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Solution for Live Quiz Session: Power Electronics-31 Jan 2018
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Question 1
In single pulse modulation of PWM inverters, third harmonic can be eliminated if pulse width is equal to
Question 2
Circuit turn-off time of an SCR is defined as the time
Question 3
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 4
The power electronic converter shown in the figure has a single-pole double-throw switch. The pole P of the switch is connected alternately to throws A and B. The converter shown is a
Question 5
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 6
The separately excited dc motor in the figure below has a rated armature current of 20 A and a rated armature voltage of 150 V. An ideal chopper switching at 5 kHz is used to control the armature voltage. If La= 0.1 mH, Ra= 1Ω, neglecting armature reaction, the duty ratio of the chopper to obtain 50% of the rated torque at the rated speed and the rated field current is
Question 7
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 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 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 10
The following figure shows the voltage across a power semiconductor device and the currentthrough the device during a switching transition. Is the transition a turn ON transition or a turn OFF transition? What is the energy lost during the transition? 
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Jan 31ESE & GATE EE
