Electrical and Electronics

What is GTO? GTO is a three terminal device with anode, cathode and gate. It is similar to SCR. The major difference between SCR and GTO is that GTO can be turned off . GTO is a PNPN device that can be turned on by applying positive gate pulse and turned off   by applying negative gate pulse. So, it is called as non-latching device . It has higher switching speed than SCR and it can withstand higher voltage and current. At present, GTO with ratings up to 5000 V and 3000 A are present.  The GTO switches regeneratively into the on-state when a positive gate signal is applied to base of NPN transistor. During turn-off, the internal regeneration is reduced by reducing the current gain  of the PNP transistor which draws sufficient current from the gate. The reduction in gain of NPN transistor can be achieved by, Gold doped GTO Anode-shorted GTO   Gold doped GTO                        Anode-shorted GTO   ...

What is Thyristor? The term Thyristor came from its gas tube equivalent, thyratron. Its family name includes, Silicon Controlled Rectifiers(SCR) Bidirectional Triode Thyristors(TRIAC) Gate Turn-off Thyristors(GTO) MOS Controlled Thyristors(MCT) Integrated Gate-Commutated Thyristors(IGCT) Thyristors are operated as bi-stable switches, operating from non conducting state to conducting state. Thyristor can recover from its conducting state to non conducting state only when the current is brought to zero. It has four or more layers and three or more junctions. This device blocks voltage in both forward and reverse direction. The SCR is almost referred to as thyristor.   Thyristor(SCR) Characteristics SCR is a four-layer semiconductor device of PNPN structure with three p-n junctions. It has three terminals namely, anode, cathode and gate. The cross section of thyristor can be split into sections of NPN and PNP transistors.  When the anode voltage is made positive with respect...

What is Power Transistor? Power Transistor posses controlled characteristics. These are turned ON when current signal is given to base. The transistor will be in ON condition until control signal is present. When the control is removed, the power transistor is turned OFF. Power Transistor can be classified into four types, Bipolar Junction Transistor(BJT)  Metal Oxide Semiconductor Field Effect Transistor(MOSFET) Insulated Gate Bipolar Transistor(IGBT) Static Induction Transistor(SIT) Bipolar Junction Transistors(BJT) A BJT is a three-layer, two junction, npn or pnp semiconductor device. It can be classified into two types,  PNP Transistor - Two p region sandwiched by one n region NPN Transistor - One p region sandwiched by two n region The term 'bipolar' denotes, the current flow in the device is due to the movement of both holes and electrons.Collector, Base, Emitter are the three terminals present in BJT. NPN Transistors are used widely in handling high-voltage and high-cur...

What is Power Diode? A Power diode is two-terminal p-n junction device. They have large power, voltage and current handling capabilities than normal signal diodes. The frequency response(switching speed) is low compared to signal diodes. Diode acts as switch to perform various functions such as switches in rectifiers, freewheeling in switching regulators, charge reversal of capacitor and energy transfer between components, voltage isolation, energy feedback from the load to the power source and trapped energy recovery. The diode is said to be forward biased when the anode potential is positive with respect to cathode and reverse biased when cathode potential is positive with respect to anode. Diode conducts when it is forward biased. A conducting diode has small forward voltage drop across it and the magnitude of this drop depends on the manufacturing process and junction temperature. Under reverse biased condition, the diode does not conduct and a small reverse current (leakage curren...

POWER ELECTRONICS Power Electronics deals with the use of electronics for the control and conversion of large amount of electrical power. It constitute a vast, complex and interdisciplinary subject that has gone through rapid technological evolution. History A paper entitled " PNPN Transistor switches"( https://ieeexplore.ieee.org/document/4052177 ) was published by four engineers of Bell Telephone Laboratory, USA. It triggered intensive research on PNPN devices. Hence, in 1957 , Gordon Hall of General Electric Company, USA, developed the three terminal PNPN based semiconductor device called as Silicon Controlled Rectifier(SCR). Later on many power devices were developed similar to SCR. Power Electronic system  Power Electronic Converters Converter uses a matrix of power semiconductor switches to convert electrical power at high efficiency. The converter system is composed of switches, reactive components(L, C) and transformers. These converters are classified into, Phase Co...