User:SSAHUKAR2000/sandbox/power electronics

power electronics why wee need power electronics ...

== What is power electronics?

Power Electronics is a branch of Electrical Engineering which deals with power conversion from one from to another form using Inductors, Capacitors, Semiconductor devices (Diode, Thyristor, MOSFET, IGBT etc.). The power may be from mW(point on load applications) to MW(Power Systems). I like to explain Power Electronics with the following diagram. As you can observe that the Power Electronics is the centre of all branches. If you need to combine any two fields of System&Control, Power&Energy, Electronics&Devices you need to use Power Electronics. Energy Conversion can take place in any form. The basic conversions are •	AC - AC (Cycloconverters) •	DC - DC (Converters) •	DC - AC (Inverters) •	AC - DC (Rectifiers) Let me give examples using the triangle •	Every person pursuing electrical engineering must be having a idea of AC & DC Machines. For AC Machines, to control speed of the machines we change voltage amplitude or frequency. Power supply frequency is constant i.e. 50 Hz in India. So we can’t change the frequency without any frequency changer. This frequency changer circuit is achieved using Power Electronic Circuit. For DC Machines voltage supplied is dependent on back emf developed. This is achieved by providing a feedback to the Power Electronics Device. Here Power Electronics is a bridge between Machine and Control Part. HVDC applications also fall under this category. •	We get a supply of 220V 50Hz in our home. However there are many electronic devices which run of DC small voltages about 12V like the mobile chargers, DC lamps etc. Hence the AC needs to be converted to DC power and it is achieved using Power Electronic Devices. •	The biomedical operations are best examples of Electronic Devices with Control. ECG is one of them. The voltage or current provided to the electronic device depends on state of the device and many other conditions which are given in form of feedback path to the Power Electronic Device. These are also known as Point on Load Operations In short Power Electronics is present everywhere in electrical from mobile chargers to battery chargers, from transmission&distribution control to renewable energy storage and control. Power Electronics is also major part of the Battery Management System(BMS) and used for Electric Hybrid Vehicles(EHV).

Date-16-07-2019 •	Why we need power electronics? It plays a important role in energy conservation renewable energy systems and bulk utility energy storage. it is evident that power electronics play a important role in solving our climate change or global warming problems mainly it is used to convert AC power to DC

•	What is power electronics? The control of electric motor drive requires control of electric power, power electronics are the concept of power control, power electronics signified the word power electronics and control or we can set the electronics that deal with power equipment for power control.

Power control based on the switching power semiconductor devices. With the development of power semiconductor technology the power handling capability and switching speed power device have improved tremendous.

•	Power semiconductor device :- The first SCR was developed in let 1957. Power semiconductor device are broadly categorize into 3 types. 1.	Power diodes 2.	Transistor 3.	Thyristors…!

Date: 17-07-19

•	Thyristor :- Thyristor is a four layer, three junction PNPN semiconductor switching device. =	It has 3 terminals this are anode, cathode and gate. =	SCR (silicon control rectifier) are solid state device, so they are compact possesses high reliability and have low losses. =	SCR is made of silicone act as a rectifier. It has very low resistance in forward direction, high resistance in reverse direction, it is a unidirectional device

Structure on the physical and electronic level, and the thyristor symbol.

•	Thyristor is a family of power semiconductor device Date: 18-07-2019 •	They are operated as base table switches operating in non-conducting state and conducting state. •	Compact to transistors thyristors have lower on state conduction losses and higher power handling capability. •	Thyristor is a 4 layer semiconductor device, PNPN structure with 3PN junction, it has 3 terminals anode, cathode, and gate. •	Thyristor are manufacture by diffusion.

