Competitive Exams: Electronics MCQs (Practice-Test 12 of 13)

  1. “Six MOSFETs connected in a bridge configuration (having no other power device) MUST be operated as a Voltage Source Inverter (VSI)” This statement is [GATE-2007]

    1. True, because being majority carrier devices, MOSFETs are voltage driven

    2. True, because MOSFETs have inherently anti parallel diodes

    3. False, because it can be operated both as current source Inverter (CSI) or a VSI

    4. False, because MOSFETs can be operated as excellent constant current sources in the saturation region

    Answer: d

  2. A single phase full-wave half controlled bridge converter feeds an inductive load. The two SCRs in the converter are connected to a common DC bus. The converter has to have a free wheeling diode [GATE-2007]

    1. because the converter inherently does not provide for free wheeling

    2. Because the converter does not provide for free wheeling for high values of triggering angles

    3. Or else the free wheeling action of the converter will cause shorting of the AC supply

    4. Or else if a gate pulse to one of the SCRs is missed, it will subsequently cause a high load current in the other SCR

    Answer: b

  3. 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 [GATE-2010]

    1. Step down chopper (buck converter)

    2. Half-wave rectifier

    3. Step Up chopper (boost converter)

    4. Full wave converter

    Answer: a

  4. The fully controlled thyristor converter in the figure is fed from a single-phase source.

    When the firing angle is 0° the dc output voltage of the converter is 300 V. What will be the output voltage for a firing angle of 60° assuming continuous conduction? [GATE-2010]

    1. 150V

    2. 210V

    3. 300V

    4. 100 (pi) V

    Answer: a