**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 Î± Î± > 90° Î± > 180° Î± < 90> 90°

Î±=90°

**correct answer is;****Î± > 90°**

**8**. In a 1-Î¦ 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

**Correct answers: two SCRs conduct at a time**

**11**.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-Î¦ full converter, for continuous conduction, each pair of SCRs conduct for angle

Ï€ + Î±
Î±
Ï€ – Î±
Ï€

**Correct answers:**

**Ï€**

**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**

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