Page 67 – 100 Very Tough MCQs (Part 2 – Advanced Numericals)
Level: GATE / PSU Advanced Numerical
🔹 DC-DC Converters
Q1. A buck converter operates with Vin = 48 V, D = 0.25, R = 12 Ω. Find output power. A) 12 W B) 24 W C) 48 W D) 96 WVo = D Vin = 0.25 × 48 = 12 V Io = 12/12 = 1 A P = 12 × 1 = 12 W Answer: A
--- Q2. Boost converter with D = 0.6. Find voltage gain. A) 1.5 B) 2 C) 2.5 D) 3Gain = 1/(1−D) = 1/0.4 = 2.5 Answer: C
--- Q3. Buck-Boost with D = 0.75. Gain magnitude equals? A) 3 B) 2 C) 1 D) 0.5|Vo/Vin| = D/(1−D) = 0.75/0.25 = 3 Answer: A
---🔹 DCM Concept
Q4. In DCM, output voltage increases if: A) Load decreases B) Load increases C) L increases D) fs decreasesFrom DCM gain: Vo ∝ R Load resistance increases → Vo increases Answer: B
---🔹 Inverters
Q5. Single-phase square inverter Vdc = 200 V Fundamental RMS? A) 90 V B) 127 V C) 180 V D) 200 VV1(rms) = (4Vdc)/(Ï€√2) = (800)/(3.14×1.414) ≈ 180 V Answer: C
---🔹 Controlled Rectifier
Q6. Single-phase full converter Vm = 325 V α = 60° Vo equals? A) 103 V B) 207 V C) 150 V D) 0Vo = (2Vm/Ï€)cosα = (650/3.14)(0.5) ≈ 103 V Answer: A
---🔹 Stability
Q7. Buck converter transfer function order? A) 1 B) 2 C) 3 D) 4Second order due to LC Answer: B
--- Q8. Natural frequency for L=200µH, C=100µF A) 7070 rad/s B) 5000 rad/s C) 10000 rad/s D) 15000 rad/sω₀ = 1/√(LC) = 1/√(200×10⁻⁶ × 100×10⁻⁶) = 1/√(2×10⁻⁸) ≈ 7070 rad/s Answer: A
---🔹 Mixed Concept
Q9. Increasing switching frequency results in: A) Larger filter size B) Smaller filter size C) Higher ripple D) Lower efficiencyHigher fs → smaller L & C Answer: B
--- Q10. MOSFET is preferred in: A) High frequency B) High voltage (>5kV) C) Very high current industrial drives D) HVDCMOSFET → high frequency switching Answer: A
---Page 67 Advanced Takeaways
✔ DCM load effect ✔ Square inverter fundamentals ✔ Rectifier numerical ✔ Natural frequency calculation ✔ Switching frequency effect
Power Electronics Advanced MCQ Series – Shaktimatha Learning
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