Question

A single phase semi converter, using two thyristors and two diodes is shown in figure. If the firing angle delay is 60${}^o$, then the average value and rms value of thyristor current for continuous conduction respectively are

• A. 5.53 A and 7.82 A
• B. 7.82 A and 11.06 A
• C. 7.82 A and 15.64 A
• D. 11.06 A and 7.82 A

Answer 1

The correct option is A 5.53 A and 7.82 A

Average output voltage in semi-converter is
$V_0=\frac{V_m}{\pi }(1+cos\alpha )$
Also, $V_0=E+I_{0}R$

$\therefore \frac{230\sqrt{2}}{\pi }[1+cos{60}^o]=100+5I_0$

$I_0=11.06$ A
Average value of thyristor current,
$I_{t,avg}=I_0\left(\frac{\pi }{2\pi }\right)=\frac{I_o}{2}=\frac{11.06}{2}=5.53A$

Rms value of thyristor current,

$I_{t,rms}=\frac{I_0}{\sqrt{2}}=7.82A$