Page 1 Dr. Ambedkar Institute of Technology, Bengaluru-560056

(An Autonomous Institution Affiliated to Visvesvaraya Technological University, Belagavi)

Third semester B.E. Degree (Autonomous) Semester End Examination (SEE), DEC/JAN 2020-21

POWER ELECTRONICS AND INSTRUMENTATION (Model Question Paper-01)

Max. Time: 3 Hours] [Max. Marks: 100

Instruction to candidates:

1. Answer all the Questions.

2. Each question is having internal choice.

3. Assume missed data suitably

Q.

No. Questions Marks COs

RBT

Level

1 a. With a neat circuit diagram and waveforms briefly explain the Resistance

capacitance firing circuit. [08

Marks] CO2 L1,L2

b. Explain the two transistor model of SCR and derive the formula for anode

current. [08

Marks] CO1 L1,L2

c. A Thyristor has a forward break over voltage of 175volts when a gate

pulse of 2mA is made to flow. Find the conduction angle if a sinusoidal

voltage of 350V peak is applied.

[06

Marks] CO2 L3

OR

2 a. Briefly explain the different ways to turn-on the Thyristor

[10

Marks]

CO1 L1,L2

b. What is power converter? List different types of power converters

[05

Marks]

CO1 L1,L2

c. Write a short note on Latching and Holding current.

[05

Marks]

CO1 L1,L2

3 a. Derive an expression for the average value of output voltage for 1-phase

half wave controlled rectifier with RL load. [07

Marks]

CO3 L1,L2

b. Write the advantages of freewheeling diode in the half wave controlled

rectifier [06

Marks]

CO3 L1,L2

c. What is Inverter? Explain the classification of Inverter

[06

Marks]

CO2 L1,L2

OR

4 a. With a neat circuit diagram and waveforms prove that Thyristor can be

used as step-up/step-down chopper. [10

Marks] CO2 L1,L2

b. A single phase half wave rectifier has a transformer secondary voltage of

230V, 50Hz and supplies a purely resistive load of R=1Ω. If the average

output voltage is 25% of the maximum possible value of DC output

voltage. Calculate

1. Delay angle of Thyristor.

2. RMS and average value of output current.

3. RMS and average value of Thyristor current.

4. Input Power factor.

[10

Marks] CO3 L3

5 a. State and explain the types of static Errors

[10

Marks] CO1 L1,L2

b. Briefly explain the Successive approximation type of Digital voltmeter

[10

Marks] CO4 L1,L2

USN 18EC35

Page 2 Dr. Ambedkar Institute of Technology, Bengaluru-560056

(An Autonomous Institution Affiliated to Visvesvaraya Technological University, Belagavi)

OR

6 a. State the advantages of digital voltmeter over the conventional analog

voltmeter [06

Marks] CO4 L1,L2

b. Determine the value of the multiplier resistance on the 50V range of a dc

voltmeter, which uses a 250µA meter movement with an internal resistance

of 100Ω.

[06

Marks] CO3 L3

c. With a neat diagram explain the Dual slope Integrator type Digital

Voltmeter

[08

Marks] CO4 L1,L2

7 a. State the advantages of Bridge circuits for measurements.

[06

Marks]

CO4 L1,L2

b. With the help of block diagram explain the function of the Oscilloscope

[08

Marks]

CO4 L1,L2

c. Write a short notes on Digital measurement of Time.

[06

Marks]

CO4 L1,L2

OR

8 a. Briefly explain the digital frequency meter

[10

Marks]

CO4 L1,L2

b. Write the block diagram and explain the working principle of function

Generator [10

Marks]

CO4 L1,L2

9 a. Write the difference between Active and Passive Transducer

[08

Marks] CO1 L1,L2

b. With a neat circuit diagram, Describe the resistance position transducer.

[06

Marks] CO4 L1,L2

c. Briefly explain the difference between resistance thermometer and

thermistor [06

Marks] CO1 L1,L2

OR

10 a. What are the factor to be considered for the selection of better transducer?

