Power Electronics (3140915) MCQs

MCQs of AC-DC Converters

Showing 11 to 20 out of 107 Questions
11.
In case of a single-phase half-wave circuit with RL load, with firing angle α and extinction angle β, the conduction angle γ can be written as
(a) γ = β+α
(b) γ = β-α
(c) γ = β/α
(d) γ = α/β
Answer:

Option (b)

12.
Choose the correct statement with respect to 1-Φ half wave controlled rectifier having R-L load with freewheeling diode circuit.
(a) The load current can be negative
(b) The load voltage can never be negative
(c) The load voltage can never be zero
(d) The load voltage can never be positive
Answer:

Option (b)

13.
In 1-Φ half wave controlled rectifier having R-L load with freewheeling diode circuit; when, the commutating diode or FD is conducting than the power-electronics-questions-answers-freshers-q1
(a) SCR has reverse bias voltage and the load current is zero
(b) SCR has reverse bias voltage and the load current is positive
(c) SCR has forward bias voltage and the load current is zero
(d) SCR has forward bias voltage and the load current is positive
Answer:

Option (b)

14.
In a single-phase half-wave circuit with RL load and a freewheeling diode, the load voltage during the freewheeling period will be
(a) zero
(b) positive
(c) negative
(d) positive than negative
Answer:

Option (a)

15.
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.
(a) 50 V
(b) 100 V
(c) 150 V
(d) 200 V
Answer:

Option (b)

16.
A single-phase HW rectifier with a FD is supplied by Vs = 240 V, 50 Hz, AC with a load R = 10 Ω, L = 0.5 mH and a firing angle α = 30°. Find the average value of the load current.
(a) 10 A
(b) 0.063 A
(c) 6.3 A
(d) 0.1 A
Answer:

Option (a)

17.
A single phase half-wave controlled rectifier has 400 sin314t as the input voltage and R as the load. For a firing angle of 60°,the average output voltage is
(a) 200/π
(b) 300/π
(c) 100/π
(d) 400/π
Answer:

Option (b)

18.
A single-phase half-wave rectifier with a FD is supplied by Vs = 240 V, 50 Hz, AC source with a load R = 10 Ω, L = 0.8 mH. The firing angle is so adjusted such that the output voltage obtained is 100 V. Find the firing angle.
(a) 62°
(b) 102°
(c) 31°
(d) 47°
Answer:

Option (c)

19.
By using a freewheeling diode (FD) in a rectifier with RL load, the power consumed by the load
(a) increases
(b) decreases
(c) is not affected
(d) decreases to zero
Answer:

Option (a)

20.
A 230 V, 50 Hz, one-pulse SCR controlled converter has extinction angle β = 210°. Find the circuit turn-off time
(a) 10 m-sec
(b) 0
(c) 8.3 m-sec
(d) 5.4 m-sec
Answer:

Option (c)

Showing 11 to 20 out of 107 Questions