a) Choose the BEST answer only for each of the following questions:

(ii) In a three phase uncontrolled full wave rectifier, each diode conducts for:

(iii) The switching control action in Fig. Q4(a-iii) is known as:

(iv) The ratio between the height of the reference wave and the carrier wave in inverter-control is called:

(v) For the three phase inverter circuit shown in Fig. Q4(a-v1), the state given in Fig.Q4(a-v2) results in which combination of line voltages?

(vi) The AC voltage of a square wave inverter is likely to have which of the following harmonic contents?

(vii) The extent of harmonic pollution in a current or voltage waveform can be determined by:

A three-phase fully controlled bridge rectifier is delivering a constant DC current of 50A to load from a 415V, 50Hz three phase source with a source inductance of 4.8mH per phase(and negligible source resistance). Neglecting the Thyristor forward voltage drop, for a firing angle of 45° determine: (i)The mean output voltage of the circuit The overlap angle The generalised mean output voltage of a p-pulse converter is given by the expression: V_{\text {mean }}=\left(\frac{p V_{\max }}{\pi} \sin \frac{\pi}{p}\right) \cos \alpha-\frac{p X}{2 \pi} I_{L} The generalized expression of mean voltage with overlap angle y is expressed as follows: V_{\text {mean }}=\left[\frac{p V_{\max }}{\pi} \sin \left(\frac{\pi}{p}\right)\right]\{\cos \alpha+\cos (\alpha+\gamma)\} (c) With the aid of appropriate sketches, discuss how a pulse width modulated control signal with variable duty cycle can be generated to control a dc/dc converter.[6]