SIDDHARTH INSTITUTE OF ENGINEERING & TECHNOLOGY Dept . of EEE POWER SEMICONDUCTOR DRIVES Question bank

2-marks 1. What are the draw backs of dynamic braking? 2 What are the advantages of electric drives? 3 What is meant by dynamic braking? 4 Write the voltage and current relations in four quadrant operation. 5 What are the functions of freewheeling diode 6. write speed & torques expressions for 3 phase full converter fed by DC series motor 7. Draw the speed-torque characteristics of dc series motor fed by 1-ɸ full converter. 8. What is meant by regenerative braking? 9. What is a dual converter, how many thyristors are required for 1-ɸ dual converter 10. What is meant by electric braking? 11. What are the different modes of operations in four quadrant operation? 12. Sketch the speed torque characteristics of DC series motor fed by 1-ɸ semi converter. 13. Write the speed & torque equation for 1 semi-converter fed by SEDC motor. 14. What is meant by plugging? 15. Write the speed torque equation for 1 phase full-converter fed SEDC motor. 16. Write the advantages of regenerative braking? 17. What is meant by rectification mode and inversion mode. 18. What are the operating modes of full converter, mention their names. 19 Draw the speed - torque characteristics in four quadrant operation. 20 Define braking and list out the types of electrical braking?

5-Marks questions 1) Draw and explain operation of 3 phase full converter fed by SEDC motor. 2) Draw and explain operation of 3 phase full converter fed by dc shunt motor. 3) Draw and explain operation of 3 phase semi converter fed by dc series motor. 4. With neat circuit diagram explain the dynamic braking and plugging of SEDC motor.

5. Draw and explain the block diagram of closed loop speed control of DC motor for Below and above base speed.[L2] 6. Explain the operation of DC motor for Closed Loop Speed control with block diagram. 7. A 200 volts, 875rpm, 150 amperes SEDC motor has an armature resistance of 0.06ohm. It is fed from a single phase fully controlled converter with an AC source voltage of 220volts, 50Hz.Assuming continuous conduction, calculate the firing angle for rated Motor torque and speed of 750rpm. 8. Explain the operation of3-ɸ full converter fed by DC series motor with necessary waveforms. 9. A 150hp, 500volts SEDC motor is operating at 1050rpm is controlled by 3-ɸ semi converter Which is operating from 3-ɸ, 450volts, 50Hz supply. The rated armature current of the motor is 150A.The motor parameters are Ra=0.099Ω,La=0.63mH,Kaɸ=0.33V/rpm.Find the no load Speed at α=00,α=450.Assuming no load current is 10% of rated current. Calculate the firing Angle at 1650rpm at rated torque. 10. Explain the operation of single phase fully controlled converter fed DC separately excited Motor with neat Waveforms and derive the expressions for speed and torque. 11. Explain the operation of 3 ɸ semi controlled converter fed by SEDC motor with neat waveforms. 12.Write short notes on a) Plugging b) Dynamic braking c) Regenerative braking 13. Explain the speed torque characteristics of a SEDC motor connected to a 3-ɸ full converter With relevant equations. 14. With a neat diagram, explain the four quadrant operation of a DC drive in all four quadrants When fed by a Three phase dual converter. 15. A 220V, 970rpm, 100A dc separately excited motor has an armature resistance of 0.05Ω.It is Braked by plugging from an initial speed of 1000rpm.Calculate a) Resistance to be placed in armature circuit to limit braking current to twice the full load value, b) Braking torque c) Torque when the speed has fallen to zero. 16. With a neat diagram, explain the operation of a DC drive in all four quadrants when fed by a Single phase dual converter with necessary circuit diagrams. 17. a) Draw and explain operation of single phase full converter fed by SEDC motor. b) Derive the speed and torque equations of a fully controlled converter connected to SEDC motor with continuous current operation. 18. Two independent 1-ɸ semi-converters are supplying the armature and field circuits of the SEDC motor for controlling its speed. The firing angle of the converter supplying the Field, adjusted such that maximum field current flows. The machine parameters are: Ra=0.25Ω, Rf=147Ω, motor voltage constant K v = 0.7032 V/A-rad/s. The load torque is T = 45 N-m at 1000 rpm. The converter is fed from a 208 V, 50 Hz AC supply. The friction and windage losses are neglected. Find a) the field current, b )The delay angle of the armature converter, c )The input power factor of the armature circuit converter. 19. Explain how four quadrant operations is achieved by dual converters for SEDC motor With relevant circuit and quadrant configurations.