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ENEE 403Bachelor in Electrical Engineering · Semester 71 Paper Available

Power Electronics

Past examination question papers and complete curriculum syllabus for Power Electronics (ENEE 403), Bachelor in Electrical Engineering Semester 7 under Institute of Engineering (IOE), Tribhuvan University.

Past Question Papers (PDF)

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Note: This question paper file (5th sem) was archived from an IOE exam session for the common Power Electronics curriculum.

5th-sem_Power Electronics.pdf

IOE Past Examination Paper

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Most Frequently Asked Questions

Top recurring IOE board exam questions for Power Electronics with verified mark schemes, formula notation, and recurrence frequency.

Showing 30 of 30 top repeated questions

Power Semiconductor Devices and Characteristics

4 Questions
#1Repeated 4 Times[8 Marks]Power Semiconductor Devices and Characteristics
Compare the V-I characteristics, switching speed, power handling capability, and safe operating area (SOA) of Power BJT, Power MOSFET, and IGBT.
Appeared in:2083 Baishakh2081 Bhadra2079 Chaitra2076 Chaitra
#2Repeated 3 Times[6 Marks]Power Semiconductor Devices and Characteristics
Explain the reverse recovery characteristics of a power diode. Derive expressions for reverse recovery time $t_{rr}$ and peak reverse current $I_{RM}$.
Appeared in:2082 Bhadra2080 Chaitra2077 Magh
#3Repeated 3 Times[6 Marks]Power Semiconductor Devices and Characteristics
Discuss Silicon Carbide (SiC) and Gallium Nitride (GaN) wide bandgap semiconductor devices. Why do they outperform Silicon in high-frequency power converters?
Appeared in:2082 Chaitra2080 Baishakh2078 Bhadra
#4Repeated 3 Times[6 Marks]Power Semiconductor Devices and Characteristics
Explain snubber circuits (RC and RCD snubbers) for protecting power switches against $dv/dt$ and $di/dt$ stresses.
Appeared in:2081 Chaitra2079 Baishakh2076 Baishakh

Thyristors and Gating/Commutation Techniques

4 Questions
#1Repeated 3 Times[8 Marks]Thyristors and Gating/Commutation Techniques
Describe the two-transistor analogy of an SCR. Derive the expression for anode current $I_A$ and explain the regenerative latching mechanism.
Appeared in:2083 Baishakh2081 Bhadra2078 Chaitra
#2Repeated 3 Times[8 Marks]Thyristors and Gating/Commutation Techniques
Explain different gate triggering circuits for SCRs: Resistance firing, RC firing, and UJT relaxation oscillator triggering circuits.
Appeared in:2082 Bhadra2080 Chaitra2077 Chaitra
#3Repeated 3 Times[8 Marks]Thyristors and Gating/Commutation Techniques
Classify thyristor commutation techniques: Natural (line) commutation vs forced commutation (Class A, B, C, D, E). Explain resonant commutation.
Appeared in:2082 Chaitra2079 Chaitra2076 Chaitra
#4Repeated 3 Times[6 Marks]Thyristors and Gating/Commutation Techniques
Explain GTO (Gate Turn-Off Thyristor) and TRIAC: Construction, two-way conduction mechanism, and gate drive circuit requirements.
Appeared in:2081 Bhadra2078 Bhadra2075 Chaitra

Phase-Controlled Rectifiers (AC to DC Converters)

5 Questions
#1Repeated 3 Times[8 Marks]Phase-Controlled Rectifiers (AC to DC Converters)
Derive expressions for average output voltage $V_{dc}$, RMS voltage $V_{rms}$, and ripple factor of a single-phase fully-controlled bridge rectifier with RL load and continuous conduction.
Appeared in:2083 Baishakh2081 Bhadra2079 Chaitra
#2Repeated 3 Times[8 Marks]Phase-Controlled Rectifiers (AC to DC Converters)
Analyze a single-phase semi-converter with RL load. Explain the role of the freewheeling diode in preventing negative output voltage and improving input power factor.
Appeared in:2082 Bhadra2080 Chaitra2077 Magh
#3Repeated 3 Times[8 Marks]Phase-Controlled Rectifiers (AC to DC Converters)
Derive the average DC voltage of a 3-phase fully-controlled bridge converter with RL load: $V_{dc} = \frac{3\sqrt{3}}{\pi} V_{ml} \cos \alpha$. Draw voltage and current waveforms for $\alpha = 60^\circ$.
Appeared in:2082 Chaitra2080 Baishakh2078 Bhadra
#4Repeated 3 Times[8 Marks]Phase-Controlled Rectifiers (AC to DC Converters)
Explain the effect of source inductance ($L_s$) on the performance of a 3-phase full converter. Derive expression for voltage drop due to commutation overlap: $\Delta V_{dc} = \frac{3\omega L_s}{\pi} I_{dc}$.
Appeared in:2081 Chaitra2078 Chaitra2076 Chaitra
#5Repeated 3 Times[8 Marks]Phase-Controlled Rectifiers (AC to DC Converters)
Describe dual converters (circulating and non-circulating current modes) for four-quadrant operation of DC drives.
Appeared in:2081 Baishakh2079 Baishakh2075 Bhadra