(Thyristor A thyristor (/θaɪˈrɪstər/) is a solid-state semiconductor device with four layers of alternating P- and N-type materials. It acts exclusively as a bistable switch, conducting when the gate receives a current trigger, and continuing to conduct until the voltage across the device is reversed biased, or until the voltage is removed (by some other means). A three-lead thyristor is designed to control the larger current of the Anode to Cathode path by controlling that current with the smaller current of its other lead, known as its Gate. In contrast, a two-lead thyristor is designed to switch on if the potential difference between its leads is sufficiently large (breakdown voltage). Some sources define silicon-controlled rectifier (SCR) and thyristor as synonymous.[1] Other sources define thyristors as more ornately constructed devices that incorporate at least four layers of alternating N-type and P-type substrate. The first thyristor devices were released commercially in 1956. Because thyristors can control a relatively large amount of power and voltage with a small device, they find wide application in control of electric power, ranging from light dimmers and electric motor speed control to high-voltage direct-current power transmission. Thyristors may be used in power-switching circuits, relay-replacement circuits, inverter circuits, oscillator circuits, level-detector circuits, chopper circuits, light-dimming circuits, low-cost timer circuits, logic circuits, speed-control circuits, phase-control circuits, etc. Originally, thyristors relied only on current reversal to turn them off, making them difficult to apply for direct current; newer device types can be turned on and off through the control gate signal. The latter is known as a gate turn-off thyristor, or GTO thyristor. A thyristor is not a proportional device like a transistor. In other words, a thyristor can only be fully on or off, while a transistor can lie in between on and off states. This makes a thyristor unsuitable as an analog amplifier, but useful as a switch. Thyristor Introduction The thyristor is a four-layered, three-terminal semiconductor device, with each layer consisting of alternately N-type or P-type material, for example P-N-P-N. The main terminals, labelled anode and cathode, are across all four layers. The control terminal, called the gate, is attached to p-type material near the cathode. (A variant called an SCS—silicon controlled switch—brings all four layers out to terminals.) The operation of a thyristor can be understood in terms of a pair of tightly coupled bipolar junction transistors, arranged to cause a self-latching action: Structure on the physical and electronic level, and the thyristor symbol. Thyristors have three states: 1.	Reverse blocking mode – Voltage is applied in the direction that would be blocked by a diode 2.	Forward blocking mode – Voltage is applied in the direction that would cause a diode to conduct, but the thyristor has not been triggered into conduction 3.	Forward conducting mode – The thyristor has been triggered into conduction and will remain conducting until the forward current drops below a threshold value known as the "holding current"

Function of the gate terminal The thyristor has three p-n junctions (serially named J1, J2, J3 from the anode). Layer diagram of thyristor. When the anode is at a positive potential VAK with respect to the cathode with no voltage applied at the gate, junctions J1 and J3 are forward biased, while junction J2 is reverse biased. As J2 is reverse biased, no conduction takes place (Off state). Now if VAK is increased beyond the breakdown voltage VBO of the thyristor, avalanche breakdown of J2 takes place and the thyristor starts conducting (On state). If a positive potential VG is applied at the gate terminal with respect to the cathode, the breakdown of the junction J2 occurs at a lower value of VAK. By selecting an appropriate value of VG, the thyristor can be switched into the on state quickly. Once avalanche breakdown has occurred, the thyristor continues to conduct, irrespective of the gate voltage, until: (a) the potential VAK is removed or (b) the current through the device (anode−cathode) becomes less than the holding current specified by the manufacturer. Hence VG can be a voltage pulse, such as the voltage output from a UJT relaxation oscillator. The gate pulses are characterized in terms of gate trigger voltage (VGT) and gate trigger current (IGT). Gate trigger current varies inversely with gate pulse width in such a way that it is evident that there is a minimum gate charge required to trigger the thyristor.) (https://r.search.yahoo.com/_ylt=AwrXpnRLNC9dxicA6wEPxQt.;_ylu=X3oDMTByb2lvbXVuBGNvbG8DZ3ExBHBvcwMxBHZ0aWQDBHNlYwNzcg--/RV=2/RE=1563403468/RO=10/RU=https%3a%2f%2fen.wikipedia.org%2fwiki%2fThyristor/RK=2/RS=X6Ffwcxd_.hEr5n9Iayv.k7hqmw- )

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