Question

In single phase semiconverter, the ratio of active power to the reactive power is 0.75. The firing angle $\alpha$ in degree will be ________ degree.

• A. 106.26

Answer 1

The correct option is A 106.26
In semiconverter
$V_0$ = average output voltage
$I_0$ = average output current

Active power, $P=V_0{I}_0$

Reactive power, $Q=V_0{I}_0\tan \left(\frac{\alpha }{2}\right)$

Given, $\frac{P}{Q}=0.75$

$\frac{V_0{I}_0}{V_0{I}_0\tan \frac{\alpha }{2}}=0.75$

$\tan \frac{\alpha }{2}=\frac{4}{3}$

$\frac{\alpha }{2}={\tan }^{-1}\left(\frac{4}{3}\right)$

or firing angle, $\alpha =106.26{}^{\circ }$