Cycloconverter MCQ

1. Cycloconverter converts

  1. fixed DC to variable voltage and variable frequency AC
  2. fixed DC to variable DC
  3. fixed AC to variable DC
  4. Fixed AC to variable frequency AC
Answer. d

2. In a single-phase to 1-phase cyclo-converter, the magnitudes of harmonic components are quite large. How can they be reduced?

  1. By using a chopper circuit
  2. By using a RC oscillator
  3. By using a three-phase input supply
  4. By adding an alternator to the input
Answer. c

3. An advantage of a cycloconverter is

  1. very good power factor
  2. requires few number of thyristors
  3. commutation failure does not short circuit the source
  4. load commutation is possible
Answer. d

4. A cycloconverter-fed induction motor drive is most suitable for which one of the following?

  1. Compressor drive
  2. Machine tool drive
  3. Paper mill drive
  4. Cement mill drive
Answer. b

5. An inter-group reactor is used in a single-phase cycloconverter circuit to

  1. Reduce current-ripples
  2. Reduce voltage-ripples
  3. Limit circulating current
  4. Limit di/dt in the semiconductor switch
Answer. c

6. A 3-phase cycloconverter is used to obtain a variable-frequency single-phase a.c. output. The single-phase a.c. load is 220 V, 60 A at a power factor of 0.6 lagging. The RMS value of input voltage per phase required is

  1. 311.12V
  2. 376.2V
  3. 220 V
  4. 266 V
Answer. d

7. How many switches are used to construct a three-phase cycloconverter?

  1. 6
  2. 3
  3. 18
  4. 12
Answer. c

8. A cycloconverter is operating on a 50Hz supply. The range of output frequency that can be obtained with acceptable quality, is

  1. 0-32 Hz
  2. 0-16 Hz
  3. 0-128 Hz
  4. 0-64 Hz
Answer. c

9. The quality of output ac voltage of a cycloconverter is improved with

  1. increase in output voltage at reduced frequency
  2. increase in output voltage at increased frequency
  3. decrease in output voltage at reduced frequency
  4. decrease in output voltage at increased frequency
Answer. a