Gandhinagar Institute of Technology “Power Electronics” Topic :Classification of choppers Branch : EE (5th sem B3) Guided by :Prof Supraja gidalluru Members: Aniket singh (130120109053) Dinesh Shirwani (130120109054) Nayan solanki (130120109055) Mitesh tanwani (130120109056)

Introduction Chopper is a static device. Power Electronics Introduction Chopper is a static device. A variable dc voltage is obtained from a constant dc voltage source. Also known as dc-to-dc converter. Thyristor converter offers greater efficiency, faster response, lower maintenance, smaller size and smooth control.

Choppers are of Two Types Power Electronics Step-down choppers. Step-up choppers. In step down chopper output voltage is less than input voltage. In step up chopper output voltage is more than input voltage.

Step down Chopper A step-down chopper with resistive load. Power Electronics Step down Chopper A step-down chopper with resistive load. The thyristor in the circuit acts as a switch. When thyristor is ON, supply voltage appears across the load. When thyristor is OFF, the voltage across the load will be zero. Prof. T.K. Anantha Kumar, E&E Dept., MSRIT

Principle Of Step-down Chopper Power Electronics Principle Of Step-down Chopper

Waveforms Of Step Down chopper Power Electronics Waveforms Of Step Down chopper

Parameters Of Step Down chopper Power Electronics Parameters Of Step Down chopper Prof. T.K. Anantha Kumar, E&E Dept., MSRIT

Power Electronics

Prof. T.K. Anantha Kumar, E&E Dept., MSRIT Power Electronics Prof. T.K. Anantha Kumar, E&E Dept., MSRIT

Prof. T.K. Anantha Kumar, E&E Dept., MSRIT Power Electronics Prof. T.K. Anantha Kumar, E&E Dept., MSRIT

Power Electronics

Prof. T.K. Anantha Kumar, E&E Dept., MSRIT Power Electronics Prof. T.K. Anantha Kumar, E&E Dept., MSRIT

Power Electronics Problem A Chopper circuit is operating on TRC at a frequency of 2 kHz on a 460 V supply. If the load voltage is 350 volts, calculate the conduction period of the thyristor in each cycle. 13 Prof. T.K. Anantha Kumar, E&E Dept., MSRIT

Power Electronics 14 Prof. T.K. Anantha Kumar, E&E Dept., MSRIT

Power Electronics 15 Prof. T.K. Anantha Kumar, E&E Dept., MSRIT

Power Electronics Methods Of Control The output dc voltage can be varied by the following methods. Pulse width modulation control or constant frequency operation. Variable frequency control.

Pulse Width Modulation Power Electronics Pulse Width Modulation tON is varied keeping chopping frequency ‘f’ & chopping period ‘T’ constant. Output voltage is varied by varying the ON time tON

Prof. T.K. Anantha Kumar, E&E Dept., MSRIT Power Electronics Prof. T.K. Anantha Kumar, E&E Dept., MSRIT

Variable Frequency Control Power Electronics Variable Frequency Control Chopping frequency ‘f’ is varied keeping either tON or tOFF constant. To obtain full output voltage range, frequency has to be varied over a wide range. This method produces harmonics in the output and for large tOFF load current may become discontinuous

Prof. T.K. Anantha Kumar, E&E Dept., MSRIT Power Electronics Prof. T.K. Anantha Kumar, E&E Dept., MSRIT

Principle Of Step-up Chopper Power Electronics Principle Of Step-up Chopper

When the chopper is ON, the inductor L is connected across the supply. Power Electronics Step-up chopper is used to obtain a load voltage higher than the input voltage V. The values of L and C are chosen depending upon the requirement of output voltage and current. When the chopper is ON, the inductor L is connected across the supply. The inductor current ‘I’ rises and the inductor stores energy during the ON time of the chopper, tON. Prof. T.K. Anantha Kumar, E&E Dept., MSRIT

Therefore voltage across load is given by Power Electronics When the chopper is off, the inductor current I is forced to flow through the diode D and load for a period, tOFF. The current tends to decrease resulting in reversing the polarity of induced EMF in L. Therefore voltage across load is given by Prof. T.K. Anantha Kumar, E&E Dept., MSRIT

