Master previous years' questions for AC/DC Marine Electrical Machinery, Switchgear & Protection, Control Systems, Power Electronics & Drives, and Industrial Instrumentation.
Marking scheme: +1.00 positive, 0.00 negative.
A $3\text{-phase}$, $440\text{ V}$, $50\text{ Hz}$, $Y\text{-connected}$ synchronous marine generator supplies a full-load current of $I_a = 100\text{ A}$ at $0.8$ power factor lagging. The armature resistance is negligible ($R_a \approx 0$) and the synchronous reactance per phase is $X_s = 0.5\ \Omega$. What is the per-phase line-to-neutral open-circuit excitation voltage ($E_f$)?
A $3\text{-phase}$ fully controlled bridge converter (six-pulse) feeds a shipboard auxiliary propulsion DC drive from a $415\text{ V}$, $50\text{ Hz}$ AC source. If the thyristor firing delay angle is set to $\alpha = 60^\circ$ and the output load current is continuous and ripple-free, what is the average output DC voltage ($V_{\text{dc}}$)?