Mar 19, 2017 the type c chopper is parallel combination of type a and type b chopper. If the supply is dc and the load current has no natural zero current periods, such as with the rl load, dc chopper circuit shown in figure. With this technique, the input current of the chopper rectifier can be highly sinusoidal with a total harmonic distortion thd of 2% to 5% see fig. Chopper x ltd a mode i, o c mode ill, t2st current source inverter is supplied through rectifier bridgecontrolled rectifier bridge or dc chopper. In a load commutated dc dc chopper, the capacitor has a. Chopper controlled dc drives electronics electronic.
An optimum control strategy for controlling the average output voltage of the chopper is given. The lc filter is connected at the input in order to get ripple free current. Essentially, a chopper is an electronic switch that is used to interrupt one signal under the control of another. Adtrons jones chopper is a selfcontained stand unit useful in the study and demonstration of the principle and working of a jones chopper. A chopper is a static power electronic device that converts fixed dc input voltage to a variable dc output voltage. Lecture notes on power electronics veer surendra sai. 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. Ans chopper circuit output voltage current waveforms average load voltage from ee 1 at engineering college. Mode 1 t2 on, capacitor voltage appears as reverse bias across t1and turns it off. Current commutated two quadrant thyristor chopper ieee xplore. Lecture notes on power electronics subject code bee1602 6th semester b. Fast responseload commutated choppers sciencedirect.
In current commutated chopper, as the name suggests, chopper is commutated by current pulse. The load current through the device at this instant, is the holding current of the device. In type b or second quadrant chopper the load must always contain a dc source e. Since oscillating current through t1 turns it off it is called current commutated chopper. Hvdc with voltage source converters a desirable solution for connecting renewable energies ying jianghafner rolf ottersten. Hvdc with voltage source converters a desirable solution.
Voltage commutated chopper current commutated chopper load commutated chopper skip to content engineering interview questions,mcqs,objective questions,class notes,seminor topics,lab viva pdf. Close the switch, initially capacitor short circuited, after 4. Commutation is reliable as load current is less than the peak commutation current. An scr is not suitable since once the device is latched on in this dc supply application, it remains on. After t 3 i c supplies load current io and the excess current. Above are the output voltage and current waveforms of a chopper circuit. Impulse commutated choppers are widely used in high power circuits where load fluctuation is. Four quadrant chopper drivesfour quadrant dc chopper drives learn and grow. Jones chopper or voltage commutated chopper in power electronics by engineering funda duration. Let us now take a look of the output current and voltage wave forms of a chopper. Four quadrant chopper drivesfour quadrant dc chopper. Source, ujt triggering circuit of variable frequency, class d.
Recent listings manufacturer directory get instant insight into any electronic component. Ans chopper circuit output voltage current waveforms. Two or more electrical contacts called brushes made of a soft conductive material. Pdf ee6503 power electronics pe books, lecture notes. Commutated chopper and voltage commutated chopper on matlab. Current commutated chopper through simulink power inverter. In this process, a charged capacitor momentarily reverse biases the conducting thyristor and turn it off. The following sections of the paper are devoted to the design aspects of current commutated choppers and brief descriptions of the trigger circuit, commutation.
A current pulse flows having a peak value vaux vcl from v1 t3 lc to charge up to 2vaux when c is fully charged, charging current tends to 0, and t3 turns off. When the chopper is on, v 0 is zero but the load voltage e drives the current through the inductor l and the chopper, l stores the energy during the time t on of the chopper. T 1 main thyristor, t a auxiliary thyristor, l,c commutating components, r c charging resistor. 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. The holding current is usually lower than, but very close to, the latching current. Voltage equation for the circuit shown in figure 2. During the time period t on the chopper is turned on and the load voltage is equal to source voltage v s. Chopper is the one represented by sw inside a dotted square which can be turned on or off as desired. It consists of a cylinder composed of multiple metal contact segments on the rotating armature of the machine. Dcchoppers free download as powerpoint presentation. The performance of these applications will be improved if we use a variable dc supply. This form of thyristor natural commutation, which is. Voltage commutated chopper mode1 and mode2 voltage commutated chopper. Input line current harmonics, power factor, current distortion and displacement.
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. What are the advantages of current commuted chopper. Nov 22, 2017 jones chopper working principle tutorial. 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. Voltage commutated chopper current commutated chopper load commutated chopper skip to content engineering interview questions,mcqs,objective questions,class notes,seminor topics,lab viva pdf free download. 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. Rc is so large such that it can be treated as open circuit during the commutation interval. In this post let us discuss about the operation of jones chopper remember that, jones chopper is the example for voltage commutated chopper. The thyristor converter offers greater efficiency, faster response, lower maintenance, smaller size and smooth control. Jul 08, 2016 voltage commutated chopper waveform the values of commutating components c and l can be obtained. Current commutated chopper mode4 and mode 5 operation. Di switches off, when the current falls back to the level of i m at time t 2. Types of chopper circuits type a, type b, type c, type d.
