National Champion Test -GATE 2018 EE: Power Electronics for ESE & GATE EE Exams

Question 1

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 2

Figure shows a chopper. The device S1 is the main switching device. S2 is the auxiliary commutation device. S1 is rated for 400V, 60A. S2 is rated for 400V, 30 A. The load current is 20 A. The main device operates with a duty ratio of 0.5. The peak current through S1 is

Question 3

Power consumed by a balanced 3-phase. 3-wire load is measured by the two wattmeter method.
The first wattmeter reads twice that of the second. Then the load impedance angle in radians is

Question 4

A half-controlled single-phase bridge rectifier is supplying an R-L load. It is operated at a firing angle α and the load current is continuous. The fraction of cycle that the freewheeling diode conducts is

Question 5

How many operating modes are there in circuit shown, when current flows through the load?

Question 6

A bipolar junction transistor (BJT) is used as a power control switch by biasing it in the cut-off region (OFF state) or in the saturation region (ON state). In the ON state, for the BJT

Question 7

Which information is incorrect in terms of sinusoidal pulse width modulation?

Question 8

In a buck-boost conversion circuit, which among the following information is incorrect?

Question 9

The main reason for connecting a pulse transformer at the output stage of a thyristor triggering circuit is to

Question 10

A fully controlled natural commuted 3–phase bridge rectifier is operating with a firing angle α = 30 °. The peak to peak voltage ripple expressed as a ratio of the peak output dec voltage at the output of the converter bridge is

Question 11

The output voltage waveform of a three-phase square-wave inverter contains

Question 12

The triac circuit shown in figure controls the ac output power to the resistive load. The power dissipation in the load when firing angle is 45⁰.

Question 13

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 14

In the single phase voltage controller circuit shown in the figure, for what range of triggering angle (α), the output voltage (v₀) is not controllable?

Question 15

A voltage commutated chopper circuit, operated at 500Hz, is shown below.

If the maximum value of load current is 10 A, then the maximum current through the main (M) and auxiliaryA. thyristors will be