Thyristors-4 MCQ

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• Latching current for an SCR is 100 mA, a dc source of 200 V is also connected to the SCR which is supplying an R-L load. Compute the minimum width of the gate pulse required to turn on the device. Take L = 0.2 H & R = 20 ohm both in series.
  ক

  62.7 μsec

  খ

  100.5 μsec

  গ

  56.9 μsec

  ঘ

  81 μsec
• Consider the two transistor analogy of SCR, if α1 & if α2 are the common-base current gains of both the transistors then to turn-on the device
  ক

  α1 + α2 should approach zero

  খ

  α1 x α2 should approach unity

  গ

  α1 – α2 should approach zero

  ঘ

  α1 + α2 should approach unity
• From the two transistor (T1 & T2) analogy of SCR, the total anode current of SCR is ___________ in the equivalent circuit.
  ক

  the sum of both the base currents

  খ

  the sum of both the collector current

  গ

  the sum of base current of T1 & collector current of T2

  ঘ

  the sum of base current of T2 & collector current of T1
• The gate-source voltage is Es = 16 V and the load line has a slope of 128 V/A. Calculate the gate current for an average gate power dissipation of 0.5 W.
  ক

  62.5 mA

  খ

  100.25 mA

  গ

  56.4 mA

  ঘ

  80.65 mA
• Latching current for an SCR is 100 mA, DC source of 200 V is also connected from the SCR to the L load. Compute the minimum width of the gate pulse required to turn on the device. Take L = 0.2 H.
  ক

  50 μsec

  খ

  100 μsec

  গ

  150 μsec

  ঘ

  200 μsec
• The two transistor model of the SCR can obtained by
  ক

  bisecting the SCR vertically

  খ

  bisecting the SCR horizontally

  গ

  bisecting the SCRs top two & bottom two layers

  ঘ

  bisecting the SCRs middle two layers
• For an SCR, the gate-cathode characteristic has a slop of 130. The gate power dissipation is 0.5 watts. Find Ig
  ক

  0.62 A

  খ

  620 mA

  গ

  62 mA

  ঘ

  6.2 mA
• average gate power dissipation for an SCR is 0.5 Watts the voltage applied to the gate is Vg = 10 V. What is the maximum value of current Ig for safe operation?
  ক

  0.25 A

  খ

  10 A

  গ

  0.05 A

  ঘ

  0.1 A
• Higher the magnitude of the gate pulse
  ক

  lesser is the time required to inject the charges

  খ

  greater is the time required to inject the charges

  গ

  greater is the value of anode current

  ঘ

  lesser is the value of anode current
• A tangent drawn from the Y-axis to the Pavg on the gate characteristics gives the value of the
  ক

  maximum value of gate-source resistance

  খ

  minimum value of gate-source resistance

  গ

  maximum value of gate-source power

  ঘ

  minimum value of gate-source power