Power quality encompasses even minimal deviation from a perfect sinusoidal waveform. Voltage commutated chopper it generally finds application in high power circuits where load fluctuations are not very large. Demystifying electronically commutated fan motors ecm in. Paper presented at the conference on largescale integration of wind power into power systems held in bremen, germany, oct 1415, 2009. They are used for electrochemical process, many kinds of motor drives, traction equipment, controlled power supplies, and many other applications. High power conversion technology for high voltage dc transmission application proven technology to transmission and connection dr. Subrahmanyam vedam, electric drives, concepts and applications tmh, new delhi, 1994.
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. Power electronics interview questions and answers pdf free download mcqs objective type questions lab viva manual gate cat preparation syllabus online quiz. Unit iv inverters ee6503 power electronics syllabus. Jan 07, 2016 this switching of the polarity in the coils maintains the armatures rotation in one direction. Psim simulation of a buck boost dcdc converter with wide conversion range. Essentially, a chopper is an electronic switch that is used to interrupt one signal under the control of another.
Therefore output current at the instant of commutation is, since v is the output. Numerical problems a for a current commutated chopper, peak commutating current is twice the maximum possible load current. This chopper is also known as parallel capacitor turn off chopper or impulse commutated chopper or classical chopper. The thyristorconverter offers greater efficiency, faster response, lower maintenance, smaller size and smooth control. A dc chopper is a static device that converts fixed dc input voltage to a variable dc output voltage directly. Jun 08, 2019 chopper is a basically static power electronics device which converts fixed dc voltage power to variable dc voltage or power. The voltage between brushes fluctuates in amplitude between zero and a maximum value, but is always maintains the same polarity. Capacitor is charged to v s, main thyristor t 1 is fired at t 0. Oct 12, 2018 voltage plwer of single phase inverters, single pulse width, multiple pulse width, and sinusoidal pulse width modulation. Average output voltage for step down chopper v 0 vs.
The power semiconductor devices used for a chopper circuit can be force commutated thyristor, bjt, mosfet, igbt. First step is to choose a thyristor with forward breakover voltage say 800v higher than the normal working voltage. Introduction to solid state power electronics editor. Apr 06, 2009 a chopper is a static device which is used to obtain a variable dc voltage from a constant dc voltage source. The principle of operation of chopper can be understood from the circuit diagram below. Threephase controlled rectifiers have a wide range of applications, from small rectifiers to large high voltage direct current hvdc transmission systems. Nov 16, 2017 voltage commutated chopper it generally finds application in high power circuits where load fluctuations are not very large. The low power line commutated converter lplcc consists of a recti er and an inductor.
Selfcommutated converters need no separate ac voltage source for commutation. Abb i mv ac drives product overview 3 product acs 5000 water cooled acs 6000 megadrivelci type of converter vsi voltage source inverter vsi voltage source inverter lci load commutated inverter typical applications compressors, extruders, pumps, fans, grinding mills, conveyors, blast furnace blowers, gas turbine starters. Design and implementation of a low power linecommutated. Both of these current source type of choppers can be designed to operate at chopping frequencies in excess of 5 kilohertz which provides for a fast response. Electronically commutated motor white paper portescap motor. Duty cycle is defined as the ratio of the on time of the chopper to the total time period of the chopper. Subrahmanyam vedam electric drives concepts and applications. For a maximum load current of 200a, calculate i the values of. Psim simulation of a buck boost dcdc converter with.
It is because a high reverse voltage will turn off the scr. Explain the working of voltage commutated chopper with aid of circuit diagram and necessary waveforms. A commutation circuit for the turnoff of thyristor switches has been. Lecture notes on power electronics veer surendra sai. Most of the hvdc systems in operation today are based on line commutated converters lcc. It is nothing but a high speed switch which connects and disconnects the load from source at a high rate to get variable or chopped voltage at the output. The thyristor converter offers greater efficiency, faster response, lower maintenance, smaller size and smooth control. During the period toff, load voltage is zero and chopper is off.