Explain. [10

Marks] CO4 L1,L2

b. Explain the construction and working of bonded resistance wire strain

gauge [10

Marks] CO4 L1,L2

*****

(Page 1 of 2)

Dr. Ambedkar Institute of Technology, Bangalore – 560056

(An Autonomous Institution Affiliated to Visvesvaraya Technological University, Belgaum)

USN

18EC35

B. E. Degree (Autonomous) THIRD Semester End Examination (SEE), Dec 2020 – Jan 2021

POWER ELECTRONICS AND INSTRUMENTATION

(Model Question Paper )

Time: 3 Hours

Maximum Marks: 100

Instructions to students:

Answer FIVE FULL Questions

Q. No Questions Marks CO RBT

Cognitive

Level

1

a) What is power electronics? with a neat block diagram explain the basic power

electronics system. [05

Marks]

1 L2,L3

b) Using 2 transistor analogy, derive an expression for anode current of SCR. [08

Marks]

1 L4

c) With a neat diagram explain the turn on and turn off characteristics of an SCR. [07

Marks]

1 L2

OR

2

a) Explain the various methods of Turn On of an SCR.

[08

Marks]

1 L2

b) With relevant circuit diagram and waveforms, explain UJT relaxation oscillator. [07

Marks]

1 L1,l2

c) Compare natural and forced commutation. [05

Marks]

1 L2

3

a) Explain, single phase full converter with R load with the help of necessary waveforms

[10

Marks]

2 L2

b) With relevant circuit diagram and waveforms explain the principle of ON-OFF of

a single phase ac controller. Derive the expression for RMS output voltage in

terms of RMS supply voltage and duty cycle of the operation of the controller.

[10

Marks]

2 L1,L4

OR

4

a) Explain the different control strategies used in choppers and also give the

classification of chopper.

[10

Marks]

2 L2

b) With the help of a neat circuit diagram explain the principle of a step

down chopper

[10

Marks]

2 L2

5 a) Explain the working principle of Successive approximation type DVM

[08

Marks]

3 L2

(Page 2 of 2)

Dr. Ambedkar Institute of Technology, Bangalore – 560056

(An Autonomous Institution Affiliated to Visvesvaraya Technological University, Belgaum)

b)

Define random error, significant figure and resolution [05

Marks]

3 L1

c) Explain the working principle of Dual Slope Integrating DVM. [07

Marks]

3 L2

OR

6

a) What is systematic error? Explain the different types of systematic errors

and how they can be avoided.

[08

Marks]

3 L1,L2

b) With a neat block diagram explain the working basic digital multimeter [07

Marks]

3 L2

c) Discuss the operating and performance characteristics of digital

voltmeter

[05

Marks]

3 L2

7

a) Explain in detail the working of a function generator. [10

Marks]

4 L2

b) Explain the working of digital storage oscilloscope and list the

advantages of DSO.

[10

Marks]

4 L2

OR

8

a) What are the limitations of wheat stone bridge? With a neat circuit

diagram explain the working of wheat stone bridge.

[10

Marks]

4 L1

b) Illustrate the working of Maxwell's bridge with all relevant

diagrams and equations.

[10

Marks]

4 L3

9

a) Interpret the construction, principle and operation of LVDT. [12

Marks]

4 L5

b) Identify the need for time delay in oscilloscopes. [08

Marks]

4 L3

OR

10

a) illustrate the working principle of thermister [12

Marks]

4 L2

b) Determine the factors to be considered for the selection of better

transducer

[08

Marks]

4 L5

Page 1 of 3

Dr.Ambedkar Institute of Technology, Bengaluru -560056

(An Autonomous Institution Affiliated to Visvesvaraya Technological University, Belagavi)

Instructions to the Candidates

i. Answer Five full questions

CO

RBT cognitive

Level

Q1 a) List and explain different types of power electronic converter systems [06 M] CO1

L1,L2

b) Explain the V-I characteristics of SCR by clearly indicating different states on

characteristics [07 M]

CO1 L2

c) Explain the two transistor analogy of SCR. Derive the expression for anode current [07 M] CO1 L2

OR

Q2 a) Define the following

i)latching current ii)holding current [06 M]

CO1 L1

b) With a neat diagram of gate characteristics of an SCR, explain the different regions

on characteristics. [06 M]

CO1 L2

c) Explain in brief different methods of triggering of SCR. [08 M] CO1 L2

Q3 a) Explain with the help of neat diagram and associated waveforms, the operation of

single phase half wave controlled converters

i)resistive load ii)inductive load

[10 M]

CO2,

CO3

L2

b) With the help of circuit diagram, explain the working of step –Up/down chopper [06 M] CO2,

CO3

L2

c) A step-up chopper is used to deliver load voltage of 500V from a 220V dc source.

