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Electronics and Communication Engineering - Power Electronics

Exercise : Power Electronics - Section 3
31.
In a semi converter feeding a resistive load, the firing angle is a. Each thyristor conducts for
p radians
(p - a) radians
(p + a) radians
(p - 0.5 a) radians
Answer: Option
Explanation:

The conduction is from a to p.

32.
Between which points does UJT exhibit negative resistance characteristics
between peak and valley points
before peak point
after peak point
after valley point
Answer: Option
Explanation:
No answer description is available. Let's discuss.
33.
A thyristor has maximum allowable junction temperature of 110° C and the ambient temperature is 40°C, If the maximum internal power dissipation is 50 W, the thermal resistance is
2° C/W
1.4° C/W
0.7°C/W
2.2° C/W
Answer: Option
Explanation:

.

34.
A single phase electric heater uses phase controlled thyristors. The firing angle is 90°. The degree of heating is
25% of maximum
50% of maximum
75% of maximum
none of the above
Answer: Option
Explanation:

Conduction occurs only during 50% of wave.

35.
Which of these commutation methods is used in AC-DC converters?
Class A
Class C
Class D
Class F
Answer: Option
Explanation:

Class F is natural commutation AC = DC converter use natural (or line) commutation.

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