Q.1
In a 3-phase full wave converter, if V is the maximum value of line voltage at the input, then each SCR is subjected to a peak negative voltage of
  • a) V
  • b) 3V
  • c) √3V
  • d) V/2
Q.2
In a 3-phase semi-converter, firing angle is less than 60°, as such each SCR and diode conduct respectively for __________ (in degrees)
  • a) 60, 60
  • b) 90, 30
  • c) 120, 120
  • d) 180, 180
Q.3
The effect of source inductance on the performance of a 3-phase controlled converter is to
  • a) increase the average load voltage
  • b) reduce the average load voltage
  • c) make the load current continuous
  • d) remove ripples from the load current
Q.4
Which of the following converter circuits would require a neutral point?
  • a) 3-phase semi-converter
  • b) 3-phase full converter
  • c) 3-phase full converter with freewheeling diode
  • d) 3-phase half wave converter
Q.5
The range of firing angle for a 3-phase, 3-pulse converter feeding a resistive load is __________ (in degrees).
  • a) 0 to 180
  • b) 0 to 150
  • c) 30 to 150
  • d) 30 to 180
Q.6
A 3-phase bridge converter is given a three-phase supply in the phase sequence R-Y-B. Let the neutral to R phase voltage be Vm sinωt. The first SCR (connected to R phase) is fired at an angle of 15°. What is the maximum value at the output terminals at this instant?
  • a) Vm/√2
  • b) Vm
  • c) 1.5 Vm
  • d) 3 Vm
Q.7
The PIV experienced by each SCRs in M-3 converter is __________ times that in a 3-phase full converter having the same output voltage.
  • a) 0.5
  • b) 1
  • c) 2
  • d) 1.5
Q.8
Each SCR of a 3-phase 6-pulse converter conducts for
  • a) 120 degrees
  • b) 60 degrees
  • c) 180 degrees
  • d) 360 degrees
Q.9
A 3-phase full converter has an average output voltage ofV for zero degree firing and resistive load. For a firing angle ofdegree, the output voltage would be
  • a) 125 V
  • b) 569 V
  • c) 365 V
  • d) zero
Q.10
Semi-converters are
  • a) single quadrant converters
  • b) double quadrant converters
  • c) three quadrant converters
  • d) none of the mentioned
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