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Principles of Energy Conversion
Published in Hamid A. Toliyat, Gerald B. Kliman, Handbook of Electric Motors, 2018
Hamid A. Toliyat, Gerald B. Kliman
The thyristor appeared quite early in the development of semiconductor devices. This device, also known as the SCR, was an early replacement for the thyratron and later, as the capabilities of the device were improved, as a replacement for the controlled mercury arc rectifier, the ignitron. However, the thyristor has the same limitation as the thyratron and the ignitron in that once conduction has been initiated by the control electrode it can be terminated only by reducing the anodecathod voltage to a very low level or by reversing it. That is, the control electrode has turn-on capability, but no turn-off capability. In the five remaining devices, the control electrodes have both turn-on and turn-off capability.
Introduction
Published in Gourab Majumdar, Ikunori Takata, Power Devices for Efficient Energy Conversion, 2018
Gourab Majumdar, Ikunori Takata
In 1955 Japanese National Railways fabricated an experimental AC drive locomotive “ED45” using three DC motors of total 1 MW output capacity driven by four ignitrons, which were constructed by a single-phase bridge rectifier on the secondary low tap-voltage output terminals of a 20 kV AC transformer. The ignitron used was a water-cooled single-phase mercury rectifier having an improved ignition method, and it needed a mercury-vapor diffusion pump and a rotary pump to maintain a specific vacuum level in the iron container. Then in the world’s first universal locomotive “EF30” series, which were made starting from 1960, the single-ignitron system was replaced by twenty 700 V/200 A silicon (Si) diodes connected in a 10-in-series and 2-in-parallel circuit architecture. The very first series, Shinkansen bullet trains, which came up in 1964 used a control system as that of “EF30”3 except that the overhead wire supply voltage was as high as 25 kV. In the Sakuma frequency conversion facility (300 MW) that operated from 1965, 26 mercury rectifiers of 125 kV/1.2 kA were used until 1993. A real breakthrough in the solid-state semiconductor-based three-terminal-based device was when the General Electric (GE) Company, of the US, successfully introduced a 300 V/7 A device named SCR in 1957. As this SCR performed the same operation as of a thyratron, it was named “thyristor” after its predecessor, thyratron, in the 1963 International Electro-technical Commission. Prior to thyristor introduction, the epoch making “transistor,” which W. Shockley invented in 1947, existed as a three-terminal solid-state semiconductor concept device. However, this solution was inadequate for high-voltage/current conversion requirement in the early days. The transistor technology shifted to silicon- material-based device fabrication technology from the original germanium-based approaches. However, due to shortcomings of the germanium semiconductor material (difficult-to-make devices of voltage breakdown characteristics higher than 300 V and a temperature rating higher than 80°C),4 thyristor and the diode technologies began with silicon-based fabrication methods, as the material was considered appropriate for making devices for high- power applications.
I
Published in Philip A. Laplante, Comprehensive Dictionary of Electrical Engineering, 2018
image acquisition idler wave the additional, often unwanted, output wave produced by an optical parametric oscillator designed to generate a signal wave. IEC See International Electro-technical Commission. IEEE See Institute of Electrical and Electronics Engineers. IEEE Color Books a series of seven books related to industrial and commercial power systems containing recommended IEEE/ANSI standards and practices. The books are color-coded as to subject as follows: Gray: Power systems in commercial buildings Green: Grounding industrial and commercial power systems Brown: Power system analysis Gold: Design of reliable industrial and commercial power systems Orange: Emergency and standby power for industrial and commercial power systems Red: Electric distribution practice in industrial plants Buff: Protection and coordination of industrial and commercial power systems. IEEE float encoding See NaN. ignitron a high-voltage mercury switch. The device is found in modulators used to dump the capacitor bank voltage in the event of a PA crowbar. An ignitron passes electrical current to a pool of liquid mercury at ground potential. IID See independent and identically distributed. II-VI semiconductor binary semiconductor made from elements in the periodic table two columns to the "left" and "right" of silicon, e.g., CdTe, ZnS, etc. III-V semiconductor a binary semiconductor made from elements from columns III and V in the periodic table. illumination the effect of a visible radiation flux received on a given surface. Illumination is measured by the illuminance, which is the luminous flux received by surface unit, usually expressed in lux. One lux equals 1 lumen/m2 . illumination system the light source and optical system designed to illuminate the mask for the purpose of forming an image on the wafer. ill-posed problem a problem whose solution may not exist, may not be unique, or may depend discontinuously on the data. A problem is wellposed if it can be shown that its solution exists, is unique, and varies continuously with perturbation of the data. If any of the three conditions does not hold, the problem is ill-posed. image acquisition the conversion of information into an image. Acquisition is the first stage of an image processing system and involves converting the input signal into a more amenable form (such as an electrical signal), and sampling and quantizing this signal to produce the pixels in the image. Hardware, such as lenses, sensors and transducers are particularly important in image acquisition. See analog-to-digital converter, digitization, image, pixel, quantization, sample.
Assessing experimental apparatus for sheet metal electromagnetic forming process analysis
Published in Materials and Manufacturing Processes, 2022
E. Paese, M. Geier, R. P. Homrich, Rodrigo Rossi, Pedro Rosa
This study presents a simple experimental apparatus using affordable components. A mathematical model was established to compare sheet metal EMF experiments with the simulated ones. Although some commercial EMF machines exist, these solutions are usually equipped with more complex and expensive high voltage pulse capacitors and switches with higher pulse repetition rates, such as solid-state, thyratron, ignitron discharge switches. This study proposes to use low voltage capacitors and a simple non-automated spark gap switch as an alternative to promote the development of EMF process analysis by comparing experimental and predicted numerical results. The main conclusions are listed below.. The proposed non-automated spark-gap switch proved to effectively drive the energy pulse, recording a maximum discharge current of 34.44 kA and a maximum rise rate of 0.389 kA/µs. This simple main discharge switch showed to be an affordable alternative to apply in EMF machines for laboratory facilities;The calculated distributions of the magnetic field in radial and axial directions with and without the coupled workpiece agree with the literature. These are important parameters to be evaluated, as these are used to calculate the electromagnetic force and inductances, respectively. Further, in the mathematical model used in this study, the mutual inductances play an essential role to couple the electrical and magnetic phenomena;Regarding the comparison between the methods to calculate the discharge current frequency: for the conditions analyzed, the formula of the significant frequency and Fourier analysis presented differences of up to +32% and −15%, respectively, when compared to the formula of series RLC circuits. The method using curve fitting from the simulated one showed to be more suitable for general applications;Finally, although the pulse unit frequency was low, which resulted in a skin depth to workpiece thickness ratio greater than 2.5, free bulging experiments were feasible for process analyses using a low voltage of 900 V. Consequently, the apparatus can aid the validation of simulated results and promote the development of the EMF process analysis.