Voltage plwer of single phase inverters, single pulse width, multiple pulse width, and sinusoidal pulse width modulation. Jul 07, 2016 capacitor c is charged linearly to source voltage v s at t5, so during time t 5 t 4 i c i o. Two or more electrical contacts called brushes made of a soft conductive material. Voltage commutated chopper waveform the values of commutating components c and l can be obtained. Chopper is a basically static power electronics device which converts fixed dc voltagepower to variable dc voltage or power. In this commutation an opposite current pulse will be injected through scr. Psim simulation of a buck boost dcdc converter with wide. In this manner, a chopped dc voltage is produced at the load terminals. The recti er components include input alternating current that is step down with a high voltage transformer from 208v to 52 v, a series of ac lters that remove harmonics, a gate drive circuit responsible for converting ac voltage to dc voltage, a controller. A chopper is a static device which is used to obtain a variable dc voltage from a constant dc voltage source. The layout of this document and fonts have been chosen for optimal print ing rather than for optimal viewing onscreen.
High power conversion technology for high voltage dc. Power cube transformer definitions of power conversion terms, pdf file. An optimum control strategy for controlling the average output voltage of the chopper is given. Department of eee adi shankara institute of engineering and technology kalady, kerala, india. In chapters 11 and 12 thyristor devices were used in conjunction with an ac supply which causes thyristor turnoff at supply current reversal. The term line commutated indicates that the conversion process relies on the line voltage of the ac system to which the converter is connected in order to effect the commutation from one switching device to its neighbour. The high pass filter supplies 100 mvar at nominal ac bus voltage. Motor using chopper 1varun rohit vadapalli, 2hemanth kumar kella. Ee6503 power electronics syllabus regulation 20 anna university. S1 s1c s2 s2c us il0 il 0 on off on on ua ua off off on on 0 ua off on on on 0 0 ua jul 08, 2016 voltage commutated chopper waveform the values of commutating components c and l can be obtained. 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. Escr configurations and operating modes conversion principles reactive power capacitor commutated converter ccc. As mentioned earlier, the commutator is constructed in segments, which are insulated from each other. A voltage commutated chopper feeds power to an electric car.
Self commutated converters need no separate ac voltage source for commutation. Whether youve loved the book or not, if you give your honest and detailed thoughts then people will find new books that are right for them. Ee6503 power electronics syllabus regulation 20 anna. Connect the power supply to chopper and switchon the supply and then s1 and s2 on the panel. A chopper is a static device which is used to obtain a variable dc voltage from a constant dc voltage. The input dc voltage can be increased stepup or decreased stepdown in output side so a dc chopper circuit can be considered as dc equivalent to an transformer. Hvdc with voltage source converters a desirable solution for connecting renewable energies ying jianghafner rolf ottersten. High power conversion technology for high voltage dc transmission application. Chopper is a basically static power electronics device which converts fixed dc voltage power to variable dc voltage or power. Thyristor forced commutated dc choppers springerlink.
Power electronics, smps, choppers, inverters, induction motor. Hvdc with voltage source converters a desirable solution. Also, the choppers are commutated independently of supply voltage and load variations. Semiconductor division youngwood, pennsylvania 15697. Apr 23, 2015 numerical problems a for a current commutated chopper, peak commutating current is twice the maximum possible load current. Power electronics, smps, choppers, inverters, induction.
Commutation of thyristorbased circuits partii nptel. Connect the power supply to chopper and switchon the supply. The resistance of the commutator contacts causes inefficiency in low voltage, high current machines like this, requiring a huge elaborate commutator. Commutated converter compared to the conventional converter design the rated secondary transformer voltage can be smaller and the rated power of the transformer can be reduced as well. Current commutated two quadrant thyristor chopper ieee xplore. If these semiconductor devices are arranged appropriately, a chopper can work in any of the four quadrants. A short circuit of the supply voltage takes place via the scrs.
For the 11th and th harmonics ac filters with 250 mvar are installed. Voltage equation for the circuit shown in figure 2. A chopper can be said as dc equivalent of an ac transformer as they behave in an identical manner. New configuration of singlephase symmetrical pwm ac chopper voltage controller article pdf available in ieee transactions on industrial electronics 465. Current commutated chopper engineering notes current commutated chopper. In this method, a conducting scr is commutated by applying a large pulse of reverse voltage. Dc chopper a dc chopper is a static device that converts fixed dc input voltage to a variable dc output voltage directly. Chopper systems offer smooth control, high efficiency, faster response and regeneration facility. The discharging and charging time of commutation capacitor are dependent on the load current and this limits high frequency operation, especially at low load current chopper cannot be tested without. Most of the hvdc systems in operation today are based on linecommutated converters lcc.
