Pdf ee6503 power electronics pe books, lecture notes. Natural commutated converters single phase and three phase controlled rectifier. Impact of fault current limiter on vschvdc dc protection b. In this process, a current pulse is made to flow in the reverse direction through the conducting thyristor and when the net thyristor current becomes zero, it is turned off. Voltage source invertervsi, single phase and three phase bridge. Compared to vsc, conventional thyristor based linecommutatedconverter lcc is usually configured as pointtopoint connection due to its current source nature that needs to alter the dclink voltage polarity for power reversal. Output voltage and load current waveforms continuous current when the current exceeds the chopper is turnedoff and it is turnedon when current reduces to. The ncp5030 is a fixed frequency pwm buckboost converter optimized for.
When the scr mutation capacitor in a resonant pulse resonant pulse commutation. During the interval t off the chopper is off and the load current will be flowing though the freewheeling diode fd. What are the advantages of load commutated chopper. After t3 ic supplies load current io and the excess current. An optimum control strategy for controlling the average output voltage of the chopper is given. Chopper control mode is an efficient means of complying with the iec 23. This application takes a large file and splits it into smaller pieces. The source voltage is 230 v dc and main scr turn off time is 30 sec. When thyristor is on, supply voltage appears acrossthe load and when thyristor isoff, the voltage acrossthe loadwill be zero.
Introduction of dc chopper using scr pantech solutions. Power electronics is the application of solidstate electronics to the control and conversion of electric power. Usually this reverse voltage is applied by switchining a perviously charged capacitor. Like a transformer, a chopper can be used to step down or step up the fixed dc input voltage. Principle of operation and analysis of buck converter, boost converter, buckboost converter and switched mode power supply. T 1 main thyristor, t a auxiliary thyristor, l,c commutating components, r c charging resistor. Show voltage variation across each pair of scrs as a function of time.
This form of thyristor natural commutation, which is illustrated in. Operation analysis of thyristor based front to front active. Current commutated chopper through simulink power inverter. The inputoutput characteristics of such linecommutated converters will be considered in detail in this chapter. For a maximum load current of 200a, calculate i the values of the commutating inductor and capacitor. Once the current is fully commutated to the main breaker, the ufd will open. Afetr t 4, a constant current equal to io flows through v s, c, l, d 2 and load. Loadcommutated current source inverter csi module 5. Linecommutated converters and inverters springerlink. The inverter bus voltage is 400 kv at the nominal operation point. Stepdown and stepup chopper control strategyforced commutated chopper voltage commutated, current commutated, load commutated, switched mode regulators buck, boost, buck boost converter, introduction to resonant converters.
The purpose of this chopper circuit is to control the flow of power from a dc voltage source to a load which consists of an rl circuit. Ee6503 power electronics previous year question papers. The effect of source impedance of various types r, l, or c on the output voltage, and the minimum value of inductance required on the dc side to provide continuous load current for both active and passive loads will also be discussed. Ture protection, shortcircuit protection and softstart are integrated. Apr 23, 2015 numerical problems a for a current commutated chopper, peak commutating current is twice the maximum possible load current. Cycloconverter and voltage controller principle of operation of cycloconverters three phase to single phase three phase to three phase input and output performances output voltage and frequency. This reverse voltage reduces the anode curent to zero repidly and aids in the completion of turn off process of the thyristor. In chapters 11 and 12 thyristor devices were used in conjunction with an ac supply which causes thyristor turnoff at supply current reversal. The holding current is usually lower than, but very close to, the latching current. Curriculum and syllabus for post graduate programmes cbcs july 2011 m. Current limit control the on and off of chopper circuit is decided by the previous set value of load current. Power electronics pdf notes pe notes pdf notes book starts with the topics thyristors silicon controlled rectifiers scrs,three phase converters three pulse and six pulse converters. Operation analysis of thyristor based front to front. Thyristor forced commutated dc choppers springerlink.
A step up chopper has a supply voltage of 250 v and output voltage of 500 vb period of the chopper is 100 micro seconds. It also refers to a subject of research in electronic and electrical engineering which deals with the design, control, computation and integration of nonlinear, timevarying energyprocessing electronic systems with fast dynamics. The power semiconductor devices have onstate voltage drop of 0. The output voltage and current waveforms are asshownin figure 2. Because of the rectified voltage, the current ripple is low, and iron losses are therefore low as well.
After t 3 i c supplies load current io and the excess current. Essentially, a chopper is an electronic switch that is used to interrupt one signal under the control of another. A commutation circuit for the turnoff of thyristor switches has been. During the time period t on the chopper is turned on and the load voltage is equal to source voltage v s. Since oscillating current through t1 turns it off it is called current commutated chopper. Conclusion in this paper we successfully study the simulation of current commutated chopper and voltage commutated chopper on matlab. If the pulse width is reduced to i rd for constant frequency operation, determine the op voltage. Impact of fault current limiter on vschvdc dc protection. The inductor l and freewheeling diode d serve the same purpose as discused in art.