DC-DC Converters (Buck, Boost, Buck-Boost Choppers)

5 Questions
#1Repeated 3 Times[8 Marks]DC-DC Converters (Buck, Boost, Buck-Boost Choppers)
Explain the step-down (Buck) converter operating in Continuous Conduction Mode (CCM). Derive expressions for output voltage $V_o = D V_s$, inductor ripple current, and critical inductance $L_c$.
Appeared in:2083 Baishakh2081 Bhadra2078 Chaitra
#2Repeated 3 Times[8 Marks]DC-DC Converters (Buck, Boost, Buck-Boost Choppers)
Explain the step-up (Boost) converter operating in CCM. Derive output voltage equation $V_o = \frac{V_s}{1 - D}$ and output capacitor ripple voltage.
Appeared in:2082 Bhadra2080 Chaitra2077 Chaitra
#3Repeated 3 Times[8 Marks]DC-DC Converters (Buck, Boost, Buck-Boost Choppers)
Derive the transfer function and duty cycle relationship for a Buck-Boost converter: $V_o = -\frac{D}{1 - D} V_s$. Explain why the output polarity is reversed.
Appeared in:2082 Chaitra2079 Chaitra2076 Baishakh
#4Repeated 3 Times[8 Marks]DC-DC Converters (Buck, Boost, Buck-Boost Choppers)
Explain the operation of an isolated Flyback and Forward DC-DC converter. Discuss transformer core reset mechanisms.
Appeared in:2081 Bhadra2078 Bhadra2075 Chaitra
#5Repeated 3 Times[8 Marks]DC-DC Converters (Buck, Boost, Buck-Boost Choppers)
Explain four-quadrant chopper (Class E chopper) configuration and operation for bidirectional power flow in DC motor regenerative braking.
Appeared in:2083 Baishakh2080 Baishakh2077 Magh

Inverters (Single-Phase and Three-Phase PWM Inverters)

5 Questions
#1Repeated 3 Times[8 Marks]Inverters (Single-Phase and Three-Phase PWM Inverters)
Explain the single-phase full-bridge voltage source inverter (VSI) with square-wave and quasi-square-wave switching. Derive Fourier series of output voltage.
Appeared in:2083 Baishakh2081 Bhadra2079 Chaitra
#2Repeated 3 Times[8 Marks]Inverters (Single-Phase and Three-Phase PWM Inverters)
Analyze Sinusoidal Pulse Width Modulation (SPWM) for inverters. Define modulation index $m_a$ and frequency ratio $m_f$. Explain harmonic elimination using SPWM.
Appeared in:2082 Bhadra2080 Chaitra2077 Chaitra
#3Repeated 3 Times[8 Marks]Inverters (Single-Phase and Three-Phase PWM Inverters)
Explain the 3-phase bridge inverter in $180^\circ$ conduction mode and $120^\circ$ conduction mode. Draw phase and line voltage waveforms for both modes.
Appeared in:2082 Chaitra2080 Baishakh2078 Bhadra
#4Repeated 3 Times[8 Marks]Inverters (Single-Phase and Three-Phase PWM Inverters)
Explain Space Vector Pulse Width Modulation (SVPWM) for 3-phase VSIs. Discuss switching vectors, sector identification, and maximum linear modulation voltage compared to SPWM.
Appeared in:2081 Chaitra2078 Chaitra2076 Baishakh
#5Repeated 3 Times[6 Marks]Inverters (Single-Phase and Three-Phase PWM Inverters)
Describe Current Source Inverters (CSI) and compare them with Voltage Source Inverters (VSI) in terms of circuit topology, reliability, and motor drive performance.
Appeared in:2081 Baishakh2079 Baishakh2075 Bhadra

