitter and p+-base or n+-base and p++-emitter. It was also found that generation of the misfit dislocations originating from B or P atom segregation at junctions during doped-Si epitaxial-layer growth enhanced the strain at the junctions. The misfit dislocations at the junctions were produced when the strain at the junctions was greater than ∼4 × 10−4. [ABSTRACT FROM AUTHOR]

Presents the cover/table of contents for this issue of the periodical. [ABSTRACT FROM AUTHOR]

A lot of large-scale industrial critical loads suffer from voltage interruptions and sags which can cause a significant financial loss. The thyristor-based solid-state transfer switch (STS) and mechanical-based automatic transfer switch (ATS) are used to protect loads against these power quality problems. However, the STS has a great deal of loss consumption because of the forward voltage drop of the thyristors, and ATS can hardly satisfy the voltage-sensitive load due to the long transfer time. This paper proposes a 400 V/1000 kVA hybrid ATS (thyristor switch in parallel with mechanical switch) (HATS) to realize low power consumption under normal situation and transfer fast when required. The proposed HATS has four transfer strategies which can be chosen according to different applications, it realizes the overlapping transfer of the neutral wire, and it can make a decision to transfer or not according to the different fault locations (transfer on the source side and not transfer on the load side). The design details of the prototype are presented, and laboratory tests and field experiments show the prototype good performance. [ABSTRACT FROM PUBLISHER]

A model of the turn-on spread has been developed for the axisymmetric configuration characteristic of the optical triggering of power SiC thyristors. Results for plane- and axisymmetric cases are compared. It is shown that the initial stage of the spread, during (2-3)τ , where τ is the current rise time constant for the thyristor turn-on, is characterized by a relatively low spread velocity, especially in the axisymmetric case. It is demonstrated that, even for a comparatively large thyristor structure, self-similarity conditions are not valid even for the plane case. [ABSTRACT FROM AUTHOR]

Shunt reactors are used to compensate the effects of line capacitance, particularly to limit voltage rise on open circuits or small loads. A magnetically controlled reactor is a device in which a DC pulsating through a special winding controls the inductive susceptance. Magnetically controlled reactors enhance transmission capability and save energy, especially in compact increased surge-impedance-loading power lines. The response of a thyristor-controlled reactor in voltage regulation to the voltage variations in a transmission line is faster than that of a magnetically controlled reactor. Although a magnetically controlled reactor can be designed to respond like a thyristor-controlled reactor in as little as 0.02 sec, the price of magnetically controlled reactor depends on its response time. In high voltage transmission lines, voltage variations are not sudden, so the slow response of the magnetically controlled reactor with respect to the thyristor-controlled reactor is not important. The main objective of this article is to compare magnetically controlled reactors and thyristor controlled reactors from a transient behavior point of view, and a detailed model of a magnetically controlled reactor reactor is used to illustrate the ideas presented throughout the article. [ABSTRACT FROM AUTHOR]

Abstract: In this paper both a method and apparatus are applied to different configurations of line-commutated ac/dc rectifiers to reduce the distortion of currents flowing from the ac supply. The load may be either inductive or capacitive. The technology involves an accurate shaping of the dc current by using two self-commutated switches. This dc-current shaping is reflected back into the shaping of the ac input currents, which become pure sine waves. Thyristor-based rectifying operation is possible with a simple control circuit, which is able to deal with both rapid load variations and failures in the self-commutated switches. Furthermore, the overlap conduction of bridge thyristors is eliminated completely. Experimental verification is provided from a 400-V 30-kVA 50-Hz laboratory prototype. [Copyright &y& Elsevier]

Inductive energy storage systems require opening switches which are technically much more difficult to realize than closing switches. Most advanced state-of-the-art semiconductor devices, namely, integrated gate-commutated thyristors, are capable of breaking currents on the order of 4 kA. However, the ISL has developed a high-power opening switch based on standard high-power thyristors and using. our so-called Inverse Current Commutation with Semiconductor devices (ICCOS) countercurrent commutation principle. These ICCOS opening switches, capable of interrupting pulse currents up to 28 kA, exploit the general property of thyristors, according to which falling short of the holding current puts the device into its blocking state. For this, a well-dimensioned countercurrent pulse is injected, via an elaborate circuit, into the thyristor which is in its conducting state. A 50-μF capacitor is used as the countercurrent pulse source, as well as a fast current-rise thyristor and a fast-recovery diode for the countercurrent subcircuit. The countercurrent energy stored in the dedicated capacitor is not lost in the switching process but fed into the load, in addition to the main-circuit energy. The achieved ICCOS switch-off time is about 30 μs. [ABSTRACT FROM AUTHOR]