Diode D prevents any current flow from capacitor to the source. Power Electronics A large capacitor ‘C’ connected across the load, will provide a continuous output voltage . Diode D prevents any current flow from capacitor to the source. Step up choppers are used for regenerative braking of dc motors. Prof. T.K. Anantha Kumar, E&E Dept., MSRIT

Expression For Output Voltage Power Electronics Expression For Output Voltage Prof. T.K. Anantha Kumar, E&E Dept., MSRIT

Prof. T.K. Anantha Kumar, E&E Dept., MSRIT Power Electronics Prof. T.K. Anantha Kumar, E&E Dept., MSRIT

Prof. T.K. Anantha Kumar, E&E Dept., MSRIT Power Electronics Prof. T.K. Anantha Kumar, E&E Dept., MSRIT

Prof. T.K. Anantha Kumar, E&E Dept., MSRIT Power Electronics Prof. T.K. Anantha Kumar, E&E Dept., MSRIT

Power Electronics

Performance Parameters Power Electronics Performance Parameters The thyristor requires a certain minimum time to turn ON and turn OFF. Duty cycle d can be varied only between a min. & max. value, limiting the min. and max. value of the output voltage. Ripple in the load current depends inversely on the chopping frequency, f. To reduce the load ripple current, frequency should be as high as possible.

Classification Of Choppers Power Electronics Classification Of Choppers Choppers are classified as Class A Chopper Class B Chopper Class C Chopper Class D Chopper Class E Chopper Prof. T.K. Anantha Kumar, E&E Dept., MSRIT

Class A Chopper Prof. T.K. Anantha Kumar, E&E Dept., MSRIT Power Electronics Class A Chopper Prof. T.K. Anantha Kumar, E&E Dept., MSRIT

Prof. T.K. Anantha Kumar, E&E Dept., MSRIT Power Electronics Prof. T.K. Anantha Kumar, E&E Dept., MSRIT

Class B Chopper Prof. T.K. Anantha Kumar, E&E Dept., MSRIT Power Electronics Class B Chopper Prof. T.K. Anantha Kumar, E&E Dept., MSRIT

Prof. T.K. Anantha Kumar, E&E Dept., MSRIT Power Electronics Prof. T.K. Anantha Kumar, E&E Dept., MSRIT

Class C Chopper Prof. T.K. Anantha Kumar, E&E Dept., MSRIT Power Electronics Class C Chopper Prof. T.K. Anantha Kumar, E&E Dept., MSRIT

Prof. T.K. Anantha Kumar, E&E Dept., MSRIT Power Electronics Prof. T.K. Anantha Kumar, E&E Dept., MSRIT

Class D Chopper Prof. T.K. Anantha Kumar, E&E Dept., MSRIT Power Electronics Class D Chopper Prof. T.K. Anantha Kumar, E&E Dept., MSRIT

Prof. T.K. Anantha Kumar, E&E Dept., MSRIT Power Electronics Prof. T.K. Anantha Kumar, E&E Dept., MSRIT

Prof. T.K. Anantha Kumar, E&E Dept., MSRIT Power Electronics Prof. T.K. Anantha Kumar, E&E Dept., MSRIT

Class E Chopper Prof. T.K. Anantha Kumar, E&E Dept., MSRIT Power Electronics Class E Chopper Prof. T.K. Anantha Kumar, E&E Dept., MSRIT

Four Quadrant Operation Power Electronics Four Quadrant Operation Prof. T.K. Anantha Kumar, E&E Dept., MSRIT

Advantages Reduction in supply harmonic currents. Reduction in the ripple content of output voltage Due to increased frequency of output voltage the size of the filter inductance L is reduced

Disadvantages Chopper cannot be tested without connecting load. Power Electronics Disadvantages Chopper cannot be tested without connecting load. Thyristor T1 has to carry load current as well as resonant current resulting in increasing its peak current rating. 44 Prof. T.K. Anantha Kumar, E&E Dept., MSRIT

Applications Widely used for motor control. Used in regenerative braking D.C motor speed control DC voltage boosting Battery operated appliances, cars Battery chargers

Thank you