Question 41 : In pulse width modulation scheme, _________ is kept constant.
1. Vs
2. Ton
3. T
4. Toff
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Question 42 : In a type C chopper, if only one switch is operated
1. only one quadrant operation will be obtained
2. two quadrant operation can be obtained
3. the chopper won't work
4. none of the mentioned
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Question 43 : For a type D chopper, if duty cycle α < 0.5 then the
1. average voltage is positive
2. average voltage is negative
3. average voltage is zero
4. none of the mentioned
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Question 44 : Find the expression for output voltage for a step-up chopper, assume linear variation of load current and α as the duty cycle.
1. Vs
2. Vs/α
3. Vs/(1-α)
4. Vs/√2
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Question 45 : The AC ripple voltage is given by
1. Vrms/Vo
2. Vrms²/π
3. √(Vrms² – Vo²)
4. √(Vrms + Vo)
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Question 46 : Find the expression for effective input resistance of a step down chopper. With R load and duty cycle = α.
1. R x α
2. R/2
3. 0
4. R/α
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Question 47 : A voltage commutated chopper has the following parameters:
Vs = 220 V. Commutation circuit: L = 20 μH and C = 50 μF.
Find the effective on period for a constant load current of 80 A and Ton = 800 μsecs.
1. 1.075 μs
2. 10.75 ms
3. 1075 μs
4. 1.075 sec
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Question 48 : The speed of a separately excited dc motor is controlled below base speed by using a type-A SCR based chopper. The supply voltage is 220 V dc and the armature resistance is 0.5 Ω. Calculate the minimum value of firing angle if the motor drives a constant torque load requiring an average armature current of 30 A.
1. 1/2
2. 3/44
3. 59/46
4. 7/12
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Question 49 : Which of the following mentioned control strategy/strategies would require a feedback loop?
1. pwm
2. constant frequency system
3. current limit control
4. none of the mentioned
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Question 50 : A step-down chopper is also called as a
1. first-quadrant chopper
2. second-quadrant chopper
3. third-quadrant chopper
4. fourth-quadrant chopper
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