Question

An inverter has a periodic output voltage with the output waveform as shown in figure.



When the conduction angle $\alpha$ = 120°, the rms fundamental component of the output voltage is

• A.
  0.90 V
• B.
  1.27 V
• C.
  0.78 V
• D.
  1.10 V

Answer 1

The correct option is C

0.78 V

$V_0=\sum _{n=1,3,\mathrm{5...}}^{\infty }\frac{4V_s}{n\pi }\sin nd\sin \frac{n\pi }{2}\sin n\omega t$

R.M.S. value of fundamental component, n = 1

$=\frac{4V_s}{\sqrt{2\pi }}\sin d\times 1$

$\alpha ={120}^{\circ }\therefore 2d=120{}^{\circ },\therefore d=60{}^{\circ }$

$=\frac{4V_s}{\sqrt{2}\pi }\times \sin 60{}^{\circ }=0.78V_s=0.78V$