1.Which of the following statements are correct for cyclo converters?
1. Step-down cyclo converter c works on natural commutation
2. Step-up cc requires forced commutation
3. Load commutated cc works online commutation
4.Load commutated cc requires a generated emf in the load circuit.
2, 3,4
1,2, 4
1,2
1,2, 3
Correct answers: 1,2, 4
2.A 3-phase to single-phase conversion device employs a 6-pulse bridge cyclo converter. For an input voltage of 200 V per phase, the fundamental RMS value of output voltage is
600√3/Ï€ V
300/Ï€ V
600/Ï€ V
300√3/Ï€ V
Correct answers: 600√3/Ï€ V
3.Consider the following statements regarding cyclo converters:
1. In 1-phase to 1-phase CC, firing angle may be varied
2. In 3-phase to 1-phase CC, firing angle may be kept constant
3. In 1-phase to 1-phase CC, firing angle may be kept constant
4. In 3-phase to 1-phase CC, firing angle may be varied
5. In 3-phase to 1-phase CC, firing angle must be varied
From these, the correct statements
2,3, 5
1, 3,5
2,4, 5
2, 3 4
Correct answers: 1, 3,5
4.In three-phase cyclo converters, the reduction factor is
(input frequency/output frequency) -1
(input frequency/output frequency) -1/2
(input frequency/output frequency) 1/2
input frequency/output frequency
Correct answers: (input frequency/output frequency) -1
5.The single-phase bridge type cycloconverter uses __________ number of SCR
none of the mentioned
4
6
8
Correct answers: 8
6.How many switches are used to build a three-phase to three-phase cyclo converter?
18
24
10
14
Correct answers: 18
7. A single-phase full controlled converter with RLE load will act like a line-commutated inverter when the firing angle α
α > 90°
α > 180°
α < 90> 90°
α=90°
correct answer is; α > 90°
8. In a 1-Φ full converter, the number of SCRs conducting during overlap is
1
3
4
2
Correct answers: 4
9.Calculate the value of the Crest factor if Vpeak=789 V and Vr.m.s=489 V.
1.61
1.26
1.63
1.54
Correct answers: 1.61
10.In a B-2 type full controlled bridge converter
four SCRs conduct at a time
two SCRs conduct at a time
one SCR conducts at a time
three SCRs conduct at a time
Correct answers: two SCRs conduct at a time11.A single-phase uncontrolled-converter is a _________ quadrant converter uses
4 diodes
4 SCRs
4 SCRs and 2 diodes
4 SCRs and 2 diodes
Correct answers: 4 diodes
12. In a single-phase semi converter, if output voltage has peak and average values of 400 and 200 V respectively, the firing angle is
55.15°
73.4°
80.9°
140.3°
Correct answers: 55.15°
13.In a three-phase bridge rectifier, the maximum conduction of each thyristor is.....
90°
30°
120°
60°
Correct answers: 120°
14.In a 1-Φ full converter, for continuous conduction, each pair of SCRs conduct for angle
π + α
α
Ï€ – α
Ï€
Correct answers: π
15.In a single-phase full converter if output voltage has peak and average values of 350 V and 150V respectively, then the firing angle is
50.0°
47.7°
140.8°
130.5°
Correct answers: 47.7°
16.A single-phase fully controlled-converter is a _________ quadrant converter
one
none
two,
one & two
Correct answers: two,
17.Applications of cyclo converters include
static VAr compensation
induction heating
all of the mentioned
speed control of ac drives
Correct answers: all of the mentioned
2 Comments
Good job
ReplyDeletegood job
ReplyDeletePlease do not enter any spam link in the comment box.