GTO thyristor commutation of DC machine

A large-capacity inverter using high-power gate turn-off (GTO) thyristors that can be used instead of a cycloconverter in AC drives is presented. With the techniques of multiple configuration and GTO series connection, the inverter capacity is increased effectively. High conversion efficiency is obtained by using low-loss snubber circuits for GTOs. It is confirmed that the low-loss snubber circuits using energy recovery units (ERUs) have good performance in pulse-width modulated (PWM) operation. High-energy recovery efficiency is obtained, especially in leading operation (turn-on operation when freewheeling diodes conduct). These snubber circuits have superior ability for clamping overvoltage at GTO turn-off. A 2750 kVA inverter with low-loss snubber circuits using high-power GTOs has been fabricated and evaluated. >

New devices that are challenging the silicon-controlled rectifier are considered. Among them are the high-power bipolar-junction transistor (HPBT), the power MOS field-effect transistor (MOSFET), the gate turnoff (GTO) thyristor, and the insulated-gate bipolar transistor (IGBT), sometimes called a conductivity-modulated field-effect transistor (COMFET). Also important are the static-induction or short-channel junction-effect transistor, and its cousin, the static-induction thyristor. Applications for these devices are outlined, and their characteristics are briefly sketched. The use of MOSFETs in automobiles and IGBTs for motor drives is examined in more detail. Packaging issues are discussed.

A system for measuring the subthyristor parameters of GTO (gate-turn-off) thyristors is presented. With the aid of a personal computer the gate breakdown voltage and leakage current, the turn-on and turn-off times, and the forward voltage drop of each subthyristor can be automatically measured, stored, and statistically evaluated. The cumulative frequency and distribution of the gate breakdown voltages on an ordinary pellet are discussed. A further example shows the distributions of gate breakdown voltage and turn-off times on a pellet with a doping inhomogeneity.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Gate turn off thyristor (GTO) gating circuits, especially off-gating circuits, are the most important for reliable operation of GTO equipment. This paper describes a new gating circuit for high power GTO of 600A class. The off-gating circuit can provide a negative pulse of 200A with its rate of rise of 30A/us. Its power dissipation decreases to 20 percent of a previous type. The on-gating and negative bias circuits are also described.

The electrothermal behavior of a 1200V-30A gate turn-off (GTO) thyristor operating in its electrical circuit has been studied using two-dimensional (2D) simulation tools. The program realized for this purpose uses a combination of Silvaco tools and takes into account the thermal environment of the GTO. It was validated by direct experimental measurements. The studied GTO is a silicon device with a symmetrical doping profile (N+PN−P+). It operates in a dc-dc converter at a 400 Hz commutation frequency, its conduction time is in the range of 0.05–0.25 ms. The thermal environment of the device is reproduced by including its thermal parameters and those of its package in the calculation, the simulation accounts, then, for all the thermal generation and conduction in the device. The simulation program was validated by comparing the electrical parameters (anode and gate currents, anode–cathode voltage, and dissipated power) of the GTO, obtained in the same operating conditions, by both simulation and direct measurements. The transient behavior of the GTO during its turn-off at a nanosecond scale was then obtained. We first obtained the 2D time-dependent distribution of most of the internal electrical parameters (carriers, current density, …); then we obtained the 2-D time-dependent distribution of temperature inside the GTO.

The gate turn-off (GTO) thyristor has the highest voltage and current rating among the semiconductor power switches used extensively today. The insulated-gate bipolar transistor (IGBT) is used to improve switching performance of a GTO in a cascode switch. This paper documents the switching performance of the different power semiconductor devices used in an IGBT-gated GTO-cascode switch. The cascode switch was tested and simulated using SPICE. Experimental waveforms are presented and show good agreement with simulation results.

The use of an insulated-gate bipolar transistor (IGBT) to improve the switching performance of a gate turn-off (GTO) thyristor in a cascode switch is documented. The IGBT-gated GTO-cascode switch features simple drive requirement, fast switching, robustness, and overcurrent protection. The cascode switch was applied in a quasi-resonant buck power converter and simulated on a computer using PSpice. The IGBT-gated GTO-cascode switch is suitable for high-power (1200 V, 140 A) and high-frequency operation up to 30 kHz. The turn-off time of the main switch, GTO, is reduced significantly due to the reverse current gain of unity in cascode configuration.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

In view of the many system planning uncertainties faced by the UK National Grid Company (NGC), there is a clear need for readily relocatable reactive power compensation systems with enhanced system performance. To date 12 relocatable SVCs (RSVCs) have been installed as part of a planned programme of work to meet these changing system needs. Developments in the rating capabilities of gate turn-off (GTO) thyristors have enabled power electronic converters using GTOs to be proposed as serious competitive alternatives to the well proven thyristor controlled reactor (TCR) and thyristor switched capacitor (TSC). GTO-based STATCOM convertors have a number of benefits which are of value to NGC, such as reduction in required site area and ease of relocation. The authors describe the East Claydon project, which is viewed as an important step towards long-term objectives which could see the deployment of a range of compact power electronic devices on NGC's system.

