61. Calculate the Vo(avg) for the 3-Φ phase Half-wave uncontrolled rectifier if the supply value is 440 V.
A. 297.25 V
B. 298.15 V
C. 298.11 V
D. 300.15 V
Answer: A
The Vo(avg) for the 3-Φ phase Half-wave uncontrolled rectifier is 3Vml÷2π. The value of output voltage is
3Vml÷2π
= 3×√2×440÷6.28 = 297.25 V.
62. Calculate the pulse number if the supply frequency is 2π and the output frequency is 2π÷3.
A. 4
B. 5
C. 6
D. 3
Answer: D
The pulse number can be calculated using the ratio of input frequency to output frequency. The value of pulse number (P) is 2π÷(2π÷3) = 3. It is a three-pulse converter or 3-Φ phase Half-wave uncontrolled rectifier.
63. Calculate the average value of current for the 3-Φ phase Half-wave uncontrolled rectifier if the supply value is 400 V and the resistive load value is 5 Ω.
A. 54.04 A
B. 57.26 A
C. 51.64 A
D. 58.15 A
Answer: A
The Io(avg) for the 3-Φ phase Half-wave uncontrolled rectifier is
3Vml÷2πR.
The value of output voltage is
3Vml÷2πR
= 3×√2×440÷6.28×5 = 54.04 A.
64. In a 3-Φ Fully controlled rectifier calculate the average value of the voltage if the supply is 400 V and the firing angle is 45°.
A. 381.15 V
B. 382.16 V
C. 383.19 V
D. 384.25 V
Answer: B
In 3-Φ Fully controlled rectifier, the average value of the voltage is
3Vml(cos(∝))÷π
= 3×400×√2(cos(45°))÷3.14 = 382.16 V.
65. Calculate the Vo(r.m.s) (Highly inductive load. for the 3-Φ phase Half-wave uncontrolled rectifier if the supply value is 441 V.
A. 297.25 V
B. 298.15 V
C. 298.11 V
D. 300.15 V
Answer: A
The Vo(r.m.s) for the 3-Φ phase Half-wave uncontrolled rectifier is 3Vml÷2π. The value of output voltage is
3Vml÷2π
= 3×√2×441÷6.28 = 297.25 V.
66. Calculate the Vo(avg) for the 3-Φ phase Half-wave controlled rectifier if the supply value is 364 V and the value of firing angle is 2°.
A. 247.62 V
B. 245.76 V
C. 214.26 V
D. 233.26 V
Answer: B
The Vo(avg) for the 3-Φ phase Half-wave controlled rectifier is 3Vmlcos(α)÷2π.
The value of output voltage is 3Vmlcos(α)÷2π
= 3×√2×364×(.99)÷6.28 = 245.76 V.
67. Calculate the value of the Input power factor for a 3-Φ Fully controlled rectifier if the firing angle value is 16°.
A. .96
B. .91
C. .93
D. .94
Answer: B
The value of the input power factor for a 3-Φ Fully controlled rectifier is .95cos(16°) = .91. The input power factor is a product of the distortion factor and displacement factor.
68. In a 3-Φ semi-controlled rectifier calculate the average value of the voltage if the supply is 299 V and the firing angle is 56.15°.
A. 311.26 V
B. 304.26 V
C. 314.51 V
D. 312.45 V
Answer: C
In 3-Φ Semi-controlled rectifier, the average value of the voltage is
3Vml(1+cos(∝))÷2π
= 3×299×√2(1+cos(56.15°))÷6.28 = 314.51 V.
69. Calculate the circuit turn-off time for 3-Φ Fully controlled rectifier if the firing angle is 13° and the supply frequency is 49.5 Hz.
A. 730.2 msec
B. 740.8 msec
C. 754.5 msec
D. 755.1 msec
Answer: A
The circuit turn-off time for 3-Φ Fully controlled rectifier is (240°-α)÷ω. The value of circuit turn-off time for ∝ < 60° is
(240°-13°)÷6.28×49.5 = 730.2 msec.
70. Calculate the circuit turn-off time for 3-Φ Fully controlled rectifier if the firing angle is 170° and the supply frequency is 50.5 Hz.
A. 32.4 msec
B. 35.2 msec
C. 39.3 msec
D. 31.5 msec
Answer: D
The circuit turn-off time for 3-Φ Fully controlled rectifier is (180°-α)÷Ω. The value of circuit turn-off time for ∝ ≥ 60° is
