Question

A 3-phase semi converter feeds power to a resistive load of 10 $\Omega$. For a firing angle of ${30}^0$, the load takes 5 kW. The per phase supply voltage is _______V(rms).

• A. 101.43

Answer 1

The correct option is A 101.43
In a 3-phase semi converter, if $\alpha <{60}^0$, then the output rms voltage
$V_{0,rms}=\frac{V_{ml}}{2}\sqrt{\left[\frac{3}{\pi }[\frac{2\pi }{3}+\frac{\sqrt{3}}{2}(1+\cos 2\alpha \left)\right]\right]}$

$V_{0,rms}^2=\frac{{\left(\sqrt{2}\sqrt{3}{V}_{sph}\right)}^2}{4}\left[\frac{3}{\pi }[\frac{2\pi }{3}+\frac{\sqrt{3}}{2}(1+\cos 2\alpha \left)\right]\right]$

Dividing on both sides by
$R=10\Omega$

$\frac{V_{0,rms}^2}{R}=5000=\frac{6V_{sph}^2}{40}\times 3.2405$

$V_{sph}^2=\frac{5000}{0.486}$

$V_{sph}=\sqrt{\frac{5000}{0.486}}=101.43V$