Electronics and Communication Engineering - Power Electronics


A single phase half wave converter is used to charge a battery of 50 V. The thyristor is continuously fired by dc signal. Input voltage is v = Vm sin ωt. The thyristor will conduct

A. from 0 to 180°
B. when v > 50 V
C. from 0 to 90°
D. When v < 50 V

Answer: Option B


Thyristor can conduct only when it is forward biased. This occurs only when v > 50 V.


The symbol in figure is for

B. P-N junction diode
C. Schottky diode
D. None of the above

Answer: Option C


No answer description available for this question. Let us discuss.


In a 3 phase semiconverter, the firing frequency is

A. equal to line frequency
B. 3 times the line frequency
C. 6 times the line frequency
D. 12 times the line frequency

Answer: Option B


Since the circuit has 3 thyristors, firing frequency is three times the line frequency.


Present day HVDC converters are all

A. 3 pulse converters
B. 6 pulse converters
C. 12 pulse converters
D. either 6 pulse or 12 converters

Answer: Option C


To reduce ripple 12 pulse converters are used.


A single phase full converter gives maximum and minimum output voltage at firing angles of

A. 0 and 180° respectively
B. 180° and 0° respectively
C. 0 and 90° respectively
D. 90° and 0° respectively

Answer: Option A


Output voltage is maximum if a = 0 and is minimum if a = 180°.