Question 31 : The expression for the thyristor (chopper switch) current is given by
I = (α².Vs - αE)/R
Find the value of firing angle α, for which the thyristor current is maximum.
1. 2Vs/π
2. 180°
3. E/2Vs
4. Vs/R
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Question 32 : The control strategy in which on and off time is guided by the pervious set of values of a certain parameter is called as
1. time ratio control
2. pulse width modulation
3. current limit control
4. constant frequency scheme
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Question 33 : For a type D chopper, if duty cycle = 0.5 then the
1. average voltage is positive
2. average voltage is negative
3. average voltage is zero
4. chopper cannot be operated with duty cycle = 0.5
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Question 34 : A chopper circuit is fed from an input voltage of 20 V delivers a power of 16 watts. If the chopper efficiency is 80 %, then find the value of input current.
1. 0.64 A
2. 1 A
3. 0.8 A
4. 1.25 A
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Question 35 : Find the expression for average output voltage in a type D chopper on RL load.
1. Vs x Duty cycle (α)
2. Vs x T
3. Vs x (T – T)/T
4. Vs²/2
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Question 36 : What is the expression for design of commutation capacitance in case of a load commutated chopper circuit?
1. (I x Ton)/Vs
2. Cannot be determined
3. (I x Ton)/2Vs
4. (I x T)/Vs
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Question 37 : In a type E chopper, if all the four chopper switches are closed simultaneously then
1. load is short circuited
2. supply is short circuited
3. both load and supply are shorted
4. none of the mentioned.
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Question 38 : For a step-up/step-down chopper, if the duty cycle > 0.5 then
1. Vo = Vs
2. Vo < Vs
3. Vo > Vs
4. None of the mentioned
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Question 39 : In a step down chopper, if Vs = 100 V and the chopper is operated at a duty cycle of 75 %. Find the output voltage.
1. 100 V
2. 75 V
3. 25 V
4. none of the mentioned
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Question 40 : The type-C chopper or two quadrant type-A chopper has
1. type-A and type-B choppers in series
2. type-A and type-B choppers in parallel
3. two type-A choppers in series
4. two type-A choppers in parallel
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