# AC/DC Conversion of Inductive Loads With Freewheeling Diode MCQ

1. Calculate the voltage across the freewheeling diode when the output voltage is 24 V.

A. -15 V
B. -24 V
C. 28 V
D. 39 V

The freewheeling diode is used to provide a freewheeling path. It is connected in the anti-parallel direction of the load. The voltage across the diode is -Vo=-24 V.

2. Calculate the value of the conduction angle for SCR for R-L load with a freewheeling diode if the value of β and α are 65° and 12°.

A. 168°
B. 170°
C. 130°
D. 180°

The conduction angle for SCR for R-L load with a freewheeling diode is

π-α=180°-12°=168°.

R-L load is a current stiff type of load. The current in the SCR only flows from α to π.

3. Calculate the value of the conduction angle for the diode for R-L load with a freewheeling diode if the value of α is 45°. (Continous conduction mode)

A. 220°
B. 225°
C. 230°
D. 280°

The conduction angle for the diode for R-L load with a freewheeling diode is

π+α=180°+45°=225°.

4. Calculate the value of the conduction angle for the diode for R-L load with a freewheeling diode if the value of β is 226°. (Discontinuous conduction mode)

A. 40°
B. 45°
C. 50°
D. 46°

The conduction angle for the diode for R-L load with a freewheeling diode is

β-π=226°-180°=45°.

5. Calculate the value of the conduction angle for R-L load if the value of β and α are 56° and 18°.

A. 48°
B. 38°
C. 57°
D. 15°

The conduction angle for R-L load is
β-α=56°-18°=38°.

R-L load is a current stiff type of load. The current in the circuit only flows from α to β.

6. Calculate the value of the fundamental displacement factor for 1-Φ Full wave bridge rectifier if the firing α=17°.

A. .98
B. .19
C. .56
D. .95

The fundamental displacement factor is the cosine of angle difference between the fundamental voltage and fundamental current.

D.F=cos(∝)=cos(17°)=0.95.

7. Calculate the value of the fundamental displacement factor for a 1-Φ Full-wave semi-converter if the firing angle value is 95o.

A. .60
B. .68
C. .62
D. .67

The fundamental displacement factor is the cosine of angle difference between the fundamental voltage and fundamental current. The fundamental displacement factor for 1-Φ Full-wave semi-converter is cos(∝÷2)=cos(47.5o)=.67.

8. Which one of the following loads is suitable for lagging power factor load in a Single-phase Half-bridge inverter?

B. R-L-C overdamped
C. R-L-C underdamped

R-L-C overdamped loads are generally lagging power factor loads. They require forced commutation. Anti-Parallel diodes do not help in the commutation process.

9. Which one of the following loads is suitable for the leading power factor load in a Single-phase Half-bridge inverter?

B. R-L-C overdamped
C. R-L-C underdamped

R-L-C underdamped are leading power factor loads. They do not require any forced commutation technique. Anti-Parallel diodes help in the commutation process.

10. A step-down chopper has an input voltage of .1 V and output voltage of .01 V. Calculate the value of the duty cycle.

A. 0.1
B. 0.2
C. 0.3
D. 0.5