GATE 2020: Power Electronics Rapid Mini Mock for ESE & GATE EE Exams

Question 1

The reverse recovery time of a fast recovery diode is 3 µsec and the rate of fall of diode current is 20 A/µsec. Find the peak value of reverse current.

Question 2

What is the ratio of the average output voltage to per phase maximum AC voltage in a three-phase half-wave diode rectifier on a resistive load?

Question 3

The typical ratio of latching current to holding current in a 20 A thyristor is

Question 4

A free-wheeling diode is not required in an ac-dc full-converter circuit. It is because:

Question 5

A single-phase fully controlled thyristor bridge ac-dc converter is operating at a firing angle of 25^o and an overlap angle of 10^o with constant dc output current of 20 A. The fundamental power factor (displacement factor) at input ac mains of 230 V rms is

Question 6

A 3-phase fully controlled bridge converter with free wheeling diode is fed from 400 V, 50 Hz AC source and is operating at a firing angle of 60 °. The load current is assumed constant at 10 A due to high load inductance. The input displacement factor (IDF) and the input power factor (IPF) of the converter will be

Question 7

The single-phase full-bridge voltage source inverter (VSI), shown in figure, has an output frequency of 50 Hz. It uses unipolar pulse width modulation with switching frequency of 50 kHz and modulation index of 0.7. For V_in = 100 V DC, L = 9.55mH, C = 63.66 μF and R = 5 Ω, the amplitude of the fundamental component in the output voltage V₀ (in Volt) under steady state is __________.

Question 8

The circuit in figure shows a 3-phase half-wave. The source is a symmetrical, 3-phase four-wire system. The line-to-line voltage of the source is 100 V. The supply frequency is 400 Hz. The ripple frequency at the output is

Question 9

A three phase fully controlled bridge converter is feeding a load drawing a constant and ripple free load current of 10A at a firing angle of 30 °. The approximate Total Harmonic Distortion (% THD) and the rms value of fundamental component of the input current will respectively be

Question 10

In the following chopper, the duty ratio of switch S is 0.4. If the inductor and capacitor are sufficiently large to ensure continuous inductor current and ripple free capacitor voltage, the charging current (in Ampere) of the 5 V battery, under steady-state, is _______.

Question 11

A voltage commutation circuit is shown in figure. If the turn off time of the SCRs is 50 μ sec and a safety margin of 2 is considered, then what will be the approximate minimum value of capacitor required for proper commutation?

Question 12

The circuit shown is meant to supply a resistive load RL from two separate DC voltage sources. The switches S1 and S2 are controlled so that only one of them is ON at any instant. S1 is turned on for 0.2 ms and S2 is turned on for 0.3 ms in a 0.5 ms switching cycle time period. Assuming continuous conduction of the inductor current and negligible ripple on the capacitor voltage, the output voltage V₀ (in Volt) across RL is ______________.