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Electronics and Communication Engineering - Power Electronics

Exercise : Power Electronics - Section 3
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
from 0 to 180°
when v > 50 V
from 0 to 90°
When v < 50 V
Answer: Option
Explanation:

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

12.
The symbol in figure is for
DIAC
P-N junction diode
Schottky diode
None of the above
Answer: Option
Explanation:
No answer description is available. Let's discuss.
13.
In a 3 phase semiconverter, the firing frequency is
equal to line frequency
3 times the line frequency
6 times the line frequency
12 times the line frequency
Answer: Option
Explanation:

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

14.
Present day HVDC converters are all
3 pulse converters
6 pulse converters
12 pulse converters
either 6 pulse or 12 converters
Answer: Option
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
0 and 180° respectively
180° and 0° respectively
0 and 90° respectively
90° and 0° respectively
Answer: Option
Explanation:

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

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