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Power Electroni...

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  • Question 1
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    Due to low internal generation in GTO, the GTO has

  • Question 2
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    The reverse recovery time of a diode is trr = 3 μs and the rate of fall is \(\frac{{di}}{{dt}} = 30\;A/\mu s\). The stored charge of the diode is

  • Question 3
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    To turn-off or commutate a thyristor

  • Question 4
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    A commutation circuit shown in figure

    What will be the maximum possible value of current through auxiliary thyristor

    TA when C = 0.3 mF L = 20 μH

  • Question 5
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    A voltage commutation circuit shown in figure. If turn off time of SCR is 10 μs and safety margin of 1.5. What will be the minimum value of capacitor required for commutation.

  • Question 6
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    Turn-on time (ton) of an SCR is related to its turn-off time (toff) in which of the following way?

  • Question 7
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    In a class D commutation as, shown in figure. L = 1 μH & C = 2 μF. For a constant load current of 100 A, calculate circuit turn off time for auxiliary thyristor

  • Question 8
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    For the simple chopper circuit shown, the average and rms value of currents for a duty cycle of 0.49, in amps, are (neglect the drop across chopper when ON)

  • Question 9
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    For the class-B commutation circuit shown below, the initial voltage across capacitor is 230 volt. For a constant load current of 300 A, the conduction time for the auxiliary thyristor is approximately equal to

  • Question 10
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    For the circuit shown below, the peak value of the current through thyristors T1 and T2 are

  • Question 11
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    A star-connected load of 20 Ω per phase is Fed from 450 V source through a 3-phase bridge inverter. For 180° mode determine load power in kW is ______ (correct up to 2 decimal places)

  • Question 12
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    A star connected load of 15 Ω per phase is fed from 420 V DC source through a 3-phase bridge inverter. If the inverter is operating in 120° conduction mode, the RMS value of thyristor current is _________ (in A)

  • Question 13
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    An IGBT chopper modulated power from a 200 V DC supply to a resistive load of 20 Ω. The switching frequency of the choppers is 1 kHz for VDS(sat) = 1.9 V. The chopper has a duty cycle, m = 0.8. The average power loss due to conduction is _______ (in W)

  • Question 14
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    A 1000 V 25 A GTO controls power from a DC supply of 600 V to Rload of 30 Ω. The data sheet gives the following information: the on-state voltage drop, VGTO(ON) = 2.2 V; average gate power should not exceed 10 W; IG Turn-off = -25 A.

  • Question 15
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    The SCR in the circuit shown below is forced commutated by a circuitry not shown in the figure. The SCR has minimum charging current of 5 mA to turn it on and its junction capacitance is 25 pF.

  • Question 16
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    A single-phase AC supply is connected to a full wave rectifier through a transformer. The rectifier is required to supply an average DC output voltage of Vdc = 400 V to a resistive load of R = 10 Ω. The kVA rating of the transformer is __________ (in kVA)

  • Question 17
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    The circuit shown below is initially relaxed. With switch closed at t = 0, the conduction time of diode is around

  • Question 18
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    A single-phase semi-converter, connected to 230 V 50 Hz source, is feeding a load R = 10 Ω in series with a large inductance that makes the load ripple-free. The firing angle is 30o, then the current distortion factor is_________

  • Question 19
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    A three-phase three pulse converter, fed from three-phase 400 V, 50Hz supply, has a load R = 2 Ω, E = 200 V, and large inductance so that load current is constant at 20A. If the source has an inductance of 2 mH, then the value of overlap angle for inverter operation is 

  • Question 20
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    In the phase-controlled half-wave converter shown above, the thyristor is fired in every positive half cycle of the input voltage, at an angle α. The firing angle for the peak value of the instantaneous output voltage of 200 V would be close to

  • Question 21
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    A single-phase 230 V, 1 kW heater is connected across single-phase 230 V, 50 Hz supply through a diode as shown in figure. The power delivered to the heater element is

  • Question 22
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    A single-phase full-bridge diode rectifier delivers a load current of 10 A, which is ripple free. The rms and average values of diode currents are respectively

  • Question 23
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    In the circuit shown below, the diode states at the extremely large negative value of the input voltage vi are

  • Question 24
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    A diode whose internal resistance is 20 Q is to supply power to a 1 kΩ load from a 230 V (rms) source of supply as shown in figure below. The percentage regulation from no load to the given load is

  • Question 25
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    A single-phase full-bridge inverter has RLC load of R = 4Ω, L = 35 mH, C = 155 μF. The DC input voltage is 230 V and the output frequency is 50 Hz. The third harmonic component in load current is:

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