Power Electronics (EX-502) - Important Questions

Explain the different methods to turn on (trigger) a thyristor/SCR.

Describe the modes of operation of a thyristor/SCR with the help of its static V-I characteristics.

Explain the symbol, construction, characteristics and applications of power semiconductor devices such as Power MOSFET, IGBT, GTO, TRIAC, DIAC and LASCR.

Explain the working of a single-phase fully controlled / full-wave bridge controlled rectifier with circuit diagram and waveforms for R and RL load.

Explain the effect of freewheeling diode and source inductance on the performance of single-phase fully controlled converter including overlap angle and reduction in output voltage.

Explain what is meant by rectification mode and inversion mode in a single-phase fully controlled converter.

Explain the working of a three-phase bridge voltage source inverter in 120-degree conduction mode with star-connected resistive load and waveforms.

Explain the working of a three-phase bridge voltage source inverter in 180-degree conduction mode with waveforms.

Differentiate between voltage source inverter (VSI) and current source inverter (CSI).

Explain the working of step-up chopper with circuit diagram and waveforms and derive the expression for output voltage.

For a type-A chopper with source voltage Vs = 220 V, chopping period T = 2000 micro-s, on-period Ton = 600 micro-s, R = 1 ohm, L = 5 mH and E = 24 V, determine whether load current is continuous, calculate average output current and steady-state maximum and minimum load current.

Explain the working of Type-C chopper with circuit diagram and waveforms.

Explain the working principle of a single-phase bridge-type step-down cycloconverter with circuit diagram and input-output waveforms (e.g., output frequency f/2 for resistive load).

A single-phase full-wave AC voltage controller feeds a load of R = 5 ohm with an input voltage of 230 V, 50 Hz. If load power is 5 kW, find the thyristor firing delay angle and input power factor.

Explain the working of a single-phase full-wave AC voltage controller / regulator feeding an R-L (inductive) load with circuit diagram and waveforms.

A single-phase AC voltage controller with on-off control (4 cycles on and 3 cycles off) feeds a 10 ohm resistive load from 230 V supply. Estimate the RMS load voltage, RMS load current and input power factor.