Download EE6503-Power Electronics

DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEE ING
QUESTION BANK
EE 6503 POWER ELECTRONICS
III Yr/ V SEM
UNIT-I
POWER SEMI-CONDUCTOR DEVICES
PART A
1. Define Holding and Latching current in SCR
2. List the advantages of GTO over SCR
3. Examine the current commutation of SCR
4. Name the limitation of high frequency operation of a power electronic device
5. List the use of snubber circuit
6. Tabulate the various forced commutation techniques used to turn off SCR
7. Distinguish between SCR and TRIAC
8. Predict the secondary breakdown in BJT
9. Discuss reverse recovery time in diodes
10. summarize the conditions under which a transistor operates as a switch
11. List any two advantages of TRIAC over SCR
12. Illustrate the need of snubber circuit
13. Classify the types of diodes
14. Compare the merits and demerits of IGBT and MOSFET
15. What are the advantages of GTO over thyristor
16. What are the three methods of triggering of thyristors
17. Define the pinch off voltage off MOSFET
18. Recommend any two difference between SCR and GTO
19. Draw TRIAC characteristics
20. Draw switching times characteristics of BJT
BTL 1
BTL 1
BTL 1
BTL 1
BTL 1
BTL 1
BTL 2
BTL 2
BTL 2
BTL 2
BTL 3
BTL 3
BTL 3
BTL 4
BTL 4
BTL 4
BTL 5
BTL 5
BTL 6
BTL 6
PART- B
1. Examine the structure and different modes of operation with the characteristics of TRIAC
(16)
BTL 1
2. (i) Describe the turn off characteristics of SCR and Explain the mechanism of turn OFF (8)
BTL 1
(ii) Describe in detail about the current commutation method of turn off SCR (8) BTL 1
3. Describe with circuit IGBT static I-V, transfer and turn –on and turn –off characteristics (16)
BTL 1
4. Examine different turn-on methods of SCR with its turn on characteristics (16)
BTL 1
5.Discuss the static and switching characteristics of IGBT and MOSFET (16)
BTL 2
6. (i) Snubber circuit for an SCR should primarily consist of capacitor only. But in practice
a resistor is used in series with the capacitr, Why-Discuss (8)
BTL 2
(ii) Discuss the dynamic characteristics of a thyristor during its turn –ON and turn-OFF
process. Discuss briefly the nature of these curves (8)
BTL 2
7. Summarize the various types of commutation circuits for SCR (16)
BTL 2
8. (i) Examine and draw the switching characteristics of SCR (8)
BTL 3
(ii) Demonstrate the working of a complementary commutation circuit of SCR with a neat
diagram and waveforms (8)
BTL 3
9. Examine the basic structure of IGBT and Explain its working .Give its equivalent circuit and
explain the turn ON and turn OFF processes (16)
BTL 3
10. (i) Explain and draw steady state and switching characteristics of power MOSFETS. (8)
(ii) With a neat diagram explain how the snubber circuit protects the MOSFET (8)
BTL 4
11. (i) Analyze the constructional details of an SCR. Sketch its schematic diagram and explain its
operation (8)
BTL 4
(ii) Explain turn-ON and turn-OFF characteristics of SCR (8)
12. (i) Analyze the various types of power diodes (8)
(ii) Explain and draw steady state and switching characteristics of SCR (8)
13. Explain the principle of operation and characteristics of GTO (16)
BTL 4
BTL 4
BTL 4
BTL 5
14. Design the switching model, equivalent circuit and switching waveforms and times of
MOSFET. (16)
BTL 6
UNIT-II
PHASE-CONTROLLED CONVERTERS
PART A
1. Define overlap angle
BTL 1
2. List the some of the application of converters
BTL 1
3. Examine the effect of source impedance on the performance of converter
BTL 1
4. Label the circuit and waveform of ideal dual converter
BTL 1
5. Define the phase control
BTL 1
6. Examine power factor of semi converter is better than full converter
BTL 1
7. Express the displacement factor for two pulse converter
BTL 2
8. Predict the circuit turn –off time for single phase full converter
BTL 2
9. Describe the disadvantages of dual converter with circulating current mode of operation
BTL 2
10.Predict by what power factor the DC output voltage of 6- pulse converter is reduced due to the
effect of source inductance
BTL2
11. Examine the harmonic factor for converter.
12. Illustrate the PIV of a thyristor
13. Examine the term voltage ripple factor
BTL 3
BTL 3
BTL 3
14. Classify the various modes of operation of single phase fully controlled bridge converter
BTL 4
15. Analyze the effect of freewheeling diode in converter
16. Explain the inversion mode of converter
BTL 4
BTL 4
17.Conclude the effect of inductive load in the performance of a three phase bridge.BTL 5
18. Summarize the parameters that are evaluated in rectifiers.
BTL 5
19. A two pulse converter is fed with a 230V, 50 Hz supply. The load on the converter is a pure
resistance of R=10 Ω. Obtain the average output voltage for a firing angle of
α =135°
BTL 6
20. A single phase full converter feeds power to RLE load with R= 6Ω ,E=60V.The full load
inductance value is very large so as to maintain the load current continuous and ripple free .The
ac source voltage is 230 V and 50Hz.Find the average value of the output voltage for a firing
angle delay of 50°.
