$14-$ Single phase half bridge inverters requires

a$)$ two wire ac supply

b$)$ two wire de supply

c$)$ three wire ac supply

d$)$ three wire dc supply

$15.$ Find the average value of output current of a basic step$-$down chopper, with duty cycle $=d$ and load $=R.$

a$)I=Vsd$

b$)I=\frac{Vsxd}{R}$

c$)I=0$

d$)I=\frac{V}{R}$

$16-$ If a step up chopper's switch is always kept off then $($ideally$)$

a$)Vo=0$

b$)V_0=$

c$)Vo=Vs$

d$)Vo>Vs$

$17-$ If T is the time period for a chopper circuit and dis its duty cycle, then the chopping frequency is

a$)$ Ton$/$d

b$)$ Toff$/$d

c$)\frac{d}{T}$off

d$)\frac{d}{T}on$

$18-$A three$-$phase, three$-$pulse, controlled converter has firing angle for one of the SCRs set as $50$ This SCR would start conducting at

a$)0$

b$)50$

c$)110$

d$)80$

$19-$The ripple current of the RL load in the circuit supplied from Jordan electrical company through the diode, where $R=xL=20($ohms$)$ ; Inorm$=0\mathrm{.}4$;Irmsnorm $=0\mathrm{.}6$ IS

a$-\sqrt[\phantom{2}]{24\mathrm{.}2}$

b$-24\mathrm{.}2$

c$-12\mathrm{.}1$

d$-2\mathrm{.}2$

$20-$The ampere meter in AC position selector switch is connected in series with thyristor nol In three phase halve controlled rectifier with Irms $=27$amps, will indicate to the

a$)9A$

b$)\frac{27}{\sqrt[\phantom{2}]{?}}2A$

c$)27x\sqrt[\phantom{2}]{3}A$

d$)\frac{27}{\sqrt[\phantom{2}]{3}}A$

$21-$The retard angle of anode group of three pulses$-$controlled rectifier is

a$)0$

b$)30$

c$)60$

d$)90$