The U.S. Army Research Laboratory has been exploring silicon and silicon carbide supergate turn-off thyristors (SGTOs) for high-power pulse switching required by Army survivability and lethality applications. Silicon SGTOs (3.5 cm²) were pulsed at 5 kA with a half-sine current waveform measuring 1 ms at the base. The recovery time, or Tq, of the devices was evaluated from the point at which the main current pulse fell to zero. Using a driver designed to provide both turn-on and turn-off signals, the Tq was reduced to 10 μs. Smaller silicon carbide SGTOs (0.16 cm²) were similarly evaluated for wide-pulse performance. They were switched several times at a peak current above 300 A, with an unassisted Tq time of 30 μs. This paper provides details of the aforementioned pulse switching as well as a description of continuing evaluations involving parallel devices and larger test beds. [ABSTRACT FROM AUTHOR]

This work presents the development of analytical models for thyristor-controlled reactors (TCRs). A nonlinear model for the TCR was developed based on the use of Generalized Switching Functions and from this model, a detailed linear model was derived. The linear model allows for the analysis and precise understanding of the behavior of the TCR under small disturbances both in the time and frequency domains, for frequency ranges up to some tens of hertz. This model clearly shows that the TCR dynamics are operating point dependent. System parameter variations are also correctly considered in the model. With the proposed model, it is possible to design static var compensators (SVC) controllers in an integrated form, avoiding risks of instabilities and guaranteeing a good overall dynamic performance for the system. Validation of the models was done by comparing simulated results obtained with the proposed model with those obtained with a traditional electromagnetic transients program (EMTP). [ABSTRACT FROM AUTHOR]

This paper presents a practical destruction-free parameter-extraction methodology for a new physics-based circuit simulator buffer-layer integrated gate-commutated thyristor (IGCT) model. Most key parameters needed for this model can be extracted by one simple clamped inductive-load switching experiment. To validate this extraction method, a clamped inductive-load switching experiment was performed, and corresponding simulations were carried out by employing the IGCT model with parameters extracted through the presented methodology. Good agreement has been obtained between the experimental data and simulation results. [ABSTRACT FROM AUTHOR]

Semiconductor switches are subjected to high voltage and high current simultaneously during turn-on and turn-off. A snubber is a set of components that reduce the stress on the power semiconductors during switching intervals and transient. This article reports on the design of snubbers for modified bridge using gate-turn-off thyristor (GTO) by-pass valves. The snubber gives switching stress reduction. It has better performance than other equivalent snubbers described in the literature. Both theoretical and experimental results are discussed in detail. [ABSTRACT FROM AUTHOR]

The basic stages of switching a high-power integrated thyristor controlled by an external MOSFET are analyzed qualitatively and quantitatively. The stage of switching delay is analyzed in terms of an analytical model the adequacy of which is verified by numerically calculating the current decay transient upon switching off the n + pnn’p +-structure. The effect of hyperdelay is discovered, which arises as the turned-off anode current approaches a limiting value depending on the parameters of the thyristor structure and control circuit. The specific energy losses are calculated, and it is shown that most losses are due to the current slow decay stage. [ABSTRACT FROM AUTHOR]

Compact high-action solid state switches are essential to weapon and protective systems for future Army vehicles. The Army Research Laboratory, Adelphi, MD, has been evaluating conventional and unconventional devices for an extended period of time. Large diameter thyristors have been explored and evaluated at currents in excess of 200 kA. Reverse dynistors, a Russian device, have shown even better performance than conventional thyristors due to their very fine gate structure (10-100s of microns). Fine gate structure leads to faster turnon, so that the switch is in full conduction much faster than those with more conventional gates, which vastly improves the reliability and lifetime of such devices. Silicon power corporation (SPCO) has produced a thyristor with an even finer gate structure than the dynistor. This super GTO (SGTO) also differs from conventional high-current thyristors in that it is modular rather than a single wafer design. Aside from a potential reduction in cost due to improved yield, the SGTO may be easily configured to produce the desired level of peak current by adding or subtracting individual chips in the module. This year, the Army Research Laboratory will obtain the first 400-kA SGTOs, which is double the prior current carrying capability of previous single wafer thyristors. A more critical parameter will be an increase of di/dt on turn-on by an order of magnitude. Single wafer thyristors of large diameter have had di/dt measured in kA/us. The objective of the SGTO switch is in excess of 40 kA/us. This paper presents the first experimental data from a prototype device, rated at 80-kA peak current. Data from this round of evaluation will provide critical design data for the realization of switch modules of 400 kA and beyond. [ABSTRACT FROM AUTHOR]

The present paper describes a converter where both series and parallel resonant circuits are used. In order to minimize losses, switching is made at zero current crossover (ZCS). The converter described in this paper has four MOS-controlled thyristor (MCTs) in H-bridge configuration (Full bridge). It is used for an induction cooking-range with two hot zones. The switching frequency is 50 kHz. To optimize the system efficiency, different control strategies are discussed. [ABSTRACT FROM AUTHOR]

A technique to achieve an efficient and low cost unity power factor for a three-phase controlled rectifier is described. The proposed technique can be used to retrofit a variety of thyristor converters for various applications. It consists of a thyristor bridge, three bidirectional switches, and a current shaping network. The bidirectional switches are turned on at double the line frequency of 50 Hz. Its current shaping network is very simple and consists of only two capacitors and three resistors. The scheme provides a simple, light, fast and economical upgrading to the existing controlled rectifier-based DC drives. In general, it is also suitable for medium to high power AC-DC converters used in UPS, HVDC, etc. [ABSTRACT FROM AUTHOR]