BTL 6
PART-B
1. Describe the operation of three pulse converter with R load. Derive for average output
voltage (16)
BTL 1
2. (i). Label the operating principle of single phase dual converter (10)
BTL 1
(ii) A single phase full converter is connected with R- load .The source voltage is 230 V
50 Hz .The average load current is 10A For R=20 Ω .find the firing angle.(6) BTL 1
3. Examine the circuit and output wave form working of single phase two pulse fully
controlled converter with RL load discontinuous current mode of operation(16) BTL 1
4. Describe with the neat sketch of voltage and current waveform of a circulating current
type dual converter (16)
BTL 1
5. Discuss the operation of dual converter with complete circuit diagram and waveform(16)
BTL 2
6. (i) Discuss the effect of series inductance on the performance of the single phase full
converter indicating clearly the conduction of various thyristors during one cycle (8)
(ii) Describe the working of single phase dual converter in two modes (8)
BTL 2
7. Describe the working of a single phase full converter in the rectifier mode with RL load
.Discuss how one pair of SCRs is commutated by an incoming pair of SCRs. Illustrate
your answer with the waveforms of source voltage load voltage and source current.
Assume continuous conduction. Also derive the expression for average and rms output
voltage (16)
BTL 2
8. A 230 V ,50 Hz supply is connected to load resistance of 12Ω through half wave controlled
rectifier .If the firing angle is 60m degree ,Calculate
BTL 3
(i) Average output voltage
(ii)
Rms output voltage
(iii) Ratio of rectification and
(iv) Transformer utilization factor
(4)
(4)
(4)
(4)
9. (i) A single phase bridge converter is utilized to produce regulated DC output voltage .the
input voltage is 230 V and the load current is 8A for a firing angle of 30 degree(8)
(a)
Calculate the dc output voltage
BTL 3
(b)
Calculate the dc output voltage and current if a freewheeling diode is used at the
output for the same firing angle as in(i)
(ii) Examine the single phase half wave rectifier circuit with RL load and freewheeling diode
(8)
BTL 3
10. (i) A three phase full converter charges a battery from a three –phase supply of 230 V ,50
Hz .The battery is 200 V and its internal resistance is 0.5 Ω .On account of inductance
connected in series with the battery ,charging current is constant at 20 A. Compute firing
angle delay and supply power factor(8)
BTL 4
(ii) Explain briefly the working of dual converter with a neat circuit diagram. (8) BTL 4
11. Analyze the effect of source inductance in the operation of single phase fully controlled
converter with relevant diagram and analysis(16)
BTL 4
12. Explain the operation of a three phase ,fully controlled bridge converter with associated
waveforms (16)
BTL 4
13. Summarize the operation of single phase two pulse midpoint converter with relevant
voltage and current waveforms. (16)
BTL 5
14. Design and explain the working of single phase half controlled and fully controlled bridge
converter and draw the necessary input and output waveforms (16)
BTL 6
UNIT-III
DC TO DC CONVERTER
PART A
1. Describe PWM control in DC chopper
BTL 1
2. Define Duty cycle
BTL 1
3. Examine the time ratio control in DC to DC converter
BTL 1
4. Define the current limit control in DC to Dc converter
BTL 1
5. Name the application of DC chopper
BTL 1
6. List the control strategies for chopper circuit
BTL 1
7. Distinguish between time ratio and current limit control employed in a DC Chopper.
BTL 2
8. Summarize the need for resonant converter
BTL 2
9. Describe the DC chopper
BTL 2
10. Express the criteria for the selection of switching frequency in chopper
BTL 2
11. Illustrate the resonant switching based SMPS
BTL 3
12. Draw the circuit diagram of boost converter
BTL 3
13. Write the expression for the output average voltage of a step up chopper
BTL 3
14. Compare buck- boost and cuk regulators
BTL 4
15. Classify the advantages of switched mode regulators
BTL 4
16. Explain the TRC
BTL 4
17. Criticize the three different ways of controlling the average value of the load current in a
step down chopper
BTL 5
18. Summarize the disadvantages of frequency modulation scheme over the pulse width
modulation scheme
BTL 5
19. Generalize the purpose of commutation circuit in a chopper
BTL 6
20. Design the circuit of a step down chopper
BTL 6
PART – B
1. Examine the circuit diagram of buck regulator and explain its working principle
with necessary waveforms. Derive the expression for peak to peak ripple voltage of the
Capacitor that is present across the load. (16)
2.
