Engineering Discipline (Electrical / Mechanical / Electronics / Civil / Instrumentation)
Where the technical marks sit
The AE technical paper is set in the discipline you applied for, but UPRVUNL is a generating utility, so questions cluster around power-plant application rather than pure theory.
- Electrical: three-phase relations (P = √3 V_L I_L cos φ, Y–Δ conversion), transformer equivalent circuit, efficiency and all-day efficiency, synchronous-machine excitation and V-curves, line parameters, circuit-breaker ratings, Merz-Price and distance protection.
- Mechanical: first law for open systems (SFEE), Rankine cycle and its departure from Carnot, turbine compounding, AFBC/CFBC boilers, affinity laws for pumps and fans, bending and torsion formulae, governors and balancing.
- Electronics: ideal op-amp assumptions (virtual short, infinite input impedance), rectifiers and ripple factor, BJT/MOSFET biasing, Boolean algebra and K-maps, 8085/8051 architecture, modulation.
- Civil: limit-state partial safety factors (1.5 dead and live, 1.15 steel), shear-force and bending-moment diagrams, effective span, bearing capacity, levelling.
- Instrumentation: transducer selection, Wheatstone and Maxwell bridges, static characteristics (accuracy, precision, linearity, hysteresis), PID action, 4–20 mA current loop.
Worked example
A 100 kVA transformer has 1 kW iron loss and 2 kW full-load copper loss. At full load, unity power factor: output 100 kW, losses 3 kW, so η = 100/103 = 97.1%. At half load: output 50 kW, copper loss scales as (1/2)² = 0.5 kW, so η = 50/51.5 = 97.1%. Maximum efficiency occurs where copper loss equals iron loss, i.e. at √(1/2) = 0.707 per unit, or 70.7 kVA.
Traps
Mixing line and phase quantities; giving transformer efficiency where all-day (energy-weighted) efficiency is asked; quoting Rankine efficiency as Carnot; sign errors in SFEE; dropping √3; applying a bridge balance condition to the wrong arm; confusing accuracy with precision.