Question

In a three phase semi converter bridge circuit feeding RL (large inductor) load, if firing angle $\alpha =\frac{\pi }{2},$ then the rms value of source current is_____A.
(Assume constant load current of 10 A)

Answer 1

In three phase semi converter, the analysis differs with the firing angle.
i.e., $\alpha >{60}^{\circ }$
or $\alpha \le {60}^{\circ }$
Here in this case, it is $\alpha >{60}^{\circ }$ which is $\frac{\pi }{2}={90}^{\circ }=\alpha$
$\therefore$ Rms value of source current,
$I_{s\left(rms\right)}=I_0\sqrt{\frac{\pi -\alpha }{\pi }}$
$I_{s\left(rms\right)}=10\times \sqrt{\frac{{180}^{\circ }-{90}^{\circ }}{{180}^{\circ }}}=10\sqrt{\frac{1}{2}}$
$I_{s\left(rms\right)}=7.07A$