BTL1
Describe the working principle of boost converter with necessary circuit and
waveforms. (16)
BTL1
3. i)Explain the various control strategies of chopper. (8)
ii) Analyze a filter component of a buck converter which has an input voltage of 12 V
and output voltage of 5V. The peak to peak output ripple voltage is 20mV and peak to
peak ripple current of inductor is limited to 0.8A. The switching frequency is 25KHz.
(8)
4. i)A dc chopper has an input voltage of 200V and a load of 15ohm resistance.
BTL4
When the chopper is on, its voltage drop is 1.5V and the chopping
frequency is 10KHz. If the duty cycle is 80%.Calculate
BTL3
i)average and rms output voltage ii)chopper on time.(12)
ii)p
rove the output voltage of step down chopper is Vo = D Vs. (4)
5. Describe the working principle of buck-boost converter with necessary circuit
and waveforms. (16)
BTL2
6. What is SMPS? Mention the types of SMPS. Explain flyback SMPS in
detail. (16)
BTL4
7. Explain Push pull SMPS, half bridge and full bridge SMPS. (16)
BTL4
8. Describe L type zero current switching resonant converters. (16)
BTL1
9. Examine M type zero current switching resonant converters. (16)
BTL1
10. Discuss zero voltage switching resonant converters(16).
BTL2
11. Describe four quadrant operation of choppers with its type and sketch operation of each
individual type in detail. (16)
BTL2
12. Demonstrate in detail the voltage-commutated chopper with RLE load, skech different
mode of operation with required wave forms. (16)
BTL3
13. Summarize in detail the current-commutated chopper with RLE load, sketch different
mode of operation with required wave forms. (16)
BTL5
14. Formulate in detail the load-commutated chopper with RLE load, sketch different mode
Of operation with required wave forms. (16)
BTL6
UNIT-IV
INVERTERS
PART A
1. Tell why diodes should be connected in antiparallel with the thyristors in
inverte r circuits?
BTL1
2. Name types of inve rters require feedback diodes.
BTL1
3. Define series inve rte r.
BTL1
4. Examine the condition to be satisfied in the selection of L and C in a se ries
inverter.
BTL1
5. Define space vector modulation.
BTL1
6. Quote the applications of a series inve rter.
BTL1
7. Describe the inverte r circuit classified based on commutation circuitry.
BTL2
8. Interpret McM urray inve rte r.
BTL2
9. Express the applications of a CSI.
BTL2
10. Discuss PWM control.
BTL2
11. Illustrate the advantages of PWM control.
BTL3
12. Show the disadvantages of the harmonics present in the inverter system.
BTL3
13. Show the methods of reduction of harmonic content.
BTL3
14. Contrast CSI and VSI.
BTL4
15. Explain the disadvantages of PWM control.
BTL4
16. Analyze what does ac voltage controller mean.
BTL4
17. Explain the applications of ac voltage controllers.
BTL5
18. Evaluate the advantages of ac voltage controlle rs.
BTL5
19. Formulate the disadvantages of ac voltage controlle rs.
BTL6
20. Generalize the two methods of control in ac voltage controllers. .
BTL6
PART – B
1. Describe the principle of operation of 3 phase voltage source inverter with
180˚conduction mode with necessary waveforms and circuits. Also obtain
the expression for line to line voltage. (16)
BTL1
2.Discuss the functioning of three phase voltage source inverter in 120 degree
operating mode with relevant waveforms and obtain the expression for voltages. (16)
BTL2
3. Explain and Formulate the following PWM techniques used in inverter.
BTL4
i) Sinusoidal PWM(8)
ii) Multiple PWM(8)
4. Examine the operation of single phase capacitor commutated CSI with R load.
BTL1
(16)
5. Explain the harmonic reduction by transformer corner lines and stepped
wave inverters. (16)
BTL1
6. Describe the different methods of voltage control adopted in an inverter with
suitable waveforms. (16)
BTL1
7. Express the working of series inverter with the help of circuit diagram and
relevant waveforms. (16)
BTL2
8.