Continuous dc is given as source to the chopper as vs and chopped dc is obtained across the load as v0. Impulse commutated chopper both constant frequency and variable frequency operations. Scribd is the worlds largest social reading and publishing site. Close the switch, initially capacitor short circuited, after 4 5 time constants, v c v s. A chopper may be considered as dc equivalent of an ac transformer since they behave in an identical manner. What are the types of commutation with respect to commutation. A chopper is a device that converts fixed dc input to a variable dc output voltage directly. Thyristor forced commutated dc choppers springerlink. Current chopping a simple explanation, and calculations to. The discharging and charging time of commutation capacitor are dependent on the load current and this limits high frequency operation, especially at. Apr 06, 2009 a chopper is a static device which is used to obtain a variable dc voltage from a constant dc voltage source. Current chopping a simple explanation, and calculations to determine transient voltages when using vacuum interrupters john s. Nov 16, 1971 in a chopper or inverter having power thyristors that are switched on a control energization of a load from a dc source, and having commutating capacitors to which current is diverted from the power thyristors when they are to be switched off, recycling means are provided for recharging each commutating capacitor to bring it back to its. Type b chopper or secondquadrant chopper chopper second quadrant.
Forced, load commutation scr turn off process is called commutation thyristor turn off methods in chopper circuits current, voltage commutation. In chapters 11 and 12 thyristor devices were used in conjunction with an ac supply which causes thyristor turnoff at supply current reversal. The output voltage is always positive but output current either positive or negative in this type of chopper therefore it works in first as well as second quadrant. Jul 07, 2016 since oscillating current through t1 turns it off it is called current commutated chopper. The chopper can be viewed as an onoff switch that can rapidly connect or disconnect the source to load connection. 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. Source, ujt triggering circuit of variable frequency, class d commutation and d. Set the gate current ig ig1 such that forward break over voltage is between 15 to 20 v, by varying r2 and v2. The values depend upon turn off time of main thyristor t1. This is a major advantage, because high current rectifiers are usually the biggest consumers of electrical energy in the. The converter bridge connected in series in the dc transmission is of the current source linecommutated type, while the. 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.
Current commutated chopper power electronics electrical. The auxiliary scr is naturally commutated as its current passes through zero value. Jun 08, 2019 dc to dc converter is very much needed nowadays as many industrial applications are dependent upon dc voltage source. A chopper is a static device which is used to obtain a variable dc voltage from a constant dc voltage source. Dec 31, 2017 thyristor turn off methods in chopper circuits current, voltage commutation. Fast responseload commutated choppers iii from fig. Latching current i l latching current is the minimum forward current that has to be. We have seen already about the basic of chopper circuits, various types of chopper circuits. It will help to improve controllability of the equipments also. 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.
The capacitor always remains charged with the correct polarity. Jones chopper voltage commutated chopper 8531 adtron. Commutation of thyristorbased circuits partii nptel. In a chopper or inverter having power thyristors that are switched on a control energization of a load from a dc source, and having commutating capacitors to which current is diverted from the power thyristors when they are to be switched off, recycling means are provided for recharging each commutating capacitor to bring it back to its original potential after each commutation and. Dc to dc converter is very much needed nowadays as many industrial applications are dependent upon dc voltage source. Selfcommutated converters need no separate ac voltage source for commutation. A commutation circuit for the turnoff of thyristor switches has been. May 02, 20 mode 1 t1 t3 on, vs used to supply the current through load. Type c chopper class c chopper electrical revolution. The thyristorconverter offers greater efficiency, faster response, lower maintenance, smaller size and smooth control. Analysis of typea chopper, singleand two quadrant operation with dc motor load. Afetr t 4, a constant current equal to io flows through v s, c, l, d 2 and load.
The function of the inductor l is to decrease the ripple current whereas the capacitor c is to reduce source impedance. Apr 23, 2015 in current commutated chopper, as the name suggests, chopper is commutated by current pulse. The capacitor always remains charged with the correct. Mode 1 t1 t3 on, vs used to supply the current through load. What are the different types of chopper with respect to commutation process. The type c chopper is parallel combination of type a and type b chopper. Stepdown choppers output voltage and current waveforms.
1 239 335 715 1271 1542 255 1604 468 859 1580 131 555 874 835 579 599 433 1040 1230 426 1169 673 352 1060 777 1563 764 445 1157 1274 1056 496 1255 937 1178 182 232 278 146