Question

A single phase full converter is supplied from $230V,50Hz$ source. The load consists of $R=10\Omega$ and a large inductance so as to render the load current constant. For a firing angle of ${30}^o$, the average and rms values of thyristor currents respectively are

• A. $8.96$ and $10A$
• B. $8.96$ and $10A$
• C. $8.96$ and $12.67A$
• D. $8.96$ and $10A$

Answer 1

The correct option is C $8.96$ and $12.67A$

Average output voltage of single phase full converter is
$V_0=\frac{2V_m}{\pi }cos\alpha$

$V_0=\frac{2\sqrt{2}\times 230}{\pi }cos{30}^o=179.33V$

$I_0=\frac{V_0}{R}=\frac{179.33}{10}=17.93A$


The average value of thyristor current,
$I_{T,avg}=17.93\times \frac{\pi }{2\pi }=8.96A$

The rms value of thyristor current,
$I_{T,rms}=17.93\times \sqrt{\frac{\pi }{2\pi }}=12.67A$