Discuss the circuit diagram of current source inverter and explain its operation
with relevant waveforms. (16)
BTL2
9. Demonstrate the working of a single phase full bridge inverter supplying R, RL
BTL3
loads with relevant circuit and waveforms. (16)
10. Analyze the need for controlling the output voltage of inverters. Classify the
various techniques adopted to vary the inverter gain and brief on sinusoidal
PWM. (16)
BTL3
11.With neat diagram explain the need for space vector modulation employed in
inverters also explain the advantage SPVWM over other technique employed in
inverters. (16)
BTL4
12.with neat circuit diagram explain the operation of modified mcmurray half bridge
Inverter with different mode of operation. (16)
BTL4
13. Explain the operation of modified mcmurray-bedord half bridge Inverter with
different mode of operation. (16)
BTL5
14. Develop neat circuit diagram explain the operation of modified mcmurray full
bridge inverter with different mode of operation. (16)
BTL6
UNIT-V
AC TO AC CONVERTERS
PART A
1. D iffe rentiate between ON-OFF control and phase control.
BTL4
2. List the advantage of ON-OFF control.
BTL1
3. Examine the disadvantage of ON-OFF control.
BTL1
4. Point out the duty cycle in ON-OFF control method.
BTL4
5. Analyze unidirectional or half-wave ac voltage controller.
BTL4
6. Quote the disadvantages of unidirectional or half-wave ac voltage controller.
BTL1
7. Examine what is meant by bidirectional or half-wave ac voltage controller.
BTL1
8. Summarize the control range of firing angle in ac voltage controlle r with RL load
BTL2
9. Predict what type of gating signal is used in single phase ac voltage controlle r with RL
load.
BTL2
10. List the disadvantages of continuous gating signal.
BTL1
11. Define high frequency carrier gating.
BTL1
12. Discuss sequence control of ac voltage regulators.
BTL2
13. Give out the advantages of sequence control of ac voltage regulators.
BTL2
14. Explain what is meant by cyclo-conve rter.
BTL5
15. Examine the two types of cyclo-conve rters.
BTL3
16. Illustrate what is meant by step-up cyclo-converte rs.
BTL3
17. Examine step-down cyclo-converters.
18. Evaluate the applications of cyclo-conve rte r.
BTL5
19. Prepare what is meant by positive conve rte r group in a cyclo converte r.
BTL6
20. Generalize negative converte r group in a cyclo conve rte r.
BTL6
BTL3
PART-B
1.
Describe the circuit diagram of three phase to single phase cycloconverter and
explain its operation with waveforms. (16)
BTL1
2. With the necessary circuit diagram and waveforms, examine the principle of operation of
single phase ac voltage controller having only thyristor feeding resistive load by on-off
control and phase control. Derive the expression for rms value of output
voltages in both cases. (16)
BTL1
3. Describe the operation of single phase full wave AC voltage controller with the help
of voltage and current waveform. Also derive the expression for average value of
output voltage. (16)
BTL2
4. Describe sinusoidal and multiple PWM techniques used in inverter. (16)
BTL1
5. Describe the operation of the step down cycloconverter both bridge and midpoint
configuration with necessary waveforms. (16)
6.
BTL1
With aid of circuit diagram, explain the operation of three phase to three phase
cycloconverter employing
three phase
half wave circuits
and list few of its
applications. (1
)B
6TL4
7.
Explain the operation of single phase half wave phase controller with required
equations. (16)
BTL4
8. Explain the principle of working of single phase to single phase step up
cycloconverter. List the factors that affect the performance of cycloconverters. (16)
BTL5
9. Discuss the working of a single phase AC voltage controller with RL load when its
firing angle is more than the load power factor angle. Illustrate with waveforms. (16)
BTL2
10. A single phase voltage controller feeds power to a resistive load of 3Ω from 230V, 50
Hz source. Calculate 1) The maximum values of average and RMS thyristor currents
for any firing angle (4). 2) The minimum circuit turn off time for any firing angle (6). 3)
the ratio of third harmonic voltage to fundamental voltage for α=6 0 º(6).
BTL3
11.A single phase voltage controller is employed for controlling the power flow from
230V,50 HZ source into a load circuit consisting of R=3Ω and ω L=4Ω.Analyze
1.control range of firing angle(3),2.maximum value of rms load current(3),3.maximum
power And power factor(3),4.maximum values of average and rms thyristor
current(3),5.the conduction angle α=0 º and α=60 º assuming a gate pulse of duration π
radians(4).
BTL4
12.Discuss
single
phase
full
wave
phase
necessary equations and waveforms. (16)
controller
with
circuit
diagrams,
BTL2
13.A 1 Ø full wave ac voltage controller feeds a load of R=20Ω with an input voltage of
230V,50 HZ .firing angle for both the thyristor is 45 º.Evaluate 1.rms value of output
Voltage(3),2.Calculate load power and input power factor(3),3.average and rms current
of Thyristors(2). Also calculate above parameters when both thyristor firing angle is
30 º.(8)
BTL 3
14. Generalize 1 Ø half wave ac voltage controller feeds a load of R=20Ω with an input
voltage of 230V,50 HZ .firing angle for both the thyristor is 45 º.Calculate 1.rms
value of output Voltage(3),2.load power and input power factor(3),3.average and
rms current of thyristors(2).Also calculate above parameters when both thyristor
firing angle is 30 º(8
BTL6