In the circuit shown below,

the voltage across main thyristor $(T_{M})$ when it gets turned off is ____(Load current =300A)

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Solution

The main thyristor is turned off when $i_{c}$ is,
$i_{c} = I_{p} s i n ω t = I_{0}$
$ω t = s i n^{- 1} (\frac{I_{0}}{I_{p}})$
Peak value of current thorugh capacitor,
$I_{p} = V_{S} \sqrt{\frac{C}{L}} = 250 \times \sqrt{\frac{20 \times 10^{- 6}}{5 \times 10^{- 6}}} = 500 A$
$ω t = s i n^{- 1} (\frac{300}{500}) = {36.86}^{o}$
Voltage across main thyristor
$= V_{S} c o s ω t$
$= 250 \times c o s ({36.86}^{o}) = 200 V$

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In the circuit shown below, the voltage across main thyristor (TM) when it gets turned off is ____(Load current =300A)

The main thyristor is turned off when ic is, ic=Ip sin ωt=I0 ωt=sin−1(I0Ip) Peak value of current thorugh capacitor, Ip=VS√CL=250×√20×10−65×10−6=500A ωt=sin−1(300500)=36.86o Voltage across main thyristor =VScos ωt =250×cos(36.86o)=200V

In the circuit shown below,

the voltage across main thyristor $(T_{M})$ when it gets turned off is ____(Load current =300A)