Question 81 : The range of firing angle for a 3-phase, 3-pulse converter feeding a resistive load is __________ (in degrees).
1. 0 to 180
2. 0 to 150
3. 30 to 150
4. 30 to 180
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Question 82 : The average output voltage is maximum when SCR is triggered at ωt =
1. π
2. 0
3. π/2
4. π/4
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Question 83 : In a single phase full converter, for discontinuous load current and extinction angle β > π, each SCR conducts for
1. α
2. β
3. β-α
4. β+α
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Question 84 : In a single phase full converter with resistive load and firing angle α, the load current is
1. zero at α, π+α, …
2. remains zero for duration α
3. Vm/R sinα at α, π+α, …
4. remains zero for duration π-α
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Question 85 : A single-phase half wave rectifier with a FD is supplied by Vs = 240 V, AC with a load R = 10 Ω, L = 0.5 mH and a firing angle α = 30°. Find the average value of the load voltage.
1. 50 V
2. 100 V
3. 150 V
4. 200 V
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Question 86 : In a 3 phase, 12-pulse controlled converter for continuous conduction mode, each SCR conducts for __________ per cycle.
1. π/6 radians
2. 60 degrees
3. 3π/2 radians
4. 12 degrees
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Question 87 : For a single phase half-wave thyristor circuit with R load, the input power factor is given by
1. rms source voltage/total rms line current
2. rms input power/power delivered to the load
3. cos α
4. power delivered to load/input VA
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Question 88 : In non-circulating current mode dual converters, the circulating current is avoided by
1. connecting a series reactor
2. maintaining α1 + α2 = 180°
3. operating only one converter
4. adding an extra SCR
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Question 89 : Which of the following converter circuits would require a neutral point?
1. 3-phase semi-converter
2. 3-phase full converter
3. 3-phase full converter with freewheeling diode
4. 3-phase half wave converter
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Question 90 : A fully controlled converter uses
1. diodes only
2. thyristors only
3. both diodes and thyristors
4. none of the mentioned
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