If the blocking period of the thyristor is 80µs,compute the required pulse width. [04 M]

CO2,

CO3

L3

OR

Q4 a) With the help of circuit diagram, explain the working of step down chopper [10 M] CO2,

CO3

L2

b) A single phase half wave controlled converter has a supply of 120v, 50Hz and

supplies a pure resistive load of R=10Ω.If the average output voltage is 25% of the

maximum possible value of DC output voltage. calculate

i)Firing angle of thyristor

[04 M]

CO2,

CO3

L3

USN 1 D A 18EC35

Dr. AMBEDKAR INSTITUTE OF TECHNOLOGY, BENGALURU – 560056 (An Autonomous Institution Affiliated to Visvesvaraya Technological University, Belagavi)

Third Semester B. E. Degree (Autonomous)Semester End Examination, Dec/Jan 2020-21

Department of Electronics and Communication

Power electronics and instrumentation

[Max Marks:100] Model Question paper-III

Page 2 of 3

Dr.Ambedkar Institute of Technology, Bengaluru -560056

(An Autonomous Institution Affiliated to Visvesvaraya Technological University, Belagavi)

ii)RMS and average value of output current

c) Explain with the help of neat diagram and waveforms, the operation of single phase

half wave controlled converter with resistive load and hence derive an expression

for average load voltage.

[06 M]

CO2,

CO3

L2

Q5 a) With block diagram, explain the principle and operation of successive

approximation Type DVM. [10 M]

CO2,

CO4

L2

b) With a neat diagram, explain multirange ammeters [06 M] CO2 L2

c) Define the following terms

i)Gross error ii)systematic error [04 M]

CO1,

CO4

L1

OR

Q6 a) With block diagram, explain the principle and operation of Dual slope integrating

Type DVM. [08 M]

CO2,

CO4

L2

b) What is systematic error? Explain the different types of systematic errors and how

they can be avoided. [06 M]

CO1,

CO4

L1,L2

c) With a neat diagram, explain multirange voltmeters [06 M] CO2 L2

Q7 a) With a neat diagram,explain the working of Wein’s bridge ?how it can be used as

an oscillator? [07 M]

CO2 L2

b) With a neat block diagram, explain digital frequency meter. [08 M] CO2 L2

c) A capacitance comparison bridge is used to measure a capacitance impedance at a

frequency of 2Khz.the bridge constants at balance are

C3=100µF,R1=10KΩ,R2=50KΩ andR3=100KΩ.Find the equivalent series circuit

of unknown impedance.

[05 M]

CO2 L3

OR

Q8 a) Draw the basic block diagram of oscilloscope and explain the function of each block [08 M] CO2 L2

b) Draw the circuit diagram of wheatstone bridge and explain how it can measure

unknown resistance. [06 M]

CO2 L2

c) Draw the circuit diagram and obtain the balanced condition for maxwell’s bridge. [06 M] CO2 L2

Q9 a) List the factors to be considered while selecting a transducer. [07 M] CO2,

CO4

L1

b) Explain the principle of resistive position transducer. [07 M]

CO2,

CO4

L2

c) List the advantages of electrical transducer.

[06 M]

CO2,

CO4

L1

OR

Q10 a) Explain resistive thermometer, list the advantages [05M] CO2,

CO4

L2

b) Explain the working principle of LVDT with the help of neat sketch and

characteristics [10 M]

CO2,

CO4

L2

Page 3 of 3

Dr.Ambedkar Institute of Technology, Bengaluru -560056

(An Autonomous Institution Affiliated to Visvesvaraya Technological University, Belagavi)

c) List the advantages and limitations of thermistor. [05 M] CO2,

CO4

L1

-------------------