Electronics and Communication Engineering - Power Electronics

11. 

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

Explanation:

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


12. 

The symbol in figure is for

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

Answer: Option C

Explanation:

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

13. 

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

Explanation:

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


14. 

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

Explanation:

To reduce ripple 12 pulse converters are used.


15. 

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

Explanation:

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