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Electronics and Communication Engineering - Power Electronics

Exercise : Power Electronics - Section 1
11.
An SCR is triggered at 40° in the positive half cycle only. The average anode current is 50 A. If the firing angle is changed to 80°, the average anode current is likely to be
50 A
25 A
less than 50 A but more than 25 A
less than 25 A
Answer: Option
Explanation:

.

12.
The characteristics of a non-linear resistance is i = kv4. If i becomes 100 times, v becomes
about 100 times
about 10 times
about 3 times
about twice
Answer: Option
Explanation:

v ∝ (i)1/4 ∝ (100)1/4 ≈ 3.

13.
In a step down chopper using pulse width modulation, Ton = 3 x 10-3 and Toff = 1 x 10-3 s. The chopping frequency is
333.33
250
500
1000
Answer: Option
Explanation:

.

14.
Thyristors are suitable for dc circuit breakers but not for ac circuit breakers.
True
False
Answer: Option
Explanation:

They are suitable for both dc and ac circuit breakers.

15.

Assertion (A): Inverters and choppers use fast switching thyristors

Reason (R): Fast switching SCR has low turn off time.

Both A and R are correct and R is correct explanation of A
Both A and R correct but R is not correct explanation of A
A is correct but R is wrong
A is wrong but R is correct
Answer: Option
Explanation:

Low turn off time enables fast switching.

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