Bissoy.com
Doctors Medicines MCQs Q&A

In the circuit shown in the given figure, the SCR is fired at 45°. Which of the following statements is correct with respect to load voltage and current at ωt = π?

In the circuit shown in the given figure, the SCR is fired at 45°. Which of the following statements is correct with respect to load voltage and current at ωt = π? Correct Answer Only load voltage is zero

Single-phase half-wave rectifier with R-L load: 

[ alt="F2 U.B Madhu 27.04.20 D1" src="//storage.googleapis.com/tb-img/production/20/04/F2_U.B_Madhu_27.04.20_D1.png" style="width: 261px; height: 216px;">

  • At ωt = α, the thyristor is turned on by a gating signal. The load voltage vo at once becomes equal to source voltage vs as shown. But the inductance L forces the load, or output, current io to rise gradually. After some time, i0 reaches a maximum value and then begins to decrease.
  • At ωt = π, vo is zero but io is not zero because of the load inductance L.
  • After ωt = π, SCR is subjected to reverse anode voltage, but it will not be turned off as load current io is not less than the holding current.
  • At some angle β > π, io reduces to zero and SCR turned off as it is already reverse biased.
  • After ωt = β, vo = 0 and io = 0 i.e. both the output voltage and current become zero.

 

The waveforms of load current and load voltage are shown below.

[ alt="F2 U.B Madhu 27.04.20 D2" src="//storage.googleapis.com/tb-img/production/20/04/F2_U.B_Madhu_27.04.20_D2.png" style="width: 361px; height: 373px;">

Related Questions

Consider the following statements: 1. In a silicon controlled rectifier (SCR), if the cathode gate is reverse-biased, then the SCR cannot fire at all. 2. The turn-on time of an SCR increases with temperature. 3. After an SCR is turned on, it can be made to turn off again by reverse biasing the gate. 4. Gate recovery time is the minimum time that the anode voltage must be maintained below holding voltage VH to turn off the SCR. Which of these statements are correct?
A 220 1-ϕ, 220 Ω  resistor is connected in series with the gate of an SCR as shown in the given figure. The gate current required to fire the SCR is 7 mA. what is the input voltage (Vin) required to fire the SCR?
Which of the following statements are correct for an ideal constant voltage source? 1. Its output voltage remains absolutely constant whatever the change in load current. 2. It possesses zero internal resistance so that internal voltage drop in the source is zero. 3. Output voltage is provided by the source would remain constant irrespective of the amount of current drawn from it. 4. Output voltage provided by the source varies with the amount of current drawn from it.
Consider the following statements regarding reciprocity theorem : 1. In any passive linear bilateral network, if the single voltage source Vx, in branch x produces the current response Iy, in branch y, then the removal of the voltage source from branch x and its insertion in branch y will produce the current response iy in branch x. 2. The interchange of an ideal voltage source and an ideal ammeter in any passive, linear, bilateral circuit will not change the ammeter reading. 3. The interchange of an ideal current source and an ideal voltmeter in any passive linear bilateral circuit will change the voltmeter reading. Which of the above statements are correct ?
For a Zener diode shunt regulator, the source current is IS, the Zener diode current is IZ and the load current is IL. The source voltage is VS, Zener voltage is VZ and load voltage is VL. The load resistance is RL. What is the correct option for the safe operation of the diode?
Consider the following statements: SCR can be turned on by 1. Applying anode voltage at a sufficiently fast rate 2. Applying sufficiently large anode voltage 3. decreasing the temperature of SCR 4. Applying sufficiently large gate current Which of the above statements are correct?
A voltage source Vs = Vm sinωt is connected in series with a resistance R and an SCR. At some firing angle delay of α a positive gate pulse is applied to the SCR which turns on the SCR. Considering ideal conditions, at the instant α the voltage at the resistor terminals Vo
Consider the following statement: 1. Initial load tests and routine load tests are carried out on test piles and working Piles, respectively. 2. In a pile load test, the allowable load can be taken equal to half the ultimate load at which the total settlement amounts to one-tenth of the pile diameter. 3. In a pile load test, the allowable load can be taken equal to two-thirds of the total toad which causes a plastic settlement of 6 mm. Which of the above statements are correct?
For the V-I characteristics if an SCR, which of the following statements are correct? 1. It will trigger when the applied voltage is more than the forward breakover voltage 2. Holding current is greater than the latching current 3. When reverse biased, a small of leakage current will flow. 4. It can be triggered without gate current
In the above figure, the load voltage is positive whereas the load current is negative. Thus, the current flows out of the load and into the source. Identify the type of chopper shown in the figure.