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New Methods of Increasing Transmission Capacity
Published in Anjan K. Deb, Power Line Ampacity System, 2017
A TCR consists of a reactor in series with a bidirectional thyristor pair. A thyristor is a fast-acting electronic switch, basically a four-layer pnpn device, consisting of anode, cathode, and gate. The thyristor is turned on by applying a short pulse across the gate and cathode, and turned off by applying a reverse voltage across the anode and cathode. The reactive power absorbed by the TCR device is controlled by regulating the current flow through the reactor by directing the firing angle of the thyristor between 90° and 180°. There is full conduction at 90° firing angle. Increasing the firing angle decreases current, and conduction is blocked when the angle is 180°. A continuously variable lagging reactor power, QL, is made possible by controlling the firing angle of the thyristor given by,
Power Electronics
Published in Mohd Hasan Ali, Wind Energy Systems, 2017
Power semiconductor devices first appeared in 1952 with the introduction of the power diode by R. N. Hall. It was made of germanium and had a voltage capability of 200 volts and a current rating of 35 amperes. The thyristor appeared in 1957. Thyristors are able to withstand very high reverse breakdown voltage and are also capable of carrying high current. One disadvantage of the thyristor for switching circuits is that once it is “latched on” in the conducting state it cannot be turned off by external control. The thyristor turn-off is passive; that is, the power must be disconnected from the device. The first bipolar transistors devices with substantial power handling capabilities were introduced in the 1960s. These components overcame some limitations of the thyristors because they can be turned on or off with an applied signal. With the improvements brought about by metal–oxide–semiconductor technology (initially developed to produce integrated circuits), power metal–oxide–semiconductor field-effect transistors (MOSFETs) became available in the late 1970s. International Rectifier introduced a 25 A, 400 V power MOSFET in 1978. These devices allow operation at higher frequency than bipolar transistors but are limited to low-voltage applications. The insulated gate bipolar transistor (IGBT) developed in the 1980s became widely available in the 1990s. This component has the power handling capability of the bipolar transistor, with the advantages of the isolated gate drive of the power MOSFET.
Analysis of Pulse-Fed Single-Input Single-Output Systems
Published in Anish Deb, Suchismita Ghosh, Power Electronic Systems, 2017
We consider the thyristor as an ideal switch and neglect the switching time of the semiconductor devices as these are small compared to the usual pulse time. The underlying assumptions for such a motor drive system are as follows [26]: During a certain pulse condition, the speed N of the motor remains unchanged.The inductance of the armature circuit remains constant. Actually, this value decreases somewhat with increasing current and flux due to saturation.The effect of circulating current in the commutating coils is neglected.Operation of the motor is in the linear region of the magnetization curve.The brushes are located on the magnetic neutral axis, and all armature feedback effects are neglected.Voltage drops in brushes or semiconductor devices are neglected.
Characteristic Analysis of Cascading-Combination DC/DC Controlled-Source Circuit for Marine Electromagnetic Transmitter
Published in Electric Power Components and Systems, 2023
Haijun Tao, Zheng Zheng, Lina Guo
Marine electromagnetic emitter is divided into shipboard part and underwater part, where the former provides initial electric energy for underwater part and monitors underwater devices [10]. Underwater part mainly consists of controlled-source circuit, emitting bridge and emitting dipole, where controlled-source circuit is responsible for transforming electric energy and transforming single-phase AC current input by tow into controlled DC current, and emitting bridge generates time-domain or frequency-domain electromagnetic waves which will be excited to the seafloor through emitting dipole. Diode uncontrolled or thyristor phase-controlled rectification mode is used in controlled-source circuit of marine electromagnetic transmitter as shown in Figure 2. As uncontrolled rectifying circuit can’t modulate amplitude, excitation regulation of generator is usually used to control output voltage, but excitation regulation will affect revolving speed of generator, which results in great voltage fluctuation and slow dynamic response of regulation. Thyristor is used as power switching element to replace power diode to constitute phase-controlled rectifying bridge which can control voltage amplitude but will cause reduction of power factor in depth control.