Gating circuit developed for high power thyristors

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.

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.

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>

The series resonant DC-link inverter is an attractive circuit topology for interfacing a DC current with a three-phase AC system. It uses gate turn-off thyristors (GTOs) as semiconductor switches. The conventional solution requires an additional series diode to perform the turn off process and to enable forward recovery of the GTO. This paper uses a single GTO along with a special gate drive to provide reverse and forward recovery. A new device testing circuit was designed to create the same electrical and thermal stresses as in a series resonant DC-link inverter. Experimental results using 2000 A GTOs at 26 kHz switching frequency demonstrate that the total device losses are reduced, while the hold-off time is slightly increased. The new single-device solution makes resonant switching attractive for very high-power applications.

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.

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. >

The authors review the fundamental mechanism by which rotating electrical machines develop torque and draw conclusions as to which configuration offers inherent advantages in this regard. Development of a DC machine with a continuous armature winding where gate turn-off (GTO) thyristors replace the traditional copper-segment-carbon-brush commutator is described. Operation of a separately excited machine with 12 armature tapping points and 18 GTO thyristors is demonstrated, and waveforms are presented to illustrate the switching duties involved. >

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.

The authors present the description, steady-state modeling, and filter design of a double-inverter PWM (pulse-width-modulated) solid-state synchronous condenser (SSSC) for reactive power compensation. The proposed scheme integrates the advantages of PWM selective harmonic elimination modulation (SHEM) and harmonic cancellation by transformer connection (HCTC) to minimize the filtering requirements. The key feature of the proposed double-inverter SSSC system is the low-switching frequency of the PWM pattern, which allows the utilization of high-power GTO (gate turn-off) thyristors (f/sub sw,max/=420 Hz). A series of PWM switching patterns in the low-switching frequency range that is most suitable for high-power GTO thyristors is presented. The performances of the SSSC for these PWM patterns are compared. Other figures of merit for the system, such as filter design and system derating, are discussed. The steady-state waveforms of the compensator current for single- and double-inverter SSSC systems are compared.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The control of high voltage at high power, particularly opening switches, has been difficult in the past. Using gate turnoff thyristors (GTOs) arranged in series enables large currents to be switched at high voltage. A high voltage opening switch has been successfully demonstrated in our Laboratory. This switch uses GTOs in series and successfully operates at voltages higher than the rated voltage of the individual devices. It is believed that this is the first time this has been successfully demonstrated, in that GTDs have been operated in series before, but always in a manner as to not exceed the voltage capability of the individual devices. In short, the devices have not worked together, sharing the voltage, but one device has been operated using several backup devices. Of particular interest is how well the individual devices share the voltage applied to them. Equal voltage sharing between devices is absolutely essential, in order to not exceed the voltage rating of any of the devices in the series chain. This is accomplished at high (microsecond) switching speeds. Thus, the system is useful for high frequency applications as well as high power, making for a flexible circuit system element. This demonstration system is rated at 5 KV and uses 1 KV devices. A larger 24 KV system is under design and will use 4.5 KV devices. In order to design the 24 KY switch, the safe operating area of the large devices must be known thoroughly.

The Large Capacity Voltage Source Inverter (LCVSI) application started early 90's. The inverters are getting old and are beginning to be replaced with more recent drives. In March of 2010, a contract was awarded to replace the existing GTO (Gate Turn-Off thyristor) Inverter drives applied to cylindrical rotor synchronous motors on a two stand reversing cold rolling mill. New IEGT (Injection Enhanced Gate Transistor) drives were applied on the two rolling stands and both tension reels. Previous voltage source inverter was the GTO Inverter. Previous synchronous motor applications had been with salient pole type synchronous motor. The differences between GTO inverter and IEGT inverter are discussed. Cylindrical rotor and salient pole motor, design considerations for application of large scale voltage source inverters to cylindrical rotor motors, and results obtained during testing and commissioning are discussed.

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.