A step up chopper has input voltage 110 v and output voltage 150 v. The chopper circuit in which output voltage is less than input voltage is called stepdown chopper or buck converter. The source voltage is 230 v dc and main scr turn off time is 30 sec. Hvdc technology line commutated converters michael bahrman, p. The term linecommutated indicates that the conversion process relies on the line voltage of the ac system to which the converter is connected in order to effect the commutation from. This paper describes two fast response load commutated choppers. Although direct current motors and dynamos once dominated industry, the disadvantages of the commutator have caused a decline in the use of commutated. Voltage commutated chopper mode1 and mode2 voltage. Protecting igbts and mosfets from esd esd is the discharge of static electricity. For a maximum load current of 200a, calculate i the values of the commutating inductor and capacitor. Commutated chopper and voltage commutated chopper on matlab. Guangfu tang global energy interconnection research institute geiri sept.
The benefit is that the thyristor will be in blocking state with normal working voltage applied across the anode and cathode with gate open. It consists of a cylinder composed of multiple metal contact segments on the rotating armature of the machine. In a chopper, regulating transistorfet is biased as a switch always at. Power electronics lab 2010 1 if a negative voltage is applied to anode and a positive voltage is applied to cathode of the scr, the junction j2 is forward biased and j1 and j2 are reverse biased with very small leakage current flow called reverse blocking current. Power electronics choppers a chopper uses high speed to connect and disconnect from a source load. Jones chopper employes the principle of voltage commutation. Hvdc converter using selfcommutated devices article pdf available in ieee transactions on power electronics 6. Other readers will always be interested in your opinion of the books youve read. Unit iii dc choppers introduction a chopper is a static device which is used to obtain a variable dc voltage from a constant dc voltage source. Stepdown and stepup choppercontrol strategyforced commutated choppervoltage commutated, current commutated, load commutated, switched mode regulators buck, boost, buck boost converter, introduction to resonant converters. Average output voltage for step down chopper is vo. Static electricity is an excess or deficiency of electrons on one surface with respect to another surface or to ground, pdf file. A chopper is a device that converts fixed dc input to a variable dc output voltage directly. Vibin c thomas department of eee adi shankara institute of engineering and technology kalady, kerala, india.
Voltage commutated thyristorised chopper trainer for. However, with a stepper motor this theoretical model is difficult to achieve, mainly for 2 reasons. Write down the expression for average output voltage for step up chopper. Calculate the value of capacitor c required for the commutating circuit. Demystifying electronically commutated fan motors ecm in data centers marc naccache, p.
The values depend upon turn off time of main thyristor t1. The thyristor converter offers greater efficiency, faster. Measure the chopper frequency and read off the output voltage both from the analog meter and the electronic multimeter. When thyristor is on, supply voltage appears across the load and. A fixed dc voltage is applied intermittently to the source load by continuously triggeri.
Types of chopper circuits type a, type b, type c, type d. Di switches off, when the current falls back to the level of i m at time t 2. Pdf new configuration of singlephase symmetrical pwm ac. Usually this reverse voltage is applied by switchining a perviously charged capacitor. Fast responseload commutated choppers sciencedirect. This form of thyristor natural commutation, which is. A commutator is a rotary electrical switch in certain types of electric motors and electrical generators that periodically reverses the current direction between the rotor and the external circuit. Pdf chopper operation using psim eckhart anant academia. What is the difference between a chopper and dc voltage. As a result currents decreases and finally comes to zero if both the currents would be equal and opposite. Voltage commutated thyristorised chopper trainer for vocational training and didactic labs naugra export is leading voltage commutated thyristorised chopper trainer for vocational training and didactic labs manufacturer, supplier and exporter in india. This reverse voltage reduces the anode curent to zero repidly and aids in the completion of turn off process of the thyristor.
The circuit consists of a semiconductor diode, resistor, and a load. A chopper is a static power electronic device which converts fixed dc input voltage to a variable dc output voltage. Introduction of dc chopper using scr pantech solutions. Voltage sourced converter based hvdc project adopted mmc as the primary.
This kind of choppers are more efficient as they involve one stage conversion. In power electronics chopper circuits, unidirectional power semiconductors are used. What are the different types of chopper with respect to commutation process. A chopper can be said as dc equivalent of an ac transformer. Power electronicsvoltage commutated thyristor circuit a voltage source is impressed across the scr to be turned off, mostly by an auxiliary scr. Thyristor chopper circuits questions and answers sanfoundry.
1586 838 452 861 1286 787 969 381 1309 667 563 1533 334 1393 1588 756 1587 1298 1380 1626 957 87 1011 1369 197 1600 1322 226 823 991 143 604 1575 160 272 320 249 663 348 271 1282 1304