# Three Phase Full-Wave AC/DC Conversion MCQ [Free PDF] – Objective Question Answer for Three Phase Full-Wave AC/DC Conversion Quiz

1. For α > 90°, 3-Φ Full wave bridge rectifier acts as a natural commutated inverter.

A. True
B. False

The output voltage of the 3-Φ Full wave bridge rectifier is 3Vml(cos(∝))÷π.

For α > 90° the output voltage becomes negative. The power flows from DC to the AC side.

2. What is the formula for output voltage for 3-Φ Full wave bridge rectifier for R-L load?

A. 3Vml(cos(∝))÷2π
B. 3Vml(cos(∝))÷π
C. 2Vml(cos(∝))÷π
D. 6Vml(cos(∝))÷π

The output voltage of the 3-Φ Full wave bridge rectifier for R-L load is 3Vml(cos(∝))÷π. The net area of the output voltage for the R-L load remains zero.

3. The output voltage of the 3-Φ Full wave bridge rectifier is six times of the 3-Φ Half-wave rectifier.

A. True
B. False

The output voltage of the 3-Φ Full wave bridge rectifier is 3Vml(cos(∝))÷π.

The output voltage of the 3-Φ Half wave rectifier is 3Vml(cos(∝))÷2π.

4. What is the formula for output voltage for 3-Φ Full wave bridge rectifier for R load for α < 60°?

A. 2Vml(cos(∝))÷π
B. 3Vml(cos(∝))÷2π
C. 3Vml(cos(∝))÷π
D. 6Vml(cos(∝))÷π

The output voltage of the 3-Φ Full wave bridge rectifier for R load is 3Vml(cos(∝))÷π for α < 60°. Conduction will only remain from 60°+α to 120°+α.

5. ____________ is the boundary for C.C.M and D.C.M mode in 3-Φ Full wave bridge rectifier for R load.

A. 60°
B. 10°
C. 80°
D. 50°

60° is the boundary for C.C.M and D.C.M mode in 3-Φ Full wave bridge rectifier for R load. Conduction will only remain from 60°+α to 120°+α.

6. What is the formula for output voltage for 3-Φ Full wave bridge rectifier for R load for α > 60°?

A. 2Vml(1+cos(∝+60°))÷π
B. 3Vml(1+cos(60°+∝))÷2π
C. 3Vml(1+cos(60°+∝))÷π
D. 6Vml(cos(∝))÷π

The output voltage of the 3-Φ Full wave bridge rectifier for R load is

3Vml(1+cos(60°+∝))÷π for α > 60°. Conduction will only remain from 60°+α to 180°.

7. Calculate the r.m.s value of thyristor current in 3-Φ Full-wave converter for the load current=4 A and α=12°.

A. 2.3 A
B. 2.5 A
C. 2.7 A
D. 2.9 A

The r.m.s value of thyristor current in a 3-Φ Full-wave converter is Io√1÷3. It is the r.m.s value of the thyristor current.

I(r.m.s) = Io√1÷3 = 2.3 A.

8. Calculate the average value of thyristor current in a 3-Φ Full-wave converter for the load current=9 A and α=26°.

A. 4 A
B. 5 A
C. 7 A
D. 3 A

The average value of thyristor current in a 3-Φ Full-wave converter is Io÷3. It is the average value of the thyristor current. I(r.m.s) = Io÷3 = 3 A.

9. Calculate the De-rating factor if the string efficiency is 16 %.

A. .84
B. .44
C. .5
D. .6

The de-rating factor is used to measure the reliability of a string. The value of the De-rating factor is 1-(string efficiency)=1-.16=.84.

10. Full form of MOSFET is ___________

A. metal oxide silicon field-effect transistor
B. metal oxide semiconductor field-effect transistor
C. Metal oxide settle field-effect transistor
D. Metal oriented silicon field-effect transistor