Discrete wavelet transform is used to analyze faulty signals for a transmission system employing a thyristor controlled series capacitor at the midpoint of a line. Different frequency components of current signals are considered to select the phase(s) involved with a fault. To identify the fault section the new approach utilizes the difference in high frequency components of the current signals. For both phase selection and section identification tasks new energy and standard deviation-based indices are also calculated for the transmission system. [Copyright &y& Elsevier]

Application of the third harmonic current injection in three-phase full-bridge thyristor rectifiers is analyzed. Spectra of the rectifier output terminal voltages are derived. Results of the optimal current injection for diode bridge rectifiers are generalized for the thyristor rectifiers, and the waveform of the optimal injected current is derived. It is shown that for the optimal third harmonic current injection, the current injection network takes 8.571% of the rectifier input power from the thyristor bridge output terminals, regardless the thyristor firing angle. A current injection network with a passive resistance emulator that provides recovery of the power taken from the thyristor bridge output terminals is proposed. Volt-ampere ratings of the magnetic components are derived. An algorithm to control the switches in the resistance emulator is presented. Analytically obtained results are experimentally verified. [ABSTRACT FROM AUTHOR]

A misfire phenomenon taking place in a discharge circuit composed of a capacitor and thyristor has been investigated. This circuit was operated at a frequency of up to 198 Hz. A misfire was observed in a circuit with a PET capacitor at low temperatures, while no misfire was observed with a PP capacitor under any conditions. Transient currents in the range of 40 A to 1 mA were measured with a digital oscilloscope. In the case of a PET capacitor, the current initially decreased exponentially at a given time constant, but exhibited a slow decay which caused the misfire. This current is associated with residual charges trapped in the bulk of the PET film. © 2001 Scripta Technica, Electr Eng Jpn, 137(2): 1–7, 2001 [ABSTRACT FROM AUTHOR]

Chaotic behaviors are observed in the anode current of the thyristors where their anodes were excited with an ac source and the constant dc current was supplied to the gate. Three aspects of chaos, i.e., period-doubling bifurcation, intermittency, and period-adding chaotic sequence, are observed with different combinations of control parameters. This paper discusses primarily the feature of period- adding chaos accompanied with intermittency. Also reported is the structure of its bifurcation by using a simple first return map model constructed from the experimental results. [ABSTRACT FROM AUTHOR]

For pulsed power systems such as lasers and accelerators, semiconductor switches with their longer service life have actively been developed as replacements for thyratrons. The MOS-driven thyristors are suitable for pulsed power applications because they have high-power handling and fast turn-on capabilities. The MOS-assisted gate-triggered thyristor (MAGT), designed especially for pulsed power, is a promising candidate in this field. This paper presents the results of an investigation into the performance of MAGTs. Using a pulse-forming network (PEN), the pulse-switching characteristics and the dynamic resistance characteristics during the current flow are investigated. A maximum current density of 21.8 kA/cm² and di/dt of 106 kA/μs/cm² with 1550-V anode voltage on a single-shot basis were obtained. Furthermore, a life test with 109 shots at a high repetition rate showed no degradation in the observed characteristics. Based on these experimental results, a carrier flow model of MAGT during turn-on process is proposed and the turn-on mechanism is considered. [ABSTRACT FROM AUTHOR]

Two design methods of ac/dc thyristor converter current control systems with MRAC (Model Reference Adaptive Control) have been designed, To linearize the input/output relation of the systems, the constant term of the model is considered in different ways. In the first method, a linear transformation of the control input is made while in the second method, the constant term and compensated modeling error are neglected by integral adaptation. Computer simulations and experiments have shown that the control performances of the MRAC systems are much better than that of PI controllers. However, in the first method, since the variable vector is not persistently spanning, the convergence rate of estimated parameters is not as high as expected. The second method has better dynamic characteristics but its stability has not been proved in theory. This paper suggests a new design method in which the constant term is considered as a deterministic disturbance. The feature of this method is that by introducing an equality equation which makes the term of disturbances apparently unobservable, the effect of disturbances can be eliminated and the existing adaptive control scheme without disturbances whose stability has been proved theoretically can be used. Computer simulations and experiments show that the new method can obtain better responses than the old ones. [ABSTRACT FROM AUTHOR]

The switching of high-voltage (1.5 kV) 4H-SiC thyristors by the dV/dt effect has been investigated for the first time in the temperature range from 300 to 504 K. At a rise time of the forward bias V(t) equal to 30 ns, the characteristic bias at which the structure under investigation can be switched on by the dV/dt effect decreases steadily from 289 V at room temperature (dV/dt ~ 9.7 kV µs-1) to 137 V at T = 504 K. The characteristic value of the critical charge per unit area, Qcr, is ~1.9 × 10-7 C cm-2 at room temperature and also decreases steadily as the temperature increases. [ABSTRACT FROM AUTHOR]