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148. To avoid commutation failure a) circuit turn-off time must be greater than the thyristor turn-off time b) circuit turn-off time must be lesser than the thyristor turn-off time c) circuit turn-off time must be equal to the thyristor turn-off time d) none of the above mentioned
Answer: a Explanation: If the thyristor turn off time is more than the circuit turn off time, the circuit will be turned off and the thyristor will keep conducting, which is not at all desirable.
Answer: a
Explanation: If the thyristor turn off time is more than the circuit turn off time, the circuit
will be turned off and the thyristor will keep conducting, which is not at all desirable.
See less149. The gate characteristics of thyristor is a plot of a) V g on the X-axis & I g on the Y-axis b) I g on the X-axis & V g on the Y-axis c) V a on the X-axis & I g on the Y-axis d) I g on the X-axis & V a on the Y-axis
Answer: b Explanation: It is the gate current versus the gate voltage plot and gives the minimum and maximum values of gate parameters.
Answer: b
Explanation: It is the gate current versus the gate voltage plot and gives the minimum
and maximum values of gate parameters.
See less149. The gate characteristics of thyristor is a plot of a) V g on the X-axis & I g on the Y-axis b) I g on the X-axis & V g on the Y-axis c) V a on the X-axis & I g on the Y-axis d) I g on the X-axis & V a on the Y-axis
Answer: b Explanation: It is the gate current versus the gate voltage plot and gives the minimum and maximum values of gate parameters.
Answer: b
Explanation: It is the gate current versus the gate voltage plot and gives the minimum
and maximum values of gate parameters.
See less146. For an SCR the total turn-on time consists of i) Delay time ii) Rise time and the iii) Spread time The spread time interval depends upon a) the value of gate current b) junction temperature c) area of the cathode d) area of the anode
Answer: c Explanation: During the spread time the conduction starts spreading all over the SCR cathode cross-section structure, which depends upon the structure of the gate & cathode. Higher the cathode area more is the time required for the charges to spread all over
Answer: c
Explanation: During the spread time the conduction starts spreading all over the SCR
cathode cross-section structure, which depends upon the structure of the gate &
cathode. Higher the cathode area more is the time required for the charges to spread all
over
See less147. For effective turning off of the SCR after the anode current has reached zero value, ______________ a) chargers are injected by applying reverse anode-cathode voltage b) chargers are removed by applying reverse anode-cathode voltage c) chargers are injected by applying gate signal d) chargers are removed by applying gate signal
Answer: d Explanation: As the gate characteristics is a plot of Ig vs Vg consisting of two curves one for the maximum values & other for the minimum the area between them gives the total average gate power dissipation. (A very important parameter in designing of the triggering circuits).
Answer: d
See lessExplanation: As the gate characteristics is a plot of Ig vs Vg consisting of two curves one
for the maximum values & other for the minimum the area between them gives the total
average gate power dissipation. (A very important parameter in designing of the
triggering circuits).
150. The area under the curve of the gate characteristics of thyristor gives the a) total average gate current b) total average gate voltage c) total average gate impedance d) total average gate power dissipation
Answer: d Explanation: As the gate characteristics is a plot of Ig vs Vg consisting of two curves one for the maximum values & other for the minimum the area between them gives the total average gate power dissipation. (A very important parameter in designing of the triggering circuits).
Answer: d
Explanation: As the gate characteristics is a plot of Ig vs Vg consisting of two curves one
for the maximum values & other for the minimum the area between them gives the total
average gate power dissipation. (A very important parameter in designing of the
triggering circuits).
See less151. A tangent drawn from the Y-axis to the Pavg on the gate characteristics gives the value of the a) maximum value of gate-source resistance b) minimum value of gate-source resistance c) maximum value of gate-source power d) minimum value of gate-source power
Answer: b Explanation: It gives the min gate to source resistance.
Answer: b
Explanation: It gives the min gate to source resistance.
See less152. Higher the magnitude of the gate pulse a) lesser is the time required to inject the charges b) greater is the time required to inject the charges c) greater is the value of anode current d) lesser is the value of anode current
Answer: a Explanation: Lesser time is required to inject the charges & turn on the device with higher gate pulse magnitude.
Answer: a
Explanation: Lesser time is required to inject the charges & turn on the device with
higher gate pulse magnitude.
See less153. The 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? a) 0.25 A b) 10 A c) 0.05 A d) 0.1 A
Answer: c Explanation: Vg/Ig = 130 .. (given) Vg.Ig = 0.5 watts .. (given) use both the given data & find the gate current
Answer: c
Explanation: Vg/Ig = 130 .. (given)
Vg.Ig = 0.5 watts .. (given)
use both the given data & find the gate current
See less154. For an SCR, the gate-cathode characteristic has a slop of 130. The gate power dissipation is 0.5 watts. Find Ig a) 0.62 A b) 620 mA c) 62 mA d) 6.2 mA
Answer: c Explanation: Vg/Ig = 130 .. (given) Vg.Ig = 0.5 watts .. (given) use both the given data & find the gate current
Answer: c
Explanation: Vg/Ig = 130 .. (given)
Vg.Ig = 0.5 watts .. (given)
use both the given data & find the gate current
See less