1
Question
For the circuit shown below, containing SCR with a latching current of 60 mA. The duration of switching pulse required to fire the thyristor is _____ msec.
(Answer up to two decimal places).
(Answer up to two decimal places).
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Solution
When SCR is triggered,
Let current flowing in circuit be i(t)
We can write,
i(t)=VR(1−e−t/τ)
Where, τ=LR=0.2550=255000=51000
=1200=0.005sec
i(t)=5050(1−e−t/0.005)
Current should be at least latching current to keep SCR turned on
60×10−3=(1−e−t/0.005)
e−t/0.005=1−60×10−3
= 1 - 0.06
= 0.94
−t0.005=−0.061875
t=0.3094 msec≈0.31 msec
Let current flowing in circuit be i(t)
We can write,
i(t)=VR(1−e−t/τ)
Where, τ=LR=0.2550=255000=51000
=1200=0.005sec
i(t)=5050(1−e−t/0.005)
Current should be at least latching current to keep SCR turned on
60×10−3=(1−e−t/0.005)
e−t/0.005=1−60×10−3
= 1 - 0.06
= 0.94
−t0.005=−0.061875
t=0.3094 msec≈0.31 msec
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