AC Voltage Regulators and Cycloconverters

3 Questions
#1Repeated 3 Times[8 Marks]AC Voltage Regulators and Cycloconverters
Analyze a single-phase AC voltage controller with resistive and inductive loads. Derive the expression for RMS output voltage as a function of firing angle $\alpha$.
Appeared in:2083 Baishakh2080 Chaitra2078 Bhadra
#2Repeated 3 Times[6 Marks]AC Voltage Regulators and Cycloconverters
Explain integral cycle control (burst firing) of AC voltage controllers. Discuss its advantages over phase angle control for heating loads.
Appeared in:2082 Bhadra2081 Baishakh2077 Magh
#3Repeated 3 Times[8 Marks]AC Voltage Regulators and Cycloconverters
Describe the operating principle of a single-phase to single-phase midpoint and bridge cycloconverter for sub-harmonic frequency generation.
Appeared in:2082 Chaitra2079 Chaitra2076 Chaitra

Applications in Motor Drives and Power Supplies

4 Questions
#1Repeated 3 Times[8 Marks]Applications in Motor Drives and Power Supplies
Explain speed control of separately excited DC motor using single-phase and three-phase full converters in both armature and field control modes.
Appeared in:2083 Baishakh2081 Bhadra2079 Chaitra
#2Repeated 3 Times[8 Marks]Applications in Motor Drives and Power Supplies
Describe constant $V/f$ control of 3-phase induction motor drives using SPWM inverters. Explain why torque remains constant below base speed.
Appeared in:2082 Bhadra2080 Chaitra2077 Chaitra
#3Repeated 3 Times[6 Marks]Applications in Motor Drives and Power Supplies
Explain Switched Mode Power Supplies (SMPS) topologies (Push-Pull, Half-Bridge, and Full-Bridge). State advantages over linear power supplies.
Appeared in:2081 Bhadra2078 Chaitra2075 Chaitra
#4Repeated 3 Times[6 Marks]Applications in Motor Drives and Power Supplies
Describe Uninterruptible Power Supply (UPS) configurations: Online UPS, Offline UPS, and Line-Interactive UPS with static bypass transfer switches.
Appeared in:2081 Chaitra2079 Baishakh2076 Baishakh

Curriculum Syllabus & Course Topics

Sourced from TU curriculum portal
Full Syllabus (PDF)
Chapter-wise Units & Micro-Syllabus Topics (7 Units)

  1. 1. Power Semiconductor Devices and Characteristics

    6

  2. 2. Thyristors and Gating/Commutation Techniques

    6

  3. 3. Phase-Controlled Rectifiers (AC to DC Converters)

    9

  4. 4. DC-DC Converters (Buck, Boost, Buck-Boost Choppers)

    8

  5. 5. Inverters (Single-Phase and Three-Phase PWM Inverters)

    8

  6. 6. AC Voltage Regulators and Cycloconverters

    5

  7. 7. Applications in Motor Drives and Power Supplies

    6

Examination Scheme & Marks Distribution

Evaluation Structure

  • Final Board Theory Exam: 60 Marks (Pass mark: 24)
  • Internal Assessment: 40 Marks (Pass mark: 16)
  • Practical / Lab Exam: 25 or 50 Marks (Continuous lab evaluation + viva, where applicable)

* This is the general current IOE 60/40 scheme; verify course-specific details in the syllabus above.

Exam Preparation Guidelines

  • Review the available past examination paper to understand question styling, typical derivation topics, and marks allocation.
  • Practice drawing labeled circuit schematics, deriving transfer functions, and showing systematic mathematical steps.
  • Structure answers with labeled diagrams, concise bullet points, and highlight final answers in numerical solutions.

Frequently Asked Questions (Power Electronics)

Q: How can I download Power Electronics past question papers?

You can preview or download the Power Electronics question papers (PDF) directly using the built-in viewer on this page with zero redirects or paywalls.

Q: What is the pass mark for Power Electronics?

The general current scheme is a 60-mark final theory exam and a 40-mark internal assessment, with pass marks of 24 and 16. Verify the course-specific syllabus above.

Q: Where can I find the complete syllabus for this subject?

The available chapter-wise syllabus and topic breakdown is indexed in the Syllabus section above, with links to the curriculum PDF source.

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