Question

A single phase inverter is operated in PWM mode generating a single pulse of width 2d in the centre of each half cycle as given below,

If the pulse width is 140°, then the ratio of maximum value of third harmonic output voltage to maximum value of fundamental output voltage will be

Answer 1

For single phase PWM inverter, pulse width is
2d = 140°
d = 70°
$\text{Ratio}=\frac{\text{maximum value of third harmonic output voltage}}{\text{maximum value of fundamental output voltage}}$

$=\frac{\frac{4V_s}{3\pi }\sin (3\times 70{}^{\circ })\sin \left(\frac{3\pi }{2}\right)}{\frac{4V_s}{\pi }\sin \left(\frac{\pi }{2}\right)\sin \left(70{}^{\circ }\right)}$

$=\frac{1}{3}\frac{(-0.5)\times (-1)}{1\times 0.9397}=0.177\approx 0.18$

$\text{Ratio}=0.18$