In a single phase full wave ac regulator, the firing angles in the two half cycl

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Question
In a single phase full wave ac regulator, the firing angles in the two half cycles
Options
A. are always equal
B. are sometimes equal
C. are never equal
D. may be equal or unequal

Correct Answer

are always equal

Power Electronics problems

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1. In an SCR, the anode current consists of
Options
A. only holes
B. only electrons
C. both electrons and holes
D. either electrons or holes

4. In the below figure the rms voltage across each half of secondary is 200 V. The peak inverse voltage across each of thyristor is
Options
A. 200 V
B. 2(200) V
C. 2(400) V
D. 800 V

5. A thyristor has its gate current zero. To start conduction the forward voltage must exceed
Options
A. about 0.5 V
B. forward breakover voltage
C. on state voltage
D. peak working off state forward voltage

6. In a single phase dual converter, a₁, and a₂ are firing angles of the two converters. Then
Options
A. a₁ - a₂ =
B. a₁ + a₂ = p
C. a₁ - a₂ = p
D. a₁ + a₂ =

7. A dc chopper V = 500 V feeds an electric fraction dc series motor. The chopping frequency is 400 Hz. The series inductance required to limit the maximum current swing to 10 A is
Options
A. 20 mH
B. about 31 mH
C. about 51 mH
D. about 92 mH

9. The gate current required to turn on an SCR is
Options
A. few amperes
B. a few mA
C. almost equal to anode current
D. about 50% of anode current

10. In a semi converter feeding a resistive load, the firing angle is a. Each thyristor conducts for
Options
A. p radians
B. (p - a) radians
C. (p + a) radians
D. (p - 0.5 a) radians

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