Question

A 3-$\varphi$ full converter bridge is connected to supply voltage of 230 volt per phase and frequency of 50 Hz. The source inductance is 4 mH . The load current on dc side is constant at 20 A. If the load consists of a dc source of internal emf 320 V with internal resistance of $1\Omega$, then firing angle delay is

• A. ${46.92}^0$
• B. ${47.42}^0$
• C. ${48.96}^0$
• D. ${36.12}^0$

Answer 1

The correct option is B ${47.42}^0$

$V_0\left(avg\right)=E+I_0.R$

= 320 + 20 $\times$ 1 = 340 V

Also, $V_0\left(avg\right)=\frac{3V_{ml}}{\pi }cos\alpha -\frac{3\omega L_s{I}_0}{\pi }$

$340=\frac{3\times \sqrt{6}\times 230}{\pi }cos\alpha -\frac{3\times 314\times 0.004\times 20}{\pi }$

$\cos \alpha =\frac{340\pi +3\times 314\times 0.004\times 20}{3\times \sqrt{6}\times 230}$
$\alpha ={47.42}^0$