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  • Question

  • 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

  • Correct Answer
  • (p - a) radians 

    Explanation
    The conduction is from a to p.

    Power Electronics problems

    Search Results

    • 1. 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
      • Discuss
    • 2. Between which points does UJT exhibit negative resistance characteristics

    • Options
    • A. between peak and valley points
    • B. before peak point
    • C. after peak point
    • D. after valley point
      • Discuss
    • 3. 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
      • Discuss
    • 4. 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 =
      • Discuss
    • 5. 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
      • Discuss
    • 6. An SCR has a turn on time of 4 ?s. The gate pulse should have a duration of about

    • Options
    • A. 2 ?s
    • B. 5 ?s
    • C. 20 ?s
    • D. 50 ?s
      • Discuss
    • 7. A 3 phase semiconverter when supplying a certain load has a rectification efficiency of 0.6 and transformer utilisation factor of 0.35. When a 3 phase full converter is supplying the same load

    • Options
    • A. rectification efficiency will be more than 0.6 and TUF will be more than 0.35
    • B. rectification efficiency will be more than 0.6 but TUF will be less than 0.35
    • C. rectification efficiency will be less than 0.6 and TUF will be less than 0.35
    • D. rectification efficiency will be less than 0.6 but TUF will be more than 0.35
      • Discuss
    • 8. The symbol in figure is for

    • Options
    • A. DIAC
    • B. P-N junction diode
    • C. Schottky diode
    • D. None of the above
      • Discuss
    • 9. When the core of a saturable reactor is saturated, the inductance is high.

    • Options
    • A. True
    • B. False
      • Discuss
    • 10. Assertion (A): When an SCR is conducting, the voltage drop across is about 1 V.

      Reason (R): When an SCR is conducting, the junction temperature is about 200°C.


    • Options
    • A. Both A and R are correct and R is correct explanation of A
    • B. Both A and R correct but R is not correct explanation of A
    • C. A is correct but R is wrong
    • D. A is wrong but R is correct
      • Discuss

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