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Electronics and Communication Engineering - Power Electronics

Exercise : Power Electronics - Section 3
16.
A thyristor has its gate current zero. To start conduction the forward voltage must exceed
about 0.5 V
forward breakover voltage
on state voltage
peak working off state forward voltage
Answer: Option
Explanation:

With zero gate current, conduction can be started only if forward voltage exceeds breakover voltage.

17.

Assertion (A): Snubber circuit has an RC series circuit in parallel with SCR

Reason (R): Voltage across a capacitor can not change instantaneously.

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:

Since voltage across capacitor cannot change instantaneously it protects SCR against high .

18.
In dielectric heating, the thyristor circuits consist of
rectifier-chopper combination
controlled rectifier
ac regulator
rectifier-inverter combination
Answer: Option
Explanation:

Input ac is rectified and then converted to high frequency ac.

19.
On load tap changer using thyristors can have a maximum of two taps.
True
False
Answer: Option
Explanation:

Any number of taps are possible.

20.

Assertion (A): A cycloconverter may be line commutated or forced commutated

Reason (R): A step up cycloconverter requires forced commutation.

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:
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