The chopper goes into operation with a humming noise. In this method, a conducting scr is commutated by applying a large pulse of reverse voltage. Rc is so large such that it can be treated as open circuit during the commutation interval. Current commutated two quadrant thyristor chopper ieee xplore. Ecomputer eee department,third year 5th semester ee6503 power electronics previous year question papers for the regulation 20. The chopper is the dc equivalent to an ac transformer having continuously variable turns ratio. When the load current reaches the upper limit, chopper is switched off. Apply 3 5 describe the working of four quadrant chopper with neat sketch. Stepdown and stepup choppercontrol strategyforced commutated choppervoltage commutated, current commutated, load commutated, switched mode regulators buck, boost, buck boost converter, introduction to resonant converters. Impulse commutated choppers are widely used in high power circuits where load fluctuation is. Ee6503 power electronics previous year question papers auhippo. Close the switch, initially capacitor short circuited, after 4 5 time constants, v c v s.
Latching current i l latching current is the minimum forward current that has to be. Jul 07, 2016 since oscillating current through t1 turns it off it is called current commutated chopper. This is the only website,where you can download the previous year anna university question papers in pdf format with good quality and with out any water marks. Stepdown choppers output voltage and current waveforms. Power electronics notes pdf pe pdf notes smartzworld.
List various types of chopper and state basic principle of chopper. Power electronics all questions carry equal marks 10 marks q. During the interval t off the chopper is off and the load current. Distinguish between voltage source and current source inverters. The thyristor converter offers greater efficiency, faster response, lower maintenance, smaller size and smooth control. Here you can download the free lecture notes of power electronics notes pdf pe pdf notes materials with multiple file links to download. A chopper is a highspeed onoff semiconductor switch.
When the load current falls below lower limit, the chopper is switched on. Inverter station of the capacitor commutated converter. What are the advantages of current commutated chopper. The input dc voltage can be increased stepup or decreased step down in output side so a dc chopper circuit can be considered as dc equivalent to an transformer. Plot all of them on a graph paper in time phase relation with the. Download link is provided and students can download the anna university ee6503 power electronics pe syllabus question bank lecture notes syllabus part a 2 marks with answers part b 16 marks question bank with answer, all the materials are listed below for the students to make use of it and score good maximum marks with our study materials. Explain current commutated chopper with the help of diagram. Apr 24, 2020 loadcommutated current source inverter csi module 5 dc to ac converters lesson 40 notes edurev is made by best teachers of. Study of decade counting assemblydca, frequency measurements, period measurements, universal counter, introduction to digital meters. Dcchoppers with vcc,ccc load commutated and multiphase. Current commutated chopper through simulink free download as word doc. Chopper basics, types, applications power electronics a to z. Basic principle of frequency conversion, types of cycloconverter, noncirculating and circulating types of cycloconverters. This is achieved by using a forced commutated device mosfet, transistor, igbt etc.
Selfcommutated converters need no separate ac voltage source for commutation. Observe also the current waveforms through th1,c and load using the 0. Voltage equation for the circuit shown in figure 2. Midpoint and bridge connections with r, rl loads and rle load, derivation of. Dec 31, 2017 in this method, a conducting scr is commutated by applying a large pulse of reverse voltage. The values depend upon turn off time of main thyristor t1. Chopper x ltd a mode i, o c mode ill, t2st current commutated chopper. What are the different types of chopper with respect to commutation process. More often than not commutating voltage is provided by an energy store usually a quenching capacitor belonging to the converter or is formed by increasing the resistance of the converter valve to be turned off e. Erickson, principles of steadystate converter analysis, switch realization, discontinuous conduction mode, converter circuits, converter dynamics and control, controller design, basic magnetics theory, transformer design, power system harmonics, line commutated rectifiers, the ideal rectifier. Self commutated converters need no separate ac voltage source for commutation. Loadcommutated current source inverter csi module 5 dc. Chopper x ltd a mode i, o c mode ill, t2st electrical question bank power electronics all questions carry equal marks 10 marks q.
The current in the conducting scr is immediately quenched. A chopper is a static device which is used to obtain a variable dc voltage from a constant dc voltage source. In current commutated chopper, as the name suggests, chopper is commutated by current pulse. Chopper x ltd a mode i, o c mode ill, t2st current l h cu r ent is the fo ward b low whi h scr switches over from on state to the forwardblocking state. Be semestervi electrical question bank power electronics. Gto based chopper are also used these devices are generally represented by a switch. St62 microcontrollers drive home appliance motor technology. The two set values are maximum load current and minimum load current. Forced commutation topologies in thyristor chopper circuits. Understand 3 6 describe the step up and step down chopper with neat diagram. Compared to vsc, conventional thyristor based line commutated converter lcc is usually configured as pointtopoint connection due to its current source nature that needs to alter the dclink voltage polarity for power reversal.
In electronics, a chopper circuit is used to refer to numerous types of electronic switching devices and circuits used in power control and signal applications. Jul 08, 2016 voltage commutated chopper waveform the values of commutating components c and l can be obtained. Power electronics lab 2010 holding holding current l h cu r ent is the fo ward b low whi h scr switches over from on state to the forwardblocking state. A chopper is a device that converts fixed dc input to a variable dc output voltage directly. Tech in eee, electrical drives and control syllabi 530 ee 901 power electronic circuits and systems uniti.
Power electronics, smps, choppers, inverters, induction. Numerical problems a for a current commutated chopper, peak commutating current is twice the maximum possible load current. Let us now take a look of the output current and voltage wave forms of a chopper. It is because at no load, capacitor would not get charged frm vs to vs when auxiliary scr is triggered for commutating the main scr. Observe voltage waveform across th1, th2, c, l and the load. After a fixed period of time determined by circuit components.
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