Page 44 – Multiple Questions & Answers (PWM & Inverters)
Subject: Power Electronics
Level: GATE / PSU Practice Set
🔹 Q1. What is the maximum line voltage in SPWM?
VLL,max = 0.866 Vdc
🔹 Q2. What is the maximum line voltage in SVPWM?
VLL,max = Vdc
🔹 Q3. How many switching states are present in a 3-phase VSI?
8 states (6 active + 2 zero vectors)
🔹 Q4. How many sectors are there in SVPWM?
6 sectors (each 60°)
🔹 Q5. Define Amplitude Modulation Index.
ma = Vm / Vcarrier
🔹 Q6. What happens when ma > 1?
Overmodulation occurs → waveform distortion increases.
🔹 Q7. In 180° conduction mode, how many switches conduct at a time?
Three switches conduct simultaneously.
🔹 Q8. In 120° conduction mode, how many switches conduct at a time?
Two switches conduct simultaneously.
🔹 Q9. What is the formula for switching time T₁ in SVPWM?
T₁ = Ts (Vref/Vdc) sin(60° − α)
🔹 Q10. Write the expression for zero vector time.
T₀ = Ts − (T₁ + T₂)
🔹 Q11. What is the main advantage of SVPWM over SPWM?
15% higher DC bus utilization.
🔹 Q12. Why must upper and lower switches of same leg never be ON together?
It causes shoot-through fault and short-circuits the DC bus.
Rapid Revision Summary
SPWM → 0.866 Vdc
SVPWM → Vdc
6 sectors → 6 active vectors
T₀ = Ts − (T₁ + T₂)
Power Electronics Practice Series – Shaktimatha Learning
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