Page 46 – Very Tough Mixed MCQ Test
Subject: Power Electronics
Level: GATE / PSU Advanced
Q1.
In SPWM, linear modulation region exists for: A) mₐ > 1 B) mₐ < 1 C) mₐ = 2 D) mₐ = 0Answer: B
Q2.
Maximum line voltage in SVPWM equals: A) 0.866 Vdc B) 0.707 Vdc C) Vdc D) 1.2 VdcAnswer: C
Q3.
Total active vectors in a 3-phase inverter: A) 8 B) 6 C) 4 D) 2Answer: B
Q4.
If switching frequency = 10 kHz, switching period Ts equals: A) 0.1 ms B) 1 ms C) 10 ms D) 100 μsAnswer: D
Q5.
If Vdc = 500V, find max fundamental line voltage in SPWM.VLL = 0.866 × 500 = 433 V
Answer: 433 V
Q6.
Number of sectors in SVPWM: A) 4 B) 6 C) 8 D) 12Answer: B
Q7.
Shoot-through condition occurs when: A) Zero vectors applied B) Both switches of same leg ON C) Dead-time inserted D) Reference vector zeroAnswer: B
Q8.
Improvement of SVPWM over SPWM is approximately: A) 5% B) 10% C) 15% D) 20%Answer: C
Q9.
If α = 150°, the vector lies in: A) Sector 1 B) Sector 2 C) Sector 3 D) Sector 4Answer: C
Q10.
In 120° conduction mode, number of conducting switches: A) 3 B) 2 C) 6 D) 1Answer: B
Q11.
Vdc = 600V. SVPWM max line voltage equals:Answer: 600 V
Q12.
Total switching states:Answer: 8
Q13.
Fundamental phase voltage in SPWM:Answer: mₐ × Vdc / 2
Q14.
Dead-time is introduced to:Answer: Prevent shoot-through
Q15.
Switching frequency affects: A) Output frequency B) Harmonics C) DC link voltage D) Load power factorAnswer: B
Q16.
If mₐ = 1.2, operation is:Answer: Overmodulation
Q17.
Zero vectors are:Answer: (000) and (111)
Q18.
Ts = 100 μs. If T₁ + T₂ = 70 μs, find T₀:Answer: 30 μs
Q19.
In 180° mode, each switch conducts for:Answer: 180°
Q20.
Maximum theoretical DC utilization in SPWM:Answer: 86.6%
Q21–25.
- Sector angle width = 60°
- Reference vector rotates at fundamental frequency
- Carrier frequency >> fundamental frequency
- THD reduces when switching frequency increases
- SVPWM reduces harmonic distortion compared to SPWM
Exam Strategy Tip
✔ Memorize 0.866 Vdc (SPWM)
✔ SVPWM = Vdc
✔ 8 states → 6 active + 2 zero
✔ 6 sectors → 60° each
✔ T₀ = Ts − (T₁ + T₂)
Advanced Power Electronics Practice – Shaktimatha Learning
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