Rectifiers

1. On which of the following factors the number of phases for which a rectifier should be designed depend?

  1. The voltage regulation of the rec┬Čtifier should be low
  2. In the output circuit there should be no harmonics
  3. The power factor of the system should be high
  4. The rectifier supply transformer should be utilized to the best ad-vantage
  5. all of the above

Correct answer: (E)
all of the above

2. In a phase-shift control method, the phase shift between anode and grid voltages can be achieved by means of

  1. shunt motor
  2. synchronous motor
  3. induction regulator
  4. synchronous generator

Correct answer: (C)
induction regulator

3. A commutating rectifier consists of commutator driven by

  1. an induction motor
  2. a synchronous motor
  3. a D.C. series motor
  4. a D.C. shunt motor

Correct answer: (B)
a synchronous motor

4. A mercury arc rectifier possesses _________ regulation characteristics

  1. straight line
  2. curved line
  3. exponential
  4. none of the above

Correct answer: (D)
none of the above

5. A rotary converter combines the function of

  1. an induction motor and a D.C. generator
  2. a synchronous motor and a D.C. generator.
  3. a D.C. series motor and a D.C. generator
  4. none of the above

Correct answer: (B)
a synchronous motor and a D.C. generator.

6. A rotary converter in general construction and design, is more or less like

  1. a transformer
  2. an induction motor
  3. an alternator
  4. any D.C. machine

Correct answer: (D)
any D.C. machine

7. A rotary converter is a single machine with

  1. one armature and one field
  2. two armatures and one field
  3. one armature and two fields
  4. none of the above

Correct answer: (A)
one armature and one field

8. A rotary converter operates at a

  1. low power factor
  2. high power factor
  3. zero power factor
  4. none of the above

Correct answer: (B)
high power factor

9. A synchronous converter can be started

  1. by means of a small auxiliary motor
  2. from AC. side as induction motor
  3. from D.C. side as D.C. motor
  4. any of the above methods

Correct answer: (D)
any of the above methods

10. Ageing of a selenium rectifier may change the output voltage by

  1. 5 to 10 per cent
  2. 15 to 20 per cent
  3. 25 to 30 per cent
  4. none of the above

Correct answer: (A)
5 to 10 per cent

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