The authors describe a system using PWM (pulse-width modulation) control converters and induction motors to control a load power of 1200 kW. GTO (gate turn-off) thyristors are used for a practical power circuit, and a microprocessor in combination with DSP (digital signal processing) control is used to configure the control circuit. It is shown that by switching GTO thyristors using DSP with a sample time of 32 mu s, current control can be continued without any problems when asymmetrical flux saturation occurs in the transformer. This device has been developed with a view to application in high-speed railway systems. >

4H-SiC gate turn-off (GTO) thyristor offers extraordinary advantages over its counterparts in handling ultra-high voltage electric power conversion applications because of its relatively low forward voltage drop at high conduction current density. Besides, though the SiC thyristors never suffer from long carrier liftime induced large switching loss like Si thyristors, the peak temperature rise rather than dynamic avalanche breakdown is blamed for the safe operation area (SOA) failure, making further reduction of power loss in SiC GTOs even more important. In this paper, a 20 kV SiC GTO with direct carrier extraction access to its drift region (DA-GTO) is investigated to explore the benefit this structure could bring for SiC thyristors, namely achieving smaller switching loss and/or potential larger SOA with slight sacrifice in forward voltage drop at high current. The structure is formed by interleaved P+ ion implantation into part of the thin N-injector layer based on conventional 20 kV SiC GTO. The SiC DA-GTO operates in BJT mode at low current, and in GTO mode with low forward voltage drop at high current. During turn-off process, it offers a direct current path to quickly sweep out the excess carriers in the P-drift region, thus speeds up the turn-off process and decreases the turn-off loss. Simulation results show that its turn-off loss reduces by 37.4%, contributing to 12.6% reduction in total power loss, compared with SiC GTO. Therefore, SiC DA-GTO is a very promising choice for next-generation power conversion systems.

Highly integrated field emitter arrays (FEAs) have been fabricated by the transfer mold technique to obtain highly uniform and stable field emission for highly efficient and reliable vacuum microelectronic devices. Transfer mold Mo FEAs containing 9,400,000 emitter tips with high emitter density of 7,840,000 tips/cm2 have demonstrated a low value of less than 0.7%. Highly uniform, and flickerless fluorescence has been observed in the entire area of the fluorescent screen corresponding to the FEAs. The principle of the vacuum microelectronic switching devices has been proposed and experimentally verified by applying a high anode voltage of ±1 kV, which will be capable of decreasing the size and the electric power loss of the high voltage electric power converters using conventional semiconductor devices such as light-triggered thyristors (LTT) and gate turn off thyristors (GTO) to less than 1/100 and 1/10, respectively.

Chapter 2 - Power Semiconductors

This paper presents the experimental results of stabilization of a model power transmission system by using a Superconducting Magnet Energy Storage (SMES). The SMES, which was composed of two sets of GTO (Gate Turn Off thyristor) power converters and a superconducting coil, is capable of controlling active power (P) and reactive power (Q) simultaneously in four quadrants by changing the firing angles of power converters. The model power transmission system was designed to simulate the behavior of a real scale long distance bulk power transmission system with voltage of 500 kV, capacity of 2000 MVA and length of 280 km. In this study, we have experimented power system stabilizing control by applying P-Q simultaneous control ability of SMES. From the results of experiment it was demonstrated that stabilizing effect by means of SMES is very significant.

Over the last few years high power semi-conductor devices with intrinsic turn-off capability have become available. These devices, called gate turn-off (GTO) thyristors, consist of several layers of silicon with appropriate dotations; they are able to turn off currents of 1000 Amperes at thousands of volts within microseconds. In circuits used in power electronics the usual resistive, inductive and capacitive circuit elements are combined with thyristors which may simply be considered as switches. This technology is still an active field of research, and it has many important applications such as AC/DC conversion (both ways), speed control of locomotives and electric cars, control of power stations and power networks, etc.

Ultra-high voltage (>10 kV) power devices based on SiC are gaining significant attentions since Si power devices are typically at lower voltage levels. In this paper, a world record 22kV Silicon Carbide (SiC) p-type ETO thyristor is developed and reported as a promising candidate for ultra-high voltage applications. The device is based on a 2cm2 22kV p type gate turn off thyristor (p-GTO) structure. Its static as well as dynamic performances are analyzed, including the anode to cathode blocking characteristics, forward conduction characteristics at different temperatures, turn-on and turn-off dynamic performances. The turn-off energy at 6kV, 7kV and 8kV respectively is also presented. In addition, theoretical boundary of the reverse biased safe operation area (RBSOA) of the 22kV SiC ETO is obtained by simulations and the experimental test also demonstrated a wide RBSOA.