GATE 2022 EE – Question 60
A 3-phase grid-connected voltage source converter with DC link voltage of 1000 V is switched using sinusoidal Pulse Width Modulation (PWM) technique. If the grid phase current is 10 A and the 3-phase complex power supplied by the converter is given by $(-4000-j3000)$ VA, then the modulation index used in sinusoidal PWM is ________. (round off to two decimal places)
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Correct answer: 0.46 to 0.48
Explanation
The apparent power is $|S|=\sqrt{4000^2+3000^2}=5000$ VA $=3V_{ph}I_{ph}$ with $I_{ph}=10$ A rms, so $V_{ph}=166.7$ V rms. For sinusoidal PWM, $V_{ph,rms}=\frac{mV_{dc}}{2\sqrt2}$, so $m=\frac{166.7\times2\sqrt2}{1000}=0.47$.